A super static precision air conditioning system

Abstract

The utility model discloses a super-static precision air conditioning system, which is composed of a vapor compression refrigeration cycle unit and a circulating air constant temperature and humidity processing circuit, and is used to provide precisely temperature-controlled circulating air to a thermal control object; it uses a precision measurement control unit to measure process parameters, control refrigeration compressor energy, control refrigerant condensation pressure, control refrigerant evaporation temperature and superheat, and super-static constant temperature control of circulating air, and can achieve ±10mK level temperature accuracy control of circulating air. The utility model is applied to the micro-environment air temperature, humidity, and cleanliness control of precision mechanical processing and precision measuring equipment such as photolithography machines, and has a strong ability to resist wide and frequent disturbances of thermal loads, so that the micro-environment air index of the controlled object can be stabilized at the set value within a short response time and maintained continuously.

Description

Technical Field

[0001] The utility model belongs to the technical field of refrigeration and air conditioning, and particularly relates to an ultra-static circulating air processing system with a temperature control accuracy of ±10mK level that meets the requirements of photolithography machine applications. Background Art

[0002] High-precision and high-stability temperature control is an important task in the research and development of high-end chip manufacturing equipment. Taking the control of lithography processing imaging quality as an example, the processing quality of nano-level lithography equipment is affected by factors such as temperature, pressure, and laser wavelength: temperature 4770nm / ℃, pressure 22.8nm / Mpa, and wavelength 470nm / pm. As the most temperature-sensitive components, projection lenses and laser interferometers not only have high requirements for internal single-point temperature accuracy, but also have extremely high requirements for the uniformity of their spatial temperature field. Temperature accuracy, spatial uniformity, and its drift over time will seriously affect the positioning accuracy and overlay accuracy of the lithography machine. In addition to the lithography machine, precise temperature control also directly affects the processing quality of other chip manufacturing equipment and processes. Temperature fluctuations during wafer growth will cause internal lattice structure inhomogeneity, resulting in an increase in the scrap rate of subsequent silicon wafer processing; the stability and consistency of temperature during photolithography coating and baking are necessary conditions to ensure uniform coating and photoresist performance; the uniformity of chip feature size and the contour control of side graphics in the etching process also require precise temperature control to ensure. High-precision and cutting-edge equipment in other industries also require ultra-static temperature control. In nanometer-level length measurement, the length change caused by the temperature of steel parts is 11500nm / ℃; the processing error caused by thermal deformation of machine tools in ultra-precision processing accounts for 40% to 70% of the total error; the fluctuations in the output wavelength and power of various laser generators and laser detectors are closely related to the accuracy and stability of the internal temperature of the laser, and the temperature stability of the optical path directly affects the accuracy of the test results. The core technology of ultra-static precision air-conditioning equipment is mainly in the precise adjustment of the cooling capacity of the refrigeration system and the precise control of the circulating air treatment process. However, for thermal control objects such as lithography equipment with large load fluctuations and large inertia and delay characteristics of thermal parameters, traditional air-conditioning refrigeration control, precise control of the heat exchange process of air, and precise temperature measurement technologies are in urgent need of technical breakthroughs. So far, there has been no public report on the relevant technology for high-end precision air-conditioning equipment with a temperature control accuracy of ±10mK. Utility Model Content

[0003] The utility model provides an ultra-static precision air conditioning system to avoid the above-mentioned deficiencies in the prior art and achieve the goal of circulating air supply temperature accuracy of ±10mK level.

[0004] The utility model adopts the following technical solutions to solve the technical problems:

[0005] The utility model ultra-static precision air-conditioning system is characterized in that it includes a vapor compression refrigeration cycle unit and a circulating air constant temperature and humidity treatment circuit; the vapor compression refrigeration cycle unit is composed of a refrigeration compressor, a condenser, an electronic expansion valve and an evaporator connected in sequence to form a closed loop; the evaporator is a fin-tube heat exchanger, or a parallel flow heat exchanger, and the refrigerant flowing through the channel in the tube evaporates and absorbs heat, which is used to cool the circulating air outside the tube; the flow rate of the cooling medium in the condenser is adjustable; the circulating air constant temperature and humidity treatment circuit is an open passage, and the circulating fan is arranged at the return air end of the air circulation channel, and a constant flow air circulation method is adopted; the circulating air returned from the user end is purified by a medium efficiency filter and a high efficiency filter in turn, and then enters the evaporator to release heat and cool down, and then is accurately temperature adjusted by a constant temperature regulator, and finally is transported to the user end through a cyclone.

[0006] The ultra-static precision air-conditioning system of the utility model is also characterized in that the condenser is an air-cooled condenser or a water-cooled condenser, the condensing fan of the air-cooled condenser is equipped with a variable frequency motor, and the condensing water pump of the water-cooled condenser is equipped with a variable frequency motor.

[0007] The utility model ultra-static precision air conditioning system is also characterized in that: the sensors include: sensors for detecting and obtaining the compressor return air temperature T respectively arranged on the refrigerant return air channel at the evaporator outlet; 11 The first temperature sensor T1 is used to detect the refrigerant evaporation pressure P 0 A first pressure sensor P1 is provided on the refrigerant liquid channel between the condenser and the electronic expansion valve for detecting the refrigerant temperature T at the condenser outlet. 22 The second temperature sensor T2 is used to detect the refrigerant condensing pressure P k A second pressure sensor P2 is provided on the circulating air outlet channel in the evaporator for detecting the circulating air temperature T after the evaporator is cooled once. 33 The third temperature sensor T3; respectively provided at the outlet of the cyclone for detecting the relative humidity of the circulating air Φ 44 The humidity sensor Φ4 is used to detect the circulating air temperature T 44 A fourth temperature sensor T4 is provided on the return air inlet channel of the circulating air for detecting the return air temperature T of the circulating air; 55 The fifth temperature sensor T5.

[0008] Compared with the existing technology, the beneficial effects of the utility model are embodied in:

[0009] 1. The utility model is provided with an ultra-static precision temperature control technology framework for secondary temperature adjustment of circulating air that is resistant to strong interference dynamic heat load; a vapor compression refrigeration system that can accurately adjust the refrigeration cycle process parameters and the refrigeration capacity is provided, and the temperature control accuracy of the primary adjustment of the circulating air is ±0.1K; a thermostat that can accurately fine-tune the energy is provided, and the temperature accuracy of the secondary adjustment of the circulating air is ±10mK, which meets the temperature accuracy and stability requirements of the nm-level lithography machine.

[0010] 2. The utility model sets a cyclone before the circulating air temperature sensor in the air supply channel, and uses the air flow velocity as the power to spin and stir the air to equalize the temperature, thereby eliminating the radial temperature gradient of the temperature measurement point, improving the accuracy of the supply air temperature measurement, and providing the necessary conditions for the precise adjustment of the thermostat. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the system flow of the utility model;

[0012] Numbers in the figure: 1 refrigeration compressor, 2 condenser, 3 electronic expansion valve, 4 evaporator, 5 circulation fan, 6 medium efficiency filter, 7 high efficiency filter, 8 thermostat, 9 cyclone. DETAILED DESCRIPTION

[0013] See also Figure 1 , the ultra-static precision air conditioning system in this embodiment is composed of a vapor compression refrigeration cycle unit, a circulating air constant temperature and humidity processing circuit and a precision measurement control unit, and is used to provide circulating air with precision temperature control to the thermal control object;

[0014] like Figure 1 As shown, the vapor compression refrigeration cycle unit is composed of a refrigeration compressor 1, a condenser 2, an electronic expansion valve 3 and an evaporator 4 connected in sequence to form a closed loop; the evaporator 4 is a finned tube heat exchanger, or a parallel flow heat exchanger, and the refrigerant flowing through the channel in the tube evaporates and absorbs heat, which is used to cool the circulating air outside the tube; the condenser 2 is an air-cooled condenser or a water-cooled condenser, and the cooling medium flow of the condenser 2 is adjustable. The condensing fan of the air-cooled condenser is equipped with a variable frequency motor, and the condensing water pump of the water-cooled condenser is equipped with a variable frequency motor; the circulating air constant temperature and humidity treatment circuit is an open passage, and the circulating The circulating fan 5 is arranged at the return air end of the air circulation channel, and adopts a constant flow air circulation method; the circulating air returned from the user end is purified by the medium efficiency filter 6 and the high efficiency filter 7, and then enters the evaporator 4 to release heat and cool down, and then is precisely temperature adjusted by the thermostat 8, and finally delivered to the user end through the cyclone 9; the precision measurement control unit achieves the control of the circulating air temperature accuracy of ±10mK through process parameter measurement, refrigeration compressor energy control, refrigerant condensation pressure control, refrigerant evaporation temperature and superheat control, and circulating air ultra-static constant temperature control.

[0015] In this embodiment, when the ultra-static precision air conditioner is used for microenvironment control in the lithography machine, the circulating fan 5 needs a large pressure head, requiring the static pressure of the air supply outlet to be no less than 200Pa. The power of the circulating fan is relatively large relative to the cooling capacity of the air conditioner. The advantage of setting the circulating fan in the return air channel of the air circulation is: using the mechanical refrigeration system to balance the heat load of the circulating fan in advance, reducing the disturbance of the circulating fan power fluctuation on the circulating air supply temperature.

[0016] In this embodiment, the process parameter measurement refers to setting each sensor in the following form and realizing the process parameter measurement:

[0017] A first temperature sensor T1 and a first pressure sensor P1 are respectively arranged on the refrigerant return air channel at the outlet of the evaporator 4, and the compressor return air temperature T is obtained by detecting the first temperature sensor T1. 11 , the refrigerant evaporation pressure P is detected by the first pressure sensor P1 0 , according to the refrigerant evaporation pressure P 0 Get the refrigerant evaporation temperature T 0 , refrigerant evaporation temperature T 0 It refers to the refrigerant evaporation pressure P 0 The corresponding refrigerant saturation temperature T 0 ; Calculate the refrigerant vapor superheat T at the outlet side of the evaporator 4 110 =T 110 =T 11 -T 0 .

[0018] A second temperature sensor T2 and a second pressure sensor P2 are arranged on the refrigerant liquid channel between the condenser 2 and the electronic expansion valve 3. The second temperature sensor T2 is used to detect the refrigerant temperature T at the condenser outlet. 22 , the refrigerant condensation pressure P is detected by the second pressure sensor P2 k , according to the refrigerant condensation pressure P k Get the refrigerant condensation temperature T k , refrigerant condensation temperature T k It refers to the refrigerant condensation pressure P k Corresponding refrigerant saturation temperature; Calculate the refrigerant subcooling T on the outlet side of the air-cooled condenser 2 k22 =T k22 =T k -T 22 .

[0019] A third temperature sensor T3 is provided on the circulating air outlet channel in the evaporator 4. The third temperature sensor T3 detects the temperature at the corresponding position, which is the circulating air temperature T after the evaporator 4 cools down once. 33 .

[0020] A humidity sensor Φ4 and a fourth temperature sensor T4 are respectively provided at the outlet of the cyclone 9 to detect the relative humidity Φ of the circulating air. 44 and circulating air temperature T 44 The fourth temperature sensor T4 is located after the cyclone 9, and the distance between the two is not less than 2 times the hydraulic radius of the air duct. In the air supply channel, the cyclone is driven by the airflow to spin, stir the air and even the temperature, and even the airflow temperature in the cross-sectional direction of the circulating air supply channel is uniform, eliminating the radial temperature gradient of the air duct, thereby improving the accuracy of the air supply temperature T4 measurement and providing the necessary conditions for the precise adjustment of the thermostat.

[0021] A fifth temperature sensor T5 is provided on the return air inlet passage of the circulating air to detect the temperature at the corresponding position, which is the return air temperature T of the circulating air. 55 .

[0022] The control method for setting the energy control of the refrigeration compressor in this embodiment is:

[0023] The refrigeration compressor energy controller is controlled by feedback control and feedforward control, and is controlled according to the fuzzy adaptive control strategy, including: 33 The refrigeration compressor energy controller is used to adjust the input current frequency of the refrigeration compressor 1 so that the circulating air return temperature T 33 Reach the temperature target value T 33 '; Set the temperature target value T 33 ' is: T 33 '=TE-0.1, TE is the supply air temperature setting value. (TE-0.1) is used as the temperature target value, the purpose is to make the evaporator after T 3 The temperature range is (TE≥T 3 ≥TE-0.2), that is, T 3 ≤TE, the subsequent thermostat 8 only needs a heating function, and an electric heater with a precision power supply can be used, which has a simple structure and low cost; otherwise, if T 3 ≥TE, the thermostat 8 needs to be provided with a cold source and a heat source, that is, a semiconductor thermal pile equipped with a precision power supply is adopted, which greatly increases the manufacturing cost and complexity of the product compared with the former.

[0024] Set the feedback control input signal of the refrigeration compressor energy controller to the circulating air temperature deviation value dT 33 And the circulating air return temperature change rate dT 33 / dt,dT 33 =T 33 -T 33 '.

[0025] Set the feedforward control input signal T of the refrigeration compressor energy controller 55 -T 55 * , T 55 is the real-time measurement value of the circulating air return temperature, T 55 * is the return air temperature of the circulating air in the last measurement cycle. When applied to a certain thermal control object, based on a constant flow circulating fan and a certain flow resistance, the flow fluctuation of the circulating air can be ignored, and the return air temperature difference between the last two measurements (T 55 -T 55 * ) to replace the heat load fluctuation of the thermal control object, and adopt (T 55 -T 55 * ) is used as the feedforward input signal of the refrigeration compressor energy controller, which can quickly adjust the operating frequency of the refrigeration compressor and quickly suppress the fluctuation of the heat load of the controlled object.

[0026] This embodiment adopts a technical solution of constant flow air supply, large flow, small temperature difference heat exchange, and circulating air supply and return air design temperature difference ≤ 2K; the (T 55 -T 55 * ) is used as the feedforward control input signal of the controller. A fuzzy adaptive control strategy with feedforward and feedback is adopted to accurately adjust the energy output of the refrigeration compressor, improve the system response speed and the ability to suppress frequent and wide fluctuations in heat load. The step size of the input frequency of the refrigeration compressor is set to 0.2 Hz.

[0027] The control method for setting the refrigerant condensing pressure control is:

[0028] The deviation value of the refrigerant condensing pressure dP k As the input signal of the condensing pressure controller, PID regulation is used to suppress the fluctuation of condensing pressure. By adjusting the input current frequency of the variable frequency condensing fan in the air-cooled condenser, or by adjusting the input current frequency of the variable frequency condensing water pump in the water-cooled condenser, the refrigerant condensing pressure reaches the steady-state value P kw , dP k =P k -P kw , and satisfy T k22 Not less than 5 to ensure the stable operation of the electronic expansion valve. Condensation pressure determination and control: Condensation pressure control is achieved by adjusting the cooling medium flow of the condenser. The actuator of the air-cooled condenser is the variable frequency condensing fan, and the actuator of the water-cooled condenser is the variable frequency cooling water pump. The input signal of the variable frequency controller is the condensation pressure P k With its steady-state value P kw Deviation dP k, use PID regulator to control the working frequency of the inverter to suppress the fluctuation of condensing pressure. For a certain refrigeration system, that is, the refrigeration compressor characteristic curve is known, the condenser structure size is determined, the electronic expansion valve characteristic curve is known, and the suction pressure and temperature of the refrigeration compressor are relatively stable, the condensing pressure of the refrigeration system operation is mainly related to the temperature and flow rate of the cooling medium; under the condition of ensuring the reliable and stable operation of the expansion valve, the lower the condensing pressure, the higher the operating efficiency of the refrigeration system. A reasonable condensing pressure variation range can be obtained through theoretical calculation or experimental research, so a better value P can be selected from it. kw As P k By controlling the cooling medium flow rate of the condenser, the condensing pressure is controlled to be stable near the optimal value. By giving learning ability to the intelligent control system, the underlying data and experience can be accumulated, and the steady-state value P of the condensing pressure in the real-time working state can be obtained through iterative optimization. kw .

[0029] The control method for setting the refrigerant evaporation temperature and superheat control is:

[0030] On the basis of stable condensing pressure, the superheat of refrigerant at the evaporator outlet is accurately controlled to achieve indirect control of evaporation temperature, with the deviation value dT of refrigerant vapor superheat 110 and its rate of change dT 110 / dt is used as the input signal of the evaporation temperature controller, which uses the fuzzy adaptive control strategy to adjust the opening of the electronic expansion valve 3 to achieve the refrigerant evaporation temperature control, where: dT 110 =T 110 -TG, TG is the setting value of the refrigerant vapor superheat. This embodiment adopts constant flow air supply, large flow, small temperature difference heat transfer, the maximum design temperature difference between supply and return air is 2K, and the supply air temperature accuracy is ±10mk level. Therefore, the design evaporation temperature is (TE-△T). The smaller the setting value of △T, the smaller the average heat transfer temperature difference, and T 3 The smaller the deviation is, the larger the evaporator heat exchange area is required, resulting in high manufacturing cost and large volume of the evaporator. Regardless of cost or small size and light weight, the value of △T cannot be very small. It is recommended that the value range of △T is 1~3K and the value range of TG is 0.3~1K.

[0031] The control method for setting the circulating air ultra-static constant temperature control is:

[0032] The fuzzy adaptive control strategy is adopted to 44 and its rate of change dT 44 / dt controls the power supply parameters of the thermostat 8 to achieve ultra-static constant temperature control of circulating air; where: dT 44 =T 44-TE; The thermostat 8 is a thermostat composed of an electric heater and a precision power supply, or a thermostat composed of a semiconductor thermal pile and a precision power supply. For ultra-static precision air conditioners used in precision processing equipment such as lithography machines, they usually work in a constant temperature and humidity working environment, and the thermostat 8 does not need to be configured with a large energy level; if it is an ultra-static precision air conditioner used in an uncontrolled working environment, the thermostat 8 needs to have a large energy level, that is, a hierarchically managed electric heater is used to meet the needs of startup heating and heating after dehumidification.

[0033] The application of the ultra-static precision air conditioning system in this embodiment is to set the system to work in any of the following modes:

[0034] Mode 1: It is a dehumidification and purification working mode, the circulating fan 5 is running, and the vapor compression refrigeration cycle unit is running in the dehumidification condition.

[0035] Mode 2: It is a heating and purification working mode, the circulating fan 5 is running, the thermostat 8 is started, and the vapor compression refrigeration cycle unit stops running.

[0036] Mode 3: It is a cooling and purification working mode, the circulating fan 5 is running, the thermostat 8 is started, and the vapor compression refrigeration cycle unit is running.

[0037] The ultra-static precision air-conditioning system of the utility model is particularly used for the micro-environment temperature control of precision mechanical processing and precision measuring equipment such as nm-level photolithography machines. It consists of a vapor compression refrigeration cycle unit, a circulating air constant temperature and humidity treatment circuit, and a precision measurement control system, and provides circulating air with a temperature accuracy of ±10mK to the thermal control object.

[0038] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention. Some conventional functional components are omitted without affecting the understanding of the basic functions and structures, such as the flow switch of the liquid supply pump, the drying filter, the sight glass, the gas-liquid separator, etc. Therefore, it is not used to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-static precision air conditioning system, characterized by: The system comprises a vapor compression refrigeration cycle unit and a circulating air constant temperature and humidity treatment circuit; the vapor compression refrigeration cycle unit comprises a refrigeration compressor (1), a condenser (2), an electronic expansion valve (3) and an evaporator (4) which are connected in sequence to form a closed loop; the evaporator (4) is a finned tube heat exchanger or a parallel flow heat exchanger, and the refrigerant flowing through the tube channel evaporates and absorbs heat, which is used to cool the circulating air outside the tube; the flow rate of the cooling medium in the condenser (2) is adjustable; the circulating air constant temperature and humidity treatment circuit is an open passage, and the circulating fan (5) is arranged at the return air end of the air circulation channel, and a fixed flow air circulation method is adopted; the circulating air returned from the user end is successively purified by a medium efficiency filter (6) and a high efficiency filter (7), then enters the evaporator (4) to release heat and cool down, and then is accurately temperature-regulated by a thermostat (8), and finally is transported to the user end through a cyclone (9).

2. The ultra-static precision air conditioning system according to claim 1 is characterized in that: The condenser (2) is an air-cooled condenser or a water-cooled condenser. The condensing fan of the air-cooled condenser is equipped with a variable frequency motor, and the condensing water pump of the water-cooled condenser is equipped with a variable frequency motor.

3. The ultra-static precision air conditioning system according to claim 1 is characterized in that: The arrangement of sensors comprises: respectively arranging sensors on the refrigerant return air passage at the outlet of the evaporator (4) for detecting and obtaining the compressor return air temperature (T 11 ) and a first temperature sensor (T1) for detecting and obtaining the refrigerant evaporation pressure (P0); and a first pressure sensor (P1) for detecting and obtaining the refrigerant temperature (T0) at the condenser outlet are respectively provided on the refrigerant liquid channel between the condenser (2) and the electronic expansion valve (3). 22 ) and a second temperature sensor (T2) for detecting the refrigerant condensing pressure (P k ) a second pressure sensor (P2); a circulating air outlet passage in the evaporator (4) is provided for detecting the circulating air temperature (T 33 ) of the third temperature sensor (T3); respectively provided at the outlet of the cyclone (9) for detecting the relative humidity of the circulating air (Φ 44 ) and a humidity sensor (Φ4) for detecting the circulating air temperature (T 44 ) of the fourth temperature sensor (T4); a temperature sensor for detecting the return air temperature of the circulating air (T 55 ) of the fifth temperature sensor (T5).

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