JP2002327975A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner which optimizes an oil holding amount in a compressor in a refrigerating cycle having in combination a variable volume compressor and a constant volume compressor and which reduces the oil holding amount of the overall refrigerating cycle. SOLUTION: The air conditioner comprises the refrigerating cycle having a plurality of the compressors, a gas-liquid separator, an oil separator, a heat source side heat exchanger, various types of expansion valves and a user side heat exchanger sequentially connected via a duct in such a manner that an oil discharging connecting port, low-pressure side ducts such as a discharge duct and a suction duct or the like are provided in the compressors. The conditioner further comprises a return oil duct for connecting the connecting port of the compressor to the discharge duct of an upstream side from a confluent point of the discharge duct, and an oil return circuit for connecting the discharge duct of the upstream side from the confluent point of the discharge duct to the low-pressure side duct.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner using a refrigeration cycle, and more particularly to an air conditioner suitable for stabilizing an oil amount of a compressor for a refrigeration cycle.

[0002]

2. Description of the Related Art In the first prior art, in the case of a plurality of compressors in which a high pressure chamber type compressor is connected, the operation and the stop are performed at the same time. The compressor cannot be applied to a refrigeration cycle in which a variable capacity compressor is always operated and a constant capacity compressor is operated as needed by controlling the capacity by combining the compressor with a fixed capacity compressor.

As a second prior art, Japanese Patent Laid-Open No. 10-1
As disclosed in Japanese Patent No. 41785, an oil separator is provided in each circuit in order to return surplus oil of a plurality of compressors to the system side.

[0004]

The first prior art is a refrigeration cycle composed of a combination of a variable capacity compressor and a fixed capacity compressor. However, no consideration is given to the fact that the oil accumulated in the stopped compressor cannot be discharged, and the amount of oil accumulated in the compressor is taken into account. Was causing a decline. In order to avoid this and reduce the oil amount, the compressor must be operated at the same time, and there is a problem that the capacity control range is greatly limited.

In the second prior art, a separator must be provided in each circuit, and there is a problem in productivity that the number of parts increases and the cost increases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a refrigerating cycle composed of a combination of a variable capacity compressor and a fixed capacity compressor, wherein the amount of oil held in the compressor is It is an object of the present invention to provide an air conditioner that optimizes the temperature and reduces the amount of oil in the entire refrigeration cycle.

[0007]

Means for Solving the Problems To achieve the above object, an air conditioner according to the present invention is characterized by what is described in each claim of the claims. The air conditioner according to the first aspect of the present invention provides a refrigeration cycle by connecting a plurality of compressors, a gas-liquid separator, an oil separator, a heat source side heat exchanger, various expansion valves, and a use side heat exchanger. The compressor has an oil discharge connection port,
In an air conditioner provided with a low-pressure side pipe such as a discharge pipe and a suction pipe, an oil return pipe that connects the oil discharge connection port of the compressor and the discharge pipe upstream from a junction of the discharge pipe. An oil return circuit is provided for connecting the discharge pipe upstream of the junction of the discharge pipe and the low-pressure pipe.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a refrigeration cycle of an air heat source type air conditioner. Inside the two-dot chain line is the indoor unit 5
0, the outdoor unit 60 is shown.

The refrigerating cycle includes a compressor 1, an oil separator 9,
It comprises a four-way valve 2, an outdoor heat exchanger 3 as a heat source side heat exchanger, an outdoor expansion valve 4, an indoor expansion valve 5, an indoor heat exchanger 6 as a use side heat exchanger, and a gas-liquid separator 7. Are connected by piping. The outdoor and indoor heat exchangers are each provided with a blower 8, and the air is blown to each heat exchanger to exchange heat between the refrigerant and air for air conditioning. The refrigeration cycle constituted by these components takes in pressure detection means 16 such as Ps in FIG. 1 and temperature detection means 17 such as Te in the detection value input means 18 and is operated by the refrigeration cycle operation means 19.

FIG. 1 shows an example in which two compressors 1 are connected in one refrigeration cycle. Discharge gas of each compressor 1 is joined by a connection pipe, and an oil separator 9 is provided after the joining. The refrigerating machine oil separated by the oil separator 9 is returned to the gas-liquid separator 7 by an oil return pipe 14, where it is mixed with a refrigerant to form an oil circulation circuit that returns to each compressor. The oil circulation circuit has been widely used in the past.

In the present invention, the oil return pipe 10 is connected between the oil return port 22 as the oil discharge connection port of the compressor 1 and the pipe route of the discharge pipe 20. The oil return pipe 10 is for preventing oil from being stored in the closed vessel of the compressor 1 in an amount larger than the required oil amount of the compressor 1 both during operation and on the stop side. In particular, during operation, the compressor 1 used in the present embodiment is a scroll compressor of a high-pressure chamber type, and the inside of the compressor 1 is maintained at a high pressure. Can discharge the oil in the compressor 1 to the oil return pipe 10 side. The pressure Pd2 in the discharge pipe 20 is lower than the pressure Pd1 in the compressor 1 by only the contraction loss ΔP1 at the outlet of the compressor 1 of the discharge pipe 20 and the pressure loss ΔP2 of the pipe. The difference, Pd1-Pd2 =
Return oil at ΔP1 + ΔP2 via oil return pipe 10 and discharge pipe 20
Can be released.

Further, piping around each compressor 1 includes:
A check valve 11 is provided downstream of the connection point of the discharge pipe 20 with the oil return circuit 12 described below and upstream of the junction of the discharge pipe 20.
An electric valve 13 is provided on an oil return circuit 12 that connects a high pressure side discharge pipe 20 and a low pressure side gas-liquid separator 7 upstream suction pipe 21.

The two compressors 1 can be operated and stopped in accordance with the load of the indoor heat exchanger 6,
Stop-side compressor 1 when one is running and the other is stopped
Excess refrigeration oil accumulated in the compressor is discharged to the gas-liquid separator 7 via the oil return circuit 12 by opening the electric valve 13 of the stop-side compressor 1.

When both compressors are operating,
Excess oil is discharged to the discharge pipe 20 by the oil return pipe 10, and is discharged to the gas-liquid separator 7 from the oil return pipe 14 via the oil separator 9.

When both compressors are stopped, the motor-operated valve 15 installed in the oil return pipe 14 is closed, so that the high-pressure side and the low-pressure side are completely separated. .

As a result, the liquid refrigerant accumulated in the high pressure pipe immediately after the stoppage can be prevented from flowing to the low pressure side through the oil return pipe 14, so that the liquid refrigerant accumulates in the gas-liquid separator 7. And the occurrence of liquid compression during startup can be suppressed.

The connection position of the oil return pipe 10 of the compressor 1 will be described with reference to FIG.

The oil return port 22 provided in the compressor 1 is located near the optimum position of the oil amount required for the compressor 1, and the excess beyond this position is an excess amount. The surplus oil is guided into the discharge pipe 20 via the oil return pipe 10 due to the pressure loss in the discharge pipe 20 during the operation of the compressor 1. When the compressor 1 is stopped, no pressure loss occurs in the discharge pipe 20, but the connection point between the oil return pipe 10 and the discharge pipe 20 of the compressor 1 is located below the oil return port 22. The surplus oil is discharged by the difference between the oil return port 22 and the oil level 25, and the oil is accumulated at a position in the discharge pipe 20 where the pipe position is lowest. The oil stored in the lower position passes through the oil return circuit 12 connected below the connection point, and is supplied to the gas-liquid separator 7.
It is a structure to return to.

Referring to FIG. 3, the oil return pipe 10 is
The fact that the vehicle passes below will be described in detail.
When the oil return pipe 10 is connected to the oil return port 22 via a position lower than the oil return port 22 of the compressor 1, excess oil in the compressor 1 Emitted with a difference in surface height of 25. As shown by the broken line, the oil return pipe 10
Connected via a position higher than the oil return port 22 of
The oil in the compressor 1 accumulates up to the maximum height 26 position of the oil return pipe 10, so that excess oil cannot be discharged from the oil return port 22. Also, in this case, the required amount of oil in the entire refrigeration cycle requires the maximum amount of oil accumulated in each compressor 1, and excess oil is sealed in, thereby causing the performance of the refrigeration cycle to deteriorate. Will be. In the present embodiment, these are avoided and a refrigeration cycle with an appropriate oil amount is realized.

Next, description will be made with reference to FIG. In the case of a refrigeration cycle using a plurality of compressors 1, the path of the discharge pipe 20 for discharging the refrigerant from the compressor 1 once passes through a position higher than the discharge port of the compressor 1, and then returns to the compressor 1. Oil port 2
2 was disposed below. After a portion serving as an oil reservoir is provided here, a pipe is arranged again above, a check valve 11 is provided, and then the discharge pipe 20 of the other compressor 1 is connected.

When a combination of a plurality of compressors 1 of two types, a variable capacity compressor 1 and a fixed capacity compressor 1, is used, the stopped fixed capacity compressor 1 and the operated variable capacity compressor 1 are combined. May be present in the same refrigeration cycle at the same time. Even in this case, the discharge pipe 2 of each compressor 1
Since the check valve 11 is provided at the position 0, it is possible to prevent the phenomenon that the refrigerant is accumulated in the stopped compressor 1.

FIG. 5 shows an example in which the components are simplified as compared with FIG. The oil return pipe 10 is not provided on the side of the variable capacity compressor 1 which is always operated during operation. This is because even if there is some surplus oil in the compressor 1 that is operating at all times, the oil can be appropriately discharged by the discharged gas. The constant-capacity compressor 1 that is operated as needed stores oil up to the oil return port 22 of the oil return pipe 10, and when all the compressors 1 are stopped, the oil from the constantly operating compressor 1 is removed. This is because there is no need to discharge.

The compressor which is always operated is located upstream of the compressor which is operated as needed in the discharge pipe 20. This is to prevent the oil from being discharged from the discharge pipe 20 of the compressor that is operated as needed by the flow at the junction of the discharge pipe 20 of the compressor that is always operated when the compressor that is operated as needed is stopped, and the oil is accumulated.

Further, in the oil return circuit 12, the motor-operated valve 13 is not arranged individually for each compressor 1, but is arranged after the oil return circuit 12 has joined. At this time, the check valve 23 is connected to each oil return circuit 12 just before the oil return circuit 12 joins.
To be provided.

If the motor-operated valve 13 is opened, the discharge pressure of the compressor 1 will decrease during operation. However, the refrigeration cycle operating means 19 minimizes the time during which the motor-operated valve 13 is open. Accordingly, it is possible to open and close the circuit while minimizing the influence of pressure fluctuation on the refrigeration cycle during operation. This can also reduce the manufacturing cost.

In this embodiment, the case where two compressors 1 are provided in one refrigeration cycle is shown, but it goes without saying that the same effect can be obtained even when the number of connected compressors 1 is increased to three or more. No. Further, although the description has been made using an air-cooled refrigeration cycle, it goes without saying that the same effect can be obtained by other methods such as a water-cooled type.

Further, in this embodiment, the indoor unit 50
Has shown an example of one so-called single cycle, but the same effect can be obtained also in a so-called multi-cycle in which a plurality of indoor units 50 are connected. Also, the outdoor unit 6
When there are a plurality of zeros, the same effect can be obtained in a cycle in which a so-called heat storage unit that stores heat in ice, water, or the like is connected.

[0029]

According to the present invention, since the surplus oil can be discharged by the oil discharge circuit of the compressor, the required amount of oil in the refrigeration cycle is reduced.

According to the present invention, since the oil discharge circuit is connected to the discharge pipe below the oil discharge connection port, surplus oil can be discharged even when the compressor is stopped. It has the effect of reducing the amount.

According to the present invention, a check valve is disposed in each of the discharge pipes of the compressor, and when one of the compressors is operated and the other is stopped, the operating compressor discharges. There is an effect that surplus oil does not accumulate in the stopped compressor.

[Brief description of the drawings]

FIG. 1 is a refrigeration cycle system diagram.

FIG. 2 is an explanatory view of a position of an oil return port of the compressor.

FIG. 3 is an explanatory diagram of an oil return pipe connection path.

FIG. 4 is an explanatory diagram of a discharge pipe connection path.

FIG. 5 is an explanatory diagram of a simplified version discharge pipe connection path.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Compressor 2 ... Four-way valve 3 ... Outdoor heat exchanger 4 ... Outdoor expansion valve 5 ... Indoor expansion valve 6 ... Indoor heat exchanger 7 ... Gas-liquid separator 8 ... Blower 9 ... Oil separator 10 ... Oil return piping 11 ... check valve 12 ... oil return circuit 13 ... electric valve 14 ... oil return pipe 15 ... electric valve 16 ... pressure detection means 17 ... temperature detection means 18 ... detection value input means 19 ... refrigeration cycle operation means 20 ... discharge pipe 21 ... Suction pipe 22 ... Oil return port 23 ... Check valve 25 ... Oil level 26 ... Maximum height of oil return pipe 50 ... Indoor unit 60 ... Outdoor unit Td ... Compressor discharge refrigerant temperature Ts ... Compressor suction refrigerant temperature Ta0 ... outdoor air temperature Te1 ... outdoor heat exchanger inlet refrigerant temperature Te2 ... outdoor heat exchanger outlet refrigerant temperature Ta1 ... indoor air suction temperature Ta2 ... indoor air blowing temperature Tr1 ... indoor heat exchanger inlet refrigerant temperature Tr2 ... indoor heat exchanger outlet cold Temperature Ps ... compressor suction pressure Pd ... compressor discharge pressure Pd1 ... compressor pressure Pd2 ... discharge pipe pressure △ P1 ... contraction loss △ P2 ... piping loss

Continued on the front page (72) Inventor Shunji Sasaki 390 Muramatsu, Shimizu-shi, Shizuoka Prefecture Inside Hitachi Air Conditioning Systems Shimizu Production Headquarters (72) Inventor Hiroaki Tsuboe 390 Muramatsu, Shimizu-shi Shizuoka Prefecture Hitachi Air Conditioning Systems Shimizu Production Headquarters (72) Inventor Narashi Miyake 390 Muramatsu, Shimizu-shi, Shizuoka Pref.Hitachi Air Conditioning Systems Co., Ltd.

Claims (5)

[Claims] A plurality of compressors, a gas-liquid separator, an oil separator,
A heat source side heat exchanger, various expansion valves and a use side heat exchanger are connected by piping to form a refrigeration cycle, and the compressor is provided with a low pressure side pipe such as an oil discharge connection port, a discharge pipe and a suction pipe. In the air conditioner, an oil return pipe connecting the oil discharge connection port of the compressor and the discharge pipe upstream of a junction of the discharge pipe, and the discharge upstream of a junction of the discharge pipe. An air conditioner comprising an oil return circuit for connecting a pipe to the low-pressure side pipe. 2. The oil return pipe according to claim 1, wherein the pipe path is below the oil discharge connection port and is connected to the discharge pipe below the oil discharge connection port. The air conditioner according to item 1. 3. The oil return circuit is connected to the discharge pipe below the oil discharge connection port, and the connection point is
3. The air conditioner according to claim 1, further comprising a valve located below a connection point between the discharge pipe and the oil return pipe and capable of shutting off a circuit. 4. 4. The discharge pipe is provided with a check valve between a junction of the discharge pipe and a downstream of any one of the oil return pipe and a connection point between the oil return circuit and the discharge pipe. The air conditioner according to any one of claims 1 to 3, wherein 5. The compressor according to claim 1, wherein the plurality of compressors include a variable capacity compressor that is constantly operated and a fixed capacity compressor that is operated as needed, and only the fixed capacity compressor is provided with the oil return pipe. The air conditioner according to any one of claims 1 to 4, wherein: