Control method of vacuum cooling device

Abstract

To provide a vacuum cooling device capable of appropriately driving a plurality of vacuum pumps when decompression in a cooling tank is progressed.SOLUTION: According to the present invention, a vacuum cooling device 1 for cooling a cooling object F stored in a processing tank 2 includes an ejector 3, a heat exchanger 4, a plurality of vacuum pumps 5A-5C, and control means 10. The ejector 3 is connected to the processing tank 2, and the plurality of vacuum pumps 5A-5C are connected to its exhaust side through the heat exchanger 4. The heat exchanger 4 is configured so as to condense vapor discharged from the processing tank 2. The control means 10 is configured so as to control actuation of the ejector 3 and driving of the vacuum pumps 5A-5C. The control means 10 is configured so as to sequentially execute a first cooling step S1 for driving the plurality of vacuum pumps 5A-5C for decompressing the inside of the processing tank, and a second cooling step S2 for activating the ejector 3 and stopping driving at least one vacuum pump of the plurality of vacuum pumps 5A-5C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vacuum cooling device provided with a plurality of vacuum pumps.

Background Art

[0002] Conventionally, there has been a vacuum cooling device for vacuum-cooling an object to be cooled such as heat-cooked food in a cooling tank. For example, the vacuum cooling device disclosed in Patent Document 1 includes a steam ejector in addition to a heat exchanger for steam condensation and a water-sealed vacuum pump, and can vacuum-suck the inside of the cooling tank even at a very low pressure at a low temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a vacuum cooling device provided with a vacuum pump and an ejector as disclosed in Patent Document 1, in order to increase the exhaust speed before the operation of the steam ejector and shorten the decompression time, it is conceivable to perform exhaust by a plurality of vacuum pumps. However, as the decompression in the cooling tank progresses, the exhaust by a plurality of vacuum pumps becomes unnecessary, leading to an increase in running costs. Further, if there is a difference in capacity between a plurality of vacuum pumps, the pressure balance may be lost during high vacuum, and there is also a risk that the vacuum pump with excellent capacity may suck in outside air from the vacuum pump with inferior capacity.

[0005] The present invention has been made in view of such circumstances, and provides a vacuum cooling device capable of appropriately driving a plurality of vacuum pumps when the decompression in the cooling tank progresses.

Means for Solving the Problems

[0006] According to the present invention, there is provided a vacuum cooling device for cooling an object to be cooled accommodated in a treatment tank, the device comprising an ejector, a heat exchanger, a plurality of vacuum pumps, and control means. The ejector is connected to the treatment tank, and the vacuum pump is connected to the exhaust side of the ejector via the heat exchanger. The heat exchanger is configured to be able to condense the vapor exhausted from the treatment tank. The control means is configured to be able to control the operation of the ejector and the driving of the vacuum pump. The control means is configured to sequentially execute a first cooling step of driving the plurality of vacuum pumps to decompress the inside of the treatment tank, and a second cooling step of operating the ejector and stopping the driving of at least one of the plurality of vacuum pumps.

[0007] According to the present invention, by executing the second cooling step after the decompression in the cooling tank has advanced in the first cooling step, it is possible to avoid driving unnecessary vacuum pumps, suppress running costs, and prevent the suction of outside air during high vacuum.

[0008] Preferably, the device comprises pressure detection means for detecting the internal pressure of the treatment tank and temperature detection means for detecting the temperature of the object to be cooled. The control means switches from the first cooling step to the second cooling step on the condition that the internal pressure of the treatment tank detected by the pressure detection means is equal to or lower than a predetermined pressure and the temperature of the object to be cooled detected by the temperature detection means is equal to or lower than a predetermined temperature.

[0009] Preferably, a check valve is provided in the intake line of each vacuum pump.

[0010] Preferably, the device comprises abnormality detection means for detecting an abnormality of the vacuum pump. Even if the abnormality detection means detects an abnormality of some of the vacuum pumps, the control means drives other vacuum pumps to continue the cooling operation.

[0011] Preferably, the control means switches the at least one vacuum pump to be stopped in the second cooling step at a predetermined timing.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described. Various characteristic matters shown in the following embodiments can be combined with each other. Also, an invention can be established independently for each characteristic.

[0014] 1. Configuration of the vacuum cooling device 1 First, the configuration of the vacuum cooling device 1 according to an embodiment of the present invention will be described. The vacuum cooling device 1 is for vacuum-cooling an object to be cooled F such as heat-treated food in a treatment tank 2. As shown in FIG. 1, the vacuum cooling device 1 of the present embodiment includes a treatment tank 2, an ejector 3, a heat exchanger 4, a plurality of vacuum pumps (in this embodiment, three vacuum pumps, the first to third vacuum pumps 5A to 5C), a water supply means 6, a pressure recovery means 7, a pressure detection means 8, a temperature detection means 9, and a control means 10. Further, the vacuum cooling device 1 of the present embodiment is provided with an exhaust passage 11 for exhausting the gas (air and vapor) in the treatment tank 2 (see the thick line in the figure), and the ejector 3, the heat exchanger 4, and the first to third vacuum pumps 5A to 5C are connected to the exhaust passage 11 in this order. Hereinafter, each configuration will be specifically described.

[0015] The treatment tank 2 is a hollow container that can withstand the decompression of the internal space and can be opened and closed by a door (not shown). The treatment tank 2 is typically formed in a substantially rectangular box shape, and the front opening can be opened and closed by a door. By opening the door, the object to be cooled F can be put in and taken out of the treatment tank 2, and by closing the door, the opening of the treatment tank 2 can be hermetically closed. The door may be provided on both the front and back of the treatment tank 2. In the illustrated example, the object to be cooled F is contained in a food container such as a hotel pan or a rice cooker and is housed in the treatment tank 2.

[0016] The ejector 3 includes a suction port 3a, an exhaust port 3b, and a fluid inlet 3c. The ejector 3 creates a decompression zone by allowing fluid to pass through at high speed from a nozzle (not shown) provided at the fluid inlet 3c toward the exhaust port 3b, and sucks the fluid from the suction port 3a provided around the decompression zone. The ejector 3 of the present embodiment is provided in the exhaust passage 11, the suction port 3a is connected to the treatment tank 2, and the exhaust port 3b is connected to the heat exchanger 4, and is configured to suck and discharge the gas in the treatment tank 2 from the suction port 3a to the exhaust port 3b via the suction port 3a. Further, the ejector 3 of the present embodiment is a steam ejector, and is configured to suck the gas in the treatment tank 2 by ejecting the steam supplied from the ejector steam supply passage 30. Here, an ejector steam supply valve 31 is provided in the ejector steam supply passage 30, and the operation of the ejector 3 can be switched by opening and closing the ejector steam supply valve 31.

[0017] The heat exchanger 4 is an indirect heat exchanger that performs heat exchange without mixing the fluid (fluid from the ejector 3) in the exhaust passage 11 and the cooling water. The heat exchanger 4 can cool and condense the steam in the exhaust passage 11 with the cooling water. The cooling water is supplied from the water supply means 6 described later via the heat exchange water passage 40 and discharged via the heat exchange drain passage 41. The heat exchange drain passage 41 branches into a cold water return passage 42 to a cold water tank (chiller water supply source) not shown and a drain outlet passage 43 to the outside. A cold water return valve 44 is provided in the cold water return passage 42, and a drain outlet valve 45 is provided in the drain outlet passage 43. By the cold water return valve 44 and the drain outlet valve 45, it is possible to switch whether to return the water after passing through the heat exchanger 4 to the cold water tank, discharge it from the drain outlet passage 43, or block the water flow through the heat exchanger 4 (that is, close the cooling water outlet side of the heat exchanger 4).

[0018] The first to third vacuum pumps 5A to 5C are each a water-sealed vacuum pump and are driven while being supplied with water called sealing water. To supply the sealing water, water is supplied from a water supply means 6 described later to the water inlets 5x of the respective vacuum pumps 5A to 5C via a sealing water supply passage 50. Here, the sealing water supply passage 50 branches into three sealing water supply passages 50A to 50C corresponding to the respective vacuum pumps 5A to 5C. The respective sealing water supply passages 50A to 50C are provided with sealing water valves 51A to 51C and constant flow rate valves 52A to 52C. Here, the constant flow rate valves 52A to 52C are configured to allow water to flow through at a constant flow rate, as is well known.

[0019] Then, when the vacuum pumps 5A to 5C are operated while supplying water from the sealing water supply passage 50, each of the vacuum pumps 5A to 5C sucks gas from the intake port 5y and exhausts and discharges water to the exhaust port 5z.

[0020] In addition, check valves 13A to 13C corresponding thereto are provided in the respective intake lines 9A to 9C of the first to third vacuum pumps 5A to 5C. The check valves 13A to 13C prevent the backflow of gas from the vacuum pumps 5A to 5C to the intake line 9A to 9C side. The check valves 13A to 13C function as emergency shut-off valves to prevent the backflow of gas into the treatment tank 2 in the event of a malfunction or power failure of each of the vacuum pumps 5A to 5C.

[0021] In addition, sealing water temperature sensors 16A to 16C are provided in the first to third vacuum pumps 5A to 5C, respectively. The sealing water temperature sensors 16A to 16C are configured to be able to detect the temperature of the sealing water (sealing water temperature) existing inside each of the vacuum pumps 5A to 5C. Specifically, each of the sealing water temperature sensors 16A to 16C can be constituted by, for example, a thermocouple inserted inside each of the vacuum pumps 5A to 5C. In the present embodiment, each of the sealing water temperature sensors 16A to 16C functions as an abnormality detection means for detecting an abnormality of each of the vacuum pumps 5A to 5C. That is, when the temperature detected by the sealing water temperature sensors 16A to 16C becomes equal to or higher than a predetermined threshold value, the control means 10 described later determines that some abnormality has occurred in the corresponding vacuum pump 5A to 5C.

[0022] The water supply means 6 is configured to be able to supply normal temperature water or cold water to the heat exchanger 4 and the vacuum pump 5. Here, the cold water is water (chiller water) cooled to a predetermined temperature by a chiller (not shown), and the normal temperature water is water that is not cooled in such a manner. Specifically, the water supply means 6 includes a normal temperature water supply passage 60 connected to a water supply source and a cold water supply passage 61 connected to the chiller. Further, a normal temperature water supply valve 62 is provided in the normal temperature water supply passage 60, and a cold water supply valve 63 is provided in the cold water supply passage 61. In addition, a cold water temperature sensor 17 capable of detecting the temperature of the cold water is provided in the cold water supply passage 61.

[0023] The normal temperature water supply passage 60 and the cold water supply passage 61 merge at positions downstream of the normal temperature water supply valve 62 and the cold water supply valve 63 respectively, and become a common supply passage 64. This common supply passage 64 branches into a heat exchange water passage 40 to the heat exchanger 4 and a sealing water supply passage 50 to the first to third vacuum pumps 5A to 5C. Then, the water supply means 6 supplies cooling water to the heat exchanger 4 by opening the normal temperature water supply valve 62 or the cold water supply valve 63, and further supplies water to each of the vacuum pumps 5A to 5C by opening the sealing water valves 51A to 51C.

[0024] The pressure recovery means 7 is a means for introducing outside air into the depressurized treatment tank 2 to recover the pressure inside the treatment tank 2. In the present embodiment, the pressure recovery means 7 includes an air supply passage 70 connected to the treatment tank 2, and an air filter 71 and an air supply valve 72 are provided in the air supply passage 70 in order from the upstream side. When the air supply valve 72 is opened in a state where the inside of the treatment tank 2 is depressurized, outside air is introduced into the treatment tank 2 through the air filter 71, and the pressure inside the treatment tank 2 can be recovered. The air supply valve 72 is preferably an electric valve whose opening degree can be adjusted, and the pressure recovery speed can be adjusted. If the air supply valve 72 is such an electric valve, it becomes possible to perform slow cooling control in which the pressure inside the treatment tank 2 is adjusted while depressurizing in the first cooling step S1 and the second cooling step S2 described later.

[0025] The pressure detection means 8 is provided in the treatment tank 2. The pressure detection means 8 of the present embodiment is a pressure sensor that detects the pressure inside the treatment tank 2.

[0026] The temperature detection means 9 is provided in the treatment tank 2. The temperature detection means 9 of the present embodiment is a product temperature sensor that detects the temperature (product temperature) of the object to be cooled F accommodated in the treatment tank 2.

[0027] The control means 10 controls each of the above-described components based on the detection signals of the respective sensors, the elapsed time, and the like. Specifically, the control means 10 controls the ejector 3 (ejector steam supply valve 31), the cold water return valve 44 and the drain outlet valve 45, the first to third vacuum pumps 5A to 5C, the water seal valves 51A to 51C, the normal temperature water supply valve 62 and the cold water supply valve 63, and the air supply valve 72. Further, the pressure detection means 8, the temperature detection means 9, the water seal temperature sensors 16A to 16C, and the like are connected to the control means 10. In the present embodiment, as will be described later, the control means 10 performs control for cooling the object to be cooled F according to a predetermined procedure (program).

[0028] Note that the control means 10 having the above-described configuration can be specifically configured by, for example, an information processing device including a CPU, a memory (for example, a flash memory), an input unit, and an output unit. Then, the processing by each of the above-described components of the control means 10 configured by the information processing device is performed by the CPU reading and executing a program stored in the memory. As the information processing device, for example, a personal computer, a PLC (programmable logic controller), or a microcomputer is used. However, a part of the functions of the control means 10 may be configured to be executed on the cloud connected by an arbitrary communication means.

[0029] 2. Operation of the vacuum cooling device 1 Next, the operation of the vacuum cooling device 1 of the present embodiment will be described. The vacuum cooling device 1 of the present embodiment is configured to execute a first cooling step S1 and a second cooling step S2 under the control of the control means 10. Here, before the start of operation of the vacuum cooling device 1 (before the start of the first cooling step S1), each valve except the air supply valve 72 of the pressure recovery means 7 is in a closed state. To start the operation of the vacuum cooling device 1, first, the object to be cooled F is accommodated in the treatment tank 2, and after the door of the treatment tank 2 is hermetically closed, each step is executed. Hereinafter, with reference to the flowchart of FIG. 2, the operation of each step will be described in detail.

[0030] <First cooling step S1> The first cooling step S1 is a step of driving all of the first to third vacuum pumps 5A to 5C to decompress the inside of the treatment tank 2 and cooling the object to be cooled F. Specifically, the first cooling step S1 includes a normal temperature water cooling step using normal temperature water as the sealing water and a cold water cooling step using cold water as the sealing water. In the first cooling step S1, the control means 10 first executes the normal temperature water cooling step after the start of operation of the vacuum cooling device 1, and after the cooling progresses, executes the cold water cooling step. In the first cooling step S1, the control means 10 closes the ejector steam supply valve 31 so as not to operate the ejector 3. That is, the first cooling step S1 is a step of decompressing the inside of the treatment tank 2 only by the first to third vacuum pumps 5A to 5C without operating the ejector 3.

[0031] When an operation start is instructed, such as when the start button (not shown) of the vacuum cooling device 1 is pressed, the control means 10 first closes the air supply valve 72 in the normal temperature water cooling step. Then, the control means 10 starts the first to third vacuum pumps 5A to 5C and opens the normal temperature water supply valve 62 of the water supply means 6 and each sealing water valve 51A to 51C. As a result, normal temperature water is supplied to the first to third vacuum pumps 5A to 5C as sealing water, and decompression of the inside of the treatment tank 2 by the three vacuum pumps 5A to 5C is started. Thereby, the air containing the vapor generated from the high-temperature object to be cooled F is discharged through the exhaust passage 11.

[0032] At the same time, the control means 10 also opens the drain outlet valve 45 of the drain outlet passage 43. As a result, normal temperature water is also supplied from the water supply means 6 to the heat exchanger 4, heat exchange is performed between the steam from the treatment tank 2 and the normal temperature water, the steam from the treatment tank 2 is condensed, and water is sent to the first to third vacuum pumps 5A to 5C. On the other hand, the normal temperature water that has absorbed heat in the heat exchanger 4 is discharged to the outside through the drain outlet passage 43.

[0033] Due to the cooling in the normal temperature water cooling process, the pressure reduction in the treatment tank 2 progresses. When the pressure in the tank detected by the pressure detection means 8 becomes equal to or lower than a predetermined cold water supply start pressure (for example, 20 kPa), the control means 10, on this condition, shifts from the normal temperature water cooling process to the cold water cooling process.

[0034] To shift to the cold water cooling process, specifically, the control means 10 closes the normal temperature water supply valve 62 of the water supply means 6 and opens the cold water supply valve 63 to supply cold water as sealing water to the first to third vacuum pumps 5A to 5C. Further, the control means 10 closes the drain outlet valve 45 and opens the cold water return valve 44 to supply cold water to the heat exchanger 4 as well, and returns the cold water that has absorbed heat in the heat exchanger 4 to a cold water tank (not shown). The water returned to the cold water tank is cooled by a chiller (not shown) and is supplied again to the cold water supply passage 61.

[0035] In the cold water cooling process, by using cold water as sealing water, the saturation pressure in the first to third vacuum pumps 5A to 5C can be reduced, so the capacity of the first to third vacuum pumps 5A to 5C can be improved, and the pressure in the depressurized treatment tank 2 can be further reduced. Also, by supplying cold water to the heat exchanger 4 as well, the gas passing through the exhaust passage 11 can be condensed.

[0036] When the sealing water valves 51A to 51C are motorized valves whose opening degrees can be adjusted, by adjusting the opening degrees of the sealing water valves 51A to 51C, the exhaust speed of the vacuum pump 5 can be controlled to control the pressure reduction speed in the treatment tank 2, and while preventing cavitation in the vacuum pump 5, it is possible to suppress the amount of cold water used.

[0037] In addition, in the vacuum cooling apparatus 1 of the present embodiment, the control means 10 monitors the sealing water temperatures of the respective vacuum pumps 5A to 5C detected by the sealing water temperature sensors 16A to 16C as abnormality detection means. When an abnormality of any one of the vacuum pumps 5A to 5C is detected, the vacuum pump in which the abnormality is detected (for example, the first vacuum pump 5A) is stopped, and the vacuum pumps other than the said pump (for example, the second and third vacuum pumps 5B and 5C) are driven to continue the cooling operation.

[0038] In addition, in the cold water cooling step, the control means 10 acquires the pressure inside the tank detected by the pressure detection means 8 and the product temperature of the object to be cooled F detected by the temperature detection means 9. Then, the control means 10 controls to switch from the first cooling step S1 to the second cooling step S2 (see branch B1) on the condition that the pressure inside the tank becomes equal to or lower than a predetermined pressure and the product temperature becomes equal to or lower than a predetermined temperature. Here, the predetermined pressure is, for example, 45 hPa. The predetermined temperature is, for example, 30°C. However, these predetermined pressure and predetermined temperature can be appropriately changed according to the size of the treatment tank 2, the type of the object to be cooled F, and the exhaust capacity of the first to third vacuum pumps 5A to 5C. The predetermined pressure and the predetermined temperature are preset before the operation of the vacuum cooling apparatus 1, but it is preferable to store them in the memory provided in the control means 10 and to be able to appropriately change them by receiving an input from the user.

[0039] <Second Cooling Step> To shift to the second cooling step S2, the control means 10 specifically opens the ejector steam supply valve 31 to operate the ejector 3 and stops the driving of the first vacuum pump 5A and the second vacuum pump 5B. That is, the second cooling step S2 is a step of reducing the pressure in the treatment tank 2 by the ejector 3 and the third vacuum pump 5C. Further, the control means 10 closes the corresponding sealing water valves 51A and 51B in accordance with the stop of the driving of the first vacuum pump 5A and the second vacuum pump 5B. Further, the control means 10 keeps the cold water supply valve 63 and the cold water return valve 44 of the water supply means 6 open to continue the supply of cold water to the heat exchanger 4 and the third vacuum pump 5C. Note that a transition step of driving all the vacuum pumps 5A to 5C while operating the ejector 3 may be provided between the first cooling step S1 and the second cooling step S2. That is, in this case, the control means 10 stops the driving of the first vacuum pump 5A and the second vacuum pump 5B after a predetermined time of operation of the ejector 3.

[0040] In the second cooling step S2, by starting the ejector 3, even when the pressure in the tank becomes so low that it cannot be reduced by the first to third vacuum pumps 5A to 5C, it is possible to further reduce the pressure in the treatment tank 2. On the other hand, after the pressure in the tank becomes low, since the exhaust capacity of the three vacuum pumps of the first to third vacuum pumps 5A to 5C is not required, the driving of the first vacuum pump 5A and the second vacuum pump 5B is stopped, and only the third vacuum pump 5C is driven.

[0041] Note that in a configuration including a plurality of vacuum pumps (the first to third vacuum pumps 5A to 5C) as in the present embodiment, when only a part of the vacuum pumps (the third vacuum pump 5C) is driven, there is a possibility of backflow from the side of the vacuum pumps whose driving has been stopped (the first and second vacuum pumps 5A and 5B) to the vacuum pump in operation (the third vacuum pump 5C). However, in the vacuum cooling device 1 of the present embodiment, since check valves 13A to 13C are provided in the intake lines 9A to 9C of the first to third vacuum pumps 5A to 5C, it is possible to prevent such backflow.

[0042] Then, when the pressure in the treatment tank 2 in the second cooling step S2 is reduced and the pressure in the treatment tank 2 becomes equal to or lower than the target pressure (e.g., 1.2 kPa) (see branch B2 in Fig. 2), the second cooling step S2 is terminated, and the cooling of the object to be cooled F by the vacuum cooling device 1 is stopped. Specifically, to stop the cooling, the control means 10 closes the valves of the ejector steam supply valve 31, the cold water return valve 44, the drain outlet valve 45, the sealing water valve 51A, the normal temperature water supply valve 62, and the cold water supply valve 63, stops the ejector 3 and the third vacuum pump 5C, and stops the water flow through the heat exchanger 4. Thereafter, the air supply valve 72 is opened to return the pressure in the treatment tank 2 to atmospheric pressure.

[0043] In the above description, an example in which the first and second vacuum pumps 5A and 5B are stopped and only the third vacuum pump 5C is driven in the second cooling step S2 has been described. However, it is preferable to switch the vacuum pumps (5A to 5C) to be stopped in the second cooling step S2 at regular intervals. Specifically, the control means 10 rotates the vacuum pumps (5A, 5B, 5C) to be stopped in the second cooling step S2 at a predetermined timing (e.g., every predetermined number of times or at regular intervals).

[0044] For example, in the second cooling step S2, the control means 10 stops the operation of the first vacuum pump 5A and the second vacuum pump 5B during the first cooling operation, stops the operation of the second vacuum pump 5B and the third vacuum pump 5C during the second cooling operation, and stops the operation of the third vacuum pump 5C and the first vacuum pump 5A during the third cooling operation. By such an operation, the difference in the total operation time among the first to third vacuum pumps 5A to 5C can be suppressed, and the risk of failure can be reduced. In order to perform such control, it is preferable to store the vacuum pumps (5A, 5B, 5C) stopped during the cooling operation in the memory provided in the control means 10.

[0045] In addition, in the second cooling step S2 as well, the control means 10 monitors the sealed water temperature detected by the sealed water temperature sensor (for example, the sealed water temperature sensor 16C) corresponding to the vacuum pump in operation (for example, the third vacuum pump 5C). When the control means 10 detects an abnormality in the vacuum pump in operation (the third vacuum pump 5C), it stops the detected vacuum pump (the third vacuum pump 5C) and drives the other vacuum pumps (for example, the first vacuum pump 5A) to continue the cooling operation.

[0046] 3. Operational Effects As described above, in the vacuum cooling device 1 of the present embodiment, the control means 10 first executes the first cooling step S1 of driving the three vacuum pumps 5A to 5C to decompress the inside of the treatment tank 2. Then, on the condition that the pressure inside the tank becomes equal to or lower than the predetermined pressure and the product temperature of the object to be cooled F becomes equal to or lower than the predetermined temperature, the ejector 3 is operated and the second cooling step S2 of stopping two vacuum pumps (for example, the first and second vacuum pumps 5A and 5B) is executed. With such a configuration, it is possible to appropriately perform decompression even when the decompression inside the treatment tank 2 progresses. Specifically, when the decompression progresses, the ejector 3 can be operated in the second cooling step S2 to further promote the decompression. In addition, by stopping the two vacuum pumps (5B, 5C), it is possible to avoid driving unnecessary vacuum pumps, reduce the electricity consumption and the sealed water consumption, and suppress the running cost.

[0047] Also, in the vacuum cooling device 1 provided with a plurality of vacuum pumps 5A to 5C, when all the first to third vacuum pumps 5A to 5C are continuously driven at high vacuum where the decompression progresses, there is a possibility that the vacuum pump with excellent performance may suck in outside air from the vacuum pump with poor performance due to a delay in the operation of the check valves 13A to 13C or the like. However, in the vacuum cooling device 1 of the present embodiment, it is also possible to prevent such suction of outside air by stopping two vacuum pumps (for example, 5B, 5C) in the second cooling step S2 at high vacuum.

[0048] In addition, in the vacuum cooling device 1 of the present embodiment, even when any of the water seal temperature sensors 16A to 16C as the abnormality detection means detects an abnormality in any of the vacuum pumps (5A to 5C), the control means 10 continues the cooling operation by driving the other vacuum pumps. Since it has such a configuration, even when some of the vacuum pumps (5A to 5C) cannot be driven, although the cooling time becomes longer, the cooling operation by the vacuum cooling device 1 can be performed without immediately making the cooling operation impossible. Therefore, the vacuum cooling device 1 of the present embodiment can perform the cooling operation until the failed vacuum pump (5A to 5C) is repaired even when some of the vacuum pumps (5A to 5C) fail.

[0049] 4. Modification Note that the present invention can also be implemented in the following aspects.

[0050] In the above embodiment, the control means 10 shifted from the first cooling step S1 to the second cooling step S2 on the condition that the pressure inside the tank became equal to or lower than the predetermined pressure and the product temperature became equal to or lower than the predetermined temperature. However, instead of this condition, it may be shifted from the first cooling step S1 to the second cooling step S2 based on other conditions such as the time from the start of operation and the water seal temperature of each vacuum pump 5A to 5C detected by the water seal temperature sensors 16A to 16C. The present invention is established if the control means 10 controls to shift from the first cooling step S1 in which cooling is performed by a plurality of vacuum pumps to the second cooling step S2 in which cooling is performed by an ejector and some of the vacuum pumps under some conditions.

[0051] In the above embodiment, the water seal temperature sensors 16A to 16C that detect the water seal temperature are used as the abnormality detection means for detecting abnormalities in each of the vacuum pumps 5A to 5C. However, as the abnormality detection means, instead of the water seal temperature sensors 16A to 16C, thermal relays may be provided for each of the vacuum pumps 5A to 5C and used as the abnormality detection means. Further, both the water seal temperature sensor and the thermal relay may be used as the abnormality detection means.

[0052] In the above-described embodiment, the first cooling step S1 included a normal-temperature water cooling step of supplying normal-temperature water to the heat exchanger 4 and the vacuum pump 5, and a cold-water cooling step of supplying cold water to the heat exchanger 4 and the vacuum pump 5. However, in the first cooling step S1, it is also possible to adopt a configuration in which cold water is constantly supplied.

[0053] In the above-described embodiment, the ejector 3 for exhausting the gas in the treatment tank 2 was a steam ejector that sucked the gas in the treatment tank 2 by ejecting the steam supplied from the ejector steam supply passage 30. However, as the ejector, it is also possible to use a water ejector that ejects the water supplied from the ejector water supply passage.

[0054] In the above-described embodiment, each of the vacuum pumps 5A to 5C was a water-sealed vacuum pump. However, the vacuum pumps 5A to 5C may be of other types such as a dry type or an oil rotary type. Further, the vacuum pumps 5A to 5C may be subjected to on-off control or their outputs may be adjustable. For example, the vacuum pumps 5A to 5C can change the driving frequency of the motor and thus the rotational speed by using an inverter.

[0055] In the above-described embodiment, check valves 13A to 13C were provided in the intake lines 9A to 9C of each of the vacuum pumps 5A to 5C. However, instead of the check valves 13A to 13C, valves such as on-off valves or motor-operated valves may be used.

[0056] In the above-described embodiment, in the second cooling step S2, the driving of two vacuum pumps (for example, the first and second vacuum pumps 5A and 5B) was simultaneously stopped. However, in the second cooling step S2, only the driving of one vacuum pump (for example, the first vacuum pump 5A) may be stopped and the pressure may be reduced by two vacuum pumps (for example, the second and third vacuum pumps 5B and 5C). Also, in the second cooling step S2, first, the driving of one vacuum pump (for example, the first vacuum pump 5A) may be stopped, and then, the driving of another vacuum pump (for example, the second vacuum pump 5B) may be stopped.

[0057] In the above-described embodiment, the vacuum cooling device 1 was configured to include three vacuum pumps 5A to 5C. However, the number of vacuum pumps provided in the vacuum cooling device 1 may be two, or may be four or more.

[0058] Furthermore, in the above-described embodiment, the vacuum cooling device 1 was described as a cooling dedicated machine. However, as long as it has at least a vacuum cooling function, it can be appropriately changed. For example, by providing a heating means using steam, it may be configured as a steaming and cooling device or a saturated steam cooking device. Alternatively, by providing a cold air cooling means using a refrigerator or a fan, it may be configured as a cold air vacuum composite cooling device.

Explanation of Reference Numerals

[0059] 1: Vacuum cooling device 2: Processing tank 3: Ejector 3a: Suction port 3b: Exhaust port 3c: Fluid inlet 4: Heat exchanger 5A: First vacuum pump 5B: Second vacuum pump 5C: Third vacuum pump 5x: Water supply port 5y: Air intake port 5z: Exhaust port 6: Water supply means 7: Pressure recovery means 8: Pressure detection means 9: Temperature detection means 9A~9C: Air intake line 10: Control means 11: Exhaust passage 13A~13C: Check valve 16A~16C: Sealing water temperature sensor 17: Chilled water temperature sensor 30: Ejector steam supply passage 31: Ejector steam supply valve 40: Heat exchange water passage 41: Heat exchange drain passage 42: Chilled water return passage 43: Drain outlet passage 44: Cold water return valve 45: Drain outlet valve 50, 50A~50C: Sealing water supply path 51A~51C: Sealing water valve 52A~52C: Constant flow valve 60: Normal temperature water supply path 61: Cold water supply path 62: Normal temperature water supply valve 63: Cold water supply valve 64: Common supply path 70: Air supply path 71: Air filter 72: Air supply valve B1, B2: Branch F: Object to be cooled S1: First cooling process S2: Second cooling process

Claims

1. A method for controlling a vacuum cooling device that cools an object to be cooled accommodated in a processing tank, wherein the vacuum cooling device includes an ejector, a heat exchanger, a plurality of vacuum pumps, and a control means, the ejector is connected to the processing tank, and the vacuum pump is connected to the exhaust side thereof via the heat exchanger, the heat exchanger is configured to be able to condense the vapor exhausted from the processing tank, the control means is configured to be able to control the operation of the ejector and the driving of the vacuum pump, and the control means sequentially executes a first cooling step of driving the plurality of vacuum pumps to reduce the pressure in the processing tank, and a second cooling step of operating the ejector and stopping the driving of at least one of the plurality of vacuum pumps. A method for controlling a vacuum cooling device.

2. A method for controlling a vacuum cooling device according to Claim 1, wherein the vacuum cooling device includes a pressure detection means for detecting the pressure inside the processing tank and a temperature detection means for detecting the temperature of the object to be cooled, and the control means switches from the first cooling step to the second cooling step on the condition that the pressure inside the tank detected by the pressure detection means is equal to or lower than a predetermined pressure and the temperature of the object to be cooled detected by the temperature detection means is equal to or lower than a predetermined temperature. A method for controlling a vacuum cooling device.

3. A method for controlling a vacuum cooling device according to Claim 1 or Claim 2, wherein a check valve is provided in the intake line of each vacuum pump in the vacuum cooling device. A method for controlling a vacuum cooling device.

4. A method for controlling a vacuum cooling device according to any one of Claims 1 to 3, wherein the vacuum cooling device includes an abnormality detection means for detecting an abnormality of the vacuum pump, and the control means continues the cooling operation by driving other vacuum pumps even if the abnormality detection means detects an abnormality of some of the vacuum pumps. A method for controlling a vacuum cooling device.

5. A method for controlling a vacuum cooling device according to any one of Claims 1 to 4, wherein the control means switches the at least one vacuum pump to be stopped in the second cooling step at a predetermined timing. A method for controlling a vacuum cooling device.

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