JP2014190658A - Refrigerator - Google Patents

Abstract

A refrigerating apparatus is provided that can appropriately determine the opening degree of an expansion valve that controls a refrigerant superheat degree of an evaporator to a target superheat degree by PID control.
A refrigerating apparatus (R) controls the degree of refrigerant superheat of an evaporator by an expansion valve (11) connected to the inlet side of the evaporator (9), and adjusts the valve opening of the expansion valve (11) by PID control. And a terminal-side control device 13 for controlling the refrigerant superheat degree of the evaporator 9 to a predetermined target superheat degree. When the terminal-side control device 13 reduces the valve opening degree of the expansion valve 11, the proportional coefficient in the PID calculation K _P is different from the proportional coefficient K _P when the valve opening is expanded.
[Selection] Figure 1

Description

  The present invention relates to a refrigeration apparatus that controls the degree of refrigerant superheat of an evaporator by means of an expansion valve.

  Conventionally, a plurality of open showcases are installed in stores such as supermarkets and convenience stores. And the cold air which exchanged heat with the evaporator of each open showcase was blown into the display room, so that the goods were displayed while being cooled in the display room. In addition, the refrigerant in each open showcase is supplied with refrigerant from the compressor of the refrigerator constituting the refrigerant circuit of the refrigeration system together with the evaporator, and the refrigerant supply to this evaporator is connected to the inlet side The expansion valve was controlled (see, for example, Patent Document 1).

  In recent years, a so-called electric expansion valve (referred to as an electronic expansion valve in Patent Document 1) driven by a stepping motor or the like has been adopted. When controlling such an expansion valve, a predetermined target superheat degree of the evaporator is set, and the refrigerant superheat degree (the difference between the outlet refrigerant temperature and the inlet refrigerant temperature) of the evaporator is set so that the target superheat degree becomes this target superheat degree. The valve opening was adjusted.

JP 2007-255845 A

  Here, FIG.5 and FIG.6 shows the relationship between the temperature of the evaporator exit in this kind of open showcase, and the valve opening degree of an expansion valve. Each figure shows the operation of a so-called mechanical expansion valve (also called a temperature expansion valve) in which the valve opening is adjusted by a bellows that operates in accordance with the temperature at the outlet of the evaporator (refrigerant outlet temperature). Fig. 6 shows the ideal operating characteristics of a mechanical expansion valve in the case of a refrigerated open showcase in which the display chamber is cooled to the refrigeration temperature, and Fig. 6 shows the ideal operating characteristic of the mechanical expansion valve in the case of a refrigerated open showcase in which the display chamber is cooled to the refrigeration temperature It is.

  In a situation where the temperature at the outlet of the evaporator is rising, the degree of superheat of the refrigerant is increasing, so that the expansion valve is an expansion of the bellows to achieve the target superheat degree (usually about 5 deg in the case of a mechanical expansion valve). Thus, the valve opening degree is expanded so that more refrigerant flows through the evaporator. When the temperature at the outlet of the evaporator starts to decrease, the bellows contracts on the contrary, so that the valve opening is reduced.

  The characteristics of the expansion and reduction operations of the valve opening are set differently between the refrigerated type open showcase and the refrigerated type open showcase. In particular, the operation to reduce the size is as shown in FIG. The valve opening was reduced more quickly. This is to reliably prevent liquid back to the compressor, which is likely to occur with a refrigeration type with a lower evaporation temperature.

  On the other hand, when a so-called electric expansion valve is used as the expansion valve, the opening degree of the valve is determined by the PID calculation based on the deviation between the target superheat degree and the current refrigerant superheat degree by the control device. Therefore, the characteristics of expansion and contraction of the valve opening are the same in the refrigerated type open showcase and the refrigerated type open showcase, and in the refrigerated type, there is a high risk of liquid back.

  The present invention has been made to solve the conventional technical problem, and appropriately determines the opening degree of the expansion valve for controlling the refrigerant superheat degree of the evaporator to the target superheat degree by PID control. An object of the present invention is to provide a refrigeration apparatus that can perform such a process.

  In order to solve the above problems, a refrigeration apparatus according to the present invention controls the degree of refrigerant superheat of an evaporator by means of an expansion valve connected to the inlet side of the evaporator, and controls the opening degree of the expansion valve by PID control. And a control means for controlling the refrigerant superheat degree of the evaporator to a predetermined target superheat degree by adjusting the coefficient of the PID calculation when the valve opening degree of the expansion valve is reduced. The coefficient is different from the coefficient for enlargement.

  According to a second aspect of the present invention, there is provided a refrigeration apparatus comprising an evaporator superheat degree detecting means for detecting the refrigerant superheat degree of the evaporator in the above invention, wherein the control means is configured to calculate a target superheat degree and a current refrigerant superheat degree of the evaporator The valve opening degree of the expansion valve is controlled by PID calculation based on the deviation.

  In the refrigeration apparatus according to a third aspect of the present invention, in each of the above inventions, the control means makes the proportional coefficient in the PID calculation when the valve opening of the expansion valve is reduced larger than the proportional coefficient when the valve opening is expanded. It is characterized by.

  According to a fourth aspect of the present invention, there is provided the refrigeration apparatus according to the above-described invention, wherein the evaporator is provided in each of a plurality of open showcases, and has a compressor that constitutes a predetermined refrigerant circuit with the evaporators of the respective open showcases. The refrigerant is supplied to the evaporator of each open showcase, and the display room of the open showcase is cooled to a freezing temperature.

  According to a fifth aspect of the present invention, there is provided a refrigeration apparatus comprising a blown cold air temperature detecting means for detecting the blown cold air temperature to the display room in the above invention, and the control means is configured such that the blown cold air temperature to the display room is equal to the blown cold air temperature. The target superheat degree is increased as the set temperature is approached.

  In the refrigeration apparatus according to the sixth aspect of the present invention, in the above invention, the control means sets a plurality of control zones on the basis of the set temperature of the cool air temperature blown into the display room, and changes the target superheat degree in each control zone. Features.

  According to the present invention, in the refrigeration apparatus that controls the refrigerant superheat degree of the evaporator by the expansion valve connected to the inlet side of the evaporator, the valve opening degree of the expansion valve is adjusted by PID control, and the refrigerant superheat degree of the evaporator is adjusted. And a control means for controlling the degree of superheat to a predetermined target superheat degree, and this control means makes the coefficient in the PID calculation when reducing the valve opening of the expansion valve different from the coefficient when expanding the valve opening. Therefore, the valve opening degree can be appropriately determined by the PID control so that the valve opening degree control of the expansion valve has a desired characteristic.

  In this case, for example, the evaporator superheat degree detecting means for detecting the refrigerant superheat degree of the evaporator as in the invention of claim 2 is provided, and the control means sets the deviation between the target superheat degree and the current refrigerant superheat degree of the evaporator. Based on the PID calculation, the valve opening degree of the expansion valve is controlled, and the proportional coefficient in the PID calculation when the valve opening degree of the expansion valve is reduced as in the invention of claim 3 is based on the proportional coefficient when the valve opening degree is increased. If it is increased, the problem of liquid back in a refrigeration type open showcase having a low evaporation temperature in the evaporator as in the invention of claim 4 can be effectively solved.

  Further, as in the fifth aspect of the invention, there is provided blown cold air temperature detecting means for detecting the blown cold air temperature to the display room, and the control means brings the blown cold air temperature to the display room close to the set temperature of the blown cold air temperature. If the target superheat degree is increased according to the above, for example, a plurality of control zones are set on the basis of the set temperature of the blown cold air temperature as in the invention of claim 6, and the target superheat degree is changed in each control zone. The refrigerant superheat degree of the evaporator can be adjusted by the expansion valve based on the temperature of the cold air blown into the display chamber, and the effective area of the evaporator can be changed.

  As a result, the display room of the open showcase can be cooled accurately and stably.

It is a block diagram of a refrigerant circuit and control of a refrigeration apparatus provided with a plurality of open showcases of an embodiment to which the present invention is applied. It is a vertical side view of the open showcase of FIG. It is a flowchart of the valve opening degree determination of the expansion valve of the open showcase of FIG. It is a figure explaining the actual valve opening degree control of the expansion valve of the open showcase of FIG. It is a figure which shows the operating characteristic of the expansion valve for refrigeration type open showcases. It is a figure which shows the operation | movement characteristic of the expansion valve for freezing type open showcases.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A refrigeration apparatus R according to an embodiment to which the present invention is applied cools a plurality of refrigeration-type open showcases 1 installed in a store such as a supermarket, and each open showcase 1 installed in a store. And a refrigerator 2 that distributes and supplies the refrigerant to them. The refrigerator 2 according to the embodiment includes a compressor 3 capable of controlling the operating frequency, a radiator 4 connected to the discharge side of the compressor 3 to dissipate high-temperature and high-pressure gas refrigerant, and an outdoor air-cooling the radiator 4 And a blower 6.

  The refrigerant used in the refrigeration apparatus R is well known and is not specified here. However, in the case of the refrigerant that condenses in the radiator 4, the radiator 4 becomes a condenser, and the high pressure side such as carbon dioxide is supercritical. In this state, the refrigerant is not condensed by the radiator 4 but only radiates heat.

  The refrigerator 2 is installed outside the store, and a refrigerant pipe 7 connected to the outlet side of the radiator 4 and a refrigerant pipe 8 connected to the suction side of the compressor 3 face the inside of the store, and open to these. The showcase 1 is connected in parallel. That is, each open showcase 1 includes an evaporator 9 and an expansion valve 11 connected to the refrigerant inlet side of the evaporator 9 as will be described in detail later. The refrigerant inlet of the expansion valve 11 is connected to the refrigerant pipe 7. A refrigerant outlet of the evaporator 9 is connected to the refrigerant pipe 8 to constitute a known refrigerant circuit of the refrigeration apparatus R. Incidentally, the expansion valve 11 of the embodiment is an electric expansion valve driven by a stepping motor, and the valve opening degree can be controlled to a predetermined value including fully closed.

  In FIG. 1, 12 is a main controller. The main controller 12 is a master controller for centrally controlling the open showcases 1 and the refrigerators 2 installed in the store. The main controller 12 operates the operating conditions such as the set temperature of each open showcase 1. It is configured to be able to set. Each open showcase 1 and refrigerator 2 is provided with a terminal-side control device 13 and is connected to the main control device 12 via a communication line so as to be able to transmit and receive data (in FIG. 1, the most). Only shown on the left open showcase 1).

  Each of the main control device 12 and each terminal-side control device 13 is constituted by a microcomputer, and these constitute the control means in the present invention. The main control device 12 transmits the data related to the above-mentioned operating conditions together with the ID given to the terminal-side control device 13 of each open showcase 1 or refrigerator 2, and each terminal-side control device 13 transmits its own data. Along with the ID, data relating to the operating state such as the temperature and pressure of each part of each open showcase 1 and refrigerator 2 is transmitted to the main controller 12 and collected. The main control device 12 is configured to be able to confirm / analyze the collected data. Thus, the main control device 12 can centrally control each open showcase 1 and the refrigerator 2.

  The refrigerator 2 is provided with a low-pressure sensor 14 or the like as a low-pressure detector that detects the low-pressure of the refrigerant circuit, and is connected to the terminal-side control device 13 of the refrigerator 2. Then, the terminal side control device 13 of the refrigerator 2 compresses the refrigerator 2 based on the low pressure of the refrigerant circuit detected by the low pressure sensor 14 and the predetermined low pressure set value so that the low pressure becomes the low pressure set value. The operation frequency of the machine 3 and the operation of the outdoor fan 6 are controlled.

  Next, the open showcase 1 and the terminal side control device 13 provided on the open showcase 1 will be described. The open showcase 1 of the embodiment includes a heat insulating wall 16 having a substantially U-shaped cross section and side plates (not shown) attached to both sides of the heat insulating wall 16. Partition plates 17 and 18 are attached to the inside of the heat insulating wall 16 with a space between each other, an inner layer duct 19 is provided between the partition plates 17 and 18, and an outer layer duct 21 is provided between the outer partition plate 18 and the heat insulating wall 16. Has been.

  A bottom plate 22 is provided in front of the lower side of the inner partition plate 17, and the inside of the partition plate 17 and the bottom plate 22 serves as a display chamber 23. An inner layer outlet 26 and an outer layer outlet 27 to which a honeycomb material is attached are juxtaposed on the heat insulating wall 16 at the upper edge of the front opening 24 of the display chamber 23, and the inner layer outlet 26 and the outer layer outlet 27 are the inner layers. The duct 19 and the outer layer duct 21 communicate with each other. The heat insulation wall 16 at the lower edge of the opening 24 is provided with an inner layer suction port 28 and an outer layer suction port 29, and both the suction ports 28 and 29 communicate with the inner layer duct 19 and the outer layer duct 21, respectively.

  On the other hand, in the inner layer duct 19 and the outer layer duct 21 below the bottom plate 22, an inner layer blower 31 and an outer layer blower 32 are respectively attached. Further, the above-described evaporator 9 constituting the refrigerant circuit of the refrigeration apparatus R is vertically installed in the inner layer duct 19 on the back side, and a plurality of stages 33 for displaying products are installed in the display chamber 23. . Reference numeral 34 denotes a temperature indicator attached to the front surface of the heat insulating wall 16 above the opening 24.

  Next, 36 is an air temperature sensor provided in the inner layer duct 19 in front of the inner air outlet 26 as a blow air temperature detecting means. After the heat exchange with the evaporator 9, the cold air blown out from the inner air outlet 26. Is detected (blow air temperature). Reference numeral 37 denotes a display room temperature sensor as a display room temperature detecting means provided in the upper part of the display room 23, and detects the temperature of the cool air in the display room 23 (display room temperature). Reference numeral 38 denotes a suction temperature sensor as a suction cold air temperature detecting means provided in the inner layer duct 19 before the inner layer blower 31 and detects the temperature of the cold air sucked from the inner layer suction port 28 (suction cold air temperature). Reference numerals 41 and 42 denote an inlet temperature sensor and an outlet temperature sensor for detecting the refrigerant temperatures on the refrigerant inlet side and the refrigerant outlet side of the evaporator 9, respectively, and these constitute the evaporator superheat degree detecting means.

  The outputs of the blowout temperature sensor 36, the display room temperature sensor 37, the suction temperature sensor 38, the inlet temperature sensor 41, and the outlet temperature sensor 42 are connected to the terminal side control device 13 of the open showcase 1. The terminal-side control device 13 controls the valve opening of the expansion valve 11 and the operation of each of the fans 31 and 32 based on the outputs of these temperature sensors, and the temperature indicator 34 detects the temperature detected by the display room temperature sensor 37. Is displayed. In particular, the terminal-side control device 13 detects the refrigerant superheat degree of the evaporator 9 from the difference between the refrigerant outlet temperature of the evaporator 9 detected by the outlet temperature sensor 42 and the refrigerant inlet temperature of the evaporator 9 detected by the inlet temperature sensor 41. The valve opening degree of the expansion valve 11 is controlled based on the refrigerant superheat degree.

  The operation of the refrigeration apparatus R of the embodiment with the above configuration will be described. When the compressor 3 is operated, the high-temperature and high-pressure gas refrigerant compressed by the compressor 3 flows into the radiator 4 and dissipates heat (condenses when a refrigerant that condenses there is used). The refrigerant exiting the radiator 4 enters the store via the refrigerant pipe 7 and is distributed to each open showcase 1. The refrigerant reaching the expansion valve 11 of the open showcase 1 is decompressed there, and then flows into the evaporator 9 to evaporate. The evaporator 9 exhibits cooling ability by the endothermic action at this time.

  The cool air in the inner layer duct 19 that exchanges heat with the evaporator 9 is blown out from the inner layer outlet 26 at the upper edge of the opening 24 toward the opening 24 of the display chamber 23 by the inner layer blower 31 and from the inner layer suction port 28 at the lower edge of the opening 24. A cold air curtain is formed in the opening 24 by being sucked. In addition, the air air curtain which blows off from the outer layer blower outlet 27 through the outer layer duct 21 by the outer layer blower 32 and is sucked in from the outer layer suction port 29 serves to guard the inner cool air curtain.

  A part of this cool air curtain is circulated in the display chamber 23, and the products on each shelf 33 are cooled to the freezing temperature. The refrigerant exiting the evaporator 9 joins the refrigerant from the other open showcase 1 through the refrigerant pipe 8 and then repeats the circulation sucked into the compressor 3 again.

  Next, valve opening control of the expansion valve 11 of each open showcase 1 will be described. First, the terminal-side control device 13 of each open showcase 1 uses the target superheat degree transmitted from the main control device 12 to the terminal-side control device 13 and the evaporator obtained from the outlet temperature sensor 42 and the inlet temperature sensor 41. Based on the refrigerant superheat degree of 9, the valve opening degree of the expansion valve (electric expansion valve) 11 is controlled so that the refrigerant superheat degree becomes the target superheat degree. In this case, the terminal-side control device 13 controls the expansion valve 11 by practical / non-interference PID control.

That is, in the embodiment, the operation amount (valve opening change amount) ΔMVn of the expansion valve 11 is set to a deviation e between the current refrigerant superheat degree and the target superheat degree, a proportional coefficient K _P , a differential coefficient K _D , an integration time T _I , calculated by a general practical and non-interfering PID arithmetic expression represented by derivative time T _D. The terminal side control device 13 of the open showcase 1 controls the valve opening degree of the expansion valve 11 by PID calculation based on the deviation e between the current refrigerant superheat degree of the evaporator 9 and the target superheat degree, and the refrigerant of the evaporator 9 The superheat degree is controlled to the target superheat degree.

In this case, the terminal-side control unit 13 switching said proportional coefficient K _P of the time to reduce the valve opening of the expansion valve 11, and a proportional coefficient K _P of the time to enlarge the valve opening, use different from each other . FIG. 3 shows a flowchart of the terminal-side control device 13 that determines the valve opening by switching the proportional coefficient K _P.

The terminal-side control device 13 detects the current refrigerant outlet temperature (evaporator outlet temperature) of the evaporator 9 detected by the outlet temperature sensor 42 in step S1 and the refrigerant outlet temperature of the evaporator 9 a predetermined time (t seconds) before that. It is determined whether or not the difference is greater than zero. That is, it is determined whether or not the refrigerant outlet temperature of the evaporator 9 has risen within this predetermined time. Since the refrigerant superheat degree of the evaporator 9 is increasing when it is rising, the PID calculation by the terminal-side control device 13 is in the direction of expanding the valve opening of the expansion valve 11. Proceeding to S2, the PID calculation is executed with the proportionality coefficient K _P “small”.

On the contrary, when the refrigerant outlet temperature of the evaporator 9 within the predetermined time is the same or decreased in step S1, the refrigerant superheat degree of the evaporator 9 is decreasing, so the PID calculation by the terminal side control device 13 is performed. Is a direction to reduce the valve opening of the expansion valve 11, but in this case, the process proceeds to step S 3 to execute the PID calculation with the proportionality coefficient K _P “large”. In either case, the process proceeds to step S4, and the calculated valve opening is output to the expansion valve 11.

  As a result, the valve opening characteristic of the expansion valve 11 which is an electric expansion valve is generated in the refrigeration type open showcase 1 in which the valve opening is rapidly reduced as in the case of FIG. 6 and the evaporation temperature is lower. Therefore, it is possible to reliably prevent the liquid back to the compressor 3 that is easy to perform.

  Next, actual valve opening control of the expansion valve 11 in which the valve opening is determined by the PID calculation as described above will be described with reference to FIG. In the main control device 12 (which may be the terminal-side control device 13 of each open showcase 1), a set temperature of the blown cold air temperature of each open showcase 1 is set. Then, main controller 12 sets a plurality of control zones (in the embodiment, a total of four control zones 1 to 4) based on the set temperature (temperature control setting) (FIG. 4).

  In this case, the main controller 12 of the embodiment sets the switching temperature 1 higher than the set temperature of the blown cold air temperature by a predetermined value, the switching temperature 2 between the switching temperature 1 and the setting temperature, and sets the region of the switching temperature 1 or higher. The zone of control zone 1, lower than switching temperature 1 and higher than switching temperature 2 is called control zone 2, the zone lower than switching temperature 2 and higher than the set temperature is called control zone 3, and the zone below the set temperature is called control zone 4.

  When the blown cold air temperature (detected by the blown temperature sensor 36) transmitted from the terminal-side control device 13 of the open showcase 1 is in the control zone 1 farthest from the set temperature, the target superheat is set as the target superheat. 1 (for example, about 5 deg), when the control zone 2 is closer to the set temperature than the control zone 1, the target superheat degree is set to the target superheat degree 2 (for example, about 8 deg) larger than the target superheat degree 1, and further to the set temperature from the control zone 2 When the control zone 3 is close, the target superheat degree is set to a target superheat degree 3 (for example, about 15 deg) that is larger than the target superheat degree 2. That is, the target superheat degree is increased in the control zone closer to the set temperature. As a result, the target superheat degree increases as the blown cold air temperature approaches the set value. Then, the main control device 12 transmits the determined target superheat degree data (data relating to operating conditions) to the terminal-side control device 13 of the open showcase 1. When the blown cold air temperature is in the control zone 4, the main controller 12 sends data indicating that the expansion valve 11 is fully closed (valve opening zero) (data relating to operating conditions) to the terminal side of the open showcase. Transmit to the control device 13.

  The terminal-side control device 13 of the open showcase 1 that has received the above-described data related to the control of the expansion valve 11 from the main control device 12 has the refrigerant superheat degree of the evaporator 9 obtained from the outlet temperature sensor 42 and the inlet temperature sensor 41 for each target. The valve opening degree of the expansion valve 11 is controlled by the PID calculation as described above so that the degree of superheat is reached, and when an instruction to fully close is transmitted, the expansion valve 11 is fully closed (the valve opening degree is zero). To do.

  FIG. 4 also shows the transition of the blowing temperature of the open showcase 1 by the valve opening control of the expansion valve 11. Assuming so-called pull-down immediately after installing the open showcase 1 or after defrosting the evaporator 9, the current blown cold air temperature detected by the blowout temperature sensor 36 is higher than the switching temperature 1 and is in the control zone 1. Since the target superheat degree is the target superheat degree 1 (about 5 deg), the effective area of the evaporator 9 is large (the amount of refrigerant in which liquid refrigerant exists from the refrigerant inlet to the vicinity of the outlet is supplied from the expansion valve 11). . Thereby, after being circulated by the inner layer blower 31 and exchanging heat with the evaporator 9, the temperature of the cool air blown out from the inner layer outlet 26 (the blown cold air temperature) rapidly decreases.

  Thereafter, when the blown cold air temperature becomes lower than the switching temperature 1 and enters the control zone 2, the target superheat degree is expanded to the target superheat degree 2 (about 8 deg). Thereby, since the effective area of the evaporator 9 is reduced, the fall degree of blowing cold air temperature becomes slow. When the blown cold air temperature becomes lower than the switching temperature 2 and enters the control zone 3, the target superheat degree is further expanded to the target superheat degree 3 (about 15 deg). As a result, the effective area of the evaporator 9 is further reduced, so that the degree of decrease in the blown-out cold air temperature becomes more gradual, gradually approaching the set temperature, and becomes stable although it is slightly up and down (FIG. 4).

  When the blown cold air temperature falls below the set temperature and enters the control zone 4, the expansion valve 11 is fully closed as described above, so that the supply of refrigerant to the evaporator 9 is stopped, and the display chamber 3 Cooling stops (thermo OFF). Thereafter, when the temperature detected by the blowout temperature sensor 36 rises and enters the control zone 3, the expansion valve 11 is opened again and returns to a state controlled by the target superheat degree 3.

As described in detail above, in the present invention, in the refrigeration apparatus R that controls the refrigerant superheat degree of the evaporator 9 by the expansion valve 11 connected to the inlet side of the evaporator 9, the valve opening degree of the expansion valve 11 is controlled by PID control. The main control device 12 and the terminal-side control device 13 that adjust and control the refrigerant superheat degree of the evaporator 9 to a predetermined target superheat degree are provided, and when the terminal-side control device 13 reduces the valve opening degree of the expansion valve 11 Since the proportional coefficient K _P in the PID calculation is different from the proportional coefficient K _P when the valve opening is enlarged, the valve is appropriately opened by PID control so that the valve opening control of the expansion valve 11 has desired characteristics. You will be able to determine the degree.

  In the embodiment, since the proportional coefficient in the PID calculation when the valve opening of the expansion valve 11 is reduced is made larger than the proportional coefficient when the valve opening is expanded, the refrigeration type in which the evaporation temperature of the refrigerant in the evaporator 9 is low. It is possible to effectively solve the problem of liquid back to the compressor 3 in the open showcase 1.

  In addition, the target superheat degree is increased as the blown cold air temperature to the display chamber 23 approaches the set temperature of the blown cold air temperature. In the embodiment, the control zones 1 to 5 are controlled based on the set temperature of the blown cold air temperature. 4 and the target superheat degree is changed in each of the control zones 1 to 4, the refrigerant superheat degree of the evaporator 9 is adjusted by the expansion valve 11 based on the blown cold air temperature to the display chamber 23, and the evaporator The effective area of 9 can be changed. Thereby, the display chamber 23 of the open showcase 1 can be cooled accurately and stably.

  In the embodiment, the valve opening control of the expansion valve 11 has been described with the refrigeration apparatus R constructed from the main control device 12 and the terminal-side control device 13. However, the present invention is not limited to this, and the terminal-side control device 13 has its own open show. A target superheat degree of the evaporator 9 of the case 1 may be set and the valve opening degree of the expansion valve 11 may be controlled.

  In particular, in the embodiment, the proportionality coefficient when the opening degree of the expansion valve 11 is reduced is larger than that when the expansion valve 11 is enlarged. However, the present invention is not limited to this when applied to a refrigeration apparatus other than the refrigeration type open showcase 1. Different proportional coefficients may be used depending on the characteristics of the valve opening degree control of the expansion valve required in the refrigeration apparatus.

In the embodiment, the proportional coefficient K _P in the PID calculation is switched between “small” and “large”, but these values should be set as appropriate according to the use of the refrigeration apparatus. Furthermore, in the embodiment, only the proportional coefficient K _P is changed. However, the inventions of claims 1 and 2 are not limited thereto, and may be changed including the differential coefficient K _D.

R Refrigeration equipment 1 Open showcase 2 Refrigerator 3 Compressor 4 Radiator 7, 8 Refrigerant piping 9 Evaporator 11 Expansion valve 12 Main control device (control means)
13 Terminal side control device (control means)
14 Low pressure sensor 23 Display room 36 Blowing temperature sensor (Blowing cold air temperature detecting means)
41 Inlet temperature sensor (Evaporator superheat detection means)
42 Outlet temperature sensor (Evaporator superheat detection means)

Claims (6)

In the refrigeration apparatus for controlling the degree of refrigerant superheat of the evaporator by an expansion valve connected to the inlet side of the evaporator,
Control means for adjusting the opening degree of the expansion valve by PID control to control the refrigerant superheat degree of the evaporator to a predetermined target superheat degree;
The control means is characterized in that when the valve opening of the expansion valve is reduced, the coefficient in the PID calculation is different from the coefficient when the valve opening is increased. Evaporator superheat degree detection means for detecting the refrigerant superheat degree of the evaporator,
The refrigeration apparatus according to claim 1, wherein the control means controls the valve opening degree of the expansion valve by PID calculation based on a deviation between the target superheat degree and a current refrigerant superheat degree of the evaporator. .   The said control means makes the proportionality coefficient in the said PID calculation when reducing the valve opening degree of the said expansion valve larger than the proportionality coefficient when expanding the said valve opening degree. 2. The refrigeration apparatus according to 2. The evaporator is provided in each of a plurality of open showcases, and refrigerant is supplied to the evaporators of the open showcases from a refrigerator having a compressor constituting a predetermined refrigerant circuit with the evaporators of the open showcases. To supply,
The refrigeration apparatus according to claim 3, wherein the display room of the open showcase is cooled to a refrigeration temperature. A blown cold air temperature detecting means for detecting the blown cold air temperature to the display room,
The refrigeration apparatus according to claim 4, wherein the control means increases the target superheat degree as the blown cold air temperature into the display room approaches a set temperature of the blown cold air temperature.   6. The refrigeration according to claim 5, wherein the control means sets a plurality of control zones based on a set temperature of the blown cold air temperature to the display room, and changes the target superheat degree in each control zone. apparatus.

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