JP2008196812A - Refrigerant flow control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerant flow control device, preventing breakage of a compressor and steadily preventing lowering of cooling efficiency. <P>SOLUTION: This refrigerant flow control device includes: an electronic expansion valve; a first temperature sensor and a second temperature sensor, which are disposed to be different from each other in distance from an inlet part of an evaporator; a valve opening control means for reducing an opening of the electronic expansion valve when a temperature difference between the temperature of a refrigerant detected by the first temperature sensor and the temperature of a refrigerant detected by the second temperature sensor is smaller than a preset lower limit threshold, and enlarging the opening of the electronic expansion valve when the temperature difference is larger than a preset upper limit threshold; and a preset temperature difference region changing means for counting the number of times of hunting in which the temperature difference is below the lower limit threshold during a preset unit time, and changing the width of the preset temperature difference region determined by the lower limit threshold and the upper limit threshold according to the counted number of times of hunting. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, an electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening degree and a pipe line that is arranged so that the refrigerant passes through the evaporator are different from each other from the inlet portion of the evaporator. The temperature difference between the first temperature sensor and the second temperature sensor, the refrigerant temperature detected by the first temperature sensor, and the refrigerant temperature detected by the second temperature sensor is lower than a preset lower threshold. A refrigerant flow rate control device comprising: a valve opening degree adjusting means for reducing the opening degree of the electronic expansion valve if the temperature difference is smaller and increasing the opening degree of the electronic expansion valve if the temperature difference is larger than a preset upper limit threshold value. It is about.

  For example, in a showcase that displays and sells products in a cooled state, an evaporator is provided inside the container, and a compressor, a condenser, and an electronic expansion valve are provided outside the container. A refrigeration cycle is configured by supplying and circulating a refrigerant to the evaporator, the compressor, the condenser, and the electronic expansion valve, and the inside of the container is maintained at a predetermined temperature state by this refrigeration cycle.

  In this type of showcase, for example, a second refrigerant temperature sensor (second temperature sensor) is provided at the refrigerant outlet of the evaporator, and a first refrigerant temperature sensor (first temperature) is provided at the refrigerant inlet of the evaporator. Sensor).

  And in this showcase, by controlling the refrigerant | coolant amount which flows in into an evaporator with an electronic expansion valve according to the detection result of those refrigerant | coolant temperature sensors, while preventing cooling efficiency falling, the exit of an evaporator This prevents a phenomenon called so-called liquid back, in which a mixture of a liquid refrigerant and a gaseous refrigerant is discharged from the section and enters the compressor.

  Specifically, the opening degree of the electronic expansion valve is changed as described below according to a temperature difference obtained by subtracting the first temperature detected by the first refrigerant temperature sensor from the second temperature detected by the second refrigerant temperature sensor. To do.

  When the temperature difference is smaller than 1 [K] which is a preset lower limit threshold, the temperature difference is increased by reducing the opening of the electronic expansion valve, and the compressor is caused by the occurrence of liquid back. Breakage can be prevented.

  On the other hand, when the temperature difference is larger than 5 [K] which is a preset upper limit threshold, the temperature difference can be reduced by increasing the opening of the electronic expansion valve, and the cooling efficiency can be improved.

  Further, when the temperature difference is not less than the lower limit threshold and not more than the upper limit threshold, the opening degree of the electronic expansion valve is maintained (see, for example, Japanese Patent Application No. 2006-179966).

  By the way, as described above, even if the operation of the refrigeration cycle is performed by reducing or expanding the opening of the electronic expansion valve based on the detection results of the two refrigerant temperature sensors, the lower limit threshold and the upper limit The following problems occur when the width of the set temperature difference area determined by the threshold does not match the current operating environment, such as the load fluctuation according to the season and the frosting state of the evaporator. Will be.

  First, a case where the width of the set temperature difference region is narrow with respect to the current operating environment will be described. For example, in the refrigeration cycle, when the current temperature difference exceeds the upper limit threshold, the showcase determines that the current temperature difference is excessive and increases the opening of the electronic expansion valve.

  By expanding the opening of the electronic expansion valve, the temperature difference becomes smaller, and eventually the temperature difference falls within the set temperature difference region, but the width of the set temperature difference region is so narrow that it does not stay there, and the lower threshold is set. Will be lower.

  In this state, the showcase determines that the liquid is back and reduces the opening of the electronic expansion valve. By reducing the opening of the electronic expansion valve, the temperature difference increases, and eventually the temperature difference falls within the set temperature difference area. It will exceed.

  Similarly, it is repeated that the temperature difference changes from outside one set temperature difference region to the other set temperature difference region, and thereafter from outside the other set temperature difference region to one set temperature difference region.

  When the showcase is operated with a large number of times that the temperature difference is outside one set temperature difference area and outside the other set temperature difference area, the temperature difference falls below the lower limit threshold value. As a result, the compressor may be damaged, and the cooling efficiency is lowered due to the temperature difference exceeding the upper limit threshold, which is contrary to the energy saving operation.

  On the other hand, when the set temperature difference area is wide with respect to the current operating environment, the temperature difference is set less frequently because the temperature difference is outside one set temperature difference area and outside the other set temperature difference area. A large proportion of the time stays in the temperature difference region. However, even if the temperature difference remains in the set temperature difference region, if the temperature difference is maintained in a state where the difference from the upper limit threshold is small, the cooling efficiency is lowered.

  Therefore, in view of the above circumstances, the present invention is to provide a refrigerant flow rate control device that can prevent a compressor from being damaged and can prevent a steady decrease in cooling efficiency.

  In order to achieve the above object, an invention according to claim 1 includes an electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening degree, and a tube disposed so that the refrigerant passes through the evaporator. A first temperature sensor and a second temperature sensor disposed on the passage so that distances from the inlet of the evaporator are different from each other; a temperature of the refrigerant detected by the first temperature sensor; and a detection by the second temperature sensor When the temperature difference from the temperature of the refrigerant is smaller than a preset lower limit threshold, the opening of the electronic expansion valve is reduced, and when the temperature difference is larger than a preset upper limit threshold, the electronic A refrigerant flow rate control device comprising a valve opening degree adjusting means for enlarging the opening degree of the expansion valve, wherein the number of huntings in which the temperature difference falls below a lower limit threshold is counted in a preset unit time, and the counted number of huntings According to the above Characterized in that it comprises a set temperature difference region changing means for changing the width of the set temperature difference area determined by the limit threshold and the upper threshold.

  The refrigerant flow rate control device according to claim 2 of the present invention is the refrigerant flow rate control device according to claim 1, wherein the set temperature difference region changing means is configured such that the number of huntings below the lower limit threshold is equal to or less than a preset lower limit number of huntings. When the width of the set temperature difference area is narrowed and the number of huntings below the lower limit threshold is equal to or greater than the preset upper limit number of huntings, the width of the set temperature difference area is widened and the number of huntings below the lower limit threshold is When the number is greater than the set lower limit number of huntings and less than the upper limit number of huntings, the width of the set temperature difference region is maintained.

  According to a third aspect of the present invention, there is provided the refrigerant flow rate control device according to the first aspect, wherein the first temperature sensor is located at an inlet portion of the evaporator, and the second temperature sensor is the evaporator. It is located in the exit part of this.

  The refrigerant flow rate control device according to claim 4 of the present invention is the refrigerant flow control device according to claim 1, wherein the first temperature sensor is located in an intermediate portion between an inlet portion and an outlet portion of the evaporator, and The second temperature sensor is located at the outlet of the evaporator.

  The refrigerant flow rate control device according to claim 5 of the present invention is the refrigerant flow control device according to claim 1, wherein the valve opening degree adjusting means elapses a preset regulation time when the temperature difference falls below the lower limit threshold value. Up to, the expansion of the opening degree of the electronic expansion valve is restricted.

  According to the present invention, the refrigerant flow control device counts the number of huntings in which the temperature difference falls below the lower limit threshold in a preset unit time, and is determined by the lower limit threshold and the upper limit threshold according to the counted number of huntings. Since it has a setting temperature difference area changing means to change the width of the setting temperature difference area, even if the current operating environment changes such as load fluctuations according to the season and frosting state of the evaporator, the setting temperature difference area The width of can be changed. Therefore, when the set temperature difference region is wider than the current operating environment, the set temperature difference region changing means can narrow the width, so that the cooling efficiency is constantly reduced. Can be prevented. In addition, when the set temperature difference area is narrower than the current operating environment, the set temperature difference area changing means can widen the width, resulting in the occurrence of liquid back. While being able to prevent a compressor from being damaged, it can prevent that cooling efficiency falls.

  Exemplary embodiments of a refrigerant flow control device according to the present invention will be explained below in detail with reference to the accompanying drawings.

[Embodiment 1]
FIG. 1 is an explanatory diagram showing a configuration of a cooling device to which the refrigerant flow rate control device according to Embodiment 1 of the present invention is applied. The cooling device illustrated here is applied to the open showcase 11 that displays and sells the product stored in the storage 10 in a cooled state, and includes the evaporator 12 in the storage 10 of the open showcase 11. The compressor 15, the condenser 14, and the electronic expansion valve 13 are provided outside the open showcase 11.

  The evaporator 12, the compressor 15, the condenser 14, and the electronic expansion valve 13 are connected to each other by a refrigerant supply pipe 16 to constitute a refrigeration cycle in which refrigerant is circulated and supplied. That is, in this cooling device, the high-temperature and high-pressure gas refrigerant discharged from the compressor 15 is cooled in the condenser 14 to become a high-temperature and high-pressure liquid refrigerant. This high-temperature and high-pressure liquid refrigerant is adiabatically expanded by the electronic expansion valve 13 to become a low-temperature and low-pressure gas-liquid two-phase refrigerant, and is supplied to the evaporator 12 of the container 10. The low-temperature and low-pressure gas-liquid two-phase refrigerant supplied to the evaporator 12 exchanges heat with the air in the storage 10 supplied by the blower fan 17 and absorbs heat from the air to become a low-temperature and low-pressure gas refrigerant. The storage 10 is cooled. The low-temperature and low-pressure gas refrigerant discharged from the evaporator 12 is sucked into the compressor 15 and again becomes a high-temperature and high-pressure gas refrigerant and supplied to the condenser 14. In the present embodiment, when an opening degree command is given as the electronic expansion valve 13, a valve that changes the opening degree according to the opening degree command and can adjust the amount of refrigerant flowing into the evaporator 12 is applied. ing. Inside the evaporator 12, a pipe line 12a is disposed so that the refrigerant passes therethrough.

  A first refrigerant temperature sensor (first temperature sensor) 20 is installed at the inlet of the evaporator 12 in the refrigerant supply line 16 connected to the electronic expansion valve 13 and the evaporator 12. The first refrigerant temperature sensor 20 detects the temperature of the refrigerant passing through the inlet portion of the evaporator 12.

  A second refrigerant temperature sensor (second temperature sensor) 21 is installed at the outlet of the evaporator 12 in the refrigerant supply line 16 connected to the evaporator 12 and the compressor 15. The second refrigerant temperature sensor 21 detects the temperature of the refrigerant that passes through the outlet of the evaporator 12.

  As described above, in the evaporator 12 of this refrigerant flow control device, the two refrigerant temperature sensors 20, 21 are installed in a manner in which the distance from the inlet is different from the inlet to the outlet of the pipe 12a. is there. Moreover, the first refrigerant temperature sensor 20 is closer to the inlet portion of the evaporator 12 than the second refrigerant temperature sensor 21.

  The refrigerant flow control device includes a control means 19. The control unit 19 includes a storage unit 25 and a valve opening degree adjusting unit 30.

  The storage means 25 stores programs and data for operating the refrigerant flow rate control device. The storage means 25 stores a lower limit threshold and an upper limit threshold. In this embodiment, for example, 1 [K] is stored as the lower limit threshold, and 5 [K] is stored as the initial value of the upper limit threshold. Further, the storage means 25 stores a hunting lower limit number and a hunting upper limit number described later. In the first embodiment, for example, 0 is stored as the hunting lower limit number, and 3 is stored as the hunting upper limit number. The storage means 25 stores a unit time described later. In the first embodiment, for example, 5 minutes is stored as the unit time.

  The valve opening adjusting means 30 adjusts the opening of the electronic expansion valve 13 based on the detection results of the refrigerant temperature sensors 20 and 21, for example, and includes a temperature difference measuring unit 31 and a valve opening setting unit 33. Yes.

The temperature difference measuring unit 31 detects the temperature of the refrigerant detected by the first refrigerant temperature sensor 20 (hereinafter referred to as “the outlet refrigerant temperature T ₂ ”) from the temperature of the refrigerant detected by the second refrigerant temperature sensor 21 (hereinafter referred to as “exit part refrigerant temperature T ₂ ”). The temperature difference Δt1 is calculated by subtracting the “inlet refrigerant temperature T ₁ ”).

  The valve opening setting unit 33 sets the opening of the electronic expansion valve 13 based on the temperature difference Δt1 and data stored in the storage means 25.

  Such a cooling device aims at improving the cooling efficiency, and can effectively use the evaporator 12 by reducing the temperature difference Δt1 as much as possible. However, when the temperature difference Δt1 is kept small, there is a possibility that the liquid back described below occurs.

  A graph showing the temperature distribution of the refrigerant in the evaporator 12 is shown in FIG. As shown in FIG. 2, the temperature distribution of the refrigerant in the evaporator 12 has a small temperature change in the superheated steam portion and the gas-liquid two-phase portion, and the boundary portion between the superheated steam portion and the gas-liquid two-phase portion (evaporation completion point). ) Have characteristics that change rapidly. This evaporation completion point is close to the inlet portion of the evaporator 12 when the temperature difference Δt1 is large, and close to the outlet portion of the evaporator 12 when the temperature difference Δt1 is small.

  Therefore, when the temperature difference Δt1 is gradually reduced by increasing the opening of the electronic expansion valve 13, the evaporation completion point is at the outlet of the evaporator 12 as shown in FIGS. 2 (a) to 2 (c). Gradually approach. Further, as shown in FIG. 2 (d), when the temperature difference Δt1 is maintained at 0 [K], a mixture of a gaseous refrigerant and a liquid refrigerant from the outlet of the evaporator 12 is obtained. A phenomenon called so-called liquid back that is discharged and enters the compressor 15 occurs. If this phenomenon of liquid back occurs, the compressor 15 may be damaged. On the other hand, when the temperature difference Δt1 is larger than 0 [K], liquid back does not occur. However, if the state in which the temperature difference Δt1 is a large value is maintained, the cooling efficiency of the cooling device decreases.

  Therefore, in the cooling device, energy saving operation can be realized by operating in a state where the temperature difference Δt1 is as small as possible so as not to damage the compressor due to occurrence of liquid back. Therefore, in order to realize the above operation, in the cooling device according to the present invention, the opening degree adjusting process of the electronic expansion valve 13 described below is performed by the valve opening degree adjusting means 30.

  FIG. 3 is a flowchart showing the contents of the opening degree adjusting process of the electronic expansion valve 13 performed by the valve opening degree adjusting means 30 shown in FIG. Hereinafter, the operation of the refrigerant flow control device will be described with reference to FIG.

  When the cooling device is in an operating state, the valve opening degree adjusting means 30 detects the temperature of each refrigerant through the refrigerant temperature sensors 20 and 21 at regular intervals, for example (step S101), and through the temperature difference measuring unit 31. It is determined whether or not the calculated temperature difference Δt1 is greater than or equal to a preset lower limit threshold L [K] (step S102).

  When the temperature difference Δt1 is not equal to or greater than the lower limit threshold L [K], that is, when the temperature difference Δt1 is smaller than the lower limit threshold L [K] (step S102: No), the valve opening degree adjusting means 30 opens the electronic expansion valve 13. Is reduced (step S103), the procedure is returned.

  When the opening degree of the electronic expansion valve 13 is reduced, the temperature difference Δt1 increases. As a result, the temperature difference Δt1 changes so as to exceed the lower limit threshold L [K].

  On the other hand, when the temperature difference Δt1 is greater than or equal to the lower threshold L [K] (step S102: Yes), the procedure proceeds to step S104.

  Next, the valve opening degree adjusting means 30 determines whether or not the temperature difference Δt1 is equal to or less than a preset upper limit threshold value U [K] (step S104).

  When the temperature difference Δt1 is not less than or equal to the upper limit threshold value U [K], that is, when the temperature difference Δt1 is larger than the upper limit threshold value U (step S104: No), the valve opening degree adjusting means 30 increases the opening degree of the electronic expansion valve 13. (Step S105), the procedure is returned.

  When the opening degree of the electronic expansion valve 13 is increased, the temperature difference Δt1 is reduced. As a result, the temperature difference Δt1 changes so as to fall below the upper limit threshold U [K].

  On the other hand, when the temperature difference Δt1 is equal to or smaller than the upper threshold value U [K] (step S104: Yes), the procedure is returned as it is.

  FIG. 4 shows a summary of the determination performed by the valve opening adjustment means 30 and the opening adjustment processing of the electronic expansion valve 13. That is, when the temperature difference Δt1 is smaller than the lower limit threshold L [K], the valve opening degree adjusting means 30 determines that the liquid is back and reduces the opening degree of the electronic expansion valve 13, and the temperature difference Δt1 is the upper limit. When larger than the threshold value U [K], it is determined that the temperature difference Δt1 is excessive, the opening degree of the electronic expansion valve 13 is increased, and the temperature difference Δt1 is equal to or greater than the lower limit threshold value L [K]. If the upper limit threshold value U [K] or less, the temperature difference Δt1 is determined to be appropriate, and the opening degree of the electronic expansion valve 13 is maintained. Therefore, according to this refrigerant flow rate control device, the valve opening degree adjusting means 30 can prevent the temperature difference Δt1 from being maintained smaller than the lower limit threshold L [K], so that liquid back occurs. This can prevent the compressor 15 from being damaged. Moreover, since it is possible to prevent the temperature difference Δt1 from being maintained larger than the upper limit threshold value U [K], it is possible to prevent the cooling efficiency from being lowered.

  Moreover, the control means 19 of this refrigerant | coolant flow control apparatus changes the setting temperature difference area change shown in FIG. 1 which changes the width | variety of the setting temperature difference area T determined by the lower limit threshold value L [K] and the upper limit threshold value U [K]. Means 40 are provided. The set temperature difference region changing unit 40 includes a lower limit threshold lowering count measuring unit 42 and an upper limit threshold setting unit 43.

  The lower limit threshold lowering count measuring unit 42 determines the number of times that the temperature difference Δt1 falls below the lower limit threshold L [K] during the unit time (hereinafter referred to as “hunting”. Count N)).

  The upper limit threshold setting unit 43 determines whether or not the width of the set temperature difference region T is appropriate according to the hunting number N counted by the lower limit threshold lowering number measuring unit 42, and according to the counted hunting number N. The width of the set temperature difference region T is changed.

  FIG. 5 is a flowchart showing the contents of the set temperature difference region changing process performed by the set temperature difference region changing means 40 shown in FIG. Hereinafter, the operation of the refrigerant flow control device will be described with reference to FIG.

  When the cooling device is in an operating state, the set temperature difference region changing unit 40 counts the number of huntings N for 5 minutes, which is a unit time, by the lower limit threshold count measurement unit 42 every time a suitable time elapses, for example. (Step S201), it is determined whether or not the counted number of huntings N is greater than 0, which is a preset lower limit number of huntings (Step S202).

  When the number of huntings N is not greater than 0 (step S202: No), that is, when the number of huntings is 0, the set temperature difference region changing means 40 determines that the width of the set temperature difference region T is excessive. Then, the upper limit threshold setting unit 43 subtracts 1 [K], which is a subtraction constant, from the current upper limit threshold U to set a new upper limit threshold U, and then returns the procedure. For example, when the upper limit threshold U is an initial value of 5 [K], 4 [K] obtained by subtracting 1 [K] from the 5 [K] is set as a new upper limit threshold.

  By performing the subtraction process on the upper limit threshold value U [K], the width of the set temperature difference region T is reduced and it is possible to prevent the cooling efficiency from being lowered.

  On the other hand, when the number of huntings N is greater than 0 (step S202: Yes), the set temperature difference region changing unit 40 moves the procedure to step S204.

  Next, the set temperature difference region changing means 40 determines whether or not the number of huntings N is greater than 3 which is a preset hunting upper limit number (step S204).

  When the number of huntings N is not larger than 3, that is, when the number of huntings N is 1 or 2 (step S204: Yes), the set temperature difference region changing means 40 has an appropriate width of the set temperature difference region T. And the procedure is returned as it is.

  On the other hand, the set temperature difference region changing means 40 determines that the width of the set temperature difference region T is too small when the hunting number N is 3 or more (step S204: No), and the upper limit threshold setting unit 43 A new upper threshold value U is set by adding 1 [K], which is an addition constant, from the current upper threshold value U. For example, when the upper limit threshold U is the initial value of 5 [K], 6 [K] obtained by adding 1 [K] to the 5 [K] is set as the new upper limit threshold U.

  By performing addition processing on the upper limit threshold value U [K], the width of the set temperature difference region T is increased. Therefore, the number of times hunting N is reduced, and the cooling device can be operated stably.

  FIG. 6 shows a summary of the determination performed by the set temperature difference region changing unit 40 and the processing performed by the upper threshold setting unit 43. That is, the set temperature difference region changing means 40 determines that the width of the set temperature difference region T is excessive when the hunting count N is 0, which is the hunting lower limit count, and the upper limit threshold setting unit 43 The width of the set temperature difference region T is narrowed by performing the subtraction process of the upper limit threshold value U, and the width of the set temperature difference region T is too small when the number of times hunting N is 3 or more, which is the upper limit number of hunting times. When the upper limit threshold setting unit 43 adds the upper limit threshold U, the width of the set temperature difference region T is widened, and the hunting count N is larger than the hunting lower limit count and smaller than the hunting upper limit count. Therefore, it is determined that the width of the set temperature difference region T is appropriate, and the width of the set temperature difference region T is maintained.

  Therefore, according to this refrigerant flow control device, even if the current operating environment changes due to load fluctuations according to the season, the frosting state of the evaporator 12, etc., the set temperature difference depends on the change in the environment. The width of the set temperature difference region T can be changed by the region changing means 40. Therefore, it is possible to prevent the cooling efficiency from steadily decreasing and to prevent the compressor 15 from being damaged due to the occurrence of the liquid back, so that the cooling device can be operated stably. can do.

  In the first embodiment described above, the setting temperature difference region changing unit 40 arbitrarily changes the width of the setting temperature difference region T according to the number of times of hunting. However, the present invention is not limited to this, and for example, a maximum upper limit threshold that restricts the addition process to the upper limit threshold U may be provided.

  Further, in the above-described first embodiment, the hunting lower limit number is set to zero. However, the present invention is not limited to this, and the hunting lower limit number may be set to an arbitrary number.

  In the first embodiment described above, the hunting upper limit number is set to 3 times. However, the present invention is not limited to this, and the hunting upper limit number may be set to an arbitrary number as long as it is different from the hunting lower limit number.

  Further, in the above-described first embodiment, the unit time for counting the number of times of hunting is set to 5 minutes. However, the present invention is not limited to this, and the unit time may be set to an arbitrary time.

  In the above-described first embodiment, the lower limit threshold L of the temperature difference Δt1 is set to 1 [K]. However, the present invention is not limited to this, and the lower limit threshold L of the temperature difference Δt1 may be set arbitrarily. However, as described above, if the state in which the temperature difference Δt1 is 0 [K] is maintained, there is a possibility that a liquid back may occur. Therefore, the lower limit threshold L is a value greater than 0 [K]. A thing as small as possible is preferable.

  Furthermore, in the first embodiment described above, the upper limit threshold value U of the temperature difference Δt1 is set to 5 [K]. However, the present invention is not limited thereto, and the upper limit threshold value U of the temperature difference Δt1 may be arbitrarily set as long as it is a value larger than the lower limit threshold value L. However, as described above, when the temperature difference Δt1 is large, the cooling efficiency is lowered. Therefore, it is preferable that the value be as small as possible without causing a liquid back.

  In the first embodiment described above, the addition constant of the addition process performed by the upper limit threshold setting unit 43 is 1 [K]. However, the present invention is not limited to this, and the addition constant is not limited to 1 [K].

  Furthermore, in the first embodiment described above, the case where the subtraction constant of the subtraction process performed by the upper limit threshold setting unit 43 is 1 [K] has been described. However, the present invention is not limited to this, and the subtraction constant is not limited to 1 [K].

  By the way, in the pipe line 12a between the inlet part and the outlet part of the evaporator 12, as shown in FIG. 7, the pipe surface temperature decreases toward the downstream side due to the pressure loss generated in the pipe line 12a. Therefore, the temperature of the refrigerant will similarly decrease. The temperature drop of the refrigerant affects the temperature difference Δt1, but when the control is performed as described above, the opening degree of the electronic expansion valve 13 is controlled without considering the pressure loss ΔT. . As a result, even if the opening degree of the electronic expansion valve is controlled so that the temperature difference Δt1 falls within the range of the set temperature difference region T, the temperature difference Δt1 substantially increased by the pressure loss ΔT becomes the reference. Therefore, there is a problem in improving the cooling efficiency.

[Embodiment 2]
Accordingly, a refrigerant flow control device that further improves the cooling efficiency will be described below. FIG. 8 is an explanatory diagram illustrating a configuration of a cooling device to which the refrigerant flow rate control device according to the second embodiment of the present invention is applied. In the cooling device shown in FIG. 8, the same components as those in the cooling device shown in FIG.

  The evaporator 12 ′ included in the refrigerant flow control device includes an intermediate refrigerant temperature sensor (first temperature sensor) 22.

  The intermediate refrigerant temperature sensor 22 is installed at an intermediate portion between the inlet portion and the outlet portion in the pipe line 12a. The intermediate refrigerant temperature sensor 22 detects the temperature of the refrigerant passing through the intermediate part. In the second embodiment, the intermediate refrigerant temperature sensor 22 is arranged at a position closer to the outlet portion than the inlet portion.

  The valve opening degree adjusting means 30 ′ provided in the refrigerant flow rate control device includes a temperature difference measuring unit 31 ′ and a valve opening degree setting unit 33.

The temperature difference measuring unit 31 ′ calculates the refrigerant temperature detected by the intermediate refrigerant temperature sensor 22 (hereinafter referred to as “intermediate refrigerant temperature T ₃ ”) from the outlet refrigerant temperature T ₂ detected by the second refrigerant temperature sensor 21. The subtracted temperature difference Δt2 is calculated.

  The valve opening degree adjusting means 30 ′ provided in this refrigerant flow rate control device replaces the temperature difference Δt 1 with the temperature difference Δt 2 in the opening degree adjusting process of the electronic expansion valve 13 described in the first embodiment, and performs the same opening degree adjusting process. It is carried out.

  Therefore, when the temperature difference Δt2 is smaller than the lower limit threshold value L [K], the valve opening degree adjusting means 30 ′ reduces the opening degree of the electronic expansion valve 13 and the temperature difference Δt2 becomes the upper limit threshold value U [K]. If larger, the opening degree of the electronic expansion valve 13 is enlarged, and if the temperature difference Δt2 is not less than the lower limit threshold L [K] and not more than the upper limit threshold U [K], the opening of the electronic expansion valve 13 is opened. Keep the degree.

  If the opening adjustment process of the electronic expansion valve 13 is performed in this way, in addition to the effects described above, the opening of the electronic expansion valve 13 can be accurately controlled without being affected by the pressure loss of the conduit 12a. Can do.

  Further, the set temperature difference region changing means 40 ′ provided in the refrigerant flow control device replaces the temperature difference Δt 1 with the temperature difference Δt 2 in the set temperature difference region change process described in the first embodiment, and is similar to the set temperature difference region. Change processing is in progress. That is, the set temperature difference region changing means 40 ′ counts the number of huntings N ′ in which the temperature difference Δt2 falls below the lower threshold L [K] during a preset unit time, and according to the counted number of huntings N ′. Thus, the width of the set temperature difference region T is changed. Specifically, the set temperature difference region changing means 40 counts the number of huntings N ′ in which the temperature difference Δt2 falls below the lower limit threshold L [K] during the unit time, and the number of huntings N ′ is the lower limit number of huntings. In the case of 0 times or less, the upper threshold value setting unit 43 performs subtraction processing of the upper threshold value U to narrow the width of the set temperature difference region T, and the hunting frequency N ′ is 3 times or more that is the hunting upper limit frequency. In this case, the upper threshold value setting unit 43 adds the upper threshold value U so as to widen the set temperature difference region T, and the hunting frequency N ′ is larger than the hunting lower limit frequency and smaller than the hunting upper limit frequency. In this case, the width of the set temperature difference region T is maintained.

  If the set temperature difference region changing process is performed by the set temperature difference region changing means 40 ′ as described above, the width of the set temperature difference region T can be accurately set without being affected by the pressure loss, in addition to the effects described above. Can be controlled.

  In the refrigerant flow rate control apparatus shown in the second embodiment described above, similar to the first embodiment, the same actions and effects can be obtained even if various numerical values are changed to arbitrary numerical values. Of course, the same change as the refrigerant flow control device described in the first embodiment may be applied to the refrigerant flow control device shown in the second embodiment.

  In the second embodiment, the second refrigerant temperature sensor 21 is located at the outlet of the evaporator 12 'and the intermediate refrigerant temperature sensor 22 is located at the middle of the evaporator 12'. . However, the positions of the refrigerant temperature sensors 21 and 22 are not limited to the above, and may be positioned so that the distances from the inlet of the evaporator 12 'are different from each other.

  Further, the second embodiment described above has been described by performing the valve opening degree adjusting process of the electronic expansion valve 13 based on the detection results of the second refrigerant temperature sensor 21 and the intermediate refrigerant temperature sensor 22. However, the present invention is not limited thereto, and the opening degree of the electronic expansion valve 13 may be changed based on the detection result of the first refrigerant temperature sensor 20 in addition to the detection results of the refrigerant temperature sensors 21 and 22.

  A first modification of the refrigerant flow control device that changes the opening of the electronic expansion valve 13 will be described below. FIG. 9 is an explanatory diagram showing a configuration of a cooling device to which the refrigerant flow rate control device of the first modification is applied. In the cooling device shown in FIG. 9, the same components as those of the cooling device shown in FIG. 1 and the cooling device shown in FIG.

  The storage means 25 ′ of this refrigerant flow rate control device further stores an evaporation threshold value LL that is set so that the evaporation completion point is located downstream of the intermediate portion of the pipe 12 a as compared with the storage means 25. . In this modification, for example, it is assumed that 0 [K] is stored in the storage unit 25 ′ as the evaporation threshold LL. In the following description, it is assumed that 1 [K] is stored in the storage unit 25 ′ as the initial value of the lower limit threshold L, and 4 [K] is stored in the storage unit 25 ′ as the initial value of the upper limit threshold U.

The valve opening degree adjusting means 30 a of the refrigerant flow control device includes a second temperature difference measuring unit 35. The second temperature difference measuring unit 35 calculates a temperature difference Δt3 obtained by subtracting the inlet refrigerant temperature T ₁ detected by the first refrigerant temperature sensor 20 from the intermediate refrigerant temperature T ₃ detected by the intermediate refrigerant temperature sensor 22. It is.

  The valve opening degree adjusting means 30a provided in the refrigerant flow rate control device changes the opening degree of the electronic expansion valve 13 based on the temperature difference Δt2, Δt3. Hereinafter, the opening degree adjusting process of the electronic expansion valve 13 performed by the valve opening degree adjusting means 30a will be described with reference to FIG.

When the cooling device is in an operating state, the valve opening degree adjusting means 30a passes through the first refrigerant temperature sensor 20, the second refrigerant temperature sensor 21, and the intermediate refrigerant temperature sensor 22 each time a predetermined time elapses. Temperatures T ₁ , T ₂ , and T ₃ are detected (step S301), and whether or not the temperature difference Δt3 calculated through the second temperature difference measuring unit 35 is equal to or greater than 0 [K], which is a preset evaporation threshold LL. Judgment is made (step S302).

  When the temperature difference Δt3 is equal to or larger than the evaporation threshold LL (step S302: Yes), the valve opening degree adjusting unit 30a performs a process of increasing the opening degree of the electronic expansion valve 13 (step S303), and then the temperature difference. Wait until Δt3 becomes equal to or less than the evaporation threshold LL. On the other hand, if the temperature difference Δt3 is not equal to or greater than the evaporation threshold LL (step S302: No), that is, if the temperature difference Δt3 is smaller than LL, the valve opening degree adjusting means 30a proceeds to step S304 as it is. Since the evaporation threshold LL is set to 0 [K], when the temperature difference Δt3 is not greater than or equal to LL, that is, when the temperature difference Δt3 is smaller than LL, as shown in FIGS. When the evaporation completion point is located in the pipe line 12a on the downstream side of the intermediate portion and the temperature difference Δt3 is LL or more, as shown in FIG. 11 (a), the evaporation completion point is from the intermediate portion. Is also located upstream.

  As described above, by performing the process of increasing the opening degree of the electronic expansion valve 13, the refrigerant flow rate control device always controls the evaporation completion point to be located downstream of the intermediate portion. .

  Next, when the temperature difference Δt2 calculated through the temperature difference measuring unit 31 ′ is smaller than the lower limit threshold L [K] (step S304: No), the valve opening degree adjusting unit 30a reduces the opening degree of the electronic expansion valve 13. (Step S305), the procedure is returned.

  When the opening degree of the electronic expansion valve 13 is reduced, the temperature difference Δt2 increases. As a result, the temperature difference Δt2 changes so as to exceed the lower limit threshold L [K].

  On the other hand, when the temperature difference Δt2 is greater than or equal to the lower limit threshold L [K] (step S304: Yes), the valve opening degree adjusting means 30a proceeds to step S306.

  Next, the valve opening degree adjusting means 30a determines whether or not the temperature difference Δt2 is equal to or less than a preset upper limit threshold value U [K] (step S306).

  When the temperature difference Δt2 is larger than the upper limit threshold U [K] (step S306: No), the valve opening degree adjusting means 30a enlarges the opening degree of the electronic expansion valve 13 (step S307), and then returns the procedure.

  When the opening degree of the electronic expansion valve 13 is increased, the temperature difference Δt2 is reduced. As a result, the temperature difference Δt2 changes so as to fall below the upper limit threshold value U [K].

  On the other hand, when the temperature difference Δt2 is equal to or less than the upper limit threshold U [K] (step S306: Yes), the valve opening degree adjusting means 30a returns the procedure as it is.

  By controlling the temperature difference Δt3 by changing the opening of the electronic expansion valve 13 as described above, the evaporation completion point is located downstream from the intermediate part and upstream from the outlet part. It will be. By controlling in this way, the evaporator 12 'can be used effectively without being affected by the pressure loss ΔT of the pipe 12a, and the compressor 15 is caused by the occurrence of liquid back. Can be prevented from being damaged, and the cooling efficiency can be reliably prevented from decreasing.

  By the way, as described in the first embodiment, even if the opening degree adjusting process of the electronic expansion valve 13 is performed by the valve opening degree adjusting means 30, the temperature difference Δt1 falls below the lower limit threshold L [K], and the state is maintained. In such a case, liquid back will occur. Immediately after the opening of the electronic expansion valve 13 is rapidly reduced and the liquid back is avoided in a state where the liquid back has occurred, the position of the evaporation completion point becomes extremely unstable.

  When the width of the set temperature difference region T is changed by the set temperature difference region changing means 40 in the state where the position of the evaporation completion point is unstable in this way, there is a possibility that the occurrence frequency of the liquid back increases. For example, as shown in FIG. 12, the opening degree of the electronic expansion valve 13 is simply reduced by the valve opening degree adjusting means 30 when the temperature difference Δt1 is smaller than the lower threshold L [K], and the temperature difference Δt1 is If it is larger than the upper limit threshold U, the temperature difference Δt1 will fall below the lower limit threshold L [K] simply by increasing the degree of opening of the electronic expansion valve 13, and this state will be maintained, resulting in liquid back. Then, the evaporation completion point is not stable, and liquid back is continuously generated.

  Therefore, in the refrigerant flow control device of the second embodiment described above, the valve opening degree adjusting means 30 ', 30a is paused for, for example, 5 minutes set in advance when the temperature difference Δt2 falls below the lower limit threshold L [K]. Control may be performed so as to restrict the opening of the electronic expansion valve 13 from increasing until the time has elapsed. The rest time is stored in the storage means 25 '.

  And according to the refrigerant | coolant flow control apparatus which set the said control time, when it falls below lower limit threshold value L [K], the opening degree of the electronic expansion valve 13 is reduced, a liquid back is avoided, and a liquid back is avoided. From a certain time, the expansion of the opening degree of the electronic expansion valve 13 is restricted. Therefore, it is possible to prevent the temperature difference Δt2 from decreasing by not increasing the opening degree of the electronic expansion valve 13 in a state where there is a possibility of liquid back. Therefore, it is possible to prevent the occurrence frequency of liquid back from increasing. For example, if such control is performed, it is possible to prevent the occurrence frequency of liquid back from increasing as shown in FIG. 12 and 13, the thin line indicates the opening degree of the electronic expansion valve, the thick line indicates the presence or absence of the liquid back, and the broken line indicates the upper limit threshold value U.

  In the above-described second embodiment, the description has been made assuming that the rest time is 5 minutes. However, the present invention is not limited to this, and the time until the evaporation completion point in each refrigerant flow control device is stabilized may be changed as appropriate.

  Moreover, even if the restriction time is set in the valve opening degree adjusting means 30 described in the first embodiment, the same operation and effect can be obtained.

By the way, the 2nd modification of the refrigerant | coolant flow control apparatus mentioned above is demonstrated. This refrigerant flow rate control device calculates a temperature difference Δt2 by subtracting the intermediate refrigerant temperature T ₃ detected by the intermediate refrigerant temperature sensor 22 from the outlet refrigerant temperature T ₂ detected by the second refrigerant temperature sensor 21. A second temperature difference measuring unit 35 that calculates a temperature difference Δt3 obtained by subtracting the inlet refrigerant temperature T1 detected by the first refrigerant temperature sensor 20 from the intermediate refrigerant temperature T3 detected by the unit 31 ′ and the intermediate refrigerant temperature sensor 22. And.

  Further, the valve opening degree adjusting means provided in the refrigerant flow control device increases the opening degree of the electronic expansion valve 13 by determining that the temperature difference Δt3 is excessive if the temperature difference Δt3 is equal to or larger than the upper limit threshold value U [K]. When the temperature difference Δt3 is equal to or lower than the upper threshold U [K] and the temperature difference Δt2 is equal to or higher than the lower threshold L [K], it is determined that the temperature differences Δt3 and Δt2 are appropriate, and the opening degree of the electronic expansion valve 13 is set. If the temperature difference Δt3 is equal to or lower than the upper limit threshold U [K] and the temperature difference Δt2 is equal to or lower than the lower limit threshold L [K], it is determined that the liquid is back and the opening of the electronic expansion valve 13 is reduced.

  According to this refrigerant flow control device, even if the conduit 12a of the evaporator 12 is relatively long, it is possible to accurately determine whether or not a liquid back has occurred without being affected by pressure loss.

By the way, the 3rd modification of the refrigerant | coolant flow control apparatus of 2nd Embodiment mentioned above is demonstrated. As in the first modification described above, when the temperature difference Δt2 falls below the lower limit threshold L [K], this refrigerant flow control device regulates the increase in the opening of the electronic expansion valve until the regulation time elapses. To do.

  In the refrigerant flow control device, the temperature difference Δt2 may fall below the lower limit threshold L [K] within a preset second unit time (for example, 10 minutes), and the temperature difference Δt2 may exceed the upper limit threshold U [K]. If it exceeds the predetermined temperature difference, the set temperature difference region changing means determines that the width of the set temperature difference region T is narrow, and adds 1 which is an addition constant to the upper limit threshold value U [K], thereby adding the set temperature difference. While increasing the width of the region T, the valve opening degree adjusting means 30 a maintains the opening degree of the electronic expansion valve 13.

  Thus, by increasing the width of the set temperature difference region, it is possible to reduce the possibility that the temperature difference Δt2 falls below the lower limit threshold L [K]. Therefore, the risk of liquid back can be reduced.

  Further, the refrigerant flow control device has a temperature difference Δt2 that exceeds the lower limit threshold L [K] in a state in which the temperature difference Δt2 has fallen below the lower limit threshold L [K] within a preset second unit time. If it is below the upper threshold value U [K], the set temperature difference region changing means determines that the width of the set temperature difference region T is appropriate, and maintains the size of the upper limit threshold value U [K]. .

  On the other hand, when the refrigerant flow rate control device maintains a state in which the temperature difference Δt2 exceeds the lower limit threshold L [K] in the second unit time set in advance, in other words, in the second unit time set in advance. The temperature difference Δt2 never falls below the lower threshold L [K], and the temperature difference Δt2 is higher than the lower threshold L [K] and lower than the upper threshold U [K]. In some cases, the set temperature difference region changing means determines that the width of the set temperature difference region T is excessive, and subtracts 1 which is a subtraction constant from the upper limit threshold value U [K] to thereby reduce the width of the set temperature difference region T. To narrow. Energy saving operation can be realized by narrowing the width of the set temperature difference region T.

  However, if the upper limit threshold U [K] is set small, hunting may occur. Therefore, the valve opening degree adjusting means 30a sets a minimum lower limit value for the temperature difference Δt2, and sets the minimum lower limit value as the temperature difference. It regulates that Δt2 falls below.

It is explanatory drawing which shows the structure of the cooling device to which the refrigerant | coolant flow control apparatus which is Embodiment 1 of this invention is applied. It is a graph which shows the temperature distribution of the refrigerant | coolant in the evaporator of the cooling device shown in FIG. It is a flowchart which shows the content of the opening degree adjustment process which the valve opening degree adjustment means with which the refrigerant | coolant flow control apparatus shown in FIG. 3 is a chart showing a relationship between determination of a temperature difference Δt1 performed by the valve opening degree adjusting means and control performed based on the determination when the opening degree of the electronic expansion valve is adjusted by the refrigerant flow control device shown in FIG. It is a flowchart which shows the content of the setting temperature difference area change process which the setting temperature difference area change means with which the refrigerant | coolant flow control apparatus shown in FIG. 1 shows the relationship between the determination of the width of the set temperature difference area performed by the set temperature difference area changing means and the control performed based on the determination when the set temperature difference area changing process is performed by the refrigerant flow rate control device shown in FIG. It is a chart. It is the graph which showed the temperature distribution of the refrigerant | coolant in the evaporator with which the cooling device shown in FIG. 1 is provided. It is explanatory drawing which shows the structure of the cooling device to which the refrigerant | coolant flow control apparatus which is Embodiment 2 of this invention is applied. It is explanatory drawing which shows the structure of the modification of the cooling device shown in FIG. It is a flowchart which shows the content of the opening degree adjustment process which the valve opening degree adjustment means with which the refrigerant | coolant flow control apparatus shown in FIG. 9 is provided implements. It is the graph which showed the temperature distribution of the refrigerant | coolant in the evaporator with which the cooling device shown in FIG. 10 is provided. In the cooling apparatus shown in Embodiment 1, it is a graph which shows the relationship between the magnitude | size of the opening degree of an electronic expansion valve, and time, the relationship between the presence or absence of a liquid back, and time, and the relationship between an upper limit threshold value and time. In the cooling device shown in Embodiment 2, it is a graph which shows the relationship between the magnitude | size of the opening degree of an electronic expansion valve, and time, the relationship between the presence or absence of a liquid back, and time, and the relationship between an upper limit threshold value and time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Container 11 Open showcase 12 Evaporator 12a Pipe line 13 Electronic expansion valve 14 Condenser 15 Compressor 16 Refrigerant supply line 17 Blower fan 19 Control means 20 1st refrigerant | coolant temperature sensor (1st temperature sensor)
21 Second refrigerant temperature sensor (second temperature sensor)
22 Intermediate refrigerant temperature sensor (first temperature sensor)
25 storage means 25 'storage means 30 valve opening adjusting means 30' valve opening adjusting means 30a valve opening adjusting means 31 temperature difference measuring part 31 'temperature difference measuring part 33 valve opening setting part 35 second temperature difference measuring part 40 preset temperature difference region changing unit 40 'sets the temperature difference region changing unit 42 lower threshold below count measuring unit 43 the upper threshold setting unit L lower threshold LL evaporated threshold N hunting number N' hunting count T set temperature difference region T ₁ inlet refrigerant Temperature T ₂ outlet refrigerant temperature T ₃ middle refrigerant temperature U upper limit threshold ΔT pressure loss Δt1 temperature difference Δt2 temperature difference Δt3 temperature difference

Claims (5)

An electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening;
A first temperature sensor and a second temperature sensor arranged in a pipe line arranged so that the refrigerant passes through the evaporator, the distances from the inlet of the evaporator being different from each other;
When the temperature difference between the refrigerant temperature detected by the first temperature sensor and the refrigerant temperature detected by the second temperature sensor is smaller than a preset lower limit threshold, the opening of the electronic expansion valve is reduced. And a refrigerant flow rate control device comprising: a valve opening degree adjusting means for expanding the opening degree of the electronic expansion valve when the temperature difference is larger than a preset upper limit threshold value;
The number of huntings where the temperature difference falls below the lower limit threshold is counted in a preset unit time, and the width of the set temperature difference area determined by the lower limit threshold and the upper limit threshold is changed according to the counted number of huntings. A refrigerant flow rate control device comprising a set temperature difference region changing means. The set temperature difference region changing means includes:
If the number of huntings below the lower threshold is less than or equal to a preset hunting lower limit, the width of the set temperature difference region is narrowed,
If the number of huntings below the lower threshold is equal to or greater than the preset upper limit of hunting, the set temperature difference area is widened, and the number of huntings below the lower threshold is greater than the preset lower limit of hunting. The refrigerant flow rate control device according to claim 1, wherein when the number is less than the upper limit number, the width of the set temperature difference region is maintained. 2. The refrigerant flow rate control device according to claim 1, wherein the first temperature sensor is located at an inlet portion of the evaporator, and the second temperature sensor is located at an outlet portion of the evaporator. The first temperature sensor is located at an intermediate portion between an inlet portion and an outlet portion of the evaporator, and the second temperature sensor is located at an outlet portion of the evaporator. The refrigerant flow control device according to 1.   The valve opening adjusting means restricts the expansion of the opening of the electronic expansion valve until a preset restriction time elapses when the temperature difference falls below the lower threshold. The refrigerant flow control device according to 1.

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