JP5411209B2 - Electronic expansion valve controller - Google Patents

Description

  The present invention relates to a control device for an electronic expansion valve in a refrigeration device, and more particularly to a control device for an electronic expansion valve that controls the opening degree of the electronic expansion valve in order to adjust the degree of superheat of the refrigeration device.

  Conventionally, as this type of control device, for example, there are those disclosed in Japanese Patent Application Laid-Open No. 2009-156502 (Patent Document 1) and Japanese Patent Publication No. 8-33244 (Patent Document 2).

  The technique of Patent Document 1 is a technique in which the constant of the target value filter is changed so that the degree of superheat quickly converges to the set value regardless of whether the measured superheat level increases or decreases. This makes it easy to adjust the degree of superheat when the device is installed. Moreover, the technique of patent document 2 is a technique which can monitor the change of measurement superheat degree, can correct | amend the setting of superheat degree, and can always drive | operate with an optimal setting value.

JP 2009-156502 A Japanese Patent Publication No. 8-33244

  In Patent Document 1, an adjusted superheat degree setting value can obtain an optimum superheat degree setting under the condition at the time of adjustment, but it can be said that the set value is an optimum value under any conditions. Absent. Therefore, if the superheat setting value cannot be adjusted more frequently, the superheat setting value should be increased so that the liquid back operation will not continue even if the seasonal conditions or load conditions change. The problem remains in that it is not always possible to operate at the optimum degree of superheat. In other words, in order to always operate at the optimum degree of superheat, the user needs to change the superheat degree setting value every time the condition changes, and there remains a problem in terms of annoyance.

  Further, in the technique of Patent Document 2, since a change in vibrational superheat is input to the controller as a control signal until it is determined that the superheat setting value is low and corrected to a high value, an electronic signal is generated accordingly. The expansion valve also vibrates, and there remains a problem in terms of the reliability of the electronic expansion valve.

  The present invention realizes the operation with the optimum superheat degree even under various conditions such as refrigeration equipment, load, evaporator pressure, condenser pressure, etc., and does not shorten the mechanical life of the electronic expansion valve. It is an object of the present invention to provide a highly reliable electronic expansion valve control device.

The control device for an electronic expansion valve according to claim 1 is a control device for an electronic expansion valve that controls the degree of superheat of the refrigeration apparatus by giving an operation amount signal to the electronic expansion valve of the refrigeration apparatus, and the superheat degree setting that is input PID control means for outputting an operation amount signal for the electronic expansion valve according to the value and the measured superheat degree of the refrigeration apparatus, a superheat degree set value and a feedback value of the operation amount signal output by the PID control means are input. Te, the correct superheat setting value to be output to the PID controller, characterized in that the corrected correction superheated Do設 value with a set value correcting means for outputting to said PID control means.

  The control device for an electronic expansion valve according to claim 2 is the control device according to claim 1, wherein the set value correction means is configured to change a valve opening degree of the electronic expansion valve from a feedback value of the operation amount signal. Monitoring is performed constantly, and the valve opening change amount and the valve opening change width in the past second period (for example, 10 minutes) are calculated every first period (for example, 1 minute). When the valve opening change amount at is less than a first predetermined pulse (for example, 25 pulses) and the valve opening change width in the past second period is less than the first predetermined pulse width (for example, 5 pulses) When it is determined that the current superheat setting value is high and the superheat setting value is corrected to be low, the amount of change in the valve opening in the past second period is equal to or greater than a second predetermined pulse (for example, 87 pulses). Is determined that the current superheat setting value is low and the superheat setting value is set to The first predetermined pulse and the first predetermined pulse width are values obtained based on experiments, respectively, depending on the structure of the electronic expansion valve and the length of the second period. Although it is different, it is the upper limit value obtained when operating during the second period in a state where it can be determined that the superheat control is stable, and the second predetermined pulse is calculated from the life of the electronic expansion valve If the change amount of the valve opening during the second period is within the second predetermined pulse, the operation of the refrigeration apparatus is continued in the same operation state, and the specified life of the electronic expansion valve (for example, 10 years) ), The value calculated so as not to exceed the number of endurance operations of the electronic expansion valve and the fact that the degree of superheat obtained based on the experiment is low and unstable (liquid back) Compared to a value that can be reliably determined) Characterized in that it is a value of the most side.

  The electronic expansion valve control device according to a third aspect is the electronic expansion valve control device according to the second aspect, wherein the set value correction means has a third period (for example, a second period) longer than the first period. Every 10 minutes), the amount of change in the valve opening during the past third period is stored as “the value of the amount of change in the valve opening during the third period for every third period”. As the previous value of the value of the valve opening change amount during the third cycle during the third cycle ", the valve opening change amount during the past third cycle is set to a third predetermined value for each first cycle. More than 3 times the value of the amount of change in the valve opening during the third period for every third period or more than the pulse (for example, 21 pulses), or the valve opening during the past third period When the degree of change is greater than or equal to the third predetermined pulse (for example, 21 pulses), it increases to more than four times the “previous value of the valve opening change amount during the third period for each third period”. In this case, it is determined that the current superheat degree set value is low and the superheat degree set value is corrected to be higher, and the value of the third predetermined pulse is a value obtained based on an experiment. Even in a system with a slow change in the degree of temperature, the degree of superheat is low and unstable (the liquid back is approaching). For example, “the value of the valve opening change amount during the third cycle for each third cycle” is 1 pulse, and the valve opening change amount during the past third cycle for each first cycle is 3 pulses. In other cases, “the previous value of the value of the valve opening change amount during the third cycle during the third cycle” is one pulse, and the valve opening change amount during the past third cycle of the first cycle is 4 If the amount of change in the valve opening is extremely small, as in the case of a pulse, it is determined that the control is normally stable. The place to be possible to prevent the accidental superheat will be determined to be unstable low (liquid back is approaching). In addition, the magnifications of 3 times and 4 times are values obtained based on experiments. Even in a system in which the change in superheat degree is slow, the superheat degree is low and unstable (the liquid back is approaching). It is a magnification that can be determined.

  A control device for an electronic expansion valve according to a fourth aspect is the control device according to the second or third aspect, wherein the first operation is performed after the refrigeration apparatus starts operation and the control apparatus finishes the startup process. The valve opening change width for the past second period calculated for each period falls within a second predetermined pulse width (for example, 25 pulses), or the refrigeration apparatus starts operation and the control apparatus ends the start-up process. The correction of the superheat degree set value is started from the time when either of the elapsed time from 30 minutes or more is established.

According to the control device for an electronic expansion valve of claim 1, the control device for the electronic expansion valve controls the degree of superheat of the refrigeration apparatus by giving an operation amount signal to the electronic expansion valve of the refrigeration apparatus. PID control means for outputting an operation amount signal for the electronic expansion valve according to the degree of set value and the measured superheat degree of the refrigeration apparatus, and a feedback value of the operation amount signal output from the superheat degree set value and the PID control means. type, by correcting the superheat setting value to be output to the PID controller, since the corrected correction overheating Do設 value and a, a setting value correcting means for outputting to said PID control means, the manipulated variable It is possible to determine whether the superheat setting value is high or low based on the feedback value of the signal, and to correct it to an optimal value.It is possible to operate at the optimal superheat setting value according to the system state of the refrigeration system. That.

  The control device for an electronic expansion valve according to claim 2 determines whether or not the current superheat degree set value is high or low based on the valve opening change amount and change width of the electronic expansion valve, and corrects the superheat degree set value to be low. The amount of change in the opening degree of the electronic expansion valve is determined so as not to exceed the mechanical life of the electronic expansion valve, so the superheat setting value is increased before the electronic expansion valve operates beyond the design life. In addition to the effect of the first aspect, the reliability is remarkably improved because the change in superheat degree and the change in the opening degree of the electronic expansion valve are stabilized.

According to the control device of the electronic expansion valve according to claim 3, in addition to the effects of 請 Motomeko 2, such as when larger systems, the superheat setpoint is low, superheat changes have unstable However, since the change in superheat degree is slow, the change in superheat degree also occurs when the amount of change in the opening of the electronic expansion valve in the second period does not reach the second predetermined pulse (for example, 87 pulses). Since it is determined that the value is unstable and the superheat degree set value can be corrected to be higher, it is possible to operate with the optimum superheat degree set value.

  According to the control device for the electronic expansion valve of the fourth aspect, it is possible to prevent the correction of the superheat setting value in the initial operation state where the refrigerant circulation is not stable, and the refrigerant circulation is stabilized. Thus, the correction of the superheat degree setting value according to the configuration of claims 1 to 3 is started from a state where it becomes effective, so that the effect of claims 1 to 3 can be obtained efficiently.

It is a principal part functional block diagram of 1st Embodiment of the control apparatus of the electronic expansion valve of this invention. It is a principal part functional block diagram of 2nd Embodiment of the control apparatus of the electronic expansion valve of this invention. It is a principal part functional block diagram of 3rd Embodiment of the control apparatus of the electronic expansion valve of this invention. It is a figure which shows the 1st system example and 2nd system example of the freezing apparatus using the control apparatus of each embodiment of this invention. It is a flowchart of the superheat degree setting addition process at the time of starting in an embodiment. It is a flowchart of the cancellation | release determination process of correction | amendment operation prohibition in embodiment. It is a flowchart of the correction process of the superheat degree setting value in embodiment. It is a flowchart of the correction determination subroutine in the embodiment. It is a figure which shows notionally the data processing in embodiment. It is a figure which shows an example of the state of the system according to the superheat degree setting addition process at the time of starting in embodiment. It is a figure which shows an example of the state of the system according to the cancellation | release determination process of correction | amendment operation prohibition in embodiment. It is a figure which shows an example of the state of the system according to the correction process of the superheat degree setting value in embodiment.

  Next, an embodiment of a control device for an electronic expansion valve of the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram of a main part of a first embodiment of a control device for an electronic expansion valve of the present invention, FIG. 2 is a functional block diagram of a main part of a second embodiment of the control device for an electronic expansion valve of the present invention, and FIG. These are the principal function block diagrams of 3rd Embodiment of the control apparatus of the electronic expansion valve of this invention, and the location enclosed with the broken line in FIGS. 1-3 is a structure peculiar to this invention. FIG. 4 is a diagram showing a first system example (FIG. 4A) and a second system example (FIG. 4B) of a refrigeration apparatus using the control device of each embodiment.

  In FIG. 4, 10 is a compressor, 20 is a condenser, 30 is an electronic expansion valve, and 40 is an evaporator. These are connected in a ring to form a refrigeration cycle. A well-known cycle for decompression (expansion) and evaporation is formed. Reference numeral 50 denotes a valve drive unit such as a pulse motor that adjusts the valve opening degree of the electronic expansion valve 30 in accordance with an input signal. Reference numeral 100 denotes a controller, and the control device for the electronic expansion valve of each embodiment is mounted on the controller 100. The controller 100 obtains an operation amount signal according to the PID operation with respect to the deviation signal calculated by comparing the superheat degree of the refrigeration cycle with the superheat degree set value set inside, and outputs the operation amount signal to the valve drive unit 50. The valve opening degree of the electronic expansion valve 30 is controlled. That is, the operation amount signal corresponds to the number of drive pulses of the pulse motor applied to the valve drive unit 50. The differences between the first system example and the second system example are as follows.

  4A includes a temperature sensor 60 for detecting the temperature of the outlet side piping of the evaporator 40 and a pressure sensor 70 for detecting the evaporation pressure on the outlet side of the evaporator 40. 100 calculates the evaporation temperature from the input signal from the pressure sensor 70, and calculates the superheat degree by the temperature / pressure equation by taking the difference between the input signal from the temperature sensor 60 of the outlet side pipe and the calculated evaporation temperature. To do. 4B includes a temperature sensor 60 that detects the temperature of the outlet-side piping of the evaporator 40, and a temperature sensor 80 that detects the temperature of the inlet-side piping of the evaporator 40. The controller 100 calculates the degree of superheat by the temperature / temperature equation by taking the difference between the temperature of the outlet side piping of the evaporator 40 and the temperature of the inlet side piping of the evaporator 40 based on the respective input signals from the temperature sensors 60 and 80. To do. The calculated degree of superheat is referred to as “measured superheat degree”. By the way, the meaning of “difference between“ X ”and“ Y ”” described herein means “X” − “Y” ”.

  In the first embodiment of FIG. 1, 1 is a set value correcting means, 2 is a PID control means, 3 is a control object, and 4 is a measuring unit. The controller 100 includes a computer having a CPU and a memory. When the computer of the controller 100 executes a predetermined control program, the functions of the set value correction unit 1, the PID control unit 2, and the measurement unit 4 are obtained. It is done. The PID control means 2 includes a PID calculation unit 21, a target value change unit 22 having a target value filter, and a target value change control unit 23 that controls the target value change unit 22. For example, a superheat degree set value SV set by the user is input to the set value correction means 1, and the set value correction means 1 uses the corrected superheat degree set value SV ′ obtained by correcting the superheat degree set value SV as a target value changing unit 22. Output to the target value change control unit 23. The controlled object 3 is the refrigeration cycle of the first system example or the second system example including the electronic expansion valve 30, and the measuring unit 4 calculates the evaporation temperature and the degree of superheat in the refrigeration cycle and measures the calculated degree of superheat. The superheat degree PV is output to the PID calculation unit 21.

  The target value changing unit 22 changes the input correction superheat degree set value SV ′ by the transfer function of the target value filter, and outputs the changed set value of the superheat degree to the PID calculating unit 21 as a target value. The mode of change of the target value can be controlled. The corrected superheat degree set value SV ′ is also input to the target value change control unit 23, and the target value change control unit 23 changes the direction of the corrected superheat degree set value SV ′, that is, the corrected superheat degree set value SV ′. Whether the value has increased or decreased is detected, and the mode of change of the target value output from the target value changing unit 22 is controlled according to the direction of the change.

  The PID calculation unit 21 performs PID calculation according to the deviation E between the superheat degree set value (target value) output from the target value change unit 22 and the measured superheat degree PV, and outputs the operation amount signal MV to the control target 3. Supply. As described above, in the embodiment, the target value filter is provided, PID control with two degrees of freedom is performed, and the target value change control unit 23 causes the target value change unit 22 to increase when the corrected superheat degree set value SV ′ increases. If the value is appropriate for the control target under the current conditions, control is performed so that the change in the target value when it falls is more gradual than the change in the target value. The measured superheat PV can be quickly converged both when SV ′ rises and falls.

  In Patent Documents 1 and 2 and a general refrigeration apparatus in which the control device for an electronic expansion valve of the present invention is used, the change in superheat degree is more stable when the superheat degree set value is increased. Conversely, when the superheat setting value is low, the change in superheat becomes unstable for the following reason. When the superheat setting value is an appropriate value or more, the refrigerant in the pipe finishes evaporating in the evaporator and becomes completely gas at the position where the temperature sensor for detecting the outlet pipe temperature is installed. Furthermore, it has passed in the state of superheated superheated steam. The part where the refrigerant evaporates absorbs the surrounding heat much more than the part where the refrigerant evaporates and is completely gasified and overheated. The piping is cooler. As a result, the low pressure side piping of the refrigeration apparatus has a portion where the temperature changes suddenly before and after that, that is, a portion where the evaporation change ends and turns into a superheated change. When the superheat setting value is an appropriate value or more, the portion where the evaporation change ends is located sufficiently upstream from the mounting position of the temperature sensor that detects the outlet piping temperature. By the superheat degree control, the outlet pipe temperature input to the controller remains stable even if it moves slightly back and forth, and the measured superheat degree is also stable. However, if the superheat setting value is lower than the appropriate value, the portion where the above-mentioned evaporation change ends approaches the mounting position of the temperature sensor that detects the outlet pipe temperature, and the position moves slightly back and forth due to superheat control. Then, a sudden temperature change is caused also in the outlet pipe temperature input to the controller, and the change in the measurement superheat degree becomes large. When the superheat degree is controlled in accordance with the change, the change in the measurement superheat degree becomes oscillating. The correction process of the superheat degree setting value of the present invention corrects the superheat degree setting value lower when the superheat degree change is stable, and conversely, when the superheat degree change is unstable, Since the set value is corrected to be higher, as a result, the refrigerant finishes evaporating at a position slightly upstream of the position where the temperature sensor for detecting the outlet pipe temperature is attached. Since the temperature sensor for detecting the outlet pipe temperature is attached to the outlet of the evaporator, the evaporation is almost completed using the entire evaporator, and efficient heat exchange can be performed.

  Here, in the control device for the electronic expansion valve as in the present invention, if the measured superheat is higher than the superheat setting value, the valve opening is controlled to be larger, and conversely, the measured superheat is higher than the superheat set value. When the value is too low, the valve opening is controlled to be small so that the measured superheat degree of the refrigeration cycle becomes equal to the superheat degree set value. Therefore, the change in the degree of superheat of the refrigeration cycle also appears in the change in the opening degree of the electronic expansion valve 30 (change in the operation amount signal MV). Therefore, the set value correction means 1 is fed back with the output of the operation amount signal MV output from the PID control means 2 (PID calculating unit 21), and the set value correction means 1 monitors the operation amount signal MV and overheats. The degree setting value SV is corrected, and a corrected superheat degree setting value SV ′ is output. In the case of Patent Document 2, the measured superheat PV is fed back to the set value correction means.

  In other words, when the set superheat degree of the refrigeration cycle is not equal to the superheat degree set value and is repeatedly vibrated repeatedly higher or lower than the superheat degree set value, the change in the valve opening is also vibrated, When the measured superheat degree of the refrigeration cycle is stable, the change in the valve opening is also stable. Therefore, even if the change in the measured superheat degree is not directly input as in Patent Document 2, as a result, the output of the manipulated variable signal MV that controls the set superheat degree is fed back and input, thereby changing the superheat degree. Can be judged whether it is stable or unstable. As described above, the determination based on the output of the operation amount signal MV makes it possible to consider the mechanical life of the operation end of the electronic expansion valve at the same time. This is because correction is performed so that the operation end does not move when the operation end moves too much.

  In the second embodiment of FIG. 2, elements denoted by the same reference numerals as in FIG. 1 are the same as those of the first embodiment, and detailed description thereof is omitted. In the second embodiment, a correction operation start determination unit 5 to which the evaporation temperature from the measurement unit 4 is fed back is provided. The correction operation start determination means 5 determines whether or not “after-start superheating degree setting process” has been completed and whether the prohibition of the correction operation has been canceled, and the setting value correction means 1 sets the superheat degree setting value. An instruction to start the correction process is output.

  In the third embodiment of FIG. 3, elements denoted by the same reference numerals as in FIG. 1 are the same as those of the first embodiment, and detailed description thereof is omitted. In the third embodiment, the PID calculation unit 21 itself is a “PID control unit”, and the set value correction unit 1 directly outputs a corrected superheat degree set value SV ′ obtained by correcting the superheat degree set value SV to the PID calculation unit 21. It is configured to

  Next, more specific control of the embodiment will be described. First, when the refrigeration apparatus is started up, the “superheating degree setting process at start-up” is performed. This is due to the following reason. For a while after the start of the operation of the refrigeration system, the evaporator 40 becomes short of refrigerant until the refrigerant reaches the refrigerant piping system, and the degree of superheat increases. If the higher superheat degree is detected and the superheat degree control is performed as it is, the opening degree of the electronic expansion valve 30 will be opened too much. Then, when the refrigerant spreads or the degree of superheat changes to a small level, the control cannot be made in time, and the liquid back seems to be slow. Thus, the stable control state is delayed. Therefore, the “superheat setting addition process” is executed as follows.

The corrected superheat degree SV ′ output from the set value correcting means 1 from the end of the start-up process of the refrigeration apparatus until either of the following conditions (1) or (2) is satisfied is a preset superheat degree. Superheat degree control is performed using not the setting (SH) value but the value of the superheat degree setting (SHS) at startup as a target value.
(1) “10 minutes have passed since the end of the startup process”
(2) “Change in the evaporation temperature (SL) after the start-up process is within 3 [K] / 5 minutes”

  The difference between the superheat degree setting (SHS) and the superheat degree setting (SH) at the time of start-up is treated as an “addition”, and the addition is set to 0 when either of the conditions (1) or (2) is satisfied. That is, the target value is apparently changed from SHS to SH.

Next, the start point of the correction operation of the superheat degree setting by the set value correction means 1 is controlled. The correction operation of the superheat degree setting is prohibited until either of the following conditions (3) or (4) is satisfied after the start process ends. When either of the conditions (3) or (4) is satisfied, it is determined as a steady state (a state where the load and the valve capacity are balanced), the prohibition of the superheat degree setting correction operation is canceled, and the correction operation is started. .
(3) “30 minutes have passed since the end of the startup process”
(4) “Valve opening change width in the past 10 minutes is within 25 pulses”

  The activation process is performed after the refrigeration apparatus starts operation and an instruction to start control is input to the controller (this input signal is referred to as “activation input” and is input to the controller through a relay contact or the like). The process performed before the controller starts PID control of the superheat degree. For example, the valve opening degree of the electronic expansion valve is changed to the valve opening position at which PID control is started (this is called the starting opening degree). Or a process of holding the activation opening for a certain time (referred to as activation time) before starting the PID control.

  The correction operation of the superheat degree setting by the set value correction means 1 is performed as follows. When the operation is performed in a state where the target value of the superheat degree is low, the liquid refrigerant moves back and forth near the attachment position of the temperature sensor 60 on the outlet pipe of the evaporator 40, and the input (detected temperature) of the temperature sensor 60 becomes unstable, and measurement is performed. The superheat value becomes unstable. Therefore, the presence or absence of this unstable state is detected, the superheat degree setting is corrected to an optimum value, and a corrected superheat degree setting value is generated.

  The correction operation of the superheat degree set value is also performed by increasing or decreasing the amount of setting addition in the same manner as the “superheat degree setting addition process at start-up”. Detection of the unstable state is determined by a change in the opening degree of the electronic expansion valve 30, that is, a change in the operation amount signal MV.

FIG. 9 is a diagram conceptually showing data processing in the set value correcting means 1. In order to correct the superheat setting value, the set value correcting means 1 is for one minute from the end of the start-up process to the valve opening change amount, maximum opening position, and minimum opening position by the operation amount signal MV. Data is totaled every minute and the past 10 minutes are held. Then, the following values (a) and (b) are calculated from these data every minute.
The amount of change in valve opening over the past 10 minutes ... (a)
Valve opening change width in the past 10 minutes ... (b)

In addition, the following values (c) and (d) are also updated every 10 minutes after the processing every minute.
Value of change in valve opening (a) in the past 10 minutes (a) every 10 minutes ... (c)
Previous value of value every 10 minutes of valve opening change amount (a) in the past 10 minutes ... (d)

  When the "superheat setting addition process at startup" is completed and the prohibition of correction operation is released, the following conditions (5) to (9) are judged every minute to increase or decrease the additional setting. Correct the superheat setting value.

(When a stable state is detected) Correction for lowering the superheat setting value is performed under the following conditions (5) and (6).
(5) Valve opening change amount (a) for the past 10 minutes is 25 pulses or less (6) Valve opening change width (b) for the past 10 minutes is 5 pulses or less Both of the above conditions (5) and (6) If it is established, the setting is reduced by 1 [K], and the superheat setting value is corrected to a lower value. Then, for 15 minutes after the low correction, even if both of the above conditions (5) and (6) are satisfied, the correction for lowering the superheat setting value is not performed. Further, when the correction is made to increase the superheat degree set value from the unstable state and the stable state is obtained, the correction for lowering the superheat degree set value is not performed for 30 minutes after the superheat degree set value is raised.

(When an unstable state is detected) Correction for increasing the superheat setting value is performed under the following conditions (7), (8), and (9).
(7) The valve opening change amount (a) for the past 10 minutes is 87 pulses or more. (8) The valve opening change amount (a) for the past 10 minutes is 21 pulses or more, and 10 of the valve opening change amount for the past 10 minutes. More than 3 times the value (c) per minute (9) The previous value (10) of the valve opening change amount (a) in the past 10 minutes is 21 pulses or more and the valve opening change amount in the past 10 minutes is 10 minutes. If any one of the above conditions (7), (8), and (9) is satisfied at least four times d), the setting value is increased by 1.0 [K] and the superheat setting value is corrected.

  When correction is performed, all data of the valve opening change amount, the maximum position, and the minimum position for the past 10 minutes, which are counted every minute, are once cleared to zero. The values of (c) and (d) are updated with the data immediately before correction even if 10 minutes have not elapsed, and the 10-minute counter is restarted.

  5 to 8 are flowcharts of the control operation of the set value correcting means 1 of the controller 100. This control operation is executed by a microcomputer built in the controller 100, and the function of the set value correcting means 1 is obtained. The processing in FIGS. 5 to 7 is executed by interrupt processing with a timing of, for example, about 1 second with respect to the main processing of the controller 100, and the processing in FIGS. 5 and 6 corresponds to the second embodiment.

  FIG. 5 is a flowchart of the superheat degree setting process at the time of startup. First, in step S1, it is determined whether the elapsed time from the start of the operation and the start-up process is 10 minutes or more. If the determination is YES, the corrected superheat degree set value is set to SHS in step S2. Is changed to SH, the addition of the superheat degree set value is terminated, and the process returns to the original routine. If the determination in step S1 is NO, it is determined in step S3 whether the change width of the evaporating temperature (SL) in the past 5 minutes is 3 [K] or less. If the determination is YES, overheating is performed in step S2. The addition of the set value is terminated and the process returns to the original routine. If the determination is NO, the process returns to the original routine as it is. By the above process, the superheat degree setting process at the time of start-up according to the conditions (1) and (2) is performed. The state of the system corresponding to the superheating degree setting process at the time of startup is as shown in FIG. 10, for example.

  FIG. 6 is a flowchart of the correction operation prohibition release determination process. First, in step S4, it is determined whether the elapsed time since the start of the operation and the start-up process is 30 minutes or more. If the determination is YES, the prohibition of the correction operation is canceled in step S5. Return to the original routine. If the determination in step S4 is NO, it is determined in step S6 whether the valve opening change width in the past 10 minutes is 25 pulses or less. If the determination is YES, the prohibition of the correction operation is canceled in step S5. Then, the process returns to the original routine. If the determination is NO, the process returns to the original routine as it is. Through the above processing, the correction cancellation prohibition determination processing according to the conditions (3) and (4) is performed. The state of the system according to this correction operation prohibition release determination process is, for example, as shown in FIG.

  FIG. 7 is a flowchart of the superheat degree setting value correction process. This process is executed when the prohibition of the correction operation is cancelled. The 1-minute timer and the 10-minute timer are started, and the process proceeds by repeating the time-up and restart of the 1-minute timer and the 10-minute timer. First, in step S11, it is determined whether 1 minute has passed. If the determination is NO, the process returns to the original routine as it is. If the determination is YES, in step S12, the valve for 1 minute is operated by the operation amount signal MV. The data of the amount of change in opening, the maximum opening position for 1 minute, and the minimum opening position for 1 minute are totaled, and the process proceeds to step S13. In step S13, the valve opening change amount (a) for the past 10 minutes and the valve opening change width (b) for the past 10 minutes are calculated from the collected data, and the process proceeds to step S14.

  In step S14, it is determined whether 10 minutes have passed. If the determination is NO, the process returns to the original routine by performing the correction determination subroutine of FIG. 8 in step S16. If the determination in step S14 is YES, in step S15, a value (c) of the valve opening change amount (a) for the past 10 minutes (c) and 10 of the valve opening change amount (a) for the past 10 minutes. The previous value (d) of the value every minute is updated. In step S16, the process of the correction determination subroutine of FIG. 8 is performed, and the process returns to the original routine.

  In the correction determination subroutine of FIG. 8, the conditions (5), (6) and (7) to (9) are determined. In step S21, the condition (7) is determined. In steps S22 and S23, the condition (8) is determined. In steps S22 and S24, the condition (9) is determined. When the condition (7) is satisfied at step S21, when the condition (8) is satisfied at steps S22 and S23, and when the condition (9) is satisfied at steps S22 and S24, respectively. Proceeding to step S25, the superheat degree set value is increased by 1 [K] and output as a corrected superheat degree set value. In step S26, mask time processing is performed and the process returns to the original routine. The mask time process in step S26 is a process for performing no correction for decreasing the setting for 30 minutes after increasing the set value when the correction is made to increase the set value and the stable state is reached. Set to minutes.

  If none of the above conditions (7) to (9) is satisfied, it is determined in step S27 whether the mask time has elapsed. If the determination is NO, the process returns to the original routine and the determination is YES. If there is, the condition (5) is determined in step S28, and the condition (6) is determined in step S29. If both conditions (5) and (6) are satisfied in steps S28 and S29, the superheat degree set value is lowered by 1 [K] in step S30 and output as a corrected superheat degree set value, and in step S31. Perform mask time processing and return to the original routine. In the mask time processing in step S31, correction for lowering the target value is not performed for 15 minutes after the setting value is corrected to be low, even if both of the above conditions (5) and (6) are satisfied. The mask time is set to 15 minutes. The state of the system according to the above correction process of the superheat degree setting value is as shown in FIG. 12, for example.

In higher than superheat setpoint condition, may not work is limited to the upper limit opening (OLP) to have a control output for moving the electronic expansion valve in the valve opening direction. If the degree of superheat is corrected in this state, since the change in the valve opening is stable at the upper limit opening, the correction for lowering the set value is continued, so if it is limited by the upper limit opening (OLP) The variable relating to correction is reset and correction processing is not performed.

  Further, there is a function called MOP (Maximum Operating Pressure) that enables prevention of liquid return at the start of the compressor and prevention of overload of the compressor motor. Similar to the upper limit opening, there are cases where the valve opening is limited by the MOP function and does not move even though the superheat degree is higher than the set value and the control output is moved to move the electronic expansion valve in the valve opening direction. . Even in this case, the correction variable is reset and the correction process is not performed.

  Furthermore, when the user changes the superheat setting SH, the variable related to correction is temporarily reset when the setting is changed so that the behavior of the electronic expansion valve due to the change of the setting value is not recognized as an unstable state. Restart the correction process. When SH is changed, if there is an additional setting, it is cleared to 0.

  There are many control devices that input an operation amount signal output for determination, but there are many purposes simply for protecting an operation end. Unlike the above, the control device of the present invention treats the manipulated variable signal output that is feedback-input as a control input signal, and actively uses it to correct the superheat setting value. That is, if the input operation amount signal output is used only for the purpose of protecting the operation end, it operates in a manner that restricts the operation amount signal output, so that the target control output cannot be output and the controllability is deteriorated. there is a possibility. On the other hand, the control device of the present invention uses the manipulated variable signal output fed back to determine whether or not the manipulated variable signal output operates within a range in which the reliability of the electronic expansion valve can be ensured, and sets the superheat degree. The degree of superheat is determined so that the manipulated variable output is within the range in which the reliability of the electronic expansion valve can be secured without degrading the controllability and the evaporator can be used effectively without degrading the controllability. Unlike the other ones, a great effect can be obtained in that the set value can be corrected to an optimum value.

DESCRIPTION OF SYMBOLS 1 Set value correction | amendment means 2 PID control means 3 Control object 4 Measurement part 5 Correction operation start determination means 10 Compressor 20 Condenser 30 Electronic expansion valve 40 Evaporator 50 Valve drive part 60 Temperature sensor 70 of evaporator outlet side piping Pressure sensor 80 Evaporator inlet side pipe temperature sensor 100 Controller

Claims (4)

A control device for an electronic expansion valve that controls the degree of superheat of the refrigeration apparatus by giving an operation amount signal to the electronic expansion valve of the refrigeration apparatus,
PID control means for outputting an operation amount signal for the electronic expansion valve in accordance with an input superheat degree set value and a measured superheat degree of the refrigeration apparatus;
Enter the feedback value of the manipulated variable signal, wherein the superheat setpoint PID control means outputs, to correct the superheat setting value to be output to the PID controller, the PID of the corrected correction overheating Do設 value A set value correcting means for outputting to the control means;
A control device for an electronic expansion valve, comprising: The set value correction means constantly monitors the valve opening change of the electronic expansion valve from the feedback value of the manipulated variable signal, and changes the valve opening change amount in the past second period for each first period, The valve opening change width is calculated, the valve opening change amount in the past second period is not more than the first predetermined pulse, and the valve opening change width in the past second period is not more than the first predetermined pulse width. If it is, it is determined that the current superheat setting value is high, and the superheat setting value is corrected to be low,
When the amount of change in the valve opening in the past second period is equal to or greater than the second predetermined pulse, it is determined that the current superheat setting value is low and the superheat setting value is corrected to be higher. The control device for an electronic expansion valve according to claim 1.   The set value correction means stores the valve opening change amount during the past third period for each third period longer than the first period, holds the previous amount, and for each first period. The amount of change in the valve opening during the past third period has increased to more than three times the “value during every third period of the amount of change in the valve opening during the third period” over the third predetermined pulse. Or, the amount of change in the valve opening during the past third period is greater than or equal to a third predetermined pulse (for example, 21 pulses), and “the value of the amount of change in the valve opening during the third period for every third period” 3. The electronic expansion according to claim 2, wherein even when the value is increased to four times or more of the “previous amount”, the current superheat setting value is determined to be low and the superheat setting value is corrected to be higher. Valve control device.   After the refrigeration apparatus starts operation and the control apparatus ends the start-up process, the valve opening change width for the past second period calculated for each first period is within the second predetermined pulse width, Alternatively, the correction of the superheat degree setting value is started when either of the elapsed time from when the refrigeration apparatus starts operation and the control apparatus finishes the start-up process becomes 30 minutes or more. The control device for an electronic expansion valve according to claim 2 or 3.

Images