Air conditioner and control method thereof

Abstract

The application discloses an air conditioner and a control method thereof. The control method comprises the following steps: acquiring an indoor environment temperature and an outdoor environment temperature, and obtaining a current indoor-outdoor environment temperature difference by subtracting the indoor environment temperature from the outdoor environment temperature; acquiring an outdoor fan nominal speed limit range and a pump speed limit range corresponding to the current indoor-outdoor environment temperature difference; acquiring a current speed of the pump; determining an actual speed upper limit within the outdoor fan nominal speed limit range, and setting the actual speed upper limit as a speed upper limit of the outdoor fan; wherein the closer the current speed is to a pump speed upper limit of the pump speed limit range, the closer the actual speed upper limit is to a nominal speed upper limit of the outdoor fan nominal speed limit range. The application aims to solve the technical problem of how to prevent the pump inlet from being cut off by excessive outdoor fan speed or insufficient pump speed when the indoor-outdoor environment temperature difference is large.

Description

Technical Field

[0001] This invention relates to air conditioning technology, specifically to an air conditioner and its control method. Background Technology

[0002] With increasingly stringent energy efficiency requirements for data centers, air conditioning systems in server rooms need to improve the utilization of natural cooling sources. Using refrigerant pumps for natural cooling can effectively improve the energy efficiency of the units.

[0003] Due to the significant lifespan advantage of centrifugal pumps, existing refrigerant pump-based natural cooling units in computer room air conditioning systems often use centrifugal pumps as the refrigerant transport device. However, when the refrigerant at the inlet of the centrifugal pump vaporizes, it can easily prevent the formation of a liquid seal within the pump, leading to a loss of pump head and flow interruption. Furthermore, during pump system operation, changes in the condenser fan speed can easily trigger refrigerant vaporization at the centrifugal pump inlet, causing system flow interruption. Summary of the Invention

[0004] The present invention aims to solve the technical problem of how to prevent refrigerant flow interruption at the pump inlet caused by excessive outdoor fan speed or insufficient pump speed when there is a large temperature difference between indoor and outdoor environments.

[0005] To achieve the above objectives, the present invention proposes a control method for an air conditioner, the air conditioner comprising: a condenser for exchanging heat with outdoor air, an evaporator for exchanging heat with indoor air, a pump for driving refrigerant to circulate between the condenser and the evaporator, and an outdoor fan for driving outdoor air to flow through the condenser.

[0006] The control method includes:

[0007] The indoor ambient temperature and the outdoor ambient temperature are obtained, and the difference between the indoor ambient temperature and the outdoor ambient temperature is calculated to obtain the current indoor and outdoor ambient temperature difference.

[0008] Obtain the nominal speed limit range of the outdoor fan and the pump speed limit range corresponding to the current indoor and outdoor temperature difference;

[0009] Get the current pump speed;

[0010] Within the nominal speed limit of the external fan, determine the upper limit of the actual speed, and set the upper limit of the actual speed as the upper limit of the speed of the external fan;

[0011] Wherein, the closer the current rotational speed is to the upper limit of the pump rotational speed limit range, the closer the actual upper limit of the rotational speed is to the upper limit of the nominal rotational speed limit range of the external fan.

[0012] In one illustrative embodiment, the lower limit of the pump speed range tends to increase with the increase of the indoor-outdoor temperature difference; and / or

[0013] The nominal speed limit and the nominal speed limit of the outdoor fan both tend to decrease as the temperature difference between indoor and outdoor environments increases.

[0014] In one illustrative embodiment, the actual upper limit of rotational speed is determined using the following formula:

[0015]

[0016] Where Zmax is the upper limit of actual speed, fc_min is the lower limit of nominal speed, fc_max is the upper limit of nominal speed, fp_real is the current speed of the pump, fp_min is the lower limit of pump speed, and fp_max is the upper limit of pump speed.

[0017] In one illustrative embodiment, it also includes:

[0018] The pump speed is kept constant as long as the absolute value of the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance.

[0019] The pump speed is increased because the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance.

[0020] When the difference between the indoor ambient temperature and the preset target temperature is less than the negative value of the preset temperature tolerance, the pump speed is reduced.

[0021] In one illustrative embodiment, the pump's speed increase rate and / or speed decrease rate is:

[0022]

[0023] In one illustrative embodiment, it also includes:

[0024] Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet;

[0025] Based on the fact that the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, and the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance, the speed of the outdoor fan is increased at the first preset rate.

[0026] In one illustrative embodiment, it also includes:

[0027] Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet;

[0028] Based on the fact that the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, and the current rotational speed is equal to the upper limit of the pump rotational speed, the rotational speed of the external fan is increased at a first preset rate.

[0029] In one illustrative embodiment, the first preset rate is negatively correlated with the current indoor-outdoor temperature difference.

[0030] In one illustrative embodiment, it also includes:

[0031] Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet;

[0032] When the difference between the current pressure and the preset target pressure is less than the negative value of the preset pressure tolerance, the speed of the external fan is reduced at the second preset rate.

[0033] In one illustrative embodiment, the second preset rate is negatively correlated with the current indoor-outdoor temperature difference.

[0034] In one illustrative embodiment, it also includes:

[0035] Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet;

[0036] Based on the absolute value of the difference between the current pressure and the preset target pressure being less than or equal to the preset pressure tolerance, the external fan speed is maintained constant; and / or

[0037] If the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, and the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance, or the current speed is not equal to the upper limit of the pump speed, the speed of the external fan is kept constant.

[0038] This application also proposes an air conditioner, which includes:

[0039] A condenser is used to exchange heat with outdoor air;

[0040] An evaporator is used to exchange heat with indoor air;

[0041] Pumps are used to drive the refrigerant to circulate between the condenser and the evaporator;

[0042] An external fan is used to drive outdoor air to flow through the condenser;

[0043] The detection component includes a first temperature sensor for detecting indoor ambient temperature and a second temperature sensor for detecting outdoor ambient temperature.

[0044] The controller is electrically connected to the first temperature sensor, the second temperature sensor, the pump, and the external fan;

[0045] The controller is configured to execute the control method described above.

[0046] In the technical solution of this application, the nominal speed limit range of the outdoor fan and the pump speed limit range are first determined based on the current indoor and outdoor temperature difference. The upper limit of the actual speed is the upper limit value of the outdoor fan speed, and the outdoor fan speed is limited to only being below the upper limit of the actual speed. The range of the upper limit of the actual speed is the nominal speed limit range of the outdoor fan, and the upper limit of the actual speed is related to the current speed of the pump. The higher the current speed of the pump within the pump speed limit range, the higher the value of the upper limit of the actual speed; the lower the current speed of the pump within the pump speed limit range, the lower the value of the upper limit of the actual speed. This can prevent refrigerant interruption at the pump inlet caused by excessive outdoor fan speed and / or insufficient pump speed when the indoor and outdoor temperature difference is large. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of an air conditioner according to an embodiment of this application;

[0049] Figure 2 This is a flowchart of a control method for an air conditioner according to an embodiment of this application;

[0050] Figure 3 This is a schematic diagram of the control flow of an air conditioner according to an embodiment of this application.

[0051] 1. Pump; 2. Throttling element; 3. Evaporator; 4. Condenser; 5. Liquid receiver; 6. Internal fan; 7. External fan; 8. First pressure sensor; 9. First check valve; 10. Second check valve; 11. Compressor.

[0052] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0054] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0055] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0058] like Figure 1 As shown, Figure 1 The structure of an air conditioner is shown. This air conditioner can be an in-row air conditioner or a computer room air conditioner. The air conditioner includes a casing, a pump 1, a throttling element 2, an evaporator 3, a condenser 4, a liquid receiver 5, an outdoor fan 7, and an indoor fan 6. The outlet of pump 1 is connected to the inlet of throttling element 2 via a pipeline. The outlet of throttling element 2 is connected to the inlet of evaporator 3 via a pipeline. The outlet of evaporator 3 is connected to condenser 4 via a pipeline. Condenser 4 is connected to the inlet of liquid receiver 5 via a pipeline. The outlet of liquid receiver 5 is connected to the inlet of pump 1. The piping of this refrigeration system contains a refrigerant, which can be a Freon refrigerant.

[0059] The air conditioner's casing contains an inner air duct and an outer air duct. Both the inlet and outlet of the inner air duct connect to the indoor space. The evaporator 3 and the internal fan 6 are both located within the inner air duct. The internal fan 6 drives the air within the inner air duct to flow from the inlet to the outlet, allowing indoor air to be drawn in through the inlet of the inner air duct and, after passing through the evaporator 3, discharged into the indoor space through the outlet. Indoor air exchanges heat with the evaporator 3 as it flows through it.

[0060] Both the inlet and outlet of the outer air duct are connected to the outdoor space. The condenser 4 and the outdoor fan 7 are both located within the outer air duct. The outdoor fan 7 drives the air within the outer air duct to flow from the inlet to the outlet, allowing outdoor air in the outdoor space to be drawn in through the inlet and discharged to the outdoor space through the outlet after passing through the condenser 4. Outdoor air exchanges heat with the condenser 4 as it flows through it.

[0061] Pump 1 can be an impeller pump, such as a centrifugal pump, axial flow pump, or mixed flow pump. During operation, pump 1 draws in liquid refrigerant from the inlet, pressurizes it, and then outputs it from the outlet. The refrigerant flows sequentially through the throttling element 2, evaporator 3, condenser 4, and receiver 5 before returning to pump 1. When the outdoor ambient temperature is low, the natural air is an abundant source of cooling. The refrigerant absorbs heat from the indoor air as it passes through evaporator 3, and releases this heat into the outdoor air as it passes through condenser 4, thus achieving cooling. Compared to using compressor 11 alone for cooling, this cooling method offers significant energy savings.

[0062] The air conditioner also includes a detection component and a controller. The detection component includes a first temperature sensor and a second temperature sensor. The first temperature sensor detects the indoor ambient temperature, also known as the return air temperature of the evaporator 3. The first temperature sensor is located within the inner air duct and upstream of the evaporator 3, and may be positioned at the inlet of the inner air duct. The second temperature sensor detects the outdoor ambient temperature, also known as the return air temperature of the condenser 4. The second temperature sensor is located within the outer air duct and upstream of the condenser 4, and may be positioned at the inlet of the outer air duct.

[0063] The controller is the logic control unit of the air conditioner and can be a microcontroller. The controller is electrically connected to the first temperature sensor, the second temperature sensor, and pump 1.

[0064] like Figure 2 As shown, this application also proposes a control method for an air conditioner, which is implemented based on the air conditioner described above. The control method includes the following steps:

[0065] Step S1: The controller acquires the indoor and outdoor ambient temperatures, and calculates the difference between the indoor and outdoor ambient temperatures to obtain the current indoor and outdoor temperature difference;

[0066] Users can send a command to start pump 1 in cooling mode to the air conditioner via remote control, smart terminal, or the air conditioner's control panel. This command instructs pump 1 to operate, enabling the air conditioner to cool. Upon receiving the command, the controller drives pump 1, outdoor fan 7, and indoor fan 6 to operate at their respective initial preset speeds. After pump 1 starts, it draws refrigerant in from its inlet, pressurizes it, and outputs it from its outlet, allowing the refrigerant to circulate between condenser 4 and evaporator 3. After outdoor fan 7 starts, it drives outdoor air to exchange heat with the refrigerant in condenser 4, thus lowering the temperature of the refrigerant in condenser 4. After indoor fan 6 starts, it drives indoor air to exchange heat with the refrigerant in evaporator 3, thus lowering the temperature of the indoor air.

[0067] When pump 1 is running, the controller measures the indoor ambient temperature using a first temperature sensor and the outdoor ambient temperature using a second temperature sensor. The controller subtracts the outdoor ambient temperature from the indoor ambient temperature to obtain the current indoor and outdoor temperature difference.

[0068] Step S2: The controller obtains the nominal speed limit range of the outdoor fan and the pump speed limit range corresponding to the current indoor and outdoor temperature difference;

[0069] The rotational speed of pump 1 determines the refrigerant flow rate, which in turn affects the heat exchange efficiency between condenser 4 and outdoor air, as well as between evaporator 3 and indoor air. A higher pump speed results in higher heat exchange efficiency between condenser 4 and outdoor air, and between evaporator 3 and indoor air. Both the heat exchange efficiency between condenser 4 and outdoor air, and between evaporator 3 and indoor air, directly affect the cooling capacity of the air conditioner; that is, a higher pump speed results in a greater cooling capacity. The temperature difference between indoor and outdoor environments also affects the cooling capacity of the air conditioner.

[0070] To ensure the air conditioner reaches its preset cooling capacity under varying indoor and outdoor temperature differences, the rotational speed of pump 1 needs to be limited. The relationship between the indoor and outdoor temperature difference and the pump speed limit range for maintaining the air conditioner above the preset cooling capacity can be pre-calibrated. The pump speed limit range restricts the rotational speed of pump 1; pump 1's speed can only be limited within this range. The pump speed limit range has an upper limit and a lower limit. The upper limit is the maximum value of the pump speed limit range, and the lower limit is the minimum value. The lower limit tends to increase with increasing indoor and outdoor temperature difference, and there can be a positive correlation between the lower limit and the indoor and outdoor temperature difference. The upper limit of the pump speed can be a fixed value, determined by the mechanical performance of pump 1, and can be the rated speed of pump 1.

[0071] For example, during the process of the indoor and outdoor temperature difference increasing from 0℃ to 67℃, the lower limit of the pump speed limit range increases from 45Hz to 60Hz, while the upper limit of the pump speed limit range remains unchanged at 60Hz.

[0072] In this way, the air conditioner controller can obtain the pump speed limit range corresponding to the current indoor and outdoor temperature difference based on the current indoor and outdoor temperature difference and the correspondence between the indoor and outdoor temperature difference and the pump speed limit range.

[0073] Meanwhile, the outdoor fan 7 blows outdoor air towards the condenser 4, and the outdoor air can carry away the heat from the refrigerant in the condenser 4. The higher the rotational speed of the outdoor fan 7, the higher the heat exchange efficiency between the outdoor air and the refrigerant.

[0074] To maintain the liquid refrigerant level in the storage tank 5 above a preset height, the rotational speed of the outdoor fan 7 needs to be limited under different indoor and outdoor temperature differences. The correspondence between the indoor and outdoor temperature difference and the nominal rotational speed limit of the outdoor fan can be pre-calibrated to maintain the liquid refrigerant level above the preset height. The nominal rotational speed limit has a lower limit and an upper limit; the upper limit is the uppermost value of the nominal rotational speed limit, and the lower limit is the lowermost value. Both the lower and upper limits tend to decrease as the indoor and outdoor temperature difference increases, and the lower limit of the pump speed can be negatively correlated with the indoor and outdoor temperature difference.

[0075] For example, during the process of the indoor and outdoor temperature difference rising from 0℃ to 67℃, the lower limit of the nominal speed of the outdoor fan decreases from 30% of the maximum speed of the outdoor fan to 0, and the upper limit of the nominal speed of the outdoor fan decreases from 70% of the maximum speed of the outdoor fan to 10% of the maximum speed of the outdoor fan.

[0076] In this way, the air conditioner controller can obtain the nominal speed limit range of the outdoor fan corresponding to the current indoor and outdoor temperature difference, as well as the correspondence between the indoor and outdoor temperature difference and the nominal speed limit range of the outdoor fan.

[0077] Step S3: The controller obtains the current speed of pump 1;

[0078] The speed of pump 1 is controlled by a controller, which can directly read the current speed information of pump 1. A speed measuring device electrically connected to the controller can also be installed in the air conditioner to measure the current speed of pump 1. The current speed of pump 1 is within the pump speed limit range.

[0079] Step S4: The controller determines the upper limit of the actual speed within the nominal speed limit of the outdoor fan, and sets the upper limit of the actual speed as the upper limit of the speed of the outdoor fan 7;

[0080] Among them, the closer the current speed of pump 1 is to the upper limit of the pump speed limit range, the closer the actual upper limit of the speed is to the upper limit of the nominal speed limit range of the external fan.

[0081] In this embodiment, the nominal speed limit range of the outdoor fan and the pump speed limit range are first determined based on the current indoor and outdoor temperature difference. The upper limit of the actual speed is the upper limit of the speed of the outdoor fan 7, and the speed of the outdoor fan 7 is limited to be below the upper limit of the actual speed. The range of the upper limit of the actual speed is the nominal speed limit range of the outdoor fan, and the upper limit of the actual speed is related to the current speed of the pump 1. The higher the current speed of the pump 1 is within the pump speed limit range, the higher the value of the upper limit of the actual speed; the lower the current speed of the pump 1 is within the pump speed limit range, the lower the value of the upper limit of the actual speed. This can prevent refrigerant interruption at the pump inlet caused by excessive speed of the outdoor fan 7 and / or insufficient speed of the pump when the indoor and outdoor temperature difference is large.

[0082] In an illustrative embodiment, in step S4, the upper limit of the actual rotational speed is calculated using the following formula:

[0083]

[0084] Where Zmax is the upper limit of actual speed, in %; fc_min is the lower limit of nominal speed, in %; fc_max is the upper limit of nominal speed, in %; fp_real is the current speed of pump 1, in Hz; fp_min is the lower limit of pump speed, in Hz; and fp_max is the upper limit of pump speed, in Hz.

[0085] Zmax (actual speed limit), fc_min (nominal speed limit), and fc_max (nominal speed limit) are all expressed as a percentage of the maximum speed of the external fan.

[0086] In this way, the position of the actual upper limit of the speed within the nominal speed limit range of the outdoor fan matches the position of the current speed of pump 1 within the pump speed limit range. This can further prevent refrigerant interruption caused by excessive speed of outdoor fan 7 when the temperature difference between indoor and outdoor environments is too large, as well as refrigerant interruption caused by excessive speed of pump 1.

[0087] In one illustrative embodiment, step S4 further includes: setting the actual speed lower limit to the speed lower limit of the external fan 7, wherein the actual speed lower limit is equal to the nominal speed lower limit of the nominal speed limit range of the external fan.

[0088] The actual speed lower limit is the lower limit of the speed of the outdoor fan 7. The speed of the outdoor fan 7 is limited to only being above the actual speed lower limit. When the speed of the outdoor fan 7 is equal to the actual speed lower limit, that is, when the speed of the outdoor fan 7 is equal to the nominal speed lower limit, the liquid level of the liquid refrigerant in the liquid storage tank 5 is not lower than the preset height, which can prevent refrigerant flow interruption at the pump inlet due to insufficient liquid refrigerant in the liquid storage tank 5.

[0089] In one illustrative embodiment, the control method further includes step S5 following step S4;

[0090] Step S5: The controller determines whether the absolute value of the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance. If yes, proceed to step S6; otherwise, proceed to step S7.

[0091] The preset target temperature is the target value for controlling the indoor ambient temperature, which can be set by the user. The range of the preset target temperature can be 24 to 45℃.

[0092] The preset temperature tolerance is a preset value. The preset temperature tolerance is the allowable deviation between the indoor ambient temperature and the preset target temperature.

[0093] When the preset temperature tolerance is greater than zero, for example, when the preset temperature tolerance is 0.5-2℃, if the deviation between the indoor ambient temperature and the preset target temperature is within the preset temperature tolerance, the indoor ambient temperature will not be adjusted, which can reduce the frequency of adjusting the indoor ambient temperature.

[0094] When the preset temperature tolerance is zero, the indoor ambient temperature needs to be adjusted whenever it deviates from the preset target temperature.

[0095] Step S6: The controller maintains the pump 1 speed constant and proceeds to step S1;

[0096] When the absolute value of the difference between the indoor ambient temperature and the preset target temperature is within the preset temperature tolerance range, there is no need to adjust the indoor ambient temperature and the speed of pump 1 remains unchanged.

[0097] Step S7: The controller determines whether the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance. If so, proceed to step S8; otherwise, proceed to step S9.

[0098] Step S8: The controller increases the speed of pump 1, proceeding to step S1;

[0099] The speed increase rate of pump 1 can be

[0100] When the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance, the indoor ambient temperature is too high. It is necessary to increase the speed of pump 1 to increase the cooling capacity of the air conditioner, thereby reducing the indoor ambient temperature so that the indoor ambient temperature can approach the preset target temperature.

[0101] Step S9: The controller reduces the speed of pump 1 and proceeds to step S1.

[0102] The rate at which the speed of pump 1 decreases can be

[0103] When the difference between the indoor ambient temperature and the preset target temperature is not greater than the preset temperature tolerance and the absolute value of the difference between the indoor ambient temperature and the preset target temperature is not less than or equal to the preset temperature tolerance, that is, when the difference between the indoor ambient temperature and the preset target temperature is less than the negative value of the preset temperature tolerance, the indoor ambient temperature is too low. It is necessary to reduce the speed of pump 1 to reduce the cooling capacity of the air conditioner, thereby increasing the indoor ambient temperature so that the indoor ambient temperature can approach the preset target temperature.

[0104] In this way, the air conditioner can adjust the indoor ambient temperature to the preset target temperature through steps S5 to S9.

[0105] In one illustrative embodiment, the detection assembly further includes a first pressure sensor 8. The first pressure sensor 8 may be located at the outlet of the evaporator 3, the inlet of the condenser 4, or the outlet of the condenser 4. The first pressure sensor 8 is used to measure the pressure at the outlet of the evaporator 3, the inlet of the condenser 4, or the outlet of the condenser 4.

[0106] The first pressure sensor 8 is electrically connected to the controller, and the first pressure sensor 8 can send the measurement results to the controller.

[0107] The control method also includes step S11 after step S4;

[0108] Step S11: The controller obtains the current pressure of the outlet of evaporator 3, the inlet of condenser 4, or the outlet of condenser 4, and proceeds to step S12.

[0109] The controller measures the current pressure at the outlet of the evaporator 3, the inlet of the condenser 4, or the outlet of the condenser 4 via the first pressure sensor 8.

[0110] Step S12: The controller determines whether the absolute value of the difference between the current pressure and the preset target pressure is less than or equal to the preset pressure tolerance. If yes, proceed to step S13; otherwise, proceed to step S14.

[0111] The preset target pressure is the pressure control target value at the outlet of evaporator 3, the inlet of condenser 4, or the outlet of condenser 4. In order to maintain stable operation of the air conditioner, the pressure at the outlet of evaporator 3, the inlet of condenser 4, or the outlet of condenser 4 needs to reach the preset target pressure.

[0112] When the first pressure sensor 8 measures the pressure at the outlet of the evaporator 3, the preset target pressure is the pressure control target value at the outlet of the evaporator 3. When the first pressure sensor 8 measures the pressure at the inlet of the condenser 4, the preset target pressure is the pressure control target value at the inlet of the condenser 4. When the first pressure sensor 8 measures the pressure at the outlet of the condenser 4, the preset target pressure is the pressure control target value at the outlet of the condenser 4.

[0113] The preset target pressure is an empirical value that can be calibrated in advance through experiments. The range of the preset target pressure can be 0.8-1.5 MPa.

[0114] The preset pressure tolerance is a preset value. The preset pressure tolerance is the allowable deviation of the pressure at the outlet of evaporator 3, the inlet of condenser 4, or the outlet of condenser 4 from the preset target pressure.

[0115] When the preset pressure tolerance is greater than zero, for example, when the preset pressure tolerance is 0.01-0.06 MPa, if the deviation between the pressure at the outlet of evaporator 3, the inlet of condenser 4, or the outlet of condenser 4 and its preset target pressure is within the preset pressure tolerance, then the refrigerant pressure will not be adjusted, which can reduce the frequency of adjusting the refrigerant pressure.

[0116] When the preset pressure tolerance is zero, the refrigerant pressure needs to be adjusted whenever the pressure at the outlet of evaporator 3, the inlet of condenser 4, or the outlet of condenser 4 deviates from its preset target pressure.

[0117] Step S13: The controller maintains the speed of the external fan 7 unchanged and proceeds to step S1;

[0118] If the absolute value of the difference between the current pressure and the preset target pressure is less than or equal to the preset pressure tolerance, then there is no need to adjust the refrigerant pressure and the speed of the outdoor fan 7 remains unchanged.

[0119] Step S14: The controller determines whether the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance. If so, proceed to step S15; otherwise, proceed to step S18.

[0120] Step S15: The controller determines whether the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance. If yes, proceed to step S17; otherwise, proceed to step S16.

[0121] Step S16: The controller determines whether the current speed of pump 1 is equal to the upper limit of the pump speed limit range. If yes, proceed to step S17; otherwise, proceed to step S13.

[0122] Step S17: The controller increases the speed of the external fan 7 at a first preset rate, and proceeds to step S1.

[0123] Thus, when the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, the speed of the outdoor fan 7 needs to be increased to cause more refrigerant to condense into liquid refrigerant, thereby reducing the refrigerant pressure in the pipes. If the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance, the speed of pump 1 continues to increase to lower the indoor ambient temperature. At this time, the refrigerant pressure is unstable, and the controller does not adjust the speed of the outdoor fan 7. When the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance, the speed of pump 1 remains unchanged. Only then is the speed of the outdoor fan 7 increased to reduce the refrigerant pressure in the pipes, making the current pressure closer to the preset target pressure without causing refrigerant flow interruption at the pump inlet. However, if the current speed of pump 1 is equal to the upper limit of the pump speed limit range, even if the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance, the speed of pump 1 cannot continue to increase and can only be maintained at the upper limit of the pump speed. At this time, the speed of pump 1 is at a relatively high speed, and increasing the speed of the outdoor fan 7 can prevent refrigerant flow interruption at the pump inlet.

[0124] Step S18: The controller reduces the speed of the external fan 7 at the second preset rate and proceeds to step S1.

[0125] In this way, when the absolute value of the difference between the current pressure and the preset target pressure is not less than or equal to the preset pressure tolerance, and when the difference between the current pressure and the preset pressure is not greater than the preset pressure tolerance, that is, when the difference between the current pressure and the preset target pressure is less than the negative value of the preset pressure tolerance, the speed of the external fan 7 is reduced to make less refrigerant condense into liquid refrigerant, thereby increasing the pressure of the refrigerant in the pipe, and thus making the current pressure closer to the preset target pressure.

[0126] In an illustrative embodiment, in step S17, the first preset rate is negatively correlated with the current indoor and outdoor temperature difference. The value of the first preset rate ranges from one percent of the maximum speed of the outdoor fan 7 every 120 seconds to one percent of the maximum speed of the outdoor fan 7 every 1 second.

[0127] The greater the temperature difference between the indoor and outdoor environments, the lower the rate of increase in the speed of the outdoor fan 7; conversely, the smaller the temperature difference between the indoor and outdoor environments, the higher the rate of increase in the speed of the outdoor fan 7.

[0128] When the temperature difference between the indoor and outdoor environments is large, the risk of refrigerant flow interruption at the pump inlet is high. In this case, increasing the speed of the outdoor fan 7 at a relatively small rate can reduce the risk of flow interruption and ensure reliable system operation. When the temperature difference between the indoor and outdoor environments is small, the risk of flow interruption is low. In this case, increasing the speed of the outdoor fan 7 at a relatively large rate can quickly bring the air conditioner to its full capacity.

[0129] In an illustrative embodiment, in step S18, the second preset rate is negatively correlated with the current indoor and outdoor temperature difference. The value of the second preset rate ranges from one percent of the maximum speed of the outdoor fan 7 every 120 seconds to one percent of the maximum speed of the outdoor fan 7 every 1 second.

[0130] The greater the temperature difference between the indoor and outdoor environments, the lower the rate of decrease in the speed of the outdoor fan 7; conversely, the smaller the temperature difference between the indoor and outdoor environments, the higher the rate of decrease in the speed of the outdoor fan 7.

[0131] When the temperature difference between the indoor and outdoor environments is large, the risk of flow interruption is higher. In this case, reducing the speed of the outdoor fan 7 at a smaller rate can reduce the risk of flow interruption and make the system operate reliably. When the temperature difference between the indoor and outdoor environments is small, the risk of flow interruption is lower. In this case, reducing the speed of the outdoor fan 7 at a larger rate can quickly bring the air conditioner into operation.

[0132] In one illustrative embodiment, the air conditioner further includes a first one-way valve 9, a second one-way valve 10, and a compressor 11. The two ends of the first one-way valve 9 are respectively connected to the outlet of the liquid storage tank 5 and the inlet of the throttling element 2.

[0133] The first check valve 9 allows only refrigerant flowing from the reservoir 5 to the throttling element 2. The first check valve 9 is connected in parallel with the pump 1.

[0134] The second one-way valve 10 is connected to the outlet of the evaporator 3 and the inlet of the condenser 4, respectively. The second one-way valve 10 can only allow refrigerant flowing from the evaporator 3 to the condenser 4. The inlet and outlet of the compressor 11 are connected to the outlet of the evaporator 3 and the inlet of the condenser 4, respectively. The compressor 11 is connected in parallel with the second one-way valve 10.

[0135] Thus, when pump 1 is running and compressor 11 is not running, the refrigerant circulates in the liquid receiver 5, pump 1, throttling element 2, evaporator 3, second check valve 10 and condenser 4; when compressor 11 is running and pump 1 is not running, the refrigerant circulates in the liquid receiver 5, first check valve 9, throttling element 2, evaporator 3, compressor 11 and condenser 4.

[0136] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A control method for an air conditioner, characterized in that, The air conditioner includes: a condenser for exchanging heat with outdoor air, an evaporator for exchanging heat with indoor air, a pump for driving refrigerant to circulate between the condenser and the evaporator, and an outdoor fan for driving outdoor air to flow through the condenser. The control method includes: The indoor ambient temperature and the outdoor ambient temperature are obtained, and the difference between the indoor ambient temperature and the outdoor ambient temperature is calculated to obtain the current indoor and outdoor ambient temperature difference. Obtain the nominal speed limit range of the outdoor fan and the pump speed limit range corresponding to the current indoor and outdoor temperature difference; Get the current pump speed; Determine the upper limit of the actual speed within the nominal speed limit of the external fan, and set the upper limit of the actual speed as the upper limit of the speed of the external fan; Wherein, the closer the current rotational speed is to the upper limit of the pump rotational speed limit range, the closer the actual upper limit of the rotational speed is to the upper limit of the nominal rotational speed limit range of the external fan.

2. The control method according to claim 1, characterized in that, The lower limit of the pump speed within the specified pump speed range tends to increase with the increase of the temperature difference between indoor and outdoor environments; and / or The nominal speed limit and the nominal speed limit of the outdoor fan both tend to decrease as the temperature difference between indoor and outdoor environments increases.

3. The control method according to claim 1 or 2, characterized in that, The actual upper limit of rotational speed is determined using the following formula: Where Zmax is the upper limit of actual speed, fc_min is the lower limit of nominal speed, fc_max is the upper limit of nominal speed, fp_real is the current speed of the pump, fp_min is the lower limit of pump speed, and fp_max is the upper limit of pump speed.

4. The control method according to claim 1, characterized in that, Also includes: The pump speed is kept constant as long as the absolute value of the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance. The pump speed is increased because the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance. When the difference between the indoor ambient temperature and the preset target temperature is less than the negative value of the preset temperature tolerance, the pump speed is reduced.

5. The control method according to claim 4, characterized in that, The pump's speed increase rate and / or speed decrease rate are 6. The control method according to claim 4, characterized in that, Also includes: Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet; Based on the fact that the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, and the difference between the indoor ambient temperature and the preset target temperature is less than or equal to the preset temperature tolerance, the speed of the outdoor fan is increased at the first preset rate.

7. The control method according to claim 4, characterized in that, Also includes: Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet; Based on the fact that the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, and the current rotational speed is equal to the upper limit of the pump rotational speed, the rotational speed of the external fan is increased at a first preset rate.

8. The control method according to claim 6 or 7, characterized in that, The first preset rate is negatively correlated with the current indoor and outdoor temperature difference.

9. The control method according to claim 4, characterized in that, Also includes: Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet; When the difference between the current pressure and the preset target pressure is less than the negative value of the preset pressure tolerance, the speed of the external fan is reduced at the second preset rate.

10. The control method according to claim 9, characterized in that, The second preset rate is negatively correlated with the current indoor and outdoor temperature difference.

11. The control method according to claim 4, characterized in that, Also includes: Obtain the current pressure at the evaporator outlet, condenser inlet, or condenser outlet; Based on the fact that the absolute value of the difference between the current pressure and the preset target pressure is less than or equal to the preset pressure tolerance, the speed of the external fan is kept constant. and / or If the difference between the current pressure and the preset pressure is greater than the preset pressure tolerance, and the difference between the indoor ambient temperature and the preset target temperature is greater than the preset temperature tolerance, or the current speed is not equal to the upper limit of the pump speed, the speed of the external fan is kept constant.

12. An air conditioner, characterized in that, include: A condenser is used to exchange heat with outdoor air; An evaporator is used to exchange heat with indoor air; Pumps are used to drive the refrigerant to circulate between the condenser and the evaporator; An external fan is used to drive outdoor air to flow through the condenser; The detection component includes a first temperature sensor for detecting indoor ambient temperature and a second temperature sensor for detecting outdoor ambient temperature. The controller is electrically connected to the first temperature sensor, the second temperature sensor, the pump, and the external fan; The controller is configured to perform the control method as described in any one of claims 1 to 11.

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