JP2009058199A - Cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device capable of quickly coping with a case where a liquid temperature is extremely lowered, improving safety and reliability and being easily mounted afterwards. <P>SOLUTION: This cooling device comprises a refrigerating cycle Cc constituted by connecting an invertor-controlled compressor 2, a condenser 3, an expansion valve 4 and a heat exchanger 5 and circulating a refrigerant, and a cooling liquid circuit Cm for cooling the cooling liquid W supplied from a cooling liquid tank 6 by heat exchange with a refrigerant by being connected with the heat exchanger 5, circulating the cooling liquid W to a cooled object H and returning the same to the cooling liquid tank 6, and further comprises a heater 8 disposed in the cooling liquid tank 6 for heating the cooling liquid W received in the cooling liquid tank 6, and a control portion 7 having a control function for switching on the heater 8 when at least a liquid temperature Tw reaches a predetermined underload temperature or less, and switching off the heater 8 when the liquid temperature Tw reaches a predetermined non-underload temperature or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cooling device that cools a coolant supplied from a coolant tank using a refrigeration cycle that circulates a refrigerant.

  In general, in a laser processing machine, the load on the laser side varies greatly depending on the material of the workpiece, the plate thickness, the processing speed, the processed surface roughness, and the like. Therefore, the cooling device that supplies (circulates) the coolant to the laser processing machine is required to have a cooling performance that can sufficiently follow such load fluctuations, and in particular, such as a mirror that greatly affects the processing accuracy. In order to ensure the thermal stability of the optical parts and avoid the deterioration of the processing quality, a high degree of precision cooling accuracy with little temperature fluctuation is required.

  Conventionally, a cooling device disclosed in Patent Document 1 is known as a cooling device used for such applications. The cooling device includes a cooling liquid tank that stores a cooling liquid returned from an object to be cooled such as a laser processing machine, a liquid feeding pump that sends out a cooling liquid flowing out from a supply port of the cooling liquid tank, and a liquid feeding pump. It is equipped with a cooler (heat exchanger) that cools the coolant discharged from the pump by heat exchange and supplies it to the object to be cooled, and detects the temperature of the coolant that has flowed out of the cooler with a temperature sensor. Based on the control system for controlling the cooling temperature of the cooler based on the temperature, more specifically, based on the temperature detected by the temperature sensor, the rotation frequency (rotation speed) of the compressor in the refrigeration cycle for circulating the refrigerant to the cooler is an inverter. A control system having a control function to control is provided.

By the way, since the inverter control of the compressor variably controls the rotation speed of the compressor by a control signal given to the inverter circuit from the control unit, there is a limit to the range of the rotation speed that can be controlled, and usually the number of the maximum cooling capacity In the underload region of 10% or less, inverter control becomes difficult. For this reason, a cooling device corresponding to an underload region is also known from Patent Document 2. This cooling device controls the temperature (water temperature) of the object to be cooled by changing the rotation speed of the compressor constituting the refrigeration cycle within a certain range by the inverter, and if the water temperature is lowered to a temperature that cannot be controlled by the inverter. , Control to open the hot gas bypass circuit, especially if the water temperature rises with the hot gas bypass circuit open, increase the compressor speed with the hot gas bypass circuit open and When the number reaches a preset number of rotations, the hot gas bypass circuit is closed, and a control function is provided for performing control to reduce the number of rotations of the compressor.
JP 2003-329355 A JP 2001-74318 A

  However, the conventional cooling device corresponding to the above-described underload region has the following problems to be solved.

  First, the hot gas bypass circuit cannot reduce the cooling capacity to less than zero because it is a measure for reducing the cooling capacity of the cooling device for the underload region. Therefore, it may not be possible to cope with the case where the liquid temperature (water temperature) is greatly reduced due to restrictions on the operation of the compressor, disturbances other than the cooling device, etc., which is not necessarily sufficient in safety and reliability. It's hard to say.

  Second, underload countermeasures are not absolutely necessary, but are necessary in environments where underload occurs. Therefore, when it is prepared as an option from the viewpoint of cost, such as a small cooling device, when installing the hot gas bypass circuit, the connection of the circuit constituting the refrigeration cycle is changed, which makes installation work very difficult. In addition, an arrangement space (dead space) needs to be secured in advance.

  The object of the present invention is to provide a cooling device that solves the problems in the background art.

  In order to solve the above-mentioned problems, the present invention connects at least the compressor 2, the condenser 3, the expansion valve 4, and the heat exchanger 5 that are inverter-controlled to circulate the refrigerant and the heat exchanger. 5, the coolant W supplied from the coolant tank 6 is cooled by heat exchange with the refrigerant, and the coolant W is circulated to the object H to be cooled, and then returned to the coolant tank 6. A cooling device that includes a circuit Cm and a control unit 7 that detects the liquid temperature Tw of the cooling liquid W and controls the rotational speed R of the compressor 2 so that the detected liquid temperature Tw becomes a preset liquid temperature Twc. 1, a heater 8 capable of heating the cooling liquid W accommodated in the cooling liquid tank 6 by being disposed in the cooling liquid tank 6, and at least the liquid temperature Tw is equal to or lower than a preset underload temperature Twds If it becomes, heater 8 And to ON, and the liquid temperature Tw, characterized in that is comprises a control unit 7 having a control function of the heater 8 is turned OFF if equal to or more than the non-under-load temperature Twus previously set.

  In this case, according to a preferred aspect of the present invention, the control for turning off the heater 8 is performed when the liquid temperature Tw is equal to or higher than the non-under-load temperature Twus and the rotation speed Rcs of the compressor 2 is set in advance. It can be performed on condition that both of the above are satisfied. Further, the monitored rotational speed Rcs can be set to a rotational speed that is smaller than the maximum operable rotational speed Rmax of the compressor 2 by a predetermined rotational speed Ros. Furthermore, the underload temperature Twds can be set to a temperature that is lower than the set liquid temperature Twc by a predetermined temperature amount Tods, and the non-underload temperature Ttws is a temperature that is higher than the set liquid temperature Twc by a predetermined temperature portion Tous Can be set.

  According to the cooling device 1 according to the present invention having such a configuration, the following remarkable effects can be obtained.

  (1) The cooling liquid W accommodated in the cooling liquid tank 6 can be forcibly heated by the heater 8, that is, the load can be forcibly increased. For example, even when the liquid temperature Tw is greatly reduced due to the above, it is possible to respond quickly and contribute to improvement in safety and reliability. Further, since liquid temperature control is performed by combining ON / OFF of the heater 8 and inverter control of the compressor 2, it is not necessary to keep the heater 8 ON at all, which can contribute to energy saving.

  (2) Since the heater 8 capable of heating the coolant W accommodated in the coolant tank 6 is used by being disposed in the coolant tank 6, even if it is prepared as an option from the viewpoint of cost, It can be easily retrofitted, and an arrangement space (dead space) prepared in advance in the circuit of the refrigeration cycle Cc becomes unnecessary.

  (3) According to a preferred embodiment, the control for turning off the heater 8 is performed when the liquid temperature Tw is equal to or higher than the non-underload temperature Twus and the rotational speed R of the compressor 2 is equal to or higher than a preset monitored rotational speed Rcs. If both conditions are satisfied, when the heater 8 is turned off, more precise and accurate control can be performed by combining the non-underload temperature Twus and the monitored rotational speed Rcs of the compressor 2. it can.

  (4) According to a preferred embodiment, if the underload temperature Twds is set to a temperature lower than the set liquid temperature Twc by a predetermined temperature amount Tods, when setting the underload temperature Twds, the set liquid temperature Twc, It is possible to easily set an accurate underload temperature Twds in consideration of the differential lower limit temperature in the control of the set liquid temperature Tw.

  (5) According to a preferred embodiment, if the non-underload temperature Twus is set to a temperature that is higher than the set liquid temperature Twc by a predetermined temperature portion Tous, the set liquid temperature Twc, In particular, it is possible to easily set an accurate non-underload temperature Twus in consideration of the differential upper limit temperature in the control of the set liquid temperature Tw.

  Next, the best embodiment according to the present invention will be given and described in detail with reference to the drawings.

  First, the configuration of the cooling device 1 according to the present embodiment will be specifically described with reference to FIGS. 1 and 2.

  FIG. 1 shows the overall configuration of the cooling device 1. The cooling device 1 includes a heat exchanger (cooler) 5, and a refrigeration cycle Cc is connected to the primary side 5 f of the heat exchanger 5, and a coolant circuit Cm is connected to the secondary side 5 s of the heat exchanger 5. To do.

  FIG. 2 shows a specific example of the coolant circuit Cm. The coolant circuit Cm includes a coolant tank 6 that stores coolant (cooling water, cooling solution, etc.) W. The illustrated coolant tank 6 has a volume of 15 [liter] and is connected to an object to be cooled H (FIG. 1) such as a laser processing machine via a coolant supply line 12s and a coolant return line 12r. In the middle of the coolant supply line 12 s, a liquid feed pump 13 for supplying the coolant W stored in the coolant tank 6 to the object to be cooled H is connected, and heat is supplied to the liquid feed pump 13. The secondary side 5s of the exchanger 5 is connected in series. The coolant tank 6 includes a tank cover 6c that covers the upper end opening, and a heater 8 that is used at the time of underload is attached to the tank cover 6c. The heater 8 projects downward from the inner surface of the tank cover 6 c and is immersed in the coolant W accommodated in the coolant tank 6. The illustrated heater 8 is a 1.5 [kW] electric heater in which a heating wire is covered with a waterproof housing. Further, the coolant supply line 12s is provided with a fluid pressure gauge 15 for detecting the pressure of the coolant W and a liquid temperature sensor 16 for detecting the temperature (liquid temperature) Tw of the coolant W, and the coolant tank 6 has A liquid supply port 17, a drain line 18, a float switch 19, a liquid level gauge 20, a strainer 21 and the like are provided.

  On the other hand, the refrigeration cycle Cc includes a compressor 2, a condenser 3, and an expansion valve (electronic expansion valve) 4 as main functional units, and the refrigerant outflow side of the electronic expansion valve 4 is the primary side of the heat exchanger 5. The other end port (refrigerant outlet port) of the primary side 5 f of the heat exchanger 5 is connected to the refrigerant inflow side of the compressor 2 via the refrigerant strainer 31. Thereby, a refrigeration cycle Cc (refrigerant circuit) in which the refrigerant circulates in the direction of arrow Fc is configured. The basic function of such a refrigeration cycle Cc is the same as a known refrigeration cycle. In the refrigeration cycle Cc, the temperature of the refrigerant discharged from the compressor 2, that is, the discharge refrigerant temperature sensor 33 that detects the discharged refrigerant temperature To, and the temperature of the refrigerant discharged from the condenser 3, that is, the condensed refrigerant temperature Tc are set. Various sensors such as a condensing refrigerant temperature sensor 34 to be detected and a cooler inlet temperature sensor 35 to detect the refrigerant temperature on the inlet side of the cooler 5 are attached, and the condenser 3 is air-cooled. A fan 36 is attached. An arrow Ff indicates the direction of air blown by the condenser fan 36. Further, an electric motor 41 is used to drive the compressor 2, and the electric motor 41 is connected to the inverter unit 42. The illustrated electric motor 41 is a sensorless brushless DC motor that operates by a 120 ° energization method, and includes three star-connected windings (field coils). The inverter unit 42 includes an inverter circuit 42i and a DC power supply circuit 42s. The output unit of the inverter circuit 42i is connected to the electric motor 41, and the AC input unit of the DC power supply circuit 42s is connected to a three-phase AC power supply.

  The sensors 33, 34, 35, the condenser fan 36, the inverter circuit 42 i, the electronic expansion valve 4, the liquid temperature sensor 16, and the heater 8 are each connected to a control unit (controller) 7. The control part 7 comprises the principal part of a control system, and has a function which manages control of the whole cooling device 1 containing the refrigerating cycle Cc. Further, a current detector 43 for detecting the magnitude of the inverter input current Ii flowing from the DC power supply circuit 42s to the inverter circuit 42i is provided between the inverter circuit 42i and the DC power supply circuit 42s, and this current detector 43 is controlled. Connect to unit 7. The control unit 7 includes an operation unit using an operation panel and a display unit using a liquid crystal display panel and the like, and has a computer function including a CPU and a memory, and performs various processes and controls according to a control program stored in advance. (Sequence control) is executed.

  Next, operation | movement of the cooling device 1 which concerns on this embodiment is demonstrated according to the flowchart shown in FIG. 4, referring FIGS. 1-3.

  First, in the control unit 7, the underload temperature Twds with respect to the liquid temperature Tw of the coolant W that determines that the underload state is in advance, and the non-underload temperature Twus with respect to the liquid temperature Tw that determines that the underload state has been removed. And the monitoring rotational speed Rcs for the rotational speed R of the compressor 2 are set.

  In the example, the underload temperature Twds is set to a temperature lower by a predetermined temperature Tods (for example, 1.0 [° C.]) than the set liquid temperature Twc. That is, Twds = Twc−Tods [° C.]. The set liquid temperature Twc relative to the liquid temperature Tw is set on the user side. Therefore, if the set liquid temperature Twc is set to 20 [° C.] and Tods is 1.0 [° C.], the underload temperature Twds is 19 [° C.]. Normally, the control differential with respect to the liquid temperature Tw is about Twc ± 0.5 [° C.] with respect to the set liquid temperature Twc, so that the liquid temperature Tw can be equal to or lower than Twds (Twc-Tods [° C.]). Thus, it can be determined that the state is an underload state. By setting the underload temperature Twds in this way, there is an advantage that an accurate underload temperature Twds can be easily set in consideration of the differential lower limit temperature in the control of the set liquid temperature Tw.

  Further, the non-underload temperature Twus is set to a temperature that is higher than the set liquid temperature Twc by a predetermined temperature Tous (for example, 1.0 [° C.]). That is, Twus = Twc + Tous [° C.] is set. Therefore, if the set liquid temperature Twc is set to 20 [° C.] and Tous is 1.0 [° C.], the non-underload temperature Twus is 21 [° C.]. As described above, since the control differential for the liquid temperature Tw is normally about Twc ± 0.5 [° C.] with respect to the set liquid temperature Twc, at least the liquid temperature Tw is Twus (Twc + Tous [° C.]. ) If this is the case, it can be determined that the underload state has been removed. By setting the non-underload temperature Twus in this way, there is an advantage that an accurate non-underload temperature Twus can be easily set in consideration of the differential upper limit temperature in the control of the set liquid temperature Tw. Further, the monitored rotational speed Rcs is set to a rotational speed that is smaller than the maximum operable rotational speed Rmax of the compressor 2 by a predetermined rotational speed Ros (for example, 50 [rpm]). That is, Rcs = Rmax−Ros [rpm] is set.

  On the other hand, the control unit 7 executes the following control during operation. Now, it is assumed that the cooling device 1 is in a normal load state that is not an underload state, and feedback control for the liquid temperature Tw is normally performed (steps S1 and S2). In this case, the heater 8 is OFF and the heater 8 is not energized. In the coolant circuit Cm, the coolant W stored in the coolant tank 6 is supplied to the object to be cooled H via the coolant supply line 12s by the operation of the liquid feed pump 13, and the object to be cooled H The coolant W cooled by heat exchange is returned to the coolant tank 6 via the coolant return line 12r. At this time, the coolant W flowing through the coolant supply line 12 s is cooled by the cooler (heat exchanger) 5. That is, the coolant W flowing into the cooler 5 is cooled by heat exchange with the cooled refrigerant in the refrigeration cycle Cc. In the refrigeration cycle Cc, the refrigerant circulates in the direction of the arrow Fc by the operation of the compressor 2, and the refrigerant is cooled by the refrigeration cycle Cc. In FIG. 2, arrows Fw... Indicate the direction in which the coolant W flows.

  Then, the liquid temperature Tw of the cooling liquid W supplied to the object to be cooled H is detected by the liquid temperature sensor 16 and applied to the control unit 7. As a result, the control unit 7 gives a control command to the inverter circuit 42i and varies the rotation speed R of the electric motor 41, thereby performing the foot-back control so that the liquid temperature Tw becomes the preset liquid temperature Twc. At this time, a DC voltage is applied from the DC power supply circuit 42s to the input part of the inverter circuit 42i, and the inverter circuit 42i executes a known inverter control for switching the DC voltage by an internal switching element. In a normal load state, the control differential with respect to the liquid temperature Tw is Twc ± 0.5 [° C.] with respect to the set liquid temperature Twc.

  On the other hand, it is assumed that the cooling device 1 is in an underload state. That is, it is assumed that the liquid temperature Tw of the cooling liquid W decreases and becomes equal to or lower than the set underload temperature Twds (Tw ≦ Twc−Tods [° C.]) (steps S3 and S4). In FIG. 4, the time when th1 becomes lower than the underload temperature Twds is shown. Thereby, the heater 8 is turned ON and the coolant W is heated by the heater 8 (step S5). As the heater 8 is turned on, the liquid temperature Tw of the coolant W gradually rises, so that the load is forcibly increased.

  On the other hand, it is assumed that the liquid temperature Tw rises and becomes equal to or higher than the set non-underload temperature Twus (Tw ≧ Twc + Tous [° C.]) (steps S6 and S7). In FIG. 4, th2 indicates a time point when the temperature becomes equal to or higher than the non-underload temperature Twus. In this case, the control unit 7 takes in the rotational speed R of the compressor 2 and determines whether or not the rotational speed R is equal to or higher than the set monitoring rotational speed Rcs (R ≧ Rmax−Ros [rpm]). When the monitored rotational speed Rcs is equal to or higher, that is, both the liquid temperature Tw is equal to or higher than the non-underload temperature Twus and the rotational speed R of the compressor 2 is equal to or higher than a preset monitored rotational speed Rcs. If the condition is satisfied, the heater 8 is turned off (steps S8 and S9). By performing such control, there is an advantage that more precise and accurate control can be performed by combining the non-underload temperature Twis and the monitored rotation speed Rcs of the compressor 2 when the heater 8 is turned off.

  Therefore, according to the cooling device 1 according to this embodiment, the coolant W stored in the coolant tank 6 can be forcibly heated by the heater 8, that is, the load can be forcibly increased. Even if the liquid temperature Tw is greatly reduced due to the operational restrictions of the system, disturbances other than the cooling device 1, etc., it is possible to respond quickly and contribute to the improvement of safety and reliability. . Further, since liquid temperature control is performed by combining ON / OFF of the heater 8 and inverter control of the compressor 2, it is not necessary to keep the heater 8 ON at all, which can contribute to energy saving. Further, since the heater 8 capable of heating the coolant W accommodated in the coolant tank 6 is used by being disposed in the coolant tank 6, it is easy even if it is prepared as an option from the viewpoint of cost. In addition, an arrangement space (dead space) prepared in advance in the circuit of the refrigeration cycle Cc becomes unnecessary.

  Although the best embodiment has been described in detail above, the present invention is not limited to such an embodiment, and the detailed configuration, method, quantity, numerical value, and the like do not depart from the spirit of the present invention. You can change, add, or delete at will. For example, the heater 8 is shown attached to the tank cover 6c, but may be attached to the coolant tank 6. Moreover, the heater 8 may be assembled in advance as standard equipment, or may be retrofitted as an option. Furthermore, the type and shape of the heater 8 are not limited to examples, and various heaters can be used. In addition, although the electric motor 41 illustrated the direct current motor, it may be an alternating current motor, the kind is not ask | required, and the inverter circuit 42i (inverter unit 42) can also be comprised by the various types which have the same function. In addition, although the type shown in FIG. 1 (FIG. 2) was illustrated as the cooling device 1, the cooling device according to the present invention can be similarly applied to various types of cooling devices other than those illustrated.

The whole block diagram of the cooling device concerning the best embodiment of the present invention, Configuration diagram of a coolant circuit in the cooling device, A flowchart showing a processing procedure during operation of the cooling device, A timing chart showing the state of each part during operation of the cooling device;

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1: Cooling device, 2: Compressor, 3: Condenser, 4: Expansion valve, 5: Heat exchanger, 6: Coolant tank, 7: Control part, 8: Heater, Cc: Refrigeration cycle, Cm: Coolant Circuit, W: Coolant, H: Object to be cooled, Tw: Liquid temperature of coolant, Twc: Set liquid temperature, Twds: Underload temperature, Twis: Non-underload temperature, Tods: Predetermined temperature, Tous: Predetermined R: Compressor speed, Rcs: Monitored speed, Rmax: Maximum operating speed, Ros: Predetermined speed

Claims (5)

  At least a compressor, a condenser, an expansion valve, and a heat exchanger that are inverter-controlled to connect a refrigeration cycle that circulates the refrigerant, and from the coolant tank by heat exchange with the refrigerant by connecting to the heat exchanger After cooling the supplied coolant and circulating the cooled coolant to the object to be cooled, the coolant circuit returning to the coolant tank and the coolant temperature are detected. In a cooling device including a control unit that controls the number of rotations of the compressor so that the set liquid temperature is set, the cooling liquid stored in the cooling liquid tank can be heated by being arranged in the cooling liquid tank The heater is turned on if at least the liquid temperature falls below a preset underload temperature, and the heater is turned off if the liquid temperature rises above a preset non-underload temperature. Cooling apparatus characterized by comprising and a control unit having a control function of.   The control to turn off the heater is on condition that both the liquid temperature has become a non-underload temperature or more and the compressor rotation speed is not less than a preset monitoring rotation speed. The cooling device according to claim 1, wherein the cooling device is performed.   3. The cooling device according to claim 2, wherein the monitored rotational speed is set to a rotational speed that is smaller by a predetermined rotational speed than a maximum operable rotational speed of the compressor.   The cooling device according to claim 1, wherein the underload temperature is set to a temperature lower than the set liquid temperature by a predetermined temperature.   The cooling device according to claim 1, wherein the non-underload temperature is set to a temperature that is higher than the set liquid temperature by a predetermined temperature.

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