WO2019177249A1

WO2019177249A1 - Method of controlling water purifier

Info

Publication number: WO2019177249A1
Application number: PCT/KR2019/000367
Authority: WO
Inventors: Kwangyong AN; Jongwoo Park; Sangjoon Lee
Original assignee: Lg Electronics Inc.
Priority date: 2018-03-13
Filing date: 2019-01-10
Publication date: 2019-09-19
Also published as: KR20190107873A; KR102638325B1

Abstract

Disclosed herein is a method of controlling a water purifier, which is capable of efficiently dispersing heat exchange energy of coolant to improve cold water discharge performance, by changing the rotation speed of an agitator through control of a duty ratio of a voltage input to an agitating motor in correspondence with change in temperature of coolant in a cold water discharge process.

Description

METHOD OF CONTROLLING WATER PURIFIER

The present invention relates to a method of controlling a water purifier.

A water purifier is a device for filtering out harmful elements such as foreign materials or heavy metals contained in water using physical and/or chemical methods.

The prior art described below discloses a so-called direct type water purifier.

The direct type water purifier means a water purifier for coolant supplied through a water tap to a set temperature through a cooling unit and directly supplying water to a consumer without using a water tank, when the consumer pressing a water supply button.

Since the direct type water purifier does not require the water tank, there is no problem that foreign materials are accumulated on the bottom of the water tank and that bacteria propagate in the water tank.

The direct type water purifier includes a coolant tank in which coolant is stored, a cold water pipe and an evaporator disposed in the coolant tank, and a partitioning plate disposed in the coolant tank to partition the internal space of the coolant tank into a space, in which the cold water pipe is received, and a space, in which the evaporator is received, as disclosed in the prior art.

In addition, coolant at an upper side and cooled by the evaporator flows downwardly toward the cold water pipe by rotation of an agitator and cold water in the space, in which the cold water pipe is received, flows upwardly toward the evaporator.

In addition, when a lump of ice is generated on the surface of the evaporator to accumulate cold air, since heat exchange is performed by latent heat as well as sensible heat, it is possible to cool drinking water passing through the cold water pipe in a short time, which is advantageous for the direct type water purifier.

The direct type water purifier having such a structure and a method of controlling the same are disclosed in the prior art described below.

The prior art discloses a control method of operating an agitator in order of single driving of the agitator, simultaneous driving of the agitator and a compressor, single driving of the agitator and stopping of the agitator to circulate and mix coolant in the vicinity of the evaporator and coolant in the vicinity of the cold water pipe, when the temperature of the coolant increases an upper limit temperature.

According to the control method disclosed in the prior art, since the agitator constantly rotates with a set number of rotations when the temperature of the coolant reaches the upper limit temperature, heat exchange efficiency between the coolant and drinking water flowing along the cold water pipe is improved, thereby rapidly decreasing the temperature of discharged cold water.

However, the control method according to the prior art includes the following problems.

First, since the agitator rotates at a constant maximum speed from beginning to end, the temperature of discharged drinking water decreases and the temperature rising speed of the coolant increases. When the temperature rising speed of the coolant increases, there is a disadvantage in continuous discharge of cold water. In other words, since cold air loss of the coolant is large at in initial discharge of cold water, heat exchange between the coolant and the cold water pipe rapidly decreases as the discharge amount of cold water increases. As a result, the amount of drinking water (the number of glasses of drinking water) discharged at a temperature equal to or less than a defined cold water temperature rapidly decreases.

Second, since the agitator rotates at a maximum speed in initial discharge of cold water, the temperature of initially discharged water is decreased more than necessary and thus the gums of a specific user, that is, a user having tender gums, may ache.

Third, in the prior art, since the agitator rotates at a constant speed from the beginning to the end of cold water discharge, the amount of power necessary to drive the agitator is increased. In addition, since the amount of exchanged heat is increased, the cycle load of the evaporator is increased.

Prior Art Document

Patent Document

Korean Unexamined Patent Publication No. 2012-0140417 (December 31, 2012)

An object of the present invention is to solve the above-described problems.

To achieve the above objects, there is provided a method of controlling a water purifier, which is capable of efficiently dispersing heat exchange energy of coolant to improve cold water discharge performance, by changing the rotation speed of an agitator through control of a duty ratio of a voltage input to an agitating motor in correspondence with change in temperature of coolant in a cold water discharge process.

The method of controlling the water purifier according to the embodiment of the present invention including the above configuration has the following effects.

First, since the rotation speed of the agitator is changed according to the temperature of the coolant through control of the duty ratio of the voltage supplied to the agitator, it is possible to reduce the amount of power required to drive the agitator.

Second, since the temperature of the coolant is sensed to control the duty ratio of the agitator when cold water is discharged, it is possible to improve cold water discharge performance. In other words, the amount of heat exchanged between the coolant and the cold water pipe is decreased through control of the duty ratio of the agitator, such that the temperature of discharged cold water is not unnecessarily decreased to a very low temperature. As a result, the initial temperature of discharged cold water is slightly increased as compared to the prior art, but cold water is discharged at a temperature equal to or less than a defined cold water temperature. Therefore, the user recognizes discharged water as cold water.

In addition, since the amount of heat exchanged between the coolant and the drinking water at the initial discharge of cold water is small as compared to the prior art, a time required to exchange heat between the coolant and the drinking water is increased. As a result, since the amount of cold water discharged when cold water is continuously discharged is increased, it is possible to improve cold water discharge performance.

Third, when the rotation speed of the agitator is decreased through control of the duty ratio of the agitator, it is possible to reduce the cycle load of the evaporator. That is, when the rotation speed of the agitator is decreased, the amount of heat exchanged between the coolant or ice or between the coolant or the evaporator is decreased. Therefore, since the driving stop period (idle period) of the compressor is increased, it is possible to reduce the refrigerating cycle load.

FIG. 1 is an exploded perspective view of a cold water generation unit configuring a water purifier, to which a control method according to an embodiment of the present invention is applied.

FIG. 2 is a perspective view of the cold water generation unit when an insulation case is removed.

FIG. 3 is a vertical sectional view taken along line 3-3 of FIG. 3.

FIG. 4 is a flowchart illustrating a method of controlling a water purifier according to an embodiment of the present invention.

FIG. 5 is a graph comparing cold water discharge performance of the water purifier, to which the control method of the embodiment of the present invention is applied, and a cold water discharge performance of a conventional water purifier, in terms of the number of glasses of discharged cold water.

Hereinafter, a method of controlling a water purifier according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view of a cold water generation unit configuring a water purifier, to which a control method according to an embodiment of the present invention is applied, FIG. 2 is a perspective view of the cold water generation unit when an insulation case is removed, and FIG. 3 is a vertical sectional view taken along line 3-3 of FIG. 3.

Referring to FIGS. 1 to 3, the cold water generation unit 30 according to the embodiment of the present invention may include a coolant tank 33 filled with coolant, an insulation case 31 surrounding the coolant tank 33 to prevent heat exchange between the coolant and indoor air, a drain valve 32 passing through the insulation case 31 to communicate with the internal space of the coolant tank 33, a cold water pipe 34 accommodated in the coolant tank 33, a partitioner 36 accommodated in the coolant tank 33 in a state of being placed on the cold water pipe 34, an evaporator 35 placed on the partitioner 36, a tank cover 37 covering the upper end of the coolant tank 33, an agitating motor 38 fixed to the inner side of the tank cover 37 and having a rotation shaft extending downwardly, an agitator 39 accommodated in the coolant tank 33 and connected to the rotation shaft of the agitating motor 38, and a case cover 40 covering the opened upper surface of the insulation case 31.

Specifically, the drain valve 32 is installed to pass through the insulation case 31 and the coolant tank 33, and is inserted through the side surface of the insulation case 31 corresponding to a position adjacent to the bottom of the coolant tank 33. When the drain valve 32 is opened, the coolant stored in the coolant tank 33 is discharged from the water purifier 10.

In addition, the insulation case 31 is made of an insulation member such as Styrofoam and the insulation case 31 may be seated on a tank support part 21.

In addition, the cold water pipe 34 is wound in a spiral shape as shown in the figure to have a cylindrical shape, and pipes vertically adjacent to each other may be in contact with each other or spaced apart from each other. The inlet end 341 and outlet end 342 of the cold water pipe 34 may vertically extend toward the case cover 40. The inlet end 341 of the cold water pipe 34 may be connected to a water pipe connected to a water supply source and the outlet end 342 may be connected to a water pipe connected to the water outlet port of the water purifier.

In addition, the partitioner 35 is placed on the cold water pipe 34 to partition the internal space of the coolant tank 33 into a first space, in which the evaporator 35 is received, and a second space, in which the cold water pipe 34 is received. Accordingly, ice formed in the vicinity of the evaporator 35 cannot move into the second space.

In addition, the evaporator 35 is wound in a spiral shape and is seated on the outer circumferential surface of the partitioner 36. The evaporator 35 is connected to the outlet end of an expansion valve connected to the outlet end of a condenser 19. Refrigerant flowing along a refrigerant pipe forming the evaporator 35 exchanges heat with the coolant stored in the coolant tank 33, thereby cooling the coolant. The coolant exchanges heat with the drinking water flowing along the cold water pipe 34, thereby cooling the drinking water to a set temperature.

The coolant may be frozen on the surface of the evaporator 35, thereby generating a lump of ice having a predetermined size. That is, cold refrigerant in the evaporator freezes the coolant through heat absroption, such that the lump of ice accumulates latent heat of melting. That is, even in a state where the compressor 18 is not driven, coolant in an ice state and coolant in a liquid state exchange heat with each other by agitating operation of the agitator 39, such that the coolant in the liquid state is maintained at a reference temperature or less.

The water purifier according to the embodiment of the present invention may be defined as an ice thermal storage type water purifier, because some of coolant is present in an ice state on the surface of the evaporator to store latent heat. Since the ice thermal storage type water purifier may use latent heat as well as sensible heat for heat exchange, cold water discharge performance is significantly better than a non-ice thermal storage type water purifier using only sensible heat.

In addition, the tank cover 37 is provided on the upper end of the coolant tank 33, thereby covering the upper surface of the first space. That is, the first space may be defined between the tank cover 37 and the partitioner 36 and the second space may be defined between the partitioner 36 and the bottom of the coolant tank 33. A coolant inlet port 371 may be formed in one side of the tank cover 37. The coolant inlet port 371 may be connected to a water pipe connected to the water supply source to supply coolant to the coolant tank 33.

In addition, the agitator 39 may be substantially located at an intermediate point of the second space, without being limited thereto. When the agitator 39 rotates, the coolant of the second space flows into the first space to exchange heat with the evaporator 35 or the ice generated on the surface of the evaporator 35, and the coolant of the first space flows into the second space, such that the temperature of the coolant is uniformly maintained at every point of the coolant tank 33. The coolant cooled through heat exchange exchanges heat with drinking water flowing along the cold water pipe 34, thereby cooling the drinking water to a defined cold water temperature or less. Here, the defined cold water temperature may be in a range of 7°C to 8°C, without being limited thereto.

The agitator 39 may be formed in a blade or impeller shape extending from the rotation shaft in a radial direction as shown in the figure, but is not limited thereto and may be formed in various shapes.

Meanwhile, the case cover 40 is fitted on the outer circumferential surface of the upper end of the insulation case 31 to cover the opened upper surface of the coolant tank 33 and the insulation case 31. A port accommodation hole 401, through which the coolant inlet port 371 passes to be exposed to the outside, may be formed in the case cover 40. A cold water pipe guide groove 402, through which the inlet end 341 and the outlet end 342 of the cold water pipe 34 pass, may be formed in the edge of one side of the case cover 40. An evaporation pipe guide hole 403, through which the pipe of the evaporator 35 passes, may be formed in the edge of the other side of the case cover 40.

In addition, a temperature sensor (not shown) for sensing the temperature of the coolant may be installed in the coolant tank 33 on one side thereof, and the temperature sensor may include a thermistor. The temperature sensor may be placed in the first space close to the evaporator or may be placed in the second space close to the cold water pipe 34.

For example, the temperature sensor may be placed at a position relatively closer to the evaporator 35 to sense not only the temperature of the coolant but also the temperature of ice which is generated on the surface of the evaporator 35 and is in contact with the temperature sensor.

Referring to FIG. 4, the control method according to the embodiment of the present invention is applied when water is discharged.

Specifically, when a water discharge command is not received, the compressor and the agitator are driven according to the temperature of the coolant sensed by the temperature sensor. In addition, the agitator constantly rotates at a set speed until the temperature of the coolant is decreased to a lower limit temperature.

Meanwhile, while the water discharge command is received and thus water is discharged, the control method of the present invention is applied to change the rotation speed of the agitator.

First, when a user presses a water discharge button to input a water discharge command to a controller (S11), a water supply valve is opened, and drinking water in the cold water pipe 34 is discharged through the outlet port.

The temperature sensor senses the temperature CT of the coolant and transmits the sensed temperature to the controller of the water purifier (S12). The controller determines whether the temperature CT of the coolant exceeds an upper limit temperature T1 (S13), and drives the agitator 39 with a duty ratio of 100% (S14) upon determining the temperature of the coolant exceeds the upper limit temperature (S13). That is, a voltage is continuously supplied to the agitator 39 to rotate the agitator 39 at a maximum set speed. Since the agitator rotates by the agitating motor, control of the duty ratio of the agitator described in this specification may be understood as control of the duty ratio of the agitating motor 38.

In contrast, upon determining that the temperature of the coolant is between the upper limit temperature and the lower limit temperature T2 (S15), the agitator is driven with the duty ratio of A% (S16). Here, A may be a value less than 100.

In addition, upon determining that the temperature of the coolant is equal to or less than the lower limit value, the agitator is driven with the duty ratio of B% (S17). Here, B may be a value less than A.

While the agitator 39 is driven with the set duty ratio, the controller determines whether a water discharge stop command is received (S18). The water discharge stop command may be received through a separate button and the controller may sense a switch off signal generated upon releasing the pressed state of a discharge lever.

When the water discharge stop command is not received, the temperature of the coolant is continuously sensed and the agitator is driven with the duty ratio corresponding to the sensed temperature. Here, the duty ratio means a ratio of a time when a voltage is applied to the agitator 39, that is, a voltage on time, during one period. For example, a duty ratio of 100% means that the voltage is turned on for one period, a duty ratio of 50% means that the voltage is turned on for half a period and is turned off for the other half period.

As the duty ratio decreases, the voltage on time decreases and thus the amount of power supplied to the agitator decreases. Therefore, when the duty ratio decreases, the rotation speed (RPM) of the agitator decreases. When the rotation speed of the agitator decreases, heat exchange between the coolant and the ice and heat exchange between the coolant and the cold water pipe decrease and thus the temperature of discharged cold water is higher than that of cold water discharged when the agitator rotates with the duty ratio of 100%.

Meanwhile, when the water discharge stop command is received while the agitator 39 rotates with the set duty ratio, the agitator 30 further rotates during a set time with the duty ratio at the moment when the water discharge stop command is received and then stops (S19 and S20). When agitator stops, control of the present invention is finished.

Rotation or driving of the agitator has the same meaning as rotation or driving of the agitating motor.

The upper limit temperature T1 of the coolant may be 4°C to 5°C and the lower limit temperature T2 of the coolant may be 2°C to 2.5°C.

In addition, the duty ratio A may be 80 to 85 and the duty ratio B may be 70 to 75.

In addition, the number of sections in which the duty ratio is differently set according to the temperature of the coolant may be three as described above, and the range between the upper limit temperature and the lower limit temperature may be subdivided into a plurality of sections.

In addition, a high-frequency duty ratio control method and a low-frequency duty ratio control method are possible as the method of controlling the duty ratio of the agitating motor 38.

Specifically, if a voltage having the same level is supplied and an input voltage has a high frequency, since the duty cycle before input is short, the voltage of the output side of the switching element varies according to the duty ratio by the L and C components of the motor. Specifically, as the duty ratio of the voltage of the agitating motor decreases, the output voltage decreases. Since the duty cycle is short, rotation of the agitating motor is maintained even at the moment when the input voltage is turned off, and the rotation speed of the agitating motor is decreased as control of the duty ratio is performed.

However, if a voltage having the same level is supplied and an input voltage has a low frequency, since the number of times of operating the switching element is less than that of the high frequency voltage, the voltage of the output side of the switching element is not changed even when the duty ratio is changed. However, in a section in which the input voltage is turned off, rotation of the agitating motor stops and, when the input voltage is turned on, the agitating motor rotates again.

As control of the duty ratio of the voltage according to the embodiment of the present invention, not only control of the duty ratio using a high frequency voltage but also control of the duty ratio using the low frequency voltage is possible.

Referring to FIG. 5, a curve a shows the cold water discharge performance of the conventional water purifier and a curve b shows the cold water discharge performance of the water purifier, to which the control method of the present invention is applied.

Specifically, when the defined cold water temperature of discharged drinking water is 8°C, the temperature of a first glass of cold water discharged from the conventional water purifier was measured at 4°C or less. This is because the agitator constantly rotated at a maximum set speed at the same time as reception of the water discharge command and thus the amount of heat exchanged between the coolant and the cold water pipe was large. In this case, the gums of a certain user may ache because the temperature of the cold water is very low.

When cold water is continuously discharged, as shown in the figure, it can be seen that the temperature of cold water rapidly increases starting from a second glass of cold water. Up to four glasses of cold water may be discharged and then drinking water having a higher temperature than cold water is discharged. This means that the temperature of the coolant rapidly increases by heat exchange between the coolant and room-temperature drinking water passing through the cold water pipe and thus heat exchange efficiency is lowered.

In contrast, in the water purifier, to which the control method of the present invention is applied, the temperature of a first glass of cold water after a water discharge command was measured at about 6°C.

This is because the temperature of the coolant when the water discharge command is received is less than the lower limit temperature or is between the lower limit temperature and the upper limit temperature and thus the duty ratio of the voltage for driving the agitator is less than 100%. As a result, the temperature of cold water first discharged after the water discharge command is relatively higher than that of the conventional water purifier and the user does not feel much difference.

When the rotation speed of the agitator is controlled using the duty ratio to limit the amount of exchanged heat in a continuous water discharge process, the initial temperature of discharged cold water is high but the temperature rising slope of the coolant is gently formed and the discharge amount of cold water is increased.

That is, by dispersing initial cold air loss (area A) to the later part (area B), it is possible to increase the discharge amount of cold water in a state in which a difference between the initial and later cold water temperatures is not large.

Claims

A method of controlling a water purifier, the method comprising:

receiving a cold water discharging command;

sensing a temperature of coolant at a predetermined time interval when the cold water discharging command is received; and

supplying a voltage to an agitating motor to rotate an agitator, when cold water is discharged,

wherein, while cold water is discharged, a rotation speed of the agitator is changed according to change in temperature of the coolant.
The method of claim 1, wherein the rotation speed of the agitator is changed by controlling a duty ratio of the voltage supplied to the agitating motor.
The method of claim 2, wherein the duty ratio of the voltage supplied to the agitating motor is increased as the temperature of the coolant is increased.
The method of claim 3, wherein, when the temperature of the coolant exceeds an upper limit temperature, the agitating motor is driven with a duty ratio of 100%.
The method of claim 4, wherein, when the temperature of the coolant is less than a lower limit temperature, the agitating motor is driven with a duty ratio of 70 to 75%.
The method of claim 5, wherein, when the temperature of the coolant is between the upper limit temperature and the lower limit temperature, the agitating motor is driven with a duty ratio of 80 to 85%.
The method of claim 6, wherein a coolant temperature range between the lower limit temperature and the upper limit temperature is divided into a plurality of sections,

wherein the duty ratios of the agitating motor for respective sections are differently set.
The method of claim 1, wherein, when a water discharge stop command is received, the agitating motor is further driven for a set time with a duty ratio at the time of receiving the water discharge stop command, and then is stopped.
The method of claim 2, wherein the voltage supplied to the agitating motor is a high-frequency voltage.
The method of claim 2, wherein the voltage supplied to the agitating motor is a low-frequency voltage.