JP2664702B2 - Air conditioner - Google Patents

Description

The present invention relates to an improvement of a multi-type air conditioner including one outdoor unit and a plurality of indoor units.

(Prior Art) Generally, as this type of air conditioner, there is an air conditioner equipped with a heat pump refrigeration cycle as shown in FIG.

In FIG. 7, A is an outdoor unit, B is a branch unit, and C, D and E are indoor units. Outdoor unit A is 2
Equipped with two variable capacity compressors 1 and 2, and the compressors 1 and 2 are check valves
They are connected in parallel via 3 and 4, respectively. Then, the compressors 1 and 2, the four-way valve 5, the outdoor heat exchanger 6, the heating expansion valve 7
And a cooling cycle forming check valve 8 in parallel, a liquid tank 9, electric flow regulating valves 11, 21, 31, cooling expansion valves 12, 22,
A parallel body of 32 and check valves 13, 23, 33 for forming a heating cycle, indoor heat exchangers 14, 24, 34, gas side on-off valves (electromagnetic on-off valves) 15, 25,
35, the accumulator 10 and the like are sequentially communicated to form a heat pump refrigeration cycle.

The cooling expansion valves 12, 22, and 32 are temperature-sensitive cylinders 12a, 22 respectively.
a, 32a, and these temperature-sensitive cylinders are connected to the indoor heat exchangers 14, 2
It is attached to each of 4,34 gas side refrigerant pipes.

That is, the indoor heat exchangers 14, 24, and 34 are arranged in parallel, and a cooling cycle is formed by flowing a refrigerant in a direction of a solid line arrow in a cooling operation, and a switching operation of the four-way valve 5 is performed in a heating operation. The refrigerant is caused to flow in the direction of the dotted arrow to form a heating cycle.

In such an air conditioner, in order to satisfy the required capacity of each indoor unit, the number of operating compressors 1 and 2 and the capacity thereof are controlled, and the opening degrees of the flow control valves 11, 21, 31 are respectively controlled. Thus, the flow rate of the refrigerant to each indoor heat exchanger is adjusted.

The expansion valves 12, 22, and 32 maintain a constant degree of superheat of the refrigerant in each indoor heat exchanger irrespective of a change in the refrigerant flow rate, thereby performing stable and efficient operation.

Therefore, for example, during the cooling operation, when the required capacity of each indoor unit increases, the capacity of the compressor 1 increases, and the compressor 2 in addition to the compressor 1 starts. When the required capacity of each indoor unit is reduced from this state, the capacity of the compressor 2 is reduced, or the operation of the compressor 2 is stopped and only the compressor 1 is operated.

However, in such an air conditioner, the oil discharge amount and the oil return amount of the compressors 1 and 2 do not completely match.
Over time, the amount of lubricating oil in one compressor increased,
The amount of lubricating oil in the other compressor decreases, and an imbalance in the amount of oil occurs between the two, making stable operation difficult.

Moreover, when the oil level of the lubricating oil falls below the critical oil level (operable level), the supply of the lubricating oil to the lubricating unit is cut off, and the compressors 1 and 2 are damaged.

Therefore, in order to eliminate the imbalance in the amount of oil in each of the compressors 1 and 2, it is necessary to connect the compressors 1 and 2 with an equalizing pipe so that the lubricating oil moves from the larger oil amount to the smaller oil amount. There is something.

However, since the capacity of each of the compressors 1 and 2 is not completely the same, the pressure loss of the suction pipe of the compressor having a relatively large capacity becomes large, and the pressure inside the compressor case becomes small. This tendency is remarkable when the compressors 1 and 2 have different capacities.

As a result, the refrigerant gas moves through the oil equalizing pipe from the compressor on the side with the higher internal pressure to the compressor on the side with the lower internal pressure, and accordingly, the lubricating oil also moves in the same direction.

When the amount of oil returned from the compressor with the higher pressure in the case is greater than the amount of oil discharged, lubricating oil at a level equal to or higher than the oil equalizing pipe moves to the compressor with the lower pressure in the case through the oil equalizing pipe. The oil level inside the machine is equal at the leveling pipe position. Conversely, when the oil return amount is smaller than the oil discharge amount, the oil level in the compressor on the side where the pressure in the case is high decreases with the passage of time, and eventually falls below the limit oil level. In this case, the lubricating oil in the compressor with the lower pressure in the case is prevented from moving to the compressor with the higher pressure in the case due to the pressure difference in the case between the compressors.

Therefore, it is conceivable to make the oil level in each of the compressors 1 and 2 uniform and the pressure in the case of each of the compressors 1 and 2 by increasing the diameter of the oil equalizing pipe. ing.

However, when a large-diameter oil equalizing pipe is used, vibration generated in one compressor is easily transmitted to the other compressor via the oil equalizing pipe, and resonance occurs depending on a combination of operating frequency ranges of both compressors 1 and 2. And the like, which causes compressor vibration and compressor noise, and also may cause damage to the oil equalizing pipe.

(Problems to be Solved by the Invention) When the compressors 1 and 2 are connected by an oil equalizing pipe,
Due to the pressure difference in the cases 1 and 2, the lubricating oil in the case moves from the compressor with the higher pressure in the case to the compressor with the lower pressure in the case through the oil equalizing pipe, and the In addition to the problem that the oil level in the case becomes uneven, the oil level in each compressor 1 and 2 is made uniform and the pressure in the case of each compressor 1 and 2 is If the compressor is made uniform, the vibration generated in one compressor will be easily transmitted to the other compressor via the oil equalization pipe, and depending on the combination of the operating frequency ranges of both compressors 1 and 2, resonance may occur. As a result, there is a problem that compressor vibration and compressor noise are caused, and there is a possibility that the oil equalizing pipe may be damaged.

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain an oil equalizing effect between compressors without using a large-diameter oil equalizing pipe. It is an object of the present invention to provide an air conditioner that can avoid compressor noise, secure sufficient strength of an oil equalizing pipe to enhance reliability, and further improve the oil equalizing effect.

[Structure of the Invention] (Means for Solving the Problems) The invention of claim 1 includes an outdoor unit having two variable capacity compressors, and a plurality of indoor units. In an air conditioner that controls the number of operating compressors and the operating frequency of each compressor, an oil equalizing pipe provided between the compressors and the compressors are driven at substantially the same operating frequency during simultaneous operation of the compressors. Normal operating means, and a first oil leveling operation in which one of the two compressors is moved up and down by a fixed time relatively to the other by a fixed time, and the other operating frequency is kept at a fixed operating frequency. And an oil equalizing operation means for repeating the first oil equalizing operation and the second oil equalizing operation in a state where both the compressors are exchanged.

The invention according to claim 2 includes an outdoor unit having two variable capacity compressors, and a plurality of indoor units, and the air conditioner controls the number of operating and the operating frequency of each of the compressors according to the required capacity of the indoor units. An oil equalizing pipe provided between each of the compressors, and a first for driving both of the compressors at substantially the same operating frequency during simultaneous operation of the two compressors.
Means for controlling the total capacity of the two compressors by combining the driving state of the two compressors and the second driving state of driving the compressor with a predetermined frequency difference between the operating frequencies of the two compressors. Then, the two compressors are driven at substantially the same operating frequency, and thereafter, the operating frequency of one of the two compressors is increased and decreased by a fixed time relative to the other, and the other operating frequency is set to a constant operating frequency. First oil leveling means for maintaining at a frequency;
A second oil equalizing operation means for performing the first oil equalizing operation in a state where the two compressors are exchanged.

(Operation) In the invention of claim 1, during the normal operation, both compressors are driven at substantially the same operation frequency during the simultaneous operation of the two variable capacity compressors. Further, at the time of oil equalizing operation, a first oil equalizing operation in which one of the two compressors is moved up and down relative to the other by a fixed time relatively, and the other operating frequency is held at a constant operating frequency. By repeating the second oil equalizing operation in which the first oil equalizing operation is performed with both compressors replaced,
An oil equalizing effect between the compressors is obtained without using a large-diameter oil equalizing pipe, and compressor vibration and compressor noise are avoided.

According to the invention of claim 2, during the simultaneous operation of the two variable capacity compressors, there is a predetermined frequency difference between the first drive state in which both compressors are driven at substantially the same operation frequency and the operation frequency of both compressors. By controlling in combination with the second drive state in which the compressors are driven in a synchronized state, the resolution of the overall capacity of both compressors is increased, and both compressors are driven at substantially the same operation frequency during oil equalization operation. Then, the operating frequency of one of the two compressors is increased and decreased by a fixed time relative to the other, and the other operating frequency is maintained at a constant operating frequency, so that the two compressors are in the second operation frequency. The first oil equalizing operation and the second oil equalizing operation are repeated at regular intervals to prevent the oil equalizing operation from being started in the drive state, and the first and second oil equalizing operations are repeated. Sometimes the operating frequency of both compressors is raised and lowered relatively, By efficiently circulating the circulating oil in the compressor case of the compressor through the oil equalizing pipe, the oil equalizing effect between each compressor can be obtained without using a large-diameter oil equalizing pipe, and the compressor vibration and compressor noise are reduced. This is to avoid it.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 6, the same parts as those in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, an oil separator 41 is provided on a refrigerant discharge side pipe of the compressor 1, and an oil bypass pipe 42 extends from the oil separator 41 to a refrigerant suction side pipe of the compressor 1.
Is provided.

Further, an oil separator 43 is provided in the refrigerant discharge side pipe of the compressor 2, and an oil bypass pipe 44 is provided from the oil separator 43 to the refrigerant suction side pipe of the compressor 2.

Further, as shown in FIG. 2, the cases of the compressors 1 and 2 are connected to each other by an oil equalizing pipe 45. In this case, the compressors 1 and 2 are installed on the same surface. In the compressors 1 and 2, the optimal reference oil level and the minimum allowable limit oil level of the lubricating oil stored in the cases are predetermined, and are set at positions at almost the same height as the reference oil level. Attach oil equalizing pipe 45 to

FIG. 3 shows a control circuit of the refrigeration cycle. In FIG. 3, reference numeral 50 denotes an outdoor control unit mounted on the outdoor unit A. The outdoor control unit 50 includes a microcomputer and its peripheral circuits, and is externally connected to inverter circuits 51 and 52. The inverter circuits 51 and 52 rectify the voltage of the AC power supply 53, convert it to an AC voltage of a predetermined frequency by switching according to the specification of the outdoor control unit 50, and supply the AC voltage as drive power to the compressor motors 1M and 2M, respectively. Things.

Reference numeral 60 denotes a multi-control unit mounted on the branch unit B. The multi-control unit 60 is composed of a microcomputer and its peripheral circuits, and is externally provided with flow control valves 11, 21, 31.
And on-off valves 15, 25 and 35, respectively.

Further, 70, 80, and 90 are indoor control units mounted on the indoor units C, D, and E, respectively. These indoor control units 70, 80, 90
Consists of a microcomputer and its peripheral circuits,
External operation control units 71, 81, 91 and indoor temperature sensors 72, 82,
92 are connected respectively.

Then, the indoor control unit 70, 80, 90 the frequency setting signal f _1, f
It adapted to forward the multi-controller 60 as a _2, f ₃ required capabilities. Multi-control unit 60 is adapted to transfer each of the indoor unit from the frequency setting signal transferred C, D, the total sum of the required capacity of E, a frequency setting signal f ₀ corresponding thereto to the outdoor control unit 50 .

 Next, the operation of the above configuration will be described.

Now, it is assumed that all the indoor units are performing the cooling operation.

At this time, the indoor control unit 70 of the indoor units C, calculates the difference between a defined set temperature at the detected temperature and the driving operation unit 71 of the indoor temperature sensor 72, a frequency setting signal f ₁ corresponding to the temperature difference It is transferred to the multi control unit 60 as the required cooling capacity. Similarly, the indoor control units 80 and 90 of the indoor units D and E also use the frequency control signals f ₂ and f ₃ as the required cooling capacity,
Transfer to 0.

Further, the multi control unit 60 obtains the sum of the required cooling capacity of each of the indoor units C, D, E based on the transferred frequency setting signal. Then, to transfer the frequency setting signal f ₀ corresponding to the sum determined in the outdoor control unit 50. This outdoor control unit
Each indoor unit on the basis of the 50 frequency setting signal f ₀ which is transferred in C, D, the total sum of the requested cooling performance of E, the number of operating units and operating frequency (inverter circuit of the compressor 1 in accordance with the sum 51, 52) are controlled. In this case, the outdoor control unit 50 shifts from the operation of one compressor 1 to the operation of two compressors 1 and 2 as the sum of the required cooling capacities increases.

During operation of the compressor 1, most of the lubricating oil contained in the discharged refrigerant is collected by the oil separator 41 and returned to the compressor 1 through the oil bypass pipe 42. Similarly,
During operation of the compressor 2, most of the lubricating oil contained in the discharged refrigerant is collected by the oil separator 43 and returned to the compressor 2 through the oil bypass pipe 44. The refrigerant that has not been recovered goes through a refrigeration cycle and returns to the compressors 1 and 2.

On the other hand, the multi-control unit 60 controls the opening of the refrigerant flow control valves 11, 21, and 31 in accordance with the frequency setting signals from the indoor units C, D, and E. The optimal amount of refrigerant corresponding to the required cooling capacity is supplied to each indoor heat exchanger 14, 24, 34.
Flows into. Further, the degree of superheat of the refrigerant in each of the indoor heat exchangers 14, 24, 34 is controlled to be constant by the expansion valves 12, 22, 32.

Further, the outdoor control unit 50 operates between the first driving state in which both compressors 1 and 2 are driven at substantially the same operating frequency and the operating frequency of both compressors 1 and 2 during the operation of the two compressors 1 and 2. The total capacity of both compressors 1 and 2 is controlled in combination with the second drive state in which the compressors are driven with a predetermined frequency difference. For example, the compressor 1 is driven in a state where the operating frequency Fa of the other compressor 1 is Fa ₀ and the operating frequency Fb of the other compressor 2 is Fb ₀ (Fa ₀ = Fb ₀ ) (first driving state). In this state, if the sum of the required capacities from the indoor units C, D, and E increases in this state, first, the operating frequency Fa of the compressor 1 is increased to Fa ₀ + ΔF, and the operating frequency of the compressor 2 is increased. It is driven respectively in a state of being held and Fb to Fb ₀ (second driving state). Next, after driving for a predetermined time in this state, the operating frequency of the compressor 2
Fb is increased to Fb ₀ + ΔF, and the operating frequency Fa of the compressor 1 is set to F
a ₀ + ΔF, the operating frequency Fb of the compressor 2 is driven for a predetermined time at Fb ₀ + ΔF (first driving state). Further, similarly, the operating frequency Fa of the compressor 1 is increased to Fa ₀ + 2ΔF, and the compressor 1 is driven for a predetermined time while the operating frequency Fb of the compressor 2 is maintained at Fb ₀ + ΔF (second driving state). The operating frequency Fb of the compressor 2 is raised to Fb ₀ + 2ΔF, the operating frequency Fa of the compressor 1 is driven at Fa ₀ + 2ΔF, and the operating frequency Fb of the compressor 2 is driven at Fb ₀ + 2ΔF for a predetermined time (first driving state). ). Then, while the first drive state and the second drive state are alternately repeated in this manner, the compressors 1, 2 are brought to a state corresponding to the sum of the required capacity from the indoor units C, D, E.
Control your overall ability. Therefore, in this case, when the total capacity of both compressors 1 and 2 is changed, the operating frequency F of both compressors 1 and 2 is changed.
Since the resolution of the total capacity of both compressors 1 and 2 can be improved compared to the case where a and Fb are increased and decreased simultaneously, it is possible to respond to the change in the sum of the required capacity from each indoor unit C, D, E side. The total capacity of both compressors 1 and 2 can be controlled finely, and the operating efficiency and comfort of both compressors 1 and 2 can be improved.

Further, the outdoor control unit 50 performs an oil leveling operation for equalizing the amount of lubricating oil in the compressor cases of the two compressors 1 and 2 while the two compressors 1 and 2 are operating.

The oil equalizing operation of the compressors 1 and 2 will be described with reference to FIGS. FIG. 4 shows a change state of the operating frequency Fa of one of the compressors 1 during the oil equalizing operation (shown by a solid line in the figure) and a change state of the operating frequency Fb of the other compressor 2 (shown by a dotted line in the figure). ) Are shown.

Now, the compressors 1 and 2 are driven in a normal operation state (a state in which the first drive state and the second drive state are alternately repeated), and both compressors 1 and 2 are operated in the second drive state. Suppose For example, as shown in FIG.
Fa is Fa ₁ , and the operating frequency Fb of the compressor 2 is Fb ₀ (Fa ₀ ≒ Fb ₀ , Fa
₁ = Fa ₀ + ΔF> Fb ₀ ). In this state, the first oil equalizing operation is performed when a predetermined time T has elapsed.

The first is when the oil equalizing operation operating frequency Fa of the compressor 1 of the operating frequency Fa is lowered from Fa ₁ to Fa ₀ by both compressors 1, 2 substantially the same operating frequency (the compressor 1 at the beginning Fa ₀ , Compressor 2
Is driven for a predetermined time t at Fb ₀ ). Thereafter, the operating frequency Fa of one of the compressors 1 is reduced by n step frequencies. In this case, the operating frequency Fb of the other compressor 2
Is kept as Fb ₀ . Therefore, the pressure Pa in the direction of the operating frequency Fa ₂ of the compressor 1 is lower than the operating frequency Fb ₀ of the compressor 2 in the case, the compressor 1 case
Becomes higher than the pressure Pb in the case of the compressor 2, so that the lubricating oil in the case of the compressor 1 on the high pressure side flows into the case of the compressor 2 on the low pressure side gradually through the oil equalizing pipe 45 together with the refrigerant. As shown in FIG. 5, the oil level in the case of the compressor 1 gradually decreases, and the oil level in the case of the compressor 2 gradually increases. In this case, the lower limit level of the oil level in the case of the compressor 1 is up to the lower surface position of the oil equalizing pipe 45.

Also, the operating frequency Fa of the compressor 1 after a lapse of t ₁ hour while being lowered to Fa _2, the operating frequency Fa of the compressor 1 to n steps the frequency increases from Fa ₀ at this point. In this case, the operating frequency Fb of the compressor 2 is maintained in a state of Fb _0. Therefore, in this case, the operating frequency of the compressor 1
Fa ₃ is higher than the operating frequency Fb ₀ of the compressor 2, and the pressure Pa in the case of the compressor 1 is equal to the pressure Pa in the case of the compressor 2.
Since the pressure becomes lower than Pb, the lubricating oil in the case of the compressor 2 on the high pressure side gradually flows into the case of the compressor 1 on the low pressure side through the oil equalizing pipe 45 together with the refrigerant, and as shown in FIG. 2, the oil level in the case of the compressor 1 gradually rises.

Further, when the operating frequency Fa of the compressor 1 has been raised to Fa ₃ and the time t _{2 has} elapsed, the first oil equalizing operation is terminated at this time, and the operating frequency Fa of the compressor ₁ is returned to Fa _1. Return to normal operation. Therefore, in the normal operation area after the end of the first oil leveling operation, the oil level in the case of the compressor 1 is maintained higher than the oil level in the case of the compressor 2 as shown in FIG. Is done. Then, when a certain time T elapses in the normal operation state, the oil equalizing operation is performed in a state where both compressors 1 and 2 are exchanged (second oil equalizing operation).

The second is when the oil equalizing operation operating frequency Fa of the compressor 1 of the operating frequency Fa is lowered from Fa ₁ to Fa ₀ by both compressors 1, 2 substantially the same operating frequency (the compressor 1 at the beginning Fa ₀ , Compressor 2
Is driven for a predetermined time t at Fb ₀ ). Thereafter, the operating frequency Fb of the compressor 2 is decreased by n step frequencies. In this case, operating frequency Fa of the compressor 1 is held in a state of Fa _0. Therefore, in this case, the compressor 2
Since the operating frequency Fb ₂ of the compressor 1 is lower than the operating frequency Fa ₀ of the compressor 1 and the pressure Pb in the case of the compressor 2 is higher than the pressure Pa in the case of the compressor 1, Machine 2
Lubricating oil in the case gradually flows into the case of the compressor 1 on the low pressure side through the oil equalizing pipe 45 together with the refrigerant, and the oil level in the case of the compressor 2 gradually decreases as shown in FIG. The oil level in the case of the compressor 1 gradually rises.

Also, the operating frequency Fb of the compressor 2 when the elapsed t ₁ hour while being reduced in Fb _2, the operating frequency Fb of the compressor 2 to n step frequency increases from Fb ₀ at this point. In this case, operating frequency Fa of the compressor 1 is held in a state of Fa _0. Therefore, in this case, the operating frequency of the compressor 2
Fb ₃ is higher than the operating frequency Fa ₀ of the compressor 1, and the pressure Pb in the case of the compressor 2 is the pressure in the case of the compressor 1.
Therefore, the lubricating oil in the case of the high-pressure side compressor 1 gradually flows into the case of the low-pressure side compressor 2 together with the refrigerant through the oil equalizing pipe 45, as shown in FIG. The oil level in the case of the compressor 2 gradually rises while the oil level in the case 1 falls gradually.

Further, after a lapse of t ₂ hours in a state of increasing the operating frequency Fb of the compressor 2 to Fb _3, returning the operating frequency Fb of the compressor 2 at this point Fb _0, the operating frequency Fa of the compressor 1 to Fa ₁ And return to normal operation. Therefore, in the normal operation range after the end of the second oil leveling operation, the oil level in the case of the compressor 2 is maintained higher than the oil level in the case of the compressor 1 as shown in FIG. Is done. After that, normal operation and the first
And the second oil equalizing operation are alternately repeated at regular intervals.

Thus, in the above configuration, the compressors 1 and 2
During the stand operation, the operating frequency Fa of one of the two compressors 1 and 2 is increased and decreased by a fixed time relative to the operating frequency Fb of the compressor 2 while the operating frequency of the compressor 2 is changed. Fb
Repeated alternately first oil equalizing operation and second oil equalizing operation is performed a first oil equalizing operation in a state in which interchanged both compressors 1, 2 for holding a predetermined cycle at a constant operating frequency Fb ₀ Since the oil leveling operation is performed, the oil level levels of the compressors 1 and 2 in the normal operation region after the end of the first oil leveling operation and the compressor 1 in the normal operation region after the end of the second oil leveling operation The level of the oil level can be alternately switched between the two oil level levels. Therefore, the compressor 1,
The level of the oil level 2 can be prevented from being extremely biased toward one side, and the oil levels of the compressors 1 and 2 can be made uniform.

Therefore, stable operation can always be performed, and oil rising and locking of the compressors 1 and 2 can be prevented, so that damage to the compressors 1 and 2 can be prevented.

Furthermore, the oil equalizing pipe 45 does not need a large diameter pipe,
Since a small diameter one can be used, sufficient strength can be ensured, compressor vibration and compressor noise can be avoided, and the cost is also advantageous.

Also, since the oil equalizing effect can be obtained without installing expensive cost type float regulators and oil level sensors in the compressors 1 and 2, the overall configuration can be simplified, and cost reduction can be achieved. Can be planned.

Further, during the oil equalizing operation of the compressors 1 and 2, an operation of lowering the operating frequency Fa ₀ (or Fb ₀ ) by n steps from the operating frequency Fa ₀ (or Fb ₀ ) and the operating frequency Fa ₀ (or Fb ₀ ) during the normal operation.
And the operation for raising the n-step frequency is performed alternately.
When the frequency of the inverter circuit 51 (or 52) is increased by n steps above ₀ (or Fb ₀ ), the output current of the inverter circuit 51 (or 52) is determined to be abnormal, and the current release that reduces the output frequency of the inverter circuit 51 (or 52) by a certain value operates. Even if the oil leveling operation at the time of the frequency rise becomes impossible, the oil leveling operation must be performed surely at the time of the operation frequency lower by n steps than the operating frequency Fa ₀ (or Fb ₀ ) during the normal operation. Can be. Therefore, at least one oil leveling operation can be performed within the time T to obtain an oil leveling effect.

Further, even when the operating frequencies Fa and Fb of both of the compressors 1 and 2 reach the maximum value, it is ensured that the operating frequency is reduced by n step frequency from the operating frequency Fa ₀ (or Fb ₀ ) during the normal operation. Since the oil operation can be performed, at least one oil equalizing operation can be performed within the time T to obtain an oil equalizing effect.

Furthermore, even when the operating frequencies Fa and Fb of both the compressors 1 and 2 have reached the minimum value, it is ensured that the operating frequency is increased by n steps from the operating frequency Fa ₀ (or Fb ₀ ) during normal operation. Since the oil operation can be performed, at least one oil equalizing operation can be performed within the time T to obtain an oil equalizing effect.

Further, during the simultaneous operation of both compressors 1 and 2, the first driving state in which both compressors 1 and 2 are driven at substantially the same operating frequency (Fa ₀ ≒ Fb ₀ ) and the operating frequency of both compressors 1 and 2 Since the control is performed in combination with the second driving state in which the motor is driven with a predetermined frequency difference ΔF therebetween, the resolution of the total capacity of both compressors 1 and 2 can be increased.

Further, during the oil equalizing operation, both compressors 1 and 2 are driven at substantially the same operating frequency (Fa ₀ ≒ Fb ₀ ) before starting the oil equalizing operation,
Then, since the oil equalizing operation of both compressors 1 and 2 is started, it is possible to prevent the oil equalizing operation from being started with both compressors 1 and 2 remaining in the second drive state. it can. Therefore, the oil equalizing operation is started in a state where both compressors 1 and 2 remain in the second drive state, and it is ensured that the difference ΔF between the operating frequencies of both compressors 1 and 2 during the oil equalizing operation becomes uneven. Even if the oil leveling operation is started with both compressors 1 and 2 kept in the second driving state, a uniform oil leveling effect can be obtained.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the case where the number of the indoor units is three has been described, but the case where the number of the indoor units is two or more or more can be similarly performed. Further, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] According to the invention of claim 1, an oil equalizing pipe is provided between the two variable capacity compressors, and both the compressors are driven at substantially the same operation frequency during the simultaneous operation of the two compressors. Means, a first oil equalizing operation in which one operating frequency of both compressors is increased and decreased by a fixed time relative to the other, and the other operating frequency is maintained at a constant operating frequency; And a second oil equalizing operation that repeats the second oil equalizing operation in which the first oil equalizing operation is performed in a state where the oil is replaced, so that an oil equalizing effect between the compressors can be achieved without using a large-diameter oil equalizing pipe. You can get
Compressor vibration and compressor noise can be avoided, and sufficient strength of the oil equalizing pipe can be ensured to enhance reliability. In addition, the oil equalizing effect can be further improved.

According to the second aspect of the present invention, an oil equalizing pipe is provided between the compressors, and during the simultaneous operation of the two compressors, the first drive state in which both compressors are driven at substantially the same operation frequency and the operation of both compressors Means for controlling the total capacity of both compressors in combination with the second drive state, which is driven with a predetermined frequency difference between the frequencies, initially driving both compressors at substantially the same operating frequency A first oil equalizing operation means and both compressors for raising and lowering the operating frequency of one of the two compressors by a fixed time relative to the other, and maintaining the other operating frequency at a constant operating frequency; The second oil equalizing operation means for performing the first oil equalizing operation in a state where the oil is replaced is provided, so that an oil equalizing effect between the compressors can be obtained without using a large-diameter oil equalizing pipe. Avoid machine vibration and compressor noise, and ensure that the oil equalizing pipe has sufficient strength. And to be able to increase the reliability,
In addition, it is possible to further improve the oil leveling effect.

[Brief description of the drawings]

1 to 6 show one embodiment of the present invention.
FIG. 1 is an overall schematic diagram showing a refrigeration cycle in an air conditioner, FIG. 2 is a schematic diagram showing a relationship between each compressor and an oil equalizing pipe, and FIG. 3 is a schematic diagram showing a configuration of a control circuit of the refrigeration cycle. FIG. 4 is a characteristic diagram showing a change state of the operating frequency during the oil equalizing operation, and FIG. 5 is an oil diagram when the operating frequency of the first compressor is lower than the operating frequency of the second compressor. FIG. 6 is a schematic configuration diagram showing a surface change state, FIG. 6 is a schematic configuration diagram showing an oil level change state when the operation frequency of the first compressor is higher than the operation frequency of the second compressor, and FIG. It is the whole schematic block diagram which shows the refrigeration cycle in the conventional air conditioner. A: Outdoor unit, B: Branch unit, C, D, E ...
Indoor unit, 1,2… Variable capacity compressor, 45… Equalizer oil pipe, 50… Outdoor control unit, 60 …… Multi control unit, 70,80,90
.... Indoor control unit.

Claims (2)

(57) [Claims] An air conditioner comprising: an outdoor unit having two variable capacity compressors; and a plurality of indoor units, wherein the number of operating compressors and the operating frequency of each of the compressors are controlled in accordance with the required capacity of the indoor units. In the oil equalizing pipe provided between the compressors, during the simultaneous operation of the two compressors, a normal operation means for driving both compressors at substantially the same operating frequency, and one of the two compressors The first oil leveling operation, in which the operating frequency is increased and decreased by a constant time relative to the other, and the other operating frequency is maintained at a constant operating frequency, and the first oil leveling operation in a state where both compressors are exchanged. An air conditioner comprising: oil equalizing operation means for repeating a second oil equalizing operation for performing an oil operation. 2. An air conditioner comprising an outdoor unit having two variable capacity compressors and a plurality of indoor units, wherein the number of operating compressors and the operating frequency of each of the compressors are controlled according to the required capacity of the indoor units. An oil equalizing pipe provided between the compressors, a first driving state in which the compressors are driven at substantially the same operating frequency during simultaneous operation of the compressors, and an operating frequency of the compressors. Means for controlling the total capacity of the two compressors in combination with a second driving state in which the two compressors are driven with a predetermined frequency difference therebetween, and firstly, the two compressors are operated at substantially the same operating frequency. Driving, and thereafter, the first oil equalizing operation means for raising and lowering the operating frequency of one of the two compressors by a constant time relative to the other, and maintaining the other operating frequency at a constant operating frequency; , The two compressors were replaced An air conditioner characterized by comprising a second oil equalizing operation means for performing the first oil equalizing operation in state.