Cooling mechanism

Abstract

The invention provides a cooling mechanism which can prevent liquid from being compressed. A controller of the cooling mechanism sets the value of a first temperature sensor or a second temperature sensor to a set temperature, and controls the CO2 refrigerant to follow a path defined by a set pressure value and a set temperature around a critical point defined by a critical temperature 31.1 DEG C and a critical pressure 7.38 MPa. The opening degree of the variable expansion valve and the rotation speed of the compressor are controlled.

Description

Technical Field

[0001] The present invention relates to a cooling mechanism for cooling a processing aid fluid used in a processing device. Background Art

[0002] A wafer having multiple devices such as IC and LSI formed on the front side is divided by a plurality of intersecting predetermined dividing lines. After being ground by a grinding device on the back side to a specified thickness, it is divided into individual device chips by a cutting device or a laser processing device. The divided device chips are used in electronic devices such as mobile phones and personal computers.

[0003] When processing a wafer, if a spindle unit that is a grinding device or a cutting device and on which a processing tool is mounted generates heat and expands, high-precision grinding or cutting cannot be performed. Therefore, a temperature control device is used to control the temperature of the spindle unit to be constant (for example, refer to Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-40396

[0005] The temperature control device described in the above-mentioned Patent Document 1 is a type of device that uses CO2 as a refrigerant and can achieve high cooling efficiency. However, when the water temperature of the processing aid fluid (disposable processing water including cutting water, etc.) used in the processing device is set low, there is a possibility that the refrigerant sucked into the compressor is not completely vaporized and liquid compression occurs, which may shorten the life of the compressor. Summary of the invention

[0006] Therefore, an object of the present invention is to provide a cooling mechanism capable of preventing liquid compression.

[0007] According to one aspect of the present invention, a cooling mechanism is provided, which cools a processing aid liquid used in a processing device, wherein the cooling mechanism comprises: a controller; a compressor, which compresses a CO2 refrigerant; a water-cooled gas cooler, which cools the CO2 refrigerant with compression heat compressed by the compressor; an internal heat exchanger, into which the cooled CO2 refrigerant is fed; an evaporator, which vaporizes the CO2 refrigerant sent from the internal heat exchanger to generate vaporization heat, thereby cooling the processing aid liquid used in the processing device; a first path, which connects the compressor to the water-cooled gas cooler; and a second path, which connects the water-cooled gas cooler to the evaporator. a third path connecting the evaporator and the compressor; a fourth path introducing industrial water to the water-cooled gas cooler, the fourth path having a water control valve; and a bypass path connected via a first connection portion connected to the first path and a second connection portion connected to the second path, the bypass path having a variable bypass valve, the internal heat exchanger being arranged across the second path and the third path in such a manner that the CO2 refrigerant delivered by the evaporator takes heat from the CO2 refrigerant delivered by the water-cooled gas cooler, and a variable expansion valve for adjusting the flow rate of the cooled CO2 refrigerant is arranged on the second path. A first pressure sensor for measuring the pressure of the CO2 refrigerant is provided between the exchanger and the second connecting portion, and on any of the second and third paths between the variable expansion valve and the compressor. A second pressure sensor for measuring the pressure of the CO2 refrigerant compressed by the compressor is provided on any of the first and second paths between the compressor and the variable expansion valve. The cooling mechanism is provided with: a first temperature sensor for measuring the temperature of the processing aid liquid used in the processing device flowing out of the evaporator; and a second temperature sensor for measuring the temperature of the processing aid liquid flowing into the evaporator. a third temperature sensor for measuring the temperature of the industrial water flowing into the water-cooled gas cooler; a fourth temperature sensor for measuring the temperature of the CO2 refrigerant sent from the compressor; a fifth temperature sensor for measuring the temperature of the CO2 refrigerant sent from the water-cooled gas cooler; a sixth temperature sensor provided as needed for measuring the temperature of the CO2 refrigerant sent from the internal heat exchanger; a seventh temperature sensor provided as needed for measuring the temperature of the CO2 refrigerant sent from the evaporator which is the same temperature as the temperature of the CO2 refrigerant sent from the variable expansion valve;and an eighth temperature sensor, which measures the temperature of the CO2 refrigerant fed into the compressor, the controller having a setting unit, the setting unit setting at least a first pressure value to be detected by the first pressure sensor, a second pressure value to be detected by the second pressure sensor, a first temperature to be detected by the first temperature sensor or a second temperature to be detected by the second temperature sensor, a fourth temperature to be detected by the fourth temperature sensor, a fifth temperature to be detected by the fifth temperature sensor, and an eighth temperature to be detected by the eighth temperature sensor, so that the CO2 refrigerant follows a path defined by the set pressure value and temperature around a critical point, and the opening of the variable expansion valve and the rotation speed of the compressor are controlled in such a manner that the value of the first temperature sensor or the second temperature sensor becomes the set temperature, wherein the critical point is determined by a critical temperature of 31.1°C and a critical pressure of 7.38MPa. ;

[0008] Preferably, the controller reduces the opening of the variable expansion valve to reduce the flow rate of the CO2 refrigerant flowing in the evaporator when reducing the cooling amount of the processing aid fluid used in the processing device, and concomitantly increases the opening of the variable bypass valve in the bypass path to increase the flow rate of the CO2 refrigerant flowing into the evaporator to ensure that the compressor does not reach the lower limit value.

[0009] Preferably, the controller increases the opening of the variable expansion valve and the rotation speed of the compressor while increasing the cooling amount of the processing aid fluid used in the processing device, thereby increasing the flow rate of the CO2 refrigerant flowing in the evaporator. Concomitantly, the liquid CO2 remaining in the CO2 refrigerant sent from the evaporator is vaporized in the internal heat exchanger, thereby reducing the burden on the compressor.

[0010] Preferably, the controller adjusts the opening of the water control valve according to the temperature of the industrial water detected by the third temperature sensor, thereby adjusting the flow rate of the industrial water introduced into the water-cooled gas cooler and controlling the cooling of the CO 2 refrigerant.

[0011] Preferably, the controller increases the value of the second pressure sensor by reducing the opening of the variable expansion valve, and reduces the value of the second pressure sensor by increasing the opening of the variable expansion valve, thereby adjusting the value of the second pressure sensor to the set pressure value and controlling the cooling efficiency, wherein the cooling efficiency is cooling capacity / compression work.

[0012] Preferably, the outlet of the compressor is set to point A, the outlet of the water-cooled gas cooler is set to point B, the outlet of the second path in the internal heat exchanger is set to point C, the outlet of the variable expansion valve is set to point D, the outlet of the evaporator is set to point E, the outlet of the third path in the internal heat exchanger is set to point F, the temperature at point A is set to TA, the pressure is set to PA, the specific enthalpy is set to EA, the temperature at point B is set to TB, the pressure is set to PB, the specific enthalpy is set to EB, the temperature at point C is set to TC, the pressure is set to PC, the specific enthalpy is set to EC, the temperature at point D is set to TD, the pressure is set to PD, the specific enthalpy is set to ED, the temperature at point E is set to TE, the pressure is set to PE, and the specific enthalpy is set to EB. The enthalpy is set to EE, the temperature at point F is set to TF, the pressure is set to PF, and the specific enthalpy is set to EF. In this case, the CO2 refrigerant sent from point F to the compressor is compressed by the compressor and reaches the point A exceeding the critical point, the temperature changes from TF to TA, the pressure changes from PF to PA, and the specific enthalpy changes from EF to EA. The CO2 refrigerant sent from point A to the water-cooled gas cooler is cooled by the water-cooled gas cooler and reaches the point B, the temperature changes from TA to TB, the pressure remains unchanged, that is, PA=PB, the specific enthalpy changes from EA to EB, the temperature difference between TA and TB and the specific enthalpy difference between EA and EB are discarded to the outside by the water-cooled gas cooler, the pressure PB and the temperature TB exceed the critical point, and CO2 refrigeration does not occur. The CO2 refrigerant is liquefied. The CO2 refrigerant fed from point B into the internal heat exchanger takes heat from the CO2 refrigerant fed from the evaporator and reaches point C. The temperature changes from TB to TC, the pressure remains unchanged, that is, PB=PC, and the specific enthalpy changes from EB to EC. The temperature TC is lower than the critical point. A part of the CO2 refrigerant is liquefied. The CO2 refrigerant fed from point C into the variable expansion valve is decompressed by the variable expansion valve and reaches point D. The temperature changes from TC to TD, the pressure changes from PC to PD, the specific enthalpy remains unchanged, that is, EC=ED. The CO2 refrigerant becomes a state of gas and liquid mixed. The CO2 refrigerant fed from point D into the evaporator takes energy from the processing aid fluid through the evaporator and reaches point E. The temperature and pressure remain unchanged, that is, TD=TE, PD=PE, the specific enthalpy changes from ED to EE, and the point E approaches the saturated vapor line passing through the critical point. The CO2 refrigerant becomes a gas. The CO2 refrigerant sent into the internal heat exchanger from the point E takes heat from the CO2 refrigerant sent into the internal heat exchanger from the point B. Although there is residual liquid, it becomes a gas and reaches the point F. The temperature changes from TE to TF, and the pressure remains unchanged, that is, PE=PF. The specific enthalpy changes from EE to EF, and reaches the point A. The absolute value of the difference between EB and EC and the absolute value of the difference between EE and EF are equal. The controller controls the temperature, pressure and specific enthalpy in a manner such that the cooling efficiency = (ED-EE) / (EF-EA) is maximized, wherein the cooling efficiency is cooling capacity / compression work.

[0013] Preferably, the temperature TA at point A is detected by the fourth temperature sensor, the temperature TB at point B is detected by the fifth temperature sensor, the temperature TC at point C is detected by the sixth temperature sensor, the temperature TD at point D is detected by the seventh temperature sensor, the temperature TE at point E is detected by the seventh temperature sensor, the temperature TF at point F is detected by the eighth temperature sensor, the pressure PA at point A is detected by the second pressure sensor, the pressure PB at point B is detected by the second pressure sensor, the pressure PC at point C is detected by the second pressure sensor, the pressure PD at point D is detected by the first pressure sensor, the pressure PE at point E is detected by the first pressure sensor, and the pressure PF at point F is detected by the first pressure sensor. The specific enthalpy EA at point A is detected based on the pressure-specific enthalpy diagram, the specific enthalpy EB at point B is detected based on the pressure-specific enthalpy diagram, the specific enthalpy EC at point C is detected based on the pressure-specific enthalpy diagram, the specific enthalpy ED at point D is detected based on the pressure-specific enthalpy diagram, the specific enthalpy EE at point E is calculated by EF-(EB-EC), and the specific enthalpy EF at point F is detected based on the pressure-specific enthalpy diagram. When the controller calculates the cooling efficiency through the mathematical formula of cooling efficiency = (ED-EE) / (EF-EA), according to EC = ED and EE = EF-(EB-EC), ED-EE = EC-{EF-(EB-EC)} = EB-EF is obtained, so that the difference (EB-EF) between the specific enthalpy EB and the specific enthalpy EF is increased, thereby improving the cooling capacity and cooling efficiency, wherein the cooling efficiency is cooling capacity / compression work.

[0014] The sixth temperature sensor and the seventh temperature sensor may be omitted.

[0015] According to the cooling mechanism of the present invention, in such a way that the value of the first temperature sensor or the second temperature sensor becomes a set temperature, the CO2 refrigerant follows a path defined by the set pressure value and temperature around a critical point determined by the critical temperature of 31.1°C and the critical pressure of 7.38MPa, thereby controlling the opening of the variable expansion valve and the speed of the compressor, thereby preventing liquid compression. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a circuit diagram of the cooling mechanism of the present invention.

[0017] Figure 2 is the pressure-specific enthalpy diagram of CO2.

[0018] Figure 3 It is shown Figure 1 A schematic diagram of an example of the configuration of the cooling mechanism shown.

[0019] Figure 4 This is a graph showing an example of the speed of the compressor when the operation is resumed.

[0020] Description of symbols

[0021] 2: cooling mechanism; 4: controller; 4a: setting unit; 4b: control unit; 6: compressor; 8: water-cooled gas cooler; 10: internal heat exchanger; 12: evaporator; 14: first path; 16: second path; 18: third path; 20: water control valve; 22: fourth path; 24: first connecting part; 26: second connecting part; 28: variable bypass valve; 30: bypass path; 32: variable expansion valve; 34: first pressure sensor; 36: second pressure sensor; 38: first temperature sensor; 40: second temperature sensor; 42: third temperature sensor; 44: fourth temperature sensor; 46: fifth temperature sensor; 48: sixth temperature sensor; 50: seventh temperature sensor; 52: eighth temperature sensor. DETAILED DESCRIPTION

[0022] Hereinafter, preferred embodiments of the cooling mechanism of the present invention will be described with reference to the drawings.

[0023] (Cooling mechanism 2)

[0024] exist Figure 1 2 shows a cooling mechanism 2 for cooling a processing aid liquid used in a processing device using a CO2 refrigerant. The cooling mechanism 2 includes a controller 4, a compressor 6, a water-cooled gas cooler 8, an internal heat exchanger 10, and an evaporator 12.

[0025] (Controller 4)

[0026] The controller 4 is composed of a computer having a processor and a memory. The controller 4 of this embodiment has a setting unit 4a and a control unit 4b. The setting unit 4a sets the pressure / temperature of the CO2 refrigerant according to an instruction input by an operator (for example, the temperature of the processing aid liquid used in the processing device). The control unit 4b controls the opening of the variable expansion valve 32, the rotation speed of the compressor 6, etc., so that the actual temperature of the processing aid liquid becomes the set temperature (the temperature input by the operator). The control content of the control unit 4b will be described in detail later.

[0027] (Compressor 6)

[0028] The compressor 6 compresses the CO2 refrigerant circulating in the cooling mechanism 2. Figure 1As shown, an inverter 6b is provided on the motor 6a driving the compressor 6. The inverter 6b changes the frequency of the power supplied to the motor 6a within a predetermined range (for example, 20 Hz to 120 Hz). Thus, the rotation speed of the motor 6a is changed, and the rotation speed of the compressor 6 is changed within the range of the allowable rotation speed (between the lower limit and the upper limit). In addition, the inverter 6b is electrically connected to the controller 4 and is controlled by the control unit 4b of the controller 4.

[0029] (Water-cooled gas cooler 8)

[0030] The water-cooled gas cooler 8 cools the CO2 refrigerant with compression heat compressed by the compressor 6. Figure 1 As shown, industrial water for cooling the CO2 refrigerant is introduced into the water-cooled gas cooler 8. Figure 3 As shown, a refrigerant passage 8a through which CO2 refrigerant flows and a water passage 8b through which industrial water flows are formed inside the water-cooled gas cooler 8. In the water-cooled gas cooler 8, heat is exchanged between the CO2 refrigerant in the refrigerant passage 8a and the industrial water in the water passage 8b, thereby cooling the CO2 refrigerant using the industrial water.

[0031] (Internal heat exchanger 10)

[0032] The CO2 refrigerant cooled by the water-cooled gas cooler 8 is sent to the internal heat exchanger 10. Figure 3 As shown, a first passage 10a through which the CO2 refrigerant cooled by the water-cooled gas cooler 8 passes and a second passage 10b through which the CO2 refrigerant after the processing aid fluid is cooled in the evaporator 12 are formed in the internal heat exchanger 10. In addition, in the internal heat exchanger 10, heat exchange is performed between the CO2 refrigerant in the first passage 10a and the CO2 refrigerant in the second passage 10b. As a result, the CO2 refrigerant in the second passage 10b sent out by the evaporator 12 takes away heat from the CO2 refrigerant in the first passage 10a sent out by the water-cooled gas cooler 8. As a result, all the CO2 refrigerant remaining in liquid becomes gas (details will be described later).

[0033] (Evaporator 12)

[0034] The evaporator 12 vaporizes the CO2 refrigerant sent from the internal heat exchanger 10 to generate vaporization heat, and uses the generated vaporization heat to cool the processing aid liquid used in the processing device. Figure 3As shown, a refrigerant passage 12a through which CO2 refrigerant flows and a processing aid liquid passage 12b through which processing aid liquid flows are provided inside the evaporator 12. In addition, in the evaporator 12, heat exchange is performed between the CO2 refrigerant in the refrigerant passage 12a and the processing aid liquid in the processing aid liquid passage 12b, so that the processing aid liquid is cooled by utilizing the vaporization heat of the CO2 refrigerant.

[0035] (First to fourth paths 14, 16, 18, 22, bypass path 30)

[0036] Reference Figure 1 Continuing the description, the cooling mechanism 2 further includes: a first path 14 connecting the compressor 6 and the water-cooled gas cooler 8; a second path 16 connecting the water-cooled gas cooler 8 and the evaporator 12; a third path 18 connecting the evaporator 12 and the compressor 6; a fourth path 22 for introducing industrial water to the water-cooled gas cooler 8 and having a water control valve 20; and a bypass path 30 connected by a first connection portion 24 connected to the first path 14 and a second connection portion 26 connected to the second path 16 and having a variable bypass valve 28. In the second path 16, a variable expansion valve 32 for adjusting the flow rate of the cooled CO2 refrigerant is disposed between the internal heat exchanger 10 and the second connection portion 26. In addition, the internal heat exchanger 10 is disposed across the second path 16 and the third path 18.

[0037] (Water control valve 20, variable bypass valve 28, variable expansion valve 32)

[0038] like Figure 1 As shown, the water control valve 20, the variable bypass valve 28 and the variable expansion valve 32 are respectively provided with motors 20a, 28a, 32a for adjusting the opening. The motors 20a, 28a, 32a are all electrically connected to the controller 4. Moreover, the opening of each of the water control valve 20, the variable bypass valve 28 and the variable expansion valve 32 is adjusted by the motors 20a, 28a, 32a according to the instruction from the control unit 4b of the controller 4.

[0039] The CO2 refrigerant of the cooling mechanism 2 passes through the first to third paths 14, 16, and 18 in sequence, and circulates in the order of the compressor 6, the water-cooled gas cooler 8, the internal heat exchanger 10, the evaporator 12, and the internal heat exchanger 10. That is, in the present embodiment, the CO2 refrigerant sent from the compressor 6 passes through the internal heat exchanger 10 twice in principle before returning to the compressor 6 again. Specifically, the CO2 refrigerant flowing out of the water-cooled gas cooler 8 passes through the internal heat exchanger 10, and then passes through the evaporator 12 and then passes through the internal heat exchanger 10 again.

[0040] However, when the variable bypass valve 28 is open, a part of the CO 2 refrigerant compressed by the compressor 6 is sent to the evaporator 12 through the bypass path 30 without passing through the water-cooled gas cooler 8 and the internal heat exchanger 10 .

[0041] (Pressure Sensor)

[0042] The cooling mechanism 2 is provided with first and second pressure sensors 34 and 36 as sensors for measuring the pressure of the CO 2 refrigerant. The values ​​measured by the first and second pressure sensors 34 and 36 are sent to the controller 4 .

[0043] (First pressure sensor 34)

[0044] The first pressure sensor 34 measures the pressure of the CO2 refrigerant expanded by the variable expansion valve 32. The first pressure sensor 34 can be disposed in any of the second path 16 and the third path 18 between the variable expansion valve 32 and the compressor 6. In the present embodiment, the first pressure sensor 34 is disposed between the internal heat exchanger 10 and the compressor 6 in the third path 18.

[0045] (Second pressure sensor 36)

[0046] The second pressure sensor 36 measures the pressure of the CO2 refrigerant compressed by the compressor 6. The second pressure sensor 36 can be disposed in any of the first path 14 and the second path 16 between the compressor 6 and the variable expansion valve 32. In the present embodiment, the second pressure sensor 36 is disposed in the first path 14 between the compressor 6 and the water-cooled gas cooler 8.

[0047] (Temperature Sensor)

[0048] A plurality of temperature sensors for measuring the temperature of the processing aid fluid, the industrial water, and the CO 2 refrigerant are provided in the cooling mechanism 2 . The values ​​measured by the temperature sensors are sent to the controller 4 .

[0049] (Sensor for measuring the temperature of processing fluid)

[0050] As sensors for measuring the temperature of the processing aid liquid, first and second temperature sensors 38 and 40 are provided. The first temperature sensor 38 measures the temperature of the processing aid liquid flowing out of the evaporator 12 . On the other hand, the second temperature sensor 40 measures the temperature of the processing aid liquid flowing into the evaporator 12 .

[0051] (Sensor for measuring the temperature of industrial water)

[0052] A third temperature sensor 42 is provided as a sensor for measuring the temperature of the process water. The third temperature sensor 42 measures the temperature of the process water flowing into the water-cooled gas cooler 8.

[0053] (Sensor for measuring the temperature of CO2 refrigerant)

[0054] As sensors for measuring the temperature of the CO2 refrigerant, fourth to eighth temperature sensors 44, 46, 48, 50, 52 are provided. The fourth temperature sensor 44 measures the temperature of the CO2 refrigerant sent from the compressor 6. The fifth temperature sensor 46 measures the temperature of the CO2 refrigerant sent from the water-cooled gas cooler 8. The sixth temperature sensor 48 measures the temperature of the CO2 refrigerant sent from the internal heat exchanger 10 (the CO2 refrigerant sent to the evaporator 12 via the variable expansion valve 32). The seventh temperature sensor 50 measures the temperature of the CO2 refrigerant sent from the evaporator 12 (the same temperature as the temperature of the CO2 refrigerant sent from the variable expansion valve 32). In addition, the eighth temperature sensor 52 measures the temperature of the CO2 refrigerant sent to the compressor 6. In addition, the sixth / seventh temperature sensors 48 and 50 can be omitted and may not be configured.

[0055] (Processing aid)

[0056] The processing aid liquid cooled by the cooling mechanism 2 is used, for example, in a cutting device (not shown) for cutting a semiconductor wafer. The cutting device has a cutting unit for cutting a semiconductor wafer. Figure 1 , an exploded perspective view of a spindle housing 54 is shown. The spindle housing 54 rotatably accommodates the spindle of the cutting unit, and the spindle housing 54 is connected to the evaporator 12 via a pipe 56. The machining aid fluid circulates between the spindle housing 54 and the evaporator 12 via the pipe 56.

[0057] However, the processing device using the processing aid liquid cooled by the cooling mechanism 2 is not limited to the dicing device, and various processing devices such as a grinding device for grinding and thinning a semiconductor wafer can be used as the object. In addition, the processing aid liquid includes a fluid used as processing water and discarded, such as cutting water, in addition to the circulating fluid circulated in the processing device.

[0058] (Operation of Cooling Mechanism 2)

[0059] Next, the operation of the cooling mechanism 2 will be described. First, the basic operation of the cooling mechanism 2 will be described, and then the operation of improving the cooling capacity / cooling efficiency of the cooling mechanism 2 will be described, and the operation of increasing or decreasing the cooling amount of the processing aid fluid will be described.

[0060] (Basic actions)

[0061] First, in the cooling mechanism 2, when the operator inputs an action instruction to the controller 4, the setting unit 4a of the controller 4 sets the value (set value) to be detected by each sensor according to the input action instruction. Specifically, the setting unit 4a sets the set temperature of the processing aid liquid and the set pressure / set temperature of the CO2 refrigerant. The set temperature of the processing aid liquid is the temperature input by the operator. The set pressure / set temperature of the refrigerant is determined by the controller 4 according to the set temperature of the processing aid liquid.

[0062] (Set temperature of processing aid fluid: first / second temperature)

[0063] First, the setting unit 4a sets the first temperature to be detected by the first temperature sensor 38 or the second temperature to be detected by the second temperature sensor 40 as the set temperature of the processing aid liquid. The first temperature is the set temperature of the processing aid liquid flowing out of the evaporator 12. On the other hand, the second temperature is the set temperature of the processing aid liquid flowing into the evaporator 12. Here, for example, the first temperature can be set to 23°C and the second temperature can be set to 25°C.

[0064] (Set pressure of CO2 refrigerant: first / second pressure value)

[0065] In addition, the setting unit 4a sets the first pressure value to be detected by the first pressure sensor 34 and the second pressure value to be detected by the second pressure sensor 36 as the set pressure of the CO2 refrigerant. The first pressure value is the set pressure of the CO2 refrigerant expanded by the variable expansion valve 32. The first pressure value can be, for example, about 4 MPa (absolute pressure). On the other hand, the second pressure value is the set pressure of the CO2 refrigerant compressed by the compressor 6. The second pressure value is the pressure of the compressed CO2 refrigerant, and is therefore set to a value greater than the set pressure (first pressure value) of the CO2 refrigerant before compression. Specifically, the second pressure value can be about 10 MPa (absolute pressure).

[0066] (Set temperature of CO2 refrigerant: 4th / 5th / 8th temperature)

[0067] Furthermore, the setting unit 4a sets the fourth temperature to be detected by the fourth temperature sensor 44, the fifth temperature to be detected by the fifth temperature sensor 46, and the eighth temperature to be detected by the eighth temperature sensor 52 as the set temperature of the CO2 refrigerant. The fourth temperature is the set temperature of the CO2 refrigerant sent from the compressor 6. The fourth temperature is, for example, 100°C. The fifth temperature is the set temperature of the CO2 refrigerant sent from the water-cooled gas cooler 8. The fifth temperature can be set to, for example, 31°C. The eighth temperature is the set temperature of the CO2 refrigerant sent to the compressor 6. The eighth temperature can be, for example, about 20°C.

[0068] In addition, the fifth temperature may be set according to the temperature of the industrial water flowing into the water-cooled gas cooler 8 (the measurement value of the third temperature sensor 42). For example, a temperature 5°C higher than the temperature of the industrial water flowing into the water-cooled gas cooler 8 may be set as the fifth temperature. Specifically, if the temperature of the industrial water is 25°C, the fifth temperature is 30°C. How much higher than the temperature of the industrial water is set as the fifth temperature can be appropriately determined according to the heat exchange area (heat exchange rate) of the water-cooled gas cooler 8.

[0069] (Set temperature of CO2 refrigerant: 6th / 7th temperature)

[0070] As required, the setting unit 4a can set the sixth temperature to be detected by the sixth temperature sensor 48 and the seventh temperature to be detected by the seventh temperature sensor 50 as the set temperature of the CO2 refrigerant. The sixth temperature is the set temperature of the CO2 refrigerant sent from the internal heat exchanger 10 (the CO2 refrigerant sent to the evaporator 12 via the variable expansion valve 32). The sixth temperature can be set to 22°C. The seventh temperature is the set temperature of the CO2 refrigerant sent from the evaporator 12. The seventh temperature can be, for example, about 5°C.

[0071] Thus, the setting unit 4a sets at least the first pressure value to be detected by the first pressure sensor 34, the second pressure value to be detected by the second pressure sensor 36, the first temperature to be detected by the first temperature sensor 38 or the second temperature to be detected by the second temperature sensor 40, the fourth temperature to be detected by the fourth temperature sensor 44, the fifth temperature to be detected by the fifth temperature sensor 46, and the eighth temperature to be detected by the eighth temperature sensor 52. Furthermore, the setting unit 4a may also set the sixth temperature to be detected by the sixth temperature sensor 48 and the seventh temperature to be detected by the seventh temperature sensor 50.

[0072] (Control by Control Unit 4b)

[0073] If the set temperature of the processing aid fluid and the set pressure / set temperature of the CO2 refrigerant are set by the setting unit 4a, the control unit 4b controls the opening of the variable expansion valve 32 and the speed of the compressor 6 in such a way that the value of the first temperature sensor 38 or the second temperature sensor 40 becomes the set temperature (first temperature or second temperature), so that the CO2 refrigerant follows a path defined by the set pressure value (first / second pressure value) and temperature (fourth to eighth temperatures) around the critical point.

[0074] (Opening degree of variable expansion valve 32)

[0075] By controlling the opening of the variable expansion valve 32, the pressure of the CO2 refrigerant and the temperature of the processing aid liquid can be adjusted. When the opening of the variable expansion valve 32 becomes larger, the flow rate of the CO2 refrigerant passing through the variable expansion valve 32 increases, so the value of the second pressure sensor 36 becomes smaller. In addition, when the opening of the variable expansion valve 32 becomes larger, the flow rate of the CO2 refrigerant in the evaporator 12 increases, so the values ​​of the first / second temperature sensors 38, 40 (the temperature of the processing aid liquid) decrease. On the other hand, when the opening of the variable expansion valve 32 becomes smaller, the value of the second pressure sensor 36 becomes larger, and the values ​​of the first / second temperature sensors 38, 40 increase.

[0076] (Speed ​​of compressor 6)

[0077] In addition, the pressure of the CO2 refrigerant can be adjusted by controlling the rotation speed of the compressor 6. When the rotation speed of the compressor 6 increases, the amount of CO2 refrigerant sucked by the compressor 6 increases, so the value of the first pressure sensor 34 decreases. Conversely, when the rotation speed of the compressor 6 decreases, the value of the first pressure sensor 34 increases.

[0078] (Critical Point)

[0079] The critical point is usually determined by the temperature and pressure at which a substance becomes supercritical. The critical point in this embodiment is determined by the critical temperature of 31.1°C and the critical pressure of 7.38 MPa at which CO2, a refrigerant, becomes supercritical. Figure 2 In the equation, the critical point of CO2 is represented by the symbol P. Figure 2 This is a pressure-specific enthalpy diagram (Mollier diagram) of CO2, where the vertical axis represents pressure and the horizontal axis represents specific enthalpy.

[0080] (Path around the critical point)

[0081] The path around the critical point (the path of the CO2 refrigerant around the critical point defined by the set pressure value and temperature) is, for example, Figure 2 The path R of points A, B, C, D, E, and F. Figure 2 Points A to F in the figure are based on Figure 1 Points A to F are plotted according to their respective temperatures and pressures.

[0082] In this embodiment, if Figure 1 As shown, the outlet of the compressor 6 is set to point A, the outlet of the water-cooled gas cooler 8 is set to point B, the outlet of the second path 16 in the internal heat exchanger 10 is set to point C, the outlet of the variable expansion valve 32 is set to point D, the outlet of the evaporator 12 is set to point E, and the outlet of the third path 18 in the internal heat exchanger 10 is set to point F.

[0083] The specific values ​​of pressure / temperature at points A to F are as follows: Figure 2 As shown. That is, the pressure at points A, B, and C is, for example, 10 MPa, and the pressure at points D, E, and F is, for example, 4 MPa. In addition, as a specific example of the temperature at points A to F, the temperature at point A is about 100°C, the temperature at point B is about 31°C, the temperature at point C is about 22°C, the temperatures at points D and E are about 5°C, and the temperature at point F is about 20°C.

[0084] Here, the temperature and pressure / specific enthalpy at each point from point A to point F are explained using symbols. That is, the temperature at point A is TA, the pressure is PA, and the specific enthalpy is EA; the temperature at point B is TB, the pressure is PB, and the specific enthalpy is EB; the temperature at point C is TC, the pressure is PC, and the specific enthalpy is EC; the temperature at point D is TD, the pressure is PD, and the specific enthalpy is ED; the temperature at point E is TE, the pressure is PE, and the specific enthalpy is EE; the temperature at point F is TF, the pressure is PF, and the specific enthalpy is EF.

[0085] (CO2 refrigerant flow: Point F → Point A)

[0086] When the control as described above is started, first, the CO2 refrigerant fed into the compressor 6 from point F is compressed by the compressor 6 to reach point A exceeding the critical point. At this time, the temperature of the CO2 refrigerant changes (increases) from TF to TA, the pressure of the CO2 refrigerant changes (increases) from PF to PA, and the specific enthalpy of the CO2 refrigerant changes (increases) from EF to EA.

[0087] (Point A→Point B)

[0088] Next, the CO2 refrigerant sent from point A to the water-cooled gas cooler 8 is cooled by the water-cooled gas cooler 8 and reaches point B. At this time, the temperature of the CO2 refrigerant changes (decreases) from TA to TB, the pressure of the CO2 refrigerant remains unchanged (PA=PB), and the specific enthalpy of the CO2 refrigerant changes (decreases) from EA to EB. The heat of the CO2 refrigerant is taken away by the industrial water, so the temperature difference between TA and TB and the specific enthalpy difference between EA and EB are discarded to the outside by the water-cooled gas cooler 8. In addition, the pressure PB and temperature TB of the CO2 refrigerant exceed the critical point, so the CO2 refrigerant does not liquefy at point B.

[0089] (Point B→Point C)

[0090] Next, the CO2 refrigerant sent from point B to the internal heat exchanger 10 takes away heat from the CO2 refrigerant sent from the evaporator 12 and reaches point C. At this time, the temperature of the CO2 refrigerant changes (decreases) from TB to TC, the pressure of the CO2 refrigerant remains unchanged (PB = PC), and the specific enthalpy of the CO2 refrigerant changes (decreases) from EB to EC. In addition, the temperature TC of the CO2 refrigerant is lower than the critical point, so a part of the CO2 refrigerant is liquefied at point C.

[0091] (Point C→Point D)

[0092] Next, the CO2 refrigerant fed into the variable expansion valve 32 from point C is decompressed by the variable expansion valve 32 and reaches point D. At this time, the temperature of the CO2 refrigerant changes (decreases) from TC to TD, the pressure of the CO2 refrigerant changes (decreases) from PC to PD, and the specific enthalpy of the CO2 refrigerant remains unchanged (EC=ED). In addition, the CO2 refrigerant at point D is in a state where gas and liquid exist in a mixture.

[0093] (Point D→Point E)

[0094] Next, the CO2 refrigerant fed into the evaporator 12 from point D takes energy from the process aid liquid through the evaporator 12 and reaches point E. At this time, the heat taken from the process aid liquid is used to vaporize the liquid CO2 refrigerant, so the temperature of the CO2 refrigerant does not change (TD=TE). In addition, the pressure of the CO2 refrigerant does not change (PD=PE). However, the specific enthalpy of the CO2 refrigerant changes (increases) from ED to EE. Point E approaches the saturated vapor line passing through the critical point, and most of the CO2 refrigerant becomes gas.

[0095] (Point E→Point F)

[0096] Next, the CO2 refrigerant sent into the internal heat exchanger 10 from point E takes away heat from the CO2 refrigerant sent into the internal heat exchanger 10 from point B. Therefore, even if liquid remains in the CO2 refrigerant at point E, the liquid in the CO2 refrigerant turns into gas in the internal heat exchanger 10. That is, all the CO2 refrigerant that reaches point F located outside the saturated vapor line turns into gas. Therefore, the CO2 refrigerant that flows into the compressor 6 from point F becomes only gas. Moreover, the load on the compressor 6 can be reduced. When the CO2 refrigerant reaches point F from point E, the temperature of the CO2 refrigerant changes (increases) from TE to TF, the pressure of the CO2 refrigerant remains unchanged (PE=PF), and the specific enthalpy of the CO2 refrigerant changes (increases) from EE to EF.

[0097] Thus, in the cooling mechanism 2, the control unit 4b controls the opening of the variable expansion valve 32 and the rotation speed of the compressor 6 so that the value of the first temperature sensor 38 or the second temperature sensor 40 becomes the set temperature (the first temperature or the second temperature) and the CO2 refrigerant follows the path R defined by the set pressure value (the first / second pressure value) and temperature (the fourth to eighth temperatures) around the critical point P. As a result, the CO2 refrigerant flowing into the compressor 6 from the point F is only gas, and therefore, no liquid compression occurs.

[0098] (Cooling capacity)

[0099] Next, the cooling capacity of the cooling mechanism 2 will be described. The cooling capacity refers to the capacity of the CO2 refrigerant to cool the processing aid fluid in the evaporator 12. Therefore, the cooling capacity can be expressed as in the following mathematical formula 1 using the specific enthalpy before and after the evaporator 12.

[0100] Cooling capacity = ED-EE... Formula 1

[0101] ED is the specific enthalpy of the CO 2 refrigerant at the point D before passing through the evaporator 12 . Also, EE is the specific enthalpy of the CO 2 refrigerant at the point E after passing through the evaporator 12 .

[0102] However, the specific enthalpy EE of the CO2 refrigerant at point E cannot be derived even if the temperature / pressure at point E is detected. The CO2 refrigerant at point E is in a state of gas-liquid mixture. The state change of the CO2 refrigerant from point D to point E occurs under the condition of constant temperature / pressure. Therefore, the temperature / pressure at point E is detected as the same value as the temperature / pressure at point D. Therefore, the specific enthalpy of the CO2 refrigerant at point E cannot be derived even if the temperature / pressure at point E is detected. In addition, the temperature TE at point E can be detected by the seventh temperature sensor 50, and the pressure PE at point E can be detected by the first pressure sensor 34.

[0103] On the other hand, the specific enthalpies EA to ED and EF of the CO 2 refrigerant at points A to D and F can be determined from a pressure-specific enthalpy diagram by detecting the temperature / pressure at each point and using the detected temperature / pressure at each point.

[0104] The temperatures of the CO2 refrigerant at points A to D and F can be detected by the following sensors. That is, the temperature TA at point A can be detected by the fourth temperature sensor 44, the temperature TB at point B can be detected by the fifth temperature sensor 46, the temperature TC at point C can be detected by the sixth temperature sensor 48, the temperature TD at point D can be detected by the seventh temperature sensor 50, and the temperature TF at point F can be detected by the eighth temperature sensor 52.

[0105] In addition, the pressure of the CO2 refrigerant at points A to D and F can be detected by the following sensors. That is, the pressure PA at point A can be detected by the second pressure sensor 36, the pressure PB at point B can be detected by the second pressure sensor 36, the pressure PC at point C can be detected by the second pressure sensor 36, the pressure PD at point D can be detected by the first pressure sensor 34, and the pressure PF at point F can be detected by the first pressure sensor 34.

[0106] Then, the specific enthalpy at point A to point D and point F can be obtained from the pressure-specific enthalpy diagram. That is, the specific enthalpy EA at point A can be detected from the pressure-specific enthalpy diagram using the temperature / pressure of point A, the specific enthalpy EB at point B can be detected from the pressure-specific enthalpy diagram using the temperature / pressure of point B, the specific enthalpy EC at point C can be detected from the pressure-specific enthalpy diagram using the temperature / pressure of point C, the specific enthalpy ED at point D can be detected from the pressure-specific enthalpy diagram using the temperature / pressure of point D, and the specific enthalpy EF at point F can be detected from the pressure-specific enthalpy diagram using the temperature / pressure of point F.

[0107] Therefore, a description will be given of a case where the cooling capacity described above is expressed using specific enthalpy that can be obtained from a pressure-specific enthalpy diagram.

[0108] First, when the specific enthalpy EF at the F point is used, the above-mentioned mathematical formula 1 can be transformed as in the following mathematical formula 2.

[0109] Cooling capacity = ED-EE

[0110] =(EF-EE)-(EF-ED)… Mathematical formula 2

[0111] Next, based on the heat exchange performed in the internal heat exchanger 10, the following mathematical formula 3 is derived.

[0112] |EB-EC|=|EE-EF|…Mathematical formula 3

[0113] As described above, the CO2 refrigerant sent into the internal heat exchanger 10 from point E takes away heat from the CO2 refrigerant sent into the internal heat exchanger 10 from point B. The specific enthalpy associated with the heat taken away from the CO2 refrigerant from point E to point F can be expressed as |EE-EF|. In addition, the specific enthalpy associated with the heat taken away from the CO2 refrigerant from point B to point C can be expressed as |EB-EC|. Moreover, the above specific enthalpies are equal, so the above mathematical formula 3 is derived. That is, the absolute value of the difference between EB and EC and the absolute value of the difference between EE and EF are equal.

[0114] In addition, as described above, the specific enthalpy EC at point C is equal to the specific enthalpy ED at point D.

[0115] EC=ED…Mathematical formula 4

[0116] The cooling capacity can be expressed as in Formula 5 using specific enthalpies EB and EF that can be obtained from Formulas 2 to 4 and from a pressure-specific enthalpy diagram.

[0117] Cooling capacity=(EF-EE)-(EF-ED)

[0118] =(EB-EC)-(EF-EC)

[0119] =EB-EF…Mathematical formula 5

[0120] According to the above mathematical formula 5, it can be understood that when the difference (EB-EF) between the specific enthalpy EB and the specific enthalpy EF becomes larger, the cooling capacity is improved. Therefore, the controller 4 of the present embodiment increases the cooling capacity by increasing the difference (EB-EF) between the specific enthalpy EB and the specific enthalpy EF. That is, the controller 4 controls in the following manner: by reducing the opening of the variable expansion valve 32 to increase the value of the second pressure sensor 36, or by increasing the opening of the variable expansion valve 32 to reduce the value of the second pressure sensor 36, the pressure of the CO2 refrigerant is adjusted to the set pressure value (first / second pressure value), and the cooling capacity is improved.

[0121] In addition, the specific enthalpy EE at the point E can be calculated according to Formula 6 which is a transformation of Formula 3.

[0122] EE = EF - (EB - EC) ... Formula 6

[0123] (Cooling efficiency)

[0124] Next, the cooling efficiency of the cooling mechanism 2 is described. The cooling efficiency refers to the value obtained by dividing the cooling capacity by the compression work (the work done by the compressor 6). That is, cooling efficiency = (cooling capacity / compression work). The compression work can be expressed as shown in Mathematical Formula 7 using the specific enthalpy EF at point F (specific enthalpy before compression) and the specific enthalpy EA at point A (specific enthalpy after compression).

[0125] Compression work = EF-EA… Formula 7

[0126] Therefore, based on the above-mentioned equations 1 and 7, the cooling efficiency can be expressed as in equation 8.

[0127] Cooling efficiency (cooling capacity / compression work) = (ED-EE) / (EF-EA)… Formula 8

[0128] Furthermore, it is preferred that the controller 4 controls the temperature, pressure, and specific enthalpy of the CO 2 refrigerant so as to maximize the cooling efficiency derived from the mathematical formula 8.

[0129] Furthermore, when calculating the cooling efficiency, the controller 4 of the present embodiment obtains the cooling capacity (Formula 5) based on the above-mentioned Formula 4 (EC=ED) and the above-mentioned Formula 6 {EE=EF-(EB-EC)}.

[0130] In other words, cooling capacity = ED - EE

[0131] =EC-{EF-(EB-EC)}

[0132] =EB-EF…Formula 5.

[0133] When equation 5 is substituted into equation 8, the cooling efficiency becomes equation 9.

[0134] Cooling efficiency (cooling capacity / compression work) = (ED-EE) / (EF-EA)

[0135] =(EB-EF) / (EF-EA)…Mathematical formula 9

[0136] According to Mathematical Formula 9, it can be understood that when the difference (EB-EF) between the specific enthalpy EB and the specific enthalpy EF becomes larger, the cooling capacity and cooling efficiency are improved. Therefore, the controller 4 of the present embodiment improves the cooling capacity and cooling efficiency by increasing the difference (EB-EF) between the specific enthalpy EB and the specific enthalpy EF. That is, the controller 4 increases the value of the second pressure sensor 36 by reducing the opening of the variable expansion valve 32, or reduces the value of the second pressure sensor 36 by increasing the opening of the variable expansion valve 32, thereby adjusting the pressure of the CO2 refrigerant to the set pressure value (first / second pressure value) and controlling the cooling efficiency (cooling capacity / compression work).

[0137] In addition, according to Mathematical Formula 5 and Mathematical Formula 9, the sixth / seventh temperature sensors 48 and 50 can be omitted. In order to calculate the cooling capacity / cooling efficiency according to Mathematical Formula 5 and Mathematical Formula 9, the values ​​of the specific enthalpy EA, EB, and EF at points A, B, and F are required. In order to detect the specific enthalpy EA, EB, and EF based on the pressure-specific enthalpy diagram, the values ​​of the temperatures TA, TB, and TF and the pressures PA, PB, and PB at points A, B, and F are required. If the fourth / fifth / eighth temperature sensors 44, 46, and 52 and the first / second pressure sensors 34, 35, and 36 are provided, these values ​​can be measured. Therefore, according to Mathematical Formula 5 and Mathematical Formula 9, the sixth / seventh temperature sensors 48 and 50 can also be omitted.

[0138] Next, the operation of increasing or decreasing the cooling amount of the processing aid liquid used in the processing apparatus (that is, changing the set temperature of the processing aid liquid) will be described.

[0139] (When the cooling amount of the processing fluid is reduced)

[0140] First, the description will be made from the case where the cooling amount of the processing aid liquid used in the processing device is reduced (the case where the set temperature of the processing aid liquid is increased). In this case, the control unit 4b of the controller 4 reduces the opening of the variable expansion valve 32. As a result, the flow rate of the CO2 refrigerant in the evaporator 12 is reduced, so the cooling amount of the processing aid liquid can be reduced. As a result, the value of the first temperature sensor 38 or the second temperature sensor 40 increases.

[0141] On the contrary, when the flow rate of CO2 refrigerant in the evaporator 12 is reduced, the value measured by the first pressure sensor 34 decreases, and the value measured by the second pressure sensor 36 increases. As a result, the value of the first pressure sensor 34 may be lower than the first pressure value and the value of the second pressure sensor 36 may exceed the second pressure value.

[0142] Therefore, the control unit 4b increases the value of the first pressure sensor 34 to the first pressure value and decreases the value of the second pressure sensor 36 to the second pressure value, thereby appropriately decreasing the rotation speed of the compressor 6 according to the increase in the set temperature of the processing fluid.

[0143] In this case, sometimes, although the rotation speed of the compressor 6 reaches the lower limit of the allowable rotation speed, the value of the first pressure sensor 34 does not rise to the first pressure value and the value of the second pressure sensor 36 does not fall to the second pressure value. In this case, the control unit 4b further operates the normally closed variable bypass valve 28 in a manner from closed to open to increase the opening degree, thereby increasing the flow rate of the CO2 refrigerant in the evaporator 12. In this way, the value of the first pressure sensor 34 can be raised to the first pressure value and the value of the second pressure sensor 36 can be lowered to the second pressure value without reducing the rotation speed of the compressor 6 to a rotation speed lower than the lower limit of the allowable rotation speed.

[0144] Therefore, in the cooling mechanism 2, even if the set temperature of the processing aid fluid is increased, the suction pressure and the discharge pressure of the compressor 6 do not change significantly, and thus the maximum cooling efficiency and the maximum cooling capacity can be obtained.

[0145] In this way, the control unit 4b reduces the opening of the variable expansion valve 32 to reduce the flow rate of the CO2 refrigerant flowing in the evaporator 12 while reducing the cooling amount of the processing aid fluid. Concomitantly, the control unit 4b increases the opening of the variable bypass valve 28 of the bypass path 30 to increase the flow rate of the CO2 refrigerant flowing into the evaporator 12 to ensure that the rotation speed of the compressor 6 does not reach the lower limit.

[0146] (Increasing the cooling capacity of the processing fluid)

[0147] Contrary to the above, when the cooling amount of the processing aid liquid used in the processing device is increased in the cooling mechanism 2 (when the set temperature of the processing aid liquid is lowered), the control unit 4b of the controller 4 increases the opening of the variable expansion valve 32. As a result, the flow rate of the CO2 refrigerant in the evaporator 12 increases, so the required cooling amount of the processing aid liquid can be increased. As a result, the value of the first temperature sensor 38 or the second temperature sensor 40 decreases.

[0148] However, when the flow rate of CO2 refrigerant in the evaporator 12 increases, the value measured by the first pressure sensor 34 increases, and the value measured by the second pressure sensor 36 decreases. As a result, the value of the first pressure sensor 34 sometimes exceeds the first pressure value, and the value of the second pressure sensor 36 sometimes falls below the second pressure value.

[0149] Therefore, the controller 4b appropriately increases the rotation speed of the compressor 6 according to the drop in the set temperature of the processing fluid. This can reduce the value of the first pressure sensor 34 to the first pressure value and increase the value of the second pressure sensor 36 to the second pressure value.

[0150] Therefore, in the cooling mechanism 2, even if the set temperature of the processing aid fluid is lowered, the suction pressure and the discharge pressure of the compressor 6 do not change significantly, and thus the maximum cooling efficiency and the maximum cooling capacity can be obtained.

[0151] In addition, when the set temperature of the processing aid liquid is low, the amount of gasification of the CO2 refrigerant in the evaporator 12 decreases, so the liquid CO2 refrigerant may be sucked into the compressor 6. However, in the cooling mechanism 2 of the present embodiment, the CO2 refrigerant flowing out of the evaporator 12 and the CO2 refrigerant flowing out of the water-cooled gas cooler 8 perform heat exchange in the internal heat exchanger 10. In this heat exchange, the CO2 refrigerant sent out of the evaporator 12 takes heat from the CO2 refrigerant sent out of the water-cooled gas cooler 8. Therefore, even if there is liquid remaining in the CO2 refrigerant flowing out of the evaporator 12, the liquid in the CO2 refrigerant becomes gas in the internal heat exchanger 10.

[0152] In this way, the control unit 4b increases the opening of the variable expansion valve 32 and the rotation speed of the compressor 6 while increasing the cooling amount of the processing aid fluid, thereby increasing the flow rate of the CO2 refrigerant flowing in the evaporator 12. At the same time, the liquid CO2 remaining in the CO2 refrigerant sent out from the evaporator 12 is vaporized in the internal heat exchanger 10, thereby reducing the burden on the compressor 6.

[0153] (Adjustment of the opening degree of the water control valve 20)

[0154] In addition, the control unit 4b of the controller 4 preferably adjusts the opening of the water control valve 20 according to the temperature of the industrial water detected by the third temperature sensor 42 to adjust the flow rate of the industrial water introduced into the water-cooled gas cooler 8 to control the cooling of the CO2 refrigerant.

[0155] When the opening of the water control valve 20 becomes larger, the amount of industrial water flowing into the water-cooled gas cooler 8 increases, promoting the cooling of the CO2 refrigerant in the water-cooled gas cooler 8. On the other hand, when the opening of the water control valve 20 becomes smaller, the amount of industrial water flowing into the water-cooled gas cooler 8 decreases, suppressing the cooling of the CO2 refrigerant in the water-cooled gas cooler 8.

[0156] Therefore, the control unit 4b adjusts the opening of the water control valve 20 according to the temperature of the industrial water, controls the cooling of the CO2 refrigerant in the water-cooled gas cooler 8, and thereby adjusts the temperature of the CO2 refrigerant sent from the water-cooled gas cooler 8 to the set temperature (fifth temperature).

[0157] As described above, in the cooling mechanism 2, the CO2 refrigerant flowing into the compressor 6 is only gas, so no liquid compression occurs. In addition, the cooling mechanism 2 of this embodiment calculates the cooling efficiency by mathematical formula 9, so the pressure value of the CO2 refrigerant for improving the cooling efficiency can be set according to the operating conditions.

[0158] Cooling efficiency = (EB-EF) / (EF-EA)… Formula 9

[0159] In addition, regarding the configuration of the compressor 6, the water-cooled gas cooler 8, the internal heat exchanger 10, and the evaporator 12, as shown in FIG. Figure 3 As shown, the water-cooled gas cooler 8 is preferably provided above the compressor 6 , the internal heat exchanger 10 , and the evaporator 12 .

[0160] When the CO2 refrigerant reaches a supercritical state, the lubricating oil in the compressor 6 tends to dissolve in the CO2 refrigerant and easily flow out of the compressor 6. When the lubricating oil in the compressor 6 dissolved in the CO2 refrigerant in a supercritical state is retained in the water-cooled gas cooler 8 or the internal heat exchanger 10 and does not return to the compressor 6, abnormal wear may occur in the compressor 6.

[0161] Therefore, if Figure 3As shown, the water-cooled gas cooler 8 is arranged above the compressor 6, etc., thereby reducing the installation area of ​​the cooling mechanism 2 as a whole, and making the flow direction of the supercritical CO2 refrigerant in the water-cooled gas cooler 8 and the internal heat exchanger 10 the gravity direction (that is, from top to bottom). Therefore, it is possible to prevent the lubricating oil in the compressor 6 dissolved in the supercritical CO2 refrigerant from being retained in the water-cooled gas cooler 8 or the internal heat exchanger 10, etc., and the lubricating oil can be returned to the compressor 6. As a result, it is possible to prevent the compressor 6 from abnormal wear.

[0162] The CO2 refrigerant expanded by the variable expansion valve 32 flows in the evaporator 12 and the internal heat exchanger 10 in the anti-gravity direction (from bottom to top). However, by setting the lower end positions of the compressor 6, the internal heat exchanger 10 and the evaporator 12 to the same height, the height difference from the outlet of the evaporator 12 to the compressor 6 can be minimized, thereby making it easier for the lubricating oil to return to the compressor 6.

[0163] In addition, when the compressor 6 is restarted after stopping, it is preferable to maintain the variable expansion valve 32 and the variable bypass valve 28 at a predetermined opening degree, and Figure 4 As shown, the operation at the intermediate speed and the operation at the lowest speed are repeated a plurality of times at a predetermined time. Thus, the lubricating oil accumulated in the internal heat exchanger 10 and the evaporator 12 when the compressor 6 is stopped can be efficiently returned to the compressor 6.

Claims

1. A cooling mechanism for cooling a processing aid liquid used in a processing device, wherein: The cooling mechanism has: Controller; A compressor, which compresses the CO2 refrigerant; A water-cooled gas cooler that cools the CO2 refrigerant compressed by the compressor with compression heat; An internal heat exchanger, which is fed with cooled CO2 refrigerant; An evaporator that vaporizes the CO2 refrigerant sent from the internal heat exchanger to generate vaporization heat and cools the processing aid liquid used in the processing device; A first path connecting the compressor to the water-cooled gas cooler; a second path connecting the water-cooled gas cooler to the evaporator; a third path connecting the evaporator to the compressor; a fourth path for introducing industrial water to the water-cooled gas cooler, the fourth path having a water control valve; as well as a bypass path connected by a first connection portion connected to the first path and a second connection portion connected to the second path, the bypass path having a variable bypass valve, The internal heat exchanger is arranged across the second path and the third path in such a manner that the CO2 refrigerant sent out by the evaporator takes heat from the CO2 refrigerant sent out by the water-cooled gas cooler. In the second path, a variable expansion valve for adjusting the flow rate of the cooled CO2 refrigerant is disposed between the internal heat exchanger and the second connecting portion. A first pressure sensor for measuring the pressure of the CO2 refrigerant is provided on any one of the second path and the third path between the variable expansion valve and the compressor. A second pressure sensor for measuring the pressure of the CO2 refrigerant compressed by the compressor is disposed on any one of the first path and the second path between the compressor and the variable expansion valve. The cooling mechanism is equipped with: A first temperature sensor, which measures the temperature of the processing aid fluid used in the processing device flowing out of the evaporator; a second temperature sensor that measures the temperature of the processing aid fluid flowing into the evaporator; a third temperature sensor for measuring the temperature of the process water flowing into the water-cooled gas cooler; a fourth temperature sensor for measuring the temperature of the CO2 refrigerant delivered from the compressor; a fifth temperature sensor for measuring the temperature of the CO2 refrigerant delivered from the water-cooled gas cooler; a sixth temperature sensor provided as needed, which measures the temperature of the CO2 refrigerant sent from the internal heat exchanger; a seventh temperature sensor provided as needed, which measures the temperature of the CO 2 refrigerant sent from the evaporator to be the same temperature as the temperature of the CO 2 refrigerant sent from the variable expansion valve; as well as an eighth temperature sensor, which measures the temperature of the CO2 refrigerant fed into the compressor, The controller includes a setting unit, which sets at least a first pressure value to be detected by the first pressure sensor, a second pressure value to be detected by the second pressure sensor, a first temperature to be detected by the first temperature sensor or a second temperature to be detected by the second temperature sensor, a fourth temperature to be detected by the fourth temperature sensor, a fifth temperature to be detected by the fifth temperature sensor, and an eighth temperature to be detected by the eighth temperature sensor. In such a way that the value of the first temperature sensor or the second temperature sensor becomes the set temperature, the CO2 refrigerant follows a path defined by the set pressure value and temperature around the critical point to control the opening of the variable expansion valve and the speed of the compressor, wherein the critical point is determined by the critical temperature of 31.1°C and the critical pressure of 7.38MPa.

2. The cooling mechanism according to claim 1, wherein: The controller reduces the opening of the variable expansion valve to reduce the flow rate of the CO2 refrigerant flowing in the evaporator while reducing the cooling amount of the processing aid fluid used in the processing device. Concomitantly, the controller increases the opening of the variable bypass valve in the bypass path to increase the flow rate of the CO2 refrigerant flowing into the evaporator to ensure that the compressor does not reach the lower limit value.

3. The cooling mechanism according to claim 1, wherein: The controller increases the opening of the variable expansion valve and the rotation speed of the compressor to increase the cooling amount of the processing aid fluid used in the processing device, thereby increasing the flow rate of the CO2 refrigerant flowing in the evaporator. At the same time, the liquid CO2 remaining in the CO2 refrigerant sent from the evaporator is vaporized in the internal heat exchanger, thereby reducing the burden on the compressor.

4. The cooling mechanism according to claim 1, wherein: The controller adjusts the opening of the water control valve according to the temperature of the industrial water detected by the third temperature sensor, thereby adjusting the flow rate of the industrial water introduced into the water-cooled gas cooler and controlling the cooling of the CO2 refrigerant.

5. The cooling mechanism according to claim 1, wherein: The controller increases the value of the second pressure sensor by reducing the opening of the variable expansion valve, and reduces the value of the second pressure sensor by increasing the opening of the variable expansion valve, thereby adjusting the value of the second pressure sensor to the set pressure value and controlling the cooling efficiency, wherein the cooling efficiency is cooling capacity / compression work.

6. The cooling mechanism according to any one of claims 1 to 5, wherein: The outlet of the compressor is set as point A. The outlet of the water-cooled gas cooler is set as point B. The outlet of the second path in the internal heat exchanger is set as point C, The outlet of the variable expansion valve is set as point D. The outlet of the evaporator is set as point E. The outlet of the third path in the internal heat exchanger is set as point F, The temperature at point A is TA, the pressure is PA, and the specific enthalpy is EA. The temperature at point B is TB, the pressure is PB, and the specific enthalpy is EB. The temperature at point C is TC, the pressure is PC, and the specific enthalpy is EC. The temperature at point D is TD, the pressure is PD, and the specific enthalpy is ED. The temperature at point E is TE, the pressure is PE, and the specific enthalpy is EE. The temperature at point F is TF, the pressure is PF, and the specific enthalpy is EF. In this case, The CO2 refrigerant fed into the compressor from point F is compressed by the compressor and reaches point A which exceeds the critical point. The temperature changes from TF to TA, the pressure changes from PF to PA, and the specific enthalpy changes from EF to EA. The CO2 refrigerant fed into the water-cooled gas cooler from point A is cooled by the water-cooled gas cooler and reaches point B. The temperature changes from TA to TB, the pressure remains unchanged, that is, PA=PB, the specific enthalpy changes from EA to EB, and the temperature difference between TA and TB and the specific enthalpy difference between EA and EB are discarded to the outside by the water-cooled gas cooler. The pressure PB and the temperature TB exceed the critical point, and the CO2 refrigerant will not be liquefied. The CO2 refrigerant sent from point B to the internal heat exchanger takes away heat from the CO2 refrigerant sent from the evaporator and reaches point C. The temperature changes from TB to TC, the pressure remains unchanged, that is, PB = PC, the specific enthalpy changes from EB to EC, the temperature TC is lower than the critical point, and part of the CO2 refrigerant is liquefied. The CO2 refrigerant fed into the variable expansion valve from point C is decompressed by the variable expansion valve and reaches point D. The temperature changes from TC to TD, the pressure changes from PC to PD, the specific enthalpy remains unchanged, that is, EC = ED, and the CO2 refrigerant becomes a mixture of gas and liquid. The CO2 refrigerant fed into the evaporator from point D takes energy from the processing fluid through the evaporator and reaches point E. The temperature and pressure remain unchanged, i.e., TD=TE, PD=PE, and the specific enthalpy changes from ED to EE. Point E approaches the saturated vapor line passing through the critical point, and the CO2 refrigerant becomes a gas. The CO2 refrigerant fed into the internal heat exchanger from point E takes heat from the CO2 refrigerant fed into the internal heat exchanger from point B. Although some liquid remains, it becomes gas and reaches point F. The temperature changes from TE to TF, the pressure remains unchanged, that is, PE=PF, and the specific enthalpy changes from EE to EF. When it reaches point A, the absolute value of the difference between EB and EC and the absolute value of the difference between EE and EF are equal. The controller follows Cooling efficiency = (ED-EE) / (EF-EA) The maximum way controls the temperature, pressure and specific enthalpy, where the cooling efficiency is cooling capacity / compression work.

7. The cooling mechanism according to claim 6, wherein: The temperature TA at point A is detected by the fourth temperature sensor. The temperature TB at point B is detected by the fifth temperature sensor. The temperature TC at point C is detected by the sixth temperature sensor. The temperature TD at point D is detected by the seventh temperature sensor. The temperature TE at the point E is detected by the seventh temperature sensor. The temperature TF at point F is detected by the eighth temperature sensor. The pressure PA at point A is detected by the second pressure sensor. The pressure PB at point B is detected by the second pressure sensor. The pressure PC at point C is detected by the second pressure sensor. The pressure PD at point D is detected by the first pressure sensor. The pressure PE at the point E is detected by the first pressure sensor. The pressure PF at point F is detected by the first pressure sensor. The specific enthalpy EA at point A is detected based on the pressure-specific enthalpy diagram. The specific enthalpy EB at point B is detected based on the pressure-specific enthalpy diagram. The specific enthalpy EC at point C is detected based on the pressure-specific enthalpy diagram. The specific enthalpy ED at point D is detected based on the pressure-specific enthalpy diagram. The specific enthalpy EE at point E is calculated by EF-(EB-EC), The specific enthalpy EF at point F is detected based on the pressure-specific enthalpy diagram. The controller is When calculating the cooling efficiency using the mathematical formula of cooling efficiency = (ED-EE) / (EF-EA), According to EC=ED and EE=EF-(EB-EC), Find ED-EE=EC-{EF-(EB-EC)}=EB-EF, By increasing the difference (EB-EF) between the specific enthalpy EB and the specific enthalpy EF, the cooling capacity and the cooling efficiency are improved, wherein the cooling efficiency is cooling capacity / compression work.

8. The cooling mechanism according to claim 1, wherein: The sixth temperature sensor and the seventh temperature sensor are omitted.

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