JP2006220391A - Controller for cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability in time of a compressor start, to prevent overfeeding of a liquid refrigerant, and to improve cooling speed, in a controller for a cooling system controlling an opening of an electric expansion valve of a refrigeration cycle. <P>SOLUTION: Temperatures of an outlet and an inlet of an evaporator 4 of the refrigeration cycle are detected by temperature sensors 6, 7. A first superheat degree (calculation by a temperature/temperature expression) is calculated from a difference between the evaporator outlet temperature and the evaporator inlet temperature detected by the temperature sensors 6, 7 to find a first operation amount MT of the valve opening. A second superheat degree (calculation by a temperature/pressure expression) is calculated on the basis of a pressure from a pressure switch 10 and the temperature from the temperature sensor 6 to find a second operation amount MP. A total operation amount M is calculated by use of a prescribed arithmetic expression by the first operation amount MT and the second operation amount MP. The first operation amount MT is made to be effective when an in-chamber temperature is on a low temperature side, and the second operation amount MP is made to be effective when the in-chamber temperature is on a high temperature side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a cooling system in a refrigeration cycle, and more specifically, cooling that controls the opening of an electric expansion valve until the internal temperature shifts to the internal set temperature after the compressor is started. The present invention relates to a system control device.

  Conventionally, for example, Japanese Patent No. 3059534 (Patent Document 1), Japanese Patent Application Laid-Open No. 9-229495 (Patent Document 2), and Japanese Patent Publication No. 60-58384 (Patent Document 3) are related to the present invention. .

  Japanese Patent Application Laid-Open No. 2004-151867 provides a temperature sensor and a pressure sensor on the outlet side of the evaporator of the refrigeration apparatus, calculates the degree of superheat of the refrigerant, and controls the flow rate of the refrigerant by adjusting the opening of the reversible proportional expansion valve It is a technique related to the method.

  Patent Document 2 is a technique related to a control method for calculating the degree of superheat based on signals from temperature sensors attached to an outlet and an inlet of an evaporator of a refrigeration system and controlling the opening degree of an electric proportional expansion valve.

In Patent Document 3, from the right column on the first page to the left column on the second page, the temperature sensor at the evaporator inlet portion has a time delay of about 30 seconds, and the temperature sensor at the evaporator outlet portion has a time delay of about 60 seconds. It is disclosed.
Japanese Patent No. 3059534 JP-A-9-229495 Japanese Patent Publication No. 60-58384

  The prior art of Patent Document 1 uses a method of calculating the degree of superheat (second degree of superheat) by a temperature / pressure formula. In this case, since the signal detection by the pressure sensor has a very small time delay, the opening degree of the expansion valve can be adjusted quickly. However, when the internal temperature is set to a low temperature range such as −20 ° C. to −60 ° C., the accuracy (accuracy) of the pressure sensor used in this low temperature range requires a high accuracy of ± 0.1%. That is, it is impossible to use a precision specification product of about ± 1%, which is widely used, and there is a problem in terms of economy in that a very expensive pressure sensor is required.

  In the prior art of Patent Document 2, temperature sensors are provided on the inlet side and the outlet side of the evaporator, respectively, the degree of superheat (first degree of superheat) is calculated by the temperature / temperature equation, and the valve opening degree is controlled. However, as disclosed in Patent Document 3, since there is a time delay in the temperature sensor, it takes a long time to reach a suitable valve opening point, such as when a large disturbance occurs during the operation of the refrigeration cycle. It leaves room for improvement.

  It is an object of the present invention to provide a cooling system control device that solves the above-described problems, increases the reliability of the refrigeration cycle, improves the responsiveness of cooling, and makes the cooling process higher quality.

  The cooling system control device according to claim 1 calculates the degree of superheat of the refrigerant in the evaporator of the refrigeration cycle, and adjusts the opening degree of the expansion valve based on the degree of superheat. The first superheat degree is calculated based on the signal from the temperature detecting means provided on the inlet side, and the operation amount MT of the expansion valve calculated based on the first superheat degree is provided on the outlet side of the evaporator. Based on the signal from the pressure detection means and the signal from the temperature detection means provided on the outlet side, the second superheat degree is calculated, and from the operation amount MP of the expansion valve calculated based on the second superheat degree, A predetermined process according to the internal temperature SR is executed to calculate the total operation amount M, and a control step of adjusting the opening of the expansion valve is provided.

  The cooling system control device according to claim 2 is the cooling system control device according to claim 1, wherein the control step includes a second predetermined internal temperature SRL in which the internal temperature SR is set to a low temperature side. When it is less than the total amount of operation M, the total operation amount M is calculated using a third predetermined arithmetic expression that calculates the weight of the operation amount MT to be greater than or equal to the weight of the operation amount MP.

  The cooling system control device according to claim 3 is the cooling system control device according to claim 1, wherein the control step includes a first predetermined internal temperature SRH in which the internal temperature SR is set to a high temperature side. And a second predetermined calculation formula for determining and calculating the weight of the operation amount MT and the weight of the operation amount MP according to the internal temperature SR when the temperature is equal to or lower than the second predetermined internal temperature SRL set on the low temperature side. The total manipulated variable M is calculated using.

  The cooling system control device according to claim 4 is the cooling system control device according to claim 1, wherein the control step includes a first predetermined internal temperature SRH in which the internal temperature SR is set to a high temperature side. At this time, the total manipulated variable M is calculated using a first predetermined calculation formula that computes the weight of the manipulated variable MP as the weight of the manipulated variable MT.

  The cooling system control device according to claim 5 is the cooling system control device according to claim 1, wherein the control step includes a first predetermined internal temperature SRH in which the internal temperature SR is set to a high temperature side. At this time, the total manipulated variable M is calculated using a first predetermined calculation formula that calculates the weight of the manipulated variable MP as the weight of the manipulated variable MT, and the internal temperature SR is the first predetermined internal temperature SRH. And a second predetermined calculation formula for determining and calculating the weight of the operation amount MT and the weight of the operation amount MP according to the internal temperature SR when the temperature is equal to or lower than the second predetermined internal temperature SRL set on the low temperature side. The total manipulated variable M is calculated by using a third predetermined formula for calculating the weight of the manipulated variable MT as the weight of the manipulated variable MP when the interior temperature SR is lower than the second predetermined interior temperature SRL. The total operation amount M is calculated using

  According to the control device for a cooling system of claim 1, the operation amount of the expansion valve calculated from the first superheat degree by the temperature / temperature equation with high accuracy on the low temperature side (for example, less than −10 ° C.) of the internal temperature ( The first operation amount MT) and the operation amount of the expansion valve (second operation) calculated from the second degree of superheat by the temperature / pressure equation having excellent responsiveness on the high temperature side (for example, −5 ° C. or more) The total manipulated variable is calculated from the amount MP) to adjust the opening of the expansion valve. Therefore, control with excellent responsiveness is possible when the internal temperature is high, and highly accurate control is possible when the internal temperature is low.

  According to the control device for a cooling system of claim 2, when the internal temperature SR is lower than the second predetermined internal temperature SRL (for example, −10 ° C.), the first operation amount MT is calculated using the third predetermined arithmetic expression. The ratio is increased to calculate the total manipulated variable M and adjust the opening of the expansion valve. Therefore, the accuracy of the temperature corresponding to the evaporating pressure by the pressure detection means is not affected, and the opening degree of the expansion valve is adjusted by the first superheat degree of the temperature / temperature type, thereby enabling high-quality cooling control. Further, since the temperature / temperature equation ratio is slightly reduced and the second superheat degree of temperature / pressure is applied, the second manipulated variable MP due to the second superheat degree acts and responds to a large disturbance. And high-quality cooling control is possible.

  According to the cooling system control apparatus of claim 3, the internal temperature SR is less than the first predetermined internal temperature SRH (for example, -5 ° C) to the second predetermined internal temperature SRL (for example, -10 ° C) or more. At this time, the total manipulated variable M is calculated and the opening degree of the expansion valve is adjusted while gradually changing the ratio of the second manipulated variable MP and the first manipulated variable MT using the second predetermined arithmetic expression. Accordingly, two switching zones for the superheat degree are provided, and the opening degree of the expansion valve is adjusted while gradually changing the ratio between the second manipulated variable MP and the first manipulated variable MT, that is, the responsiveness is completely different. Since the control elements are not switched suddenly, it is possible to smoothly switch between control methods without causing hunting or the like, and high-quality cooling control is possible.

  According to the cooling system control apparatus of the fourth aspect, when the internal temperature SR is equal to or higher than the first predetermined internal temperature SRH (for example, −5 ° C.), the second operation amount MP is calculated using the first predetermined arithmetic expression. The ratio is increased to calculate the total manipulated variable M and adjust the opening of the expansion valve. Therefore, the ratio of the temperature / pressure type is slightly reduced and the temperature / temperature type is operated, so that the frequent opening / closing operation of the expansion valve due to small pressure fluctuations is suppressed, the service life of the expansion valve is lengthened, and the high Quality cooling control is possible.

  According to the cooling system control apparatus of the fifth aspect, when the internal temperature SR is equal to or higher than the first predetermined internal temperature SRH (for example, −5 ° C.), the second operation amount MP is calculated using the first predetermined arithmetic expression. The ratio is increased to calculate the total manipulated variable M to adjust the opening of the expansion valve, and the internal temperature SR is less than the first predetermined internal temperature SRH (for example, −5 ° C.) to the second predetermined internal temperature SRL. When the temperature is equal to or greater than (for example, −10 ° C.), the total manipulated variable M is calculated by gradually changing the ratio between the second manipulated variable MP and the first manipulated variable MT using the second predetermined arithmetic expression. When the opening degree is adjusted and the internal temperature SR is lower than the second predetermined internal temperature SRL (for example, −10 ° C.), the total operation is performed by increasing the ratio of the first operation amount MT using the third predetermined arithmetic expression. The amount M is calculated to adjust the opening of the expansion valve. Therefore, the effects of claims 2, 3 and 4 can be obtained.

  According to the control device for a cooling system of claim 1, since control with excellent responsiveness is possible when the internal temperature is high, and highly accurate control is possible when the internal temperature is low, the reliability of the refrigeration cycle As the temperature increases, the cooling process becomes higher quality.

  According to the cooling system control device of the second aspect, in addition to the effect of the first aspect, the second manipulated variable MP due to the second superheat degree acts on a large disturbance, and the responsiveness is good. High quality cooling control is possible.

  According to the control device for the cooling system of claim 3, in addition to the effect of claim 1, it is possible to smoothly switch the control method without causing hunting and the like, and high-quality cooling control is possible. .

  According to the cooling system control device of claim 4, in addition to the effect of claim 1, it further suppresses frequent opening and closing operations of the expansion valve due to fine pressure fluctuations, and the service life of the expansion valve becomes longer. High quality cooling control is possible.

  According to the cooling system control apparatus of the fifth aspect, the effects of the first, second, third and fourth aspects can be obtained.

  Next, an embodiment of a control device for a cooling system of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a basic configuration of a rapid cooling control device in a refrigeration cycle to which the cooling system control device of the embodiment is applied. This rapid cooling control apparatus uses signals from temperature sensors 6 and 7, temperature sensor 8 and pressure detection means 10 as temperature detection means mounted on the outlet side and the inlet side of the evaporator of the refrigeration cycle, respectively. Based on the A / D conversion unit 91 that performs D conversion, the temperature data of the temperature sensors 6 and 7 output from the A / D conversion unit 91, and the pressure data of the pressure detection means 10, the first superheat degree and the second superheat A superheat degree calculating means 92a-1 for calculating the degree, a valve opening degree calculating means 92a-2 for calculating a total manipulated variable of the valve opening degree from the calculated first superheat degree and the second superheat degree, A / A valve opening restriction calculating means 92a-3 for calculating an upper limit value and a lower limit value of the valve opening degree at each temperature in the storage based on the temperature data of the internal temperature sensor 8 output from the D conversion unit 91; Upper limit value of valve opening calculated by calculating means 92a-3 And a lower limit value and the valve opening calculated by the valve opening calculating means 92a-2, and the comparison result is sent to the valve drive unit 5 to drive the electric expansion valve 3. And. The pressure detection means 10 corresponds to a pressure switch and a pressure sensor described later, and the reference numeral “10” is also used for these elements.

  As will be described later, the valve opening calculation means 92a-2 calculates a first operation amount MT corresponding to the first superheat degree and a second operation amount MP corresponding to the second superheat degree, and the inside temperature sensor The total manipulated variable M is calculated based on the first to third predetermined calculation formulas (and setting coefficients) corresponding to the temperature data of 8. In addition, the valve opening restriction calculating means 92a-3 calculates the valve opening so as to lower the upper limit opening and the lower limit opening of the valve opening as the internal temperature decreases as the third priority control step. In the second priority control step, the valve opening is calculated so that the range of superheat is, for example, 5 ° C. or more and 25 ° C. or less, and in the first priority control step, the valve is controlled so as to regulate the MOP and the low pressure cut. Calculate the opening.

  Here, the MOP and the low pressure cut will be described. MOP (Maximum Operating Pressure) is originally a function of a temperature type expansion valve. As a result of the MOP regulation, it is possible to prevent liquid return at the start of the compressor and overload of the compressor motor. In general, this is a high limit function. The low pressure cut is the main function of the low pressure switch. When an abnormality occurs in the refrigeration cycle such as an expansion valve or an evaporator, and the refrigerant stops flowing, the low-pressure side pressure decreases. At that time, a low-pressure cut acts to protect the refrigeration cycle. In general, this is a low limit function.

  FIG. 2 is a diagram illustrating the refrigeration cycle and the rapid cooling control device of the embodiment. In the figure, 1 is a compressor, 2 is a condenser, 3 is an electric expansion valve, 4 is an evaporator, and these are connected in a ring to form a refrigeration cycle. A well-known cycle for decompression (expansion) and evaporation is formed. 5 is an electromagnet that adjusts the opening of the electric expansion valve 3 according to an input signal, a valve drive unit such as a pulse motor, and 6 and 7 are temperature sensors that respectively detect the temperatures of the outlet side and the inlet side of the evaporator 4. 8 is a temperature sensor for detecting the temperature in the freezer, 10 is a pressure switch for detecting the evaporation pressure on the outlet side of the evaporator 4, and 9 is connected to the pressure switch 10 and the temperature sensors 6, 7 and 8, and based on the output thereof. It is a control part which controls the valve drive part 5. FIG.

  The control unit 9 takes the difference between the evaporator outlet temperature and the refrigerant temperature, that is, the evaporator inlet temperature, based on the respective input signals from the temperature sensors 6 and 7 that detect the outlet side and inlet side temperatures of the evaporator 4, respectively. The first superheat degree (calculated by the temperature / temperature equation) is calculated, and the first manipulated variable MT according to the PID operation is obtained from the deviation signal calculated by comparing the first superheat degree and the set superheat degree. Further, the control unit 9 calculates a second degree of superheat (calculation based on a temperature / pressure equation) based on an input signal from the pressure switch 10 and a signal from the temperature sensor 6 on the outlet side. Based on the deviation signal calculated by comparing the degree of superheat and the set degree of superheat, the second manipulated variable MP according to the PI operation is obtained. Then, the first to third predetermined arithmetic expressions are selected according to the internal temperature detected by the temperature sensor 8, and the total operation amount M is calculated using the first operation amount MT, the second operation amount MP, and the selected operation expression. Then, an adjustment signal corresponding to the total operation amount M is output. That is, by applying a valve opening degree adjustment signal that gives the valve drive unit 5 the number of pulses for opening and closing the electric expansion valve 3, the opening degree of the electric expansion valve 3 is controlled and the refrigerant flow rate of the refrigeration cycle is adjusted. . Needless to say, the above-described PID operation includes a PI operation without a D element.

  FIG. 3 shows the internal configuration of the control unit 9, in which an A / D conversion unit 91 receives signals from the evaporator outlet temperature sensor 6, the inlet temperature sensor 7, the internal temperature sensor 8 and the pressure sensor 10 as A. An A / D converter 92 that performs / D conversion is a microcomputer that operates according to a predetermined program. The microcomputer 92 includes a CPU 92a, a ROM 92b that stores programs and various fixed data, and various data areas and work areas. A rewritable RAM 92c is included. The CPU 92a calculates the first superheat degree based on the signals from the temperature sensors 6 and 7, calculates the second superheat degree based on the signals from the temperature sensor 6 and the pressure sensor 10, and calculates the calculated first temperature. The valve opening is calculated from the second degree of superheat. Further, the correction value β is calculated as the difference between the first superheat degree and the second superheat degree, the set superheat degree is corrected with the correction value β, and the valve opening degree is calculated. And the valve opening degree by this calculation is sent to the valve drive part 5, and the electric expansion valve 3 is operated. Further, the CPU 92a determines the valve opening at each temperature in the chamber from various set values such as the chamber temperature stored in a predetermined area in the ROM 92b, the capacity of the electric expansion valve, the required cooling capacity, the evaporation temperature, and the condensation temperature. The upper and lower limit values are calculated. When the controller 9 operates the electric expansion valve 3 to reach the upper limit value and the lower limit value, the valve opening is limited by the upper limit value / lower limit value.

  FIG. 4 is an explanatory view showing the concept of the restriction of the opening degree by the priority control process, and the change of the upper limit value and the lower limit value of the valve opening degree obtained by calculation with respect to the internal temperature. A curve a shows a state where the upper limit opening is lowered due to a decrease in the internal temperature, and a curve b shows a state where the lower limit opening is lowered due to a decrease in the internal temperature. This is the third priority control step. Moreover, the range of the diagonal line over the curve a has shown the concept which regulates the range of superheat degree to 5 degreeC or more, and the concept which regulates MOP. This is the second priority control step and the first priority control step. Furthermore, the range of the diagonal line over the curve b has shown the concept which regulates the range of a superheat degree to 25 degrees C or less, and the concept which regulates a low voltage | pressure cut, for example. This is the second priority control step and the first priority control step. Although not directly related to the present invention, the curve c is an initial predetermined opening, and this initial predetermined opening is a value of 70% of the interval between the lower limit and the upper limit (curve a) from the lower limit (curve b). It has become. The reason why the lower limit opening is increased when the internal temperature is high is to prevent the electric expansion valve 3 from being closed too much when the refrigeration load is large.

  As explained above, when the internal temperature is high, the upper limit value of the valve opening is set to a lower opening, and the upper limit value is lowered as the internal temperature decreases, so that the valve can finally be operated at the set superheat. ing. This is because the initial superheat degree at the outlet of the evaporator at the initial stage where the rapid cooling load is large is larger than the final superheat degree at the final stage where the rapid cooling load is small. Although the operation is slightly overheated, the valve closing operation due to excessive liquid volume can be prevented, so there is no wasteful operation, and as a result, the cooling rate is increased to obtain the final cooling temperature. The time can be shortened (if the amount of liquid is excessive, the valve is repeatedly opened and closed, resulting in a slow cooling rate).

  Details of the operation outlined above will be described below with reference to a flowchart showing processing performed by the CPU 92a in accordance with a program stored in the ROM 92b. FIGS. 5 and 6 are flowcharts of the first embodiment. In the first embodiment, the CPU 92a starts operation by turning on the power, and performs initial setting in the first step S1. In this initial setting, various set values such as the internal temperature stored in the ROM 92b, the capacity of the electric expansion valve, the required cooling capacity, the evaporation temperature, the condensing temperature, the supercooling degree, and the set superheat value SH are stored in the RAM 92c. This is done by writing to a predetermined area. In step S2, it is determined whether or not there is an activation signal generated by operating an activation switch (not shown), and waits for this determination to be YES. If there is an activation signal, the valve initial opening operation is performed in step S3, and the process proceeds to step S4.

  Step S4 is a step of communication processing executed in the case of the system configuration shown in FIGS. 10 and 11 described later, and its subroutine is shown in FIG. In step S5, the signal from the pressure sensor 10 is read and A / D converted to calculate the evaporator outlet pressure PG and the evaporation pressure equivalent temperature SPG, and the process proceeds to step S6. In step S6, signals from the temperature sensors 6, 7, and 8 are read and A / D converted to obtain temperature data SG (evaporator outlet temperature), SL (evaporator inlet temperature), and SR (internal temperature). Next, in step S7, the first superheat degree SHT is calculated by the equation SHT = SG-SL. By the processing in step S7, the CPU 92a functions as superheat degree calculation means 92a-1 that calculates the first superheat degree based on signals from the temperature sensors 6 and 7 attached to the refrigerant pipes at the outlet and inlet of the evaporator 4. is doing. Next, in step S8, the second superheat degree SHP is calculated by the equation SHP = SG-SPG, and the process proceeds to step S9.

In step S9, it is determined “whether or not the operation is in a steady state”. Here, it is assumed that the cooling system is activated in step S2 and the transition from the transient state operation to the steady state operation takes about several minutes. If the determination in step S9 is NO (transient state operation), step S10 is performed. In step S12, the correction value β is set as a default value β ₀ (for example, 5 ° C.) previously stored in the storage means, and the process proceeds to step S12. If the determination is Yes (steady state operation), the correction value β is calculated by subtracting the first superheat degree SHT and the second superheat degree SHP in step S11, and the process proceeds to step S12. This correction value β is an offset value β of the set superheat degree. In step S12, a correction value (offset value) β storage process is executed. In FIG. 9C, which will be described later, the correction value β is a constant value with respect to the internal temperature SR, but the correction value β may change depending on the cooling system. In this case, for example, if the internal temperature SR is divided every 10 ° C., and the representative value βi of the correction value β in the classification 1 is stored in the storage means, it is suitable for the change in the internal temperature SR. Since a correct correction value βi is obtained, higher quality control can be performed.

  In step S13, it is determined whether or not the difference between the current internal temperature SR and the set internal temperature SRS is 20 ° C. or more. When the determination is NO (when the refrigeration load is small), the process proceeds to step S14, and the determination is YES. (When the refrigeration load is large), the process proceeds to step S16. In step S14, the first superheat degree deviation ΔSHT, which is the difference between the first superheat degree SHT and the set superheat degree SH, is added to the correction value β and is calculated by the equation ΔSHT = SHT− (SH + β). Thus, the second superheat degree deviation ΔSHP, which is the difference between the second superheat degree SHP and the set superheat degree SH, is calculated by the equation ΔSHP = SHP−SH, and the process proceeds to step S19 in FIG. In step S16, the set superheat degree SH is corrected based on the internal temperature SR to obtain a variable set superheat degree SH ', and the process proceeds to step S17. In step S17, the first superheat degree deviation ΔSHT, which is the difference between the first superheat degree SHT and the variable set superheat degree SH ′, is added to the correction value β and is calculated by the equation ΔSHT = SHT− (SH ′ + β). In step S18, the second superheat degree deviation ΔSHP, which is the difference between the second superheat degree SHP and the variable set superheat degree SH ′, is calculated by the equation ΔSHP = SHP−SH ′, and the process proceeds to step S19 in FIG. .

  Next, the first manipulated variable MT of the electric expansion valve 3 that satisfies “0 ← ΔSHT” in step S19 of FIG. 6 is calculated and stored in the RAM 92c, and “0 ← ΔSHP” is satisfied in step S20. The second manipulated variable MP of the expansion valve 3 is calculated and stored in the RAM 92c, and the process proceeds to step S21. Next, in step S21, it is determined whether the internal temperature SR is −5 ° C. or higher. In step S23, it is determined whether the internal temperature SR is −10 ° C. or higher. If the internal temperature SR is −5 ° C. or higher, the total manipulated variable M is calculated by M = MP × 0.8 + MT × 0.2 (first predetermined arithmetic expression) in step S22, and the process proceeds to step S27. When the internal temperature SR is less than −5 ° C. to −10 ° C. or more, the coefficient is calculated by CP = [0.6 × SR + 7] / 5 and CT = [− 0.6 × SR−2] / 5 in step S24. In step S25, the total operation amount M is calculated by M = MP × CP + MT × CT (second predetermined calculation formula), and the process proceeds to step S27. If the internal temperature SR is less than −10 ° C., the total manipulated variable M is calculated by M = MP × 0.2 + MT × 0.8 (third predetermined arithmetic expression) in step S26, and the process proceeds to step S27. That is, in the processing in steps S21 to S26, when the internal temperature SR is −5 ° C. or higher, the ratio of the second superheat degree is controlled to 80% and the ratio of the first superheat degree is set to 20%. When the temperature is lower than -10 ° C or higher, the switching control is gradually performed with two superheat degrees, and when the temperature is lower than -10 ° C, the ratio of the first superheat degree is 80% and the ratio of the second superheat degree is 20%. It is.

  Step S27 is a third priority control process for restricting the upper limit value / lower limit value of the valve opening, and the restriction of S27 has priority over the total manipulated variable M calculated in Step S22, S25, or S26. . Therefore, the valve opening / closing operation is not always performed when the total operation amount M is 100%. Step S28 is a second priority control process for restricting the range of the first superheat degree, and restricts the amount of refrigerant so as not to be liquid back or too small to prevent overheating. That is, even after the restriction of the third priority control process of step S27, the restriction of step S28 has priority. Therefore, also in this case, the valve opening / closing operation is not always performed when the total operation amount M is 100%. Step S29 is the first priority control process, and the operation amount is calculated such that the evaporator outlet pressure PG is equal to or lower than the MOP set value, and the evaporator outlet pressure PG is equal to or higher than the low pressure cut set value. Processing of MOP regulation and low pressure cut regulation is performed. Therefore, also in this case, the valve opening / closing operation is not always performed when the total operation amount M is 100%. In step S30, the valve opening / closing operation is executed according to the results of the processes in steps S21 to S29, and the process returns to step S4 in FIG.

  FIG. 7 is a flowchart of the second embodiment. Steps S31 to S36 of the second embodiment are processes that replace steps S21 to S26 of the first embodiment. That is, when the processing in step S20 is completed, it is determined in step S31 whether the internal temperature SR is -5 ° C or higher, and in step S33, it is determined whether the internal temperature SR is -10 ° C or higher. If the internal temperature SR is −5 ° C. or higher, the total manipulated variable M is set as the second manipulated variable MP corresponding to the second superheat degree in step S32, and the process proceeds to step S27. When the internal temperature SR is less than −5 ° C. to −10 ° C. or more, the coefficient is calculated by CT = [− SR−5] / 5 and CP = [SR + 10] / 5 in step S34, and M = in step S35. The total manipulated variable M is calculated by MP × CP + MT × CT and the process proceeds to step S27. When the internal temperature SR is less than −10 ° C., the total operation amount M is set as the first operation amount MT corresponding to the first superheat degree in step S36, and the process proceeds to step S27. That is, the processes in steps S31 to S36 are controlled by the second superheat degree when the internal temperature SR is −5 ° C. or higher, and gradually switched between two superheat degrees when the temperature is less than −5 ° C. to −10 ° C or higher. This is an example of controlling by less than −10 ° C. using the first superheat degree.

  FIG. 8 is a diagram for explaining the ratio between the first manipulated variable MT and the second manipulated variable MP for calculating the total manipulated variable M. FIG. 8 (a) is a general formula, and FIG. 8 (b) is a diagram of the first embodiment. FIG. 8C shows the formula of the second embodiment. a1, a2 are the maximum ratios of the second operation amount MP and the first operation amount MT, b1, b2 are the minimum ratios of the first operation amount MT and the second operation amount MP, respectively, and the first predetermined internal temperature A total manipulated variable M mixed according to each ratio is calculated between the SRH and the second predetermined internal temperature SRL according to the internal temperature SR.

  FIG. 9 is an explanatory view of the temperature change and superheat degree change corresponding to the control of the first embodiment. As shown in FIG. 9 (a), the internal temperature is −5 ° C. or higher. At this time, the opening degree of the electric expansion valve is adjusted based on the second superheat degree SHP. When the internal temperature is less than −5 ° C., the opening degree of the electric expansion valve is adjusted based on the first superheat degree SHT. When the internal temperature is −5 ° C. or higher, the electric expansion is performed so that the second superheat degree SHP becomes the variable set superheat degree SH ′ as shown in the state of the second superheat degree SHP in FIG. Valve opening control is performed. When the internal temperature is less than −5 ° C., as shown in the state of the first superheat degree SHT in FIG. 9C, for example, when the internal temperature is −60 ° C., the internal temperature is −5 When the temperature is lower than ℃ to -40 ℃ or higher, the opening degree of the electric expansion valve is adjusted so that the first superheat degree SHT becomes a value (SH '+ β) obtained by adding the superheat degree deviation β to the variable set superheat degree SH'. Is done. In the above description, when the internal temperature is −40 ° C. or higher, the set superheat degree SH ′ is “variable set superheat degree SH ′” whose value varies depending on the internal temperature. The curve of the second superheat degree SHP in FIG. 9B shows the case where the accuracy (accuracy) of the pressure detecting means is on the negative side. Needless to say, when the accuracy (accuracy) is ± 0, the second superheat degree SHP varies with respect to the variable set superheat degree SH ′ and the (fixed) set superheat degree SH.

As another embodiment similar to the first example, the following processing may be performed. Three temperature divisions are provided, and the division is increased and decreased by a predetermined rate by 20% every 1.66 ° C.
When the internal temperature is −5 ° C. or higher, M = MP × 1.0 + MT × 0.0,
When less than −5 ° C. to −6.66 ° C. or more, M = MP × 0.8 + MT × 0.2,
When less than −6.66 ° C. to −8.33 ° C. or more, M = MP × 0.6 + MT × 0.4,
When less than −8.33 ° C. to −10.0 ° C. or more, M = MP × 0.4 + MT × 0.6,
When less than −10.0 ° C., M = MP × 0.2 + MT × 0.8,
To calculate the operation amount M and adjust the opening of the expansion valve. At -5 ° C or higher, control is performed by the second superheat degree, and at less than -5 ° C to -10 ° C or higher, switching control is gradually performed at two superheat degrees, and at less than -10 ° C, the ratio of the first superheat degree In this example, 80% is controlled and 20% is the second superheat ratio. This is an example of acting only on the low temperature side.

Moreover, you may process as follows as other embodiment similar to 2nd Example. There are four temperature zones, and the zones are increased or decreased by 20% every 1.25 ° C.
When the internal temperature is −5 ° C. or higher, M = MP × 1.0 + MT × 0.0,
When less than −5 ° C. to −6.25 ° C. or more, M = MP × 0.8 + MT × 0.2,
When less than −6.25 ° C. to −7.5 ° C. or more, M = MP × 0.6 + MT × 0.4,
When less than −7.5 ° C. to −8.75 ° C. or more, M = MP × 0.4 + MT × 0.6,
When less than −8.75 ° C. to −10 ° C. or higher, M = MP × 0.2 + MT × 0.8,
When less than −10 ° C., M = MP × 0.0 + MT × 1.0,
To calculate the operation amount M and adjust the opening of the expansion valve. When the temperature is -5 ° C or higher, control is performed by the second superheating degree. When the temperature is lower than -5 ° C to -10 ° C or higher, the switching is gradually performed by two superheating degrees. This is an example.

  In the case of the first superheat degree based on the conventional temperature / temperature equation, the control is performed only by the third predetermined arithmetic equation, and a2 = 1 and b2 = 0. The third predetermined arithmetic expression is M = MP × 0 + MT × 1, that is, M = MT. Further, in the case of using the second superheat degree based on the conventional temperature / pressure formula, the control is performed only by the first predetermined calculation formula, and a1 = 1 and b1 = 0. The first predetermined arithmetic expression is M = MP × 1 + MT × 0, that is, M = MP.

  FIG. 10 is a block diagram showing an embodiment of the cooling system control system. In this embodiment, with respect to one compressor 1 and one condenser 2, a refrigeration cycle is constituted by four evaporators 41 to 44 and electric expansion valves 31 to 34 corresponding thereto. . The evaporators 41 to 44 are connected to the cooling system controllers 91 to 94 of the embodiments, respectively. Hereinafter, the control device for the cooling system is also referred to as a “control device” as appropriate. The control devices 91 to 94 are connected to temperature sensors 61 to 64 on the outlet side of the evaporators 41 to 44 and temperature sensors 71 to 74 on the inlet side. Further, a control device 91 as a parent device among the control devices 91 to 94 is connected to the personal computer 100, and an internal temperature sensor 8 is connected to the control device 91 of the parent device. A high pressure switch 11 is connected between the compressor 1 and the condenser 2, and a pressure switch 10 is connected to the outlet sides of the evaporators 41 to 44, and the pressure switch 10 and the control devices 91 to 94 are connected. Are connected by a communication cable 200 via a communication terminal. A terminal resistor R is connected to the communication device of the control device 91 of the master unit and the pressure switch 10. As indicated by broken lines in the figure, the outlet side and inlet side temperature sensors 61 to 64 and 71 to 74 of the evaporators 41 to 44 may be connected only to the control device 91 of the master unit. The electric expansion valve drive units 51 to 54 are valve drive units that open and close the electric expansion valves 31 to 34 in response to signals from the control devices 91 to 94 to control the valve opening. In a broad sense, it is included in the electric expansion valves 31 to 34. Further, in the figure, the pressure switch 10 is illustrated in two places, in the piping of the refrigeration cycle and in the connection of the communication line, but this pressure switch 10 is one installed at the same position.

  FIG. 11 is a block diagram of the pressure switch 10 as pressure detecting means. The pressure switch 10 includes a microcomputer 10a, a RAM 10b, a ROM 10c, an EEPROM 10d, a communication interface 10e, an input / output interface 10f, a pressure sensor 10g, an operation switch 10h, a relay drive circuit and output relay 10i, a digital display 10j, and a power supply circuit 10k. Yes. The microcomputer 10a controls the pressure switch 10 as a whole, inputs various setting values by the operation switch 10h, various arithmetic processes, and exchanges communication data with the control devices 91 to 94 via the communication interface 10e. Do. The digital display 10j includes four digits of 7-segment LED elements, and the 7-segment LED elements are configured by blue LEDs. Needless to say, the 7-segment LED element using the blue LED is not limited to the pressure switch but is widely used in the control device of the present invention.

  From the operation switch 10h, the MOP set value and the low pressure cut set value in the refrigeration cycle are input and set, and these set values are stored in the EEPROM 10d. Then, these set values and detected pressure data are transmitted from the pressure switch 10 to the control devices 91 to 94, and the control devices 91 to 94 send the set values and detected pressure data to the control devices 91 to 94 based on these set values and detected pressure data. The opening degree of the corresponding electric expansion valves 31 to 34 is controlled. At this time, each of the control devices 91 to 94 controls the valve opening so that the detected pressure based on the detected pressure data is MOP set value> detected pressure> low pressure cut set value.

  The detected pressure data is displayed on the digital display 10j. At this time, the low pressure data is displayed in blue. As a result, the visibility is improved and discrimination is much easier than when displaying in green, for example.

  FIG. 12 is a flowchart of control in each of the control devices 91 to 94, and is executed in step S4 of FIG. In the control devices 91 to 94, the control device 91 that is the parent device is set to “address 1”, and the control devices 92 to 94 that are child devices are set to “address 2 to 4”. In step S4, the program is started as a subroutine. In step S41, it is determined whether the address is "1" (whether it is a master unit). If YES, the process proceeds to step S46 via steps S42 and S43. If so, the process proceeds to step S46 via steps S44 and S45. In step S42, data is transmitted from the parent device to the child device, and in step S43, the parent device receives data from the child device. In step S44, the slave unit receives data from the master unit, and in step S45, data is transmitted from the slave unit to the master unit. In step S46, a data comparison and storage process is performed, the communication process is terminated, and the process returns to the original routine.

  In this way, the plurality of cooling system controllers corresponding to the plurality of evaporators and the pressure detection means are connected by the communication line to transmit / receive digital data. Then, the detected pressure data, the MOP set value, and the low pressure cut set value are sent to the communication line, and the plurality of cooling system control devices, for example, detect the detected pressure data, the MOP set value, and the low pressure cut set value via the communication line. It is received and various control like the said Example is performed, and it can control to the valve opening degree suitable for a refrigerating cycle.

  In the embodiment, the switching is simply performed by changing the ratio, but of course, a method of defining the membership function by applying fuzzy theory and calculating the total manipulated variable M may be used. In the embodiment, an example in which data is exchanged by communication using a pressure switch as a pressure detection unit has been described. Of course, for example, a 4 to 20 mA or 1 to 5 V transmission signal may be used using a pressure sensor. it can. In this case, the setting process of the setting value related to the first priority control process is performed on the control device side of the present invention, but it goes without saying that the same problem / effect can be obtained by solving the problem.

It is a figure which shows the basic composition of the rapid cooling control apparatus in the refrigerating cycle to which the control apparatus for cooling systems of embodiment by this invention is applied. It is a figure which shows the refrigerating cycle and rapid cooling control apparatus of embodiment. It is a figure which shows the internal structure of the control part in embodiment. It is explanatory drawing which shows the concept of the restriction | limiting of the opening degree by the change of the upper limit value and lower limit value of the valve opening degree in embodiment, and a priority control process. It is a part of flowchart of 1st Example in embodiment. It is another part of the flowchart of 1st Example in embodiment. It is a flowchart of the 2nd example in an embodiment. It is a figure explaining the ratio of the 1st operation amount MT and the 2nd operation amount MP which calculate the total operation amount M in embodiment. It is explanatory drawing of the internal temperature change and superheat degree change corresponding to control of 1st Example. It is a block diagram which shows one Example of the control system for cooling systems. It is a block diagram of the pressure switch in an Example. It is a flowchart of a subroutine of communication processing in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Electric expansion valve 4 Evaporator 5 Valve drive part 6 Evaporator outlet temperature sensor 7 Evaporator inlet temperature sensor 8 Chamber temperature sensor 10 Pressure switch (pressure detection means)
92a-1 Superheat calculating means (CPU)
92a-2 valve opening calculation means (CPU)
92a-3 Valve opening restriction calculation means (CPU)
92a-4 comparison means (CPU)

Claims (5)

In the control device for the cooling system that calculates the superheat degree of the refrigerant of the evaporator of the refrigeration cycle and adjusts the opening degree of the expansion valve based on the superheat degree,
The first superheat degree is calculated based on signals from the temperature detection means provided on the outlet side and the inlet side of the evaporator, and the operation amount MT of the expansion valve calculated based on the first superheat degree;
The second superheat degree is calculated based on the signal from the pressure detection means provided on the outlet side of the evaporator and the signal from the temperature detection means provided on the outlet side, and the expansion calculated based on the second superheat degree From the valve operation amount MP,
A control apparatus for a cooling system, comprising a control step of calculating a total operation amount M by executing a predetermined process according to the internal temperature SR and adjusting an opening of the expansion valve.   The control step uses a third predetermined calculation formula that calculates the weight of the operation amount MT as the weight of the operation amount MP when the internal temperature SR is lower than the second predetermined internal temperature SRL set to the low temperature side. The cooling system control device according to claim 1, wherein the total operation amount M is calculated.   When the control temperature is lower than the first predetermined internal temperature SRH set on the high temperature side and equal to or higher than the second predetermined internal temperature SRL set on the low temperature side, the weight of the operation amount MT 2. The cooling system control according to claim 1, wherein the total manipulated variable M is calculated using a second predetermined calculation formula that determines and calculates the weight of the manipulated variable MP according to the internal temperature SR. 3. apparatus.   The control step uses a first predetermined calculation formula that calculates the weight of the operation amount MP as the weight of the operation amount MT when the internal temperature SR is equal to or higher than the first predetermined internal temperature SRH set to the high temperature side. The cooling system control device according to claim 1, wherein the total operation amount M is calculated. The control step is
When the internal temperature SR is equal to or higher than the first predetermined internal temperature SRH set on the high temperature side, the total operation amount is calculated using a first predetermined arithmetic expression that calculates the weight of the operation amount MP as the weight of the operation amount MT. M is calculated,
When the internal temperature SR is lower than the first predetermined internal temperature SRH and equal to or higher than the second predetermined internal temperature SRL set on the low temperature side, the weight of the operation amount MT and the weight of the operation amount MP are determined as the internal temperature. The total manipulated variable M is calculated using a second predetermined calculation formula that is determined and calculated according to SR,
When the internal temperature SR is lower than the second predetermined internal temperature SRL, the total operation amount M is calculated using a third predetermined arithmetic expression that calculates the weight of the operation amount MT as the weight of the operation amount MP. The control device for a cooling system according to claim 1, wherein

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