阅读说明：本技术 冷藏冷冻机组的回油控制方法及冷藏冷冻机组 (Oil return control method of refrigeration and freezing unit and refrigeration and freezing unit ) 是由 孟庆良 宋强 毛守博 顾超 于 2021-05-28 设计创作，主要内容包括：本发明涉及一种冷藏冷冻机组的回油控制方法及使用该回油控制方法的冷藏冷冻机组。该回油控制方法包括：检测所述冷藏冷冻机组的压缩机的实时运行频率和对应的累计运行时长；基于所述实时运行频率和所述对应的累计运行时长,判断所述压缩机是否满足回油控制条件；当所述回油控制条件得到满足时,在所述压缩机的重启次数小于预定次数的条件下,控制所述压缩机实施运行回油模式。该冷藏冷冻机组的回油控制方法能够在压缩机的重启次数小于预定次数的条件下实施运行回油模式,实现在运行中断情况下顺利回油。(The invention relates to an oil return control method of a refrigeration and freezing unit and the refrigeration and freezing unit using the oil return control method. The oil return control method comprises the following steps: detecting the real-time running frequency and the corresponding accumulated running time of a compressor of the refrigerating and freezing unit; judging whether the compressor meets an oil return control condition or not based on the real-time running frequency and the corresponding accumulated running duration; and when the oil return control condition is met, controlling the compressor to implement an oil return operation mode under the condition that the restarting time of the compressor is less than the preset time. The oil return control method of the refrigerating and freezing unit can implement the oil return operation mode under the condition that the restarting times of the compressor is less than the preset times, and smooth oil return is realized under the condition of operation interruption.)

1. An oil return control method of a refrigeration and freezing unit is characterized by comprising the following steps:

detecting the real-time running frequency and the corresponding accumulated running time of a compressor of the refrigerating and freezing unit;

judging whether the compressor meets an oil return control condition or not based on the real-time running frequency and the corresponding accumulated running duration;

and when the oil return control condition is met, controlling the compressor to implement an oil return operation mode under the condition that the restarting time of the compressor is less than the preset time.

2. A method as claimed in claim 1, wherein the step of controlling the compressor to implement an oil return mode of operation when the oil return control condition is satisfied and when the number of restarts of the compressor is less than a predetermined number of restarts comprises:

judging whether the compressor is in a starting stage or an operating stage;

when the compressor is in a starting stage, judging whether the starting stage is interrupted, when the starting stage is not interrupted, after the starting stage is finished, the compressor enters the operation stage at a first operation frequency, and after a first preset operation time period, controlling the compressor to enter the operation oil return mode; when the starting phase is interrupted, restarting the compressor for the first time after a preset restart interval time period, wherein the restart count is 1;

judging whether the first restart is interrupted or not after the compressor is restarted for the first time, entering the operation stage at the first operation frequency after the first restart is finished when the first restart is not interrupted, and controlling the compressor to enter the operation oil return mode after the first preset operation time period; restarting the compressor a second time and a restart count of 2 after the predetermined restart interval period has elapsed while the first restart was interrupted;

and controlling the compressor to implement the operation oil return mode under the condition that the restarting times of the compressor are less than 2 times.

3. A method of controlling oil return to a refrigeration and freezing unit as claimed in claim 2,

when the compressor is in an operation stage, judging whether the operation stage is interrupted, and when the operation stage is not interrupted, controlling the compressor to enter the operation oil return mode after the first preset operation time period; when the running stage is interrupted, restarting the compressor for the first time after a preset restart interval time period, wherein the restart count is 1;

judging whether the first restart is interrupted or not after the compressor is restarted for the first time, entering the operation stage at the first operation frequency after the first restart is finished when the first restart is not interrupted, and controlling the compressor to enter the operation oil return mode after the first preset operation time period; restarting the compressor a second time and a restart count of 2 after the predetermined restart interval period has elapsed while the first restart was interrupted;

and controlling the compressor to implement the operation oil return mode under the condition that the restarting times of the compressor are less than 2 times.

4. A method of oil return control for a refrigeration and freezing assembly as claimed in claim 2 or 3, wherein the step of controlling the compressor to enter the oil return mode of operation after the first predetermined period of operation has elapsed comprises:

comparing the first operating frequency with a preset oil return frequency;

when the first operating frequency is greater than the preset oil return frequency, the compressor operates at an oil return frequency equal to the first operating frequency to return oil;

and when the first operating frequency is less than or equal to the preset oil return frequency, the compressor operates at the oil return frequency equal to the preset oil return frequency to return oil.

5. A method of oil return control for a refrigeration chiller as set forth in claim 4 wherein controlling said compressor into said oil return mode of operation after the first predetermined period of operation further comprises:

detecting an operation state of the compressor;

determining an oil return set time length based on the running state of the compressor;

and controlling the compressor to run at the oil return frequency and continuously for the oil return set time.

6. A refrigeration and freezing unit oil return control method as claimed in claim 5, wherein after the set oil return time period, the oil return control method clears each accumulated operation time period and ends oil return.

7. A method of controlling oil return to a refrigeration and freezing unit as claimed in claim 5,

when the running state of the compressor is a normal running state, the oil return set time is a first preset oil return time period; and is

When the running state of the compressor is a protection control state, the oil return set time is a second preset oil return time period,

wherein the second predetermined oil return time period is less than the first predetermined oil return time period.

8. A refrigeration chiller as set forth in claim 5 wherein when said compressor is operating in said run oil return mode, said oil return control method further comprises:

detecting the current oil return time;

judging whether the oil return process of the compressor is interrupted or not;

when the oil return process is interrupted, restarting the compressor after a first preset time period;

after the compressor is restarted and enters the operation stage for a second predetermined operation time period, the compressor is operated at the oil return frequency for a third predetermined oil return time period,

and the sum of the third preset oil return time period and the current oil return time period is equal to the oil return set time period.

9. A method of oil return control for a refrigeration and freezing assembly as claimed in claim 1, further comprising:

setting a plurality of frequency intervals and an operation duration threshold corresponding to each frequency interval;

judging the frequency interval in which the real-time running frequency falls;

determining the corresponding running time threshold value based on the frequency interval;

comparing the corresponding accumulated running time with the corresponding running time threshold;

when the corresponding accumulated running time is less than the corresponding running time threshold, the oil return control condition is not met;

and when the corresponding accumulated running time is more than or equal to the corresponding running time threshold, the oil return control condition is met.

10. A refrigerator-freezer unit, characterized in that the refrigerator-freezer unit comprises a variable frequency compressor and that the refrigerator-freezer unit controls the oil return of the compressor using the oil return control method according to any of claims 1-9.

Technical Field

The invention relates to the technical field of refrigeration, in particular to an oil return control method of a refrigeration and freezing unit and the refrigeration and freezing unit.

Background

In the modern industrial and agricultural production process, the refrigerating and freezing unit can provide effective temperature control, so that the production efficiency and the product quality are continuously improved, and therefore, the refrigerating and freezing unit is widely applied to the fields of food processing, mechanical manufacturing, medicine production, grain storage and the like. Refrigeration and freezing units, including but not limited to water-cooled units and air-cooled units, may be used to cool refrigerators directly with a refrigerant (also referred to as "refrigerant") to provide suitable refrigeration and/or freezing temperatures. Some refrigeration and freezing units employ a vapor compression refrigeration cycle, such as using a screw compressor or scroll compressor. The refrigeration and freezing unit further includes at least a condenser, an evaporator, and an expansion device. The refrigerating-freezing unit can be divided into two parts, an outdoor unit (which is usually placed in an outdoor environment) and an indoor unit (which is usually placed in an indoor environment to be temperature-regulated, for example a cold storage) which are interconnected with each other. The compressor and the condenser are disposed in the outdoor unit, and the evaporator and the expansion device are disposed in the indoor unit. In the refrigeration cycle, the compressor sucks a low-temperature and low-pressure gaseous refrigerant through the suction port and compresses the refrigerant into a high-temperature and high-pressure gaseous refrigerant. The high-temperature and high-pressure gaseous refrigerant is discharged from a discharge port of the compressor and flows into the condenser along a pipe. In the condenser, a high-temperature and high-pressure gaseous refrigerant is condensed into a medium-temperature and high-pressure liquid refrigerant by means of an air cooling or water cooling method. The medium-temperature high-pressure liquid refrigerant flows from the condenser to the expansion device along the pipeline, and is throttled in the expansion device into low-temperature low-pressure liquid refrigerant. Then, the low-temperature low-pressure liquid refrigerant flows along the pipeline to the evaporator. In the evaporator, the liquid refrigerant is evaporated into a low-temperature and low-pressure gaseous refrigerant by absorbing heat of the indoor air, and the indoor air is cooled to a predetermined target refrigerating temperature or a target freezing temperature. The low-temperature and low-pressure gaseous refrigerant is then sucked and compressed again by the compressor, thereby starting a new refrigeration cycle.

The compressor is a core component of the refrigerating and freezing unit, so that ensuring the normal running shape of the compressor is one of important subjects for designing the refrigerating and freezing unit. The compressor needs a sufficient amount of oil during operation to ensure lubrication of the internal components. However, when the compressor discharges air, part of the lubricating oil flows in the refrigeration cycle circuit along with the refrigerant. Particularly, when the compressor operates at low frequency, the circulation flow in the refrigeration system is small, the flow rate of the refrigerant is low, and lubricating oil in the refrigerant can be deposited in components such as a heat exchanger, a gas-liquid separator and a pipeline, so that the compressor operates in an oil-deficient state. If the compressor is in an oil shortage state for a long time, the compressor is abraded, the motor is burnt and the like. In order to ensure that a sufficient amount of oil is available during operation of the compressor, it is common practice in the prior art to increase the operating frequency during normal operation of the compressor, thereby bringing the lubricant back into the interior of the compressor. However, the compressor may be stopped during operation for various reasons (for example, a shutdown protection is triggered, a user malfunctions or the indoor temperature reaches a target temperature set by the user), so as to affect the oil return process.

Accordingly, there is a need in the art for a new solution to the above problems.

Disclosure of Invention

In order to solve the above problems in the prior art, that is, to solve the technical problem in the prior art that the oil cannot be returned smoothly due to the interruption of the operation of the compressor, the present invention provides an oil return control method for a refrigeration and freezing unit. The oil return control method comprises the following steps:

detecting the real-time running frequency and the corresponding accumulated running time of a compressor of the refrigerating and freezing unit;

judging whether the compressor meets an oil return control condition or not based on the real-time running frequency and the corresponding accumulated running duration;

and when the oil return control condition is met, controlling the compressor to implement an oil return operation mode under the condition that the restarting time of the compressor is less than the preset time.

As can be understood by those skilled in the art, in the oil return control method for the refrigeration and freezing unit, the real-time operation frequency and the corresponding accumulated operation duration of the compressor are detected, and then whether the compressor meets the oil return control condition is judged based on the measured real-time operation frequency and the corresponding accumulated operation duration. And when the oil return control condition is met, controlling the compressor to implement an oil return operation mode under the condition that the restarting time of the compressor is less than the preset time. When the restart times of the compressor is less than the preset times, the operation of the compressor is normal, or the compressor is normally operated after the restart although the compressor is interrupted due to some reason, so that the compressor is controlled to implement an operation oil return mode for oil return, the compressor is prevented from operating in an oil shortage state for a long time, and the service life of the compressor is prolonged.

In a preferred technical solution of the oil return control method for a refrigeration and freezing unit, when the oil return control condition is satisfied, the step of controlling the compressor to implement an oil return operation mode under a condition that the restart time of the compressor is less than a predetermined time includes:

judging whether the compressor is in a starting stage or an operating stage;

when the compressor is in a starting stage, judging whether the starting stage is interrupted, when the starting stage is not interrupted, after the starting stage is finished, the compressor enters the operation stage at a first operation frequency, and after a first preset operation time period, controlling the compressor to enter an operation oil return mode; when the starting phase is interrupted, restarting the compressor for the first time after a preset restart interval time period, wherein the restart count is 1;

judging whether the first restart is interrupted or not after the compressor is restarted for the first time, entering the operation stage at the first operation frequency after the first restart is finished when the first restart is not interrupted, and controlling the compressor to enter the operation oil return mode after the first preset operation time period; restarting the compressor a second time and a restart count of 2 after the predetermined restart interval period has elapsed while the first restart was interrupted;

and controlling the compressor to implement an oil return operation mode under the condition that the restarting times of the compressor are less than 2. The first interruption of the compressor during the start-up phase may be due to a compressor malfunction. If the compressor is not interrupted after the first restart and can still normally operate after the first preset operation time period, it indicates that the refrigeration and freezing unit and the compressor are both in a normal state, so that oil return can be performed after the compressor enters an operation stage and operates for the first preset operation time period (to ensure that the compressor enters a stable operation state), and therefore the operation is called as an oil return operation mode.

In a preferred technical solution of the oil return control method for the refrigerating and freezing unit, when the compressor is in an operation stage, it is determined whether the operation stage is interrupted, and when the operation stage is not interrupted, the compressor is controlled to enter the operation oil return mode after the first predetermined operation time period elapses; when the running stage is interrupted, restarting the compressor for the first time after a preset restart interval time period, wherein the restart count is 1;

judging whether the first restart is interrupted or not after the compressor is restarted for the first time, entering the operation stage at the first operation frequency after the first restart is finished when the first restart is not interrupted, and controlling the compressor to enter the operation oil return mode after the first preset operation time period; restarting the compressor a second time and a restart count of 2 after the predetermined restart interval period has elapsed while the first restart was interrupted;

and controlling the compressor to implement the operation oil return mode under the condition that the restarting times of the compressor are less than 2 times. The first interruption of the compressor during the operating phase may be due to a compressor malfunction. If the compressor is not interrupted after the first restart and can still normally operate after the first preset operation time period, the refrigerating and freezing unit and the compressor are in a normal state, and therefore the compressor can be controlled to implement an operation oil return mode.

In a preferable technical solution of the oil return control method for a refrigeration and freezing unit, after the first predetermined operation time period elapses, the step of controlling the compressor to enter the operation oil return mode includes:

comparing the first operating frequency with a preset oil return frequency;

when the first operating frequency is greater than the preset oil return frequency, the compressor operates at an oil return frequency equal to the first operating frequency to return oil;

and when the first operating frequency is less than or equal to the preset oil return frequency, the compressor operates at the oil return frequency equal to the preset oil return frequency to return oil. The preset oil return frequency is set based on the actual configuration of the refrigeration system, experimental data of oil return control, and the like. The real-time running frequency (namely the first running frequency) when the compressor enters the running oil return mode is compared with the preset oil return frequency, and the larger frequency between the first running frequency and the preset oil return frequency is selected as the oil return frequency of the compressor, so that the oil return requirement can be met, the large influence on the running of a refrigeration system can be avoided, and the running of the compressor is more stable.

In a preferable technical solution of the oil return control method for a refrigeration and freezing unit, after the first predetermined operation time period elapses, the step of controlling the compressor to enter the operation oil return mode further includes:

detecting an operation state of the compressor;

determining an oil return set time length based on the running state of the compressor;

and controlling the compressor to run at the oil return frequency and continuously for the oil return set time.

In the preferable technical scheme of the oil return control method of the refrigerating and freezing unit, after the set oil return time period, the oil return control method clears each accumulated operation time period and ends oil return so as to count again.

In the preferable technical scheme of the oil return control method of the refrigerating and freezing unit, when the running state of the compressor is the normal running state, the oil return set time is a first preset oil return time period; and is

When the running state of the compressor is a protection control state, the oil return set time is a second preset oil return time period,

wherein the second predetermined oil return time period is less than the first predetermined oil return time period. When the compressor enters the operation oil return mode, the compressor may be in a normal operation state or a protection control state. When the compressor is in the protection control state, the risk of abnormal operation of the compressor is indicated. In order to ensure that the compressor can timely return oil and prevent the compressor from operating for a long time in an oil shortage state, the compressor is controlled to carry out short-time oil return in a protection control state (compared with the oil return time in a normal operation state), and the basic oil return requirement of the compressor can be ensured.

In a preferred embodiment of the oil return control method for a refrigeration and freezing unit, when the compressor operates in the operation oil return mode, the oil return control method further includes:

detecting the current oil return time;

judging whether the oil return process of the compressor is interrupted or not;

when the oil return process is interrupted, restarting the compressor after a first preset time period;

after the compressor is restarted and enters the operation stage for a second predetermined operation time period, the compressor is operated at the oil return frequency for a third predetermined oil return time period,

and the sum of the third preset oil return time period and the current oil return time period is equal to the oil return set time period. When the compressor runs in the oil return running mode, if the oil return process is interrupted, the compressor is controlled to restart, and oil return is continued so as to meet the requirement of oil return setting time.

In a preferable technical solution of the oil return control method of the refrigeration and freezing unit, the oil return control method further includes:

setting a plurality of frequency intervals and an operation duration threshold corresponding to each frequency interval;

judging the frequency interval in which the real-time running frequency falls;

determining the corresponding running time threshold value based on the frequency interval;

comparing the corresponding accumulated running time with the corresponding running time threshold;

when the corresponding accumulated running time is less than the corresponding running time threshold, the oil return control condition is not met;

and when the corresponding accumulated running time is more than or equal to the running time threshold corresponding to the frequency interval, the oil return control condition is met. Whether the actual operation of the compressor meets the oil return condition or not is judged by setting a plurality of frequency intervals and the operation time length threshold corresponding to each frequency interval, so that the condition of oil return control of the compressor is more in line with the actual requirement.

In order to solve the above problems in the prior art, that is, to solve the technical problem in the prior art that the oil return cannot be smoothly performed when the operation of the compressor is interrupted, the present invention further provides a refrigeration and freezing unit, wherein the refrigeration and freezing unit comprises a variable frequency compressor, and the refrigeration and freezing unit controls the oil return of the compressor by using the oil return control method according to any one of the above. By using the control method, the refrigeration and freezing unit can realize smooth oil return under the condition that the operation of the compressor is interrupted, so that the service life of the compressor is prolonged.

Drawings

Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

FIG. 1 is a system schematic of an embodiment of the refrigeration chiller of the present invention;

fig. 2 is a flow chart of an oil return control method of the refrigerating and freezing unit of the invention;

fig. 3 is a first partial flowchart of an embodiment of an oil return control method of a refrigeration and freezing unit according to the present invention;

fig. 4 is a second partial flowchart of the oil return control method of the refrigeration and freezing unit according to the embodiment of the invention.

List of reference numerals:

1. a refrigeration and freezing unit; 11. an outdoor unit; 111. a compressor; 111a, compressor heating belt; 112a, an exhaust pipe; 112b, liquid pipe; 112c, a gas pipe; 112d, an air suction pipe; 113. a high voltage protection switch; 114. an oil separator; 115. an oil return capillary tube; 116. a one-way valve; 117. a high pressure sensor; 118. an outdoor heat exchanger; 119. a high pressure reservoir; 119a, a high-pressure reservoir heating belt; 120. drying the filter; 121. a liquid viewing mirror; 122. a liquid pipe stop valve; 123. an air pipe stop valve; 124. a gas-liquid separator; 125. a low pressure sensor; 126. a hot defrosting bypass pipeline; 127. a hot defrosting stop valve; 128. an outdoor balanced bypass line; 129. an outdoor bypass electromagnetic valve; 21. an indoor unit; 211. an indoor heat exchanger; 212. an expansion valve; 213. an indoor solenoid valve.

Detailed Description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.

The invention provides an oil return control method of a refrigeration and freezing unit, aiming at solving the technical problem that oil cannot be returned smoothly when the compressor is interrupted in the prior art. The oil return control method comprises the following steps:

detecting the real-time operation frequency and the corresponding accumulated operation time of a compressor of the refrigerating and freezing unit (step S1);

judging whether the compressor meets an oil return control condition or not based on the real-time operation frequency and the corresponding accumulated operation duration (step S2);

when the oil return control condition is satisfied, the compressor is controlled to implement the operation oil return mode under the condition that the restart number of the compressor is less than the predetermined number of times (step S3).

Figure 1 is a system schematic of an embodiment of a refrigeration and freezing assembly of the present invention. As shown in fig. 1, in one or more embodiments, the refrigeration-freezer unit 1 includes an outdoor unit 11 (which is typically disposed in an outdoor environment) and one indoor unit 21 (which is typically disposed indoors or in a room). Alternatively, the refrigerating-freezing unit 1 may be provided with a plurality of parallel-connected indoor units, for example two, three, four or another suitable number of indoor units. Fig. 1 shows only one indoor unit 21. In the case where a plurality of indoor units are arranged, the arrangement of the plurality of indoor units may be the same or different depending on actual needs.

As shown in fig. 1, in one or more embodiments, the outdoor unit 11 mainly includes a compressor 111, an outdoor heat exchanger 118, a high-pressure accumulator 119, and a gas-liquid separator 124; the indoor unit 21 mainly includes an indoor heat exchanger 211, an expansion valve 212, and an indoor solenoid valve 213. The compressor 111 has a discharge port and a suction port (not shown). The discharge port of the compressor 111 is connected to the input end of the outdoor heat exchanger 118 through a discharge pipe 112 a; the output end of the outdoor heat exchanger 118 is connected to the high-pressure reservoir 119, the expansion valve 212 of the indoor unit 21, and the indoor heat exchanger 211 in this order through the liquid pipe 112 b; the indoor heat exchanger 211 is connected to an inlet of the gas-liquid separator 124 through a gas pipe 112c, and an outlet of the gas-liquid separator 124 is connected to an inlet of the compressor 111 through a suction pipe 112d, thereby being interconnected to form a refrigeration cycle allowing a refrigerant to flow therein.

As shown in FIG. 1, in one or more embodiments, the compressor 111 is an inverter compressor. Alternatively, the compressor 111 may include two or more compressors in parallel. These compressors may be all inverter compressors or may include some inverter compressors. In one or more embodiments, a high pressure protection switch 113 is disposed on the discharge line 112a near the discharge of the compressor 111 to provide shutdown protection when the discharge pressure of the compressor 111 is too high. In one or more embodiments, an oil separator 114 is disposed on the gas discharge pipe 112a, wherein a gas input end of the oil separator 114 is connected to a gas discharge port of the compressor 111; the gas output of the oil separator 114 is connected to the input of the outdoor heat exchanger 118 through the gas discharge pipe 112 a; the oil return discharge end of the oil separator 114 is connected to an oil return capillary tube 115 and is connected to the suction port of the compressor 111 through a pipe so as to return the lubricating oil to the compressor 111 in time. In one or more embodiments, a compressor heating zone 111a is provided at the bottom of the compressor 111 to preheat the compressor when needed. In one or more embodiments, a check valve 116 for preventing the refrigerant from flowing backwards and a high pressure sensor 117 for detecting the discharge pressure of the compressor 111 are further disposed on the discharge pipe 112a, and both the check valve 116 and the pressure sensor 117 are located downstream of the gas output end of the oil separator 114.

As shown in fig. 1, in one or more embodiments, the outdoor heat exchanger 118 may be, but is not limited to, a finned coil heat exchanger or a plate heat exchanger, and is equipped with an outdoor heat exchanger fan (not shown). The high pressure accumulator 119 may receive the liquid refrigerant condensed by the outdoor heat exchanger 118 to adjust and ensure a refrigerant circulation amount in the refrigeration system. In one or more embodiments, a high pressure accumulator heating belt 119a is provided on the high pressure accumulator 119 to preheat the liquid refrigerant, ensuring accurate supply of the refrigerant. A dry filter 120, a sight glass 121, and a liquid pipe shutoff valve 122 are also connected in series in this order to the liquid pipe 112b downstream of the high-pressure accumulator 119. The desiccant filter 120 may dry moisture in the liquid refrigerant, the liquid viewing mirror 121 may be used to observe a flow condition of the liquid refrigerant and detect a water content in the refrigerant, and the liquid tube stop valve 122 may help to temporarily store the refrigerant in the refrigeration cycle loop outside the room, so as to facilitate assembly, disassembly, maintenance and repair of the refrigeration and freezing unit 1. In one or more embodiments, an indoor solenoid valve 213 is further disposed at a position of the liquid pipe 112b upstream of the expansion valve 212 to control the liquid refrigerant to flow into the indoor unit 21.

As shown in fig. 1, in one or more embodiments, the expansion valve 212 is a thermal expansion valve. Alternatively, the expansion valve 212 may be an electronic expansion valve, or other suitable expansion valve. The indoor heat exchanger 211 includes, but is not limited to, a fin-and-coil heat exchanger or a plate heat exchanger, and is provided with an indoor heat exchanger fan (not shown in the drawings). The gas pipe 112c is further provided with a gas pipe shutoff valve 123 to assist the refrigerant in the refrigeration cycle circuit to be temporarily stored outside the room in cooperation with the liquid pipe shutoff valve 122.

As shown in fig. 1, in one or more embodiments, a low pressure sensor 125 is further disposed on the suction pipe 112d to detect a suction pressure of the compressor 111. In one or more embodiments, a hot defrosting bypass line 126 is connected in parallel between the gas output end close to the oil-gas separator 114 and the output end of the indoor heat exchanger 211, and a hot defrosting stop valve 127 is arranged on the hot defrosting bypass line 126, so that when the indoor heat exchanger 211 needs defrosting, the hot defrosting stop valve 127 is opened, and the high-temperature and high-pressure gaseous refrigerant output from the exhaust port of the compressor 111 is allowed to be directly delivered to the indoor heat exchanger 211 through the hot defrosting bypass line 126 for defrosting treatment. In one or more embodiments, an outdoor balance bypass line 128 is connected in parallel between the exhaust pipe 112a and the suction pipe 112d, and an outdoor bypass solenoid valve 129 is disposed on the outdoor balance bypass line 128.

When the refrigerating and freezing unit 1 receives a cooling instruction, the compressor 111 starts to operate, and the refrigerant (for example, R410a) is compressed by the compressor 111 and then enters the outdoor heat exchanger 113 (which serves as a condenser) through the exhaust pipe 112a in the form of a high-temperature and high-pressure gas. In the outdoor heat exchanger 113, the high-temperature and high-pressure gas refrigerant is condensed into a high-temperature and high-pressure liquid refrigerant by transferring heat to an air flow caused by the outdoor heat exchanger fan. The high-temperature and high-pressure liquid refrigerant flows through the high-pressure accumulator 119, the dry filter 120, the liquid scope 121, and the liquid tube shutoff valve 122 in this order, and flows to the expansion valve 212 of the indoor unit 21. The expansion valve 212 throttles the high-temperature and high-pressure liquid refrigerant to a low-temperature and low-pressure liquid refrigerant, and distributes the refrigerant to the indoor heat exchanger 211. The low-temperature and low-pressure liquid refrigerant is evaporated into a low-temperature and low-pressure gas refrigerant by absorbing heat of the indoor air, and the indoor air is cooled. The low-temperature and low-pressure gaseous refrigerant exits the indoor heat exchanger 211, passes through the corresponding gas pipe 112c and the gas pipe shutoff valve 123, and then enters the gas-liquid separator 124. The gas-liquid separated refrigerant gas is sucked into the compressor 111 through the suction port. A complete refrigeration cycle is completed and such refrigeration cycle can be performed without interruption in order to achieve the target refrigeration temperature.

The oil return control method of the refrigerating and freezing unit of the present invention will be described in detail based on the refrigerating and freezing unit 1. It should be noted that the oil return control method of the present invention can also be used in other suitable refrigeration equipment.

Fig. 2 is a flow chart of an oil return control method of the refrigeration and freezing unit. As shown in fig. 2, after the oil return control method of the refrigeration and freezing unit 1 is started, step S1 is executed to detect the real-time operating frequency f of the compressor 111 of the refrigeration and freezing unit 1_yAnd a corresponding cumulative operating time t_y. Based on real-time operating frequency f_yAnd a corresponding cumulative operating time t_yThen, it is determined whether or not the compressor 111 satisfies the oil return control condition (step S2). When the oil return control method is satisfied, the compressor 111 is controlled to implement the operation oil return mode under the condition that the number of restarts of the compressor 111 is less than the predetermined number N of times (step S3). In one or more embodiments, the predetermined number of times N is 2. Alternatively, the predetermined number of times N may be set to other suitable numbers more than 2, such as 3, 4, etc., depending on the actual conditions of the refrigeration-freezer unit 1.

Fig. 3 is a first partial flowchart of an embodiment of an oil return control method of a refrigeration and freezing unit according to the present invention. As shown in fig. 3, after the oil return control method of the refrigeration and freezing unit 1 is started, step S10 is executed, that is, a plurality of frequency intervals and an operation time period threshold corresponding to each frequency interval are set. The plurality of frequency intervals may be determined according to a frequency range of the compressor 111. In one or more embodiments, the plurality of frequency intervals include a first frequency interval a, a second frequency interval B, and a third frequency interval C, wherein the first frequency interval a is less than 30Hz (hertz), the second frequency interval B is greater than or equal to 30Hz and less than 60Hz, the third frequency interval C is greater than or equal to 60Hz, and corresponds to the operating duration threshold t of the first frequency interval a_aIs 4h (hours), corresponding to the threshold value t of the operating duration of the second frequency interval B_b8h, corresponding to the operating time threshold of the third frequency interval CValue t_cIs 16 h. The number of frequency bins may be set to other suitable numbers more or less than 3. Further, the specific range of each frequency interval can also be adjusted according to actual needs. Furthermore, the operation duration threshold corresponding to each frequency interval may also be adjusted according to actual needs. Then, the oil return control method proceeds to step S11 of detecting the real-time operation frequency f of the compressor 111 of the refrigerating and freezing unit 1_y. Then, the real-time operation frequency f is judged_yThe frequency bin in which it falls (step S12). In determining the real-time operating frequency f_yAfter the falling frequency interval, the control method proceeds to step S13, where a corresponding operating duration threshold is determined based on the falling frequency interval. In one or more embodiments, the real-time operating frequency f of the compressor 111 is measured_y55Hz, the real-time operating frequency f_yFalls within the second frequency interval B, thus corresponding to the threshold value t of the operating duration_bIs 8 h. In determining the real-time operating frequency f_yAfter the falling frequency interval, the oil return control method also proceeds to step S14, in which the accumulated operation time t of the compressor 111 in the falling frequency interval is obtained_y. Then, the control method proceeds to step S20 to acquire the accumulated operating time period t_yAnd comparing with the running time threshold corresponding to the frequency interval. It should be noted that the compressor 11 is in operation, at a frequency f of operation in real time_yIs adjusted in accordance with the load in the refrigeration system and the difference between the actual and target evaporating temperatures, the real-time operating frequency fy is varied, but rarely is a fixed value. Whether the compressor 111 meets the oil return condition or not is judged by setting a plurality of frequency intervals and presetting the operation time length threshold value corresponding to each frequency interval, so that the oil return opportunity can better meet the actual requirement. When each accumulated running time t_yIf the detected values are less than the threshold value of the operation duration corresponding to the frequency interval, which indicates that the oil return control condition is not satisfied (step S22), the real-time operation frequency f of the compressor 111 is repeatedly detected_yStep S11. When any one of the accumulated operation time lengths t_yWhen the frequency interval is larger than or equal to the running time length threshold corresponding to the falling frequency interval, the fact that the running time length threshold is larger than or equal to the running time length threshold corresponding to the falling frequency interval indicates that the running time length is already at the momentWhen the oil return control condition is satisfied (step S21), the compressor 111 is already in a state in which oil return is possible.

Fig. 4 is a second partial flowchart of the oil return control method of the refrigeration and freezing unit according to the embodiment of the invention. As shown in fig. 4, when the oil return control condition has been satisfied by the compressor 111, step S30 is executed, i.e., the operation stage of the compressor 111 is determined. It should be noted that the compressor 111 first enters the start-up phase after starting up. In the starting stage, the starting frequency of the compressor 111 will gradually increase from zero to the starting target frequency f according to a preset program_q. When the compressor 111 is at the start-up target frequency f_qContinuously running for a preset time period t_sAfter that, the start-up phase is ended and the compressor 111 enters the run phase. In one or more embodiments, the target frequency f is initiated_qIs 42Hz, and a preset time period t_sIt was 3min (min). Alternatively, the target frequency f is started_qCan be set to any value between (40Hz-60Hz), such as 40Hz, 45Hz, etc. Further, a preset time period t_sSet to be longer or shorter than 3min or other suitable time.

As shown in FIG. 4, when it is detected that the compressor 111 is in the operation stage (step S50), step S51 is performed to control the compressor 111 to operate at the first operation frequency f_y1And (5) operating. It will be appreciated that the first operating frequency f_y1Is automatically adjusted by the compressor 111 according to the load of the refrigeration system and other factors. It is then determined whether the compressor 111 is interrupted in the operation stage (step S52). If the operating phase is not interrupted, a first predetermined operating time t has elapsed_y1After that, the compressor 111 enters the oil return operation mode (step S53). In one or more embodiments, the first preset operating time period t_y1It is 5 min. Alternatively, the first preset operating period t_y1Other suitable times longer or shorter than 5min may be provided. The compressor 111 operates at a first operating frequency f_y1Operating for a first preset operating time period t_y1Without interruption, the compressor 111 is in a stable operation state, and all conditions for oil return are met. Thus, step S54 and step S55 are performed, respectively. In particular, based on the first operating frequency f_y1And preset oil returnFrequency f_sDetermining the oil return frequency f as a result of the comparison_o(step S54). When the first operating frequency f_y1Greater than a predetermined oil return frequency f_sTime, oil return frequency f_oEqual to the first operating frequency f_y1(ii) a When the first operating frequency f_y1Less than or equal to the preset oil return frequency f_sTime, oil return frequency f_oEqual to the preset oil return frequency f_s. Meanwhile, the oil return setting time period t is determined based on the operation state of the compressor 111_o(step S55). When the compressor 11 is in a normal operation state, the oil return setting time period t_oIs equal to the first preset oil return time period t_h1(ii) a When the compressor 11 is in the protection control state, the oil return setting time period t_oIs equal to the second preset oil return time period t_h2Wherein the second predetermined oil return time period t_h2Is less than the first preset oil return time period t_h1. In one or more embodiments, the first predetermined oil return time period t_h1Is 5min, and a second predetermined oil return time period t_h2Is 3 min. Alternatively, the first predetermined oil return time period t_h1Other suitable times longer or shorter than 5min may be provided. Further, a second predetermined oil return time period t_h2Other suitable times longer or shorter than 3min may also be provided. It is understood that when the compressor 111 is in the protection control state, it indicates that there is a risk of abnormal operation of the compressor 111 (at which time the compressor 111 has not triggered the protection shutdown). In order to ensure that the compressor 111 can return oil in time and prevent the compressor 111 from operating for a long time in an oil shortage state, the compressor 111 is controlled to return oil for a short time in a protection control state as long as the basic oil return requirement of the compressor 111 can be ensured. Determining good oil return frequency f_oAnd a set oil return time period t_oThen, the compressor 111 is controlled to return oil at the frequency f_oThe oil is returned (step S56). Control then continues to step S57 where it is determined whether the oil return process is interrupted. If the oil return process is not interrupted, which indicates that the oil return of the compressor 111 is smooth, the set time t for the oil return operation is reached_oThen, the oil return is finished, and each accumulated running time t is_yZero clearing (step S62). If the oil return process is interrupted, step S58 is executed to obtain the current oil return processTime t of oil return_hd. The compressor 111 is then controlled for a first predetermined time period t₁And then restarts the compressor 111 (step S59). In one or more embodiments, the first predetermined time period t₁Is 3 min. Alternatively, the first predetermined period of time t₁Other suitable times, longer or shorter than 3min, may be provided. After the start-up phase is finished, the compressor 111 is controlled to continuously operate for a second predetermined time period t₂(step S60). In one or more embodiments, the second predetermined time period t₂Is 2 min. Alternatively, the second predetermined period of time t₂Other suitable times longer or shorter than 2min may be provided. Over a second predetermined period of time t₂After that, the compressor 111 is stably operated again, step S61 is executed, i.e. the compressor 111 is controlled to return the oil frequency f_oRunning a third predetermined oil return time period t_h3Wherein the third predetermined oil return time period t_h3The current oil return time t_hdThe sum is equal to the set oil return time t_o. In other words, when the oil return process is interrupted, the compressor 111 is controlled to return oil at the original frequency f_oContinuing to operate to enable the sum of the first oil return time and the second oil return time to reach the oil return set time t_oSo as to smoothly complete the whole oil return process. When the oil return process is finished, each accumulated operation time t is_yZero clearing (step S62).

As shown in fig. 4, when the compressor 111 is detected to be in the starting stage (step S31), step S32 is executed to determine whether the compressor 111 is interrupted in the starting stage (step S32). If the compressor 111 is interrupted during the start-up phase, step S33 is executed, i.e. a predetermined restart interval time period t elapses_cAfter that, the compressor 111 is restarted for the first time and the restart count is 1. In one or more embodiments, the restart interval period t is predetermined_cIs 3 min. Alternatively, the restart interval period t is predetermined_cOther suitable times longer or shorter than 3min may also be provided. Next, it is determined whether the first restart is interrupted (step S34). If the start-up of the compressor 111 is not interrupted during the first restart, the control method proceeds to step S40, i.e. after the start-up phase has ended, the compressor 111 enters the run phase. If it is in the first placeWhen the start of the compressor 111 is again interrupted during one restart, step S35 is performed, i.e., a predetermined restart interval period t elapses_cAfter that, the compressor 111 is restarted for the second time and the restart count is 2. Then, step S36 is executed to control the compressor 111 to set the oil return frequency f_sAs a start-up target frequency f_qA second restart is performed. It is understood that the compressor 111 is interrupted during the start-up phase, and may be interrupted under normal conditions (e.g., the accuracy of the indoor target temperature is too high, etc.), or may be shut down for protection under abnormal conditions (e.g., the exhaust temperature of the compressor 111 is too high, etc.). Therefore, when the compressor 111 is interrupted at the start-up stage, the compressor 111 is first controlled to restart for the first time. If the compressor 111 is started normally after the first restart, the compressor operates for oil return after stable operation. If the compressor 111 is interrupted again after the first restart, it means that the compressor 111 may be in an abnormal condition, and therefore oil return needs to be performed at the start stage to achieve smooth oil return. The control method proceeds to step S37, i.e., it is determined whether the compressor 111 is interrupted at the second restart. If the compressor 111 is not interrupted during the second restart, which indicates that the compressor 111 is normally started and smoothly returns oil during the second restart, step S38 is executed to accumulate the operation time t_yAnd clearing to zero to finish oil return. If the compressor 111 is interrupted again when the second restart occurs, which means that the compressor 111 cannot be started normally, and smooth oil return cannot be performed in the starting stage, step S39 is executed to issue a fault alarm for the compressor 111.

As shown in fig. 4, when the compressor 111 is in the start-up phase, in performing step S32, if it is determined that the start-up phase is not interrupted, the control method proceeds to step S40, i.e., after the start-up phase is over, the compressor 111 enters the run phase. Next, the control method proceeds to step S51, i.e., the compressor 111 is controlled to operate at the first operating frequency f_y1And (5) operating.

As shown in fig. 4, if it is determined that the operation phase is interrupted while the compressor 111 performs the step S52, the step S63 of acquiring the restart count of the current compressor 111 is performed. In one or more embodimentsThe predetermined number of times N is 2, when the number of restarts is equal to 0, the control method proceeds to step S33, i.e., the predetermined restart interval period t elapses_cAfter that, the compressor 111 is restarted for the first time and the restart count is 1. When the number of restarts is equal to 1, the control method proceeds to step S35, i.e., a predetermined restart interval period t elapses_cAfter that, the compressor 111 is restarted for the second time and the restart count is 2. It is to be understood that when the predetermined number of times N is 3, the control method proceeds to step S33 when the number of restarts is equal to 0 or 1, and proceeds to step S35 when the number of restarts is equal to 2.

So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the invention, a person skilled in the art may combine technical features from different embodiments, and may make equivalent changes or substitutions for related technical features, and such changes or substitutions will fall within the scope of the invention.