JP2012217391A - Heat sterilization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sterilization device for performing heat sterilization of packaged foods, wherein the heat sterilization device is enabled to perform low cost control of the steam supply amount.SOLUTION: There is provided a heat sterilization device, which performs heat sterilization of objects 2 to be sterilized, by injecting high temperature water to the objects to be sterilized and in a sterilization vessel 1, and is a heat sterilization device detecting the temperature in the sterilization vessel to control the steam supply amount to the high temperature water so that the temperature in the sterilization vessel is the desired value, wherein a steam introduction control device 6 controlling the steam supply amount is provided by setting in series a full open/full shut control valve 6A opened and closed at two positions of full open and full close and a full open/minute open control valve 6B opened and closed at two positions of full open and minute open, and the steam introduction control device 6 performs open and close control of the full open/full shut control valve 6A and the full open/minute open control valve 6B based on the current temperature in the vessel and the calculated estimate of the temperature in the vessel after a predetermined time.

Description

  The present invention relates to a heat sterilization apparatus that heats and sterilizes food in a packaging container after the food such as canned food or retort food is stored in the packaging container.

  Canned and retort food products can be stored at room temperature for a long period of time by heat-sterilizing the internal food in a container after sealed packaging. When heat sterilization is performed, an object to be sterilized is stored in a sterilization tank, and the object to be sterilized is heated by spraying high-temperature circulating water onto the object to be sterilized. If there is an excess or deficiency in the heating of the object to be sterilized, it will be necessary to carry out precise heating control because it may cause spoilage due to insufficient sterilization or alteration of food due to excessive heating. is there. In the heat sterilizer, the temperature in the sterilization tank is detected, and the amount of heating is adjusted so that the temperature in the tank becomes a target value. When the temperature in the tank is lower than the target value, the temperature in the tank is increased by increasing the temperature of the circulating water being injected, and when the temperature in the tank is higher than the target value, the circulating water being injected is increased. The temperature in the tank is lowered by lowering the temperature, and the temperature is adjusted. Steam is generally used as a heat source for heating the circulating water. When the amount of steam supplied to the circulating water is increased, the temperature of the circulating water increases, and when the supply of steam is stopped, the temperature of the circulating water decreases.

   Japanese Patent Application Laid-Open No. 7-231770 describes that an analog pressure regulating valve is provided and the steam supply amount is controlled by adjusting the opening of the analog pressure regulating valve. When the opening degree is sequentially controlled according to the required amount of steam, it is possible to supply steam for the required amount of steam. However, the adjustment valve that can control the opening degree proportionally has a problem of high cost. For this reason, a parallel part is provided in the steam inlet pipe, and control valves that are controlled at two positions of opening and closing, and a plurality of control valves having different calibers are installed in each of the parallel parts, and a valve that is opened according to the required amount of steam is selected. Thus, the steam supply amount is also controlled. In this case, since an inexpensive control valve having two open / close positions can be used, the steam supply amount can be increased or decreased step by step while reducing the cost of the steam introduction control device. However, even in this case, since it is necessary to provide a parallel part in the steam introduction pipe, the cost increases in this part.

JP-A-7-231770

  The problem to be solved by the present invention is to provide a heat sterilization apparatus capable of adjusting a steam supply amount at low cost in a heat sterilization apparatus for heat sterilization of packaged food.

  The invention according to claim 1 is a heat sterilization apparatus that heats and sterilizes an object to be sterilized by spraying high-temperature water onto the object to be sterilized in the sterilization tank, and detects the temperature in the sterilization tank. In the heat sterilization apparatus that controls the steam supply amount for the high-temperature water so that the temperature becomes the target value, the steam introduction control device for controlling the steam supply amount is fully opened / fully opened / closed at two positions of fully open and fully closed. A closed control valve and a full open / micro open control valve that opens and closes in two positions, full open and micro open, are installed in series, and the steam introduction control device uses the current temperature in the tank and the tank after a predetermined time determined by calculation. Based on the predicted value of the internal temperature, the full open / full close control valve and the full open / small open control valve are controlled to open and close.

  According to a second aspect of the present invention, in the heat sterilization apparatus, the steam introduction control sets a target temperature zone having a predetermined width including the target temperature and the target temperature, and the current temperature in the tank is the target. If the temperature is less than the temperature, the fully open / closed control valve is fully opened. If the temperature is higher than the target temperature, the fully open / closed control valve is fully closed. If the predicted temperature after that is less than the lower limit of the target temperature range, the fully open / slightly open control valve is fully opened; otherwise, the fully open / slightly open control valve is slightly opened. And

  When control valves that open and close at two positions are connected in series, an inexpensive control valve can be used, and pipes are not arranged in parallel, so the cost of the steam introduction control device can be reduced. And, in addition to the current tank temperature, based on the predicted value of the tank temperature after a predetermined time, the opening / closing control of the fully open / fully closed control valve and the fully open / microopen control valve is performed. It is possible to prevent the overshoot and undershoot of the internal temperature from increasing.

  When the present invention is implemented, the steam introduction amount can be adjusted by the low-cost steam introduction control device so that the overshoot and undershoot of the temperature in the tank are reduced.

Flow diagram of a heat sterilizer embodying the present invention Explanatory drawing explaining the relationship between the tank internal temperature and steam supply amount in one Example of this invention. Explanatory drawing explaining the relationship between the tank internal temperature and steam supply amount in one Example of this invention.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram of a heat sterilization apparatus embodying the present invention, and FIGS. 2 and 3 are explanatory diagrams for explaining the relationship between the temperature in the tank and the amount of steam supplied. The heat sterilization apparatus sterilizes the object to be sterilized 2 such as canned food or retort food in the cylindrical sterilization tank 1 and heats the object to be sterilized 2 in the sterilization tank 1. A steam introduction pipe 3 for introducing steam and a feed water introduction pipe 5 for introducing feed water are connected to the lower part of the sterilization tank 1. The steam introduction pipe 3 is provided with a steam introduction control device 6, and the steam introduction control device 6 is provided with a fully open / fully closed control valve 6A and a fully open / microopen control valve 6B in series. A water supply control valve 7 is provided in the water supply introduction pipe 5, and the introduction of steam and water supply into the sterilization tank 1 is controlled by controlling the opening and closing of each control valve. A circulation pipe 8 is connected to the bottom of the sterilization tank 1, and the other end of the circulation pipe 8 is connected to an injection nozzle 9 provided in the sterilization tank. A circulation pump 4 is provided in the middle of the circulation pipe 8. When the circulation pump 4 is operated, water at the bottom of the sterilization tank 1 is sent to the injection nozzle 9 through the circulation pipe 8, and the circulation water is supplied from the injection nozzle 9 into the sterilization tank 1. Spray. In the upper part of the sterilization tank 1, an in-tank temperature detector 11 for detecting the in-tank temperature is provided. The operation of the steam introduction control device 6, the water supply control valve 7 and the circulation pump 4 is controlled by the operation control device 10, and the operation control device 10 is also connected to the in-tank temperature detector 11.

  The full opening / full closing control valve 6A and the full opening / small opening control valve 6B constituting the steam introduction control device 6 are control valves that perform operations at two positions of opening and closing, respectively. In the case of the fully open / fully closed control valve 6A, the valve is operated in two positions, fully open and fully closed. However, the fully open / micro open control valve 6B is a control valve with an opening adjustment mechanism, and even when closed, the valve is completely closed. Instead, it is designed to be slightly open allowing a small amount of steam to pass through.

  When performing the heat sterilization of the article 2 to be sterilized, the article 2 to be sterilized is arranged in a tray and stored in the sterilization tank 1 with the trays stacked. Next, water is introduced into the bottom of the sterilization tank 1, and steam is blown into the water accumulated in the bottom to heat the water to a high temperature. Inject hot circulating water toward In the heat sterilization, a temperature raising process for raising the article to be sterilized 2 to the sterilization temperature, a heating process for maintaining the article to be sterilized 2 at the sterilization temperature, and a cooling process for cooling the article to be sterilized 2 are performed. In the temperature raising process and the heating process, when steam is supplied from the steam introduction pipe 3, the temperature of the circulating water injected from the injection nozzle 9 is increased, and when the steam supply is stopped, the circulating water temperature is decreased. Cooling water is introduced from the feed water introduction pipe 5, and the temperature of the circulating water is lowered to cool the article to be sterilized 2.

  In the operation control device 10, an elapsed time from the start of operation and a target value of the temperature in the tank at that time are set, and the temperature in the tank detected by the temperature sensor 11 in the tank is set to the target temperature. Temperature control is performed by controlling the introduction of steam. When steam is supplied to the sterilization tank 1, the temperature of the water stored in the bottom of the sterilization tank rises, and when the circulating water temperature sprayed from the injection nozzle 9 rises, the temperature in the sterilization tank 1 rises. . Conversely, when the supply of steam to the sterilization tank 1 is stopped, the water temperature at the bottom of the sterilization tank decreases and the temperature of the spray water sprayed from the spray nozzle 9 decreases, so the temperature in the sterilization tank 1 decreases. Since the temperature change of the water sprayed on the article to be sterilized 2 spreads spilloverly, even if the steam introduction control valve 6 is closed and the steam supply is stopped, the temperature in the tank rises for a while. Then, even if the steam introduction control valve 6 is opened and steam supply is started, the temperature in the tank continues to decrease for a while. Therefore, when it is detected that the tank temperature has reached the target temperature and the steam introduction control device 6 is operated, the tank temperature passes the target temperature, so that the tank temperature cannot be maintained at the target value. It turns out that.

  Therefore, the operation control device 10 obtains the predicted temperature in the tank after a predetermined time from the control of the steam supply amount based on the current temperature in the tank and the change speed of the temperature in the tank, and changes the steam supply amount in advance. The control which suppresses the overshoot and undershoot of the temperature in a sterilization tank small by this is performed. The predicted value of the tank temperature is calculated by comparing the current tank temperature with the tank temperature before unit time, and calculating the expected tank temperature after a predetermined time, assuming that the change in the tank temperature continues thereafter. Can do.

  As shown in FIGS. 2 and 3, the operation control device 10 maintains a target temperature zone having a certain width (for example, a range from target temperature −0.5 ° C. to target temperature + 1 ° C.). Control steam supply. When the current temperature in the tank detected by the tank temperature detector 11 is lower than the target temperature −0.5 ° C., the operation control device 10 opens the fully open / fully closed control valve 6A to fully open / smallly open. The control valve 6B is fully open or slightly open. Whether the fully open / microopen control valve 6B is fully open or slightly open is determined based on the predicted temperature after a predetermined time. The predicted temperature after a predetermined time is obtained by calculation from the current temperature inside the tank and the rate of change in temperature until then. If the predicted temperature is also less than the target temperature -0.5 ° C, the fully open / micro-open control valve 6B is fully opened, When the predicted temperature is higher than the target temperature -0.5 ° C, the fully open / slightly open control valve 6B is slightly opened. Further, when the current tank temperature detected by the tank temperature detector 11 is between the target temperature -0.5 ° C. and the target temperature, the fully open / fully closed control valve 6A is fully opened and fully opened / smallly opened. The valve 6B is slightly opened. If the current temperature in the tank is equal to or higher than the target temperature, the fully open / fully closed control valve 6A is fully closed, and the fully open / smallly opened control valve 6B is slightly opened.

  When the fully open / fully closed control valve 6A is fully opened and the fully open / microopen control valve 6B is also fully opened, the total opening in the steam introduction control device 6 becomes large, and the amount of steam supplied to the sterilization tank 1 increases. The internal temperature rises. When the fully open / fully closed control valve 6A is fully opened and the fully open / microopen control valve 6B is slightly open, the amount of steam supplied through the steam introduction pipe 3 is a minute opening of the fully open / microopen control valve 6B. In addition, the overall opening degree in the steam introduction control device 6 is reduced, and the amount of steam supplied to the sterilization tank 1 is reduced. Even in this case, since the steam is introduced into the sterilization tank 1, the temperature in the tank rises, but the degree of increase becomes moderate. In this embodiment, the inside temperature of the tank rises due to the amount of steam supplied when it is slightly opened, but the opening degree when it is slightly opened may be set to be the amount of steam supplied so that the inside temperature of the tank decreases. When the fully open / fully closed control valve 6A is fully closed and the fully open / slightly open control valve 6B is slightly open, the fully open / fully closed control valve 6A connected in series is fully closed. The total opening at is closed and the supply of steam to the sterilization tank 1 is stopped. Since the sterilization tank 1 has a temperature drop due to heat dissipation, the temperature in the tank decreases when the steam supply is stopped.

  When the steam supply amount is controlled by combining the current temperature in the tank and the expected temperature after a predetermined time as described above, the current temperature in the tank is the target value −0.5 ° C. as shown in FIG. The steam supply amount is reduced at a time point a lower than that. The tank temperature indicated by the solid line in the figure is for the case where the steam supply amount is reduced by slightly opening / closing the micro-open control valve 6B at time a, and the tank temperature indicated by the broken line is the target temperature minus the detected temperature. The figure shows the case where the steam supply amount is decreased after reaching 0.5 ° C. Even if the steam supply amount is decreased, there is a time lag until the temperature inside the tank starts to change. Therefore, the steam supply is performed by opening the fully open / micro open control valve 6B until the temperature inside the tank reaches the target temperature -0.5 ° C. If it continues, an overshoot occurs in which the temperature in the tank becomes significantly higher than the target temperature, which may damage the food being heated. However, the overshoot of the tank temperature can be suppressed by reducing the steam supply amount at the stage of time a.

  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 sterilization tank
2 Objects to be sterilized
3 Steam inlet pipe
4 Circulation pump
5 Water supply introduction pipe
6 Steam introduction control device 6A Full open / fully closed control valve 6B Full open / micro open control valve
7 Water supply control valve
8 Circulation piping
9 Injection nozzle
10 Operation control device 11 Temperature detector in tank

Claims (2)

  A heat sterilization apparatus for heating and sterilizing an object to be sterilized by spraying high temperature water onto the object to be sterilized in the sterilization tank, wherein the temperature in the sterilization tank is detected, and the temperature in the sterilization tank is set to a target value. In a heat sterilizer that controls the amount of steam supplied to high-temperature water, the steam introduction control device that controls the amount of steam supplied is a fully open / fully closed control valve that opens and closes in two positions, fully open and fully closed, and fully open and slightly open. A full-open / micro-open control valve that opens and closes in two positions is installed in series, and the steam introduction control device is fully open based on the current temperature in the tank and the expected value of the tank temperature after a predetermined time determined by calculation. / Heat sterilizer for controlling opening / closing of a fully-closed control valve and a fully-open / micro-open control valve. In the heat sterilization apparatus according to claim 1, the steam introduction control sets a target temperature zone having a predetermined width including the target temperature and the target temperature, and the current temperature in the tank is lower than the target temperature. When the temperature is higher than the target temperature, the fully open / fully closed control valve is fully closed and the fully open / closed control valve is fully closed. The current tank temperature is less than the lower limit of the target temperature zone, and the predicted temperature after a predetermined time is A heat sterilizer characterized in that if it is less than the lower limit of the target temperature range, the fully open / micro open control valve is fully opened, and otherwise, the full open / micro open control valve is slightly open. .

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