JP4532833B2 - Vacuum cooling method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum cooling method for cooling a food or vegetable by evacuating a treatment tank.
[0002]
[Prior art]
In recent years, it has been required to rapidly reduce the temperature of cooked foods and the like from the viewpoint of safety and hygiene of foods and the like. One method for cooling these foods (hereinafter referred to as “objects to be cooled”) is a vacuum cooling method.
[0003]
In such a vacuum cooling method, moisture is vaporized from the object to be cooled itself. Therefore, when the pressure is rapidly reduced, boiling occurs in the object to be cooled, and the like, Some may scatter or lose shape. On the other hand, if the vacuum cooling is performed slowly, boiling or the like does not occur, but the cooling time becomes longer and the operation efficiency of the vacuum cooler becomes worse. That is, the vacuum cooling method has conflicting problems of preventing boiling and shortening the cooling time.
[0004]
In order to solve these problems, the applicant stores the decompression characteristic curve examined in advance for each object to be cooled in a controller by programming, detects the pressure in the processing tank, and follows the decompression characteristic curve. It is proposed to perform the decompression control (Japanese Patent Application No. 2002-42412).
[0005]
This method is effective as a technique for preventing the object to be cooled from boiling. However, it is not effective for the object to be cooled other than the object to be cooled corresponding to the decompression characteristic curve stored in the controller, and there is a problem that boiling cannot be prevented for many of the objects to be cooled. is there.
[0006]
Further, as a technique for preventing boiling of the object to be cooled, the pressure in the treatment tank is detected, and the temperature of the object to be cooled (hereinafter referred to as “product temperature”) is detected, and the inside of the treatment layer is detected. A technique for controlling the saturated pressure of the object to be cooled has been proposed (see, for example, Patent Document 1).
[0007]
[Patent Document 1]
JP-A-6-27307 (page 3, FIG. 1)
[0008]
According to the prior art described in Patent Document 1, since the saturation pressure is controlled at a preset temperature value of the object to be cooled, an appropriate cooling rate cannot be achieved, and the cooling time is long. There is a problem of becoming. As a result, the above-described prior art has not been sufficient in solving the boiling prevention and the shortening of the cooling time, which are the problems of the conflicting vacuum cooling method.
[0009]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to prevent bumping and scattering associated with it, or to prevent deformation of the mold, and to perform appropriate cooling suitable for the object to be cooled.
[0010]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems, and includes a treatment tank that accommodates an object to be cooled, a decompression unit that decompresses the inside of the treatment tank, and a temperature at which the temperature of the object to be cooled is detected. A vacuum cooling method of a vacuum cooling device comprising a sensor and an electric valve that adjusts a holding pressure in a plurality of stages by introducing air into the processing tank, and the pressure in the processing tank is finally reduced by pressure reduction Reach first A first pressure holding step for reducing the pressure in the processing tank by operating the pressure reducing means by setting the opening of the motor-operated valve to a predetermined value so as to obtain a holding pressure, and detecting by the temperature sensor by the first pressure holding step The product temperature determination step for determining whether the temperature of the object to be cooled has reached a set temperature, and the time change of the temperature of the object to be cooled detected by the temperature sensor is below a reference value. The By determining, the temperature of the object to be cooled is The pressure in the treatment tank finally reaches due to the reduced pressure Holding pressure Of the corresponding object to be cooled The product temperature time change determining step for determining that the temperature has almost approached the saturation temperature, the arrival of the set temperature is determined by the product temperature determining step, and the reference temperature or less is determined by the product temperature time change determining step. Then, the pressure of the treatment tank Guarantee Including a holding pressure reduction process for reducing the holding pressure by a predetermined value, Taho A second pressure holding step of reducing the pressure in the processing tank so as to be a holding pressure, and repeatedly performing the product temperature change determination step and the second pressure holding step, the second pressure holding step Each adjustment of the predetermined value in the holding pressure reduction step when iterating is performed by adjusting the opening degree of the motor-operated valve in a plurality of stages with the exhaust amount of the decompression means being constant, and the product temperature of the object to be cooled is The lower pressure is performed by reducing the amount of closing the motor-operated valve, and the first pressure holding step, the product temperature change determination step, and the second pressure holding step are performed without using a pressure sensor. Holding process The first The holding pressure, the reference value of the product temperature determination step, and the predetermined value of the holding pressure reduction step are set so as to prevent bumping of the object to be cooled.
[0011]
The invention described in claim 2 is characterized in that, in claim 1, the reference value is adjustable.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention can be implemented in a vacuum cooling method using a vacuum cooler that cools food by evacuating the inside of the treatment tank when cooling food (hereinafter referred to as “object to be cooled”). .
[0013]
(Embodiment 1)
An embodiment of the present invention is a vacuum cooling method in which a processing tank is depressurized to cool an object to be cooled, and the pressure in the processing tank is first The pressure inside the treatment tank is reduced to a holding pressure, and it is determined that the time change of the temperature of the object to be cooled (hereinafter referred to as “product temperature”) has become a reference value or less. The pressure in the treatment tank finally reaches due to the reduced pressure Holding pressure Of the corresponding object to be cooled It was determined that the saturation temperature was almost approached, and the pressure in the treatment tank was Guarantee Reduce the holding pressure by a predetermined value Taho Decrease the inside of the treatment tank so that the holding pressure becomes Guarantee It is a vacuum cooling method characterized by repeatedly performing pressure reduction by reducing holding pressure.
[0014]
In this embodiment, when depressurization in the processing tank is started, the pressure in the processing tank first decreases with a large gradient while introducing (leaking) outside air, and the gradient decreases with time. And finally said first The holding pressure is reached. Thus, the pressure in the treatment tank is first Hold at the holding pressure (first pressure holding step). this first Holding pressure of By holding, the product temperature is first In the treatment tank equal to the holding pressure Of the object to be cooled corresponding to the pressure Lower to saturation temperature. When the temporal change in the product temperature decreases, it is determined that the product temperature has approached the saturation temperature. In this state, it is determined whether the temporal change in the product temperature is equal to or less than the reference value (change in the product temperature over time). Determination step), when the reference value or less is determined, The pressure in the treatment tank finally reaches due to the reduced pressure The holding pressure is reduced by a small predetermined value (holding pressure reduction process), and the pressure in the processing tank is reduced. Taho The pressure is reduced so that the holding pressure is reached (second pressure holding step). The second pressure holding step includes the holding pressure reducing step.
[0015]
In the above, product temperature But" The phrase “approaching the saturation temperature” includes a case where the product temperature is slightly higher than the saturation temperature, a case where the product temperature is equal to the saturation temperature, and a case where the product temperature is slightly lower than the saturation temperature.
[0016]
And after said 1st pressure holding process, the difference of the temperature of the said to-be-cooled object and the saturation temperature in the said processing tank is constant temperature by repeating the said product temperature time change determination process and said 2nd pressure holding process. It cools so that it may become below the range. The saturation temperature of the treatment tank is the saturation temperature of the object to be cooled corresponding to the pressure of the treatment tank.
[0017]
The constant pressure holding in the processing tank by the first pressure holding step and the second pressure holding step is preferably performed as follows. An electric valve that adjusts the amount of leakage in multiple stages is connected to the processing tank, and a pressure reducing means is connected to the processing tank, and the exhaust amount of the pressure reducing means is controlled to be constant with the opening of the motor operated valve as a predetermined value. Thus, the pressure in the treatment tank is The pressure in the treatment tank finally reaches due to the reduced pressure It is held constant at the holding pressure.
[0018]
As the pressure reducing means, a vacuum pump, a combination of the vacuum pump, a steam ejector, and a heat exchanger, or a combination of the vacuum pump and the heat exchanger can be used. The steam ejector may be replaced with a water ejector.
[0019]
In the product temperature / time change determination step, the temperature change due to the cooling operation is regarded as temperature change / time (ΔT / Δt) change of the product temperature, and the temperature change / time (hereinafter referred to as “product temperature time”). It is determined whether or not (change) is equal to the reference value (ΔT1 / Δt1). The determination that the reference value has been reached is performed in the treatment tank. Of the object to be cooled corresponding to the pressure The difference between the saturation temperature and the product temperature decreases, and the product temperature Said Determining that the saturation temperature has been approached.
[0020]
The reference value (ΔT1 / Δt1) is preferably adjustable, and more preferably, only the temperature difference (ΔT1) is variable with the time (Δt1) as a fixed time. Depending on the implementation, both ΔT 1 and Δt 1 can be adjustable.
[0021]
The reference value can be depressurized slowly by reducing the value, and conversely, it can be depressurized quickly by increasing the value of the object to be cooled with a small amount of liquid and a large amount of solid. The reference value can be set according to the type and amount of the object to be cooled, and even if the same object and amount are to be cooled, it is determined that the reference value is more appropriate based on the result of the past vacuum cooling operation. Can be set to a value.
[0022]
The setting of the reference value is executed by a user or maintenance person of the vacuum cooler, and the setting result is stored in the controller of the vacuum cooler. The setting need not be performed for each vacuum cooling operation, but may be performed when the reference value needs to be changed.
[0023]
The holding pressure reducing step includes The pressure in the treatment tank finally reaches due to the reduced pressure This is a step of lowering the holding pressure by a small predetermined value, and is performed by adjusting the opening of the motor-operated valve. This holding pressure reduction step is a step necessary for the next effective reduction of the product temperature when the change in the product temperature is eliminated by the pressure holding step.
[0024]
According to this embodiment, after performing the first pressure holding step, the product temperature time change determining step and the second pressure holding step are repeatedly performed, so the difference between the product temperature and the saturation temperature is increased. Therefore, it is possible to perform vacuum cooling while suppressing the formation of the overheated region. In addition, since the reference value of the time change of the product temperature can be changed and set according to the type of the object to be cooled, the reference value is increased within a range that does not cause boiling due to the formation of the overheating region. The time required for vacuum cooling, that is, the vacuum cooling time can be shortened.
[0025]
The present invention is not limited to the above-described embodiment, and includes the following second to eighth embodiments.
[0026]
(Embodiment 2)
A vacuum cooling method for cooling an object to be cooled by depressurizing the inside of the treatment tank, wherein the pressure in the treatment tank is Ichiho The first pressure holding step for holding the holding pressure, the product temperature time change determining step for determining whether the time change of the product temperature is equal to or less than the reference value, and the reference temperature or less is determined by the product temperature time change determining step. Once judged The pressure in the treatment tank finally reaches due to the reduced pressure A holding pressure reducing step of reducing the holding pressure by a small predetermined value, and the pressure in the processing tank is set by the holding pressure reducing step. Niho And a second pressure holding step for holding the holding pressure, and repeatedly performing the product temperature change determination step and the second pressure holding step.
[0027]
(Embodiment 3)
In the first embodiment or the second embodiment, the predetermined value in the holding pressure reduction step is adjusted according to a product temperature when a value equal to or lower than the reference value in the product temperature time change determination step is determined. A featured vacuum cooling device.
[0028]
In the third embodiment, the predetermined value in the holding pressure reduction step is adjusted according to the product temperature when it is determined that the reference value or less is determined in the product temperature time change determination step. Specifically, the adjustment of the predetermined value is an adjustment of the opening degree of the motor-operated valve. When the operating time of the motor-operated valve is lengthened, the amount of closing the motor-operated valve increases. Accordingly, when the product temperature is T11 ° C., the operation time is t11, the product temperature is less than T11, and when the product temperature is T12 (<T11) or more, the operation time is t12 (<t11), and the product temperature is less than T12, T13 (<T12). Thus, the control is performed so that the operation time is t13 (<t12).
[0029]
According to the third embodiment, the amount of the predetermined pressure in the holding pressure reduction step is adjusted according to the product temperature. Guarantee It is possible to effectively prevent the object to be cooled from boiling in the region where the holding pressure is low.
[0030]
(Embodiment 4)
In the second embodiment or the third embodiment, there is provided a product temperature determination step for determining whether or not the product temperature has reached the first set temperature, the arrival at the first set temperature is determined, and the product temperature time A vacuum cooling method for executing the holding pressure reduction step when it is determined that the reference value is reached in the change determination step.
[0031]
(Embodiment 5)
The vacuum cooling method according to the fourth embodiment, wherein the first set temperature can be adjusted.
[0032]
According to the fifth embodiment, when the first preset temperature is set to a high value, the pressure reduction rate can be slowed, which is suitable for preventing bumping of an object to be cooled whose viscosity increases remarkably due to a decrease in temperature, such as a liquid with high viscosity. It is. Further, when the first set temperature is set low, the vacuum cooling time can be shortened.
[0033]
(Embodiment 6)
In any of the first to fifth embodiments, in the holding pressure reducing step. The pressure in the treatment tank finally reaches due to the reduced pressure A vacuum cooling method further including a delaying step of delaying the holding pressure reduction execution time by an adjustable delay time (t2).
[0034]
The delaying process in the sixth embodiment is performed before the holding pressure reducing process. The delay time can be adjusted, and if the time is lengthened, the product temperature can be sufficiently lower than the saturation temperature in the treatment tank due to heat radiation or the like, and even when a sudden pressure drop is caused by the next holding pressure reduction process, bumping can occur. Can be prevented. Further, if the delay time is lengthened, the product temperature can be reduced to the target temperature without subsequent decompression.
[0035]
(Embodiment 7)
In any one of the first to sixth embodiments, when the product temperature reaches a second set temperature lower than the first temperature, the reduction adjustment in the holding pressure reduction process is maximized, and the inside of the processing tank is depressurized. A vacuum cooling method comprising a cooling step after the second pressure holding step.
[0036]
According to the seventh embodiment, when the product temperature reaches the second set temperature, the pressure can be rapidly reduced and the vacuum cooling time can be shortened. This embodiment is based on the knowledge by the inventors that if the product temperature is lowered to a certain temperature, the temperature difference between the top and bottom surfaces of the object to be cooled does not increase, and boiling does not occur even if sudden pressure reduction is performed. Based.
[0037]
(Embodiment 8)
The vacuum cooling method according to Embodiment 7, wherein the second set temperature can be adjusted.
[0038]
In the eighth embodiment, since the second set temperature varies depending on the characteristics of the object to be cooled, the temperature can be set according to the object to be cooled.
[0039]
【Example】
(First Example)
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view for explaining a vacuum cooling apparatus of an embodiment to which the vacuum cooling method of the present invention is applied, and FIG. 2 is a flowchart showing a control procedure by a controller of the embodiment. FIG. 3 shows the product temperature at the bottom of the part to be cooled by the vacuum cooling method of the embodiment when the object to be cooled is warm water and the inside of the treatment tank. Of the object to be cooled corresponding to the pressure It is a characteristic view which shows the time change of saturation temperature.
[0040]
(Configuration of Example)
In FIG. 1, a vacuum cooling device 1 includes a processing tank 3 for storing a food to be cooled (hereinafter referred to as “object to be cooled”) 2 and a door (not shown) for hermetically closing the processing tank 3. A pressure reducing means 4 for depressurizing the inside of the processing tank 3, a temperature sensor 5 as a product temperature detecting means for detecting the temperature of the object to be cooled 2 (hereinafter referred to as "product temperature"), and air. By introducing into the treatment tank 3 The pressure in the treatment tank 3 finally reaches due to the reduced pressure. A motor-operated valve 6 as holding pressure adjusting means for adjusting the holding pressure in a plurality of stages and a controller 7 for controlling the vacuum cooling operation are provided.
[0041]
The object to be cooled 2 is a food containing a lot of moisture, for example, soup, and is put in a large number of breads (containers) 8, 8,..., And a plurality of shelves 9, 9,. It is mounted on.
[0042]
The decompression unit 4 includes a vacuum pump 11, a steam ejector 12, a condenser (heat exchanger) 13 and a check valve 14 provided in a vacuum suction line 10 connected to the processing tank 3. The steam ejector 12 depressurizes the inside of the processing tank 3 on the upstream side of the vacuum pump 11. Thereby, the decompression means 4 performs two-stage decompression. The capacitor 13 has a function of cooling the gas sucked by the vacuum pump 11 on the downstream side of the ejector 12.
[0043]
The temperature sensor 5 detects the product temperature and outputs the temperature signal to the controller 7. And the front-end | tip part (code | symbol omission) of the said temperature sensor 5 inserts in one of the said to-be-cooled objects 2, and detects a product temperature.
[0044]
The motor-operated valve 6 is provided in an air pipe 14 connected to the processing tank 3. The motor-operated valve 6 has a function of adjusting the air introduction amount in a plurality of stages by adjusting the opening degree in a plurality of stages from the fully open to the fully closed state according to the output signal of the controller 7. . The holding pressure reduction is adjusted in a plurality of stages by the opening adjustment function of the motor-operated valve 6. An air filter 15 for cleaning the air introduced into the processing tank 3 is provided at the tip of the air pipe 14.
[0045]
The controller 7 is connected to the pressure-reducing means 4, the temperature sensor 5, and the motor-operated valve 6 via lines 16, 16,. The controller 7 realizes the vacuum cooling method of the present invention by controlling the operation of the pressure reducing means 4 and the operation of the motor-operated valve 6 according to the processing procedure shown in FIG. Control of the decompression means 4 by the controller 8 includes starting and stopping control of the vacuum pump 11 and opening / closing control of an electromagnetic valve (not shown) for controlling supply of steam as a working fluid of the steam ejector 12; Control of supply of working fluid (not shown) to the capacitor 13.
[0046]
(Operation of the embodiment)
The operation of the embodiment will be described according to the processing procedure shown in FIG. First, warm water as the object to be cooled 2 is stored in the processing tank 3 in a state where it is put in each pan 8, the door is closed, and preparation for vacuum cooling operation is performed. Then, in process step S1 (hereinafter, process step SN is simply referred to as SN), adjustable set values, that is, the first set temperature T0 ° C., temperature change ΔT 1 ° C., delay time t 2 min (minutes), product A second set temperature T2 ° C. lower than the first set temperature is set and input.
[0047]
Said 1st preset temperature T0 degreeC is the product temperature which determines the start of a temperature change determination process. The first set temperature T0 ° C. is a temperature at which the bubble diameter does not become so large even when boiling occurs and scattering does not occur. And it is necessary to set temperature high with respect to the to-be-cooled object 2 with large surface tensions, such as a highly viscous liquid.
[0048]
The temperature change ΔT1 ° C. is a reference value (ΔT1 / Δt1) of the time change (ΔT / Δt) of the product temperature. molecule The time Δt1min is fixed to 3 minutes. The delay time t2min is a time for delaying the holding pressure adjustment by the motor-operated valve 6. The second set temperature T2 ° C. is a product temperature for determining a time point when the motor valve 6 is fully closed and the holding pressure reduction adjustment is maximized. The input of each set value is performed as necessary.
[0049]
In the vacuum cooling operation shown in FIG. 3, the first set temperature T0 ° C. is set to 50 ° C., the temperature change ΔT 1 ° C. is set to 1.8 ° C., the delay time t 2 min (min) is set to 2 minutes, and the second set temperature is set. The temperature T2 ° C is set to 15 ° C.
[0050]
Next, when the process proceeds to S2 and the start switch (not shown) of the vacuum cooling operation is turned on, the motor-operated valve 6 is closed for about 14.5 seconds from the full opening (the valve opening is about ½), and the vacuum The pump 11 is operated, and the pressure in the processing tank 3 corresponds to the opening degree of the motor-operated valve 6. The pressure in the treatment tank 3 finally reaches due to the reduced pressure. The pressure is reduced to the holding pressure (first pressure holding step), and the vacuum cooling operation is started.
[0051]
In the first half of the first pressure holding step, only the vacuum pump 11 is operated, and the product temperature reaches a predetermined temperature from the start of the cooling operation, which is about 45 ° C. in this embodiment, or a set time from the start of the cooling operation. In the example, the operation of the ejector 12 is started after about 5 minutes. Thus, the first pressure holding step performs control to increase the pressure reduction speed step by step, and the product temperature and the processing tank 3 Saturation temperature (Saturation temperature of the object to be cooled corresponding to the pressure in the treatment tank 3) The temperature difference (about 4 ° C.) that does not form the overheating region is not exceeded.
[0052]
In the first pressure holding step, the inside of the processing tank 3 is depressurized by the vacuum suction action of the decompression means 4 and exhausted through the vacuum suction line 10. Due to this suction / exhaust action, the product temperature gradually decreases as water evaporates from the object to be cooled. At that time, vacuum is sucked while the outside air is sucked from the motor-operated valve 6, and the front according to the opening degree of the motor-operated valve 6. Guarantee A vacuum cooling operation is performed so as to maintain the holding pressure. The state of the decrease in the product temperature is shown in FIG. In this figure, the curve A shows the change over time of the saturation temperature of the object to be cooled, and the curve B shows the change over time of the product temperature at the bottom of the object to be cooled, that is, the bottom inside the bread 8. The point X of the curve A indicates the saturation temperature when the ejector 12 is activated.
[0053]
By this first pressure holding step, the saturation temperature (pressure) in the treatment tank 3 rapidly decreases at the beginning of decompression as shown by the curve A in FIG. Before corresponding to 6 opening Guarantee The holding pressure is maintained. The product temperature gradually approaches the saturation temperature of the treatment tank 3 as shown by a curve B in FIG. This represents a process in which the difference between the product temperature and the saturation temperature of the object to be cooled decreases.
[0054]
In such a first pressure holding step, it is determined whether the temperature detected by the temperature sensor 5 has reached 50 ° C. (first product) Warm Step S3). In S3, if NO is determined, the first pressure holding step is continued without changing the opening of the motor-operated valve 6. If YES is determined, the process proceeds to S4.
[0055]
In S4, it is determined whether or not the change in product temperature over time (ΔT / Δt) is equal to or less than the reference value (ΔT1 / Δt1), that is, whether the change in product temperature in 3 minutes is less than 1.8 ° C. ( Product temperature time change judgment process ). If NO is determined in S4, the process remains at S4, the first pressure holding step is continued, and if YES is determined, the process proceeds to S5. The determination of YES in S4 means that a change in the product temperature time decreases, and if the first pressure holding step is continued as it is, the vacuum cooling operation is prolonged.
[0056]
In S5, it is determined whether or not 2 minutes of the delay time (t2) has elapsed (first delay time determination step). If NO is determined in S5, the first cooling step is continued, and if YES is determined, the process proceeds to S6.
[0057]
In S6, by closing the motor-operated valve 6 for 0.4 seconds, the opening degree is slightly reduced, The pressure in the treatment tank 3 finally reaches due to the reduced pressure. A vacuum cooling operation (second pressure holding step) is performed by lowering the holding pressure a little (holding pressure reduction adjusting step) and reducing the pressure inside the processing tank 3 to a reduced holding pressure. The point in time when the holding pressure is adjusted by the motor-operated valve 6 is indicated by point P in FIG. It can be seen that the slope of the pressure drop in the treatment tank 3 is steep immediately after the point P. By adjusting the holding pressure, the product temperature and the Saturation temperature of the object to be cooled corresponding to the pressure in the treatment tank 3 And the difference between the temperature of the object to be cooled and the evaporation of water from the object to be cooled become active, thereby reducing the product temperature.
[0058]
After the holding pressure reduction step of S6, the process proceeds to S7, and after execution of the holding pressure adjustment, it is determined whether or not a predetermined delay time (t3: in this embodiment, a fixed value, 80 sec) has elapsed. (Second delay time determination step). If NO is determined in S7, the process stays in S7. If YES is determined, the process proceeds to S8 to determine whether the product temperature has reached the second set temperature of 15 ° C (second product temperature determination). Step).
[0059]
If NO is determined in S8, the process returns to S4, and the second pressure holding step is performed until it is determined that the first set temperature is reached. In this second pressure holding step, the gradient of the pressure drop in the processing tank 3 is steep immediately after holding pressure adjustment as shown after point P in FIG. Retained. And the product temperature Of the object to be cooled corresponding to the pressure in the treatment tank 3 When the difference from the saturation temperature decreases, the value of the change in product temperature over time (ΔT / Δt) also decreases, and this value is again Standard value Then, YES is determined in S4.
[0060]
Then, the first delay time determination step of S5, the holding pressure reduction step of S6, the second product temperature determination step of S8, and the product temperature time change determination step of S4 are the second product temperature determination step. The process is repeatedly performed until reaching the second set temperature is determined. The repetition of this process repeats the operation of reducing the holding pressure a little when the time change of the product temperature becomes small, and lowering the holding pressure a little when the time change of the product temperature becomes small again. In the example shown in FIG. 3, the holding pressure is reduced again at S6 at the point Q.
[0061]
The reason for providing the delay time (t3) is as follows. Even if the holding pressure is reduced in S6, the time change of the product temperature does not change immediately. Therefore, if the delay time (t3) is not provided, if the determination of S4 is immediately performed via S8 after the processing of S6, YES is determined, and the holding pressure adjustment of S6 is again performed before the effect of the holding pressure adjustment appears. Adjustments are made. In order to avoid this, the delay time (t3) is provided.
[0062]
If it is determined in S8 that the second set temperature is reached, the process proceeds to S9. In S9, the motor-operated valve 6 is fully closed, that is, the inside of the cooling tank 3 is depressurized with the adjustment of the holding pressure reduction being maximized, and the vacuum cooling operation is performed (rapid cooling operation). In the example of FIG. 3, the point R indicates the start point of the rapid cooling operation.
[0063]
In the above embodiment, due to the characteristics of the motor-operated valve 6, it is almost closed by the second opening adjustment and cooled to the second set temperature in the previous period, but the time until the motor-operated valve 6 is fully closed is long. If one is used, the holding pressure can be reduced little by little, and the number of repetitions of the steps from S4 to S7 can be increased.
[0064]
(Effect of Example)
According to the embodiment, when the time change of the product temperature is small, the holding pressure is reduced, and when the time change of the product temperature is small again, the operation of reducing the holding pressure is repeatedly performed. Product temperature and Of the object to be cooled corresponding to the pressure in the treatment tank 3 Without increasing the difference from the saturation temperature, it is possible to suppress the occurrence of an overheated region of the object to be cooled, which is the main cause of boiling. As a result, scattering of the object to be cooled from the pan 8 can be prevented. Further, when the time change of the product temperature is small, the holding pressure is lowered, so that the vacuum cooling operation time can be shortened.
[0065]
Further, according to the embodiment, the first set temperature T0 ° C, the temperature change ΔT1 ° C, the delay time t2min (minutes), and the second set temperature T2 ° C can be adjusted. Even if the type is different, the amount of the object to be cooled is different, or the accommodation state of the object to be cooled in the pan 8 is different (such as the absence of a lid or the depth of the pan 8), the setting is performed. value (First set temperature T0 ° C, temperature change ΔT1 ° C, delay time t2min (minutes), second set temperature T2 ° C) By adjusting one or a plurality of values, a vacuum cooling operation in which boiling is suppressed can be performed.
[0066]
Furthermore, according to the above-described embodiment, without using a pressure sensor, it is possible to prevent bumping and scattering associated with it, or to prevent deformation of the mold, and to perform appropriate cooling suitable for the object to be cooled.
[0067]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent bumping and scattering associated therewith, or prevent deformation of the mold and perform appropriate cooling suitable for the object to be cooled. At the same time, since the amount of reduction of the predetermined value in the holding pressure reduction step is adjusted according to the product temperature, it is possible to effectively prevent the object to be cooled from boiling in the region where the predetermined holding pressure is low. And so on.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view for explaining a vacuum cooling apparatus according to an embodiment to which a vacuum cooling method of the present invention is applied.
FIG. 2 is a flowchart showing a control procedure by the controller of the embodiment.
FIG. 3 is a characteristic diagram showing temporal changes in the product temperature at the bottom of the part to be cooled and the saturation temperature in the treatment tank by the vacuum cooling method of the same example when the object to be cooled is warm water.
[Explanation of symbols]
2 Object to be cooled
3 treatment tank
4 Pressure reducing means
5 Temperature sensor
6 Motorized valve

Claims (2)

A processing tank 3 for storing the object to be cooled 2, a decompression means 4 for decompressing the inside of the processing tank 3, a temperature sensor 5 for detecting the temperature of the object to be cooled 2, and the atmosphere into the processing tank 3 A vacuum cooling method for a vacuum cooling device 1 comprising a motor-operated valve 6 that adjusts a holding pressure in a plurality of stages by introducing a holding pressure,
The pressure reducing means 4 is operated with the opening of the motor-operated valve 6 as a predetermined value so that the pressure in the processing tank 3 reaches a first holding pressure that is finally reached by pressure reduction, and the pressure in the processing tank 3 is reduced. A first pressure holding step to be performed;
A product temperature determination step of determining whether or not the temperature of the object to be cooled 2 detected by the temperature sensor 5 in the first pressure holding step has reached a set temperature;
The final pressure of the temperature sensor 5 the cooling object in temperature of 2 the processing tank 3 by determining the time variation of the temperature of the cooling object 2 to be detected is equal to or less than the reference value by the by vacuum Product temperature time change determination step of determining that the saturation temperature of the object to be cooled 2 corresponding to the holding pressure to be reached is substantially approached,
The product temperature determination step reaching the set temperature is determined by, and the article when the rising time changed by the determination step below the reference value is determined, the pressure of the treatment tank 3 before Kiho predetermined value from lifting pressure include holding pressure reducing step of reducing, and a second pressure holding step of performing the decompression in the treatment tank 3 so that the reduced hold pressure by the holding pressure reduction step,
The product temperature time change determination step and the second pressure holding step are repeatedly performed, and each adjustment of the predetermined value in the holding pressure reduction step when the second pressure holding step is repeated is performed by adjusting the displacement of the decompression means 4. Is performed by adjusting the opening of the motor-operated valve 6 in a plurality of stages, and by decreasing the amount of closing the motor-operated valve 6 as the product temperature of the object to be cooled 2 decreases, the first pressure The holding step, the product temperature time change determining step and the second pressure holding step are performed without using a pressure sensor,
Said predetermined value of said reference value and the holding pressure reduction step of the first holding pressure and the product temperature determining step of the first pressure holding step, that the set to prevent bumping of the object to be cooled 2 A vacuum cooling method characterized by the above.   The vacuum cooling method according to claim 1, wherein the reference value is adjustable.

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