Energy-saving control method, system and device for keeping fixed position of electronic expansion valve, processor and computer readable storage medium thereof

Abstract

The invention relates to an energy-saving control method for keeping the fixed position of an electronic expansion valve, which comprises the following steps of: self-learning holding current, setting the holding current to be multi-gear adjustable, and when entering a position keeping mode, firstly reducing a driving current by one gear at set intervals from the maximum holding current, and then reducing the driving current by one gear at set intervals from the maximum holding current; and in the process, if the Hall signal is detected to change, the current pressure value is read immediately, the minimum current is set to be the previous gear of the holding current gear with the moved position, then the holding current is set to be the maximum holding current, and the operation is repeated until the Hall signal changes. And searching the minimum holding current capable of keeping the current pressure according to the steps. The invention also relates to a corresponding system, device, processor and computer readable storage medium. By adopting the method, the system, the device, the processor and the computer readable storage medium provided by the invention, certain accuracy and energy consumption saving effects are achieved.

Description

Technical Field

[0001] The present invention relates to stepper motor control, and in particular to an energy-saving control method, device, processor and computer-readable storage medium thereof for keeping an electronic expansion valve in a fixed position. Background Art

[0002] In the thermal management system of new energy vehicles, the expansion valve plays a vital role. The traditional control method to keep the expansion valve stationary is to apply a fixed current to a coil of the expansion valve to keep it in a relative position with the magnetic field of the stator, and the torque generated by it keeps the valve needle stable. As the performance of the car improves, the pressure range of the expansion valve needle is gradually increasing, and the instantaneous pressure it is subjected to changes rapidly with different usage scenarios. The expansion valve is easily pushed by external forces, causing it to lose step.

[0003] The current existing technology may have the following defects: when the current is kept fixed and the current is set to be low, it is easy to be pushed into position when encountering high voltage, and the position reliability cannot be guaranteed; when the driving current is set to be high, it is easy to cause serious heating of the motor, and a large amount of electricity is wasted at low voltage, which is not energy-saving and environmentally friendly. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide an energy-saving control method, device, processor and computer-readable storage medium thereof for maintaining a fixed position of an electronic expansion valve.

[0005] In order to achieve the above-mentioned object, the energy-saving control method, device, processor and computer-readable storage medium for maintaining a fixed position of an electronic expansion valve of the present invention are as follows:

[0006] The energy-saving control method for keeping the electronic expansion valve in a fixed position has the following main features:

[0007] The holding current of the electronic expansion valve is self-learned and adjustable in multiple gears;

[0008] When the electronic expansion valve stops at a certain position for a period of time, if no position movement instruction is received, it enters the position holding mode, and sets the holding current of the current position of the electronic expansion valve to the maximum holding current, and waits for a period of time for the valve needle to stabilize at the position;

[0009] The control system periodically reads the minimum holding current value of the electronic expansion valve within the corresponding pressure range;

[0010] The electronic expansion valve starts from the maximum holding current and decreases in sequence according to the preset current gradient;

[0011] Determine whether the current is the minimum holding current. If so, directly use the current holding current to keep the position stable. Otherwise, reduce the current by one level, keep it for a while, and wait for it to remain stable at the current position.

[0012] Determine whether the Hall signal changes at the current position of the electronic expansion valve. If no change occurs, stay at the current position to maintain stability; otherwise, update the current minimum current holding gear, set the current holding current to the maximum holding current, and read the position data;

[0013] Finally, according to the number of pulses generated by the Hall signal, the distance the electronic expansion valve moves is calculated, and the expansion valve is driven to perform position correction processing, thereby completing the cycle control.

[0014] Preferably, when the electronic expansion valve enters the position holding mode, minimum holding current data is obtained, and if the current holding current has not dropped to the minimum holding current, the current holding current is reduced by one level according to the current gradient until it drops to the minimum holding current.

[0015] Preferably, position signal detection processing is performed while the holding current is decreasing. If a change in the position signal is detected, the current holding current is recorded and the current pressure data is read, and the minimum holding current corresponding to the pressure data is increased by one level based on the holding current level.

[0016] Preferably, when the holding current drops to the minimum holding current, the position will be kept stable at this current, and the position signal will be periodically detected to see if it has changed. If a change in the position signal is detected, the current holding current will be recorded and the corresponding position data and pressure data will be read. At the same time, based on the current pressure range, the minimum holding current of this pressure range will be increased by one level based on the level of the original minimum holding current.

[0017] Preferably, when the minimum holding current changes, the latest minimum holding current is calculated and stored in a storage unit, wherein the stored data format divides the entire pressure range into a finite number of pressure levels, and each pressure level stores a corresponding minimum holding current value. When the minimum holding current value changes, the corresponding data is first updated to the minimum current array recording different pressure levels, and then stored in the storage unit.

[0018] The energy-saving control system for maintaining the fixed position of the electronic expansion valve for implementing the above-mentioned method has the following main features: the system comprises:

[0019] A position detection module, used to detect the signal change of the Hall element, thereby calculating the position of the valve core of the electronic expansion valve;

[0020] A storage unit, used to store the position information of the valve core and the minimum holding current data at different pressure levels;

[0021] The MCU performs corresponding data analysis and judgment processing by acquiring data information from the storage unit and the position detection module, thereby issuing a control instruction to the electronic expansion valve.

[0022] Preferably, the position detection module specifically performs the following processing:

[0023] The position of the valve core is calculated. When the stepper motor changes position, the Hall sensor of the position detection module transmits the corresponding Hall waveform. The MCU calculates the current position of the valve core through the detected Hall waveform. If the position is offset, the position correction is performed in time.

[0024] Preferably, when the valve needle of the electronic expansion valve stops at a certain position, the current position Locationdata is recorded, and before the system controller enters a sleep state, the current position Locationdata is written to the storage unit so that the current position of the valve needle can be immediately read upon waking up.

[0025] Preferably, after the electronic expansion valve enters the position holding mode, if the position moves, the minimum holding current gear corresponding to the pressure is written into the storage unit. Before storage, the system compares the minimum holding current under the corresponding pressure range with the minimum holding current when the position moves. If the minimum current gear is larger than the stored minimum current gear, the larger minimum current gear is written into the storage unit. Each time the system is initialized, it reads the minimum current gear of the corresponding pressure range into RAM for use.

[0026] Preferably, the MCU specifically performs the following processing:

[0027] The position signal transmitted by the position detection module is periodically detected. If a change in the position signal is detected, the current position data and pressure data are read and the holding current is immediately set to the maximum holding current, and holding processing is performed to stabilize the valve needle. Finally, the position correction is performed based on the calculated moving position.

[0028] The energy-saving control device for maintaining a fixed position of an electronic expansion valve has the following main features: the device comprises:

[0029] a processor configured to execute computer executable instructions;

[0030] The memory stores one or more computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the energy-saving control method for keeping the electronic expansion valve in a fixed position are implemented.

[0031] The energy-saving control processor for keeping the electronic expansion valve in a fixed position has the main feature that the processor is configured to execute computer-executable instructions, and when the computer-executable instructions are executed by the processor, the steps of the above-mentioned energy-saving control method for keeping the electronic expansion valve in a fixed position are implemented.

[0032] The main feature of the computer-readable storage medium is that a computer program is stored thereon, and the computer program can be executed by a processor to implement the steps of the above-mentioned energy-saving control method for keeping the electronic expansion valve in a fixed position.

[0033] The energy-saving control method, device, processor and computer-readable storage medium for maintaining a fixed position of an electronic expansion valve of the present invention are adopted to determine whether the expansion valve is out of step based on the pressure information collected near the expansion valve and the position variable obtained by the Hall sensor, and appropriately adjust the holding current and correct the position to keep it at the minimum energy consumption, thereby achieving the effect of energy saving and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a flow chart of the energy-saving control method for keeping the electronic expansion valve in a fixed position according to the present invention. DETAILED DESCRIPTION

[0035] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0036] Before describing in detail embodiments according to the present invention, it should be noted that, hereinafter, the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, whereby a process, method, article or apparatus comprising a series of elements includes not only these elements, but also other elements not explicitly listed or inherent to such process, method, article or apparatus.

[0037] See also Figure 1 As shown, the energy-saving control method for maintaining a fixed position of an electronic expansion valve, wherein the method comprises:

[0038] The holding current of the electronic expansion valve is self-learned and adjustable in multiple gears;

[0039] When the electronic expansion valve stops at a certain position for a period of time, if no position movement instruction is received, it enters the position holding mode, and sets the holding current of the current position of the electronic expansion valve to the maximum holding current, and waits for a period of time for the valve needle to stabilize at the position;

[0040] The control system periodically reads the minimum holding current value of the electronic expansion valve within the corresponding pressure range;

[0041] The electronic expansion valve starts from the maximum holding current and decreases in sequence according to the preset current gradient;

[0042] Determine whether the current is the minimum holding current. If so, directly use the current holding current to keep the position stable. Otherwise, reduce the current by one level, keep it for a while, and wait for it to remain stable at the current position.

[0043] Determine whether the Hall signal changes at the current position of the electronic expansion valve. If no change occurs, stay at the current position to maintain stability; otherwise, update the current minimum current holding gear, set the current holding current to the maximum holding current, and read the position data;

[0044] Finally, according to the number of pulses generated by the Hall signal, the distance the electronic expansion valve moves is calculated, and the expansion valve is driven to perform position correction processing, thereby completing the cycle control.

[0045] As a preferred embodiment of the present invention, when the electronic expansion valve enters the position holding mode, the minimum holding current data is obtained. If the current holding current has not dropped to the minimum holding current, the current holding current is reduced by one level according to the current gradient until it drops to the minimum holding current.

[0046] As a preferred embodiment of the present invention, position signal detection processing is performed during the process of maintaining the current decreasing. If a change in the position signal is detected, the current holding current is recorded and the current pressure data is read, and the minimum holding current corresponding to the pressure data is increased by one level based on the holding current level.

[0047] As a preferred embodiment of the present invention, when the holding current drops to the minimum holding current, the position will be kept stable at this current, and the position signal will be periodically detected to see if it has changed. If a change in the position signal is detected, the current holding current will be recorded and the corresponding position data and pressure data will be read. At the same time, based on the current pressure range, the minimum holding current of this pressure range will be increased by one level based on the level of the original minimum holding current.

[0048] As a preferred embodiment of the present invention, when the minimum holding current changes, the latest minimum holding current is calculated and stored in a storage unit, wherein the stored data format divides the entire pressure range into a finite number of pressure levels, and each pressure level stores a corresponding minimum holding current value. When the minimum holding current value changes, the corresponding data is first updated to the minimum current array recording different pressure levels, and then stored in the storage unit.

[0049] The energy-saving control system for maintaining a fixed position of an electronic expansion valve for implementing the above-mentioned method, wherein the system comprises:

[0050] A position detection module, used to detect the signal change of the Hall element, thereby calculating the position of the valve core of the electronic expansion valve;

[0051] A storage unit, used to store the position information of the valve core and the minimum holding current data at different pressure levels;

[0052] The MCU performs corresponding data analysis and judgment processing by acquiring data information of the storage unit and the position detection module, thereby sending control instructions to the electronic expansion valve. The control instructions include the size of the driving current and the direction and micro-step of the movement of the driving expansion valve.

[0053] As a preferred embodiment of the present invention, the position detection module specifically performs the following processing:

[0054] The position of the valve core is calculated. When the stepper motor changes position, the Hall sensor of the position detection module transmits the corresponding Hall waveform. The MCU calculates the current position of the valve core through the detected Hall waveform. If the position is offset, the position correction is performed in time.

[0055] As a preferred embodiment of the present invention, when the valve needle of the electronic expansion valve stops at a certain position, the current position Locationdata is recorded. Before the system controller enters a sleep state, the current position Locationdata is written to the storage unit so that the current position of the valve needle can be read immediately when awakened.

[0056] As a preferred embodiment of the present invention, when the electronic expansion valve enters the position holding mode, if the position moves, the minimum holding current gear of the corresponding pressure is written into the storage unit. Before storage, the system compares the minimum holding current under the corresponding pressure range with the minimum holding current when the position moves. If the minimum current gear is larger than the stored minimum current gear, the larger minimum current gear is written into the storage unit. Each time the system is initialized, the minimum current gear of the corresponding pressure range is read into RAM for use.

[0057] As a preferred embodiment of the present invention, the MCU specifically performs the following processing:

[0058] The position signal transmitted by the position detection module is periodically detected. If a change in the position signal is detected, the current position data and pressure data are read and the holding current is immediately set to the maximum holding current, and holding processing is performed to stabilize the valve needle. Finally, the position correction is performed based on the calculated moving position.

[0059] The energy-saving control device for maintaining a fixed position of an electronic expansion valve, wherein the device comprises:

[0060] a processor configured to execute computer executable instructions;

[0061] The memory stores one or more computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the energy-saving control method for keeping the electronic expansion valve in a fixed position are implemented.

[0062] The energy-saving control processor for keeping the electronic expansion valve in a fixed position, wherein the processor is configured to execute computer-executable instructions, and when the computer-executable instructions are executed by the processor, the steps of the energy-saving control method for keeping the electronic expansion valve in a fixed position are implemented.

[0063] The computer-readable storage medium stores a computer program, which can be executed by a processor to implement the steps of the energy-saving control method for maintaining a fixed position of an electronic expansion valve.

[0064] In actual applications, when the expansion valve stops at a certain position, the holding current is set according to the current gradient to the minimum holding current that keeps the position stationary. This control method is an adaptive holding current control method. When the position movement is detected, the minimum holding current in the pressure range will be learned and stored in the non-volatile memory. After the position is corrected, the expansion valve will operate with the minimum holding current that maintains the current position, thereby ensuring the reliability of the position and saving energy.

[0065] In practical applications, the self-learning of the holding current can be adjusted in multiple gears, and the maximum holding current is I a , the minimum holding current is I g (I a >I b >I c >I d …I g ), when entering the position holding mode, the drive current starts from the maximum holding current I a At the beginning, it drops one gear at a time, drops to the minimum holding current and maintains it. During this process, if the Hall signal changes, read the current pressure value immediately, set the minimum current to the previous gear of the holding current gear where the position moves, and then set the holding current to the maximum holding current. Repeat the above operation and follow the above steps to find the minimum current I that can maintain the current pressure. x .

[0066] The MCU determines whether the current position has moved based on the Hall signal. When the MCU detects a change in the Hall signal, it calculates the distance moved based on the number of pulses generated by the Hall signal and drives the expansion valve to correct the position to ensure the accuracy of the expansion valve position.

[0067] When the valve needle of the expansion valve stops at a certain position, the current pressure value and current gear should be immediately recorded in the storage unit when the position moves, so as to provide data support for the subsequent setting of the gear for maintaining the current.

[0068] A specific embodiment is given below to further illustrate the implementation details of this technical solution:

[0069] 1. When the expansion valve stops at a certain position for a period of time (taking 100ms as an example) and does not receive a position movement command, it enters the position holding mode. If a new position command is received, it exits the position holding mode.

[0070] 2. After entering the position holding mode, immediately set the holding current to the maximum holding current (the maximum holding current is the minimum holding current to keep the valve needle position stable under maximum pressure, taking 100ma as an example), and periodically detect the position signal. If there is no position signal change after a period of time, the holding current will be reduced by one gear until it drops to the minimum holding current.

[0071] 3. Before starting to reduce the holding current, it will be determined whether to start reducing the holding current based on the current data information. First, it will be determined whether there has been any position movement within the pressure range. If there has been any position movement within the pressure range, the minimum holding current that can be reduced within the pressure range is the previous gear of the holding current when the position movement occurred last time. Otherwise, the holding current will be gradually reduced to the normal minimum holding current Ig (The normal minimum holding current is 20ma).

[0072] 4. If a change in the position signal is detected during the process of holding the current downshift, the holding current will be immediately set to the maximum holding current to prevent moving to a larger position.

[0073] 5. After the position changes, the minimum holding current is set to the holding current of the previous gear where the position change occurred, the number of pulses of the movement is calculated and the expansion valve is driven to move to the previous stopped position.

[0074] 6. Write the minimum holding current of different pressure levels to the storage unit, and read the corresponding data each time after waking up from sleep mode.

[0075] In practical applications, after applying this technical solution, the following technical effects can be achieved:

[0076] Select a suitable holding current to reduce the power consumption of the expansion valve. The commonly used method is to set the holding current according to the maximum pressure. Assuming the holding current is 100ma, the holding current is set to 20ma at low pressure. According to the internal resistance of 20Ω, each expansion valve can reduce the power consumption by up to 0.192 kWh per day, thereby indirectly reducing CO2 emissions.

[0077] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0078] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device.

[0079] A person of ordinary skill in the art may understand that all or part of the steps of the method for implementing the above-mentioned embodiment may be completed by instructing the relevant hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0080] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0081] In the description of this specification, the description with reference to the terms "an embodiment", "some embodiments", "example", "specific example", or "embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0082] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0083] The energy-saving control method, device, processor and computer-readable storage medium for maintaining a fixed position of an electronic expansion valve of the present invention are adopted to determine whether the expansion valve is out of step based on the pressure information collected near the expansion valve and the position variable obtained by the Hall sensor, and appropriately adjust the holding current and correct the position to keep it at the minimum energy consumption, thereby achieving the effect of energy saving and emission reduction.

[0084] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. An energy-saving control method for maintaining a fixed position of an electronic expansion valve, characterized in that: The method includes: The holding current of the electronic expansion valve is self-learned and adjustable in multiple gears; When the electronic expansion valve stops at a certain position for a period of time, if no position movement instruction is received, it enters the position holding mode, and sets the holding current of the current position of the electronic expansion valve to the maximum holding current, and waits for a period of time for the valve needle to stabilize at the position; The control system periodically reads the minimum holding current value of the electronic expansion valve within the corresponding pressure range; The electronic expansion valve starts from the maximum holding current and decreases in sequence according to the preset current gradient; Determine whether the current is the minimum holding current. If so, directly use the current holding current to keep the position stable. Otherwise, reduce the current by one level, keep it for a while, and wait for it to remain stable at the current position. Determine whether the Hall signal changes at the current position of the electronic expansion valve. If no change occurs, stay at the current position to maintain stability; otherwise, update the current minimum current holding gear, set the current holding current to the maximum holding current, and read the position data; Finally, according to the number of pulses generated by the Hall signal, the distance the electronic expansion valve moves is calculated, and the expansion valve is driven to perform position correction processing, thereby completing the cycle control.

2. The energy-saving control method for maintaining a fixed position of an electronic expansion valve according to claim 1, characterized in that: When the electronic expansion valve enters the position holding mode, the minimum holding current data is obtained. If the current holding current has not dropped to the minimum holding current, the current holding current is reduced by one level according to the current gradient until it drops to the minimum holding current.

3. The energy-saving control method for maintaining a fixed position of an electronic expansion valve according to claim 2, characterized in that: The position signal detection process is performed while the holding current is decreasing. If a change in the position signal is detected, the current holding current is recorded and the current pressure data is read, and the minimum holding current corresponding to the pressure data is increased by one level based on the holding current level.

4. The energy-saving control method for maintaining a fixed position of an electronic expansion valve according to claim 2, characterized in that: When the holding current drops to the minimum holding current, the position will be kept stable at this current, and the position signal will be periodically detected to see if it has changed. If a change in the position signal is detected, the current holding current will be recorded and the corresponding position data and pressure data will be read. At the same time, based on the current pressure range, the minimum holding current of this pressure range will be increased by one level based on the original minimum holding current level.

5. The energy-saving control method for maintaining a fixed position of an electronic expansion valve according to claim 2, characterized in that: When the minimum holding current changes, the latest minimum holding current is calculated and stored in the storage unit, wherein the stored data format is to divide the entire pressure range into a finite number of pressure levels, and each pressure level stores the corresponding minimum holding current value. When the minimum holding current value changes, the corresponding data is first updated to the minimum current array recording different pressure levels, and then stored in the storage unit.

6. An energy-saving control system for maintaining a fixed position of an electronic expansion valve for implementing the method according to any one of claims 1 to 5, characterized in that: The system comprises: A position detection module, used to detect the signal change of the Hall element, thereby calculating the position of the valve core of the electronic expansion valve; A storage unit, used to store the position information of the valve core and the minimum holding current data at different pressure levels; The MCU performs corresponding data analysis and judgment processing by acquiring data information from the storage unit and the position detection module, thereby issuing a control instruction to the electronic expansion valve.

7. The energy-saving control system for maintaining a fixed position of an electronic expansion valve according to claim 6, characterized in that: The position detection module specifically performs the following processing: The position of the valve core is calculated. When the stepper motor changes position, the Hall sensor of the position detection module transmits the corresponding Hall waveform. The MCU calculates the current position of the valve core through the detected Hall waveform. If the position is offset, the position correction is performed in time.

8. The energy-saving control system for maintaining a fixed position of an electronic expansion valve according to claim 6, characterized in that: When the valve needle of the electronic expansion valve stops at a certain position, the current position Locationdata is recorded. Before the system controller enters the sleep state, the current position Locationdata is written to the storage unit so that the current position of the valve needle can be read immediately when awakened.

9. The energy-saving control system for maintaining a fixed position of an electronic expansion valve according to claim 6, characterized in that: When the electronic expansion valve enters the position holding mode, if the position moves, the minimum holding current gear of the corresponding pressure will be written into the storage unit. Before storage, the system will compare the minimum holding current under the corresponding pressure range with the minimum holding current when the position moves. If the minimum current gear is larger than the stored minimum current gear, the larger minimum current gear will be written into the storage unit. Each time the system is initialized, it will read the minimum current gear of the corresponding pressure range into RAM for use.

10. The energy-saving control system for maintaining a fixed position of an electronic expansion valve according to claim 6, characterized in that: The MCU specifically performs the following processing: The position signal transmitted by the position detection module is periodically detected. If a change in the position signal is detected, the current position data and pressure data are read and the holding current is immediately set to the maximum holding current, and holding processing is performed to stabilize the valve needle. Finally, the position correction is performed based on the calculated moving position.

11. An energy-saving control device for maintaining a fixed position of an electronic expansion valve, characterized in that: The device comprises: a processor configured to execute computer executable instructions; A memory stores one or more computer executable instructions, and when the computer executable instructions are executed by the processor, the steps of the energy-saving control method for maintaining a fixed position of an electronic expansion valve according to any one of claims 1 to 5 are implemented.

12. An energy-saving control processor for maintaining a fixed position of an electronic expansion valve, characterized in that: The processor is configured to execute computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the energy-saving control method for maintaining a fixed position of an electronic expansion valve according to any one of claims 1 to 5 are implemented.

13. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and the computer program can be executed by a processor to implement the steps of the energy-saving control method for maintaining a fixed position of an electronic expansion valve as described in any one of claims 1 to 5.

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