JPH0363468A - Operation controller for air conditioner - Google Patents

Abstract

PURPOSE:To recover oil collecting on a discharge line effectively by communicating the discharge-line side gas branch pipes and absorption-line side gas branch pipes of each utilization-side heat exchanger and conducting the operation for bypassing one part of a discharged refrigerator to the suction line side, on oil recovery operation. CONSTITUTION:One part of a discharged refrigerant is controlled so as to be bypassed to a suction line 32 through a branch pipe 31b in a first chamber and a branch pipe 32b in a second chamber by a discharged-oil recovery control means 101 in each indoor unit B for a fixed time on oil recovery operation. Since the refrigerant is bypassed between a high-pressure discharge line 31 and the low-pressure suction line 32 at that time, the gas refrigerator is flowed in the discharge line 31 at high speed even when the operation capacity of a compressor 1 is reduced by high and low differential pressure, thus accelerating the speed of the refrigerant in the discharge line 31 without resulting in the over-rise of high pressure due to the increase of the capacity of the compressor 1, then recovering oil collecting in the refrigerant piping, etc. of the discharge line 31.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an operation control device for an air conditioner in which the gas pipe side of each heat exchanger can be individually switched to a discharge line and a suction line. In particular, it relates to measures to improve oil recovery operation functions.

(Prior Art) Conventionally, as disclosed in JP-A-61-110859, for example, in an air conditioner in which a plurality of indoor units are connected in parallel to an outdoor unit, a discharge line, a suction line, and a liquid line are connected. The air conditioner is extended from the outdoor side to the indoor side, and the gas pipe side of the heat source side heat exchanger and each user side heat exchanger are connected alternately to the discharge line and suction line, respectively. When operating the device,
By individually switching the connection of each heat exchanger to the gas line to the discharge line or suction line depending on the operating conditions,
On each indoor side, cooling operation and heating operation are performed individually according to the indoor demand, and on the heat source side, the heat source side heat exchanger is switched to a condenser or an evaporator according to the demand of the whole room,
BACKGROUND ART Air conditioners that aim to improve the comfort and operational efficiency of air conditioning are well-known technologies.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional air conditioner, the discharge line is long and extends indoors, and the refrigerant pipe on the discharge line, that is, the discharge side connecting pipe, or the indoor Since the gas branch pipe on the discharge line side is always located in the discharge line, the following problems occur when performing oil recovery operation.

In other words, when oil accumulates on the discharge line, oil recovery is carried out by maximizing the operating capacity of the compressor in the cooling cycle and opening the valve to allow a slightly moist refrigerant to flow, as in a normal air conditioner. Even after operation, only dry gas refrigerant flows through the discharge line, so
There is a possibility that the accumulated oil may not be sufficiently recovered.

Therefore, it may be possible to return the refrigerant to the discharge line by increasing the flow rate of the refrigerant.

In that case, in order to increase the flow rate of the refrigerant, it is necessary to control the operating capacity of the compressor to be large, but if the required load of the heat exchanger is small, controlling the operating capacity of the compressor too large will cause high pressure. A new problem arises in that there is a risk of excessive rise and high pressure cut.

The present invention has been made in view of the above, and its purpose is to effectively remove oil accumulated on the discharge line by providing a means for increasing the speed of the refrigerant without causing an excessive rise in high pressure. The goal is to collect it.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention provides a solution between the gas branch pipe on the discharge line side and the gas branch pipe on the suction line side of each heat exchanger on the user side during oil recovery operation. The objective is to perform a discharge oil recovery operation in which a part of the discharged refrigerant is bypassed to the suction line side.

Specifically, the first solution is as shown in FIG.
(Dotted line area and dotted line area not included), variable capacity compressor (
1), an outdoor unit having a heat source side heat exchanger (2) and a heat source side flow rate control valve (25) whose opening degree can be adjusted) (for A>, a user side heat exchanger (5) and a user side flow rate control valve) Control valve (5
The present invention assumes an air conditioner in which a plurality of indoor units (B), . . . , having 1) are connected in parallel.

As an operation control device for the air conditioner, a discharge line (31) extending from the discharge side of the compressor (1), and a suction line (32) extending from the suction side of the compressor (1);
The liquid line (33) extending from the liquid pipe side of the heat source side heat exchanger (2) and the gas pipe side of the heat source side heat exchanger (2) are connected to the discharge line (31) and the suction line (32). an outdoor connection switching means (21) that switches to
) are branched from the gas pipe side of the discharge line (31
) and the second indoor branch pipe (32b) that communicates with the suction line (32), and the gas pipe side of the user heat exchanger (5) are connected to the first indoor branch pipe (31 b) that communicates with Indoor connection switching means (35) for switching between the indoor branch pipe (31b) and the second indoor branch pipe (32b) shall be provided.

Further, a bypass opening/closing means (36) for connecting and disconnecting the first indoor branch pipe (31 b) and the second indoor branch pipe (32 b), and a bypass opening/closing means (36) for connecting and disconnecting the first indoor branch pipe (31 b) and the second indoor branch pipe (32 b), and a bypass opening/closing means (36) for connecting and disconnecting the discharge refrigerant for a certain period of time during the oil recovery operation. discharge oil recovery control means (101) for controlling the bypass opening/closing means (36) so that a part of the oil is bypassed from the first indoor branch pipe (31b) to the suction side via the second indoor branch pipe (32b); The configuration is such that the

As shown in FIG. 1 (not including the dotted line portion), the second solution includes, in addition to the first solution, during oil recovery operation,
For a predetermined period of time after the discharge oil recovery control means (101) finishes the discharge oil recovery operation, the operating capacity of the compressor (1) is increased, and the heat source side flow control valve (25) and each user side flow control valve (51) ), and the gas pipe side of the heat source side heat exchanger (2) is connected to the discharge line (31),
The outdoor connection switching means (2) connects the gas pipe side of each user-side heat exchanger (5) to the suction line (32).
1) and an intake oil recovery control means (102) that controls the indoor connection switching means (35).

As shown in FIG. 1, in addition to the first or second solution, the third solution is a system that connects the discharge pipe and suction pipe of the compressor (1) so that the discharged refrigerant can be bypassed. A pressure bypass path (42), an opening/closing means (42a) for opening and closing the pressure equalizing bypass path (42), and a discharge pipe before the discharge oil recovery operation by the discharge pipe oil recovery control means (101) during the oil recovery operation. The above-mentioned pressure equalization bypass path (
pressure equalization control means (42) for controlling the opening/closing means (42a);
103).

(Function) With the above configuration, in the invention of claim (1), during the oil recovery operation, the discharge oil recovery control means (101) controls the discharge oil in each indoor unit (B), . A portion of the refrigerant is controlled to bypass into the suction line (32) via the first indoor branch pipe (31b) and the second indoor branch pipe (32b).

In that case, the refrigerant is bypassed between the high-pressure discharge line (31) and the low-pressure suction line (32), so even if the operating capacity of the compressor (1) is small, the discharge line ( 31), the gas refrigerant flows through the discharge line (31) at high speed, and the velocity of the refrigerant in the discharge line (31) increases without causing an excessive rise in high pressure due to an increase in the capacity of the compressor (1). (31) The oil remaining in the refrigerant pipes etc. is recovered.

In the invention of claim (2), the suction oil recovery control means (102) is operated for a predetermined period of time after the discharge oil recovery control means (101) in the invention of claim (1) finishes the discharge oil recovery operation.
), the operating capacity of the compressor (1) is increased, and the heat source side flow control valve (25) and each user side flow control valve (21),
With the opening degree of ... increased, all the user side heat exchangers (5
) functions as an evaporator, and the heat source side heat exchanger (2) functions as a condenser.Since oil recovery operation is performed in a cooling cycle, the amount of refrigerant circulated is large and the operation is a bit humid. ) etc., is collected in the compressor (1), and in addition to the effect of the invention of claim (1), the oil, etc. that remains in each part other than the discharge line (31) is recovered by the compressor (1). Oil recovery is performed throughout the main refrigerant circuit (3).

Furthermore, by combining the discharge oil recovery operation, the oil in the discharge line (31) can be removed from the suction line (31) in a short period of discharge oil recovery operation.
32) and then return it to the compressor (1) through suction oil recovery operation, which significantly improves the oil recovery effect.

In the invention of claim (3), the above claim (1) or (2)
Before the discharge oil recovery control means (101) performs the discharge oil recovery operation in the invention, the pressure equalization control means (103) equalizes the pressure in the discharge line (31) and the suction line (32), After the pressure difference between the high and low pressures has almost disappeared, the discharge oil recovery operation is started. Therefore, generation of loud switching noise due to bypass of the refrigerant between the first indoor branch pipe (31b) and the second indoor branch pipe (32b) by the bypass opening/closing means (36) is suppressed, and deterioration of the air conditioning feeling is prevented. will be done.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of an air conditioner (X) according to an embodiment of the present invention, in which a plurality of indoor units (B), (B), etc. (in the drawing) are provided for one outdoor unit (A). 3 units)
It has a so-called multi-type configuration in which two are connected.

In the above outdoor unit (A), (1) is a compressor, (
2) is an outdoor heat exchanger as a heat source side heat exchanger equipped with an outdoor fan (26), and (21) is the outdoor heat exchanger (2).
(25) is an outdoor electric expansion valve as a heat source side flow rate control valve; (43) is a receiver for storing liquid refrigerant. , (41) is an accumulator for separating liquid refrigerant in the suction refrigerant.

On the other hand, each of the indoor units (B), etc. has the same configuration, and all of them have an indoor heat exchanger ( 5) Reduce the pressure of the refrigerant during cooling operation,
It is provided with an indoor electric expansion valve (51) which is a user-side flow control valve that adjusts the refrigerant flow rate during heating operation.

Here, from the discharge side of the compressor (1), a discharge line (
31), suction lines (32) extend from the suction side, while liquid lines (33) extend from the liquid pipe side of the outdoor heat exchanger (2), and the three refrigerant pipes (3) extend from the liquid pipe side of the outdoor heat exchanger (2).
1) to (33) extend from the outdoor side to the indoor side. The above-mentioned outdoor unit (A) and each indoor unit (B), etc. are connected to the three refrigerant pipes (
31) to (33) to form a main refrigerant circuit (3) that allows heat to be transferred between the heat exchangers (2) and (5), . . . .

Next, to explain in detail the connection relationship of the refrigerant piping mentioned above,
In the outdoor unit (A), the outdoor heat exchanger (2)
The gas pipe side of is branched into a first outdoor branch pipe (22-1) communicating with the discharge line (31) and a second outdoor branch pipe (22-2) connected to the suction line (32). 1st.
The ends of the second outdoor branch pipes (22-1) and (22-2) are connected to two opposing connection boats of the four-way switching valve (21), so that the four-way switching valve (21) When switching to the broken line side in the figure, the gas pipe side of the outdoor heat exchanger (2) is connected to the suction line (32) via the second outdoor branch pipe (22-2), and as a result, the outdoor heat exchanger (2) functions as an evaporator, while when the four-way switching valve (21) switches to the solid line side in the figure, the gas pipe side of the outdoor heat exchanger (2) becomes the first outdoor branch pipe (
As a result of being connected to the discharge line (31) via 22-1), the outdoor heat exchanger (2) functions as a condenser. The other connection boat of the four-way switching valve (21) is connected to the second outdoor branch pipe (22-2) via a capillary tube (23).

On the other hand, in the indoor unit (B), the discharge line (
31), the indoor end of the suction line (32) and the liquid line (33) are connected to the first to third flow dividers (31a) to (31), respectively.
33a), while the gas pipe side of each indoor heat exchanger (5) branches into a first indoor branch pipe (31 b) and a second indoor branch pipe (32b), Branch pipe (3
1b) is connected to the first flow divider (
31a), the second indoor branch pipe (32b) is connected to the second flow divider (32a) via the second indoor on-off valve (52), and the liquid pipe (33b) of the indoor heat exchanger (5) is connected to the second indoor branch pipe (32b). )
is connected to the third flow divider (33a). That is,
The first indoor on-off valve (52) opens and the second indoor on-off valve (52) opens.
3) is closed, the gas pipe side of the indoor heat exchanger (5) is connected to the discharge line (31), and as a result, the indoor heat exchanger (
5) functions as a condenser, while the first indoor on-off valve (5) functions as a condenser.
2) is closed and the second indoor on-off valve (53) is opened, the gas pipe side of the indoor heat exchanger (5) is connected to the suction line (32), and as a result, the indoor heat exchanger (5) functions as an evaporator. It is made to work. Above 1. The second indoor on-off valves (52) and (53) separately connect the gas pipe side of the indoor heat exchanger (5) to the first indoor branch pipe (31 b) and the second indoor branch pipe (32 b). Indoor connection switching means (
35) is configured.

In addition, as described below, the above-mentioned No. 1. Second indoor on/off valve (15
) and (16) are open, the first indoor branch pipe (31 b) and the second indoor branch pipe (32 b) are connected, and a portion of the discharged refrigerant bypasses to the suction side. ing. That is, the above 1. The second indoor on-off valves (15) and (16) switch the connection on the gas pipe side of the indoor heat exchanger (5) to the discharge line (31) and the suction line (32) when they are alternately switched between open and close states. While functioning as the indoor connection switching means (35), the first indoor branch pipe (
31b) and the second indoor branch pipe (32b).

Furthermore, the device is equipped with sensors (Th
l) is an indoor liquid temperature sensor that detects the liquid refrigerant temperature of the indoor heat exchanger (5), (T h2) is an indoor gas temperature sensor that detects the gas refrigerant temperature of the indoor heat exchanger (5), and (T113) is an indoor liquid temperature sensor that detects the temperature of the liquid refrigerant of the indoor heat exchanger (5). A room temperature sensor that detects the indoor air temperature, (T h4) an outdoor liquid temperature sensor that detects the temperature of the liquid refrigerant in the outdoor heat exchanger (2), and (T h5) a sensor that detects the temperature of the gas refrigerant in the outdoor heat exchanger (2). (T he) is an outdoor air temperature sensor that detects outside air temperature, (T h7) is a compressor) (1
) Discharge pipe sensor that detects the discharge pipe temperature of (L ps)
is a low pressure sensor arranged in the suction line (32) to detect low pressure, and (Hps) is a high pressure sensor arranged in the discharge line (31) to detect high pressure.

In the air conditioner, the operating capacity of the compressor (1) and each flow control valve (
25), (51), . . . are controlled to open or close. Note that (57) is an indoor fan provided in each indoor unit (B).

During normal operation of the air conditioner (X), each indoor unit (B
), ..., when the indoor request is a cooling request, the connection by the indoor connection switching means (35) is switched to the suction line (32) side, and the refrigerant depressurized by the indoor electric expansion valve (51) is transferred indoors. It flows to evaporate in the heat exchanger (5). Further, when the indoor request is a heating request, the connection by the indoor connection switching means (35) is switched to the discharge line (31) side, and the refrigerant discharged from the compressor (1) is transferred to the indoor heat exchanger (5). It flows as if it were condensed and liquefied.

On the other hand, in the outdoor unit (A), all the indoor units (
When the overall request for B), ... is a cooling request, the four-way switching valve (21) is switched to the solid line side in the figure, and the discharged refrigerant flows to be condensed and liquefied in the outdoor heat exchanger (2), The heat exchanger (2) functions as a condenser, and all indoor units (B
), ... is a heating request, the four-way switching valve (21) is switched to the side shown by the broken line in the figure, and the refrigerant whose pressure has been reduced by the outdoor electric expansion valve (25) is transferred to the outdoor heat exchanger (2). The outdoor heat exchanger (2) functions as an evaporator. In other words, while minimizing the operating capacity of the compressor (1), each indoor unit (B),
... can be individually heated and cooled at the same time.

When a certain period of time has elapsed since the start of operation of the compressor (1) and it becomes necessary to recover oil, a control different from that described above is performed. The contents will be explained based on the flowchart of FIG. 3 and Table 1 below. In step S2, a predetermined first set time (for example, 8
An oil recovery operation timer (not shown) having a period of time (approximately 30 minutes) is set, and in step S2 it is determined whether the compressor (1) is in operation, that is, whether or not the timer count is permitted, and in step S3, The oil recovery operation timer counts only when the timer count is permitted, and the above control is performed until the oil recovery operation timer times out in step S4.

That is, as shown in the top column of Table 1 below, the opening and closing states of each of the first indoor on-off valve (52) and the second indoor on-off valve (53) are alternately turned on and off according to indoor demands. Then, while each indoor heat exchanger (5) functions as an evaporator or a condenser, the four-way switching valve (21) is switched to the solid line side or the broken line side in the figure according to the overall indoor demand, and outdoor heat exchange is performed. Vessel (2)
is made to function as a condenser or an evaporator, and its capacity is adjusted by the opening degree of the outdoor electric expansion valve (25). At that time, the operating capacity of the compressor (1) is determined by the high pressure value detected by the high pressure sensor (Hps) and the low pressure sensor (Hps).
The pressure difference between the low pressure value and the low pressure value detected at L ps is controlled to a predetermined set value.

Then, in step S5, a discharge oil recovery timer (not shown) having a predetermined set time (for example, about 4 minutes) is set, and in step S6, a check is made to determine whether a command to stop the compressor (1) has been output. In other words, it is determined whether or not the discharge oil recovery timer is allowed to count, and if the timer count is prohibited, the discharge oil recovery timer is reset in step S7 and the process returns to step S6, while the determination in step S6 is that the timer count is allowed. When this happens, the process advances to step S8, and a discharge oil recovery operation is performed while counting the discharge oil recovery timer. That is, as shown in the second column of Table 1 above, the outdoor fan (26) is stopped and the outdoor heat exchanger (2)
The function of the outdoor electric expansion valve (2
1) and the indoor electric expansion valve (51) are fully closed, and the first and second indoor opening/closing valves (52) and (53) are both controlled to open. In other words, the bypass opening/closing means (
36), the flow rate of the refrigerant is increased and the oil remaining in the discharge line (31) is recovered to the compressor (1).

The above-mentioned discharge oil recovery operation is performed continuously for the above-mentioned set time based on the determination in step S9.

Next, if the discharge oil recovery timer times up in the determination in step S9, a suction oil recovery timer (not shown) having a predetermined set time (for example, about 4 minutes) is set in step S11, and in step S11 It is determined whether or not the timer count is allowed. If the timer count is not allowed, the process moves to step SI2 and the timer count is set for a predetermined time (
For example, the suction oil recovery timer having a time of about 4 minutes is reset, and if the timer count is permitted, the process proceeds to step SI3, and suction oil recovery operation is performed while counting the suction oil recovery timer.

That is, as shown in the third column of Table 1, the operating capacity of the compressor (1) is maximized, the air volume of the outdoor fan (26) is maximized, and the four-way selector valve (21) is While switching to the solid line side and making the outdoor heat exchanger (2) function as a condenser,
While the outdoor electric expansion valve (25) is fully opened, each indoor unit (B).

..., each indoor electric expansion valve (51), while closing the first indoor on-off valve (52) and opening the second indoor on-off valve (53) to make the indoor heat exchanger (5) function as an evaporator.・
By fully opening the opening of the refrigerant, the amount of refrigerant to be circulated is increased and the oil in each device, refrigerant pipe, etc. is quickly recovered to the compressor (1) by slightly damp operation. After that, step S1
After the set time has elapsed in the determination in step 4, the suction oil recovery operation is performed continuously for the set time, and then the control is terminated.

In the above flow, in step S8, during oil recovery operation of the air conditioner, the gas pipe side of the outdoor heat exchanger (heat source side heat exchanger) (2) is connected to the suction line (32) for each indoor heat exchanger for a certain period of time. The gas pipe sides of the exchangers (utilization side heat exchangers) (2), ... are connected to the discharge line (31), and a part of the discharged refrigerant is transferred from the first indoor branch pipe (31b) to the second indoor room. The four-way switching valve (outdoor connection switching means) (21
), indoor connection switching means (35) and bypass opening/closing means (
A discharge oil recovery control means (101) is configured to control the discharge oil recovery control means (101), and in step S+3, during the oil recovery operation, the compressor is operated for a predetermined time after the discharge oil recovery operation by the discharge oil recovery control means (101) is completed. Increasing the operating capacity of (1) and increasing the opening degree of the outdoor electric expansion valve (heat source side flow control valve) (25) and each indoor electric expansion valve (user side flow control valve) (51), etc. , the gas pipe side of the outdoor heat exchanger (2) is connected to the discharge line (31), and each indoor heat exchanger (
5) The gas pipe side of... is the suction line (32)
The above four-way switching valve (outdoor connection switching means) to be connected to
(21) and an intake oil recovery control means (102) that controls the indoor connection switching means (35). .

Therefore, in the invention of claim (1), during oil recovery operation,
For a certain period of time, the discharge oil recovery control means (101)
In each indoor unit (B),..., a part of the discharged refrigerant is transferred to the first indoor branch pipe (31b) and the second indoor branch pipe (32
b) is controlled to bypass to the suction line (32) via. In that case, the refrigerant is bypassed between the high-pressure discharge line (31) and the low-pressure suction line (32), so even if the operating capacity of the compressor (1) is small, the discharge line ( 31) through which the gas refrigerant flows at high speed. In other words, the discharge line (3
1) The velocity of the refrigerant inside can be increased, thus
The oil remaining in the refrigerant piping on the discharge line (31) can be effectively recovered.

In the invention of claim (2), in addition to the invention of claim (1), the suction oil recovery control means (101) operates for a predetermined time after the discharge oil recovery control means (101) finishes the discharge oil recovery operation.
02), the operating capacity of the compressor (1) is increased, and the outdoor electric expansion valve (25) and each indoor electric expansion valve (21),
All indoor heat exchanger (5) with the opening degree of...
Since the oil recovery operation is performed in a cooling cycle in which the outdoor heat exchanger (2) functions as an evaporator and the outdoor heat exchanger (2) functions as a condenser, the amount of refrigerant circulated is large and the operation is slightly damp, resulting in the suction line (32) etc. The oil accumulated in the refrigerant piping and each device is collected by the compressor (1), and in addition to the effect of the invention of claim (1), the oil accumulated in each part other than the discharge line (31) is recovered by the main refrigerant. Oil recovery can be effectively performed throughout the circuit (3). In particular, if the discharge oil recovery operation cannot be performed for a long time due to problems such as noise caused by high-speed refrigerant passing during the discharge oil recovery operation, the oil in the discharge line (31) can be removed by short-time discharge oil recovery operation. Inhalation line (32)
It is also possible to control the oil to be recovered once and then returned to the compressor (1) through suction oil recovery operation. Therefore, when used in conjunction with the above-mentioned discharge oil recovery operation, the oil recovery can be highly effective. .

Next, a second embodiment according to the invention of claim (3) will be described based on FIGS. 4, 5, and Table 2.

FIG. 4 shows the overall configuration of the air conditioner according to the second embodiment, and the outdoor unit (A) includes two outdoor heat exchangers (2
a) and (2b) are arranged, and the outdoor electric expansion valve (
25a) and (25b) to the liquid line (33), while the gas pipe side has two four-way switching valves (21a),
(21b), a first outdoor branch pipe (22a-1),
(22b-1) and a second outdoor branch pipe (22a-2),
It is switchably connected to the discharge line (31) and the suction line (32) via (22b-2).

The outdoor heat exchangers (2g) and (2b) are arranged in parallel in the ventilation path of a common outdoor fan (26), with one outdoor heat exchanger (2a) on the windward side and the other outdoor heat exchanger (2a) on the windward side. The exchanger (2b) is arranged on the leeward side.

Furthermore, the discharge line (31) and the first outdoor branch pipe (22b
-1) from the discharge line (31) upstream of the joint with the suction line (32) and the second outdoor branch pipe (22b-2).
), and the above accumulator (
41) A pressure equalizing bypass passage (42) is provided for the upstream suction line (32), allowing bypass of the refrigerant;
The pressure equalization bypass path (42) is provided with a pressure equalization on/off valve (
42a) and a capillary tube (42b) are interposed. The other configurations are the same as those of the first embodiment.

Here, the control details of the oil recovery operation according to the second embodiment will be explained based on the flowchart of FIG. After performing gri (see the top column of Table 2), proceed to step R5, and in step R5,
A pressure equalization control timer (not shown) having a predetermined set time (for example, about 2 minutes) is set, and pressure equalization control is performed in step R6 until the pressure equalization control timer times out as determined in step R7. In other words, the second item in Table 2 above
As shown in the columns, the operating capacity of the compressor (1) is set to the minimum (about 20%), the air volume of the outdoor fan (26) is set to the maximum, and each indoor electric expansion valve (51), .. completely closed, and close the outdoor heat exchanger (2a) on the windward side.
) is used as an evaporator and the outdoor heat exchanger (2b) on the leeward side is used as a condenser. is opened to about half open and the leeward side outdoor electric expansion valve (25b) is fully opened.
42a) to bypass a part of the discharged refrigerant to the suction side, the pressure is equalized until the differential pressure between the high pressure value and the low pressure value becomes a small value.

After that, in steps R8 to RI7, a discharge oil recovery operation (
(see column 3 of Table 2) and suction oil recovery operation (2nd column)
(See the column in the fourth row of the table) and ends the control.

In the above flow, in step R6, during the oil recovery operation, before the discharge oil recovery operation by the discharge pipe oil recovery control means (101), the pressure of the discharge refrigerant and the pressure of the suction refrigerant are equalized. The pressure equalization on/off valve of the bypass path (42) (
A pressure equalization control means (103) is configured to control 42a).

Therefore, in the invention of claim (3), the above claim (1)
) or (2), the discharge oil recovery control means (1)
01), the pressure equalization control means (103) controls the discharge line (31) and suction line (
After the pressure is equalized and the pressure difference between high and low pressures has almost disappeared, the discharge oil recovery operation is started, and a part of the discharged refrigerant is transferred to the 13th inner branch pipe ( 31b) to the suction side via the second indoor branch pipe (32b), the bypass opening/closing means (36) is controlled. If the differential pressure between high and low pressures is large at the start of this refrigerant bypass, the refrigerant passes at high speed, which may generate loud passing noise and impair the feeling of air conditioning. ), the high pressure and low pressure are equalized by the pressure equalization control means (103) before the refrigerant bypass starts, so that generation of loud refrigerant passing noise can be suppressed as much as possible.

In the second embodiment, the pressure equalization control is carried out for a set period of time. The pressure equalization control may be performed until the pressure reaches a certain value.

In addition, in each indoor unit (B), the two indoor on-off valves (5) in each of the above embodiments are used as indoor connection switching means.
2), a four-way switching valve can also be used instead of (53). FIG. 6 shows a modified row equipped with such an indoor connection switching means, and shows only a part of the indoor unit (B).

Here, (54) connects the gas pipe side of the indoor heat exchanger (5) to the first indoor branch pipe (31 b) and the second indoor branch pipe (31 b).
2b), an indoor four-way switching valve (56) is a bypass path provided via an on-off valve (55) between the first indoor branch pipe (31 b) and the second indoor branch pipe (32b); The indoor four-way switching valve (54) constitutes an indoor connection switching means, and the on-off valve (55) and the bypass path (56)
This constitutes a bypass opening/closing means (36) that bypasses the refrigerant from the discharge line (31) to the suction line (32) during the discharge oil recovery operation. The other connection boat of the indoor four-way switching valve (54) is connected to the second indoor branch pipe (32b) via a capillary tube (58). The other configurations are the same as in each of the above embodiments.

(Effect of the invention) As explained above, according to the invention of claim (1), in an air conditioner in which a plurality of indoor units are connected in parallel to an outdoor unit, the discharge line, suction line, and liquid line are connected to each other in parallel. The gas pipe side of each indoor heat exchanger is provided from the outdoor side to the indoor side, and the gas pipe side of each indoor heat exchanger is branched into a first indoor branch pipe and a second indoor branch pipe, which are switchably connected to a discharge line and a suction line, respectively. , during oil recovery operation, the first
Since a portion of the discharged refrigerant is bypassed from the indoor branch pipe to the second indoor branch pipe, the speed of the refrigerant in the discharge line is increased without causing an excessive rise in high pressure due to an increase in the operating capacity of the compressor. Therefore, oil remaining in the discharge line can be effectively recovered.

According to the invention of claim (2), in addition to the invention of claim (1), the heat source side heat exchanger is used as a condenser for a predetermined period of time after the end of the discharge oil recovery operation, and each user side heat exchanger is operated as a condenser. In the cooling cycle, the compressor functions as an evaporator, and oil is recovered by increasing the operating capacity of the compressor and increasing the opening of each flow control valve, which allows for a large amount of refrigerant circulation and operation that is slightly humid. Accordingly, the oil remaining in each part other than the discharge line can be effectively recovered, and therefore, the effective recovery can be achieved.

According to the invention of claim (3), the above claim (1) or (
In the invention of 2J, pressure equalization control is performed before discharge oil recovery operation to equalize high pressure and low pressure.
It is possible to suppress as much as possible the generation of the high-speed refrigerant passage noise that accompanies the start of the bypass of the discharged refrigerant in the discharged oil recovery operation, and thus it is possible to prevent the air-conditioned feeling from deteriorating.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 and 3 show a first embodiment of the present invention, FIG. 2 is a refrigerant piping system diagram of an air conditioner, FIG. 3 is a flowchart showing control details of oil recovery operation, and FIGS. FIG. 5 shows a second embodiment, FIG. 4 is a refrigerant piping system diagram of an air conditioner, and FIG. 5 is a flowchart showing control details of oil recovery operation. FIG. 6 is a refrigerant piping system diagram showing the configuration of an indoor unit according to a modification. 1 Compressor 2 Outdoor heat exchanger (heat source side heat exchanger) 3 Main refrigerant circuit 5 Indoor heat exchanger (user side heat exchanger) 21 Four-way switching valve (outdoor connection switching means) 22-1. -2 1st. Second outdoor branch pipe 25 Outdoor electric expansion valve (heat source side flow rate control valve) 31 Discharge line 32 Suction line 33 Liquid lines 31b, 32b 1st. Second indoor branch pipe 35 Indoor connection switching means 36 Bypass opening/closing means 42 Pressure equalizing bypass path 42a Pressure equalizing opening/closing valve 51 Indoor electric expansion valve (utilization side flow rate control valve) 101 Discharge oil recovery control means 102 Suction oil recovery control means 103 Equalization pressure control means

Claims (3)

[Claims] (1) Variable capacity compressor (1), heat source side heat exchanger (2)
and an outdoor unit (
In contrast to A), a plurality of indoor units (B) each having a user-side heat exchanger (5) and a user-side flow control valve (51),...
In an air conditioner in which ・are connected in parallel, a discharge line (31) extending from the discharge side of the compressor (1)
) and a suction line (3) extending from the suction side of the compressor (1).
2), a liquid line (33) extending from the liquid pipe side of the heat source side heat exchanger (2), and a connection between the gas pipe side of the heat source side heat exchanger (2) and the discharge line (31) and the suction line. (32)
an outdoor connection switching means (21) that switches between ) A second indoor branch pipe (32b) communicating with
and the connection on the gas pipe side of the user side heat exchanger (5) as described above.
It is equipped with indoor connection switching means (35) for switching between the indoor branch pipe (31b) and the second indoor branch pipe (32b), and each of the first indoor branch pipe (31b) and the second indoor branch pipe (3).
Bypass opening/closing means (36) for connecting and disconnecting with 2b)
), and during oil recovery operation, a portion of the discharged refrigerant flows from the first indoor branch pipe (31b) to the second indoor branch pipe (32b) for a certain period of time.
) The discharge oil recovery control means (101) controls the bypass opening/closing means (36) so that the oil is bypassed to the suction side via the
) An operation control device for an air conditioner, characterized by comprising: (2) During oil recovery operation, the operating capacity of the compressor (1) is increased for a predetermined period of time after the discharge oil recovery control means (101) finishes the discharge oil recovery operation, and the heat source side flow control valve (25)
The opening degree of each user-side flow control valve (51) is increased, and the gas pipe side of the heat source-side heat exchanger (2) is connected to the discharge line (31), so that the gas of each user-side heat exchanger (5) is increased. The outdoor connection switching means (21) and the indoor connection switching means (35) are connected so that both pipe sides are connected to the suction line (32).
2. The operation control device for an air conditioner according to claim 1, further comprising an intake oil recovery control means (102) for controlling the air conditioner. (3) A pressure equalizing bypass path (42) connecting the discharge pipe and suction pipe of the compressor (1) so that the discharged refrigerant can be bypassed, and an opening/closing means (42a) for opening and closing the pressure equalizing bypass path (42). During the oil recovery operation, before the discharge oil recovery operation by the discharge pipe oil recovery control means (101), the pressure equalization bypass passage (42) is opened and closed so that the discharge pressure and the suction pressure are equalized.
3. The operation control device for an air conditioner according to claim 1, further comprising pressure equalization control means (103) for controlling the pressure equalization control means (103).