Patent Application
20080209924
This application claims the benefit of Korean Patent Application No. 10-2007-0021118, filed on Mar. 2, 2007, which is hereby incorporated by reference as if fully set forth herein.
1. Field
The present application discloses an air conditioner including a plurality of compressors which is configured to supply balanced amounts of oil to the compressors, and a control method thereof.
2. Background
Generally, an air conditioner performs air conditioning using heat absorbed by or discharged from a refrigerant. The refrigerant is subjected to a refrigeration cycle of compression, condensation, expansion, and evaporation. One essential element of such an air conditioner is a compressor functioning to compress the refrigerant. The compressor is subjected to a high pressure, high temperatures, and the moving parts of the compressor may experience a high degree of friction. As a result, if the compressor is not properly lubricated, it can be easily damaged.
In order to ensure reliability of such a compressor, it is important to lubricate and cool the compressor. The lubrication and cooling is achieved by oil. The compressor should always contain a certain amount of oil.
However when the refrigerant is discharged from the compressor, after being compressed, a portion of the oil in the compressor may be mixed in with the refrigerant. As a result, the oil is discharged together with the refrigerant. As the compressor continues to operate, the amount of oil contained in the compressor decreases gradually. In conventional compressors, an oil separator is arranged in a discharge line connected to an outlet of the compressor. The separator separates the oil from the refrigerant and returns the separated oil to the compressor.
Where a plurality of compressors are used together in a single air conditioning system, typically connected in parallel, and where the amounts of refrigerant discharged from the respective compressors is different due to different capacities of the compressors, the amounts of oil contained in the respective compressors may not be balanced. As a result, the compressor or compressors containing an insufficient amount of oil may be damaged. In this case, there are considerable adverse affects on the performance of the overall system.
The embodiments will be described in detail with reference to the following drawings, in which like reference numerals refer to like elements, and wherein:
Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The air conditioner shown in
The outdoor unit 1 includes a compression unit 10, a heat exchanging unit 30, and an expansion device 40. Although not shown, the indoor unit 3 includes an indoor heat exchanger and an expansion valve. The distribution unit 2 can include a refrigerant line connecting the outdoor unit 1 and indoor unit 3, and various valves, to control a refrigerant flow between the outdoor unit 1 and the indoor unit 3.
Where the air conditioner is adapted to perform both a cooling operation and a heating operation (including both a simultaneous type or a switching type), a switching valve 20 is installed in the outdoor unit 1. The switching valve 20 switches the flow direction of a refrigerant discharged from the compression unit 10.
The air conditioner includes oil separation units 100 respectively connected to a plurality of compressors constituting the compression unit 10. Each oil separation unit 100 separates oil mixed with a refrigerant discharged from the associated compressor, and returns the separated oil to the associated compressor.
In
As shown in
In detail, the compression unit 10 includes a first compressor 10a, a second compressor 10b, and a third compressor 10c. Of course, any number of compressors could be used, as long as the number of compressors is plural. Also, the plural compressors may comprise constant speed compressors or variable speed compressors. Alternatively, the plural compressors may comprise a combination of variable speed compressors and constant speed compressors.
Discharge lines 11a, 11b, and 11c are connected to respective outlets of the compressors 10a, 10b, and 10c. Compressed refrigerant flow through the discharge lines 11a, 11b, and 11c after it is discharged from the compressors 10a, 10b, and 10c.
The oil separation unit includes a first oil separator 101, a second oil separator 102, and a third oil separator 103. The first oil separator 101 is connected to the first discharge line 11a, to communicate with the first compressor 10a. The second oil separator 102 is connected to the second discharge line 11b, to communicate with the second compressor 10b. The third oil separator 103 is connected to the third discharge line 11c, to communicate with the third compressor 10c.
The supply lines, through which refrigerant flows from the accumulator 50 to the respective compressors includes a first supply line 12a connected to the first compressor 10a, a second supply line 12b connected to the second compressor 10b, and a third supply line 12c connected to the third compressor 10c.
The oil separators 101, 102, and 103 separate oil mixed with the refrigerant discharged from the compressors 10a, 10b, and 10c. The separated oil is then returned to the compressors via the supply lines 12a, 12b, and 12c, so as to return the separated oil to the compressors 10a, 10b, and 10c, respectively. The air conditioner includes recovery lines 111, 112, and 113, through which oil flows from the oil separators 101, 102, and 103 to the compressors 10a, 10b, and 10c. The recovery lines 111, 112, and 113 comprise a first recovery line 111 connected between the first oil separator 101 and the first supply line 12a, a second recovery line 112 connected between the second oil separator 102 and the second supply line 12b, and a third recovery line 113 connected between the third oil separator 103 and the third supply line 12c.
Opening/closing valves 151, 152, and 153 are arranged in the recovery lines 111, 112, and 113, to open or close the recovery lines 111, 112, and 113, and thus, to control recovery of oil to the compressors 10a, 10b, and 10c, respectively. The opening/closing valves 151, 152, and 153 comprise a first opening/closing valve 151 for controlling recovery of oil through the first recovery line 111, a second opening/closing valve 152 for controlling recovery of oil through the second recovery line 112, and a third opening/closing valve 153 for controlling recovery of oil through the third recovery line 113.
Preferably, expansion devices 141, 142, and 143 are arranged in the recovery lines 111, 112, and 113. The expansion devices act to expand (lower the pressure) oil which is being returned to the compressors 10a, 10b, and 10c. The expansion devices 141, 142, and 143 comprise a first expansion device 141 for expanding oil recovered through the first recovery line 111, a second expansion device 142 for expanding oil recovered through the second recovery line 112, and a third expansion device 143 for expanding oil recovered through the third recovery line 113.
The reason why the expansion devices 141, 142, and 143 are installed is that there is a pressure difference between the refrigerant supplied from the accumulator 50 to each of the compressors 10a, 10b, and 10c and the oil recovered from the associated oil separators 101, 102, or 103. The refrigerant from the accumulator 50 has a low pressure, whereas the oil separated from the compressed refrigerant has a high pressure.
The expansion devices reduce the pressure of oil flowing through the recovery lines 111, 112, and 113, and thus, reducing the pressure difference between each recovery line 111, 112, or 113 and the associated return line 12a, 12b, or 12c. The pressure reduction function is also desirable because a reduction in temperature is also achieved during the expansion of the oil, and this helps to reduce an oil evaporation phenomenon to a certain degree.
The recovery lines 111, 112, and 113 are connected to a bypass line 120 such that the recovery lines 111, 112, and 113 communicate. In detail, the recovery lines 111, 112, and 113 comprise a first recovery line 111, a second recovery line 112, and a third recovery line 113 which all communicate with the bypass line 120. Accordingly, oil from the first oil separator 101 flowing through the first recovery line 111 may be sent through the bypass line 120 such that it is introduced into the second and third recovery lines 112 and 113, to thereby be recovered to the second and third compressors 10b and 10c. Thus, the oil recovered from any of the oil separators 101, 102, and 103 can be supplied, via the bypass line 120, to a compressor which contains an insufficient amount of oil.
Preferably, control valves 131 and 132 are arranged in the bypass line 120, to control oil flows among the recovery lines 111, 112, and 113. The control valves 131 and 132 comprise a first control valve 131 arranged in a portion of the bypass line 120 connecting the first and second recovery lines 111 and 112, and a second control valve 132 arranged in a portion of the bypass line 120 connecting the second and third recovery lines 112 and 113. The first control valve 131 controls an oil flow between the first recovery line 111 and the second recovery line 112. The second control valve 132 controls an oil flow between the second recovery line 112 and the third recovery line 113. For the control valves, solenoid valves may be used. Also, valves, which can adjust an opening degree thereof, may be used.
Now, a control method for the embodiment shown in
During normal operations, the controller closes the first and second control valves 131 and 132, and opens the first, second, and third opening/closing valves 151, 152, and 153, to enable the normal operation to be executed. In this state, oil separated by the first oil separator 101 is introduced into the first compressor 10a. Oil separated by the second oil separator 102 is introduced into the second compressor 10b, and oil separated by the third oil separator 103 is introduced into the third compressor 10c. As the normal operation is repeatedly executed, the amount of oil contained in each compressor may vary.
Where a plurality of compressors having different capacities are used, an oil shortage may occur in one of the compressors. Even in the case in which the compressors have similar capacities, an oil unbalance phenomenon may occur because the driving times of the compressors may be different. When an unbalance occurs, an oil balancing operation is executed in the air conditioner. In detail, the controller of the air conditioner controls the oil balancer included in the air conditioner to supply balanced amounts of oil to the compressors.
The oil balancing operation step may include step A of operating at least one compressor while stopping the remaining compressors, and a step B of controlling the oil balancer to allow oil to be supplied to the non-operating compressors. The oil balancing operation step may further include a step C of operating at least one compressor including the compressor supplied with oil, and introducing oil into the compressors, except for the operating compressor. The oil balancing operation step may include repeating steps A, B, and C for all the plural compressors.
In the following description, it is assumed that during the normal operation step, all of the first, second, and third compressors were operated, and that an oil unbalance occurred among the compressors. Of course, the oil balancing operation can be executed for a compressor which did not operate during the normal operation step.
During the balancing operation, the controller of the air conditioner operates one of the plural compressors, while stopping the remaining compressors. The controller then controls the oil balancer such that oil separated by the oil separator associated with the operating compressor is supplied to one or both of the stopped compressors. In detail, the controller operates the first compressor 10a, while stopping the second and third compressors 10b and 10c. The controller then opens the first control valve 131 and second opening/closing valve 152, while closing the second control valve 132, first opening/closing valve 151, and third opening/closing valve 153. Accordingly, oil separated by the first oil separator 101 is introduced into the stopped second compressor 10b via the bypass line 120 and second recovery line 112. In this case, the controller operates the first compressor 10a for a first predetermined time.
After the operation of the first compressor 10a is completed, the controller maintains the first and third compressors 10a and 10c in a stopped state. Simultaneously, the controller operates the second compressor 10b, which has been supplied with oil in the above procedure. Thereafter, the controller opens the second control valve 132 and third opening/closing valve 153, while closing the first control valve 131, first opening/closing valve 151, and second opening/closing valve 152. Accordingly, oil separated by the second oil separator 102 is introduced into the stopped third compressor 10c via the bypass line 120 and third recovery line 113. In this case, the controller operates the second compressor 10b for a second predetermined time.
The controller sequentially executes the above-described procedures for all compressors. Here, sequential operations of the compressors mean that all compressors operate sequentially in a given order. In detail, in the embodiment shown in
The controller may execute the above-described procedures once for all compressors. If necessary, the controller may repeat the above-described procedures several times. After completion of the above-described procedures, the amounts of oil supplied to the compressors are balanced due to the following reasons.
Since different amounts of oil are contained in the compressors before the oil balancing operation, the ratio of oil mixed with a refrigerant in one compressor during operation of the compressor is different from those in the remaining compressors. For example, in a compressor containing a large amount of oil, a large amount of oil is mixed with a refrigerant. As a result, when that compressor is operated, a large amount of oil is discharged from the compressor, and this relatively large amount of oil is introduced into another one of the compressors. On the other hand, in a compressor containing a small amount of oil, a small amount of oil is mixed with a refrigerant. As a result, when that compressor operates, only a small amount of oil will be transferred over to another compressor. When all compressors operate sequentially, as explained above, the amounts of oil contained in the compressors tends to balanced out.
If sensors are installed in the respective compressors, to sense the amounts of oil contained in the respective compressors, the air conditioner according to the first embodiment can operate in the following manner. First, the controller determines which one of the compressors 10a, 10b, and 10c, contains an insufficient amount of oil, based on sensing data from the sensors. If it is determined that the second compressor 10b has an insufficient amount of oil, the controller then operates the first compressor 10a, while stopping the second and third compressors 10b and 10c. Thereafter, the controller opens the first control valve 131 and second opening/closing valve 152, while closing the second control valve 132, first opening/closing valve 151, and third opening/closing valve 153. Accordingly, oil separated by the first oil separator 101 is introduced into the second compressor 10b via the bypass line 120 and second recovery line 112. Thus, the second compressor 10b is replenished with the oil.
If it is determined that the third compressor 10c has an insufficient amount of oil, the controller will then execute a control operation to introduce oil separated by the first oil separator 101 into the third compressor 10c, and thus, to replenish the third compressor 10c with the oil. Similarly, if it is determined that the first compressor 10a has an insufficient amount of oil, the controller will then execute a control operation to supply oil only to the first compressor 10a.
Hereinafter, a procedure, in which an oil balancing operation is carried out in a second embodiment of the air conditioner, will be described with reference to
In the air conditioner according to the second embodiment, the first and second control valves 131 and 132 are eliminated. That is, the first, second, and third recovery lines 111, 112, and 113 are always in communication by the bypass line 120. Of course, the control method according to this embodiment is also applicable to the case in which the first and second control valves 131 and 132 are used, as long as the first and second control valves 131 and 132 are maintained in an opened state. In the following description, it is assumed that, during the normal operation step, all the first, second, and third compressors were operated, and an oil unbalance occurred among the compressors.
For the oil balancing operation in the air conditioner according to the second embodiment, the controller first operates the first and second compressors 10a and 10b, while stopping the third compressor 10c. The controller then closes the first and second opening/closing valves 151 and 152, while opening the third opening/closing valve 153. Accordingly, oil separated by each of the first and second oil separators 101 and 102 passes through the bypass line 120, and is then introduced into the third compressor 10c via the third recovery line 113. In this case, the controller operates the first and second compressors 10a and 10b for a first predetermined time.
After the operations of the first and second compressors 10a and 10b are completed, the controller operates the second and third compressors 10b and 10c, while maintaining the first compressor 10a in a stopped state. The controller closes the second and third opening/closing valves 152 and 153, while opening the first opening/closing valve 151. Accordingly, oil separated by each of the second and third oil separators 102 and 103 passes through the bypass line 120, and is then introduced into the first compressor 10a via the first recovery line 111. In this case, the controller operates the second and third compressors 10b and 10c for a second predetermined time.
After the operations of the second and third compressors 10b and 10c are completed, the controller operates the third and first compressors 10c and 10a, while maintaining the second compressor 10b in a stopped state. The controller closes the third and first opening/closing valves 153 and 151, while opening the second opening/closing valve 152. Accordingly, oil separated by each of the third and first oil separators 103 and 101 passes through to the bypass line 120, and is then introduced into the second compressor 10b via the second recovery line 112. In this case, the controller operates the third and first compressors 10c and 10a for a third predetermined time.
The controller may execute the above-described procedures once. If necessary, the controller may repeat the above-described procedures several times. After completion of the above-described oil balancing operation, the controller opens the first, second, and third opening/closing valves 151, 152, and 153, to enable a normal operation to be executed. In the normal operation, oil emerging from the first oil separator 101, oil emerging from the second oil separator 102, and oil emerging from the third oil separator 103 will be mixed in the bypass line 120.
Of course, where the control valves 131 and 132 are used, they are opened in the oil balancing operation, but are closed in the normal operation.
If sensors are installed in the respective compressors, to sense the amounts of oil contained in the respective compressors, the controller will not operate a compressor which contains an insufficient amount of oil. Instead, the controller will operate at least one of the remaining compressors and control the opening/closing valves to supply oil to the compressor containing an insufficient amount of oil.
For example, when the first compressor 10a contains an insufficient amount of oil, the controller does not operate the first compressor 10a, but operates the second compressor 10b, which contains a sufficient amount of oil. Thereafter, the controller closes the second and third opening/closing valves 152 and 153, while opening the first opening/closing valve 151.
Accordingly, oil separated by the oil separator 102 associated with the operating second compressor 10b is introduced into the first compressor 10a via the first recovery line 111. In this case, the sensor of the first compressor 10a senses the amount of oil in the first compressor 10a, to determine the operating time of the second compressor 10b.
Hereinafter, an oil balancing operation carried out in a third embodiment will be described with reference to
The controller first operates the first compressor 10a, while stopping the second and third compressors 10b and 10c. The controller then closes the second and third control valves 132 and 133, while opening the first control valve 131. Accordingly, oil separated by the first oil separator 101 is partially introduced into the first compressor 10a via the first recovery line 111. The remaining portion of the separated oil is introduced into the second compressor 10b via the bypass line 120. In this case, the controller operates the first compressor 10a for a first predetermined time.
After the operation of the first compressor 10a is completed, the controller operates the second compressor 10b, while maintaining the third and first compressors 10c and 10a in a stopped state. The controller closes the third and first control valves 133 and 131, while opening the second control valve 132. Accordingly, oil separated by the second oil separator 102 is partially introduced into the second compressor 10b via the second recovery line 112. The remaining portion of the separated oil is introduced into the third compressor 10c via the bypass line 120. In this case, the controller operates the second compressor 10b for a second predetermined time.
After the operation of the second compressor 10b is completed, the controller operates the third compressor 10c, while maintaining the first and second compressors 10a and 10c in a stopped state. The controller closes the first and second control valves 131 and 132, while opening the third control valve 133. Accordingly, oil separated by the third oil separator 103 is partially introduced into the third compressor 10c via the third recovery line 113. The remaining portion of the separated oil is introduced into the first compressor 10a via the second bypass line 121. In this case, the controller operates the third compressor 10c for a third predetermined time.
The controller may execute the above-described procedures once. If necessary, the controller may repeat the above-described procedures several times. After completion of the above-described oil balancing operation, the controller executes a control operation for a normal operation of the air conditioner. That is, the controller closes the first, second, and third control valves 131, 132, and 133, and operates at least one of the first, second, and third compressors 10a, 10b, and 10c, which is required for the normal operation. During normal operations, oil emerging from the first oil separator 101 is introduced into the first compressor 10a. Oil emerging from the second oil separator 102 is introduced into the second compressor 10b, and oil emerging from the third oil separator 103 is introduced into the third compressor 10c.
If sensors are installed in the respective compressors, to sense the amounts of oil contained in the respective compressors, the controller will not operate the compressor which contains an insufficient amount of oil, but will operate at least one of the remaining compressors and control the control valves to supply oil to the compressor containing an insufficient amount of oil.
For example, when the first compressor 10a contains an insufficient amount of oil, the controller does not operate the first compressor 10a, but operates the second compressor 10b, which contains a sufficient amount of oil. The controller closes the second and third control valves 132 and 133, while opening the first control valve 131.
Accordingly, oil separated by the second oil separator 102 is partially introduced into the first compressor 10a via the bypass line 120 and first recovery line 111. The remaining portion of the separated oil is introduced into the second compressor 10b. In this case, the sensor of the first compressor 10a senses the amount of oil in the first compressor 10a during the operation of the second compressor 10b, to determine the operating time of the second compressor 10b.
Hereinafter, a fourth embodiment of the air conditioner will be described with reference to
The controller first operates one of the two compressors. For example, as shown in
After the operation of the first compressor 10a is completed, the controller maintains the first compressor 10a in a stopped state, while operating the second compressor 10b. Thereafter, the controller closes the second opening/closing valve 152, while opening the first opening/closing valve 151 and control valve 131. Accordingly, oil separated by the second oil separator 102 is introduced into the first compressor 10a via the bypass line 120 and first recovery line 111. In this case, the controller operates the second compressor 10a for a second predetermined time.
When the oil balancing operation is completed, the controller closes the control valve 131, while opening the first and second opening/closing valves 151 and 152, to enable a normal operation to be executed.
If sensors are installed in respective compressors, to sense the amounts of oil contained in respective compressors, the air conditioner according to the fourth embodiment can operate in the following manner. First, if it is determined that the first compressor 10a contains an insufficient amount of oil, based on sensing data from the sensors, the controller stops the first compressor 10a, and operates the second compressor 10b. The controller opens the first opening/closing valve 151, closes the second opening/closing valve 152, and opens the control valve 131. As the second compressor 10b operates, oil separated by the second oil separator 102 is introduced into the first compressor 10a via the bypass line 120 and first recovery line 111. Thus, the second compressor 10b is replenished with oil.
On the other hand, if it is determined that the second compressor 10b contains an insufficient amount of oil, the controller stops the second compressor 10b, and operates the first compressor 10a. The controller opens the second opening/closing valve 152 and control valve 131, and closes the first opening/closing valve 151. As the first compressor 10a operates, oil separated by the first oil separator 101 is introduced into the second compressor 10b via the bypass line 120 and second recovery line 112. Thus, the second compressor 10b is replenished with oil.
When the oil balancing operation is completed, the controller closes the control valve 131, while opening the first and second opening/closing valves 151 and 152, to enable a normal operation to be executed.
Hereinafter, a fifth embodiment of the air conditioner will be described with reference to
The controller first operates the first compressor 10a, while stopping the second and third compressors 10b and 10c. The controller then closes the first and third opening/closing valves 151 and 153, while opening the second opening/closing valve 152. Accordingly, oil separated by the oil separator 200 is introduced into the second compressor 10b via the second recovery line 112. In this case, the controller operates the first compressor 10a for a first predetermined time.
After the operation of the first compressor 10a is completed, the controller operates the second compressor 10b, while maintaining the third and first compressors 10c and 11a in a stopped state. Thereafter, the controller closes the second and first opening/closing valves 152 and 151, while opening the third opening/closing valve 153. Accordingly, oil separated by the oil separator 200 is introduced into the third compressor 10c via the third recovery line 113. In this case, the controller operates the second compressor 10b for a second predetermined time.
After the operation of the second compressor 10b is completed, the controller operates the third compressor 10c, while maintaining the first and second compressors 10a and 10b in a stopped state. Thereafter, the controller closes the third and second opening/closing valves 153 and 152, while opening the first opening/closing valve 151. Accordingly, oil separated by the oil separator 200 is introduced into the first compressor 10a via the first recovery line 111. In this case, the controller operates the third compressor 10c for a third predetermined time.
The controller may execute the above-described procedures once. If necessary, the controller may repeat the above-described procedures several times. After completion of the above-described oil balancing operation, the controller opens the first, second, and third opening/closing valves 151, 152, and 153, to enable a normal operation to be executed. In the normal operation, oil emerging from the oil separator 200 is introduced into the compressors via the first, second and third recovery lines, respectively.
Of course, if there are sensors for sensing amounts of oil contained in respective compressors, the controller will not operate the compressor which contains an insufficient amount of oil, but will operate at least one of the remaining compressors and control the opening/closing valves to supply oil to the compressor containing an insufficient amount of oil.
For example, when the first compressor 10a contains an insufficient amount of oil, the controller does not operate the first compressor 10a, but operates the second compressor 10b, which contains a sufficient amount of oil. The controller closes the second and third opening/closing valves 152 and 153, while opening the first opening/closing valve 151. Accordingly, oil separated by the oil separator 200 is introduced into the first compressor 10a via the first recovery line 111. In this case, the sensor of the first compressor 10a senses the amount of oil in the first compressor 10a, to determine the operating time of the second compressor 10b.
As apparent from the above description, the air conditioners and control methods thereof can effectively perform oil balancing for a plurality of compressors, to achieve an enhancement in the operation reliability of the compressors. In particular, during the oil balancing operations, all the compressors, which were operated in a normal operation, are sequentially operated. Thus, oil balancing can be effectively achieved.
In the oil balancing operations, at least a portion of the oil separated from an oil-refrigerant mixture discharged from the compressor which operates during the oil balancing operation is supplied to at least one of the stopped compressors. Accordingly, oil balancing can be effectively achieved.
An air conditioning system as described above can include both high-pressure type and low-pressure type compressors, connected in series, and are independently controlled. Accordingly, there is an advantage in that it is possible to easily adjust the compression ratio of the compression system. Also, the high-pressure type and low-pressure type compressors are connected using an oil connecting line. Accordingly, it is possible to equally distribute oil to the high-pressure type and low-pressure type compressors, through a simple method using the hydrostatic pressure of oil.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
Although a number of illustrative embodiments have been described, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, variations and modifications are possible in the component parts and/or arrangements of the subject combinations which would fall within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0021118 | Mar 2007 | KR | national |
