Air conditioner and control method thereof

Abstract

The invention provides an air conditioner and a control method thereof.The air conditioner comprises a refrigerant circulation loop, an oil level sensor and a controller, and the oil level sensor is arranged in an oil pool at the bottom of a compressor and used for detecting the oil level height of the oil pool; the controller is configured to periodically obtain the current oil level height and the current operation frequency of the compressor after the compressor is started, and control the operation frequency of the compressor in the next period and the opening degree of the electronic expansion valve in the next period according to the first oil level height in the current period and the first operation frequency of the compressor. Therefore, the viscosity and the oil quantity of the lubricating oil in the oil pool of the compressor are ensured, parts of the compressor can be lubricated by enough lubricating oil, the situation of empty burning of the compressor due to oil shortage is avoided, and the reliability of low-temperature operation of the air conditioner is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to an air conditioner and a control method thereof. Background Art

[0002] An air conditioner is an electrical appliance product widely used in people's lives. The air conditioner plays an important role in regulating the indoor temperature, can provide a healthy and comfortable indoor environment for users, and meet the normal work, life and learning needs.

[0003] Currently, during the use of an air conditioner, it is greatly affected by changes in the ambient temperature and user usage conditions. On the one hand, when the ambient temperature is relatively low (below -25°C) and the air conditioner has been shut down for a long time, the oil pool temperature at the bottom of the compressor is relatively low, the viscosity of the refrigeration oil is relatively large, and the refrigerant also migrates from the high-temperature condenser to the oil pool of the compressor. At this time, if the compressor starts, since the temperature at the bottom of the compressor is lower than the condensation temperature, the refrigerant discharged from the compressor will condense and fall back into the compressor oil pool from the compressor cavity, thereby diluting the oil, causing the compressor to lack oil, resulting in wear of the compressor components, and even burning out the compressor. On the other hand, when a variable-frequency air conditioner is operating, due to frequency changes, during the change process of the electronic expansion valve, the opening degree of the electronic expansion valve is too large, and too much oil is sprayed out and cannot be recovered. Or if the variable-frequency air conditioner operates at a low frequency for a long time, it will also cause the oil to be sprayed out and cannot be recovered, finally resulting in a lack of oil. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art.

[0005] To this end, an object of the present invention is to provide an air conditioner that can ensure the viscosity and oil volume of the lubricating oil in the compressor oil pool, enable the components of the compressor to have sufficient lubricating oil for lubrication, avoid the situation of the compressor running dry due to lack of oil, and improve the reliability of the air conditioner during low-temperature operation.

[0006] To this end, a second object of the present invention is to provide a control method for an air conditioner.

[0007] To achieve the above object, an embodiment of the first aspect of the present invention provides an air conditioner, which includes: a refrigerant circulation circuit that enables the refrigerant to perform a refrigeration cycle in a circuit composed of a compressor, a condenser, an electronic expansion valve, and an evaporator, where one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger; the electronic expansion valve is disposed between the condenser and the evaporator, and is configured to increase the flow resistance of the refrigerant passing through the electronic expansion valve when its opening degree decreases, and decrease the flow resistance of the refrigerant passing through the electronic expansion valve when its opening degree increases; an oil level sensor is disposed in the oil sump at the bottom of the compressor for detecting the oil level height of the oil sump; the controller is configured to: after the compressor starts, periodically obtain the current oil level height and the current operating frequency of the compressor, and control the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first oil level height and the first operating frequency of the compressor in the current cycle, until the operating frequency of the compressor in the current cycle reaches the target operating frequency.

[0008] For the air conditioner according to the embodiment of the present invention, during the process from the air conditioner being turned on to the compressor reaching the target operating frequency, the operating frequency of the compressor and the opening degree of the electronic expansion valve can be controlled according to the detected oil level height and the current operating frequency of the compressor to control the amount of lubricating oil in the oil sump of the compressor and adjust the refrigerant state of the compressor's suction gas, so as to ensure the viscosity and amount of lubricating oil in the oil sump of the compressor, enable the components of the compressor to have sufficient lubricating oil for lubrication, avoid the situation of the compressor running dry due to lack of oil, and improve the reliability of the air conditioner during low-temperature operation.

[0009] In some embodiments, when controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first oil level height in the current cycle and the first operating frequency of the compressor, the controller is specifically configured as follows: if the first oil level height is less than the first preset height, control the operating frequency of the compressor in the next cycle to decrease by the first preset frequency, and control the opening degree of the electronic expansion valve in the next cycle to remain unchanged; if the first oil level height is greater than the first preset height but not greater than the second preset height, and it is determined that the first oil level height is in a downward trend in the current cycle, then control the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first operating frequency of the compressor, where the second preset height is greater than the first preset height; if the first oil level height is greater than the first preset height, and it is determined that the first oil level height is not in the downward trend in the current cycle; or, if the first oil level height is greater than the second preset height, and it is determined that the first oil level height is in the downward trend in the current cycle, then after delaying for the first preset time, control the operating frequency of the compressor in the next cycle to increase by the second preset frequency, and control the opening degree of the electronic expansion valve in the next cycle according to the operating frequency of the compressor in the next cycle.

[0010] In some embodiments, when controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first operating frequency of the compressor, the controller is specifically configured as follows: if the first operating frequency of the compressor is greater than the third preset frequency, control the operating frequency of the compressor in the next cycle to remain unchanged, and control the opening degree of the electronic expansion valve in the next cycle to decrease by the preset opening degree; if the first operating frequency of the compressor is not greater than the third preset frequency, control the operating frequency of the compressor in the next cycle to increase by the fourth preset frequency, and control the opening degree of the electronic expansion valve in the next cycle to remain unchanged, where the third preset frequency is less than the target operating frequency, and the fourth preset frequency is greater than the second preset frequency.

[0011] In some embodiments, when determining whether the first oil level height is in the downward trend or not in the downward trend in the current cycle, the controller is specifically configured as follows: in the current cycle, if the oil level height in adjacent moments or adjacent time periods decreases successively, then determine that the first oil level height is in the downward trend in the current cycle, otherwise, determine that the first oil level height is not in the downward trend in the current cycle.

[0012] In some embodiments, after the operating frequency of the compressor reaches the target operating frequency within the current cycle, the controller is further configured to: obtain the current second oil level height in real time; if the second oil level height is less than the first preset height, and the target operating frequency of the compressor is less than the fifth preset frequency and the duration reaches the second preset time, control the operating frequency of the compressor to increase to the sixth preset frequency, and control the opening degree of the electronic expansion valve according to the operating frequency of the compressor until the first preset condition is met, then control the compressor to operate at the target operating frequency, and control the opening degree of the electronic expansion valve to return to the opening value before the frequency increase at a preset decreasing rate, where the first preset condition includes: the time for the compressor to operate at the sixth preset frequency reaches the third preset time, the oil return time of the compressor reaches the fourth preset time, or the compressor shuts down, the second preset time is greater than the fourth preset time, and the fourth preset time is greater than the third preset time.

[0013] In some embodiments, the air conditioner further includes an ambient temperature sensor, an exhaust temperature sensor, a compressor bottom temperature sensor, and a condenser temperature sensor. Before the compressor starts, the controller is further configured to: obtain the current ambient temperature and the power-off duration of the air conditioner; determine the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time; determine whether the air conditioner changes from the power-off state to the power-on state; when it is determined that the air conditioner changes from the power-off state to the power-on state, the power-on time reaches the fifth preset time, a start-up instruction is received, the current ambient temperature is less than the preset ambient temperature, and the exhaust temperature of the compressor reaches the preset exhaust temperature, execute the first preheating control strategy, where the first preheating control strategy includes: control the coil of the compressor to be energized until the time for the coil to be energized reaches the target preheating time, then control the compressor to start; when the air conditioner remains in the power-on state and the current ambient temperature is less than the preset ambient temperature, periodically execute the second preheating control strategy until the second preset condition is met, then control the coil of the compressor to be de-energized, where the second preheating control strategy includes: control the coil of the compressor to be energized, when the time for the coil to be energized reaches the target preheating time, control the coil to be de-energized for the sixth preset time, and obtain the current ambient temperature and the power-off duration again, and determine the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time; the second preset condition includes that the current ambient temperature is not less than the preset ambient temperature, or when the time for the coil to be energized reaches the target preheating time, the temperature at the bottom of the compressor is greater than the temperature of the condenser.

[0014] In some embodiments, when determining the target preheating time according to the current ambient temperature, power-off duration, and a preset minimum preheating time, the controller is specifically configured to:

[0015] T = k×(M 1 - M 2 ) + b×M 2 ;

[0016] where T is the target preheating time, M 1 is the power-off duration, M 2 is the preset minimum preheating time, k is a preset constant determined according to the current ambient temperature, and b is a preset constant.

[0017] In some embodiments, when controlling the opening degree of the electronic expansion valve according to the operating frequency of the compressor, the controller is specifically configured to:

[0018] P = a×F + T a ×d + (T d - T e )×c + L;

[0019] where P is the opening degree of the electronic expansion valve, F is the operating frequency of the compressor, T a is the current ambient temperature, T d is the temperature of the condenser, T e is the temperature at the bottom of the compressor, and a, d, c, and L are preset constants.

[0020] In some embodiments, after the operating frequency of the compressor in the current cycle reaches the target operating frequency, the controller is further configured to: when receiving a shutdown instruction, obtain the second operating frequency of the compressor; and control the compressor to continuously operate for a seventh preset time and then stop operating according to the second operating frequency of the compressor.

[0021] To achieve the above object, an embodiment of the second aspect of the present invention provides a control method for an air conditioner, the method including the following steps: after the compressor starts, periodically obtain the current oil level height and the current operating frequency of the compressor; control the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first oil level height and the first operating frequency of the compressor in the current cycle until the operating frequency of the compressor in the current cycle reaches the target operating frequency.

[0022] According to the control method of the air conditioner according to an embodiment of the present invention, during the process from the air conditioner being turned on to the compressor reaching the target operating frequency, the operating frequency of the compressor and the opening degree of the electronic expansion valve can be controlled according to the detected height of the oil level and the current operating frequency of the compressor, so as to control the amount of lubricating oil in the compressor oil sump and adjust the refrigerant state of the compressor suction gas, ensuring the viscosity and amount of the lubricating oil in the compressor oil sump, enabling the components of the compressor to have sufficient lubricating oil for lubrication, avoiding the situation of the compressor running dry due to lack of oil, and improving the reliability of the air conditioner during low-temperature operation.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0025] Figure 1 is a schematic structural diagram of an air conditioner according to an embodiment of the present invention;

[0026] Figure 2 is a schematic structural diagram of a compressor according to an embodiment of the present invention;

[0027] Figure 3 is a schematic structural diagram of a controller according to an embodiment of the present invention;

[0028] Figure 4 is a schematic structural diagram of an air conditioner according to another embodiment of the present invention;

[0029] Figure 5 is a flowchart of controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first operating frequency of the compressor according to an embodiment of the present invention;

[0030] Figure 6 is a schematic flowchart of determining the target preheating time according to the current ambient temperature, power-off duration and preset shortest preheating time according to an embodiment of the present invention;

[0031] Figure 7 is a flowchart of the control method of the air conditioner according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0033] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention.

[0034] The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0035] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0036] As Figure 1 shown, the air conditioner 100 in the present invention performs a refrigeration cycle by using a compressor 103, a condenser, an electronic expansion valve 107 and an evaporator 101. The refrigeration cycle includes a series of processes involving compression, condensation, expansion and evaporation, and supplies refrigerant to the air that has been conditioned and heat-exchanged.

[0037] The compressor 103 compresses the refrigerant gas in a high-temperature and high-pressure state that enters from the suction pipe 1032 and discharges the compressed refrigerant gas through the discharge pipe 1031. The discharged refrigerant gas flows into the condenser from the condenser inlet pipe 104. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0038] The electronic expansion valve 107 expands the high-temperature and high-pressure liquid-phase refrigerant that has been condensed in the condenser and discharged via the condenser outlet pipe 106 into a low-pressure liquid-phase refrigerant. The evaporator 101 evaporates the refrigerant expanded in the electronic expansion valve 107 and returns the refrigerant gas in the low-temperature and low-pressure state to the compressor 103. The evaporator 101 can achieve a refrigeration effect by exchanging heat with the material to be cooled by utilizing the latent heat of evaporation of the refrigerant. During the entire cycle, the middle temperature sensor 102 of the evaporator and the middle temperature sensor 105 of the condenser can monitor the condensation temperature and the evaporation temperature in real time.

[0039] Among them, as Figure 2 shown, the compressor 103 includes a compressor exhaust port 1, a compressor rotor 2, a compressor coil 3, a compressor cylinder 4, a compressor oil pump 5, a compressor oil sump 6, an oil level sensor 20, and a compressor bottom temperature sensor 7.

[0040] Specifically, the compressor exhaust port 1 is the outlet of the high-pressure gas inside the compressor 103, and can discharge the compressed high-temperature and high-pressure refrigerant gas to other parts of the refrigeration system, such as the condenser; the compression rotor 2 is the rotating component of the compressor 103, and can achieve gas compression through rotational motion; the compressor coil 3 is a part of the motor of the compressor 103, and can drive the rotation of the compressor rotor 2. When the compressor 103 is preheated, the compressor coil 3 is energized. Due to the low power, the compressor rotor 2 does not rotate, and the compressor coil 3 generates heat. The heat generated by the compressor coil 3 is transmitted to the oil sump at the bottom of the compressor 103 through the rotating shaft to preheat the lubricating oil at the bottom of the compressor 103; the compressor cylinder 4 is the space inside the compressor 103 for compressing gas; the compressor oil pump 5 is used to supply lubricating oil to each lubrication part of the compressor 103; the compressor oil sump 6 is used to store lubricating oil; the oil level sensor 20 of the compressor is used to monitor the oil level height in the compressor oil sump 6; the compressor bottom temperature sensor 7 is used to monitor the temperature at the bottom of the compressor 103.

[0041] In the embodiment shown in the present application, the air conditioner 100 further includes a controller 71. The controller 71 refers to a device that can generate operation control signals according to the instruction operation code and timing signals to instruct the air conditioner 100 to execute control instructions. For example, in response to the power-on or power-off instruction issued by the user received, the controller 71 can perform operations related to the object selected by the power-on or power-off instruction.

[0042] The embodiment of the present application also provides a schematic diagram of the hardware structure of a controller 71, as Figure 3 shown, the controller 71 includes a processor 83. Optionally, it further includes a memory 82 and a communication interface 84 connected to the processor 83. The processor 83, the memory 82, and the communication interface 84 are connected through a bus 81.

[0043] The processor 83 may be a central processing unit (CPU), a general-purpose processor 83, a network processor 83 (NP), a digital signal processor 83 (DSP), a microprocessor 83, a microcontroller 7183, a programmable logic device (PLD), or any combination thereof. The processor 83 may also be any other device with processing capabilities, such as a circuit, a device, or a software module. The processor 83 may also include multiple CPUs, and the processor 83 may be a single-CPU processor 83 or a multi-CPU processor 83. The processor 83 herein may refer to one or more devices, circuits, or processing cores for processing data (such as computer program instructions).

[0044] The memory 82 may be a read-only memory 82 (ROM) or other types of static storage devices that can store static information and instructions, a random access memory 82 (RAM), or other types of dynamic storage devices that can store information and instructions. It may also be an electrically erasable programmable read-only memory 82 (EEPROM), a compact disc read-only memory (CD ROM), or other optical disc storage, optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), a magnetic disk storage medium, or any other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer. The embodiments of the present application do not impose any restrictions on this. The memory 82 may exist independently or be integrated with the processor 83. Among them, the memory 82 may contain computer program code. The processor 83 is used to execute the computer program code stored in the memory 82, thereby implementing the control method of the air conditioner 100 provided by the embodiments of the present application.

[0045] The communication interface 84 may be used to communicate with other devices or communication networks (such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.). The communication interface 84 may be a module, a circuit, a transceiver, or any device capable of implementing communication.

[0046] The bus 81 can be a peripheral component interconnect (PCI) bus 81, an extended industry standard architecture (EISA) bus 81, or the like. The bus 81 can be divided into an address bus 81, a data bus 81, a control bus 81, and the like.

[0047] The following will be combined with Figures 1-7 to describe the air conditioner 100 and its control method according to an embodiment of the present invention.

[0048] Combined with Figures 1-4 As shown, in some embodiments, the air conditioner 100 includes: a refrigerant circulation circuit 10. The refrigerant circulation circuit 10 enables the refrigerant to perform a refrigeration cycle in a circuit composed of a compressor 103, a condenser, an electronic expansion valve 107, and an evaporator 101. One of the condenser and the evaporator 101 is an outdoor heat exchanger, and the other is an indoor heat exchanger. Among them, the electronic expansion valve 107 is provided between the condenser and the evaporator 101. The electronic expansion valve 107 is configured to increase the flow resistance of the refrigerant passing through the electronic expansion valve 107 when its opening degree decreases, and decrease the flow resistance of the refrigerant passing through the electronic expansion valve 107 when its opening degree increases.

[0049] In an embodiment of the present invention, the air conditioner 100 further includes: an oil level sensor 20, which is provided in the oil sump at the bottom of the compressor 103 and is used to detect the oil level height of the oil sump.

[0050] In an embodiment of the present invention, the air conditioner 100 further includes: a controller 71. The controller 71 is configured to: after the compressor 103 starts, periodically obtain the current oil level height and the current operating frequency of the compressor 103, and control the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first oil level height and the first operating frequency of the compressor 103 in the current cycle until the operating frequency of the compressor 103 in the current cycle reaches the target operating frequency.

[0051] Specifically, after the air conditioner 100 is turned on and the compressor 103 starts, the controller 71 can detect the oil level height of the oil sump through the oil level sensor 20 provided inside the compressor 103. In the embodiment of the present invention, by periodically obtaining the oil level height in the compressor oil sump 6 and the current operating frequency of the compressor 103, and controlling the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the change of the first oil level height and the first operating frequency of the compressor 103 in the current cycle, the discharge amount and recovery amount of the lubricating oil in the compressor oil sump 6 are controlled, and the refrigerant state of the return air of the compressor 103 is adjusted. By repeating this cycle, the operating frequency of the compressor 103 and the opening degree of the electronic expansion valve are continuously adjusted until the operating frequency of the compressor 103 in the current cycle reaches the target operating frequency, so that when the air conditioner 100 operates at a low temperature, the viscosity and the amount of the lubricating oil in the compressor oil sump 6 are ensured during the process from the start of the compressor 103 to the achievement of the target operating frequency, so that the components of the compressor 103 have sufficient lubricating oil for lubrication, and the reliability of the air conditioner 100 during low-temperature operation is improved.

[0052] For the air conditioner 100 according to the embodiment of the present invention, during the process from the start of the air conditioner 100 to the achievement of the target operating frequency of the compressor 103, the operating frequency of the compressor 103 and the opening degree of the electronic expansion valve 107 can be controlled according to the detected oil level height and the current operating frequency of the compressor 103 to control the amount of the lubricating oil in the compressor oil sump 6 and adjust the refrigerant state of the return air of the compressor 103, so as to ensure the viscosity and the amount of the lubricating oil in the compressor oil sump 6, enable the components of the compressor 103 to have sufficient lubricating oil for lubrication, avoid the situation of the compressor 103 running dry due to lack of oil, and improve the reliability of the air conditioner 100 during low-temperature operation.

[0053] In an embodiment of the present invention, when controlling the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first oil level height and the first operating frequency of the compressor 103 in the current cycle, the controller 71 is specifically configured as follows: if the first oil level height is less than the first preset height, then control the operating frequency of the compressor 103 in the next cycle to decrease by the first preset frequency, and control the opening degree of the electronic expansion valve 107 in the next cycle to remain unchanged.

[0054] Specifically, the first preset height is the lower limit value of the oil level in the compressor oil sump 6 when the compressor 103 is operating normally. During the process of controlling the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first oil level height in the current cycle and the first operating frequency of the compressor 103, if the first oil level height is less than the first preset height, it is considered that the oil level in the compressor oil sump 6 is lower than the preset lower limit of the oil level. The compressor 103 may run dry due to lack of oil, resulting in wear of the compressor 103. At this time, the controller 71 can control the operating frequency of the compressor 103 in the next cycle to decrease by the first preset frequency, so as to reduce the operating frequency of the compressor 103 and the oil discharge volume of the compressor 103. Further, the controller 71 can control the opening degree of the electronic expansion valve 107 in the next cycle to remain unchanged, so as to maintain the current refrigerant flow rate without affecting the refrigeration effect, that is, when the circulation rate of the refrigerant remains unchanged, prevent further oil level drop by reducing the oil volume discharged by the compressor 103, so that there is enough lubricating oil for the components of the compressor 103 for lubrication, and improve the reliability of the air conditioner during low-temperature operation.

[0055] In a specific embodiment, the first preset frequency can be a value set according to experimental data and experience, for example, 1Hz / 10s.

[0056] In some embodiments, if the first oil level height is greater than the first preset height but not greater than the second preset height, and it is determined that the first oil level height is in a downward trend in the current cycle, then control the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first operating frequency of the compressor 103, where the second preset height is greater than the first preset height.

[0057] Specifically, the second preset height is the oil level safety value of the compressor oil sump 6 when the compressor 103 operates normally. The second preset height is lower than the upper limit value of the oil level. When the oil level of the compressor oil sump 6 is higher than the second preset height, it is considered that the oil volume in the compressor oil sump 6 should be prevented from reaching the upper limit value to avoid lubricating oil overflow. If the first oil level height is greater than the first preset height but not greater than the second preset height, and it is determined that the first oil level height is in a downward trend in the current cycle, it is considered that although the oil level of the compressor oil sump 6 is within the safe range, as the operating frequency of the compressor 103 increases, it may approach the preset lower limit of the oil level. Therefore, in the embodiment of the present invention, the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle are controlled according to the first operating frequency of the compressor 103. Specifically, in the case where the oil level may continue to drop, at this time, the controller can control the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first operating frequency of the compressor 103, increase the oil return amount, reduce the downward trend of the oil level, and further prevent the compressor 103 from being worn due to lack of oil.

[0058] In some embodiments, if the first oil level height is greater than the first preset height and it is determined that the first oil level height is not in a downward trend in the current cycle; or, if the first oil level height is greater than the second preset height and it is determined that the first oil level height is in a downward trend in the current cycle, then after delaying the first preset time, the operating frequency of the compressor 103 in the next cycle is controlled to increase by the second preset frequency, and the opening degree of the electronic expansion valve 107 in the next cycle is controlled according to the operating frequency of the compressor 103 in the next cycle.

[0059] Specifically, if the first oil level height is greater than the first preset height and it is determined that the first oil level height is not in a downward trend during the current cycle, that is, the oil level in the current compressor oil sump 6 is within the safe range and there is no continuous downward trend, and the oil quantity is relatively stable; or, if the first oil level height is greater than the second preset height and it is determined that the first oil level height is in a downward trend during the current cycle, that is, the oil level in the current compressor oil sump 6 is still within a relatively high safe range, the adjustment of the frequency of the compressor 103 and the electronic expansion valve 107 may not be performed during the current cycle. After delaying the first preset time, the operating frequency of the compressor 103 in the next cycle may be controlled to increase by a second preset frequency, and the opening degree of the electronic expansion valve 107 in the next cycle may be controlled according to the operating frequency of the compressor 103 in the next cycle. It can be understood that controlling the operating frequency of the compressor 103 to increase by the second preset frequency in the next cycle and controlling the opening degree of the electronic expansion valve 107 in the next cycle according to the operating frequency of the compressor 103 in the next cycle can ensure that during the process of the compressor increasing its frequency to reach the target operating frequency, the discharge amount and the recovery amount of the lubricating oil in the compressor oil sump 6 can remain stable, thereby ensuring the viscosity and quantity of the lubricating oil in the compressor oil sump 6, enabling the components of the compressor 103 to have sufficient lubricating oil for lubrication, avoiding the situation of the compressor 103 running dry due to lack of oil, and improving the reliability of the air conditioner 100 during low-temperature operation.

[0060] In a specific embodiment, the first preset time and the second preset frequency may be values set according to experimental data and experience. Among them, the first preset time may be 30 s.

[0061] In an embodiment of the present invention, as Figure 5 shown, when controlling the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first operating frequency of the compressor 103, the controller 71 is specifically configured to: if the first operating frequency of the compressor 103 is greater than the third preset frequency, control the operating frequency of the compressor 103 in the next cycle to remain unchanged, and control the opening degree of the electronic expansion valve 107 in the next cycle to decrease by a preset opening degree.

[0062] Specifically, if the first oil level height is greater than the first preset height but not greater than the second preset height, and it is determined that the first oil level height is in a downward trend in the current cycle, when controlling the operating frequency of the compressor 103 in the next cycle and the opening degree of the electronic expansion valve 107 in the next cycle according to the first operating frequency of the compressor 103, if the first operating frequency of the compressor 103 is greater than the third preset frequency, it is considered that the current frequency of the compressor 103 is relatively high, the discharge amount of the lubricating oil is too large, and the oil amount is in a downward trend. At this time, the controller 71 can control the operating frequency of the compressor 103 to remain unchanged in the next cycle, and control the opening degree of the electronic expansion valve 107 to decrease by a preset opening degree in the next cycle. Thus, while maintaining the oil circulation strength, that is, while maintaining the oil return amount, the discharge amount of the oil in the compressor 103 can be reduced, and then the oil in the compressor oil sump 6 can be increased, preventing the compressor 103 from being worn due to lack of oil in a low-temperature environment.

[0063] In a specific embodiment, the third preset frequency can be a value set according to experimental data and experience.

[0064] In some embodiments, as Figure 5 shown, if the first operating frequency of the compressor 103 is not greater than the third preset frequency, control the operating frequency of the compressor 103 to increase by a fourth preset frequency in the next cycle, and control the opening degree of the electronic expansion valve 107 to remain unchanged in the next cycle, where the third preset frequency is less than the target operating frequency, and the fourth preset frequency is greater than the second preset frequency.

[0065] Specifically, if the first operating frequency of the compressor 103 is not greater than the third preset frequency, that is, the current compressor 103 has just started, the operating frequency is still relatively low, the oil return ability is poor, and the oil return speed is slow. At this time, the operating frequency of the compressor 103 can be controlled to increase by a fourth preset frequency in the next cycle to enhance the oil return ability of the compressor 103, and the opening degree of the electronic expansion valve 107 can be controlled to remain unchanged in the next cycle to avoid the exhaust temperature being too high and triggering the protection mechanism of the air conditioner 100, ensuring that the oil discharge amount and the oil return amount of the compressor 103 are stable, and then increasing the oil level of the compressor oil sump 6 to prevent the compressor 103 from being worn due to lack of oil. Specifically, the fourth preset frequency can be a value set according to experimental data and experience, and the third preset frequency is less than the target operating frequency, and the fourth preset frequency is greater than the second preset frequency, where the fourth preset frequency can be 2Hz / s.

[0066] In an embodiment of the present invention, when it is determined that the first oil level height is in a downward trend or not in a downward trend during the current cycle, the controller 71 is specifically configured as follows: during the current cycle, if the oil level heights at adjacent moments or adjacent time periods decrease in sequence, it is determined that the first oil level height is in a downward trend during the current cycle; otherwise, it is determined that the first oil level height is not in a downward trend during the current cycle.

[0067] Specifically, during the operation of the air conditioner 100, the controller 71 can monitor the first oil level height of the compressor 103 in real time through the oil level sensor 20. If, during the current cycle, the oil level heights at adjacent moments or adjacent time periods decrease in sequence, that is, during the current cycle, each subsequent oil level value is lower than the previous one. For example, the oil level height drops from 10 mm to 9 mm, and then to 8 mm and continues to drop, then the controller 71 determines that the first oil level height is in a downward trend during the current cycle. On the contrary, if there is at least one adjacent moment or adjacent time period where the oil level height is not lower than the previous data point. For example, if the oil level height drops from 10 mm to 9 mm, but then remains at 9 mm or rises to 10 mm, that is, the oil level height does not continue to drop at adjacent moments or adjacent time periods, then the controller 71 determines that the first oil level height is not in a downward trend during the current cycle, so as to improve the accuracy of the judgment.

[0068] In a specific embodiment, one cycle can be 16 s. Every 2 s, the first oil level height can be recorded, and it is determined whether the first oil level height is in a downward trend during the current cycle according to the change of the first oil level height.

[0069] In an embodiment of the present invention, after the operating frequency of the compressor 103 reaches the target operating frequency during the current cycle, the controller 71 is further configured to: obtain the current second oil level height in real time; if the second oil level height is less than the first preset height, and the target operating frequency of the compressor 103 is less than the fifth preset frequency and the duration reaches the second preset time, then control the operating frequency of the compressor 103 to increase to the sixth preset frequency, and control the opening degree of the electronic expansion valve 107 according to the operating frequency of the compressor 103. Until the first preset condition is met, control the compressor 103 to operate at the target operating frequency, and control the opening degree of the electronic expansion valve 107 to return to the opening value before the frequency increase at a preset decreasing rate, where the first preset condition includes: the time for the compressor 103 to operate at the sixth preset frequency reaches the third preset time, the oil return time of the compressor 103 reaches the fourth preset time, or the compressor 103 shuts down. The second preset time is greater than the fourth preset time, and the fourth preset time is greater than the third preset time.

[0070] Specifically, during the operation of the compressor 103, when the operating frequency of the compressor 103 reaches the target operating frequency, the controller 71 can obtain the current second oil level height in real time. If the second oil level height is less than the first preset height, and the target operating frequency of the compressor 103 is less than the fifth preset frequency and the duration reaches the second preset time, that is, when the compressor 103 operates at the target operating frequency for the second preset time while ensuring that it will not exceed its maximum or recommended operating frequency, and the oil level in the compressor oil sump 6 is still lower than the preset lower limit of the oil level, the compressor 103 may run dry due to lack of oil, resulting in wear of the compressor 103. At this time, the controller 71 controls the operating frequency of the compressor 103 to increase to the sixth preset frequency, and controls the opening degree of the electronic expansion valve 107 according to the operating frequency of the compressor 103, that is, increases the operating frequency of the compressor 103 and controls the opening degree of the electronic expansion valve 107 according to the current operating frequency of the compressor 103 to enhance the oil return ability of the compressor 103 and reduce the oil discharge amount. Until the first preset condition is met, the controller 71 controls the compressor 103 to operate at the target operating frequency. At the same time, the opening degree of the electronic expansion valve 107 returns to the opening degree value before the frequency increase at a preset decreasing rate to maintain the stability of the oil level of the compressor 103. Among them, the first preset condition includes: the operating time of the compressor 103 at the sixth preset frequency reaches the third preset time, the oil return time of the compressor 103 reaches the fourth preset time, or the compressor 103 stops. The second preset time is greater than the fourth preset time, and the fourth preset time is greater than the third preset time.

[0071] In a specific embodiment, the fifth preset frequency, the sixth preset frequency, the second preset time, the third preset time, the fourth preset time, and the preset decreasing rate can be values set according to experimental data and experience. For example, the fifth preset frequency can be 35 Hz, the sixth preset frequency can be 55 Hz, the second preset time can be 30 min, the third preset time can be 1 min, the fourth preset time can be 2 min, and the preset decreasing rate can be 30 P / 10 s.

[0072] In an embodiment of the present invention, the air conditioner 100 further includes an ambient temperature sensor, an exhaust temperature sensor, a compressor bottom temperature sensor 7, and a condenser middle temperature sensor 105. As Figure 6 shown, before the compressor 103 starts, the controller 71 is further configured to: obtain the current ambient temperature and the power-off duration of the air conditioner 100; determine the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time.

[0073] Specifically, before the compressor 103 starts, a timer set in the air conditioner 100 can record the power-off duration, that is, the time length from the last power-off to the current power-on of the air conditioner, and the ambient temperature sensor can obtain the ambient temperature where the air conditioner 100 is currently located in real time and store it. Further, the controller 71 can calculate the target preheating time through a preset algorithm based on the current ambient temperature, power-off duration, and preset shortest preheating time to ensure that the compressor 103 is fully preheated before starting under the condition that factors such as ambient temperature and power-off duration change. For example, if the air conditioner 100 detects a sudden drop in ambient temperature during the preheating process, the preheating time can be increased to adapt to this change. It can be understood that the lower the current ambient temperature and the longer the power-off duration, the longer the target preheating time.

[0074] In some embodiments, as Figure 6 shown, before the compressor 103 starts, it is determined whether the air conditioner 100 changes from a power-off state to a power-on state; when it is determined that the air conditioner 100 changes from a power-off state to a power-on state, and the power-on time reaches the fifth preset time, and a startup instruction is received, and the current ambient temperature is less than the preset ambient temperature, and the exhaust temperature of the compressor 103 reaches the preset exhaust temperature, the first preheating control strategy is executed, where the first preheating control strategy includes: controlling the coil of the compressor 103 to be energized until the time of coil energization reaches the target preheating time, and then controlling the compressor 103 to start.

[0075] Specifically, before the compressor 103 starts, the controller 71 can detect in real time whether the air conditioner 100 changes from a power-off state to a power-on state. When the controller 71 determines that the air conditioner 100 changes from a power-off state to a power-on state, the timer starts timing. If the power-on time reaches the fifth preset time, and the controller 71 receives a startup instruction issued by the user, and the controller 71 determines that the current ambient temperature is less than the preset ambient temperature, and the controller 71 determines that the exhaust temperature of the compressor 103 reaches the preset exhaust temperature, the controller 71 executes the first preheating control strategy, that is, the controller 71 controls the coil of the compressor 103 to be energized to make the coil heat up until the time of coil energization reaches the target preheating time, that is, when the compressor 103 meets the condition of being able to start normally at this time, the compressor 103 is controlled to start. It can be understood that during the preheating process of the compressor coil 3, the preheating gear of the compressor coil can be selected, such as 20 - 50W, etc. for optional preheating. The heat generated by the compressor coil 3 can be transmitted to the compressor oil sump 6 through the rotating shaft to preheat the oil liquid at the bottom of the compressor 103 and vaporize the refrigerant deposited at the bottom of the compressor 103, so as to effectively prevent liquid compression before the air conditioner is turned on, increase the oil temperature of the compressor 103, thereby increasing the viscosity of the lubricating oil, and further ensuring that before the compressor 103 starts, the situation of lack of oil in the compressor 103 and dry-running of the compressor 103 can be effectively prevented.

[0076] In a specific embodiment, the fifth preset time, the preset ambient temperature, and the preset exhaust temperature can be values set according to experimental data and experience. For example, the fifth preset time can be 60 s, the preset ambient temperature can be 3°C, and the preset exhaust temperature can be 10°C.

[0077] In some embodiments, as Figure 6 shown, before the compressor 103 starts, if the air conditioner 100 remains in the powered-on state and the current ambient temperature is less than the preset ambient temperature, the second preheating control strategy is periodically executed until the second preset condition is met, and then the coil of the compressor 103 is controlled to be powered off. The second preheating control strategy includes: controlling the coil of the compressor 103 to be powered on, and when the power-on time of the coil reaches the target preheating time, controlling the coil to be powered off for the sixth preset time, and then obtaining the current ambient temperature and the power-off duration again, and determining the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time; the second preset condition includes that the current ambient temperature is not less than the preset ambient temperature, or when the power-on time of the coil reaches the target preheating time, the temperature at the bottom of the compressor 103 is greater than the temperature of the condenser.

[0078] Specifically, before the compressor 103 starts, when the air conditioner 100 remains in the powered-on state, the controller 71 can continuously monitor the current ambient temperature. If the current ambient temperature is less than the preset ambient temperature, that is, the current air conditioner 100 is in a low-temperature operating environment, the controller periodically executes the second preheating control strategy until the second preset condition is met, and then controls the coil of the compressor 103 to be powered off. The second preheating control strategy includes: controlling the coil of the compressor 103 to be powered on to make the coil heat up until the power-on time of the coil reaches the target preheating time, and then controlling the coil to be powered off for the sixth preset time. After power-off, the controller obtains the current ambient temperature and the power-off duration again, recalculates and adjusts the target preheating time to accurately adapt to the changes in the external environment. The second preset condition includes that the current ambient temperature is not less than the preset ambient temperature, that is, the current ambient temperature can meet the starting condition of the compressor 103 and no additional preheating is required, or when the power-on time of the coil reaches the target preheating time, the temperature at the bottom of the compressor 103 is greater than the temperature of the condenser, that is, the compressor 103 has reached an appropriate operating temperature after preheating and the lubricating oil inside has been fully preheated to meet the starting condition. It can be understood that before the compressor 103 starts, when the air conditioner 100 remains in the powered-on state and the current ambient temperature is less than the preset ambient temperature, the embodiments of the present invention can preheat the oil at the bottom of the compressor 103, vaporize the refrigerant deposited at the bottom of the compressor 103, effectively prevent liquid compression, increase the oil temperature of the compressor 103, thereby increasing the viscosity of the lubricating oil, and preparing for the start of the compressor.

[0079] In a specific embodiment, the sixth preset time may be a value set according to experimental data and experience. For example, the sixth preset time may be 20 min.

[0080] In some embodiments, when determining the target preheating time according to the current ambient temperature, power-off duration, and preset shortest preheating time, the controller 71 is specifically configured to:

[0081] T = k×(M 1 - M 2 ) + b×M 2 ;

[0082] where T is the target preheating time, M 1 is the power-off duration, M 2 is the preset shortest preheating time, k is a preset constant determined according to the current ambient temperature, and b is a preset constant.

[0083] Specifically, when determining the target preheating time according to the current ambient temperature, power-off duration, and preset shortest preheating time, the specific formula is as shown above, where T is the target preheating time, indicating the time for which the compressor coil 3 needs to be powered on, M 1 is the power-off duration, indicating the time interval between the last shutdown of the air conditioner 100 and the current power-on state, M 2 is the preset shortest preheating time, indicating the time for which the compressor 103 generally needs to be preheated at least, k is a preset constant determined according to the current ambient temperature, used to adjust the preheating time to adapt to different external temperature conditions and varies with the ambient temperature, and b is a preset constant used to adjust the target preheating time. Exemplarily, the preset constant k determined according to the current ambient temperature is shown in Table 1,

[0084] Ambient temperature k -15°C ≤ Ta < 3°C 1 -20°C ≤ Ta < -15°C 1.5 -30°C ≤ Ta < -20°C 2 Ta < -30°C 3

[0085] Table 1

[0086] In some embodiments, when controlling the opening degree of the electronic expansion valve 107 according to the operating frequency of the compressor 103, the controller 71 is specifically configured to:

[0087] P = a×F + T a ×d+(T d - T e )×c + L;

[0088] where P is the opening degree of the electronic expansion valve 107, F is the operating frequency of the compressor 103, T a is the current ambient temperature, T d is the temperature of the condenser, T e is the temperature at the bottom of the compressor 103, and a, d, c, and L are preset constants.

[0089] Specifically, when controlling the opening degree of the electronic expansion valve 107 according to the operating frequency of the compressor 103, the specific formula is as shown above, where P is the opening degree of the electronic expansion valve 107, which is used to determine the flow rate of the oil of the compressor 103 passing through the expansion valve, F is the operating frequency of the compressor 103, which is used to determine the oil return amount of the compressor 103, and T a is the current ambient temperature, which is used to determine the length of the preheating time required when the compressor 103 is powered on, and T d is the temperature of the condenser, and T e is the temperature at the bottom of the compressor 103. Whether the preheating of the compressor 103 is completed can be determined by the difference between the two.

[0090] In some embodiments, after the operating frequency of the compressor 103 reaches the target operating frequency in the current cycle, the controller 71 is further configured to: when receiving a shutdown instruction, obtain the second operating frequency of the compressor 103; control the compressor 103 to continuously operate for a seventh preset time and then stop operating according to the second operating frequency of the compressor 103.

[0091] Specifically, during the operation of the compressor 103, when the operating frequency of the compressor 103 reaches the target operating frequency, if the controller 71 receives a shutdown instruction, the second operating frequency of the current compressor 103 is obtained, and then the compressor 103 is controlled to continuously operate at the current frequency for a seventh preset time before shutdown. Specifically, the second operating frequency and the seventh preset time can be set according to experimental data. For example, when the operating frequency of the compressor 103 reaches the target operating frequency in the current cycle, and at this time the controller 71 receives a shutdown instruction, if the second operating frequency of the compressor 103 is below 30HZ, the compressor 103 needs to continuously operate for 5 minutes to stop; if the second operating frequency of the compressor 103 is above 30HZ, the compressor 103 needs to continuously operate for 2 minutes to stop; if the second operating frequency of the compressor 103 is below 18hz, the compressor 103 needs to continuously operate for 7 minutes to stop, so as to ensure that the compressor 103 can return oil stably before shutdown, so that the components of the compressor 103 have sufficient lubricating oil for lubrication, and improve the reliability of the air conditioner 100 during low-temperature operation.

[0092] According to the air conditioner 100 of the embodiment of the present invention, during the process from when the air conditioner 100 is turned on to when the compressor 103 reaches the target operating frequency, the operating frequency of the compressor 103 and the opening degree of the electronic expansion valve 107 can be controlled according to the detected oil level height and the current operating frequency of the compressor 103, so as to control the amount of lubricating oil in the compressor oil sump 6, adjust the refrigerant state of the return gas of the compressor 103, ensure the viscosity and amount of the lubricating oil in the compressor oil sump 6, enable the components of the compressor 103 to have sufficient lubricating oil for lubrication, avoid the situation of the compressor 103 running dry due to lack of oil, improve the reliability of the air conditioner 100 during low-temperature operation. Further, during the preheating process before the compressor 103 is started, by setting an ambient temperature sensor, an exhaust temperature sensor, a compressor bottom temperature sensor 7 and a condenser middle temperature sensor 105, the ambient temperature, the exhaust temperature of the compressor 103, the bottom oil sump temperature of the compressor 103 and the condensation temperature of the condenser can be detected in real time, so as to judge the preheating time of the compressor 103 and preheat the oil liquid at the bottom of the compressor 103. Furthermore, when the operating frequency of the compressor 103 reaches the target operating frequency and a shutdown instruction is received, the controller 71 can control the compressor 103 to continuously operate at the current frequency for a preset time before shutdown according to the current operating frequency of the compressor 103, so as to ensure that the compressor 103 can stably return oil before shutdown, enable the components of the compressor 103 to have sufficient lubricating oil for lubrication, and improve the reliability of the air conditioner 100 during low-temperature operation.

[0093] The following refers to Figure 7 Describe the control method of the air conditioner according to the embodiment of the present invention.

[0094] As Figure 7 shown, the control method of the air conditioner according to the embodiment of the present invention at least includes step S1-step S2.

[0095] Step S1, after the compressor starts, periodically obtain the current oil level height and the current operating frequency of the compressor.

[0096] Step S2, control the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first oil level height and the first operating frequency of the compressor in the current cycle until the operating frequency of the compressor in the current cycle reaches the target operating frequency.

[0097] In some embodiments, when controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first oil level height in the current cycle and the first operating frequency of the compressor, if the first oil level height is less than the first preset height, control the operating frequency of the compressor in the next cycle to decrease by the first preset frequency, and control the opening degree of the electronic expansion valve in the next cycle to remain unchanged; if the first oil level height is greater than the first preset height but not greater than the second preset height, and it is determined that the first oil level height is in a downward trend in the current cycle, then control the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first operating frequency of the compressor, where the second preset height is greater than the first preset height; if the first oil level height is greater than the first preset height, and it is determined that the first oil level height is not in a downward trend in the current cycle; or, if the first oil level height is greater than the second preset height, and it is determined that the first oil level height is in a downward trend in the current cycle, then after delaying for the first preset time, control the operating frequency of the compressor in the next cycle to increase by the second preset frequency, and control the opening degree of the electronic expansion valve in the next cycle according to the operating frequency of the compressor in the next cycle.

[0098] In some embodiments, when controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first operating frequency of the compressor, if the first operating frequency of the compressor is greater than the third preset frequency, control the operating frequency of the compressor in the next cycle to remain unchanged, and control the opening degree of the electronic expansion valve in the next cycle to decrease by the preset opening degree; if the first operating frequency of the compressor is not greater than the third preset frequency, control the operating frequency of the compressor in the next cycle to increase by the fourth preset frequency, and control the opening degree of the electronic expansion valve in the next cycle to remain unchanged, where the third preset frequency is less than the target operating frequency, and the fourth preset frequency is greater than the second preset frequency.

[0099] In some embodiments, when determining whether the first oil level height is in a downward trend or not in the current cycle, in the current cycle, if the oil level height in adjacent moments or adjacent time periods decreases in sequence, then determine that the first oil level height is in a downward trend in the current cycle, otherwise, determine that the first oil level height is not in a downward trend in the current cycle.

[0100] In some embodiments, after the operating frequency of the compressor reaches the target operating frequency within the current cycle, the following steps are further included: obtaining the current second oil level height in real time; if the second oil level height is less than the first preset height, and the target operating frequency of the compressor is less than the fifth preset frequency and the duration reaches the second preset time, then controlling the operating frequency of the compressor to increase to the sixth preset frequency, and controlling the opening degree of the electronic expansion valve according to the operating frequency of the compressor, until when the first preset condition is satisfied, controlling the compressor to operate at the target operating frequency, and controlling the opening degree of the electronic expansion valve to return to the opening value before the frequency increase at a preset decreasing rate, where the first preset condition includes: the time for the compressor to operate at the sixth preset frequency reaches the third preset time, the oil return time of the compressor reaches the fourth preset time, or the compressor shuts down, the second preset time is greater than the fourth preset time, and the fourth preset time is greater than the third preset time.

[0101] In some embodiments, before the compressor starts, the following steps are further included: obtaining the current ambient temperature and the power-off duration of the air conditioner; determining the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time; judging whether the air conditioner changes from the power-off state to the power-on state; when it is judged that the air conditioner changes from the power-off state to the power-on state, and the power-on time reaches the fifth preset time, and a start-up instruction is received, and the current ambient temperature is less than the preset ambient temperature, and the exhaust temperature of the compressor reaches the preset exhaust temperature, execute the first preheating control strategy, where the first preheating control strategy includes: controlling the coil of the compressor to be energized until the time for the coil to be energized reaches the target preheating time, and then controlling the compressor to start; when the air conditioner remains in the power-on state and the current ambient temperature is less than the preset ambient temperature, periodically execute the second preheating control strategy until the second preset condition is satisfied, and then control the coil of the compressor to be de-energized, where the second preheating control strategy includes: controlling the coil of the compressor to be energized, when the time for the coil to be energized reaches the target preheating time, controlling the coil to be de-energized for the sixth preset time, and obtaining the current ambient temperature and the power-off duration again, and determining the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time; the second preset condition includes that the current ambient temperature is not less than the preset ambient temperature, or when the time for the coil to be energized reaches the target preheating time, the temperature at the bottom of the compressor is greater than the temperature of the condenser.

[0102] In some embodiments, when determining the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time

[0103] T = k×(M 1 -M 2 ) + b×M 2 ;

[0104] where T is the target preheating time, M 1 is the power-off duration, M2 is the preset minimum preheating time, k is a preset constant determined according to the current ambient temperature, and b is a preset constant.

[0105] In some embodiments, when the opening of the electronic expansion valve is controlled according to the operating frequency of the compressor,

[0106] P=a×F+T a ×d+(T d -T e )×c+L;

[0107] Among them, P is the opening of the electronic expansion valve, F is the operating frequency of the compressor, T a is the current ambient temperature, T d is the temperature of the condenser, T e is the temperature at the bottom of the compressor, and a, d, c and L are preset constants.

[0108] In some embodiments, after the operating frequency of the compressor in the current cycle reaches the target operating frequency, it also includes: when a shutdown command is received, obtaining the second operating frequency of the compressor; and controlling the compressor to stop running after running continuously for the seventh preset time according to the second operating frequency of the compressor.

[0109] It should be noted that when controlling the air conditioner, its specific implementation method is similar to the specific implementation method of the air conditioner in any one of the above-mentioned embodiments of the present invention. Therefore, for a detailed exemplary description of the control process of the household appliance, please refer to the aforementioned relevant description part about the air conditioner. In order to reduce redundancy, it will not be repeated here.

[0110] According to the control method of the air conditioner according to the embodiments of the present invention, during the process from the air conditioner being turned on to the compressor reaching the target operating frequency, the operating frequency of the compressor and the opening degree of the electronic expansion valve can be controlled according to the detected height of the oil level and the current operating frequency of the compressor, so as to control the amount of lubricating oil in the compressor oil sump, adjust the refrigerant state of the compressor suction gas, ensure the viscosity and amount of the lubricating oil in the compressor oil sump, enable the components of the compressor to have sufficient lubricating oil for lubrication, avoid the situation of the compressor running dry due to lack of oil, and improve the reliability of the air conditioner during low-temperature operation. Further, during the preheating process before the compressor is turned on, the preheating time of the compressor can be judged by detecting the ambient temperature, the compressor discharge temperature, the temperature of the oil sump at the bottom of the compressor, and the condensation temperature of the condenser in real time, and the oil liquid at the bottom of the compressor can be preheated, so as to effectively prevent the compressor from lacking oil and running dry when the air conditioner operates at low temperature. Further, after the operating frequency of the compressor reaches the target operating frequency and a shutdown instruction is received, the compressor can be controlled to continuously operate at the current frequency for a preset time before shutdown according to the current operating frequency of the compressor, so as to ensure that the compressor can return oil stably before shutdown, enable the components of the compressor to have sufficient lubricating oil for lubrication, and improve the reliability of the air conditioner during low-temperature operation.

[0111] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0112] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirits of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An air conditioner, characterized in that: include: A refrigerant circulation loop, wherein the refrigerant performs a refrigeration cycle in a loop consisting of a compressor, a condenser, an electronic expansion valve, and an evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger; The electronic expansion valve is arranged between the condenser and the evaporator, and is used to increase the flow resistance of the refrigerant passing through the electronic expansion valve when the opening degree of the electronic expansion valve is reduced, and to reduce the flow resistance of the refrigerant passing through the electronic expansion valve when the opening degree of the electronic expansion valve is increased; An oil level sensor is provided in the oil pool at the bottom of the compressor and is used to detect the oil level height of the oil pool; The controller is configured to: after the compressor is started, periodically obtain the current oil level height and the current operating frequency of the compressor, and control the operating frequency of the compressor in the next cycle and the opening of the electronic expansion valve in the next cycle according to the first oil level height and the first operating frequency of the compressor in the current cycle, until the operating frequency of the compressor in the current cycle reaches the target operating frequency.

2. The air conditioner according to claim 1, characterized in that: When controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first oil level in the current cycle and the first operating frequency of the compressor, the controller is specifically configured as follows: If the first oil level is less than a first preset level, the operating frequency of the compressor in the next cycle is controlled to be lowered by the first preset frequency, and the opening degree of the electronic expansion valve in the next cycle is controlled to remain unchanged; If the first oil level is greater than the first preset height but not greater than the second preset height, and it is determined that the first oil level is in a downward trend in the current cycle, the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle are controlled according to the first operating frequency of the compressor, wherein the second preset height is greater than the first preset height; If the first oil level height is greater than the first preset height, and it is determined that the first oil level height is not in the downward trend in the current cycle; or, if the first oil level height is greater than the second preset height, and it is determined that the first oil level height is in the downward trend in the current cycle, then after a delay of a first preset time, the operating frequency of the compressor in the next cycle is controlled to increase by a second preset frequency, and the opening of the electronic expansion valve in the next cycle is controlled according to the operating frequency of the compressor in the next cycle.

3. The air conditioner according to claim 2, characterized in that: When controlling the operating frequency of the compressor in the next cycle and the opening degree of the electronic expansion valve in the next cycle according to the first operating frequency of the compressor, the controller is specifically configured as follows: If the first operating frequency of the compressor is greater than the third preset frequency, controlling the operating frequency of the compressor in the next cycle to remain unchanged, and controlling the opening of the electronic expansion valve in the next cycle to decrease by a preset opening; If the first operating frequency of the compressor is not greater than the third preset frequency, the operating frequency of the compressor in the next cycle is controlled to increase by a fourth preset frequency, and the opening of the electronic expansion valve in the next cycle is controlled to remain unchanged, wherein the third preset frequency is less than the target operating frequency, and the fourth preset frequency is greater than the second preset frequency.

4. The air conditioner according to claim 2, characterized in that: When determining whether the first oil level is in the downward trend or not in the downward trend in the current cycle, the controller is specifically configured to: In the current cycle, if the oil level heights in adjacent moments or adjacent time periods decrease successively, it is determined that the first oil level height is in the downward trend in the current cycle; otherwise, it is determined that the first oil level height is not in the downward trend in the current cycle.

5. The air conditioner according to claim 2, characterized in that: After the operating frequency of the compressor in the current cycle reaches the target operating frequency, the controller is further configured to: Acquire the current second oil level in real time; If the second oil level height is less than the first preset height, and the target operating frequency of the compressor is less than the fifth preset frequency and the duration reaches the second preset time, the operating frequency of the compressor is controlled to be increased to the sixth preset frequency, and the opening of the electronic expansion valve is controlled according to the operating frequency of the compressor until the first preset condition is met, the compressor is controlled to operate according to the target operating frequency, and the opening of the electronic expansion valve is controlled to be restored to the opening value before the frequency increase at a preset reduction rate, wherein the first preset condition includes: the time when the compressor runs at the sixth preset frequency reaches the third preset time, the oil return time of the compressor reaches the fourth preset time or the compressor is shut down, the second preset time is greater than the fourth preset time, and the fourth preset time is greater than the third preset time.

6. The air conditioner according to claim 5, characterized in that: The air conditioner further comprises an ambient temperature sensor, an exhaust temperature sensor, a compressor bottom temperature sensor and a condenser temperature sensor. Before the compressor is started, the controller is further configured as follows: Obtaining the current ambient temperature and the power-off duration of the air conditioner; Determine a target preheating time according to the current ambient temperature, the power-off duration, and a preset minimum preheating time; Determining whether the air conditioner changes from a power-off state to a power-on state; When it is determined that the air conditioner changes from the power-off state to the power-on state, and the power-on time reaches the fifth preset time, and a power-on instruction is received, and the current ambient temperature is less than the preset ambient temperature, and the exhaust temperature of the compressor reaches the preset exhaust temperature, a first preheating control strategy is executed, wherein the first preheating control strategy includes: controlling the coil of the compressor to be energized until the coil energization time reaches the target preheating time, and then controlling the compressor to start; When the air conditioner continues to be in the powered-on state and the current ambient temperature is lower than the preset ambient temperature, the second preheating control strategy is periodically executed until the second preset condition is met, and the coil of the compressor is controlled to be powered off, wherein the second preheating control strategy includes: controlling the coil of the compressor to be powered on, and when the power-on time of the coil reaches the target preheating time, controlling the coil to be powered off for a sixth preset time, and obtaining the current ambient temperature and power-off duration again, and determining the target preheating time according to the current ambient temperature, the power-off duration, and the preset shortest preheating time; the second preset condition includes that the current ambient temperature is not lower than the preset ambient temperature, or, when the power-on time of the coil reaches the target preheating time, the temperature at the bottom of the compressor is higher than the temperature of the condenser.

7. The air conditioner according to claim 6, characterized in that: When determining the target preheating time according to the current ambient temperature, the power-off duration and the preset minimum preheating time, the controller is specifically configured as follows: T = k × (M1-M2) + b × M2; Among them, T is the target preheating time, M1 is the power-off duration, M2 is the preset shortest preheating time, k is a preset constant determined according to the current ambient temperature, and b is a preset constant.

8. The air conditioner according to claim 6, characterized in that: When the opening degree of the electronic expansion valve is controlled according to the operating frequency of the compressor, the controller is specifically configured as follows: P=a×F+T a ×d+(T a -T e )×c+L; Wherein, P is the opening degree of the electronic expansion valve, F is the operating frequency of the compressor, T a is the current ambient temperature, T d is the temperature of the condenser, T e is the temperature of the bottom of the compressor, and a, d, c and L are preset constants.

9. The air conditioner according to claim 1, characterized in that: After the operating frequency of the compressor in the current cycle reaches the target operating frequency, the controller is further configured to: When receiving a stop instruction, obtaining a second operating frequency of the compressor; The compressor is controlled to stop running after running continuously for a seventh preset time according to the second operating frequency of the compressor.

10. A method for controlling an air conditioner, characterized in that: For the air conditioner according to any one of claims 1 to 9, the method comprises the following steps: After the compressor is started, periodically obtaining the current oil level and the current operating frequency of the compressor; The operating frequency of the compressor in the next cycle and the opening of the electronic expansion valve in the next cycle are controlled according to the first oil level in the current cycle and the first operating frequency of the compressor, until the operating frequency of the compressor in the current cycle reaches the target operating frequency.

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