System and method for controlling temperature of refrigerant in air conditioner

There is provided a system and method for controlling a temperature of a refrigerant in an air conditioner, in which a supercooling degree and/or a superheating degree can be secured by controlling a difference in refrigerant temperatures of a pipe connecting one or more indoor units to one or more outdoor units, and a flow of a specific refrigerant. The system includes: one or more indoor units; one or more outdoor units; a high-pressure pipe and a low-pressure pipe for connecting the indoor units and the outdoor units; and a refrigerant temperature control unit coupled to the high-pressure pipe and the low-pressure pipe, for performing a heat exchange with respect to flowing refrigerants by coupling an inner pipe to an outer pipe, the inner pipe passing through the another pipe. The refrigerant temperature control unit is installed in one side of the high-pressure or low-pressure pipe and senses a supercooling degree and/or a superheating degree and increasing/decreasing a refrigerant inlet flow to the outer pipe through a bypass passage, which couples the outer pipe to a specific pipe, so as to make the sensed supercooling or superheating degree equal to a target value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air conditioner, and more particularly, to a system and method for controlling a temperature of a refrigerant in an air conditioner, in which a supper-heating degree and/or a supper-cooling degree can be secured by controlling an amount of refrigerant which is heat exchanged due to a difference in temperature of refrigerant at a predetermined position of a pipe connecting an indoor unit and an outdoor unit.

2. Description of the Related Art

An air conditioner is an apparatus that can control air temperature, humidity, stream and cleanliness so as to make comfortable circumference. Recently, a multi-type air conditioner has been developed. The multi-type air conditioner includes a plurality of indoor units installed in partitioned spaces and controls air temperatures of the respective spaces.

A heat pump system can be used both as a cooling system and a heating system in accordance with a refrigeration cycle and a heating cycle. The refrigeration cycle makes a refrigerant flow through a normal passage and the heating cycle makes a refrigerant flow through a reverse passage.

FIG. 1illustrates a relationship of a general refrigeration cycle and a Molier diagram. As shown inFIG. 1, the refrigeration cycle is performed by iterative operations of refrigerant compression, condensation, expansion and vaporization.

A compressor10compresses an introduced refrigerant and discharges a high-temperature and high-pressure heated vapor to an indoor heat exchanger15. At this point, a state of the refrigerant discharged from the compressor10becomes a superheating degree (SH), which exceeds a saturated state on the Molier diagram.

An outdoor heat exchanger15performs a heat exchange between the discharged high-temperature and high-pressure refrigerant with an outdoor air, resulting in a phase change into a liquid state. At this point, heat of the refrigerant is removed by air passing through the outdoor heat exchanger15, such that its temperature is rapidly lowered. As a result, the refrigerant is transferred in a liquid state of a supercooling degree (SC).

An expander20decompresses the suppercooled refrigerant, making it easy to evaporate the refrigerant at the indoor heat exchanger25.

The indoor heat exchanger25performs a heat exchange between the decompressed refrigerant with the outdoor air. At this point, heat of the refrigerant is removed by air passing through the indoor heat exchanger, such that its temperature increases. As a result, phase of the refrigerant is changed into a liquid state.

The refrigerant introduced from the indoor heat exchanger25to the compressor10becomes a gaseous state of a superheating degree TSH, in which it is evaporated over the saturated state.

In the relationship between the refrigeration cycle and the Molier diagram, the refrigerant passes through the compressor10, the outdoor heat exchanger15, the expander20, and the indoor heat exchanger25. The refrigerant discharged from the indoor heat exchanger25is again introduced into the compressor10.

While the refrigerant is transferred from the indoor heat exchanger25to the compressor10, the phase of the refrigerant is changed into the superheating degree. That is, the refrigerant introduced into or discharged from the compressor10must be a complete liquid state.

However, it is a theoretical result and a predetermined error occurs in an actual application to the products. Also, when an amount of refrigerant flowing during the refrigeration cycle is relatively small or large compared with the heat exchange state, the phase change does not occur completely in the respective processes.

Due to these problems, the refrigerant introduced from the indoor heat exchanger25to the compressor10is not changed into a complete superheated vapor and it often exists in a liquid state. When the refrigerant of a liquid state is accumulated in an accumulator (not shown) and introduced into the compressor10, a noise occurs increasingly and performance of the compressor is degraded.

Also, when the heat pump system changes from the heating mode to the defrosting mode or from the defrosting mode to the heating mode, a probability that the refrigerant of a liquid state will be introduced into the compressor10is very high. The reason for this is that the refrigerant flow is changed while the heat exchanger acting as the indoor heat exchanger operates as a condenser during the mode switching process and, on the contrary, the heat exchanger acting as the outdoor heat exchanger operates as an evaporator.

The refrigerant introduced into the compressor10is made to have the superheating degree (TSH) by controlling a flow rate of the refrigerant using the expander20, thereby preventing a phenomenon that the refrigerant of a liquid state is excessively accumulated in the accumulator and then introduced into the compressor. Here, the expander20includes a linear electronic expansion valve (LEV) or an electronic expansion valve (EEV). This valve will be referred to as an EEV.

The multi-type air conditioner includes at least one outdoor unit and a plurality of indoor units connected to the outdoor unit, and it operates in a heating mode and a cooling mode. Such a multi-type air conditioner tends to be developed to selectively operate in a heating or cooling mode with respect to the individual rooms.

The related art air conditioner has following problems.

As a supercooling degree for the inlet flow of the indoor unit is degraded according to installation conditions of short/medium/long pipes and height differences, a refrigerant flow noise occurs severely due to the expander included in the indoor unit.

In the related art air conditioner, a current state of the refrigerant is measured using a sensor or the like, which is installed in the inlet and outlet pipes of the outdoor heat exchanger or the compressor. Then, a supercooling degree and a superheating degree are calculated and controlled using the current state of the refrigerant. In this case, however, there occurs a problem in that the supercooling degree cannot be secured due to a pressure loss under the installation conditions of the long pipe and height difference.

Also, the supercooling degree may be degraded because the multi-type air conditioner has a bad branching characteristic or a length of the pipe after a branched pipe is long.

Further, when a refrigerant noise claim occurs in the multi-type air conditioner, an algorithm for the outdoor unit or a structural design must be modified.

Like this, it may be difficult to secure the supercooling degree due to the pressure loss or heat loss, which occurs under the installation conditions of the long pipe and height difference. In this case, a refrigerant noise may occur very seriously.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an air conditioner that substantially obviates one or more problems due to limitations and disadvantages of the related art.

A first object of the present invention is to provide a system and method for controlling a temperature of a refrigerant in a multi-type air conditioner, in which a supercooling degree and/or a superheating degree can be secured. The system includes a refrigerant temperature control unit between a high-pressure pipe and a low-pressure pipe. One pipe passes through another pipe and the supercooling degree and/or the superheating degree is secured using a temperature difference of a flowing refrigerant and controlling an amount of a refrigerant through a bypass passage.

A second object of the present invention is to provide a system and method for controlling a temperature of a refrigerant, which can secure a supercooling degree using a temperature difference of refrigerants flowing through a high-pressure pipe and a low-pressure pipe under a control of a supercooling degree control unit installed in a predetermined position of the high-pressure and low-pressure pipes.

A third object of the present invention is to provide a system and method for controlling a temperature of a refrigerant, in which a superheating degree can be secured using a temperature of refrigerants flowing through a high-pressure pipe and a low-pressure pipe under a control of a superheating control unit installed in a predetermined position of the high-pressure and low-pressure pipes.

A fourth object of the present invention is to provide a system and method for controlling a temperature of a refrigerant in an air conditioner, in which a supercooling degree and a superheating degree can be simultaneously secured using a supercooling/superheating degree control unit installed at a predetermined position of high-pressure and low-pressure pipes.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a system for controlling a temperature of refrigerant in an air conditioner includes: one or more indoor units; one or more outdoor units; a high-pressure pipe and a low-pressure pipe for connecting the indoor units and the outdoor units; and a refrigerant temperature control unit coupled to the high-pressure pipe and the low-pressure pipe, for performing a heat exchange with respect to flowing refrigerants by coupling an inner pipe to an outer pipe, the inner pipe passing through the another pipe, the refrigerant temperature control unit installed in one side of the high-pressure or low-pressure pipe, for sensing a supercooling degree and/or a superheating degree and increasing/decreasing a refrigerant inlet flow to the outer pipe through a bypass passage, which couples the outer pipe to a specific pipe, so as to make the sensed supercooling or superheating degree equal to a target value.

Preferably, the refrigerant temperature control unit may be one of a supercooling degree control unit, a superheating degree control unit and a supercooling/superheating degree control unit.

According to another embodiment of the present invention, a method for controlling a temperature of a refrigerant includes the steps of: performing a heat exchange due to a difference of a temperature between a high-pressure refrigerant and a low-pressure refrigerant using a heat exchanging part, the heat exchanging part including an inner pipe and an outer pipe whose both ends are coupled to high-pressure and low-pressure pipes connecting at least one indoor unit and at least one outdoor unit; sensing a supercooling degree and/or a superheating degree at pipes disposed at one side of the heat exchanging part; and securing a supercooling degree and/or a superheating degree by increasing/decreasing a predetermined amount of a refrigerant flowing into an outer pipe of the heat exchanging part such that the sensed supercooling degree and/or superheating degree are/is made to be equal to a target value.

According to the present invention, the refrigerant temperature control unit is installed between the high-pressure pipe and the low-pressure pipe and controls a temperature difference and amount of a refrigerant flowing through two pipes, thereby securing a supercooling degree or a superheating degree or a supercooling/superheating degree. Accordingly, it is possible to secure the supercooling degree and/or the superheating degree regardless of operation cycle characteristics.

DETAILED DESCRIPTION OF THE INVENTION

It is preferable that an air conditioner according to the present invention includes one or more outdoor units and one or more indoor units. The present invention can be applied to a cooling/heating switching type product and a multi-type air conditioner which can operate in a cooling mode, a heating mode, a cooling-based concurrent cooling/heating mode, and a heating-based concurrent cooling/heating mode.

FIG. 2is a schematic view of an air conditioner according to the present invention.

Referring toFIG. 2, an air conditioner includes one or more outdoor units100and one or more indoor units110. The units100and110are coupled through pipes121and122. A refrigerant temperature control unit130for controlling a temperature of a refrigerant is installed between the pipes so as to secure a supercooling degree and/or a superheating degree of the pipe121and122.

The outdoor unit100includes a compressor101, one or more outdoor heat exchangers103and104, and EEVs105and106installed in inlet sides of the outdoor heat exchangers103and104.

The indoor unit110is installed in each partitioned room and includes one or more indoor EEVs112and one or more indoor heat exchangers114. Headers111and116are installed on both sides of the indoor heat exchanger.

Such an air conditioner constructs a closed circuit by sequentially connecting the compressor101, the outdoor heat exchangers103and104, the outdoor EEVs105and106, the indoor EEV112, and the indoor heat exchanger114through refrigerant pipes.

A refrigerant pipe for connecting an outlet side of the compressor101to an inlet side of the indoor EEV112is a high-pressure pipe121that guides a flow of a high-pressure refrigerant discharged from the compressor101, and a refrigerant pipe for connecting an outlet side of the indoor EEV112to an inlet side of the compressor101is a low-pressure pipe122that guides a flow of a low-pressure refrigerant expanded at the indoor EEV112. Accordingly, the outdoor heat exchangers103and104are installed on passage of the high-pressure pipe121, and the indoor heat exchangers are installed on passage of the low-pressure pipe122.

If the compressor101is driven, the discharged refrigerant is switched depending on a cooling mode or a heating mode by a passage switching valve (not shown) and it flows in an opposite direction.

Here, the supercooling degree is controlled using a high-pressure sensor107and a temperature senor108, which are disposed at the outlet side of the compressor101. Also, the superheating degree is controlled using temperature sensors113and115, which are disposed at the inlet and outlet sides of the indoor heat exchanger114.

Regarding the relationship between the refrigeration cycle and Molier diagram based on the above-described operation cycle, the refrigerant transferred from the compressor101through the outdoor heat exchangers103and104to the indoor heat exchanger114must secure the supercooling degree. On the contrary, the refrigerant transferred from the indoor heat exchanger114to the compressor101must secure the superheating degree. Also, the refrigerant introduced into the compressor101or discharged thereto must be a complete liquid state.

For this purpose, the refrigerant temperature control unit130for securing the supercooling degree and/or the superheating degree is installed at predetermined positions of the high-pressure and low-pressure pipes121and122that connect the outdoor unit100to the indoor unit110.

The refrigerant temperature control unit130can be installed closer to the indoor unit110, that is, adjacent to the indoor EEV112and the indoor heat exchanger114. Also, when the refrigerant temperature control unit130is installed in front ends of the headers111and115and bridges, the supercooling degree can also be secured.

Also, the refrigerant temperature control unit130can be provided with a single unit such that it independently controls a refrigerant temperature without communication with the indoor and outdoor units. In this case, it is preferable to supply a separate voltage to a board. Further, in the presence of an existing communication line, the refrigerant temperature control unit130can transmit and receive refrigerant states (temperature, pressure) so as to communicate with other units.

FIG. 3is a view of the refrigerant temperature control unit130.

Referring toFIG. 3, the refrigerant temperature control unit130includes a heat exchanging part131, a refrigerant temperature sensing part132, and a refrigerant temperature control unit135. The heat exchanging part131is connected to the high-pressure and low-pressure pipes121and122and performs a heat exchange due to a difference of a refrigerant temperature. The refrigerant temperature sensing part132is installed on one side of the pipe and senses a supercooling. The refrigerant temperature control unit135controls a heat exchanged amount of the heat exchanging part131according to the sensing result of the refrigerant temperature sensing part132.

Here, the heat exchanging part131is installed in a dual pipe type such that the heat can be exchanged using a difference of temperature between a room-temperature and high-pressure refrigerant of the high-pressure pipe121and a low-temperature and low-pressure refrigerant of the low-pressure pipe122. In the dual pipe, an inner pipe may be coupled to the high-pressure pipe and an outer pipe may be extended to an outside of the inner pipe and coupled to the low-pressure pipe.

That is, the dual pipe of the heat exchanging part131is installed between portions which are cut away between the high-pressure and low-pressure pipes. In order for the heat exchange efficiency, the inner pipe is coupled in a predetermined shape (for example, a “” shape) and the outer pipe is formed in a cylindrical shape and installed extending larger than an outer radius of the inner pipe. As another example, it is preferable that the inner and outer pipes of the dual pipe are formed in a shape such that the heat exchange efficiency between the refrigerants can increase. Also, a heat-sinking fin can be formed in an outside of the inner pipe or an inside of the outer pipe.

The refrigerant temperature sensing part132includes one or more sensors that can sense the supercooling degree and/or the superheating degree at the pipes. That is, the refrigerant temperature sensing part132includes one or more temperature sensors134for sensing an outflow temperature of the pipe disposed at one side of the heat exchanging part131, and one or more temperature sensors or pressure sensors133for detecting a saturation temperature or a pressure of the high-pressure pipe. The pressure sensor133may be installed in the inlet side or the outlet side of the high-pressure pipe so as to measure a high-pressure and saturation temperature.

Here, the refrigerant temperature sensing unit132can operate as a supercooling degree sensing part and/or a superheating degree sensing part.

The refrigerant temperature control unit135includes a microcomputer (Micom)136and an EEV137. The microcomputer136calculates deviations in the supercooling/superheating degrees and target supercooling/superheating degrees according to the sensing result of the refrigerant temperature sensing unit132. Then, an opening degree of the EEV137is controlled to decrease the calculated deviation. In this manner, the heat exchanged amount of the heat exchanging part131is controlled.

Here, the refrigerant temperature control unit135can operate as a supercooling degree control unit and/or a superheating degree control unit.

The refrigerant temperature control unit130controls a supercooling degree TSCwith respect to the refrigerant transferred to the indoor unit110and controls a superheating degree TSHwith respect to the refrigerant transferred to the outdoor unit100. That is, an amount of a flowing refrigerant is controlled using a bypass, a branch and so on, so that at least one refrigerant can supercool or superheat other refrigerants by controlling differences in pressure and temperature of two pipes and the heat exchanged amount of the refrigerant.

When the refrigerant temperature control unit130operates as the supercooling degree control unit, the superheating degree control unit or the supercooling/superheating degree control unit, the respective embodiments of the refrigerant temperature control unit10will now be described.

First Embodiment

FIGS. 4 to 6are views illustrating constructions of various examples of a supercooling degree control unit200according to a first embodiment of the present invention.

Referring toFIG. 4, the superheating degree control unit200includes a heat exchanging unit201; sensors202and203; and a bypass pipe204and an EEV205for controlling the supercooling.

The heat exchanging unit201has an inner pipe201aand an outer pipe201b, which are correspondingly connected to and between a high-pressure pipe121and a low-pressure pipe122. The inner pipe201ahas both ends connected to an inlet side and an outlet side of the high-pressure pipe121, and it is bent to have a “” shape. The outer pipe201bhas both ends connected to an inlet side and an outlet side of the low-pressure pipe122, and it extends to an outside of the inner pipe201ato allow a flow of a low-temperature and low-pressure refrigerant.

Here, the high-pressure pipe121is connected to the outdoor heat exchanger at its inlet side to introduce a two phase flow, and it is connected to the indoor EEV at its outlet side and discharge a liquid phase by heat exchange. The low-pressured pipe122is connected to the indoor heat exchanger at its inlet side and is connected at its outlet side to an inhalation side of the compressor.

Additionally, the supercooling degree sensing unit (not shown) includes a first temperature sensor202and a second temperature sensor3. The first temperature sensor202is installed at the high-pressure pipe121of the inlet side of the heat exchanging unit201, and the second temperature sensor203is installed at the high-pressure pipe121of the outlet side of the heat exchanging unit201.

The first temperature sensor202senses the temperature of the high-pressure pipe121to sense a pressure of the high-pressure pipe121, and senses a high-pressure saturation temperature on a Molier diagram. The second temperature sensor203senses the temperature corresponding to a current discharge temperature of the heat-exchanged high-pressure pipe121.

Additionally, the supercooling degree control unit (not shown) includes the bypass pipe204branched from the high-pressure pipe121of the inlet side of the heat exchanging unit201to connect the high-pressure pipe121with the outer pipe201b; the EEV205installed at an air passage of the bypass pipe204to control the flow amount of the refrigerant; and the microcomputer203for controlling the EEV205.

Here, the branched bypass pipe121has a refrigerant temperature lower than a temperature of the refrigerant flowing to the high-pressure pipe121by a branch pressure.

At this time, the microcomputer230subtracts a second temperature sensed at the second temperature sensor203from a first temperature sensed from the first temperature sensor202to calculate the supercooling degree. The calculated supercooling degree increases and decreases an opening of the EEV205such that the calculated supercooling degree is consistent with the target supercooling degree.

By doing so, the high temperature and high-pressure refrigerant and a low temperature and low-pressure refrigerant are heat-exchanged by the temperature difference between the inner pipe201aand the outer pipe201bof the heat exchanging unit201, and have the heat-exchanged amount of the heat exchanging unit201controlled by an amount of the refrigerant introduced into the bypass pipe204.

Here, since the sensed first temperature is not an actual saturation temperature, it is compensated as much as a predetermined temperature to calculate the saturation temperature.

Additionally, the supercooling degree (TSC) is obtained from the following Equation:
TSC=Tin2−Tin1where, TSCis a supercooling degreeTin1: a first temperature sensed by the first temperature sensor202Tin2: second temperature sensed by the second temperature sensor203.

FIG. 5is a view illustrating another construction of the supercooling degree control unit200according to the first embodiment of the present invention. Descriptions of the same elements as those ofFIG. 4are omitted in the following.

Referring toFIG. 5, the supercooling sensing unit (not shown) includes a high-pressure sensor212and a temperature sensor213of the high-pressure pipe121of the outlet side of the heat exchanging unit211. The supercooling sensing unit calculates the saturation temperature by using a high pressure sensed at the high-pressure sensor212.

At this time, the microcomputer230subtracts the saturation temperature (condensation temperature) sensed at the high-pressure sensor212from the temperature sensed at the outlet-side temperature sensor213, and controls the opening of the EEV215such that the obtained supercooling degree follows (or secures) the target supercooling degree.

Here, the supercooling degree (TSC) is obtained from the following Equation:
TSC=Tin−TL(Ps)where, Tin: temperature sensed by the outlet-side temperature sensorTL(Ps): pressure saturation temperature sensed by the high-pressure sensor.

FIG. 6is a view illustrating a further another construction of the supercooling degree control unit200according to the first embodiment of the present invention.

Referring toFIG. 6, the heat exchanging unit221of the supercooling degree control unit200has a dual pipe structure, which has the inner pipe221aconnected to both ends of the high-pressure pipe121and the outer pipe221bextended to the exterior of the inner pipe221a.

Additionally, the supercooling degree sensing unit includes the high-pressure sensor222and the temperature sensor223disposed at the outlet-side high-pressure pipe121of the heat exchanging unit221. The supercooling degree control unit includes a bypass pipe224branched from the high-pressure pipe121; an EEV225for controlling an amount of refrigerant; a high-pressure refrigerant inlet pipe225connected with the outer pipe221bof the dual pipe; and a check valve227or a bypass valve being one-directional refrigerant inlet unit.

The microcomputer230of the supercooling degree control unit senses the supercooling by using the high-pressure sensor222and the temperature sensor223. The microcomputer230controls the opening of the EEV225depending on the sensed result to heat-exchange the high temperature and high-pressure refrigerant of the inner pipe221awith a middle temperature and high-pressure refrigerant, which is branched from the high-pressure pipe121, of the outer pipe221b.

Here, the bypass pipe224branched from the high-pressure pipe121has a refrigerant temperature lower than a temperature of a refrigerant flowing due to the branch pressure in the high-pressure pipe121, thereby achieving a heat exchange at the heat exchanging unit.

Further, the high-pressure refrigerant flowing in the outer pipe221bof the heat exchanging unit221is introduced into the low-pressure pipe123through a high-pressure refrigerant inlet pipe226by opening the check valve227. At this time, the refrigerant flowing in the outer pipe211bof the heat exchanging unit221is in a high-pressure and the refrigerant flowing in the low-pressure pipe122is in a low-pressure. Therefore, the high-pressure refrigerant of the high-pressure refrigerant inlet pipe226flows to the low-pressure pipe122by a pressure difference.

Here, the supercooling degree (TSC) is obtained from the following Equation:
TSC=Tin−TL(Ps)where, Tin: discharge temperature sensed by the outlet-side temperature sensor223of the high-pressure pipeTL(Ps): pressure saturation temperature sensed by the high-pressure sensor222.
Second Embodiment

FIGS. 7 to 9are views illustrating constructions of various examples of a superheating degree control unit300according to a second embodiment of the present invention.

Referring toFIG. 7, the superheating control unit300has an inner pipe301aand an outer pipe301bconnected with each other between a high-pressure pipe121and a low-pressure pipe122. The inner pipe301aof the heat exchanging unit301has both ends connected to an inlet side and an outlet side of the low-pressure pipe122and is bent to have a “” shape. The outer pipe301bhas both ends connected to an inlet side and an outlet side of the high-pressure pipe121. A high temperature and low-pressure refrigerant flows through an outside of the inner pipe301a.

Additionally, the superheating degree sensing unit includes temperature sensors302and303. The first sensor302is installed at the inlet-side low-pressure pipe122of the heat exchanging unit301, and the second temperature sensor303is installed at the outlet-side low-pressure pipe122.

The first temperature sensor302senses a pressure of the low-pressure pipe122and senses a low-pressure side saturation temperature on Molier diagram. The second temperature sensor303senses a current temperature of the discharged refrigerant of the heat-exchanged low-pressure pipe122.

Additionally, the superheating degree control unit includes a bypass pipe304, an EEV305and a microcomputer (not shown). The bypass pipe is branched from the inlet-side low-pressure pipe122of the heat exchanging unit301to be connected to the low-pressure pipe122and an inside of the outer pipe301b. The EEV305is installed at a predetermined passage of the bypass pipe304to control an amount of the refrigerant flowing to the inside of the outer pipe301bthrough the bypass pipe304.

At this time, the microcomputer330subtracts the second temperature sensed at the second temperature sensor303from the first temperature sensed at the first temperature sensor302to calculate the superheating degree (TSH) to control the superheating degree. An opening of the electronic expansion value305is increased and decreased such that the calculated superheating degree is consistent with a target superheating degree. Accordingly, a heat-exchange amount is controlled by the refrigerant introduced into the bypass tube304and due to a temperature difference between the high temperature and high-pressure refrigerant, which flows through the inner pipe301a, and the low temperature and low-pressure refrigerant, which flows through the outer pipe301b.

In other words, if the current superheating degree is less than the target superheating degree, the opening of the EEV305is increased such that the heat-exchange amount is increased at the heat exchanging unit301to increase the current superheating degree. To the contrary, if the current superheating degree is more than the target superheating degree, the opening of the EEV305is decreased such that the heat-exchange amount is decreased at the heat exchanging unit301to decrease the current superheating degree.

Here, since the first temperature sensed at the first temperature sensor302is not an actual saturation temperature, it is compensated as much as a predetermined temperature to calculate the saturation temperature.

Additionally, the superheating degree (Tsh) is obtained in the following Equation:
Tsh=Tout2−Tout1where,Tsh: superheating degreeTout1: first temperatureTout2: second temperature.

FIG. 8is a view illustrating another construction of the superheating degree control unit300according to the second embodiment of the present invention.

As shown inFIG. 8, the superheating degree sensing unit includes a low-pressure sensor312and a temperature sensor313of an outlet-side low-pressure pipe122of the heat exchanging unit311. The low-pressure sensor312calculates a saturation temperature by using the low-pressure sensed by the low-pressure sensor312.

At this time, the microcomputer330subtracts the saturation temperature (condensation temperature) from the temperature sensed from the outlet-side temperature sensor313to obtain the superheating degree, and increases and decreases to control the opening of the EEV315such that the obtained superheating degree follows the target superheating degree.

Here, the superheating degree (Tsh) is obtained in the following Equation:
Tsh=Tout−TL(Ps)where,Tout: temperature sensed at the outlet-side temperature sensorTL(Ps): saturation temperature of the pressure sensed at the low-pressure sensor.

FIG. 9is a view illustrating a further another construction of the superheating degree control unit300according to the second embodiment of the present invention.

As shown inFIG. 9, the heat exchanging unit331of the superheating degree control unit300is configured in a dual pipe to connect the low-pressure pipe122to both ends of the inner pipe321aand to connect refrigerant inlet and outlet pipes326aand326bto both ends of the outer pipe321b.

Additionally, the superheating degree sensing unit includes a low-pressure sensor322and a temperature sensor of an outlet-side low-pressure pipe122.

Additionally, the superheating degree control unit includes an EEV327, a check valve327band the microcomputer330. The EEV327is installed at the refrigerant inlet pipe326aconnected between the high-pressure pipe121and the outer pipe321b. The check valve327bis installed at the refrigerant outlet pipe326bof the refrigerant flowing from the outer pipe321bto the high-pressure pipe121.

Additionally, the high-pressure sensor322and the temperature sensor323are used to sense the current superheating degree, and the opening of the EEV327ais increased and decreased depending on the sensed result to control the current superheating degree to follow the target superheating degree and control the heat-exchange amount of the heat exchanging unit321.

In other words, the refrigerant introduced into the outer pipe321bthrough the bypass pipe324is varied in amount depending on an opening control of the EEV325to control the heat-exchange amount of the heat exchanging unit321and the superheating degree. At this time, the high-pressure refrigerant flowing through the outer pipe321bof the heat exchanging unit321is again introduced into the high-pressure pipe121by the check valve327.

Here, the superheating degree (Tsh) is obtained in the following Equation:
Tsh=Tout−TL(Ps)where,Tout: temperature sensed at the outlet-side temperature sensor of the low-pressure pipeTL(Ps): saturation temperature of the pressure sensed at the outlet-side low-pressure sensor of the low-pressure pipe.
Third Embodiment

FIGS. 10 to 12are views illustrating constructions of a supercooling/superheating degree control unit400according to a fourth embodiment of the present invention.

Referring toFIG. 10, a heat exchanging unit401has a dual pipe structure of an inner pipe401aand an outer pipe401bto perform a refrigerant heat exchange therein. The inner pipe401ahas both ends connected to a high-pressure pipe121, and the outer pipe401bhas both ends connected to a low-pressure pipe122.

Additionally, the supercooling/superheating degree sensing unit (not shown) includes a plurality of temperature sensors402,403,408and409, that is, an inlet-side first temperature sensor402and an outlet-side second temperature sensor403of a high-pressure pipe121; and an inlet-side third temperature sensor408and an outlet-side fourth temperature sensor409of a low-pressure pipe122.

Here, the first temperature sensor402senses a temperature for calculating a saturation condensation temperature, the third temperature sensor408senses a temperature for calculating a saturation evaporation temperature, the second temperature sensor403senses a temperature of a heat-exchanged high-pressure pipe121, and the fourth temperature sensor409senses a temperature of a heat-exchanged low-pressure pipe122.

Additionally, the supercooling/superheating degree control unit (not shown) includes a bypass pipe404branched at an inlet side of the high-pressure pipe121to be connected to the outer pipe401b; an EEV405installed at the bypass pipe404to control an amount of the high-pressure refrigerant; and a microcomputer450.

In order to concurrently control the supercooling/superheating degrees, the microcomputer450subtracts the temperature sensed at the first temperature sensor402from the temperature sensed at the second temperature sensor403to detect the supercooling degree, and subtracts the temperature sensed at the third temperature sensor408from the temperature sensed at the fourth temperature sensor409to detect the superheating degree.

According to a condition of satisfying all of the detected supercooling and superheating degrees, the opening of the EEV405is increased and decreased to control a heat exchange degree of the heat exchanging unit401.

In other words, the condition of satisfying all of the detected supercooling and superheating degrees is obtained as follows:
Tout1<Tout2<Tin1<THEX<Tin2where,Tout1: temperature of the outlet-side third temperature sensor of the low-pressure pipe122Tout2: temperature of the outlet-side fourth temperature sensor of the low-pressure pipe122THEX: internal temperature of the heat exchanging unitTin1: temperature of the outlet-side first temperature sensor of the high-pressure pipeTin2: temperature of the outlet-side second temperature sensor of the high-pressure pipe.

Under the above condition, the supercooling degree of the high-pressure pipe121introduced into the indoor unit can be secured, and the superheating degree of the low-pressure pipe122introduced into the outdoor unit can be secured.

FIG. 11is a view illustrating another construction of the supercooling/superheating degree control unit400according to the third embodiment of the present invention.

Referring toFIG. 11, a heat exchanging unit411includes an inner pipe411ahaving both ends connected to a high-pressure pipe121; and an outer pipe411bhaving both ends connected to a low-pressure pipe122to perform a heat exchange between the refrigerants flowing through the inner pipe and the outer pipe.

Additionally, the supercooling/superheating degree sensing unit (not shown) includes a plurality of temperature sensors413and419, and pressure sensors412and418. That is, it includes an outlet-side first pressure sensor412and first temperature sensor413of the pressure pipe121; and an outlet-side second pressure sensor418and second temperature sensor of a low-pressure pipe. The first pressure sensor412is a high-pressure sensor, and the second pressure sensor418is a low-pressure sensor.

Here, a saturation condensation temperature is calculated from a high-pressure sensed at the first pressure sensor412, a saturation evaporation temperature is calculated from a high-pressure sensed at the second pressure sensor418, the first temperature sensor413senses a temperature of the heat-exchanged high-pressure pipe121, and the second temperature sensor419senses the temperature of the heat-exchanged low-pressure pipe122.

The supercooling/superheating degree control unit (not shown) includes a bypass pipe414branched from the inlet side of the high-pressure pipe121to be connected to the outer pipe411b; an EEV415installed at the bypass pipe414to control an amount of the high-pressure refrigerant; and a microcomputer450.

In order to concurrently control the supercooling/superheating degrees, the microcomputer450subtracts the saturation temperature sensed at the first pressure sensor412from the temperature sensed at the first temperature sensor413to detect the supercooling degree, and subtracts the saturation temperature sensed at the second temperature sensor.418from the temperature sensed at the second temperature sensor419to detect the superheating degree.

According to a condition of satisfying all of the detected supercooling and superheating degrees, the opening of the EEV415is increased and decreased to control a heat exchange degree of the heat exchanging unit411.

In other words, the condition of satisfying all of the detected supercooling and superheating degrees is obtained as follows:
Tout1<Tout2<Tin1<THEX<Tin2where,Tout1: low-pressure saturation temperature of the low-pressure pipeTout2: temperature of the outlet-side second temperature sensor of the low-pressure pipeTHEX: internal temperature of the heat exchanging unit411Tin1: saturation temperature of the outlet-side first pressure sensor of the high-pressure pipeTin2: temperature of the outlet-side first temperature sensor of the high-pressure pipe.

Under the above condition, the supercooling degree of the high-pressure pipe121introduced into the indoor unit can be secured, and the superheating degree of the low-pressure pipe122introduced into the outdoor unit can be secured.

FIG. 12is a view illustrating a further another construction of the supercooling/superheating degree control unit400according to the third embodiment of the present invention.

Referring toFIG. 12, the heat exchanging unit421of the supercooling/superheating degree control unit400include a high-pressure pipe121connected to both ends of an inner pipe421aand an outer pipe421b.

The supercooling/superheating control unit controls a heat-exchange amount through a bypass pipe424branched from the high-pressure pipe121and the EEV425, and connects the outer pipe421bof the heat exchanging unit421with the low-pressure pipe122by a check valve427.

Additionally, the supercooling/superheating degree sensing unit includes outlet-side first pressure sensor422and first temperature sensor423of a high-pressure pipe121, and outlet-side second pressure sensor428and second temperature sensor429of a low-pressure pipe.

The microcomputer450of the supercooling/superheating control unit-detects the supercooling degree by using the outlet-side first pressure sensor422and first temperature sensor423of the high-pressure pipe121, and detects the superheating degree by using the outlet-side second pressure sensor428and second temperature sensor429of the low-pressure pipe.

Additionally, the supercooling/superheating control unit includes a high-pressure refrigerant inlet pipe426connected with the outer pipe421bof a dual pipe; and a check valve427as one directional refrigerant inlet unit, to control the superheating degree of the low-pressure pipe122.

The microcomputer450calculates the supercooling degree by using the first pressure sensor422and the first temperature sensor423of the supercooling degree sensing unit. The microcomputer450controls an increase or a decrease of the opening of the EEV425according to the calculated superheating degree to control the heat-exchange amount between the high-pressure refrigerant branched from the high-pressure pipe121to flow into the outer pipe421band the high-pressure refrigerant flowing to the inner pipe421a.

Concurrently, according to the superheating degree calculated from the second pressure sensor428and the second temperature sensor429, the opening of the EEV425is controlled such that the check valve427is opened to allow the high-pressure refrigerant flowing into the outer pipe421bof the heat exchanging unit421to flow into the low-pressure pipe122through a high-pressure refrigerant inlet pipe426. At this time, since the outer pipe421bof the heat exchanging unit421is in a high pressure, and the low-pressure pipe122is in a low-pressure, the high-pressure refrigerant of the high-pressure refrigerant inlet pipe426is transmitted to the low-pressure pipe122due to a pressure difference to secure the superheating degree.

In other words, the condition of satisfying all of the detected supercooling and superheating degrees is obtained as follows:
Tout1<Tout2<Tin1<THEX<Tin2where,Tout1: saturation temperature sensed at the outlet-side second pressure sensor of the low-pressure pipeTout2: temperature of the outlet-side second temperature sensor of the low-pressure pipeTHEX: internal temperature of the heat exchanging unitTin1: high-pressure saturation temperature of the inlet-side first pressure sensor of the high-pressure pipeTin2: temperature of the outlet-side second temperature sensor of the high-pressure pipe.

Under the above condition, the supercooling degree of the high-pressure pipe121introduced into the indoor unit can be secured, and the superheating degree of the low-pressure pipe122introduced into the outdoor unit can be secured.

FIG. 13is a view illustrating a still another construction of the supercooling/superheating degree control unit400according to the third embodiment of the present invention.

Referring toFIG. 13, the superheating degree control unit detects an inlet-side temperature (T121) of a high-pressure pipe121and a temperature (T433) sensed by an outlet-side temperature sensor433of a heat-exchanged high-pressure pipe, and obtains an internal temperature (THEX) of the heat exchanging unit431.

Further, a temperature (T438) sensed by an inlet-side third temperature sensor438of the low-pressure pipe122and a temperature (T439) sensed by a fourth temperature sensor439of the heat-exchanged low-pressure pipe122are obtained. Here, in order to concurrently secure the superheating degree and the supercooling degree, the supercooling degree and the superheating degree are concurrently controlled to be in a sequence of T428<T429<THEX<T423<T121.

Here, the inlet-side temperature of the high-pressure pipe121and the internal temperature of the heat exchanging unit431can be respectively sensed using a temperature sensor, and the temperature sensor is installed only at a side of the high-pressure pipe to sense the internal temperature of the heat exchanging unit by using a temperature difference of before/after a heat exchange.

Fourth Embodiment

FIG. 14is a view illustrating a construction of the supercooling/superheating degree control unit400according to a fourth embodiment of the present invention.

Referring toFIG. 14, a refrigerant temperature control unit500is comprised of a supercooling degree control unit510and a superheating degree control unit520. The supercooling degree control unit510is installed at a side of an indoor unit, and the superheating degree control unit520is installed at a side of an outdoor unit.

The supercooling degree control unit510detects the supercooling degree by using a first pressure sensor502and a first temperature sensor503. Since a high-pressure connection pipe121aof a heat exchanging unit501is connected with a high-pressure pipe121through an inner pipe501a, a bypass pipe504branched from the high-pressure connection pipe121ais connected to an outer pipe501b.

At this time, a microcomputer530calculates a current supercooling degree to control an increase or decrease of an opening of an EEV505such that the current supercooling degree is consistent with the target supercooling degree. Accordingly, an amount of refrigerant flowing through the outer pipe501bis controlled.

Additionally, the microcomputer530detects the current superheating degree by using a second pressure sensor512and a second temperature sensor513. A bypass pipe514branched from the high-pressure pipe121of the heat exchanging unit controls an amount of refrigerant applied to the outer pipe511bby controlling the opening of the EEV515. This superheating degree control operation is as described above.

In other words, according to the fourth embodiment of the present invention, the supercooling degree control unit is installed at the indoor unit to secure the supercooling degree of the high-pressure pipe, and the superheating degree control unit is installed at the outdoor unit to secure the superheating degree of the low-pressure pipe. These control units are preferably installed as a single unit.

FIG. 15illustrates a Molier diagram on which the supercooling degree is increased by the inventive superheating degree control unit. InFIG. 15, a dotted line and a solid line illustrate the Molier diagrams caused by refrigerants different from each other.

The supercooling degree control unit secures the supercooling degree of the refrigerant heat-exchanged at the outdoor heat exchange and introduced into the EEV. Therefore, a temperature point (A) sensed at the temperature sensor is compensated up to a saturation temperature point (B) and then, the supercooling degree of a high-pressure (Pd) saturation point is increased by the supercooling degree control unit. Accordingly, at the Pd point, the supercooling degree at the outlet side is secured in the outdoor heat exchanger. Additionally, the Molier diagram is increased up to an inlet-side temperature (C) of the indoor EEV.

Additionally, the inlet-side superheating degree (TSH) of the compressor can be secured. Here, “S1” denotes a temperature point sensed at a pipe temperature sensor of an indoor entrance under a low-pressure (Ps), “S2” denotes a temperature sensed at a pipe temperature sensor of an indoor exit, “S3” denotes a temperature sensed at a discharge pipe temperature sensor under a high pressure (PD), and “S4” denotes a temperature sensed at an outlet-side pipe temperature sensor of an outdoor heat exchanger.

FIG. 16illustrates an application example of the system according to the present invention.

Referring toFIG. 16, at least one outdoor unit601to605connected by long, medium and short pipes is installed at the outdoors600. At least one indoor unit611to617is installed at each of indoor room610. Accordingly, according to an operation condition, a multi air conditioner for a combined cooling and heating is provided for selectively performing an all-room cooling operation, an all-room heating operation, a cooling-based concurrent cooling and heating operation, and a heating-based concurrent cooling and heating operation.

The refrigerant temperature control units621,622,623,624and625, which are installed at a predetermined position between the pipes of the air conditioner, are installed between the indoor unit and the outdoor unit, or respectively installed at an entrance of a bridge type indoor unit and at a front of the indoor unit. Each of the refrigerant temperature control units621,622,623,624and625is controlled such that the supercooling degree and the superheating degree are consistent with the target temperature on the pipe between the indoor unit and the outdoor unit.

FIG. 17illustrates a method for controlling a refrigerant temperature according to a preferred embodiment of the present invention.

Referring toFIG. 17, it is determined to control a refrigerant temperature whether the supercooling degree is controlled or the superheating degree is controlled (S101, S113). At this time, this determination can be different depending on any priority for the supercooling degree and the superheating degree. In other words, in a cooling operation mode, the superheating degree is first controlled, and in a heating operation mode, the supercooling degree is first controlled.

Additionally, in case that the supercooling degree is controlled, the outlet-side refrigerant temperature and high pressure of the heat exchanging unit (for example, dual pipe) are sensed (S103), and the sensed pressure and temperature are used to sense the current supercooling degree (S105).

The sensed supercooling degree is compared with a predetermined target supercooling degree to detect the deviation therebetween (S107). The opening of the EEV is controlled to reduce the detected deviation such that the current supercooling degree is consistent with the target supercooling degree (S109). At this time, an internal heat-exchange amount is increased or decreased due to the high-pressure refrigerant of the dual pipe, which is the heat exchanging unit to secure the supercooling degree (S111).

Meanwhile, in case that the superheating degree is controlled (S113), the refrigerant temperature and pressure are sensed at the outlet side of the low-pressure pipe of the dual pipe (S115), and the current superheating degree is calculated (S117). If the superheating degree is calculated, the deviation between the current superheating degree and the target superheating degree is obtained (S119). After that, the opening of the EEV is controlled such that the current superheating degree is consistent with the target superheating degree to reduce the deviation (S121). At this time, the internal heat-exchange amount is increased or decreased due to the high-pressure refrigerant of the dual pipe to secure the superheating degree (S111).

As described above, the present invention can solve the installation position of the temperature sensor and the pressure sensor by using a specific sensing unit for performing an accurate sensing irrespective of an inside/outside of the pipe, can use the sensed temperature of the heat exchanging unit, and can use the temperature difference of before/after the heat exchange of the pipe.

Further, the present invention can secure the supercooling degree/the superheating degree by controlling the supercooling degree/the superheating degree for a refrigerant flowing cycle for a cooling operation, and for an oppositely flowing cycle for a heating operation.

As described above, the inventive temperature control unit and method of a refrigerant air conditioner controls the temperature of the refrigerant between the indoor unit and the outdoor unit to selectively control to secure the supercooling degree of the refrigerant flowing to the indoor unit or the superheating degree of the refrigerant flowing to the outdoor unit, and to concurrently control the supercooling degree and the superheating degree, thereby securing the supercooling degree and the superheating degree irrespective of a characteristic of an operation cycle.

Furthermore, the present invention has an effect in that the supercooling degree and the superheating degree are secured, thereby reducing a refrigerant noise. Specifically, a supercooling effect is remarkable in the long pipe.

Additionally, the present invention has an effect in that a module type is installed before and after the header and the branch, thereby achieving a simple installation without disassembling the indoor unit and the outdoor unit. Further, the present invention has an effect in that an independent control can be performed by an independent power supply even without the communication between the indoor unit and outdoor unit.

Further, the present invention has an effect in that the superheating degree can be secured during the cooling operation, thereby preventing a freezing and a fluid compression, in that in case that there is an excessive mass flow such as a weak wind operation of the air conditioner, the mass flow can be controlled.