JP4798116B2 - Refrigerant flow control device - Google Patents

Description

  The present invention is an aspect in which the distance from the inlet portion is different between the electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening degree and the inlet portion to the outlet portion of the refrigerant flow passage in the evaporator. The present invention relates to a refrigerant flow rate control device including three temperature sensors installed in the above and valve opening degree adjusting means for adjusting the opening degree of an electronic expansion valve according to the detection results of those temperature sensors.

  For example, in an open 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 refrigerant is supplied and circulated to the evaporator, the compressor, the condenser, and the electronic expansion valve to constitute a refrigeration cycle, and the inside of the container is maintained at a predetermined temperature state by the refrigeration cycle.

  In this type of open showcase, there is an electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening, and between the inlet part and outlet part of the refrigerant flow passage (evaporator pipe) in the evaporator. In addition, there are some equipped with three temperature sensors installed in a manner in which the distances from the inlet portions are different from each other, and a valve opening degree adjusting means for adjusting the opening degree of the electronic expansion valve according to the detection result of those temperature sensors. . Each temperature sensor is attached to, for example, the circumferential surface of the evaporator tube, and detects the temperature of the refrigerant tube passing through the position by detecting the temperature of the surface of the evaporator tube at the installation position. Of these three temperature sensors, the first temperature sensor (inlet side temperature sensor) is installed, for example, at the inlet of the evaporation pipe, and the second temperature sensor (outlet side temperature sensor) is located at the outlet of the evaporator pipe. The third temperature sensor (intermediate temperature sensor) is installed at an intermediate position between the inlet and outlet of the evaporation pipe.

  This open showcase prevents the cooling efficiency from decreasing by controlling the amount of refrigerant flowing into the evaporator with an electronic expansion valve according to the detection results of the three temperature sensors, and from the outlet of the evaporator. A phenomenon called a so-called liquid back, in which a mixture of a liquid refrigerant and a gaseous refrigerant is discharged and enters the compressor, is prevented.

  Specifically, the opening degree of the electronic expansion valve is set as described below according to a temperature difference (so-called superheat degree) obtained by subtracting the intermediate temperature detected by the intermediate temperature sensor from the outlet side temperature detected by the outlet side temperature sensor. change.

  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, thereby preventing the occurrence of liquid back. . By preventing the occurrence of this liquid back, it is possible to prevent the compressor from being damaged due to the occurrence of the liquid back.

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

  In addition, when the inlet side temperature is lower than the intermediate temperature, the above refrigerant flow rate control device reduces the cooling efficiency in consideration of the pressure loss generated in the evaporation pipe by increasing the opening of the electronic expansion valve. (For example, see Japanese Patent Application No. 2006-179966).

  By the way, in the said refrigerant | coolant flow control apparatus, when the said temperature sensor remove | deviates from an evaporation pipe, there exists a possibility that regular temperature cannot be detected with a temperature sensor. More specifically, when the temperature sensor is removed from the evaporator tube, the temperature sensor detects the temperature of the air around the evaporator tube. Since the temperature of the air around the evaporator tube is higher than the surface temperature of the evaporator tube, the temperature sensor detects a temperature higher than the normal temperature. Thus, when there is even one temperature sensor that cannot detect the normal temperature, it is impossible to control the opening degree of the electronic expansion valve that prevents the cooling efficiency from decreasing and prevents the occurrence of liquid back.

  In order to solve this problem, it is necessary to provide a drop-off detection sensor for each temperature sensor for detecting that the temperature sensor has been detached from the evaporation pipe. However, when such a drop detection sensor is provided in each temperature sensor, the number of parts increases.

  In view of the above circumstances, the present invention provides a refrigerant flow rate control device capable of preventing a decrease in cooling efficiency, preventing the occurrence of liquid back, and preventing the increase in the number of components as much as possible. is there.

  In order to achieve the above object, the invention according to claim 1 includes an electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening, and an inlet portion to an outlet portion of the refrigerant flow passage in the evaporator. Until the inlet side temperature detected by the three temperature sensors installed at different distances from the inlet part and the inlet side temperature sensor installed at the most upstream side is the downstream side of the inlet side temperature sensor. If the temperature is lower than the intermediate temperature detected by the intermediate temperature sensor installed at the intermediate temperature sensor, the opening of the electronic expansion valve is expanded and the intermediate temperature is detected from the outlet side temperature detected by the outlet side temperature sensor installed downstream of the intermediate temperature sensor. When the temperature difference obtained by subtracting the temperature is smaller than a preset lower limit threshold, the opening degree of the electronic expansion valve is reduced. On the other hand, when the temperature difference is greater than a preset upper limit threshold, the electronic expansion valve Opening A valve opening degree adjusting means that expands, calculates an upstream temperature difference obtained by subtracting the inlet side temperature from the intermediate temperature, and calculates a downstream temperature difference obtained by subtracting the outlet side temperature from the intermediate temperature; A side temperature difference is compared with a preset first threshold value, and the downstream temperature difference is compared with a preset second threshold value, and the upstream temperature difference is greater than the first threshold value and the downstream side. Error output means for outputting an error on condition that the side temperature difference is larger than a second threshold value.

  In order to achieve the above object, the invention according to claim 2 includes an electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening, and an inlet portion of the refrigerant flow passage in the evaporator. The temperature on the inlet side detected by the three temperature sensors installed at different distances from the inlet part to the outlet part and the inlet side temperature sensor installed on the most upstream side is the temperature of the inlet side temperature sensor. When the temperature is lower than the intermediate temperature detected by the intermediate temperature sensor installed on the downstream side, the opening of the electronic expansion valve is enlarged, and from the outlet side temperature detected by the outlet side temperature sensor installed on the downstream side of the intermediate temperature sensor. When the temperature difference obtained by subtracting the intermediate temperature is smaller than a preset lower limit threshold, the opening degree of the electronic expansion valve is reduced. On the other hand, when the temperature difference is greater than a preset upper limit threshold, the electronic expansion is reduced. valve A valve opening degree adjusting means for enlarging the opening degree, calculating an upstream temperature difference obtained by subtracting the inlet side temperature from the intermediate temperature, and calculating a downstream temperature difference obtained by subtracting the outlet side temperature from the intermediate temperature. Comparing the upstream temperature difference with a preset first threshold value and comparing the downstream temperature difference with a preset second threshold value, wherein the upstream temperature difference is greater than the first threshold value, And an error output means for outputting an error when the downstream temperature difference is larger than a second threshold value.

  According to the refrigerant flow control device of the first aspect, when the temperature difference obtained by subtracting the intermediate temperature from the outlet side temperature is smaller than the preset lower limit threshold, the valve opening degree adjusting means adjusts the opening degree of the electronic expansion valve. Since the size is reduced, the occurrence of liquid back can be prevented. In addition, when the temperature difference is larger than the preset upper limit threshold, the valve opening degree adjusting means enlarges the opening degree of the electronic expansion valve, so that it is possible to prevent the cooling efficiency from being lowered.

  In addition, according to the refrigerant flow control device of the present invention, when the inlet side temperature is lower than the intermediate temperature, the valve opening degree adjusting means increases the opening degree of the electronic expansion valve. It is possible to prevent the cooling efficiency from being lowered in consideration of the generated pressure loss.

  In addition, in the state where the cooling device is operating, there is no situation where the intermediate temperature is higher than the inlet side temperature and higher than the outlet side temperature, and the situation described above only when the intermediate temperature sensor is removed from the refrigerant flow path. The refrigerant flow rate control device according to the present invention calculates the upstream temperature difference obtained by subtracting the inlet side temperature from the intermediate temperature, and calculates the downstream temperature difference obtained by subtracting the outlet temperature from the intermediate temperature. The upstream temperature difference is compared with a preset first threshold value, the downstream temperature difference is compared with a preset second threshold value, the upstream temperature difference is greater than the first threshold value, and the downstream side Error output means for outputting an error on condition that the temperature difference is larger than the second threshold value is provided. According to such a refrigerant flow control device, it is possible to detect that the intermediate temperature is higher than the inlet side temperature and higher than the outlet side temperature, so that the intermediate temperature sensor is removed from the refrigerant flow passage. It is possible to detect. Accordingly, the intermediate temperature sensor of the three temperature sensors does not need to be provided with a drop-off detection sensor that detects that the intermediate temperature sensor has been removed from the refrigerant flow path, and thus prevents an increase in the number of parts as much as possible. be able to.

  According to the refrigerant flow control device of the second aspect, when the temperature difference obtained by subtracting the intermediate temperature from the outlet side temperature is smaller than the preset lower limit threshold, the valve opening degree adjusting means adjusts the opening degree of the electronic expansion valve. Since the size is reduced, the occurrence of liquid back can be prevented. In addition, when the temperature difference is larger than the preset upper limit threshold, the valve opening degree adjusting means enlarges the opening degree of the electronic expansion valve, so that it is possible to prevent the cooling efficiency from being lowered.

  In addition, according to the refrigerant flow control device of the present invention, when the inlet side temperature is lower than the intermediate temperature, the valve opening degree adjusting means increases the opening degree of the electronic expansion valve. It is possible to prevent the cooling efficiency from being lowered in consideration of the generated pressure loss.

  In addition, in the state where the cooling device is operating, there is no situation where the intermediate temperature is higher than the inlet side temperature and higher than the outlet side temperature, and the situation described above only when the intermediate temperature sensor is removed from the refrigerant flow path. The refrigerant flow rate control device according to the present invention calculates the upstream temperature difference obtained by subtracting the inlet side temperature from the intermediate temperature, and calculates the downstream temperature difference obtained by subtracting the outlet temperature from the intermediate temperature. The upstream temperature difference is compared with a preset first threshold value, the downstream temperature difference is compared with a preset second threshold value, the upstream temperature difference is greater than the first threshold value, and the downstream side Error output means for outputting an error when the temperature difference is larger than the second threshold value is provided. According to such a refrigerant flow control device, it is possible to detect that the intermediate temperature is higher than the inlet side temperature and higher than the outlet side temperature, so that the intermediate temperature sensor is removed from the refrigerant flow passage. It is possible to detect. Accordingly, the intermediate temperature sensor of the three temperature sensors does not need to be provided with a drop-off detection sensor that detects that the intermediate temperature sensor has been removed from the refrigerant flow path, and thus prevents an increase in the number of parts as much as possible. be able to.

  Hereinafter, preferred embodiments of a refrigerant flow control device according to the present invention will be described in detail with reference to the accompanying drawings as appropriate.

  FIG. 1 is an explanatory diagram showing a configuration of a cooling device to which a refrigerant flow rate control device according to an embodiment of the present invention is applied. The cooling device illustrated here is applied to the open showcase 11 that displays and sells products stored in the storage 10 in a cooled state. For example, the cooling device includes an evaporator 12 in the storage 10 while storing the product. An electronic expansion valve 13 is provided outside the cabinet 10 inside the casing of the open showcase 11, and a compressor 15 and a condenser 14 are provided outside the casing of 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 be stored as 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 compressed by the compressor 15, so that it becomes high-temperature and high-pressure gas refrigerant and is supplied to the condenser 14 again. In this embodiment, when an opening degree command is given as the electronic expansion valve 13, the opening degree is changed according to the opening degree command, and the amount of refrigerant flowing into the evaporator 12 is adjusted according to the opening degree. Apply what you can. In addition, an evaporation pipe 12 a is disposed inside the evaporator 12. The evaporation pipe 12 a constitutes a flow path through which the refrigerant passes inside the evaporator 12.

  Three temperature sensors 21, 22 and 23 are installed between the inlet portion and the outlet portion of the evaporation pipe 12 a in the evaporator 12 in such a manner that the distances from the inlet portion are different from each other. Each temperature sensor 21, 22, 23 is attached to, for example, the peripheral surface of the evaporation pipe 12 a, and approximately detects the refrigerant temperature passing through the position by detecting the surface temperature of the evaporation pipe 12 a at the attachment position. To do.

  Of the temperature sensors 21, 22, and 23, the first temperature sensor (inlet side temperature sensor) 21 is attached to the peripheral surface of the inlet portion of the evaporation pipe 12a. The first temperature sensor 21 approximately detects the refrigerant temperature passing through the inlet portion of the evaporation pipe 12a (hereinafter, the refrigerant temperature detected by the first temperature sensor 21 is simply referred to as “inlet side temperature”. (Inlet portion refrigerant temperature) T1 ”).

  Of the temperature sensors 21, 22, and 23, the second temperature sensor (intermediate temperature sensor) 22 is attached to a circumferential surface at an intermediate position between the inlet portion and the outlet portion of the evaporation pipe 12 a. The second temperature sensor 22 approximately detects the refrigerant temperature passing through the intermediate portion of the evaporation pipe 12a (hereinafter, the refrigerant temperature detected by the second temperature sensor 22 is simply referred to as “intermediate temperature ( Intermediate refrigerant temperature) T2 ”). In the present embodiment, the second temperature sensor 22 is attached in the vicinity of the outlet portion of the evaporation pipe 12a.

  Of the temperature sensors 21, 22, and 23, the third temperature sensor (outlet temperature sensor) 23 is attached to the peripheral surface of the outlet portion of the evaporation pipe 12a. The third temperature sensor 23 approximately detects the temperature of the refrigerant passing through the outlet portion of the evaporation pipe 12a (hereinafter, the refrigerant temperature detected by the third temperature sensor 23 is simply referred to as “exit side temperature”). (Exit portion refrigerant temperature) T3 ").

  That is, in the refrigerant flow control device described above, the first temperature sensor 21 is installed on the most upstream side among the three temperature sensors 21, 22 and 23, and the second temperature sensor 22 is arranged on the downstream side of the first temperature sensor 21. The third temperature sensor 23 is installed on the downstream side of the second temperature sensor 22. The first temperature sensor 21 and the third temperature sensor 23 are provided with a drop-off detection sensor (not shown) that detects that the temperature sensors 21 and 23 are detached from the evaporation pipe 12a.

  The refrigerant flow control device is provided with a control means 19. The control means 19 is an electronic computer (hardware) that comprehensively controls the refrigerant flow rate control device, and includes a storage unit 25 and a valve opening degree adjustment means (error output means) 30.

  The storage unit 25 stores a program and data for operating the refrigerant flow control device. The storage unit 25 stores a lower limit threshold L [K] and an upper limit threshold U [K]. In this embodiment, for example, 1 [K] is stored as the lower limit threshold L, and 5 [K] is stored as the upper limit threshold U. The storage unit 25 stores a first cycle time and a second cycle time. The first cycle time is set to 15 seconds, for example, based on an interval for performing an opening adjustment process for the electronic expansion valve 13 and an error detection process, which will be described later. The second cycle time is set to 5 minutes, for example. Further, the storage unit 25 stores a first threshold value α1 and a second threshold value α2. In the present embodiment, 0 is stored as the first threshold value α1, and 0 is stored as the second threshold value α2. The first threshold value α1 is used to calculate whether or not the intermediate temperature T2 is higher than the inlet side temperature T1, and the second threshold value α2 is used to calculate whether or not the intermediate temperature T2 is higher than the outlet side temperature T3. Is for.

  As will be described later, the valve opening adjusting means 30 gives an opening command to the electronic expansion valve 13 according to the detection results of the three temperature sensors 21, 22, and 23, thereby controlling the opening of the electronic expansion valve 13. This is an adjustment (software), and includes a temperature difference calculation unit 31, a comparison unit 32, a valve opening setting unit 34, an upstream temperature difference calculation unit 36, and a downstream temperature difference calculation unit 37.

  The temperature difference calculation unit 31 calculates a temperature difference (superheat degree) Δt1 (T3−T2 = Δt1) obtained by subtracting the intermediate temperature T2 detected by the second temperature sensor 22 from the outlet side temperature T3 detected by the third temperature sensor 23. Is to be calculated.

  The comparison unit 32 compares the level of the inlet temperature T1 detected by the first temperature sensor 21 with the intermediate temperature T2 detected by the second temperature sensor 22.

  The upstream temperature difference calculation unit 36 calculates an upstream temperature difference X (T2−T1 = X) obtained by subtracting the inlet temperature T1 detected by the first temperature sensor 21 from the intermediate temperature T2 detected by the second temperature sensor 22. Is to be calculated.

  The downstream temperature difference calculator 37 calculates a downstream temperature difference Y (T2−T3 = Y) obtained by subtracting the outlet temperature T3 detected by the third temperature sensor 23 from the intermediate temperature T2 detected by the second temperature sensor 22. Is to be calculated.

  The valve opening degree setting unit 34 compares the temperature difference Δt1 calculated by the temperature difference calculating unit 31 with the lower limit threshold L and the upper limit threshold U stored in the storage unit 25, and the state of the evaporator 12 is determined from the comparison result. The opening degree command is not transmitted to the electronic expansion valve 13 or the opening degree command is transmitted to the electronic expansion valve 13 according to the state of the evaporator 12. Specifically, the valve opening setting unit 34 determines that the temperature difference Δt1 is appropriate when the temperature difference Δt1 is equal to or greater than the lower limit threshold L and equal to or less than the upper limit threshold U. When the opening degree command is not transmitted to maintain the opening degree and the temperature difference Δt1 is smaller than the lower limit threshold L, it is determined that the liquid back has occurred and the opening degree is reduced to the electronic expansion valve 13 If the temperature difference Δt1 is larger than the upper limit threshold value U, an opening degree increase indicating that the temperature difference Δt1 is excessive and the opening degree is expanded to the electronic expansion valve 13 is transmitted. The command is transmitted.

  In addition, when the cooling device is in operation, the valve opening degree setting unit 34 is based on the comparison result by the comparison unit 32 and is an evaporation completion point, which will be described later, located upstream of the installation position of the second temperature sensor 22. If it is determined that the evaporation completion point is on the upstream side of the installation position of the second temperature sensor 22, an opening degree expansion command is given to the electronic expansion valve 13. Specifically, when the inlet side temperature T1 is higher than the intermediate temperature T2 when the inlet side temperature T1 is compared with the intermediate temperature T2 through the comparison unit 32 (T1> T2), Is determined that the evaporation completion point is downstream of the installation position of the second temperature sensor 22 and does not transmit the opening degree command to the electronic expansion valve 13, while the inlet side temperature T1 is not higher than the intermediate temperature T2, That is, when the inlet side temperature T1 is equal to or lower than the intermediate temperature T2 (T1 ≦ T2), it is determined that the evaporation completion point is on the upstream side of the installation position of the second temperature sensor 22, and the electronic expansion valve 13 is opened. Gives an enlargement command.

  Further, the valve opening setting unit 34 compares the upstream temperature difference X calculated by the upstream temperature difference calculation unit 36 with the first threshold value α1 in the state where the cooling device is operating, and the downstream side. The downstream temperature difference Y calculated by the side temperature difference calculation unit 37 is compared with the second threshold value α2, and based on the comparison result, it is determined whether or not the second temperature sensor 22 is detached from the evaporation pipe 12a. Is. When the valve opening degree setting unit 34 determines that the second temperature sensor 22 is detached from the evaporation pipe 12a based on the comparison result, the valve opening setting unit 34 transmits an error display command to the display device 40 (outputs an error), for example. The display device (display means) 40 is constituted by a liquid crystal panel, for example.

  Such a cooling device can effectively use the evaporator 12 by positioning the evaporation completion point downstream of the installation position of the second temperature sensor 22 and making the temperature difference Δt1 as small 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 an outline of the temperature distribution of the refrigerant in the evaporation pipe 12a of 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). In the vicinity of the downstream side). Specifically, it has a feature that the refrigerant temperature rapidly increases in the vicinity of the downstream side of the evaporation completion point. As shown in FIGS. 2B to 2D, when the evaporation completion point is located downstream of the installation position of the second temperature sensor 22, when the temperature difference Δt1 is large, the inlet of the evaporation pipe 12a. On the other hand, when the temperature difference Δt1 is small, it is close to the outlet of the evaporation pipe 12a.

  Therefore, in a state where the evaporation completion point is located downstream of the installation position of the second temperature sensor 22, when the temperature difference Δt1 is gradually reduced by gradually increasing the opening of the electronic expansion valve 13, As shown in FIGS. 2B to 2D, the evaporation completion point gradually approaches the outlet of the evaporation pipe 12a. Further, although not illustrated, when the evaporation completion point is located downstream of the installation position of the third temperature sensor 23 and the temperature difference Δt1 is maintained at approximately 0 [K], the outlet of the evaporation pipe 12a is maintained. A so-called liquid back phenomenon occurs in which a mixture of a gaseous refrigerant and a liquid refrigerant is discharged from the section and enters the compressor 15. 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, when the temperature difference Δt1 becomes a large value, for example, as shown in FIG. 2B, or as shown in FIG. 2A, the evaporation is completed upstream of the installation position of the second temperature sensor 22. When the state where the point is located is maintained, the cooling efficiency of the cooling device is lowered.

  Therefore, the cooling device is operated so that the evaporation completion point is located downstream of the installation position of the second temperature sensor 22, and as much as possible so as not to damage the compressor due to the occurrence of liquid back. By operating in a state where the temperature difference Δt1 is small, energy saving operation can be realized. 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 later is performed by the valve opening degree adjusting means 30.

  Further, in the evaporation pipe 12a, as shown in FIG. 3, when the refrigerant is in a gas-liquid two-phase state, the pipe surface temperature of the evaporation pipe 12a decreases toward the downstream side due to the pressure loss ΔT generated in the evaporation pipe 12a. . Further, similarly to the tube surface temperature of the evaporation tube 12a, the temperature of the refrigerant also decreases. This temperature drop of the refrigerant affects the refrigerant flow control device. In this refrigerant flow control device, the pressure loss ΔT is taken into consideration, and the opening degree of the electronic expansion valve 13 is set as described below. I have control.

  The opening degree adjusting means 30 provided in the refrigerant flow control device changes the opening degree of the electronic expansion valve 13 based on the temperature difference Δt1, the inlet side temperature T1, and the intermediate temperature T2, and the opening degree of the valve is adjusted. The contents of the opening adjustment process of the electronic expansion valve 13 performed by the adjusting means 30 are shown in FIG. Hereinafter, operation | movement of a refrigerant | coolant flow control apparatus is demonstrated using FIG.

  When the first cycle time stored in advance in the storage unit 25 has elapsed under the operating state of the cooling device (step S101: Yes), the valve opening degree adjusting means 30 is set to the first temperature sensor 21 and the second temperature sensor 21. After each refrigerant temperature T1, T2, T3 is detected through the temperature sensor 22 and the third temperature sensor 23 (step S102), is the inlet side temperature T1 lower than the intermediate temperature T2 through the comparison unit 32 (T1 <T2)? It is determined whether or not (step S103).

  The reason for this operation will be described in detail. The state where the inlet side temperature T1 is lower than the intermediate temperature T2 (T1 <T2) (step S103: Yes) is the gas-liquid 2 as described above with reference to FIG. Considering that in the phase state, the refrigerant temperature gradually decreases as it goes downstream due to the pressure loss of the evaporation pipe 12a, and that the refrigerant temperature rapidly increases near the downstream side of the evaporation completion point, for example, FIG. The evaporation completion point shown in (b) to (d) is not established in a state where the evaporation completion point is located downstream of the installation position of the second temperature sensor 22. For example, as shown in FIG. However, it is the state located in the upstream rather than the installation position of the 2nd temperature sensor 22. FIG. In a state where the evaporation completion point is located upstream of the installation position of the second temperature sensor 22, the cooling efficiency of the cooling device is reduced. Based on this, the valve opening degree adjusting means 30 issues an opening degree enlargement command to the electronic expansion valve 13 through the valve opening degree setting unit 34 so that the evaporation completion point is located downstream of the installation position of the second temperature sensor 22. Transmit (step S104). When the opening degree expansion command is given to the electronic expansion valve 13, the electronic expansion valve 13 performs an opening degree expanding operation. When the electronic expansion valve 13 expands the opening, the evaporation completion point gradually moves toward the downstream side, and when the evaporation completion point moves to the downstream side of the installation position of the second temperature sensor 22, The inlet side temperature T1 becomes higher than the intermediate temperature T2 (T1> T2) (for example, the state shown in FIGS. 2B to 2D).

  On the other hand, when the inlet side temperature T1 is not lower than the intermediate temperature T2 (step S103: No), that is, when the inlet side temperature T1 is equal to or higher than the intermediate temperature T2 (T1 ≧ T2), the valve opening degree adjusting means 30 It is determined that the evaporation completion point is downstream of the installation position of the second temperature sensor 22 through the valve opening setting unit 34, and the procedure is directly transferred to step S105 without transmitting the opening command to the electronic expansion valve 13. .

  The reason for this operation will be described in detail. First, the state where the inlet side temperature T1 is equal to or higher than the intermediate temperature T2 (T1 ≧ T2) is the gas-liquid two-phase state as described above with reference to FIG. Considering that the refrigerant temperature gradually decreases as it goes downstream due to the pressure loss of the evaporation pipe 12a, and that the refrigerant temperature rapidly rises near the downstream side of the evaporation completion point, for example, FIG. 2), the evaporation completion point is not established in a state where it is located upstream of the installation position of the second temperature sensor 22. For example, the evaporation completion points shown in FIGS. In this state, the second temperature sensor 22 is located downstream from the installation position. In this state, since the cooling device can be operated while preventing the cooling efficiency from being lowered, the process proceeds to the next procedure without transmitting the opening degree command to the electronic expansion valve 13.

  Therefore, this refrigerant flow control device always performs the opening degree adjustment process of the electronic expansion valve 13 so that the evaporation completion point is located downstream of the installation position of the second temperature sensor 22. By performing this process, the evaporator 12 can be used effectively without being affected by the pressure loss ΔT of the evaporation pipe 12a.

  Next, the valve opening degree adjusting means 30 causes the temperature difference Δt1 as the calculation result of the temperature difference calculating unit 31 to be greater than or equal to a preset lower threshold L [K] (L ≦ Δt1 = T3) through the valve opening setting unit 34. -T2) is determined (step S105).

  When the temperature difference Δt1 is not greater than or equal to the lower limit threshold L [K], that is, when the temperature difference Δt1 is smaller than the lower limit threshold L [K] ((L> Δt1) (step S105: No), It is determined that a liquid back is generated through the opening setting unit 34, and an opening reduction command is transmitted to the electronic expansion valve 13 (step S106), and the procedure is returned to the electronic expansion valve 13. The opening reduction command is sent to the electronic expansion valve 13. When the electronic expansion valve 13 reduces the opening degree, the temperature difference Δt1 gradually increases and eventually the temperature difference Δt1 becomes the lower limit. It will change so that it may exceed threshold value L [K].

  On the other hand, when the valve opening degree adjusting means 30 determines that the temperature difference Δt1 is greater than or equal to the lower threshold L [K] (L ≦ Δt1) through the valve opening degree setting unit 34 (step S105: Yes), the procedure is stepped. The process proceeds to S107.

  Next, the valve opening degree adjusting means 30 causes the temperature difference Δt1 as the calculation result of the temperature difference calculating unit 31 to be equal to or less than a preset upper limit threshold U [K] (Δt1 = T3-T2) through the valve opening degree setting unit 34. It is determined whether or not ≦ U) (step S107).

  When the temperature difference Δt1 is not less than or equal to the upper limit threshold U [K], that is, when the temperature difference Δt1 is greater than the upper limit threshold U [K] (Δt1> U) (step S107: No), the valve opening degree adjusting means 30 opens the valve. After determining that the temperature difference Δt1 is excessive through the degree setting unit 34 and transmitting an opening degree expansion command to the electronic expansion valve 13 (step S108), the procedure is returned. When an opening degree expansion command is given to the electronic expansion valve 13, the electronic expansion valve 13 performs an opening degree expansion operation. And if the electronic expansion valve 13 enlarges an opening degree, the temperature difference (DELTA) t1 will become small gradually, and the temperature difference (DELTA) t1 will change so that it may fall below upper limit threshold value U [K] before long.

  On the other hand, when it is determined that the temperature difference Δt1 is equal to or lower than the upper limit threshold U [K] (Δt1 ≦ U) (step S107: Yes), the valve opening degree adjusting means 30 determines that the temperature difference Δt1 is appropriate. In order to maintain the opening degree of the electronic expansion valve 13, the opening degree enlargement command and the opening degree reduction instruction are not transmitted, and the procedure is returned as it is.

  FIG. 5 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 threshold L [K], the valve opening adjusting means 30 determines that the liquid is back and reduces the opening of the electronic expansion valve 13 through the valve opening setting unit 34. When the temperature difference Δt1 is larger than the upper limit threshold 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 less than the lower limit threshold L. If it is equal to or greater than [K] and equal to or smaller than the upper threshold U [K], it is determined that the temperature difference Δt1 is 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.

  The valve opening degree adjusting means 30 provided in the refrigerant flow control device also performs error detection based on the refrigerant temperatures detected by the first temperature sensor 21, the second temperature sensor 22, and the third temperature sensor 23. is there. Hereinafter, the error detection process performed by the valve opening degree adjusting means 30 will be described with reference to FIG.

  When the first cycle time stored in advance in the storage unit 25 has elapsed under the operating state of the cooling device (step S201: Yes), the valve opening degree adjusting means 30 is set to the first temperature sensor 21 and the second temperature sensor 21. Respective refrigerant temperatures are detected through the temperature sensor 22 and the third temperature sensor 23 (step S202), and then the upstream temperature difference X calculated by the upstream temperature difference calculation unit 36 by the valve opening setting unit 34 and the first threshold value. Compare the magnitude with α1, compare the magnitude of the downstream temperature difference Y calculated by the downstream temperature difference calculator 37 with the second threshold value α2, determine that the upstream temperature difference X is greater than the first threshold value α1, and It is determined whether or not the downstream temperature difference Y is greater than the second threshold value α2 (X> α1 and Y> α2) (step S203).

  When the valve opening degree adjusting means 30 does not satisfy the above condition, that is, when the upstream temperature difference X is not more than the first threshold value α1 (X ≦ α1), or the downstream temperature difference Y is not more than the second threshold value α2 ( If Y ≦ α2) (step S203: No), it is determined that the second temperature sensor 22 is not detached from the evaporation pipe 12a through the valve opening setting unit 34, and the procedure is returned as it is. End the process.

  On the other hand, when the valve opening degree adjusting means 30 satisfies the above condition, that is, the upstream temperature difference X is larger than the first threshold value α1, and the downstream temperature difference Y is larger than the second threshold value α2 (X> α1, and Y > Α2) (step S203: Yes), the opening degree adjusting process of the electronic expansion valve 13 is not functioning because the second temperature sensor 22 is removed from the evaporation pipe 12a through the valve opening degree setting unit 34. It is determined that there is a possibility, and the process proceeds to step S204.

  Hereinafter, the reason for this operation will be described in detail. In the cooling device, the magnitude relationship between the upstream temperature difference X and the first threshold value α1 and the magnitude relationship between the downstream temperature difference Y and the second threshold value α2 are as follows according to the position of the evaporation completion point. Exists.

  First, as shown in FIG. 2A, in a state where the evaporation completion point is located upstream from the installation position of the second temperature sensor 22, the intermediate temperature T2 is higher than the inlet side temperature T1 (T2>). T1) and the intermediate temperature T2 is lower than the outlet side temperature T3 (T2 <T3). That is, the upstream temperature difference X is larger than the first threshold value α1 (T2−T1 = X> α1 = 0), and the downstream temperature difference Y is smaller than the second threshold value α2 (T2−T3 = Y <α2 = 0). .

  Next, as shown in FIGS. 2B to 2D, the evaporation completion point is located downstream of the installation position of the second temperature sensor 22 and upstream of the installation position of the third temperature sensor 23. In this state, the intermediate temperature T2 is lower than the inlet side temperature T1 (T2 <T1), and the intermediate temperature T2 is lower than the outlet side temperature T3 (T2 <T3). That is, the upstream temperature difference X is smaller than the first threshold value α1 (T2−T1 = X <α1 = 0), and the downstream temperature difference Y is smaller than the second threshold value α2 (T2−T3 = Y <α2 = 0). .

  Next, although not shown in the drawing, in a state where the evaporation completion point is located downstream of the installation position of the third temperature sensor 23, the refrigerant gradually goes down as the refrigerant temperature goes downstream due to the pressure loss generated in the evaporation pipe 12a. Therefore, the intermediate temperature T2 is lower than the inlet side temperature T1 (T2 <T1), and the intermediate temperature T2 is higher than the outlet side temperature T3 (T2> T3). That is, the upstream temperature difference X is smaller than the first threshold value α1 (T2−T1 = X <α1 = 0), and the downstream temperature difference Y is larger than the second threshold value α2 (T2−T3 = Y> α2 = 0). .

  As described above, in a state where the cooling device is operating, the intermediate temperature T2 is higher than the inlet side temperature T1 (T2> T1) and the intermediate temperature T2 is higher than the outlet side temperature T3 (T2> T3). That is, the upstream temperature difference X is larger than the first threshold value α1 (T2−T1 = X> α1 = 0), and the downstream temperature difference Y is larger than the second threshold value α2 (T2−T3 = Y> α2 = 0). There is no case. When the second temperature sensor 22 is detached from the evaporation pipe 12a, the second temperature sensor 22 detects the air temperature around the evaporation pipe 12a, and detects a temperature higher than the normal temperature. Therefore, the intermediate temperature T2 is higher than the inlet side temperature T1 (T2> T1) and the intermediate temperature T2 is higher than the outlet side temperature T3 (T2> T3), that is, the upstream temperature difference X is the first threshold value. A state occurs where the value is larger than α1 (T2−T1 = X> α1 = 0) and the downstream temperature difference Y is larger than the second threshold value α2 (T2−T3 = Y> α2 = 0). Based on the above principle, when the valve opening degree adjusting means 30 detects the above-described relationship from the detection results of the three temperature sensors 21, 22, and 23, the second opening temperature is set from the evaporation pipe 12 a through the valve opening degree setting unit 34. It is determined that the sensor 22 may have come off.

  Next, the valve opening degree adjusting means 30 temporarily has the intermediate temperature T2 higher than the inlet side temperature T1 (T2> T1), although the second temperature sensor 22 is not detached from the evaporation pipe 12a. When the intermediate temperature T2 is higher than the outlet side temperature T3 (T2> T3), in order to prevent erroneous output of error, the process waits until the second cycle time elapses (step S204), and then proceeds to step S205. .

  Next, the valve opening degree adjusting means 30 again compares the magnitude of the upstream temperature difference X calculated by the upstream temperature difference calculating unit 36 with the first threshold value α1 through the valve opening setting unit 34 and the downstream side. The downstream temperature difference Y calculated by the side temperature difference calculation unit 37 is compared with the second threshold value α2, the upstream temperature difference X is larger than the first threshold value α1, and the downstream temperature difference Y is the second threshold value α2. It is determined whether or not the state is larger (X> α1 and Y> α2) (step S205).

  When the valve opening degree adjusting means 30 does not satisfy the above condition, that is, when the upstream temperature difference X is not more than the first threshold value α1 (X ≦ α1), or the downstream temperature difference Y is not more than the second threshold value α2 ( If Y ≦ α2) (step S205: No), it is determined that the second temperature sensor 22 is not detached from the evaporation pipe 12a through the valve opening setting unit 34, and the procedure is returned as it is. End the process.

  On the other hand, when the valve opening degree adjusting means 30 satisfies the above condition, that is, the upstream temperature difference X is larger than the first threshold value α1, and the downstream temperature difference Y is larger than the second threshold value α2 (X> α1, and Y > Α2) (step S205: Yes), it is determined that the second temperature sensor 22 has been removed from the evaporation pipe 12a through the valve opening setting unit 34, and the process proceeds to step S206.

  Based on the determination, the valve opening degree adjusting means 30 transmits an error display command to the display device 40 through the valve opening degree setting unit 34 (step S206), and then returns the procedure and ends the current process. When the error display command is given, the display 40 displays that the second temperature sensor 22 has been removed from the evaporation pipe 12a.

  According to the refrigerant flow control device according to this embodiment, when the temperature difference Δt1 obtained by subtracting the intermediate temperature T2 from the outlet side temperature T3 is smaller than the preset lower threshold L, the valve opening degree adjusting means 30 is electronic. Since the opening degree of the expansion valve 13 is reduced, the occurrence of liquid back can be prevented. Moreover, when the temperature difference Δt1 is larger than the preset upper limit threshold U, the valve opening degree adjusting means 30 increases the opening degree of the electronic expansion valve, so that it is possible to prevent the cooling efficiency from being lowered.

  In addition, according to this refrigerant flow rate control device, when the inlet side temperature T1 is lower than the intermediate temperature T2, the valve opening degree adjusting means 30 expands the opening degree of the electronic expansion valve 13, so that it occurs in the evaporation pipe 12a. It is possible to prevent the cooling efficiency from being lowered in consideration of the pressure loss.

  Further, in a state where the cooling device is operating, there is no situation where the intermediate temperature T2 is higher than the inlet side temperature T1 and the intermediate temperature T2 is higher than the outlet side temperature T3, and the second temperature sensor 22 is connected from the evaporation pipe 12a. The refrigerant flow rate control device is based on the fact that the upstream temperature difference X is larger than the first threshold value α1 and the downstream temperature difference Y is larger than the second threshold value α2 based on the fact that the above-mentioned situation occurs only when the deviation occurs. Is provided with a valve opening degree adjusting means 30 for performing error output. According to such a refrigerant flow control device, since it can be detected that the intermediate temperature T2 is higher than the inlet side temperature T1 and the intermediate temperature T2 is higher than the outlet side temperature T3, the second temperature sensor is connected from the evaporation pipe 12a. It can be detected that 22 is disconnected. Therefore, the second temperature sensor 22 among the three temperature sensors 21, 22, and 23 does not need to be provided with a drop-off detection sensor that detects that the second temperature sensor 22 is detached from the evaporation pipe 12 a. Can be prevented as much as possible.

  In the above-described embodiment, 0 is set as the first threshold value α1, and the upstream temperature difference X obtained by subtracting the inlet side temperature T1 from the intermediate temperature T2 is higher than the first threshold value α1 (T2−T1 = X>). It has been described that the valve opening degree adjusting means 30 determines that the second temperature sensor 22 may be detached from the evaporation pipe 12a on the condition that α1 = 0). However, the present invention is not limited to this. Considering the error of the first temperature sensor 21 and the second temperature sensor 22, a number greater than 0 is set to the first threshold value α1 ′ (α1 ′ = α1 + ΔTX1: where ΔTX1 is 0 The valve opening degree adjusting means 30 is set from the evaporating pipe 12a to the first temperature on the condition that the upstream temperature difference X is larger than the first threshold value α1 ′ (T2−T1 = X <α1 ′). You may judge that there exists a possibility that 2 temperature sensor 22 may remove | deviate. If the first threshold value α1 ′ is set in this way, the intermediate temperature T2 is temporarily higher than the inlet side temperature T1 even though the second temperature sensor 22 is not detached from the evaporation pipe 12a (T2>). T1) It is possible to prevent erroneous output of errors. However, when the first threshold value α1 ′ is set to a positive number larger than 0, it is preferable that the first threshold value α1 ′ is as small as possible in order to prevent a situation where error output is not performed. For example, 1 is set as the first threshold value α1 ′.

  In the above-described embodiment, 0 is set as the second threshold value α2, and the downstream temperature difference Y obtained by subtracting the outlet side temperature T3 from the intermediate temperature T2 is higher than the second threshold value α2 (T2−T3 = Y>). It has been described that the valve opening degree adjusting means 30 determines that the second temperature sensor 22 may be detached from the evaporation pipe 12a on the condition that α2 = 0). However, the present invention is not limited to this, and in consideration of errors of the second temperature sensor 22 and the third temperature sensor 23, a number larger than 0 is set to a second threshold value α2 ′ (α2 ′ = α2 + ΔTX2: where ΔTX2 is 0 The valve opening degree adjusting means 30 is set from the evaporating pipe 12a to the second temperature on the condition that the downstream temperature difference Y is larger than the second threshold value α2 ′ (T2−T3 = Y <α2 ′). You may judge that there exists a possibility that 2 temperature sensor 22 may remove | deviate. If the second threshold value α2 ′ is set in this manner, the intermediate temperature T2 is temporarily higher than the outlet side temperature T3 (T2>) even though the second temperature sensor 22 is not detached from the evaporation pipe 12a. T3) It is possible to prevent erroneous output of errors. However, when the second threshold value α2 ′ is set to a positive number larger than 0, it is preferable that the second threshold value α2 ′ is as small as possible in order to prevent a situation where error output is not performed. For example, 1 is set as the second threshold value α2 ′.

  Further, in the above-described 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.

  In the above-described embodiment, the initial value of the upper limit threshold U of the temperature difference Δt1 is set to 5 [K]. However, the present invention is not limited to this, and the initial value of the upper limit threshold U of the temperature difference Δt1 may be arbitrarily set as long as it is larger than the lower limit threshold L. However, as described above, when the temperature difference Δt1 is large, the cooling efficiency is lowered. Therefore, a value larger than the lower limit threshold L is preferably as small as possible.

  Further, in the above-described embodiment, the first temperature sensor 21 is attached to the inlet portion of the evaporation pipe 12a, and the second temperature sensor 22 is attached to an intermediate position between the inlet portion and the outlet portion of the evaporation pipe 12a to evaporate. In the above description, the third temperature sensor 23 is attached to the outlet of the tube 12a. However, the attachment positions of the temperature sensors 21, 22, and 23 are not limited to the above positions. For example, the first temperature sensor 21 may be attached to the downstream side of the inlet part of the evaporation pipe 12a, or the third temperature sensor 23 may be attached to the upstream side of the outlet part of the evaporation pipe 12a. However, it is necessary to attach the second temperature sensor 22 on the downstream side of the first temperature sensor 21 and attach the third temperature sensor 23 on the downstream side of the second temperature sensor 22. Moreover, it is preferable that the 2nd temperature sensor 22 is attached to the vicinity of the exit part of the evaporation pipe | tube 12a.

  In the embodiment described above, the valve opening degree adjusting means 30 that adjusts the opening degree of the electronic expansion valve 13 according to the detection results of the temperature sensors 21, 22, 23 is detected by the temperature sensors 21, 22, 23. As described above, the second temperature sensor 22 is detected to be disconnected from the evaporation pipe 12a according to the result, and an error is output. However, the present invention is not limited thereto, and the valve opening degree adjusting means 30 for adjusting the opening degree of the electronic expansion valve 13 in accordance with the detection results of the temperature sensors 21, 22, 23, and the detection results of the temperature sensors 21, 22, 23. Accordingly, an error output means for detecting that the second temperature sensor 22 is detached from the evaporation pipe 12a and outputting an error may be provided inside the control means 19 separately.

  Further, in the above-described embodiment, when the valve opening degree setting unit 34 determines that the second temperature sensor 22 is disconnected from the evaporation pipe 12a, the valve opening degree setting unit 34 instructs the display unit 40 to display an error. Is transmitted and the fact that the second temperature sensor 22 is disengaged from the evaporation pipe 12a is displayed on the display device 40 to notify the user. However, the means for notifying the user that the second temperature sensor 22 is detached from the evaporation pipe 12a is not limited to that through vision. For example, when the valve opening setting unit 34 determines that the second temperature sensor 22 is disconnected from the evaporation pipe 12a, the valve opening setting unit 34 transmits an error display command to the buzzer, and the second temperature sensor 22 The user may be notified by generating a warning sound that the evaporator 12a is detached.

  In the above-described embodiment, the first condition is that the upstream temperature difference X is higher than the first threshold and the downstream temperature difference Y is higher than the second threshold, and the state continues for a certain period of time. In the above description, the second condition is set to perform error output when the first condition and the second condition are satisfied. This is because the intermediate temperature T2 is temporarily higher than the inlet side temperature T1 (T2> T1) and the intermediate temperature T2 is equal to the outlet side temperature T3 although the second temperature sensor 22 is not detached from the evaporation pipe 12a. This is for the purpose of preventing an erroneous error output when the value is higher. Therefore, the present invention is not limited to the one that performs error output when these two conditions are satisfied, and may perform error output when only the first condition is satisfied.

It is explanatory drawing which shows the structure of the cooling device to which the refrigerant | coolant flow control apparatus which is embodiment 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 graph explaining the temperature distribution of the refrigerant | coolant shown in FIG. 2 in detail. 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. 6 is a chart showing a relationship between determination of a temperature difference Δt1 performed by the valve opening degree adjusting means and control performed by 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 error detection process which the valve opening degree adjustment means with which the refrigerant | coolant flow control apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Container 11 Open showcase 12 Evaporator 12a Evaporating pipe (refrigerant flow path)
DESCRIPTION OF SYMBOLS 13 Electronic expansion valve 14 Condenser 15 Compressor 16 Refrigerant supply pipe 17 Blower fan 19 Control means 21 1st temperature sensor (inlet side temperature sensor)
22 Second temperature sensor (intermediate temperature sensor)
23 Third temperature sensor (outlet temperature sensor)
25 Storage Unit 30 Valve Opening Adjustment Unit 31 Temperature Difference Calculation Unit 32 Comparison Unit 34 Valve Opening Setting Unit (Error Output Unit)
36 upstream temperature difference calculation unit 37 downstream temperature difference calculation unit 40 indicator L lower limit threshold T1 inlet side temperature T2 intermediate temperature T3 outlet side temperature U upper limit threshold X upstream temperature difference Y downstream temperature difference ΔT pressure loss Δt1 temperature difference (Superheat)
α1 First threshold α2 Second threshold

Claims (2)

An electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening;
Three temperature sensors installed at different distances from the inlet portion between the inlet portion and the outlet portion of the refrigerant flow passage in the evaporator;
When the inlet side temperature detected by the inlet side temperature sensor installed on the most upstream side is lower than the intermediate temperature detected by the intermediate temperature sensor installed on the downstream side of the inlet side temperature sensor, the opening degree of the electronic expansion valve is set. When the temperature difference obtained by subtracting the intermediate temperature from the outlet temperature detected by the outlet temperature sensor installed on the downstream side of the intermediate temperature sensor is smaller than a preset lower threshold, the electronic expansion valve is opened. 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,
An upstream temperature difference obtained by subtracting the inlet side temperature from the intermediate temperature is calculated, and a downstream temperature difference obtained by subtracting the outlet side temperature from the intermediate temperature is calculated, and the upstream temperature difference and a preset first temperature difference are calculated. And comparing the downstream temperature difference with a preset second threshold, the upstream temperature difference is greater than the first threshold, and the downstream temperature difference is greater than the second threshold. And an error output means for outputting an error on condition that it is large. An electronic expansion valve that controls the amount of refrigerant flowing into the evaporator according to the opening;
Three temperature sensors installed at different distances from the inlet portion between the inlet portion and the outlet portion of the refrigerant flow passage in the evaporator;
When the inlet side temperature detected by the inlet side temperature sensor installed on the most upstream side is lower than the intermediate temperature detected by the intermediate temperature sensor installed on the downstream side of the inlet side temperature sensor, the opening degree of the electronic expansion valve is set. When the temperature difference obtained by subtracting the intermediate temperature from the outlet temperature detected by the outlet temperature sensor installed on the downstream side of the intermediate temperature sensor is smaller than a preset lower threshold, the electronic expansion valve is opened. 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,
An upstream temperature difference obtained by subtracting the inlet side temperature from the intermediate temperature is calculated, and a downstream temperature difference obtained by subtracting the outlet side temperature from the intermediate temperature is calculated, and the upstream temperature difference and a preset first temperature difference are calculated. And comparing the downstream temperature difference with a preset second threshold, the upstream temperature difference is greater than the first threshold, and the downstream temperature difference is greater than the second threshold. A refrigerant flow rate control device comprising: error output means for outputting an error when large.

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