JP5950437B2 - Vacuum cooling device - Google Patents

Description

  The present invention rapidly cools an object to be cooled by storing the object to be cooled such as cooked food in a cooling tank and evaporating moisture in the object to be cooled by depressurizing the inside of the cooling tank. The present invention relates to a vacuum cooling device.

  As described in Japanese Patent No. 3173535, there is known a vacuum cooling device that evaporates moisture from an object to be cooled by reducing the pressure in the cooling tank and cools the object to be cooled by vaporization heat generated by evaporation. . In food service centers and the like, it is required to pass through the temperature range in which miscellaneous germs propagate as soon as possible when cooling cooked food. Cooling to the center of the object to be cooled in a short time is possible with a vacuum cooling device. Is widely used because it is possible. However, when the pressure reduction rate is too high, a bumping phenomenon may occur due to the pressure in the cooling tank being lower than the saturated vapor pressure determined from the product temperature of the object to be cooled. In that case, the object to be cooled may be broken or scattered. Even when air is introduced into the cooling tank after cooling to return the pressure to the cooling tank, the object to be cooled may be deformed if the return pressure speed is too high. For this reason, it is possible to perform slow cooling that slows down the decompression speed in accordance with the properties of the object to be cooled and slow return that slows down the decompression speed after decompression.

  In the vacuum cooling device, a vacuum generator is connected to the cooling tank via a vacuum pipe, and the air in the cooling tank is discharged by operating the vacuum generator. A vacuum cooling pipe provided with a slow cooling valve is connected to the vacuum pipe in the middle so that air can be taken in via the slow cooling pipe. When the slow cooling valve is opened during air suction by the vacuum generator, air is sent to the vacuum pipe through the slow cooling pipe, and the vacuum generator sucks air from the slow cooling pipe in addition to the air in the cooling tank. Therefore, the amount of air discharged from the cooling tank is reduced, and the pressure reduction speed in the cooling tank is reduced. The pressure reduction rate in the cooling tank can also be adjusted by increasing or decreasing the amount of air introduced from the slow cooling valve, and the pressure reduction rate can be increased by increasing the air introduction amount by increasing the opening of the slow cooling valve. If the opening of the slow cooling valve is reduced and the amount of air introduced is reduced, the reduction in the pressure reduction rate is reduced. The same is true for the gradual return at the time of return pressure, and an air intake valve that can adjust the opening is provided in the part where the air for return pressure is introduced into the cooling tank, and the return pressure can be increased by increasing the opening of the air intake valve. The speed increases, and the return pressure speed decreases as the opening of the air intake valve is reduced.

  When performing slow cooling operation or slow return operation, set the elapsed time and the pressure in the cooling tank at that time as the target pressure, and adjust the opening of the slow cooling valve or air intake valve so that it becomes the target pressure While driving. If the tank pressure actually measured is higher than the target pressure set for slow cooling, it means that the pressure reduction speed is insufficient due to the large amount of air taken in by the slow cooling valve. In order to reduce the air intake, the pressure reducing speed is increased. Conversely, if the tank pressure actually measured is lower than the target pressure set for slow cooling, it means that the pressure reduction speed is too fast because the amount of air taken in by the slow cooling valve is small. In that case, the amount of air intake is increased by increasing the opening of the slow cooling valve, and the pressure reduction speed is decreased.

  The amount of change in the opening of the slow cooling valve is determined based on the difference between the target pressure and the pressure in the tank, and the amount of change in the opening of the slow cooling valve increases as the difference between the target pressure and the pressure in the tank increases. Set as follows. PID control is performed, the opening change amount of the slow cooling valve is determined according to the difference with the target pressure, and the opening of the slow cooling valve is adjusted so as to eliminate the difference, so that the pressure in the tank follows the target pressure. Although it should be possible to reduce the pressure, there may actually be a deviation between the tank pressure and the target pressure. If the pressure in the tank does not match the target pressure, the object to be cooled is damaged or scattered due to bumping, and it takes a long time to complete the operation.

Japanese Patent No. 3173535

  The problem to be solved by the present invention is that when performing slow cooling operation or slow return operation with a vacuum cooling device, vacuum cooling that can reduce the deviation of the internal pressure of the tank from the target pressure and increase the accuracy of pressure control. To provide an apparatus.

  The invention described in claim 1 has a cooling tank for storing an object to be cooled and a vacuum generator for discharging the air in the cooling tank, and the inside of the cooling tank is evacuated so as to accommodate the object to be stored in the cooling tank. A vacuum cooling device that cools a cooling object, and is provided with a slow cooling pipe with a slow cooling valve in the middle, and the vacuum pressure is reduced by introducing slow cooling air through the slow cooling valve during vacuum cooling. Slow cooling operation can be performed, and during vacuum cooling operation, the tank pressure detected by the pressure detection device that detects the pressure in the cooling tank is compared with the target pressure set corresponding to the elapsed time. In the vacuum cooling device in which the opening of the slow cooling valve is adjusted so that the pressure in the tank approaches the target pressure, when performing the slow cooling operation, the target pressure and the target pressure are reduced when the degree of vacuum in the cooling tank is low. Proportional band of change amount of slow cooling valve opening to difference in tank pressure As the degree of vacuum in the cooling tank increases as the vacuum cooling operation progresses, the proportional bandwidth of the slow cooling valve opening change amount with respect to the difference between the target pressure and the tank pressure increases. It is characterized by performing.

  According to a second aspect of the present invention, in the vacuum cooling device, the opening degree of the air intake valve is adjusted so that the target pressure set in accordance with the elapsed time is obtained even when the pressure is restored after completion of the vacuum cooling. In this case, when the degree of vacuum in the cooling tank is high, the proportional band width of the change amount of the slow cooling valve opening relative to the difference between the target pressure and the pressure in the tank is increased, and the return pressure operation proceeds. As the degree of vacuum in the cooling tank decreases, the proportional band width of the slow cooling valve opening change amount with respect to the difference between the target pressure and the tank pressure is set to be small.

  The problem during slow cooling is that the vacuum generator operates in the same way, and even if the slow cooling valve operates in the same way, the amount of change in the cooling tank temperature due to the change in the opening of the slow cooling valve is low vacuum. This is because it becomes larger at high vacuum than at times. In the present invention, when performing the slow cooling operation, when the degree of vacuum in the cooling tank is low, the proportional bandwidth of the change amount of the slow cooling valve opening relative to the difference between the target pressure and the tank pressure is reduced, and the vacuum cooling operation is performed. As the degree of vacuum in the cooling tank is lowered by proceeding, the proportional bandwidth of the amount of change in the slow cooling valve opening with respect to the difference between the target pressure and the tank pressure is increased. Then, even if the tank pressure slightly deviates from the target pressure during low vacuum, the opening of the slow cooling valve will be changed relatively large, but even when the tank pressure deviates from the target pressure by the same amount during high vacuum. The amount of change in the opening degree of the slow cooling valve is relatively small. During high vacuum, even if the opening degree of the slow cooling valve is slightly changed, the amount of change in the saturation temperature in the cooling tank becomes large, so that it is difficult to converge the pressure in the tank to the target pressure. However, when the vacuum is high, the change in opening is made gentle so that the amount of pressure fluctuation does not become too large. Conversely, when the vacuum is low, the change in opening is increased so that the amount of fluctuation in pressure is not insufficient. Can do. Therefore, the bumping phenomenon of the object to be cooled can be suppressed and the cooling time can be shortened, and an improvement in yield can be expected.

  The same is true at the time of return pressure, and even if the amount of air intake valve opening change is the same, the amount of change in saturation temperature in the cooling tank increases during high vacuum, and the amount of change in saturation temperature in the cooling tank during low vacuum. Becomes smaller. Also in this case, the width of the proportional band is increased when the vacuum is high, and is decreased as the vacuum is reduced. Then, when the vacuum is high, the amount of change in the opening of the air intake valve with respect to the difference from the target pressure is small, so the amount of change in the pressure in the cooling tank is small, and when the vacuum is low, the amount of change in the opening of the air intake valve is large. Thus, the amount of change in pressure in the cooling tank changes in the increasing direction. As a result, the amount of fluctuation is reduced during a high vacuum where the temperature change with respect to pressure tends to be large, and the amount of fluctuation is enlarged during a low vacuum where the temperature change against pressure tends to be small.

  By carrying out the present invention, when performing a slow cooling operation or a slow return operation, it can be controlled so that the change amount does not become too large at a time when the change amount of the pressure change rate tends to be large. Control can be performed so that the change amount does not become too small at a time when the change amount of the change speed tends to be small. Therefore, the slow cooling operation and the slow return operation along the target pressure can be performed, and both suppression of bumping and shortening of the operation time can be achieved.

Flow diagram of a vacuum cooling apparatus for carrying out the present invention Explanatory drawing explaining the slow cooling valve / air intake valve opening change amount with respect to the deviation from the target pressure during the slow cooling / slow return operation

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of a vacuum cooling apparatus embodying the present invention, and FIG. 2 is an explanatory diagram for explaining an amount of change in opening degree of a slow cooling valve / air intake valve with respect to a deviation from a target pressure during slow cooling / slow return operation. . The vacuum cooling device has a cooling tank 2 that accommodates an object to be cooled 7 and a vacuum generator 1 that discharges air in the cooling tank 2, and is accommodated in the cooling tank 2 by evacuating the inside of the cooling tank 2. The cooled object 7 is cooled.

  The vacuum generator 1 is connected to the cooling tank 2 by a vacuum pipe 9, and the air in the cooling tank 2 is discharged through the vacuum pipe 9 by operating the vacuum generator 1. In order to perform gradual cooling with a slow cooling rate when the object to be cooled 7 is cooled, a gradual cooling pipe 4 provided with a gradual cooling valve 3 is connected to the vacuum pipe 9 and the gradual cooling valve 3 is opened. The outside air enters the vacuum pipe 9 through the slow cooling pipe 4. An electric proportional valve is used as the slow cooling valve 3, and the opening degree of the slow cooling valve 3 can be freely adjusted between 0% and 100%.

  Moreover, since the inside of the cooling tank 2 is in a negative pressure state when the cooling is completed by the vacuum cooling device, it is necessary to return the pressure of the cooling tank 2. In order to return the pressure in the cooling tank 2, a return pressure device having an air intake valve 8 is provided in the cooling tank 2. In the case where it is necessary to perform gradual return that gradually returns even when the pressure is restored, the air intake valve 8 is also an electric proportional valve, and the air intake valve 8 also freely adjusts the opening between 0% and 100%. Be able to do that.

  The cooling tank 2 is provided with a pressure detection device 5 for detecting the pressure in the cooling tank, and the value of the pressure in the cooling tank detected by the pressure detection device 5 is supplied to the operation control device 6 for controlling the operation of the vacuum cooling device. Output. The operation control device 6 controls the operation of each device based on the elapsed time and the tank pressure detected by the pressure detection device 5. The operation control device 6 sets an elapsed time and a target pressure in the cooling tank at that time, and a decompression speed or a decompression speed so that the tank pressure detected by the pressure detection device 5 becomes the target pressure. Adjust. In the present embodiment, the target pressure after the lapse of time A from the start of decompression is -10 kPa, the target pressure after the lapse of time B is -30 kPa, the target pressure after the lapse of time C is -50 kPa, and the target pressure after the lapse of time D is- The target pressure after elapse of 70 kPa and time E is set to −90 kPa.

  When the operation control device 6 performs the slow cooling operation, the operation control device 6 compares the target pressure determined from the time with the tank pressure at that time, and if the tank pressure is higher than the target pressure, the slow cooling valve 3 The opening degree is decreased, and when the tank pressure is lower than the target pressure, the opening degree of the slow cooling valve 3 is increased.

  At this time, in the initial stage of the cooling operation in which the tank internal pressure is high, the proportional band width of the slow cooling valve opening change amount with respect to the difference between the target pressure and the tank internal pressure is reduced, and the tank internal pressure decreases as the cooling process proceeds. The proportional bandwidth of the slow cooling valve opening change amount with respect to the difference between the target pressure and the tank pressure is set so as to increase toward the end of the cooling operation. This will be described with reference to FIG. In FIG. 2, the target pressure value set based on the elapsed time and the opening degree of the slow cooling valve 3 determined based on the tank internal pressure are shown. When the time A has elapsed from the start of the cooling operation, the target pressure is -10 kPa, and when the tank pressure detected by the pressure detection device 5 is higher than the target pressure, -10 kPa, the slow cooling valve 3 The opening degree is decreased, and when it is lower than the target constant value of −10 kPa, the opening degree of the slow cooling valve 3 is increased.

  The width of the proportional band that determines the opening degree of the slow cooling valve based on the pressure in the tank is not simply set to the same value. At the initial stage of the cooling operation, the width of the proportional band is set to be small and as the cooling operation proceeds. Increase the width of the proportional band. At time A, the pressure in the tank is set to 1.0 kPa from 0% of the slow cooling valve opening to 9.1 kPa to the pressure of the slow cooling valve to 100% at the tank pressure of 10.1 kPa. When the tank internal pressure is different by 0.1 kPa, the opening degree of the slow cooling valve is changed by 10%. Here, since the width of the proportional band is set narrow, even when the pressure in the tank is slightly different, the opening change amount of the slow cooling valve becomes large.

  In the case of time B, which is the next explanation point, 3.0 kPa from 0% of the slow cooling valve opening at the tank pressure -27.9 kPa to 100 kPa opening of the slow cooling valve at the tank pressure -30.9 kPa. When the tank pressure is different by 0.3 kPa, the opening degree of the slow cooling valve changes by 10%. Here, although not as much as time A, the width of the proportional band is relatively narrow, so even if the tank pressure is slightly different, the opening change amount of the slow cooling valve is relatively large.

  When time C, which is the next explanatory point, has elapsed, from 0% of the slow cooling valve at a tank internal pressure of -47.5 kPa to 100% of the opening of the slow cooling valve at a tank internal pressure of -52.5 kPa. Of 5.0 kPa, and when the pressure in the tank differs by 0.5 kPa, the opening of the slow cooling valve changes by 10%. Here, the opening degree of the slow cooling valve does not change unless the pressure in the tank further changes more than the time B, but it is not as in the case of time D and time E described later, and is within the range of the description. Setting.

  When the time D has elapsed, the pressure is set at 7.0 kPa from 0% of the slow cooling valve opening at the tank pressure -67.9 kPa to 100% opening of the slow cooling valve at the tank pressure -74.9 kPa. When the pressure in the tank differs by 0.7 kPa, the opening degree of the slow cooling valve changes by 10%. Here, if the tank pressure does not change much more than the time C, the opening degree of the slow cooling valve will not change, and the opening degree change of the slow cooling valve will be relatively gradual.

  When the time E has elapsed, the pressure is set at 9.0 kPa from 0% of the slow cooling valve opening at the tank pressure -89.1 kPa to 100% opening of the slow cooling valve at the tank pressure -98.1 kPa. When the pressure in the tank is different by 0.9 kPa, the opening degree of the slow cooling valve is changed by 10%. Here, since the opening degree of the slow cooling valve does not change unless the pressure in the tank is largely changed, the opening degree change of the slow cooling valve becomes gentle.

  By setting the proportional band that defines the opening degree of the slow cooling valve 3 with respect to the target pressure to be narrow at low vacuum, the width of the proportional band becomes wider as the vacuum becomes higher. The opening degree of the cold valve changes immediately, and the opening degree change of the slow cooling valve becomes gentler as the vacuum becomes higher. This is because the amount of change in temperature relative to the pressure in the cooling tank relative to the pressure in the cooling tank is relatively small during low vacuum, and the amount of change in temperature relative to the pressure in the cooling tank is relatively large during high vacuum. This is because. Therefore, even if the opening of the slow cooling valve is changed in order to bring the pressure inside the tank closer to the target pressure at low vacuum, the target pressure will not be reached. If the opening degree of the slow cooling valve is changed to make it closer, the target pressure tends to be passed.

  In this case, when the vacuum is low at the beginning of the cooling operation, the width of the proportional band is narrowed so that the amount of change in the opening degree of the slow cooling valve becomes large. Is prevented from occurring. Conversely, when the degree of vacuum at the end of the cooling operation is high, the target of the excessive amount of change in the opening of the slow cooling valve is set by increasing the width of the proportional band and reducing the amount of change in the opening of the slow cooling valve. Generation of deviation from pressure is prevented. Thereby, the temperature in the tank can be controlled to match the target temperature in the vacuum cooling step, and the effect of suppressing the bumping phenomenon of the object to be cooled and shortening the cooling time can be obtained.

  Moreover, since the inside of the cooling tank 2 is a high vacuum at the time of completion | finish of cooling operation, and the to-be-cooled object 7 cannot be taken out from the inside of the cooling tank 2, it is necessary to perform the process of vacuum release. In the case of releasing the vacuum, air is introduced into the cooling tank 2 by opening the air intake valve 8. Also in this case, when a problem occurs when the pressure changes abruptly, the gradual return for gradually releasing the vacuum is performed. Also in the case of performing slow return, the width of the proportional band is set to be large at high vacuum, and the width of the proportional band is decreased as the degree of vacuum decreases as the process proceeds. Also in this case, if the opening of the air intake valve 8 is changed in order to bring the pressure inside the tank closer to the target pressure by reducing the amount of change of the opening of the air intake valve 8 during high vacuum, the target pressure is changed. The opening of the air intake valve 8 has been changed to bring the pressure inside the tank closer to the target pressure by preventing the air from passing through and increasing the amount of change in the opening of the air intake valve 8 during low vacuum. Prevents the pressure from reaching the target pressure. Accordingly, the temperature in the tank can be controlled so as to follow the target temperature even in the pressure-recovery step, and an effect of preventing deformation of the object to be cooled and shortening the pressure-reduction time can be obtained even at the time of pressure-return.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

1 Vacuum generator
2 Cooling tank
3 Slow cooling valve 4 Slow cooling pipe 5 Pressure detection device 6 Operation control device 7 Object to be cooled 8 Air intake valve 9 Vacuum piping

Claims (2)

A vacuum cooling device having a cooling tank for storing the object to be cooled and a vacuum generator for discharging the air in the cooling tank, and cooling the object to be cooled stored in the cooling tank by evacuating the inside of the cooling tank In addition, a slow cooling pipe having a slow cooling valve is provided in the middle so that a slow cooling operation can be performed to reduce the decompression speed by introducing air for slow cooling through the slow cooling valve during vacuum cooling. During the vacuum cooling operation, the tank pressure detected by the pressure detection device that detects the pressure in the cooling tank is compared with the target pressure set corresponding to the elapsed time, and the tank pressure approaches the target pressure. In the vacuum cooling device in which the opening degree of the slow cooling valve is adjusted in this way, when performing the slow cooling operation, the slow cooling valve with respect to the difference between the target pressure and the pressure in the tank when the degree of vacuum in the cooling tank is low by reducing the proportional band width of opening change amount, the bath As the pressure relatively large change the opening of the slow cooling valve even if just outside the target pressure, the degree of vacuum in the cooling tank is increased by a vacuum cooling operation progresses, for the difference between the target pressure and the intracisternal pressure By making the proportional band width of the slow cooling valve opening change amount larger, even when the tank pressure deviates from the target pressure by the same amount as above, the opening change amount of the slow cooling valve becomes relatively small. A vacuum cooling device characterized by setting. 2. The vacuum cooling device according to claim 1, wherein a return pressure device having an air intake valve is provided for returning the pressure in the cooling tank after completion of the vacuum cooling, and is set according to the elapsed time even when the pressure is returned. The opening of the air intake valve is adjusted so that the target pressure becomes the same. In this case, when the degree of vacuum in the cooling tank is high, the opening of the air intake valve with respect to the difference between the target pressure and the tank pressure The proportional band width of the air intake valve opening change amount with respect to the difference between the target pressure and the tank pressure decreases as the degree of vacuum in the cooling tank decreases by increasing the proportional band width of the change amount and proceeding with the reverse pressure operation. The vacuum cooling device is characterized in that it is set so that it goes on.

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