JPH0623624B2 - Oil level control device for multi refrigerator - Google Patents

Description

Description: (a) Field of Industrial Application The present invention relates to an improvement in an oil level control device for a multi-refrigerator, and more particularly to a plurality of compressors having different internal pressures of respective crank chambers, that is, suction pressures. The present invention relates to a multi-refrigerator such as a subcooler system, a satellite system, and a two-stage compressor equipped with the.

(B) Conventional technology Conventionally, a multi-refrigerator provided with a plurality of compressors having different crank chamber internal pressures has been proposed in JP-A-55-46315 and configured as a refrigerant circuit as shown in FIG. ing.

Explaining below, (1) is an auxiliary compressor in which the internal pressure of the crank chamber (1a), that is, the suction pressure is high, and (2) and (3) are the internal pressures of the crank chambers (2a) and (3a). Lower main compressor, (4) oil separator, (5) condenser, (6) receiver, (7) subcooler, (8) main expansion valve, (9) evaporator These are sequentially connected by piping to form a main refrigerant circuit. And the auxiliary compressor (1) and the main compressor
(2) The refrigerant gas discharged from (3) is introduced into the oil separator (4) through a common discharge pipe (10) having a check valve (21). The refrigerant gas separated from the oil by the oil separator is condensed by the condenser (5) and then introduced into the liquid receiver (6) to be stored as a liquid refrigerant. This liquid refrigerant then passes through the inside of the subcooler (7), where a part of the liquid refrigerant derived from the liquid receiver (6) is branched from the middle by the branch pipe (11), and the subcooler liquid solenoid valve (22) Passes through the auxiliary expansion valve
After being decompressed by (12), it flows in the subcooler (7) while exchanging heat with the liquid refrigerant in the main refrigerant circuit. As a result, the liquid refrigerant in the main refrigerant circuit is supercooled by a part of the liquid refrigerant branched from the middle. Further, the liquid refrigerant branched from the middle is evaporated in the subcooler (7), then derived from the subcooler, and returned to the auxiliary compressor (1). On the other hand, the liquid refrigerant in the main refrigerant circuit that is supercooled in the subcooler (7) is introduced into the main expansion valve (8) and the evaporator (9) and evaporated, and then the respective main compressors (2) (3) Have been returned to.

In the multi-refrigerator constructed as described above, the oil level control device thereof is constructed as disclosed in Japanese Patent Publication No. 55-21945 and shown in FIG. Explaining below, the auxiliary compressor (1) and the main compressor (2) (3) are discharged together with the refrigerant gas and separated and stored in the oil separator (4) through the common discharge pipe (10). Oil
(13) is supplied to the oil tank (15) through the oil return pipe (14). This is because the pressure in the oil tank (15) is maintained at a low pressure by the pressure equalizing pipe (16) connecting the oil tank and the suction side of the auxiliary pressure machine (1), and the oil separator (4 This is because the oil (13) is pumped by the pressure difference between the oil tank (15) and the oil tank (15). The oil (13) stored in this oil tank (15) is the oil return pipe.
It is supplied to the auxiliary compressor (1) and the main compressors (2) and (3) via (17) and the oil regulators (18), (19) and (20). This is an auxiliary compressor with a high suction pressure for the pressure in the oil tank (15).
By setting the pressure to be approximately the same as that of the crank chamber (1a) of (1) and by providing a drop between the oil tank and each of the compressors (1), (2) and (3), each oil from the oil tank The oil (13) is supplied to the regulators (18), (19) and (20) and the oil levels of the compressors (1), (2) and (3) are made uniform by the oil leveling action of the oil regulators.

However, the oil level control device for a multi-refrigerator thus configured sets the pressure in the oil tank (15) to substantially the same pressure as the auxiliary compressor (1) having a high suction pressure.
Therefore, the supply pressure of the oil (13) applied to the oil regulator (19) (20) from the oil tank via the oil return pipe (17) is likely to become excessively large, and in particular, the oil regulator (19) (20) Opens the valve beyond its capacity and unnecessarily feeds oil (13) to the main compressor (2) (3) with a low suction pressure. This disturbs the oil leveling function of the oil regulators (19) (20), and the auxiliary compressor (1) and the main compressor (2) (3)
Make the oil level uneven between the main compressor (2)
This causes various problems such as the increase in the oil discharge amount of (3), and the oil level control device lacks reliability. This problem is caused by the auxiliary compressor with high suction pressure.
Oil tank (15) and main compressor when (1) is stopped
(2) It becomes particularly remarkable because the differential pressure between (3) is further increased.

(C) Object of the Invention The present invention has been made in view of the above point, and an object thereof is to provide an oil level of a multi-refrigerator including a plurality of compressors having different internal pressures of crank chambers. In the control device, the oil supply pressure applied to the oil regulator mounted on the main compressor having a low suction pressure from the oil tank is prevented from being excessively increased, and the oil regulator's equalizing action is favorably maintained and the oil level is maintained. It is to improve the reliability of the control device.

(D) Structure of the invention The present invention is a multi-refrigerator equipped with a main compressor that sucks intake gas through a crank chamber and an auxiliary compressor that also sucks intake gas. The lower side of the main compressor is used as a main compressor, a common discharge pipe for guiding the refrigerant discharged from each of these compressors, an oil separator connected to this discharge pipe, and the oil of this oil separator are returned to the oil tank. Oil return pipe, a second oil return pipe for returning the oil in the oil tank to an oil regulator formed in the main compressor and the auxiliary compressor, and an equalizer communicating the oil tank and the suction side of the auxiliary compressor. Second composed of a pressure tube and connected to the main compressor
Is provided with a differential pressure valve in the oil return pipe, and a bypass pipe with an electromagnetic valve is provided in parallel with the differential pressure valve, and the difference in pressure between the suction side of the auxiliary compressor and the suction side of the main compressor Is provided with a differential pressure switch for opening and closing the solenoid valve, and when the pressure difference between the suction sides of the auxiliary compressor and the main compressor is small, the solenoid valve is opened by the differential pressure switch, and the oil tank Oil is supplied to the auxiliary compressor via the second oil return pipe and is also supplied to the main compressor via the second oil return pipe and the bypass pipe. On the other hand, when the pressure difference is large, a solenoid valve is used. The oil in the oil tank which is closed is supplied to the auxiliary compressor through the second oil return pipe and is supplied to the main compressor through the second oil return pipe and the differential pressure valve.

(E) Embodiment An embodiment of the present invention will be described below with reference to FIG. 2. Since the basic structure of the refrigerant circuit and its operation are the same as those of the conventional example shown in FIG. Description will be omitted, and only the points of this embodiment different from the conventional example, that is, the oil level control device will be described.

(1) is an auxiliary compressor on the side where the internal pressure of the crank chamber (1a), that is, the suction pressure is high. (2) and (3) are the respective crank chambers (2
a) The main compressor on the side with low internal pressure in (3a). (14) is a common refrigerant discharge pipe from the auxiliary compressor (1) and the main compressor (2) (3)
It is a first oil return pipe for supplying the oil (13) stored in the oil separator (4) after being discharged through (10) to the oil tank (15). This is a pressure equalizing pipe that connects the oil tank (15) and the refrigerant suction pipe (23) of the auxiliary compressor (1).
Since the oil tank is maintained at a low pressure by (24), the pressure difference causes the oil (1) in the oil separator (4) to
This is because 3) is pumped to the oil tank (15). (25) is the oil regulator (18) (1) that is equipped with the oil (13) in the oil tank (15) installed in the auxiliary compressor (1) and the main compressor (2) (3).
2nd feeding to each compressor (1) (2) (3) via 9) (20)
Oil return pipe. (26) is the second oil return pipe (25)
The differential pressure valve is provided between the auxiliary compressor (1) and the main compressors (2) and (3). This differential pressure valve (26) consists of the valve and the main compressor (2) (3)
The pressure in the crank chambers (2a) (3a) of the main compressors (2) (3) transmitted by the pipe (28) communicating with the refrigerant suction pipe (27) of the second oil from the oil tank (15) It detects the pressure difference with the oil supply pressure transmitted through the return pipe (25) and adjusts its opening.When this pressure difference is large, the opening is throttled to reduce the oil regulator (19) (20 )), The oil supply pressure applied to the second oil return pipe (25) is reduced by fully opening the oil when the differential pressure is small and opening a suitable amount of oil (13) in the oil tank (15) according to the supply pressure and the drop. The oil is supplied to the main compressors (2) and (3) via the oil regulators (19) and (20).

The oil (13) in the oil tank (15) is first supplied to the auxiliary compressor (1) via the second oil return pipe (25) and the oil regulator (18). As described above, the internal pressure of the oil tank (15) is set to the same pressure as the crank chamber (1a) of the auxiliary compressor (1), and the oil tank (15) is located above the auxiliary compressor (1). This is because the oil (13) can be supplied from the tank to the auxiliary compressor (1) by the supply pressure and the head of the tank. (29)
Is a bypass pipe branched from the middle of the pressure equalizing pipe (24) and connected to the refrigerant suction pipe (27) of the main compressors (2) and (3) having a low suction pressure. Reference numeral (30) is a solenoid valve provided in the bypass pipe (29). This solenoid valve (30) is an auxiliary compressor with high suction pressure.
It is set to open only when (1) stops. This is because when the auxiliary compressor (1) is stopped and the internal pressure of the compressor rises, the internal pressure of the oil tank (15) also rises due to the pressure equalizing pipe (24), and the second oil return pipe from the oil tank (15).
The oil supply pressure transmitted to each oil regulator (19) (20) via (25) becomes excessively high and the oil regulator
(18) (19) (20) This is to solve the problem of disturbing the pressure equalizing action, and when the auxiliary compressor (1) stops, the solenoid valve (30) is opened and the pressure equalizing pipe (24 ) To the refrigerant suction pipe (27) so that the main compressor is installed in the oil tank (15).
(2) The low pressure is applied to (3) to keep the internal pressure of the tank lower, and the oil (13) in the oil tank (15) is connected to the second oil return pipe (25) and the differential pressure valve (26). , Oil regulator (1
8) (19) (20) is also added to the head so that each compressor can be satisfactorily supplied to the compressor (1) (2) (3). still,
At this time, the differential pressure valve (26) is connected to the second oil return pipe (25) and the pipe (2
Since the pressure difference with 8) has almost disappeared, it is fully opened, and the oil supply performed via the second oil return pipe (25) is not interrupted.

Thus, (31) is a bypass pipe that branches from the middle of the second oil return pipe (25) to bypass the differential pressure regulating valve (26) and then communicates with the second oil return pipe (25) again. . Reference numeral (32) is an electromagnetic valve provided in the bypass pipe (31), which is opened and closed by a differential pressure switch (33) described later. (33) is the suction refrigerant pipe (2) of each of the auxiliary compressor (1) and the main compressor (2) (3).
3), (27) pressure is detected and ON-OFF by the differential pressure
It is a differential pressure switch that operates and opens and closes the solenoid valve (32) by this operation.

In such a configuration, when the pressure difference between the suction refrigerants of the auxiliary compressor (1) having a high suction pressure and the main compressors (2) (3) having a low suction pressure is small, the differential pressure switch ( The solenoid valve (32) is opened by 33). For this reason the oil tank (1
The oil (13) of (5) is supplied to the auxiliary compressor (1) via the second oil return pipe (25) and the oil regulator (18), and at the same time the second oil return pipe (25) and the bypass pipe ( 31), and is supplied to the main compressors (2) and (3) via the oil regulators (19) and (20), respectively. This is because there is not much pressure difference between the auxiliary compressor (1) and the main compressors (2) and (3), and the internal pressure of the oil tank (15) is not so high. (2)
(3) Oil is smoothly supplied due to its supply pressure and head.
This is because (13) can be supplied. However, the greatest feature of the present invention here is that even if the diameter of the differential pressure valve (26) is not sufficient, the main compressor (2) (via the second return pipe (25) ( This means that the oil supply pressure transmitted to 3) can be secured. That is, as a feature of the differential pressure regulating valve (26), it can be said that the opening / closing operation can be smoothly performed when the differential pressure acting on the valve is large, but the opening / closing operation cannot be reliably performed when the differential pressure is small. In other words, if the diameter of the differential pressure regulating valve (26) is designed to be small, it operates reliably even with a small differential pressure, but if the diameter is increased, leakage at the opening / closing portion is large and opening / closing operation cannot be performed reliably. From this,
The differential pressure valve (26) is limited in its diameter, and when actually used, it had to be applied with a diameter much smaller than the diameter of the second oil return pipe (25). In this embodiment, when the pressure difference between the suction refrigerants of the auxiliary compressor (1) and the main compressors (2) and (3) is small, the differential pressure valve (26) is bypassed and the second oil return is performed. Adjust the oil supply pressure of the oil tank (15) through the pipe (25) and the bypass pipe (31) to the main compressor (2) (3).
The above problem is solved by introducing the bypass pipe (31) and ensuring the pipe diameter of the bypass pipe (31). Also, auxiliary compressor (1)
When the pressure difference between the refrigerant sucked into the main compressors (2) and (3) is large, the solenoid valve (33) is closed by the differential pressure switch (33). Therefore, the oil (13) in the oil tank (15) is supplied to the auxiliary compressor (1) via the second oil return pipe (25) and the oil regulator (18) and the second oil return pipe ( 2
It is supplied to the main compressors (2) and (3) via the differential pressure valve (26) and the oil regulators (19) and (20), respectively. This is due to the action of the differential pressure regulating valve (26) described above, but since the differential pressure applied to the differential pressure regulating valve (26) at this time is large, the valve can operate reliably.

(F) Effects of the Invention As described above, according to the present invention, in the multi-refrigerator including the main compressor that sucks the intake gas through the crank chamber and the auxiliary compressor that also sucks the intake gas, the high suction pressure side Is the auxiliary compressor and the main compressor is on the low suction pressure side, and a common discharge pipe for guiding the refrigerant discharged from each of these compressors, an oil separator connected to this discharge pipe, and the oil of this oil separator. Of the oil tank to the oil tank, a second oil return pipe for returning the oil of the oil tank to an oil regulator formed in the main compressor and the auxiliary compressor, and a second oil return pipe of the oil tank and the auxiliary compressor. A pressure equalizing pipe communicating with the suction side is provided, and a differential pressure valve is provided in the second oil return pipe connected to the main compressor.
Also, a bypass pipe with an electromagnetic valve is provided in parallel with the differential pressure valve, and a differential pressure switch for opening and closing the electromagnetic valve by the difference in pressure between the suction side of the auxiliary compressor and the suction side of the main compressor. Therefore, when the pressure difference between the suction sides of the auxiliary compressor and the main compressor is small, the solenoid valve is opened by the differential pressure switch, and the oil in the oil tank is passed through the second oil return pipe. Is supplied to the auxiliary compressor while being supplied to the main compressor through the second oil return pipe and the bypass pipe, and when the pressure difference is large, the solenoid valve is closed by the differential pressure switch, and the oil in the oil tank is closed. The second
Is supplied to the main compressor through the second oil return pipe and the differential pressure valve, and is supplied to the main compressor through the second oil return pipe and the differential pressure valve. Bypass to secure the oil supply pressure that is transmitted from the second oil return pipe to the main compressor, while when the pressure difference is large, the differential pressure valve properly adjusts the oil supply pressure that is transmitted from the second oil return pipe to the main compressor. Can be adjusted. As a result, a reliable differential pressure valve can be applied even if its diameter is small, and the pressure of the oil supplied from the oil tank to the oil regulator installed in the main compressor can be adjusted with this differential pressure valve and bypass pipe configuration. Prevents excessive increase and even when the pressure difference is small and the oil supply pressure is small, this supply pressure is well transmitted to each oil regulator without going through a differential pressure valve, and the oil regulator's oil leveling action is maintained well. However, the reliability of the oil level device can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of refrigerant and oil of a multi-refrigerator showing a conventional example, and FIG. 2 is a circuit diagram of refrigerant and oil of a multi-refrigerator showing an embodiment of the present invention. (1) …… Auxiliary compressor, (2) (3) …… Main compressor, (4) …… Oil separator, (14) …… First oil return pipe, (15) ……
Oil tank, (18) (19) (20) …… Oil regulator,
(24) …… equalizing pipe, (25) …… second oil return pipe, (26)…
… Differential pressure valve, (31) …… Bypass pipe, (32) …… Solenoid valve, (33)
...... Differential pressure switch.

Claims (1)

[Claims] 1. In a multi-refrigerator including a main compressor that sucks intake gas through a crank chamber and an auxiliary compressor that also sucks intake gas, a side having a high suction pressure is placed on a side having a high suction pressure and a side having a low suction pressure. A common discharge pipe serving as a main compressor, which guides the refrigerant discharged from each of these compressors, an oil separator connected to this discharge pipe, and a first oil return pipe for returning the oil of this oil separator to an oil tank And a second oil return pipe for returning the oil in the oil tank to an oil regulator formed in the main compressor and the auxiliary compressor, and a pressure equalizing pipe communicating the oil tank and the suction side of the auxiliary compressor. However, a differential pressure valve is provided on the second oil return pipe connected to the main compressor, and a bypass pipe with an electromagnetic valve is provided in parallel on the differential pressure valve.
A differential pressure switch for opening and closing the solenoid valve is provided on the suction side of the auxiliary compressor and the suction side of the main compressor, and a differential pressure switch is provided for opening and closing the solenoid valve. Level control device.