Control method of electronic expansion valve

Abstract

The invention discloses a control method of an electronic expansion valve, which comprises the following steps: when a compressor operates normally, acquiring a low-pressure transmission enabling state; judging whether the low-pressure transmission enabling state is forbidden or not; if the low-pressure transmission enabling state is forbidden, the air suction temperature and the downstream temperature are obtained; calculating the current superheat degree, wherein the current superheat degree is equal to the suction temperature minus the downstream temperature; if the low-pressure transmission enabling state is not forbidden, the suction temperature and the saturated evaporation temperature are obtained; calculating the current superheat degree, wherein the current superheat degree is equal to the suction temperature-the saturated evaporation temperature; the target superheat degree is obtained, the superheat degree deviation is calculated, and the superheat degree deviation = the current superheat degree-the target superheat degree; according to the superheat degree deviation, the required opening degree is obtained; and the opening degree of the electronic expansion valve is adjusted to the required opening degree. Therefore, the corresponding required opening degree can be obtained according to the current superheat degree, the low-pressure transmission enabling state, the operation mode and the corresponding target multi-heat degree, and therefore the opening degree of the electronic expansion valve can be adjusted in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to a control method of an electronic expansion valve. Background Art

[0002] The electronic expansion valve is an electronic regulating device that adjusts the liquid supply of the evaporator based on a preset program. Its core consists of three parts: the controller, the actuator, and the sensor. As the core device of the system, the controller is similar to the brain of the human body. It is responsible for receiving signals from the pressure sensor and the temperature sensor, and sends out pulse signals through internal calculations based on these signals to control the opening of the electronic expansion valve to ensure the appropriate amount of liquid supply and the appropriate superheat. Specifically, the control logic of the electronic expansion valve includes the following key points:

[0003] Sensor detection: The pressure sensor detects the evaporation pressure and converts the evaporation pressure value into a 4-20mA current signal; the temperature sensor changes its resistance value according to the temperature. These detected signals are sent to the controller. Controller processing: The controller receives the signals from the pressure sensor and the temperature sensor, calculates the current actual superheat through internal calculations, and compares it with the set parameters to calculate the required superheat that should be achieved. Actuator action: According to the difference between the actual superheat and the required superheat, combined with the parameter setting of the controller, the opening of the electronic expansion valve is adjusted in a certain reaction mode to make it as close to the required superheat as possible. This process is realized by the actuator of the electronic expansion valve. The actuator adjusts the valve opening according to the instructions of the controller, thereby changing the flow area of ​​the valve port. In short, the control logic of the electronic expansion valve is a closed-loop control system. The system status is detected by the sensor, the controller issues a control instruction according to the detected status, and the actuator adjusts the valve opening according to the instruction, thereby realizing the optimal control of the system.

[0004] The above is the control logic and method of the electronic expansion valve in the current conventional refrigeration system. However, in actual operation, there will be many uncontrollable and unquantifiable factors that affect the control of the electronic expansion valve; for example, after the unit is shut down, the system is not completely balanced, and restarting it will cause system failure; if the unit is defrosted according to the conventional superheat control, it will cause system failures such as incomplete defrosting and high pressure; in order to solve the above uncontrollable factors, the control logic of the electronic expansion valve is subdivided and controlled on demand. Summary of the invention

[0005] In view of the above-mentioned deficiencies, the technical problem to be solved by the present invention is: to provide a control method for an electronic expansion valve, to obtain the corresponding required opening according to the current superheat, low-pressure pressure transmission enabling state, operating mode and corresponding target multi-heat, thereby realizing real-time adjustment of the opening of the electronic expansion valve to solve the conventional problems.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A control method for an electronic expansion valve comprises the following steps:

[0008] S10, determining whether the compressor is in normal operation;

[0009] S20: If the compressor is in normal operation, obtain the low-pressure transmission enabling state;

[0010] S30, determining whether the low-voltage transmission enabling state is disabled;

[0011] S40, if the low pressure transmission enable state is disabled, obtain the suction temperature and the valve after temperature;

[0012] Then calculate the current superheat, current superheat = suction temperature - valve after temperature;

[0013] If the low pressure transmission enable status is not disabled, obtain the suction temperature and saturated evaporation temperature;

[0014] Then calculate the current superheat, current superheat = suction temperature - saturated evaporation temperature;

[0015] S50, obtaining a target superheat, and then calculating a superheat deviation, where superheat deviation = current superheat - target superheat;

[0016] S60, obtaining the required opening degree according to the superheat deviation;

[0017] S70: Adjust the opening of the electronic expansion valve to the required opening.

[0018] Preferably, the S20 includes:

[0019] If the compressor is in normal operation, determine whether the system is operating in defrost mode;

[0020] If the system is running in defrost mode, the electronic expansion valve is controlled to be fully open;

[0021] If the system is not running in defrost mode, obtain the status of low pressure transmission enable.

[0022] Preferably, the S20 includes:

[0023] If the compressor is not in normal operation, determine whether it is shut down or shut down due to a fault;

[0024] If the machine is shut down or shut down due to a fault, the current opening is obtained and maintained for s seconds, and then the valve closing action is performed according to the current opening + 160 steps to close the electronic expansion valve before shutting down.

[0025] Preferably, the post-valve temperature is the inner disk temperature in cooling mode, and the post-valve temperature is the outer disk temperature in heating mode; and / or, the saturated evaporation temperature is a temperature value calculated according to the current low pressure.

[0026] Preferably, the S10 includes:

[0027] Determine whether the compressor is in power-on state;

[0028] If the compressor is powered on, the electronic expansion valve is controlled to reset to zero;

[0029] After zero resetting, adjust the opening of the electronic expansion valve to the preset standby opening.

[0030] Preferably, the S10 further includes:

[0031] Determine whether the system is started and running;

[0032] If the system is up and running, get the ambient temperature;

[0033] According to the ambient temperature, the corresponding initial opening is obtained;

[0034] Adjust the opening of the electronic expansion valve to the initial opening.

[0035] Preferably, the step of obtaining the corresponding initial opening according to the ambient temperature comprises:

[0036] Determine whether the current operation is in heating mode or cooling mode;

[0037] If the current operation is in heating mode,

[0038] When the ambient temperature is ≥ 0.0℃, the initial opening degree = initial heating coefficient 1×(200+6.5t+0.15t 2 ), and the ambient temperature is ≥20.0℃, it shall be treated as 20.0℃;

[0039] When the ambient temperature is less than 0.0℃, the initial opening degree = initial heating coefficient 2×(200+4.9t+0.09t 2 ), if the ambient temperature is ≤-20.0℃, it shall be treated as -20.0℃; t is the ambient temperature;

[0040] If the current operation is in cooling mode, the initial opening degree = initial cooling coefficient × (500-24t+0.6t 2 );

[0041] If the ambient temperature is ≤20.0℃, it shall be treated as 20.0℃; if the ambient temperature is ≥45.0℃, it shall be treated as 45.0℃; t is the ambient temperature.

[0042] Preferably, the control method further comprises the following steps:

[0043] After the compressor is powered on, determine whether the compressor needs to be started;

[0044] If there is a startup requirement, obtain the absolute value of the high and low pressure difference;

[0045] Determine whether the absolute value of the high and low pressure difference is greater than the preset starting pressure difference;

[0046] If the absolute value of the high and low pressure difference is greater than the starting pressure difference, adjust the starting pressure difference to control the electronic expansion valve to fully open;

[0047] If the absolute value of the high and low pressure difference is not greater than the starting pressure difference, the compressor starts and adjusts the opening of the electronic expansion valve to the initial opening.

[0048] Preferably, the target superheat in S50 is obtained by the following steps: obtaining a corresponding superheat target value and a minimum opening value according to the ambient temperature;

[0049] The S70 further includes: determining whether the required opening is less than the minimum opening value;

[0050] If the required opening is less than the minimum opening value, adjust the opening of the electronic expansion valve to the minimum opening value;

[0051] If the required opening is not less than the minimum opening value, adjust the opening of the electronic expansion valve to the required opening.

[0052] Preferably, the S60 includes:

[0053] When the superheat deviation is greater than zero, the required opening = current opening + preset valve opening adjustment step;

[0054] When the superheat deviation is less than zero, the required opening = current opening - preset valve opening adjustment step.

[0055] After adopting the above technical solution, the beneficial effects of the present invention are:

[0056] Due to the control method of the electronic expansion valve of the present invention, when the compressor is in normal operation, the state of low-pressure pressure transmission is obtained; it is determined whether the state of low-pressure pressure transmission is disabled; if the state of low-pressure pressure transmission is disabled, the suction temperature and the temperature after the valve are obtained; then the current superheat is calculated, and the current superheat = suction temperature - valve after temperature; if the state of low-pressure pressure transmission is not disabled, the suction temperature and the saturated evaporation temperature are obtained; then the current superheat is calculated, and the current superheat = suction temperature - saturated evaporation temperature; the target superheat is obtained, and then the superheat deviation is calculated, and the superheat deviation = current superheat - target superheat; according to the superheat deviation, the required opening is obtained; and the opening of the electronic expansion valve is adjusted to the required opening. It can be seen that the control method of the present invention obtains the corresponding required opening according to the current superheat, the low-pressure pressure transmission enabling state, the operating mode and the corresponding target multi-heat, thereby realizing the real-time adjustment of the opening of the electronic expansion valve to solve the conventional problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a flow chart of the control method of the electronic expansion valve in the present invention;

[0058] Figure 2 is a graph of target multi-heat, minimum opening and ambient temperature in cooling mode in the embodiment;

[0059] Figure 3 3 is a graph of target multi-temperature, minimum opening degree and ambient temperature in heating mode in the embodiment. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0061] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0062] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] like Figure 1 As shown, a control method for an electronic expansion valve comprises the following steps:

[0064] Step S10, determining whether the compressor is in a normal operating state;

[0065] Step S20: If the compressor is in normal operation, obtain the low pressure transmission enabling state;

[0066] Step S30, determining whether the low-voltage pressure transmission enabling state is disabled;

[0067] Step S40: if the low pressure transmission enable state is disabled, obtain the suction temperature and the after-valve temperature;

[0068] Then calculate the current superheat, current superheat = suction temperature - valve back temperature; the valve back temperature is the inner disk temperature in cooling mode, and the valve back temperature is the outer disk temperature in heating mode;

[0069] If the state of low pressure pressure transmission enabling is not disabled, that is, the state of low pressure pressure transmission enabling is enabled, the suction temperature and saturated evaporation temperature are obtained;

[0070] Then calculate the current superheat, current superheat = suction temperature - saturated evaporation temperature; the saturated evaporation temperature is the temperature value converted according to the current low pressure, that is, the saturated evaporation temperature is the calibration value.

[0071] Step S50, obtaining a target superheat, and then calculating a superheat deviation, where superheat deviation = current superheat - target superheat;

[0072] Step S60, obtain the required opening according to the superheat deviation; in this embodiment, when the superheat deviation is greater than zero, the required opening = current opening + preset valve opening adjustment step; when the superheat deviation is less than zero, the required opening = current opening - preset valve opening adjustment step.

[0073] Step S70: adjust the opening of the electronic expansion valve to the required opening.

[0074] The control method of the present invention mainly obtains the corresponding required opening according to the current superheat, low-pressure pressure transmission enabling state, operation mode and corresponding target multi-heat, thereby realizing real-time adjustment of the opening of the electronic expansion valve to solve conventional problems.

[0075] like Figure 1 As shown, step S20 in this embodiment includes:

[0076] If the compressor is in normal operation, determine whether the system is operating in defrost mode;

[0077] If the system is running in defrost mode, the electronic expansion valve is controlled to be fully open;

[0078] If the system is not running in defrost mode, obtain the status of low pressure transmission enable.

[0079] Through the above steps, it is ensured that when running in defrost mode, defrosting can be performed reliably and thoroughly to avoid causing system failure.

[0080] like Figure 1 As shown, step S20 in this embodiment includes:

[0081] If the compressor is not in normal operation, determine whether it is shut down or shut down due to a fault;

[0082] If the machine is shut down or shut down due to a fault, after obtaining and maintaining the current opening for s seconds, t can be but is limited to 10, and the valve closing action is performed according to the current opening + 160 steps to close the electronic expansion valve before shutting down.

[0083] Through the above steps, it is ensured that the electronic expansion valve can be reliably closed before the unit is shut down.

[0084] like Figure 1 As shown, step S10 in this embodiment includes:

[0085] Determine whether the compressor is in power-on state;

[0086] If the compressor is powered on, the electronic expansion valve is controlled to reset to zero;

[0087] After zero resetting, adjust the opening of the electronic expansion valve to the preset standby opening.

[0088] Through the above steps, the electronic expansion valve has a power-on self-checking function to ensure that the electronic expansion valve is in a closed state when powered on, so as to ensure the normal operation of the compressor and the unit.

[0089] like Figure 1 As shown, step S10 in this embodiment further includes:

[0090] Determine whether the system is started and running;

[0091] If the system is started and running, obtain the ambient temperature t;

[0092] According to the ambient temperature t, the corresponding initial opening is obtained;

[0093] Adjust the opening of the electronic expansion valve to the initial opening.

[0094] In this embodiment, the steps of obtaining the corresponding initial opening according to the ambient temperature t include:

[0095] Determine whether the current operation is in heating mode or cooling mode;

[0096] If the current operation is in heating mode,

[0097] When the ambient temperature is ≥ 0.0℃, the initial opening degree = initial heating coefficient 1×(200+6.5t+0.15t 2 ), and the ambient temperature is ≥20.0℃, it is treated as 20.0℃; the heating initial coefficient 1 is the preset value; t is the ambient temperature.

[0098] When the ambient temperature is less than 0.0℃, the initial opening degree = initial heating coefficient 2×(200+4.9t+0.09t 2 ), if the ambient temperature is ≤-20.0℃, it will be treated as -20.0℃; the initial heating coefficient 2 is the preset value; t is the ambient temperature.

[0099] If the current operation is in cooling mode, the initial opening degree = initial cooling coefficient × (500-24t+0.6t 2 ); and if the ambient temperature is ≤20.0℃, it is treated as 20.0℃; if the ambient temperature is ≥45.0℃, it is treated as 45.0℃; the initial refrigeration coefficient is the preset value; t is the ambient temperature.

[0100] Through the above steps, the initial opening of the electronic expansion valve is adjusted according to the ambient temperature t to obtain a corresponding initial opening, thereby ensuring reliable operation of the compressor and the entire system.

[0101] The control method in this embodiment further includes the following steps:

[0102] After the compressor is powered on, determine whether the compressor needs to be started;

[0103] If there is a startup requirement, obtain the absolute value of the high and low pressure difference;

[0104] Determine whether the absolute value of the high and low pressure difference is greater than the preset starting pressure difference;

[0105] If the absolute value of the high and low pressure difference is greater than the starting pressure difference, adjust the starting pressure difference to control the electronic expansion valve to fully open;

[0106] If the absolute value of the high and low pressure difference is not greater than the starting pressure difference, the compressor starts and adjusts the opening of the electronic expansion valve to the initial opening.

[0107] Through the above steps, when the compressor needs to be started, the compressor can be started normally only after the high and low pressure differences meet the requirements of the starting pressure difference, thus solving the problem of unbalanced pressure difference.

[0108] In this embodiment, the target superheat in step S50 is obtained by the following steps:

[0109] Get the ambient temperature t;

[0110] Then, according to the ambient temperature t, the corresponding superheat target value and minimum opening value are obtained;

[0111] Step S70 also includes: determining whether the required opening is less than the minimum opening value;

[0112] If the required opening is less than the minimum opening value, adjust the opening of the electronic expansion valve to the minimum opening value;

[0113] If the required opening is not less than the minimum opening value, adjust the opening of the electronic expansion valve to the required opening.

[0114] In this embodiment, the superheat target value and the minimum opening value specifically include the following two situations:

[0115] like Figure 2 As shown, when the system is running in cooling mode, the ambient temperature t obtains the corresponding target superheat and minimum opening according to the following Table 1, which is specifically divided into temperature rising trend and temperature falling trend, see Table 1 for details:

[0116] Temperature rising trend Temperature decreasing trend Target superheat Minimum opening 37.0℃≤t 35.0℃＜t Refrigeration superheat 1 Minimum cooling opening 1 27.0℃≤t＜37.0℃ 25.0℃＜t≤35.0℃ Refrigeration superheat 2 Refrigeration minimum opening 2 t＜27.0℃ t≤25.0℃ Refrigeration superheat 3 Minimum cooling opening 3

[0117] like Figure 3 As shown, when the system is running in heating mode, the ambient temperature t obtains the corresponding target superheat and minimum opening according to the following Table 2, which is specifically divided into temperature rising trend and temperature falling trend, see Table 2 for details:

[0118] Table 2:

[0119] Ambient temperature rise process Ambient temperature drop process Target superheat Minimum opening 15.0℃≤t 13.0℃＜t Heating superheat 1 Heating minimum opening 1 7.0℃≤t＜15.0℃ 5.0℃＜t≤13.0℃ Heating superheat 2 Heating minimum opening 2 0.0℃≤t＜7.0℃ -2.0℃＜t≤5.0℃ Heating superheat 3 Heating minimum opening 3 -6.0℃≤t＜0.0℃ -8.0℃＜t≤-2.0℃ Heating superheat 4 Heating minimum opening 4 -12.0℃≤t＜-6.0℃ -14.0℃＜t≤-8.0℃ Heating superheat 5 Heating minimum opening 5 t＜-12.0℃ t≤-14.0℃ Heating superheat 6 Heating minimum opening 6

[0120] In summary, the control method of the electronic expansion valve of the present invention realizes power-on reset and self-checking; the superheat is preset according to the ambient temperature before the point; after the unit is shut down, the system is not completely balanced, and restarting it will cause, avoiding system failure; when the unit is defrosted, the electronic expansion valve is fully opened to avoid system failures such as incomplete defrosting and high pressure.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made within the spirit and principles of the present invention, improvements in the control method of an electronic expansion valve, etc., should be included in the protection scope of the present invention.

Claims

1. A control method for an electronic expansion valve, characterized in that: The following steps are involved: S10, determining whether the compressor is in normal operation; S20: If the compressor is in normal operation, obtain the low-pressure transmission enabling state; S30, determining whether the low-voltage transmission enabling state is disabled; S40, if the low pressure transmission enable state is disabled, obtain the suction temperature and the valve after temperature; Then calculate the current superheat, current superheat = suction temperature - valve after temperature; If the low pressure transmission enable status is not disabled, obtain the suction temperature and saturated evaporation temperature; Then calculate the current superheat, current superheat = suction temperature - saturated evaporation temperature; S50, obtaining a target superheat, and then calculating a superheat deviation, where superheat deviation = current superheat - target superheat; S60, obtaining the required opening degree according to the superheat deviation; S70: Adjust the opening of the electronic expansion valve to the required opening.

2. The control method of the electronic expansion valve according to claim 1, characterized in that: The S20 includes: If the compressor is in normal operation, determine whether the system is operating in defrost mode; If the system is running in defrost mode, the electronic expansion valve is controlled to be fully open; If the system is not running in defrost mode, obtain the status of low pressure transmission enable.

3. The control method of the electronic expansion valve according to claim 1, characterized in that: The S20 includes: If the compressor is not in normal operation, determine whether it is shut down or shut down due to a fault; If the machine is shut down or shut down due to a fault, the current opening is obtained and maintained for s seconds, and then the valve closing action is performed according to the current opening + 160 steps to close the electronic expansion valve before shutting down.

4. The control method of the electronic expansion valve according to claim 1, characterized in that: The post-valve temperature is the inner disk temperature in cooling mode, and the post-valve temperature is the outer disk temperature in heating mode; and / or, the saturated evaporation temperature is a temperature value converted according to the current low pressure.

5. The control method of the electronic expansion valve according to claim 1, characterized in that: The S10 includes: Determine whether the compressor is in power-on state; If the compressor is powered on, the electronic expansion valve is controlled to reset to zero; After zero resetting, adjust the opening of the electronic expansion valve to the preset standby opening.

6. The control method of the electronic expansion valve according to claim 5, characterized in that: The S10 further includes: Determine whether the system is started and running; If the system is up and running, get the ambient temperature; According to the ambient temperature, the corresponding initial opening is obtained; Adjust the opening of the electronic expansion valve to the initial opening.

7. The control method of the electronic expansion valve according to claim 6, characterized in that: The step of obtaining the corresponding initial opening degree according to the ambient temperature comprises: Determine whether the current operation is in heating mode or cooling mode; If the current operation is in heating mode, When the ambient temperature is ≥ 0.0℃, the initial opening degree = initial heating coefficient 1×(200+6.5t+0.15t 2 ), and the ambient temperature is ≥20.0℃, it shall be treated as 20.0℃; When the ambient temperature is less than 0.0℃, the initial opening degree = heating initial coefficient 2×(200+4.9t+0.09t 2 ), if the ambient temperature is ≤-20.0℃, it shall be treated as -20.0℃; t is the ambient temperature; If the current operation is in cooling mode, the initial opening degree = initial cooling coefficient × (500-24t+0.6t 2 ); If the ambient temperature is ≤20.0℃, it shall be treated as 20.0℃; if the ambient temperature is ≥45.0℃, it shall be treated as 45.0℃; t is the ambient temperature.

8. The control method of the electronic expansion valve according to claim 6, characterized in that: The control method further comprises the following steps: After the compressor is powered on, determine whether the compressor needs to be started; If there is a startup requirement, obtain the absolute value of the high and low pressure difference; Determine whether the absolute value of the high and low pressure difference is greater than the preset starting pressure difference; If the absolute value of the high and low pressure difference is greater than the starting pressure difference, adjust the starting pressure difference to control the electronic expansion valve to fully open; If the absolute value of the high and low pressure difference is not greater than the starting pressure difference, the compressor starts and adjusts the opening of the electronic expansion valve to the initial opening.

9. The control method of the electronic expansion valve according to claim 1, characterized in that: The target superheat in S50 is obtained by the following steps: obtaining a corresponding superheat target value and a minimum opening value according to the ambient temperature; The S70 further includes: determining whether the required opening is less than the minimum opening value; If the required opening is less than the minimum opening value, adjust the opening of the electronic expansion valve to the minimum opening value; If the required opening is not less than the minimum opening value, adjust the opening of the electronic expansion valve to the required opening.

10. The control method of the electronic expansion valve according to claim 1, characterized in that: The S60 includes: When the superheat deviation is greater than zero, the required opening = current opening + preset valve opening adjustment step; When the superheat deviation is less than zero, the required opening = current opening - preset valve opening adjustment step.

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