CN104236169A - Oil return control method of full fixed frequency multi-line - Google Patents

Abstract

The invention discloses an oil return control method of a full fixed-frequency multi-split air conditioner, which comprises the following steps: a. the outlet of the oil separator (1) is communicated with the inlets of the two constant-frequency compressors (3) through a first oil return capillary tube (2); an outlet of the oil separator (1) is communicated with an inlet of a gas-liquid separator (5) through an oil return pipe (4), an oil return port (6) is formed in the bottom of the gas-liquid separator (5), the oil return port (6) of the gas-liquid separator (5) is communicated with an inlet of a second oil return capillary tube (8) with an electromagnetic valve (7), and an outlet of the second oil return capillary tube (8) is communicated with inlets of two constant-frequency compressors (3); b. when one fixed-frequency compressor (3) is started to operate, the electromagnetic valve (7) on the second oil return capillary tube (8) is closed, and when two fixed-frequency compressors (3) are started to operate simultaneously, the electromagnetic valve (7) on the second oil return capillary tube (8) is opened. The method can balance the oil quantity of each compressor and prevent the exhaust temperature of the compressor from being overhigh.

Description

Oil return control method of full fixed frequency multi-line

technical field

The invention relates to a multi-connected air conditioner unit, in particular to an oil return control method for a full fixed-frequency multi-connected unit.

Background technique

The multi-connected air conditioner unit in the prior art is referred to as a multi-connected unit for short, and it includes an outdoor unit, a plurality of indoor units connected in parallel, and two refrigerant circulation main pipes connecting each indoor unit and outdoor unit. The outdoor unit communicates with multiple indoor units connected in parallel through two refrigerant circulation main pipes.

Each outdoor unit includes a compressor, an oil separator, a four-way reversing valve, an outdoor heat exchanger (a condenser for cooling and an evaporator for heating) and a gas-liquid separator. The outlet of the compressor is connected with the inlet of the oil separator, the outlet of the oil separator is connected with the first valve port of the four-way reversing valve, the second valve port of the four-way reversing valve is connected with one end of the outdoor heat exchanger, and the outdoor heat exchanger The other end communicates with one of the two refrigerant circulation main pipes, and the other refrigerant circulation main pipe of the two refrigerant circulation main pipes communicates with the third valve port of the four-way reversing valve of each outdoor unit, and the four-way reversing valve The fourth valve port is connected with the inlet of the gas-liquid separator, and the outlet of the gas-liquid separator is connected with the inlet of the compressor. The compressor of the outdoor unit generally refers to an inverter compressor and a fixed frequency compressor connected in parallel.

Each indoor unit includes an electronic expansion valve of the indoor unit and an indoor heat exchanger (an evaporator for cooling and a condenser for heating). One end of the indoor heat exchanger communicates with one end of the electronic expansion valve of the indoor unit, and the electronic expansion The other end of the valve communicates with one of the two refrigerant circulation main pipes, and the other end of the indoor heat exchanger communicates with the other refrigerant pipe of the two refrigerant circulation main pipes.

In cooling mode, the first valve port of the four-way reversing valve is connected to the second valve port, and the third valve port is connected to the fourth valve port, that is, the refrigerant flows along the compressor, outdoor heat exchanger, indoor heat exchanger, compression In the heating mode, the first valve port of the four-way reversing valve is connected to the third valve port, and the second valve port is connected to the fourth valve port, that is, the refrigerant flows along the compressor, indoor heat exchanger, The route of outdoor heat exchanger and compressor circulates.

As the competition in the multi-split unit market continues to intensify, the cost control of air-conditioning companies has reached the point where the price of products must be compared, and the advantages of low-cost multi-split units in market competition are becoming more and more significant. Since the price of variable frequency compressors is more expensive than that of fixed frequency compressors, in order to control costs, some technicians have proposed the concept of full fixed frequency multi-connection, that is, all the compressors of outdoor units use parallel fixed frequency compressors to replace the traditional one. The frequency conversion is a certain frequency.

However, there is an insurmountable technical problem in this scheme, that is, the oil return problem of the two parallel compressors. Specifically, the oil return method in the prior art is to connect the inlet of each compressor with an oil return capillary with a solenoid valve to one end of an oil return main pipe, and the other end of the oil return main pipe is separated from the oil The outlet connection of the compressor, that is, each compressor corresponds to an oil return capillary with a solenoid valve. When the compressor is turned on, the solenoid valve of the compressor is opened to return oil, and the solenoid valve of the compressor that is not turned on is not opened. In this way, the oil quantity of each compressor is balanced. However, the solenoid valve in the prior art has a condition for normal operation, that is, the pressure difference between the two sides of the solenoid valve must be ≤ 2.0Mpa to work normally. Conventional compressors with variable frequency can run at reduced frequency to meet the pressure difference of the solenoid valve to ensure its normal opening and closing, but it is difficult to meet this condition in a system with all fixed frequency compressors. If a fixed-frequency compressor is not used, it will cause huge fluctuations to the entire system, causing various failures and damages. It was also suggested that the electromagnetic valve should not be installed at all, but the inability to control the on-off of the oil return line will also cause a series of hidden dangers. For example, when only one fixed-frequency compressor is started in the system, the oil originally used to lubricate the two compressors will all be exhausted. If one compressor is supplied with too much oil and the other has too little oil, there is a risk of burnout in such a long-term lack of oil compressor. Moreover, the lubricating oil will drive the high-temperature and high-pressure refrigerant back to the compressor. After all the lubricating oil supplied to the two compressors is supplied to one compressor, the return refrigerant originally borne by the two compressors will be fully loaded on one compressor, resulting in the high discharge temperature of the compressor and triggering the shutdown protection.

Contents of the invention

The technical problem to be solved by the present invention is to provide a full fixed-frequency multi-line oil return control method that can balance the oil volume of each compressor and prevent the exhaust temperature of the compressor from being too high.

The technical solution of the present invention is to provide a full fixed-frequency multi-line oil return control method, the specific steps of which are as follows:

a. Connect the outlet of the oil separator with the inlet of the first oil return capillary, connect the outlet of the first oil return capillary with the inlets of the two fixed-frequency compressors; connect the outlet of the oil separator with the inlet of the oil return pipe, and connect the The outlet of the oil return pipe is connected with the inlet of the gas-liquid separator, and an oil return port is provided at the bottom of the gas-liquid separator, and the oil return port of the gas-liquid separator is connected with the inlet of the second oil return capillary with a solenoid valve, and the first The outlet of the second oil return capillary is connected with the inlet of the two fixed-frequency compressors;

b. When one fixed-frequency compressor starts to run, close the solenoid valve on the second oil return capillary, and when two fixed-frequency compressors start to run at the same time, open the solenoid valve on the second oil return capillary.

The principle of this control method is: when only any compressor is turned on, the compressor that is turned on constitutes an oil return path, and the compressor that is not turned on is an oil return circuit breaker, and the lubricating oil in the oil separator passes through the first oil return capillary. Oil is returned to the compressor that is turned on, and the oil is not returned to the compressor that is not turned on. The excess lubricating oil in the oil separator will enter the gas-liquid separator through the oil return pipe and be stored. Any one of the compressors is fully lubricated and there is not too much lubricating oil in the starting compressor, that is, to ensure sufficient and appropriate oil return to any compressor that is starting; and the lubricating oil enters the gas-liquid separation from the oil return pipe After the device, the volume from the pipeline to the gas-liquid separator increases sharply, so the pressure drops sharply. At this time, one end of the solenoid valve is a low-pressure gas-liquid separator and the other end is a low-pressure compressor inlet, so there is no pressure at both ends of the solenoid valve. The difference is greater than 2.0Mpa and cannot work normally. When the two compressors are turned on at the same time, the solenoid valve is opened, so that the excess lubricating oil stored in the gas-liquid separator can quickly return to the oil circuit and circulate to the two compressors. oil, which can effectively prevent the oil shortage of the previously unstarted compressor. At this time, all the lubricating oil in the oil separator will lubricate the two compressors evenly through two oil circuits. The oil capillary goes to the compressor, and the second circuit, the oil separator, passes through the oil return pipe, the gas-liquid separator, and the second oil return capillary to the compressor.

Using the above method, compared with the prior art, the oil return control method of the full fixed-frequency multi-line unit of the present invention has the following advantages:

Through this control method, the oil volume of each compressor can be guaranteed to be balanced, and the excess part of the high-temperature and high-pressure refrigerant returned to the compressor with the lubricating oil is stored in the gas-liquid separator when only one compressor is turned on, while the two compressors At the same time, the two compressors are jointly responsible for the start-up to prevent the shutdown protection caused by the high discharge temperature of the compressor. Moreover, this control method overcomes the technical problem that the full fixed-frequency multi-line unit cannot return oil, makes the design of the full-fixed frequency multi-line unit possible, effectively reduces costs, and occupies a great advantage in the increasingly fierce market competition.

Description of drawings

Fig. 1 is a system schematic diagram of the oil return control method of the full fixed-frequency multi-line unit of the present invention.

As shown in the figure 1. Oil separator, 2. First oil return capillary, 3. Fixed frequency compressor, 4. Oil return pipe, 5. Gas-liquid separator, 6. Oil return port, 7. Solenoid valve, 8. The second oil return capillary, 9, refrigerant pipe, 10, refrigerant branch pipe.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Fig. 1, the oil return control method of the full fixed-frequency multi-line unit of the present invention has the following specific steps.

a. Connect the outlet of the oil separator 1 with the inlet of the first oil return capillary 2, connect the outlet of the first oil return capillary 2 with the inlets of the two fixed-frequency compressors 3; connect the outlet of the oil separator 1 with the oil return pipe The inlet of 4 is connected, and the outlet of the oil return pipe 4 is connected with the inlet of the gas-liquid separator 5. An oil return port 6 is set at the bottom of the gas-liquid separator 5, and the oil return port 6 of the gas-liquid separator 5 is connected with the solenoid valve. The inlet of the second oil return capillary 8 of 7 is communicated, and the outlet of the second oil return capillary 8 is communicated with the inlets of two fixed-frequency compressors 3 .

The outlet of the gas-liquid separator 5 communicates with the inlet of a conventional refrigerant pipe 9, the outlet of the refrigerant pipe 9 communicates with the inlets of two conventional refrigerant branch pipes 10, and the outlet of each refrigerant branch pipe 10 is connected with a fixed-frequency compressor 3 entrances are connected. The outlet of the first oil return capillary 2 communicates with the inlets of the two fixed-frequency compressors 3 means that the outlet of the first oil return capillary 2 communicates with the refrigerant pipe 9 . The outlet of the second oil return capillary 8 communicates with the inlets of the two fixed-frequency compressors 3 means that the outlet of the second oil return capillary 8 communicates with the refrigerant pipe 9 .

b. When a fixed-frequency compressor 3 starts running, close the electromagnetic valve 7 on the second oil return capillary 8, and when two fixed-frequency compressors 3 start running at the same time, open the electromagnetic valve 7 on the second oil return capillary 8. valve 7. In this way, the two oil return capillary tubes carry out the oil return cycle synchronously.

Claims (1)

1. a method for controlling oil return for full fixed-frequency multi-gang machine, is characterized in that: its concrete steps are as follows:

A, the entrance of the outlet of oil eliminator (1) with the first oil return capillary (2) to be communicated with, the outlet of the first oil return capillary (2) is communicated with the entrance of two invariable frequency compressors (3); The entrance of the outlet of oil eliminator (1) with oil return pipe (4) is communicated with, the entrance of the outlet of oil return pipe (4) with gas-liquid separator (5) is communicated with, an oil return opening (6) is established in gas-liquid separator (5) bottom, the entrance of the oil return opening (6) of gas-liquid separator (5) with the second oil return capillary (8) of provided with electromagnetic valve (7) is communicated with, the outlet of the second oil return capillary (8) is communicated with the entrance of two invariable frequency compressors (3);

B, when the start of invariable frequency compressor (3) runs, close the magnetic valve (7) on the second oil return capillary (8), when two invariable frequency compressors (3) start shooting operation simultaneously, open the magnetic valve (7) on the second oil return capillary (8).