Air conditioner

The air conditioner includes a first and a second heat exchanger, a plurality of compressors, a pipe for uniform distribution of oil, a plurality of oil separators, and an oil return opening. The first heat exchanger performs heat exchange between air of an indoor space and refrigerant to condition the air. The second heat exchanger is connected to the first heat exchanger through a pipe, to perform heat exchange between the refrigerant and water. The plurality of compressors is installed at one side of the second heat exchanger, to compress the refrigerant to a high temperature and a high pressure. The pipe for uniform distribution of oil communicates the plurality of compressors with each other, to guide a flow of oil within the plurality of compressors to flow between the compressors. Each oil separator is provided at an outlet of a respective compressor, to separate oil included in refrigerant discharged from the compressors. The oil return opening guides the oil separated by each of the oil separators to flow into all or any one of the plurality of compressors.

This application claims priority from Korean Patent Application 10-2006-0100614, filed Oct. 17, 2006, which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a water cooled air conditioner, and more particularly, to a water cooled air conditioner including a plurality of compressors for compressing refrigerant and a plurality of oil separators for filtering oil discharged from the compressors, and having a constitution which allows the oil filtered in the plurality of oil separators to return into all or any one of the plurality of compressors.

2. Description of the Related Art

An air conditioner is a cooling/heating apparatus installed in an indoor space such as an office or a home to cool or heat air of the indoor space. The air conditioner uses a repeating refrigerating cycle made up of compression, condensation, expansion, and evaporation operations. The air conditioner discharges heat of condensation or heat of evaporation into an outdoor space generally using air of the outdoor space.

Generally, an air conditioner includes an indoor unit conditioning the air of the indoor space by exchanging heat with the air of the indoor space and an outdoor unit connected to the indoor unit through a pipe, in which refrigerant exchanges heat with outdoor air. Also, an indoor heat exchanger in which the air of the indoor space exchanges heat with the refrigerant is provided in the indoor unit, and an outdoor heat exchanger in which a compressor compressing the refrigerant that exchanges heat with the outdoor air is provided in the outdoor unit.

Meanwhile, the compressor compressing the refrigerant to a high temperature and a high pressure is installed in the outdoor unit of the air conditioner. That is, the compressor, having a cylindrical shape with a predetermined diameter, is provided to compress the refrigerant into a high temperature/pressure gaseous state. Also, one or a plurality of compressors are provided in the outdoor unit.

However, when only one compressor compressing the refrigerant into the high temperature and pressure gas is provided, a problem occurs in that the compressor (having a limited compressing capacity) is damaged by an operation overload when conditioning air of the indoor space. Also, excessive load in the compressor reduces the operating lifespan of the compressor.

Also, oil flow between the compressors does not occur when a plurality of compressor are used. That is, an oil separator, which returns oil discharged from the compressors, is installed in one side of each of the compressors, and the oil separated in each of the oil separators is returned into each of the compressors through a return pipe.

Therefore, the oil discharged from each of the compressors is returned into each of the compressors and oil flow between the compressors does not occur.

Thus, because each of the compressors is operated at a different capacity, an oil shortage occurs in any one compressor having a larger capacity and an oil surplus occurs in another compressor having a smaller capacity.

When the oil shortage of the compressor occurs, the compressor is damaged during operation of the compressor. Also, servicing costs increase and product reliability decreases if the compressor is damaged.

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.

An object of the present invention is to provide an air conditioner that allows oil flow between a plurality of its compressors, thereby preventing damage of the compressors.

Another object of the present invention is to provide an air conditioner including a plurality of compressors and an oil separator for separating oil discharged from the compressors, and having a constitution which allows the oil filtered from each of the oil separators to flow into another compressor as well as the discharging compressor.

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 an air conditioner including: a first heat exchanger for performing heat exchange between air of an indoor space and refrigerant to condition the air; a second heat exchanger connected to the first heat exchanger through a pipe, for performing heat exchange between the refrigerant and water; a plurality of compressors installed at one side of the second heat exchanger, for compressing the refrigerant to a high temperature and a high pressure; a pipe for uniform distribution of oil communicating the plurality of compressors with each other, for guiding a flow of oil within the plurality of compressors to flow between the compressors; a plurality of oil separators respectively provided at an outlet of each of the plurality of compressors, for separating oil included in refrigerant discharged from the compressors; and an oil return opening for guiding the oil separated by each of the oil separators to flow into all or any one of the plurality of compressors.

In another aspect of the present invention, there is provided an air conditioner including: a plurality of compressors compressing refrigerant to a high temperature and a high pressure; and a plurality of pipes for uniform distribution of oil communicating the plurality of compressors with each other, for guiding a flow of oil within the plurality of compressors to flow between the compressors, wherein the plurality of pipes for uniform distribution of oil guide oil from within any one compressor to inlets of other compressors from the plurality of compressors.

In a further aspect of the present invention, there is provided an air conditioner including: a plurality of compressors for compressing refrigerant to a high temperature and a high pressure; a plurality of oil separators respectively provided at one side of the plurality of compressors, for separating oil included in refrigerant discharged from the plurality of compressors; and an oil return opening for guiding the oil separated by each of the oil separators to flow into all or any one of the plurality of compressors.

In an air conditioner according to the present invention, a pair of compressors is provided, and an oil return opening and a pipe for uniform distribution of oil are connected to each of the compressors. A pipe for uniform distribution of return oil communicated with an inlet of another compressor is formed in the oil return opening and a return valve selectively opening and closing the pipe for uniform distribution of return oil is installed in the pipe for uniform distribution of return oil. Also, a uniform oil valve selectively opening and closing the pipe for uniform distribution of oil is installed in the pipe for uniform distribution of oil.

Also, in an air conditioner according to the present invention, oil discharged from any one compressor between two compressors can be provided into the discharging compressor and another compressor. Therefore, a suitable oil pressure is attained between the plurality of compressors, thereby preventing an oil shortage due to partiality of oil toward one side of the compressor.

Also, the oil can be uniformly returned into each of compressors by providing a return valve capable of controlling an opening degree of the valve in a pipe for uniform distribution of return oil such that the oil is returned into another compressor. That is, a compressor having a large load capacity can return more oil than a compressor having a small load capacity. Therefore, oil supply according to an amount of oil discharged from each of compressors is possible.

Thus, according to the present invention, the oil can flow among the plurality of compressors, thereby preventing damage of the compressors and also improving product reliability.

DETAILED DESCRIPTION OF THE INVENTION

In a multi-type water cooled air conditioner, an indoor unit and an outdoor unit are separately installed, and indoor units are installed respectively in an indoor space to condition the indoor space. Here, the indoor unit and the outdoor unit are connected using a refrigerant pipe. Refrigerant serving as working fluid moves between the indoor unit and the outdoor unit through the refrigerant pipe to condition the indoor spaces.

Meanwhile, in a single unit water cooled air conditioner, an indoor unit and an outdoor unit are not separately installed but are integrated in one body. Also, the indoor spaces and the air conditioner may be connected by ducts. Accordingly, the conditioned air and air of the indoor space flow along this duct to condition the indoor spaces.

Hereinafter, embodiments of a multi-type water cooled air conditioner composed as described above will be described with reference to drawings.

FIG. 1is a schematic view illustrating a construction of an air conditioner according to a preferred embodiment of the present invention.

In a multi-type water cooled air conditioner according to the present invention, indoor units100provided within a building are separately installed in a plurality of indoor spaces and an outdoor unit200connected by the plurality of indoor units and pipes is installed in another space separated from the indoor spaces where the indoor units100are installed.

The indoor units100configured to be suitable for the indoor spaces are installed in each of the indoor spaces to condition the indoor spaces. That is, the indoor unit100may be embodied in a variety of types such as a standing unit, a wall-mounted unit, a ceiling-mounted unit, etc., and is selectively installed according to a user's needs. The indoor unit100communicates with the outdoor unit200through a refrigerant pipe300. Accordingly, the refrigerant pipe300guides refrigerant flow between the indoor unit100and the outdoor unit200.

Meanwhile, a cooling tower C cooling water is installed on a roof of the building where the water cooled air conditioner according to the present invention is installed. The cooling tower C cools water by directly contacting the water with air. That is, when the water contacts cool air, a portion of the water is evaporated, thereby dropping the water temperature by absorbing heat required for evaporation from the surrounding air.

The water cooled within the cooling tower C is guided by a water supply pipe420and then provided to the outdoor unit200. The water supply pipe420is generally made of a cylindrical pipe. Also, in the cooling tower C, there is installed a water return pipe440for guiding water, such that water that is heat exchanged with the refrigerant inside the outdoor unit200flows into the cooling tower C. Accordingly, the water cooled in the cooling tower C is guided by the water supply pipe420to flow into the outdoor unit200and the water heat exchanged with the refrigerant inside the outdoor unit200is guided by the water return pipe440to flow into the cooling tower C. Then, the water is again cooled in the cooling tower C to again flow into the outdoor unit200through the water supply pipe420, and this procedure is repeated.

A water supply pump (not shown) is further installed in the water supply pipe420or the water return pipe440to forcefully recycle water between the cooling tower C and the outdoor unit200through the water supply pipe420and the water return pipe440.

A first heat exchanger120, which conditions air in the indoor spaces where the indoor unit100is installed by intaking the air in the indoor spaces and performing heat exchanging between the air and the refrigerant, is installed inside the indoor unit100. The refrigerant serving as working fluid flows within the first heat exchanger120and exchanges heat with outside air.

An expansion valve140is provided in an entry of the first heat exchanger120. The expansion valve140decompresses pressure of the refrigerant by expanding the refrigerant passing through the expansion valve140.

The refrigerant pipe300for guiding refrigerant flow is connected between the indoor unit100and the outdoor unit200. The refrigerant pipe300is divided such that the refrigerant is guided into each of indoor units100.

Referring toFIGS. 1 and 2, the constitution of the outdoor unit200will be described in detail.

When examining a multi-type water cooled air conditioner outdoor unit200with reference to the accompanying drawings, the outdoor unit200is connected to the first heat exchanger120of the indoor unit100by the refrigerant pipe300, and a construction of the outdoor unit200has an approximate external shape that is hexahedral.

The outdoor unit200is coupled to a front panel201forming a frontal exterior, a left panel202forming a left exterior, a right panel203forming a right exterior, a rear panel204forming a rear exterior, an upper panel205forming an upper exterior, and a base206forming a bottom exterior, respectively, to form an overall exterior of the outdoor unit200.

Thus, the outdoor unit200forms an inner space having a predetermined size, and a plurality of components for conditioning air of the indoor spaces are installed in the inner space.

The front panel201includes a front upper panel201′ installed at the upper portion and a front lower panel201″ installed at a lower portion of the front upper panel201′. The front panel201is divided into the upper panel201′ and the lower panel201″ so as to easily service the inner components.

Also, the front panel201and the rear panel204are formed in a shape equivalent to each other. Accordingly, the front panel201and the rear panel204can be positionally switched. Also, the left panel202and the right panel203are formed in a shape equivalent to each other, thereby also being positionally switchable.

Therefore, the front panel201and the rear panel204, and the left panel202and the right panel203are formed in a shape equivalent to each other, thereby improving assemblability of the outdoor unit200and panel manufacturability to increase production yield.

The base206forming the bottom exterior of the outdoor unit200is formed in a square plate shape having a predetermined thickness, and a base support206′ is formed in a transverse direction at a front end portion and a rear end portion of the bottom of the base206.

A fork hole206″ is formed at the base support206′ such that a fork of a forklift can be passed therethrough. The bottom of the base206is separated from a ground by a predetermined interval such that moving and transporting the outdoor unit200can be easily performed.

Meanwhile, each of the panels forming an outward appearance of the outdoor unit200is formed in an approximately square plate shape having a predetermined thickness, and each of the panels is coupled to and supported by the frame210.

The frame210is a component forming a framework of the outdoor unit200and includes longitudinal frames212extended in an upper direction from each of the edges of an upper surface of the base206and transverse frame214coupled to upper end portions of the longitudinal frames212to connect the upper end portions.

The longitudinal frames212are lengthily formed in an upper and lower direction as described inFIG. 2, and each of the panels contacts and is coupled to the longitudinal frames212.

A second heat exchanger220is installed on the upper surface of the base206such that refrigerant serving as working fluid is heat exchanged with water. The second heat exchanger220has a rectangular hexahedral shape extending in a vertical direction. A plurality of sheet metals is formed within the second heat exchanger220such that the sheet metals have a predetermined interval therebetween. The refrigerant and the water are heat exchanged while flowing against each other through spaces among the plurality of sheet metals.

For example, if the refrigerant serving as the working fluid flows from an upper portion to a lower portion at a space formed at the front of the spaces formed among the plurality of sheet metals provided within the second heat exchanger220, the water flows from a lower portion to an upper portion in a space adjacent to where the refrigerant flows, and the refrigerant flows from an upper portion to a lower portion in a subsequently adjacent space. Accordingly, the refrigerant and the water flow in an opposite direction to allow heat exchange to occur between the refrigerant and the water by heat transmitted through the sheet metals.

A water supply outlet221, which is a passage where water is supplied into the inner space of the second heat exchanger220is protruded frontward at a frontal, lower left side portion thereof. The water supply outlet221has a round pipe shape having a predetermined diameter, and an inner space of the water supply outlet221communicates with the inner space of the second heat exchanger220.

A water return inlet222, which is a passage where water that has exchanged heat with the refrigerant in the inner space of the second heat exchanger220flows into the outside of the second heat exchanger220, is formed at a front upper portion, that is an upper portion of the water supply outlet221of the second heat exchanger220. Preferably, the water return inlet222is formed in a shape identical to the water supply outlet221.

The water supply outlet221and the water return inlet222are connected to the water supply pipe420and the water return pipe440, respectively.

A refrigerant inlet223and refrigerant outlet224, which are passages where the refrigerant serving as the working fluid flows into the inner space of the second heat exchanger220and is discharged into an outer space of the second heat exchanger220, are formed at one side (left when viewed inFIG. 1) of the water supply outlet221and the water return inlet222, respectively. The refrigerant inlet223is formed at a left side of the water return inlet222, that is a frontal upper left portion, and the refrigerant outlet224is formed at a left side of the water supply outlet221, that is the frontal lower left portion of the second heat exchanger220. Preferably, the refrigerant inlet222and the refrigerant outlet224are formed in a shape identical to the water supply outlet221and the water return inlet222, respectively.

A compressor230compressing the refrigerant serving as the working fluid into a high pressure and temperature is installed at a right side of the second heat exchanger220. The compressor230has a cylindrical shape having a predetermined height and is provided in a pair. Thus, a high pressure type scroll inverter compressor231that operates according to load capacity and compresses refrigerant is installed on the left, and a constant velocity compressor232that operates at constant velocity and compresses refrigerant is installed on the right.

The pair of compressors230functions selectively according to the load of the indoor space. That is, when the load is low, the inverter compressor231is operated, and when the sole operation of the inverter compressor231cannot handle an increase in load, the constant velocity compressor232is operated. Of course, only the constant velocity compressor232can be operated through a user setting. Likewise, even when the inverter compressor231cannot handle a load, the inverter compressor231can be set to not operate.

A high pressure type scroll compressor for compressing refrigerant to a high pressure is used as the compressor230due to its lower noise level and smaller size.

An accumulator240is provided at one side of the compressor230. The accumulator240is cylindrical in shape with a predetermined diameter and filters refrigerant in a liquid state from refrigerant flowing into the compressor230such that refrigerant in a gaseous state flows into the compressor230.

When refrigerant which is not vaporized into gas and remains in a liquid state from refrigerant flowing from the outdoor unit100flows into the inner space of the compressor230, load is increased in the compressor230that compresses the refrigerant to a gaseous state of a high temperature and a high pressure to cause damage to the compressor230.

Therefore, the refrigerant flowing into the inner space of the compressor230passes through the accumulator240to separate the refrigerant in the gaseous state from the refrigerant of the liquid state so that only refrigerant of the gaseous state flows into the inner space of the compressor230to compress the refrigerant to the high temperature and pressure.

The refrigerant remaining in the liquid state from the refrigerant flowing into the accumulator240is stored at a lower portion of the accumulator240because of its heavier weight relative to the refrigerant in the gaseous state, and only the refrigerant of the gaseous state, which is in a higher position than that of the liquid state flows into the compressor230.

An oil separator241for separating oil included in the refrigerant discharged from the compressor230is provided at an outlet of the compressor230. The oil separator241has a cylindrical shape with a predetermined diameter and separates the oil included in the refrigerant, which is compressed in the inner space of the compressor230, and discharged from the compressor230.

Oil for cooling heat generated from friction during the operation of the compressor230is provided within the compressor230and a part of the oil is mixed with the refrigerant and discharged from the compressor230. Accordingly, the oil included in the refrigerant discharged from the compressor230is separated into oil and refrigerant by passing through the oil separator241, and the separated oil is again returned into the inner space of the compressor230.

The oil separator241includes a first oil separator242for separating oil included in the refrigerant discharged from the inverter compressor231and a second oil separator243for separating oil included in the refrigerant discharged from the constant velocity compressor232.

An oil separator check valve244preventing backward flow is further included at an outlet of the oil separator241. The oil separator check valve244prevents backflow of the compressed refrigerant into the inner space of the compressor230, which does not operate when only one of the constant velocity compressor232or the inverter compressor231operates.

An oil return opening250is provided between the constant velocity compressor232and the inverter compressor231such that the oil of the constant velocity compressor232and the inverter compressor231are equally received. The oil return opening250refills oil through another compressor230or the oil separator241before an oil shortage occurs in any one compressor230, thereby preventing damage of the compressors230through a lack of oil.

The oil return opening250includes oil return pipes251and254, which guide oil separated by the oil separator241to return into the same compressor230where the corresponding oil was discharged and return uniformly to oil pipes252and255divided from the oil return pipes to guide oil into another compressor230, which has not discharged the oil.

The pair of oil return pipes251and254includes a first oil return pipe251and a second oil return pipe254. The first oil return pipe251guides oil separated from the first oil separator242for separating the oil included in the refrigerant discharged from the inverter compressor231to again return into the inverter compressor231. The second oil return pipe254guides oil separated from the second oil separator243for separating the oil included in the refrigerant discharged from the constant velocity compressor232to again return into the constant velocity compressor232.

Also, the pair of pipes for uniform distribution of return oil252and255includes a first pipe for uniform distribution of return oil252and a second pipe for uniform distribution of return oil255. The first pipe for uniform distribution of return oil252guides oil flowing along the first oil return pipe251from the first oil separator242to flow into the constant velocity compressor232. The second pipe for uniform distribution of oil255guides oil flowing along the second oil return pipe254from the second oil separator243to flow into the inverter compressor231.

The first pipe for uniform distribution of return oil252is divided from the first oil return pipe251, and the second pipe for uniform distribution of return oil255is divided from the second oil return pipe254. That is, one end of the first pipe for uniform distribution of return oil252is communicated with the first oil return pipe251, and another end is communicated with the inlet of the constant velocity compressor232. Also, one end of the second oil return pipe254is communicated with the second oil separator243, and another end is communicated with the inlet of the constant velocity compressor232.

For a further detailed explanation, the oil included in the refrigerant exchanged from the inverter compressor231is separated from the refrigerant by passing through the first oil separator242, and the oil separated from the refrigerant flows along the first oil return pipe251. The oil flowing within the first oil return pipe251is recycled into the inverter compressor231through the inlet of the inverter compressor231, and a part of the oil is guided by the first pipe for uniform distribution of return oil252to flow into the constant velocity compressor232.

Also, the oil included in the refrigerant exchanged from the constant velocity compressor232is separated from the refrigerant by passing through the second oil separator243, and the oil separated from the refrigerant flows along the second oil return pipe254. The oil flowing along the second oil return pipe254is recycled into the first pipe for uniform distribution of return oil252through the inlet of the constant velocity compressor232, and a part of the oil is guided by the inverter compressor231to flow into the inverter compressor231.

A first return valve253controlling the flow of oil by selectively opening and closing the first pipe for uniform distribution of return oil252is installed in the first pipe for uniform distribution of return oil252, and a second return valve256controlling the flow of oil by selectively opening and closing the second return uniform oil pipe255is installed in the second return uniform oil pipe256.

The first return valve253selectively opens and closes the first pipe for uniform distribution of return oil252according to the load capacity of the inverter compressor231. The first return valve253is an electronic valve that can control the amount that it opens. Therefore, the flow volume of the oil is controlled according to the operating capacity of the inverter compressor231. Also, the second return valve256is an electronic valve that controls the amount that it opens.

A pipe for uniform distribution of oil260for guiding oil flow when the operation of the compressor230is stopped is installed between the inverter compressor231and the constant velocity compressor232. The pipe for uniform distribution of oil260includes a first pipe for uniform distribution of oil261and a second pipe for uniform distribution of oil263. The first pipe for uniform distribution of oil261guides oil received within the inverter compressor231to flow into the constant velocity compressor232through the inlet thereof. The second pipe for uniform distribution of oil263guides oil received within the constant velocity compressor232to flow into the inverter compressor231through the inlet thereof.

A first uniform oil valve262controlling oil flow by selectively opening and closing the first pipe for uniform distribution of oil261is installed in the first pipe for uniform distribution of oil261, and a second uniform oil valve264controlling oil flow by selectively opening and closing the second pipe for uniform distribution of oil263is installed in the second pipe for uniform distribution of oil263. Thus, the oil flowing through the first pipe for uniform distribution of oil261and the second pipe for uniform distribution of oil263is controlled by the second uniform oil valve264, and the amount of oil flow can also be controlled.

Surplus oil discharged from oil received in the individual inner space of the first pipe for uniform distribution of oil261and the constant velocity compressor263can flow into another compressor because the oil is guided by the first pipe for uniform distribution of oil261and the second pipe for uniform distribution of oil263.

The oil separator241is communicated with a main refrigerant valve270through the pipes. The main valve270is a four-way valve. The four-way valve reverses the flow direction of the refrigerant according to an operation mode of the air conditioner. Each of the ports is respectively connected to the second heat exchanger220, the first heat exchanger120and the accumulator240. Thus, the refrigerant discharged from the constant velocity compressor232and the inverter compressor231flows into the main refrigerant valve270.

Meanwhile, a hot gas pipe272in which a portion of the refrigerant flowing into the main refrigerant valve270can be directly injected into the accumulator240is provided between the oil separator241and the main refrigerant valve270.

The hot gas pipe272can directly supply high pressure refrigerant discharged from the compressor230to the accumulator240when a pressure rise of low pressure refrigerant flowing into the accumulator240is required during operation of the air conditioner. A hot gas valve274serving as a bypass valve is installed in the hot gas pipe272to open and close the hot gas pipe272.

An overcooler280is provided at one side of the compressor230. The overcooler280is installed at a predetermined position of the refrigerant pipe300connected to the second heat exchanger220and the first heat exchanger120and is an overcooling means for further cooling refrigerant flowing into the indoor unit100through the second heat exchanger220.

Hereinafter, the flow of oil through the oil return opening will be described in detail.

Referring toFIG. 3, oil flow will be described in a state where only the inverter compressor231is operated.

Here, refrigerant compressed to a high temperature and a high pressure in the inverter compressor231flows into the first oil separator242, and the refrigerant includes a part of oil.

The first oil separator242separates oil from the refrigerant, which is discharged during operation of the inverter compressor231, and the separated oil is guided through the first oil return pipe251. The oil guided by the first oil return pipe251flows into the inverter compressor231through the inlet of the inverter compressor231.

Here, the first return valve253installed in the first pipe for uniform distribution of return oil252divided from the first oil return pipe251is closed. Thus, the first pipe for uniform distribution of return oil252is shielded.

As such, when only the inverter compressor231is operated, the oil discharged from the inverter compressor231is separated from the refrigerant in the first oil separator242and then flows along the first oil return pipe251to flow back into the inverter compressor231. That is, when only the inverter compressor231is operated, the oil discharged from the inverter compressor231flows back into the inverter compressor231, thereby preventing a shortage of oil.

Referring toFIG. 4, oil flow will be described in a state in which only the constant velocity compressor232is operated.

The oil included in high temperature and pressure refrigerant discharged from the constant velocity compressor232is separated from the refrigerant in the second oil separator243and guided by the second oil return pipe254communicated with the second oil separator243. The oil guided by the second oil return pipe254flows back into the constant velocity compressor232through the inlet of the constant velocity compressor232.

Here, the second return valve256installed in the second pipe for uniform distribution of return oil255divided from the second oil return pipe254is closed. Thus, the second pipe for uniform distribution of return oil255is shielded.

As such, when only the constant velocity compressor232is operated, the oil discharged from the constant velocity compressor232is separated from the refrigerant in the second oil separator243and then flows along the second oil return pipe254to again flow into the constant velocity compressor232. That is, when only the constant velocity compressor232is operated, the oil discharged from the inverter compressor231flows back into the constant velocity compressor232, thereby preventing the oil shortage in the constant velocity compressor232.

Hereinafter, referring toFIG. 5, oil flow will be described in a state in which the inverter compressor231and the constant velocity compressor232are operated at the same time when a required load capacity exceeds the capacity of the inverter compressor231.

When the inverter compressor231and the constant velocity compressor232are operated at the same time, the oil included in the refrigerant discharged from the inverter compressor231is separated from the refrigerant through the first oil separator242and then flows along the first oil return pipe251. The oil included in the refrigerant discharged from the constant velocity compressor232is separated from the refrigerant through the second oil separator243and then flows along the second oil return pipe254.

The oil flowing along the first oil return pipe251flows into the inlet of the inverter compressor231, and a portion of the oil flowing along the first oil return pipe251flows into the first pipe for uniform distribution of return oil252divided from the first oil return pipe251and flows into the inlet of the constant velocity compressor232. That is, the oil flows into the constant velocity compressor232through the inverter compressor252because the first return valve253is opened to open the first pipe for uniform distribution of return oil252. Thus, a portion of the oil discharged from the inverter compressor231is returned to the inverter compressor231, and another portion of the oil flows into the constant velocity compressor232.

Also, the oil flowing along the second oil return pipe254flows into the inlet of the constant velocity compressor232, and a portion of the oil flowing along the second oil return pipe254flows into the second pipe for uniform distribution of return oil255divided from the second oil return pipe254and flows into the inlet of the inverter compressor231. The second return valve256is opened to open the second pipe for uniform distribution of return oil255. Thus, the oil flows into the inverter compressor231through the second pipe for uniform distribution of return oil255.

Therefore, when the inverter compressor231and the constant velocity compressor232are operated at the same time, the oil discharged from the inverter compressor231is returned into the inverter compressor231, and simultaneously, a portion of the oil flows into the constant velocity compressor232. And, the oil discharged from the constant velocity compressor232is returned into the constant velocity compressor232, and simultaneously, a portion of the oil flows into the inverter compressor231.

Here, the first uniform oil valve262and the second uniform oil valve264installed in the first pipe for uniform distribution of oil261and the second pipe for uniform distribution of oil263, respectively, are not operated.

Also, the first return valve253and the second return valve256can control an amount of the oil flowing into the first pipe for uniform distribution of return oil252and the second pipe for uniform distribution of return oil255according to a load capacities of the inverter compressor231and the constant velocity compressor232by controlling of the amount by which the valve is opened.

Referring toFIG. 6, a flow of oil will be described in a state in which the operation of the compressor230is stopped. That is, oil flow through the first pipe for uniform distribution of oil261and the second pipe for uniform distribution of oil263will be described in a state in which the operation of the compressor230is stopped.

When the operation of a pair of compressors230is stopped, the first return valve253installed in the first pipe for uniform distribution of return oil252and the second return valve256installed in the second pipe for uniform distribution of return oil255are closed. Accordingly, the first pipe for uniform distribution of return oil252and the second pipe for uniform distribution of return oil255are shielded.

Meanwhile, here, the first uniform oil valve262installed in the first pipe for uniform distribution of oil261and the second uniform oil valve264installed in the second pipe for uniform distribution of oil263are opened. Accordingly, the first pipe for uniform distribution of oil261and the second pipe for uniform distribution of oil263are opened.

Thus, the oil received in the inverter compressor231is guided by the pipe for uniform distribution of oil261to flow into the inlet of the constant velocity compressor232, and the oil received within the constant velocity compressor232is guided by the second pipe for uniform distribution of oil263to flow into the inlet of the inverter compressor231.

Thus, the oil received in the inverter compressor231and the constant velocity compressor232through the first pipe for uniform distribution of oil261and the second pipe for uniform distribution of oil263can flow together. Therefore, the oil pressures within each of the pair of compressors230are equal.

By repeatedly performing such an operation, the oil more rapidly flows into each of the compressors230and can be selectively supplied according to an amount of oil required for each of the compressor230, thereby preventing damage due to an oil shortage in the compressor230. That is, oil flow among a plurality of compressors230is possible, and also, oil discharged from a compressor of one side can directly flow into a compressor of another side, thereby effectively preventing compressor damage due to the oil shortage.

Hereinafter, an operation of a water cooled air conditioner as described above will be described with reference toFIG. 1.

The operation of a multi-type water cooled air conditioner in heating mode to heat an indoor space will be described below.

A user connects an external power supply for operating the air conditioner. When the external power is supplied, the compressor230is operated by the power supply.

When the compressor230is operated, refrigerant is changed to a gaseous state with a high temperature and a high pressure through the operation of the compressor230. The refrigerant changed to the gaseous state with the high temperature and pressure flows into the oil separator241. The refrigerant separated in the oil separator241flows into the main refrigerant valve270to pass through the main refrigerant valve270.

The refrigerant passing through the main refrigerant valve270flows along a pipe connected to one port among ports of the main refrigerant valve270to flow into the first heat exchanger120installed in an inner space of the indoor unit100. The refrigerant flowing into the first heat exchanger120exchanges heat with air for conditioning air when the air for the air conditioning suctioned into the inner space of the indoor unit100passes through the first heat exchanger120.

The air of the indoor space, which is heat exchanged with high temperature, and pressurized refrigerant in the first heat exchanger120is heat exchanged to a high temperature and re-injected into the indoor space, thereby heating the indoor space.

The refrigerant passing through the first heat exchanger120is heat exchanged with the air for conditioning the air, and phase-transforms into a liquid state with low temperature and pressure. The refrigerant phase-transformed into the liquid state with the low temperature and pressure passes through the expansion valve140installed in the inner space of the indoor unit100to flow along the refrigerant pipe300, and then passes through the overcooler280to flow into the second heat exchanger220.

The refrigerant flowing into the second heat exchanger220is heat exchanged with water to phase-transform the refrigerant into a gaseous state with a high temperature and a low pressure, and the refrigerant phase-transformed into the gaseous state with the high temperature and the low pressure flows into the main refrigerant valve270through a pipe connected to one port formed at the main refrigerant valve270.

The refrigerant flowing into the main refrigerant valve270flows into the accumulator240and flows back into the compressor230. The refrigerant flowing into the compressor230is compressed within the compressor230to complete one cycle of operation.

The operation of cooling an indoor space according to refrigerant flow when a multi-type water cooled air conditioner is operated in a cooling mode will be described below.

The compressor230is operated by supplying an external power supply. When the compressor230is operated, refrigerant is changed to a gaseous state with a high temperature and a high pressure through the operation of the compressor230. The refrigerant changed to the gaseous state with the high temperature and pressure flows into the oil separator241. The refrigerant separated in the oil separator241flows into the main refrigerant valve270to pass through the main refrigerant valve270.

The refrigerant passing through the main refrigerant valve270flows along a pipe connected to one port among ports of the main refrigerant valve270to flow into an inner space of the second heat exchanger220. The refrigerant flowing into the second heat exchanger220is heat exchanged with water supplied from the cooling tower C in the inner space of the second heat exchanger220.

The refrigerant heat exchanged in the inner space of the second heat exchanger220is phase-transformed into a liquid state with a low temperature and a high pressure, and the refrigerant phase-transformed into the liquid state with the low temperature and the high pressure is over-cooled by passing through the overcooler280. The over-cooled refrigerant transforms to a liquid state with low temperature and pressure by passing through the expansion valve140installed in the inner space of the indoor unit100. The refrigerant having the liquid state of the low temperature and pressure is heat exchanged with air injected from inside the indoor unit100by passing through the first heat exchanger120.

Air of the inner space and the a low temperature refrigerant flowing inside of the first heat exchanger120exchange heat in the first heat exchanger120. The air of the inner space, which exchanges heat with the low temperature refrigerant has a low temperature and the low temperature air is re-injected into the inner space, thereby cooling the inner space.

The refrigerant heat exchanged with the air of the inner space is phase-transformed into a gas state with high temperature and pressure, and the phase-transformed refrigerant is guided by the refrigerant pipe300to pass through the main refrigerant valve270through one port of the main refrigerant valve270. The refrigerant passing through the main refrigerant valve270is separated into liquid refrigerant and gas refrigerant by passing through the accumulator240.

The gas refrigerant separated through the accumulator240flows into the inner space of the compressor230and is again compressed into a gaseous state with high temperature and pressure to complete one cycle of operation.