Method for controlling a heating element and heater

Abstract

To provide a control method of a heating element and a heater capable of increasing a temperature of an object to be heated to a target temperature accurately in a short time.SOLUTION: A control method of a heating element of the present disclosure includes the steps of: setting a target temperature of an object to be heated; operating the heating element to heat a structure that contacts the object to be heated; detecting a temperature rise speed of the structure at predetermined timing after the start of the heating; calculating a time required for the object to be heated to reach the target temperature from the temperature change; and notifying that the time required to reach the target temperature has elapsed.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for controlling a heating element that heats an object and a heater.

Background Art

[0002] Heaters that heat a heat-retaining object, such as a retort food in which a heated object, for example, cooked food, etc. is stored inside a pouch, using a heating element are widely used. For example, as a device for heating (warming) retort food, Patent Document 1 below describes a device that sandwiches a retort food inserted from an opening between hot plates by pressing it from one side, and heats the hot plates with a heater having a constant output to warm the retort food.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the device of Patent Document 1 above, the ambient temperature inside the device is detected by a temperature sensor, and heating and cooking control is performed based on whether or not the ambient temperature has reached a predetermined temperature. However, in the method described above, since the temperature near the surface of the retort food is measured, it may be different from the actual temperature of the contents. Furthermore, it is expected that there will be a difference in the finished temperature depending on the contents of the retort food.

[0005]

Means for Solving the Problems

[0006] To achieve the above objective, a heating element control method according to a first aspect of the present disclosure includes the steps of: setting a target temperature for an object to be heated; heating a structure in contact with the object to be heated by operating the heating element; detecting a temperature change of the structure at a predetermined timing after the start of heating; calculating the time it takes for the object to be heated to reach the target temperature from the temperature change; and notifying that the time to reach the target temperature has elapsed.

[0007] In this type of heating element control method, the time it takes for the object to be heated to reach the target temperature is calculated from the temperature change of the structure, making it possible to raise the object to be heated to the target temperature quickly and accurately.

[0008] A method for controlling a heating element according to a second aspect of the present disclosure, wherein the step of calculating the time it takes for the object to be heated to reach the target temperature from the heating rate is to apply a virtual thermal circuit to a heater including the heating element, and use the thermal circuit to calculate the time it takes for the object to be heated to reach the target temperature from the detected heating rate.

[0009] In this type of heating element control method, the time it takes for the object to be heated to reach the target temperature can be calculated with high accuracy.

[0010] A method for controlling a heating element according to a third aspect of the present disclosure includes the steps of: setting a target temperature for an object to be heated; heating a structure in contact with the object to be heated by operating a heating element; detecting a temperature change of the structure at a predetermined timing after the start of heating; calculating from the temperature change the target temperature of the structure and the time it takes for the object to be heated to reach the target temperature; detecting whether the temperature of the structure has reached the target temperature; stopping the heating of the heating element when it is detected that the temperature of the structure has reached the target temperature; and notifying that the time to reach the target temperature has elapsed.

[0011] In this method of controlling a heating element, the object to be heated can be raised to the target temperature in a short time and without overshooting the target temperature.

[0012] A control method for a heating element according to a fourth aspect of the present disclosure is a control method for a heating element according to any of the first to third aspects of the present disclosure, wherein the predetermined timing is the timing when the rate of change of the heating rate per unit time becomes 3% or less, the timing when a preset elapsed time from the start of heating has elapsed, or the timing when the structure reaches a preset temperature.

[0013] In this method of controlling a heating element, temperature changes are detected only after the heating rate has stabilized, allowing for accurate identification of temperature changes within the structure.

[0014] A fifth aspect of the present disclosure relates to a method for controlling a heating element, wherein, in any of the first to fourth aspects of the present disclosure, the object to be heated contains a liquid, and the heating element is controlled to bring the temperature of the liquid to the target temperature.

[0015] In this method of controlling a heating element, even if the object to be heated contains liquid, the contents of the object to be heated will not be excessively heated, thus allowing for safe heating.

[0016] A method for controlling a heating element according to a sixth aspect of the present disclosure, in a method for controlling a heating element according to any third to fifth aspect of the present disclosure, the step of calculating the time it takes for the object to be heated to reach the target temperature from the heating rate is to apply a virtual thermal circuit to a heater including the heating element, and use the thermal circuit to calculate the time it takes for the object to be heated to reach the target temperature from the detected heating rate.

[0017] In this type of heating element control method, the time it takes for the object to be heated to reach the target temperature can be calculated with high accuracy.

[0018] A method for controlling a heating element according to a seventh aspect of the present disclosure includes the steps of: setting a target temperature for an object to be heated; heating a structure in contact with the object to be heated by operating a heating element; detecting the temperature rise of the structure at a predetermined timing after the start of heating; calculating the time it takes for the object to be heated to reach the target temperature from the rate of heating; calculating the heating time for the heating to be performed from the temperature rise; detecting whether the heating time has elapsed; stopping the heating of the heating element when the elapsed heating time has been detected; and notifying that the time to reach the target temperature has elapsed.

[0019] In this method of controlling a heating element, the object to be heated can be raised to the target temperature in a short time and without overshooting the target temperature.

[0020] A method for controlling a heating element according to an eighth aspect of the present disclosure, in a method for controlling a heating element according to a seventh aspect of the present disclosure, the step of calculating the time it takes for the object to be heated to reach the target temperature from the heating rate is to apply a virtual thermal circuit to a heater including the heating element, and use the thermal circuit to calculate the time it takes for the object to be heated to reach the target temperature from the detected heating rate.

[0021] In this type of heating element control method, the time it takes for the object to be heated to reach the target temperature can be calculated with high accuracy.

[0022] The method for controlling a heating element according to the ninth aspect of the present disclosure includes a step of setting a target temperature of an object to be heated, a step of heating a structure in contact with the object to be heated by operating a heating element, a step of detecting a temperature increase rate of the structure at a predetermined timing after starting the heating, a step of calculating a time for the object to be heated to reach the target temperature from the temperature increase rate, a step of detecting whether the temperature of the structure has reached a predetermined upper limit temperature higher than the target temperature, a step of controlling the heating element to maintain the upper limit temperature when it is detected that the temperature of the structure has reached the upper limit temperature, and a step of notifying that the time for reaching the target temperature has elapsed.

[0023] In such a method for controlling a heating element, the temperature of the object to be heated can be raised to the target temperature in a short time without overheating the object to be heated.

[0024] The method for controlling a heating element according to the tenth aspect of the present disclosure is the method for controlling a heating element according to the ninth aspect of the present disclosure, wherein the step of calculating a time for the object to be heated to reach the target temperature from the temperature increase rate applies a virtual thermal circuit to a heater including the heating element, and calculates a time for the object to be heated to reach the target temperature using the thermal circuit from the detected temperature increase rate.

[0025] In such a method for controlling a heating element, the time for the object to be heated to reach the target temperature can be accurately calculated.

[0026] The method for controlling a heating element according to the 11th aspect of the present disclosure includes a step of setting a target temperature of an object to be heated, a step of heating a structure that contacts the object to be heated by operating a heating element, a step of stopping the heating at a predetermined timing after starting the heating, a step of detecting a temperature change of the structure after stopping the heating, a step of calculating a time for the object to be heated to reach the target temperature from the temperature change, a step of restarting the heating of the structure by operating the heating element, a step of detecting whether the temperature of the structure has reached a predetermined upper limit temperature higher than the target temperature, a step of controlling the heating element to maintain the upper limit temperature when it is detected that the temperature of the structure has reached the upper limit temperature, and a step of notifying that the time for reaching the target temperature has elapsed.

[0027] In such a method for controlling a heating element, the temperature of the object to be heated can be raised to the target temperature in a short time without overheating the object to be heated. Further, the calculation of the time for reaching the target temperature can be performed with high accuracy.

[0028] The method for controlling a heating element according to the 12th aspect of the present disclosure is the method for controlling a heating element according to the 11th aspect of the present disclosure, wherein the step of calculating the time for the object to be heated to reach the target temperature from the temperature change applies a virtual thermal circuit to a heater including the heating element, and calculates the time for the object to be heated to reach the target temperature using the thermal circuit from the detected temperature change.

[0029] In such a method for controlling a heating element, the time for the object to be heated to reach the target temperature can be accurately calculated.

[0030] The heater according to the 13th aspect of the present disclosure includes an installation portion where an object to be heated is disposed, a structure that contacts the object to be heated disposed in the installation portion, a heating element that heats the structure, a temperature detection portion that detects the temperature of the structure, and a control portion that performs each step of the method for controlling a heating element according to any one of the 1st to 12th aspects based on the detection result of the temperature detection portion.

[0031] In such a heater, the object to be heated can be raised to the target temperature in a short time and without overshooting the target temperature.

[0032] A heater according to a fourteenth aspect of the present disclosure is a heater according to a thirteenth aspect of the present disclosure, wherein the mounting portion is provided between a pair of structures that face each other at a predetermined distance apart, and the heating element is provided on at least one of the pair of structures.

[0033] In such a heater, the object to be heated, which is installed in the mounting section, is heated while sandwiched between a pair of structures. This ensures a sufficient contact area between the structures and the object to be heated, allowing the object to be heated evenly. [Effects of the Invention]

[0034] According to the heating element control method and heater of this disclosure, it is possible to raise the temperature of an object to be heated to a target temperature in a short time with high accuracy. [Brief explanation of the drawing]

[0035] [Figure 1] This is a schematic perspective view showing an example of a heater according to the first embodiment of this disclosure. [Figure 2] Figure 1 is an exploded perspective view showing the heater in its disassembled state. [Figure 3] Figure 1 is an explanatory diagram showing an example of the operating state when inserting retort food into the heater shown in Figure 1 from above. [Figure 4] This flowchart shows an example of a method for controlling a heating element according to the first embodiment of this disclosure. [Figure 5] This graph shows an example of the temperature change of a structure when the heating element control method shown in Figure 4 is implemented. [Figure 6] This graph shows an example of the relationship between the heating rate of a structure and the target temperature when the heating element control method shown in Figure 4 is implemented. [Figure 7]This flowchart shows an example of a method for controlling a heating element according to a second embodiment of the present disclosure. [Figure 8] This graph shows an example of the temperature change of a structure when the heating element control method shown in Figure 7 is implemented. [Figure 9] Figure 7 shows an example graph illustrating the relationship between the heating rate of a structure and the heating time when the heating element control method shown is implemented. [Figure 10] This is a flowchart showing an example of a method for manufacturing a heating element according to the third embodiment of this disclosure. [Figure 11] This graph shows an example of the temperature change of a structure when the heating element control method shown in Figure 10 is implemented. [Figure 12] This is a flowchart showing an example of a method for manufacturing a heating element according to the fourth embodiment of this disclosure. [Figure 13] This graph shows an example of the temperature change of a structure when the heating element control method shown in Figure 12 is implemented. [Figure 14] This is a schematic diagram showing a virtual heat circuit applied to the heater shown in Figure 1. [Figure 15] This figure shows a simplified and enlarged version of section E in Figure 14. [Modes for carrying out the invention]

[0036] The following describes various embodiments for implementing this disclosure with reference to the drawings. In the following, only the extent necessary to explain the objectives of this disclosure will be schematically shown, and the explanation will primarily focus on the extent necessary to explain the relevant parts of this disclosure. Any parts that are omitted from the explanation will be considered to be covered by prior art.

[0037] <First Embodiment> Figure 1 is a schematic perspective view showing an example of a heater according to the first embodiment of this disclosure. Figure 2 is an exploded perspective view showing the heater shown in Figure 1 in a disassembled state. The heater 1 according to the first embodiment of this disclosure may be capable of heating (warming) a retort food PF (see Figure 3) as an example of an object to be heated. In the following description, the direction indicated by arrow X in Figure 1 will be considered the front-back direction, the direction indicated by arrow Y will be considered the left-right direction, and the direction indicated by arrow Z will be considered the up-down direction.

[0038] The retort food PF heated by the heater 1 according to this embodiment may include, for example, a pouch P (see Figure 3) containing liquid inside, but its size and contents are not particularly limited. The pouch P may be, for example, one made of a packaging material such as a laminated synthetic resin film or metal foil (e.g., aluminum foil), with the perimeter sealed to create a space for sealing liquid-containing food inside. Furthermore, this pouch P may be self-standing or non-self-standing.

[0039] As shown in Figures 1 and 2, the heater 1 may include at least a pair of rectangular parallelepiped-shaped wall sections 10 and 20 arranged opposite each other at a predetermined distance apart. Between the pair of wall sections 10 and 20, there is an installation section 30 on which the retort food PF, which is to be heated, is placed. The pair of wall sections 10 and 20 may be arranged opposite each other via the installation section 30, and more preferably, they should be arranged substantially parallel to each other. Hereinafter, the section located to the left of the installation section 30 when the heater 1 is viewed from the front will be referred to as the first wall section 10, and the section located to the right of the installation section 30 will be referred to as the second wall section 20. Note that the aforementioned "rectangular parallelepiped shape" is not limited to those with all corners at right angles, but also includes those with some faces inclined or some corners chamfered.

[0040] The first wall portion 10 may include a first wall portion body 11 and a first heating portion 12, as shown in particular in Figure 2. Of these, the first wall portion body 11 accommodates at least a part of the first heating portion 12 and may be made of synthetic resin or the like. The first wall portion body 11 in this embodiment may, together with the second wall portion body 21, front housing 31, rear housing 32, and bottom housing 33 described later, constitute the housing of the heater 1. Furthermore, this first wall portion body 11 can be made of a plate-like body that is bent to cover the upper part and left side of the first heating portion 12, for example.

[0041] The first heating unit 12 may heat a retort food PF disposed within the installation unit 30, with its periphery, other than the portion facing the installation unit 30, at least partially covered by the first wall unit body 11. This first heating unit 12 includes at least a first structure 13 that can contact the retort food PF disposed within the installation unit 30, and a first heating element 14 that can heat the first structure 13. The first structure 13 and the second structure 23 described later correspond to examples of structures in this embodiment, and the first heating element 14 and the second heating element 24 described later correspond to examples of heating elements in this embodiment.

[0042] The first structure 13 functions as a heat transfer element that transmits heat from the first heating element 14 to the retort food PF, and can be made of a plate-like body made of a material with high thermal conductivity, such as iron, aluminum, or an alloy thereof. The surface of this first structure 13 facing the installation portion 30 functions as the heating surface. In addition, fixing pieces 13A, which will be fixed to the first cover member 15 described later, may be erected on the back side (i.e., towards the left in Figure 2) around the outer circumference of the first structure 13.

[0043] The first heating element 14 can be a rectangular heater having a shape similar to that of the first structure 13. For example, the first heating element 14 can be a polyimide heater, a rubber heater with a nichrome wire inside, etc. The first heating element 14 may also be positioned in contact with or close to the back surface (the left side in Figure 2) of the first structure 13. The heat generated from the first heating element 14 by the application of electricity is transferred via the first structure 13 to the retort food PF inserted into the installation section 30, more specifically, to the contents containing liquid enclosed in the pouch P.

[0044] In addition, the first heating section 12 may include a first cover member 15 that supports the first structure 13 and the first heating element 14. This first cover member 15 may be a member capable of supporting the first structure 13 and the first heating element 14 in contact with each other, and can be made up of a rectangular shape. This first cover member 15 can be fixed to the fixing piece 13A of the first structure 13, thereby fixing the relative position of the first heating element 14 and the first structure 13. The first cover member 15 can be made of a heat-resistant material, such as mica or a heat-resistant resin.

[0045] The second wall section 20 may be arranged symmetrically with respect to the first wall section 10 and the installation section 30, and its specific configuration may be the same as that of the first wall section 10. That is, the second wall section 20 may include a second wall section body 21 and a second heating section 22. Of these, the second wall section body 21 is capable of housing at least a part of the second heating section 22 and may be made of synthetic resin or the like. The second wall section body 21, like the first wall section body 11, may also constitute the housing of the heater 1 together with the front housing 31 and the rear housing 32. Furthermore, the second wall section body 21 may be made of a plate-like body that is bent to cover the upper part and left side of the second heating section 22, for example.

[0046] The second heating section 22 includes a second structure 23 having a fixing piece 23A around its outer circumference, the surface of which contacts the retort food PF contained in the installation section 30, and a second heating element 24 provided on the back side of the second structure 23 for heating the second structure 23. The second heating section 22 may further include a second cover member 25 attached to the back side of the second heating element 24 to support the second structure 23 and the second heating element 24. The detailed structure of each component of the second heating section 22 described above will be based on the information provided for the first heating section 12, and will not be described here.

[0047] According to the above configuration, the installation section 30 is provided between the first and second structures 13 and 23, which are facing each other with a predetermined distance between them. In addition, the first and second heating elements 14 and 24 are arranged on the sides of the first and second structures 13 and 23 opposite to the installation section 30, respectively, but it is also possible to use only one of these heating elements.

[0048] Between the first wall body 11 of the first wall portion 10 and the first heating portion 12, and between the second wall body 21 of the second wall portion 20 and the second heating portion 22, first and second biasing members 16 and 26 may be provided to bias the first and second heating portions 12 and 22 toward the installation portion 30. Specifically, the first biasing member 16 may bias the first structure 13 toward the second heating surface of the second wall portion 20, and the second biasing member 26 may bias the second structure 23 toward the first heating surface of the first wall portion 10. Various biasing means such as coil springs can be used as these first and second biasing members 16 and 26. The first and second biasing members 16 and 26 can be arranged such that one end contacts the inner surface of the first and second wall body 11 and 21, and the other end contacts a suitable location on the back surface of the first and second heating section 12 and 22, that is, on the back surface of the first and second cover members 15 and 25.

[0049] Figure 3 is an explanatory diagram showing an example of the operating state when inserting retort food into the heater shown in Figure 1 from above. Figure 3(A) shows the state before the retort food is inserted into the containment space, and Figure 3(B) shows the state after the retort food is inserted into the containment space. Because the first and second biasing members 16 and 26 include the above-described configuration, the first and second heating sections 12 and 22 are constantly biased toward the installation section 30. The first and second heating sections 12 and 22, which are biased toward the installation section 30 in this way, may protrude toward the installation section 30 by a predetermined length relative to the end faces 11A and 21A of the first and second wall sections 11 and 21 toward the installation section 30 before the retort food PF is contained. The respective protruding lengths W1 of the first and second heating sections 12 and 22 may be, for example, 3 to 6 mm, preferably 4 to 5 mm, and more preferably about 4.5 mm, as shown in Figure 3(A). The first and second heating sections 12 and 22 can move in a direction away from each other by the amount of their protruding length W1, against the biasing force of the first and second biasing members 16 and 26. Alternatively, instead of using the first and second biasing members 16 and 26, the first and second structural elements 13 and 23 may be fixed to the first and second wall bodies 11 and 22.

[0050] The width W2 of the mounting section 30 in the left-right direction may be adjusted as appropriate to match the general width of retort food PF. Specifically, the width W2 of the mounting section 30 can be adjusted as appropriate between 17 and 27 mm. For example, if the width W2 of the mounting section 30 is set to 22 mm and the protruding lengths W1 of the first and second heating sections 12 and 22 described above are set to 4.5 mm, the distance between the first and second structures 13 and 23 will be a minimum of 13 mm and a maximum of 22 mm. As described above, by adjusting the distance between the first and second structures 13 and 23 to 13 to 22 mm, retort food PF with a wall thickness W3 of at least 13 to 22 mm can be reliably sandwiched between the first and second structures 13 and 23 and heated.

[0051] Furthermore, the heater 1 according to this embodiment includes temperature detection units 17 and 27 capable of detecting the temperature of at least one of the first and second structures 13 and 23. In this embodiment, as shown in Figure 2, an example is provided in which a first temperature detection unit 17 and a second temperature detection unit 27 are provided on both the first wall 10 and the second wall 20, respectively, to detect the temperatures of the first and second structures 13 and 23.

[0052] The first and second temperature sensing units 17 and 27 can be configured, for example, as contact-type temperature sensors. These first and second temperature sensing units 17 and 27 may be attached to sensor mounting parts 15M and 25M provided in the approximate center of the first and second cover members 15 and 25 in the vertical and front-to-back directions. Furthermore, the sensing surfaces 17A and 27A of the first and second temperature sensing units 17 and 27 may be in contact with the back surface opposite to the surface of the first structure (also called the "heating plate") 13 that functions as the first heating surface, and the back surface opposite to the surface of the second structure 23 that functions as the second heating surface. In addition, the sensing surfaces 17A and 27A of the temperature sensing units 17 and 27 according to this embodiment are in contact with the back surfaces of the first and second structures 13 and 23 via through holes 14H, 24H, 15H, and 25H provided in the first and second heating elements 14 and 24 and the first and second cover members 15 and 25, respectively. Note that the sensor mounting portion 15M and the through hole 15H are hidden by other components in Figure 2 and are therefore not visible, so their reference numerals have been omitted.

[0053] The heater 1 according to this embodiment may further include three housings 31, 32, and 33 that cover the front, rear, and bottom portions of the first and second wall portions 10 and 20, in addition to the first and second wall portions 10 and 20 described above. Of these, the front housing 31 and the rear housing 32 can be formed from a member made of the same material as the first and second wall portion bodies 11 and 21, for example, and are shaped in a substantially U-shape when viewed from the front, as shown in Figure 2. The U-shaped openings of the front housing 31 and the rear housing 32 should preferably be pre-adjusted to communicate with the installation portion 30 when attached to the first and second wall portions 10 and 20.

[0054] The bottom housing 33 is disposed on the bottom surface of the heater 1 and has multiple (for example, four) legs 33A attached to each corner. It can be formed from a component made of the same material as the first and second wall bodies 11 and 21. A main control board 41, which constitutes a control unit 40 that controls the first and second heating elements 14 and 24 based on the detection results of the first and second temperature sensing units 17 and 27, may be disposed on this bottom housing 33.

[0055] Furthermore, a partition plate 34 (see Figure 3) may be provided above the main control board 41 to separate the main control board 41 from the installation section 30. This partition plate 34 can be made of a plate-like body that extends substantially parallel to the bottom housing 33, and its upper surface can function as the bottom surface of the installation section 30. Therefore, it is preferable that the upper surface of this partition plate 34 is located on the same plane as the lower surface of the front opening 31A and the lower surface of the rear opening 32A, as this makes it less likely for dirt and other debris to accumulate between these components, thus facilitating cleaning. Note that the partition plate 34 is not shown in Figure 2.

[0056] The control unit 40 included in the heater 1 according to this embodiment is capable of controlling the first and second heating elements 14 and 24, and may mainly include a main control board 41. This main control board 41 may be electrically connected to the first and second heating elements 14 and 24. In connection with this, the main control board 41 may also be electrically connected to the first and second temperature sensing units 17 and 27. To supply power to the first and second heating elements 14 and 24, the main control board 41 may be connected to a power cord 42 having a power plug at its end. Furthermore, the main control board 41 may have various electronic components such as capacitors and resistors mounted on it that are used when performing various types of control. The method of controlling the heating elements that can be implemented by the control unit 40 will be described later.

[0057] The right surface of the front housing 31 may include a switch for operating the heater 1, such as a start switch 43 that can switch the heater 1 ON / OFF. This start switch 43 may be mounted on a switch mounting board 45 which is part of the control unit 40 located on the back surface of the front housing 31, and this switch mounting board 44 may be connected to the main control board 41.

[0058] Furthermore, the heater 1 according to this embodiment may include a temperature setting switch 50 as an input unit that can input a target temperature T0, which is the target temperature when heating the retort food PF. This temperature setting switch 50 may be electrically connected to the main control board 41 by being mounted on the switch mounting board 44, similar to the start switch 43.

[0059] In this embodiment, the temperature setting switch 50 can be configured to allow for stepwise selection of the target temperature of the retort food PF. Specifically, by pressing the temperature setting switch 50, it is preferable to allow the user to select a desired temperature from a predetermined set of target temperatures (for example, 100°C, 85°C, 70°C, 55°C, etc.). The number and types of predetermined target temperatures can be changed as appropriate.

[0060] In relation to the above, a display unit 51 capable of displaying the target temperature selected by operating the temperature setting switch 50 may be provided above the temperature setting switch 50. An example of a display unit 51 in this embodiment is one composed of a number of LED lamps corresponding to the selectable target temperature (for example, 4). In addition to LED lamps, other display means such as a liquid crystal monitor can be used for this display unit 51. By providing this display unit 51, users can grasp the selected target temperature at a glance.

[0061] In this embodiment, a start switch 43 and a temperature setting switch 50 are exemplified as switches for operating the heater, but the switches of this disclosure are not limited to these two. For example, in order to heat the retort food PF with greater precision, a switch that can input the volume (weight) of the retort food RF or a switch that can input the contents of the retort food PF (e.g., soup, curry, water) can also be used.

[0062] Furthermore, to inform the user of the operating status of the heater 1 and the temperatures of the first and second structures 13 and 23, it is advisable to install a lamp 53 in an appropriate location on the housing of the heater 1. The lamp 53 in this embodiment may function as a warning light that illuminates when the first and second structures 13 and 23 are at a high temperature.

[0063] In this embodiment, the lamp 53 is positioned to extend from the front end of the upper surface of the second wall portion 20 to the upper end of the front housing 31 on the second wall portion 20 side, in order to improve its visibility. With the lamp 53 positioned as described above, it can be seen from either the top or front side of the heater 1. Therefore, for example, when the lamp 53 is lit to indicate that the first and second structures 13 and 23 are hot, the user is unlikely to overlook the lit state of the lamp 47. Consequently, accidents such as the user accidentally touching the hot first and second structures 13 and 23 can be suppressed.

[0064] In this embodiment, an example is given in which one lamp 53 is placed at the front end portion of the second wall portion 20. However, the arrangement, shape, number, etc., of the lamps 53 can be changed as appropriate, as long as the above-described effects can be expected. Specifically, the lamps 53 should be arranged at least at one location on the outer edge of the upper surface of the first wall portion 10 or the second wall portion 20, extending from the upper surface of the first wall portion 10 or the second wall portion 20 to another surface adjacent to the upper surface of the first wall portion 10 or the second wall portion 20.

[0065] As shown in Figure 1, the heater 1, which includes the series of configurations described above, has a rectangular mounting section 30 sandwiched between the first and second walls 10 and 20, with three sides of the outer circumference, excluding the bottom surface, open to the outside of the heater 1. Therefore, when heating retort food PF using the heater 1, the retort food PF can be placed inside the mounting section 30 of the heater 1 by inserting it through one of the three openings described above.

[0066] Furthermore, when heating a retort food PF as the object to be heated using the heater 1 which includes the series of configurations described above, first, as shown in Figure 3(A), the retort food PF is moved in the direction of the arrow in the figure and inserted into the installation section 30 from the upper opening of the heater 1. When the retort food PF is inserted into the installation section 30, the first and second structures 13 and 14 move so as to be pushed outwards in the left and right directions against the biasing force of the first and second biasing members 16 and 26 by the pouch P of the retort food PF. Once the insertion of the retort food PF into the installation section 30 is complete, the first and second structures 13 and 23 are pressed against the pouch P by the biasing force from the first and second biasing members 16 and 26, as shown in Figure 3(B).

[0067] After reaching the state shown in Figure 3(B), when the user operates the start switch 43, the control unit 40 executes control of the first and second heating elements 14 and 24. The following describes the control method for the heating elements according to this embodiment. The control method for the heating elements according to this embodiment can be implemented, for example, by the control unit 40 of the heater 1 described above. Therefore, the control method for the heating elements according to this embodiment can be provided in the form of a program such as software containing commands for a computer configured on the main control board 41 to execute a predetermined operation, in the form of a non-temporary recording medium on which this program is stored, or in the form of an application program provided via a network or the like.

[0068] The amount of heat and heating time required to reach the target temperature vary depending on the type of retort food PF, as the size of the pouch P and the contents of the retort food PF vary widely. Therefore, if a device that heats with a constant heater output is used, for example, as described in Patent Document 1 above, increasing the heater output may cause the temperature of the contents of the pouch P to rise above the target temperature, depending on the type of retort food PF. Therefore, there is a limit to how much the heating time can be shortened by increasing the heater output. In this case, it will take a relatively long time to heat the retort food PF to the target temperature. In the heating element control method according to this embodiment, taking the above points into consideration, the following steps are adopted in order to complete heating in a short time without overshoot, according to the heat capacity and size of the retort food PF.

[0069] The heating element control method according to this embodiment includes at least the steps of: setting a target temperature T0 of the retort food PF (S01); heating at least one of the first and second structures 13 and 23 that come into contact with the retort food PF by operating at least one of the first and second heating elements 14 and 24 (S02); detecting the rate of heating of the first and second structures 13 and 23 at a predetermined timing after heating has started (S04); calculating the time t0 for the retort food PF to reach the target temperature T0 from the rate of heating (S05); and notifying that the time t0 for reaching the target temperature T0 has elapsed (S09).

[0070] More specifically, the heating element control method according to this embodiment includes the steps of: setting a target temperature T0 of the retort food PF (S01); heating at least one of the first and second structures 13 and 23 that come into contact with the retort food PF by operating at least one of the first and second heating elements 14 and 24 (S02); detecting the rate of heating of the first and second structures 13 and 23 at a predetermined timing after heating has started (S04); and determining from the rate of heating that the first and second structures are higher than the target temperature T0. The process includes the steps of: calculating the target temperature Tr of the bodies 13 and 23 and the time t0 for the retort food PF to reach the target temperature T0 (S05); detecting whether the temperature of the first and second structures 13 and 23 has reached the target temperature Tr (S06); stopping the heating of the first and second heating elements 14 and 24 when it is detected that the temperature of the first and second structures 13 and 23 has reached the target temperature Tr (S07); and notifying that the time t0 for reaching the target temperature T0 has elapsed (S08). The process will be explained in more detail below, mainly with reference to Figures 4 and 5.

[0071] Figure 4 is a flowchart showing an example of a heating element control method according to the first embodiment of this disclosure. Figure 5 is a graph showing an example of the temperature transition of a structure when the heating element control method shown in Figure 4 is implemented. In Figure 5, the solid line graph shows the temperature transition of the first and second structures 13 and 23 detected by the first and second temperature detection units 17 and 27, while the dashed line graph shows the estimated temperature of the contents of the retort food PF at the same point in time. As shown in Figure 3(B), when the retort food PF is placed in the installation unit 30 and the start switch 43 is pressed, the control unit 40 then acquires the target temperature T0 (step S01). The target temperature T0 can be set to any temperature, for example, by the user operating the temperature setting switch 50.

[0072] When the target temperature T0 is obtained, the control unit 40 supplies power to the first and second heating elements 14 and 24 to start heating the retort food PF. At this time, the control unit 40 operates the first and second heating elements 14 and 24 to raise the temperature of the first and second structures 13 and 23 and the retort food PF in contact with them (step S02). During this heating, regardless of the value of the target temperature T0, the first and second heating elements 14 and 24 can be operated to maximize the amount of heat generated, for example. As shown in Figure 5, the temperature of the contents of the retort food PF rises with a delay compared to the temperature rise of the first and second structures 13 and 23.

[0073] When heating begins, the control unit 40 detects the temperature change of the first and second structures 13 and 23. Specifically, in order to measure the heating rate S of the first and second structures 13 and 23, a timer (not shown) is operated to measure the elapsed time from the start of heating and detect whether a predetermined time t1 has been reached (step S03). The predetermined time t1 may be set considering the timing at which the heating rate of the first and second structures 13 and 23 stabilizes after heating has started. In this embodiment, the timing at which the heating rate stabilizes is defined by detecting the elapsed time t1, but the timing at which the heating rate stabilizes can also be defined by other methods. Specifically, the timing at which the rate of change of the heating rate per unit time becomes 3% or less, or the timing at which the first and second structures 13 and 23 reach a preset temperature, may be defined as the timing at which the heating rate stabilizes.

[0074] When a predetermined time t1 has elapsed (Yes in step S03), the control unit 40 calculates the heating rate S (step S04). Various methods can be used to calculate the heating rate S. For example, the detection results of the first and second temperature detection units 17 and 27 can be obtained multiple times (for example, three times) at equal time intervals (for example, 1-second intervals), and a regression line using the least squares method can be calculated from these multiple detection results. The heating rate S can then be derived by referring to this line.

[0075] The heating rate S derived here is a value that correlates with the weight of the retort food PF and its contents. Therefore, by controlling the heating element using this heating rate S, it is possible to accurately achieve heating that matches the weight and contents of the retort food PF.

[0076] Once the heating rate S is calculated, the control unit 40 then calculates the target temperature Tr (step S05). The target temperature Tr is set to a temperature higher than the target temperature T0 and can be calculated, for example, by the following equation (1).

number

[0077] Figure 6 is a graph showing an example of the relationship between the heating rate and the target temperature of a structure when the heating element control method shown in Figure 4 is implemented. In Figure 6, the relationship between the heating rate S and the target temperature Tr when the target temperature T0 is 80°C, 70°C, 60°C, and 50°C is shown by an approximate straight line. This approximate straight line can be derived from the values ​​of the heating rate S and the target temperature Tr collected experimentally. As shown in Figure 6, it can be seen that there is a negative correlation between the heating rate S and the target temperature Tr, regardless of the target temperature T0.

[0078] Along with calculating the target temperature Tr as described above, the time when heating is completed (completion time) t0 is calculated. The completion time t0 can be estimated by calculation once the target temperature Tr is determined.

[0079] Once the target temperature Tr and end time t0 are calculated, the control unit 40 continues to monitor the detection results of the first and second temperature detection units 17 and 27, and continues heating until it detects that the detected temperature, i.e., the temperature of the first and second structures 13 and 23, has reached the target temperature Tr. When it detects that the temperature of the first and second structures 13 and 23 has reached the target temperature Tr (Yes in step S06), the control unit 40 stops heating the first and second structures 13 and 23 by stopping the power supply to the first and second heating elements 14 and 24 (step S07).

[0080] It is important to note that the estimated temperature of the contents of the retort food PF when the temperatures of the first and second structures 13 and 23 reach the target temperature Tr (point P1 in Figure 5) is lower than the target temperature T0. The target temperature Tr is set higher than the target temperature T0, and can be around 100°C, for example. Therefore, if the temperature of the contents of the retort food PF is heated to above 100°C, which is the boiling point of water, the pouch P may be damaged due to sudden boiling of the contents of the retort food PF.

[0081] However, in this embodiment, when the temperature of the contents of the retort food PF is lower than the target temperature T0, the first and second structures 13 and 23 are heated up to the target temperature Tr, and then the heating by the first and second heating elements 14 and 24 is stopped at a timing that prevents the retort food PF from being overheated. As a result, the retort food PF can be heated without causing an overshoot. In addition, the output of the first and second heating elements 14 and 24 during heating can be set to a large value, making it possible to complete the heating of the retort food PF to the target temperature T0 in a short time.

[0082] When heating of the first and second structures 13 and 23 is stopped in step S07, the heat from the first and second structures 13 and 23, which have been heated to the target temperature Tr, is transferred to the retort food PF that is in contact with the first and second structures 13 and 23. As a result, the first and second structures 13 and 23 and the retort food PF enter a state of thermal equilibrium. When the first and second temperature detection units 17 and 27 detect that the temperature of the first and second structures 13 and 23 has reached the target temperature T0, or that the elapsed time has reached the end time t0 (Yes in step S08), the control unit 40 notifies the user that heating of the retort food PF is complete. Specifically, it displays that the retort food PF has been heated to the target temperature T0 (step S09). Various methods of display are conceivable, but for example, the display unit 51 or lamp 53 may be made to flash, or to light up in a specific color. In addition to the display, sound may also be used.

[0083] After notifying the user that heating is complete, the system can perform several control actions: immediately terminate heating at that point (point P2 in Figure 5), switch to temperature-holding control to continue heating, or terminate heating after performing temperature-holding control for a predetermined time (e.g., a few seconds to tens of seconds). Here, temperature-holding control involves operating the first and second heating elements 14 and 24 so that the temperatures of the first and second structures 13 and 23 maintain the target temperature T0. As a specific control method for such heat retention, a control method (so-called on-off control) can be used in which power is intermittently supplied to the first and second heating elements 14 and 24 at specific timings to cause them to operate intermittently.

[0084] As described above, the heating element control method and heater 1 according to this embodiment enable heating control that takes into account the temperature of the retort food PF by controlling the heating element based on the temperature change of the structure. Furthermore, in the heating element control method according to this embodiment, a long control time with a large amount of heat can be taken in the initial stages of heating, shortening the time required to heat the retort food PF to the target temperature T0. In addition, even when the temperature of the structure reaches a target temperature higher than the target temperature T0, heating is terminated at a timing that prevents the temperature of the contents of the retort food PF from rising above the target temperature T0, i.e., from overshooting. Therefore, the retort food PF can be heated to the target temperature T0 in a short time while avoiding overheating.

[0085] Furthermore, with the heater 1 according to this embodiment, the user can easily and quickly heat the retort food PF to the target temperature accurately by simply inserting the retort food PF to be heated into the installation section 30, operating the temperature setting switch 50 to set the target temperature, and pressing the start switch 43. In addition, heating can be performed without overshooting regardless of the size of the retort food PF, so damage to the pouch P caused by overheating can be substantially eliminated.

[0086] In the embodiment described above, the user only sets the target temperature T0, but if information regarding the weight and contents of the retort food PF could be input, the accuracy of subsequent processes could be improved.

[0087] Furthermore, in the heating element control method according to the embodiment described above, an example was shown in which heating is stopped when the temperature of the first and second structures 13 and 23 reaches the target temperature Tr. However, instead, the control may be immediately switched to maintaining the temperature at the target temperature T0.

[0088] <Second Embodiment> In the first embodiment of the heating element control method described above, the target temperature Tr is calculated using the calculated heating rate S, and heating is stopped when this target temperature Tr is reached. However, this disclosure is not limited to this. Therefore, a second embodiment of the heating element control method, in which the timing of stopping heating is determined by another method, is described below. The heating element control method according to this embodiment can be implemented in the heater 1 described in the first embodiment. Furthermore, in the heating element control method according to this embodiment, steps that are the same as those in the heating element control method according to the first embodiment are denoted by the same reference numerals as those used in the heating element control method according to the first embodiment, and their explanation is omitted. The explanation will focus on steps that differ from the first embodiment.

[0089] The heating element control method according to this embodiment includes at least the steps of: setting a target temperature T0 of the retort food PF (S01); heating at least one of the first and second structures 13, 23 that come into contact with the retort food PF by operating at least one of the first and second heating elements 14, 24 (S02); calculating the temperature change of the first and second structures 13, 23 at a predetermined timing after the start of heating (S04); calculating the end time t0, which is the time it takes for the object to be heated to reach the target temperature T0, from the heating rate, and the heating time tr for carrying out the heating from the temperature change (S05A); detecting whether or not the heating time tr has elapsed (S06A); stopping the heating of the first and second heating elements 14, 24 when the elapsed heating time tr is detected (S07); and notifying that the time to reach the target temperature T0 has elapsed (S09). The following will provide a more detailed explanation, primarily referring to Figures 7 and 8.

[0090] Figure 7 is a flowchart showing an example of a heating element control method according to a second embodiment of this disclosure. Figure 8 is a graph showing an example of the temperature transition when the heating element control method shown in Figure 7 is implemented. In Figure 8, the solid line graph shows the temperature transition of the first and second structures 13 and 23 detected by the first and second temperature detection units 17 and 27 in this embodiment, and the dashed line graph shows the estimated temperature of the contents of the retort food PF at the same point in time.

[0091] When the retort food PF is placed in the installation section 30 and the start switch 43 is pressed, the control unit 40 acquires the target temperature T0 in the same manner as the heating element control method according to the first embodiment (step S01). Next, the control unit 40 operates the first and second heating elements 14 and 24 to perform heating, detects whether the elapsed time from the start of heating has reached a predetermined time t1, and if the elapsed time t1 is detected, calculates the heating rate S corresponding to the temperature change of the first and second structures 13 and 23 (steps S02 to S04).

[0092] Once the heating rate S is calculated, the control unit 40 then calculates the end time t0 and the heating time tr (step S05A). First, the heating time tr corresponds to the time during which heating is continued and can be calculated, for example, by the following equation (2).

number

[0093] Figure 9 is a graph showing an example of the relationship between the heating rate and heating time of a structure when the heating element control method shown in Figure 7 is implemented. In Figure 9, the relationship between the heating rate S and heating time tr for target temperatures T0 = 80°C, 70°C, 60°C, and 50°C is shown by an approximate straight line. This approximate straight line can be derived from values ​​of heating rate S and heating time tr collected experimentally. As shown in Figure 9, it can be seen that there is a negative correlation between the heating rate S and heating time tr, regardless of the target temperature T0.

[0094] Along with calculating the heating time tr as described above, the end time t0 for terminating heating is also calculated. The end time t0 can be estimated by calculation once the heating time tr is determined.

[0095] Once the heating time tr and end time t0 are calculated, the control unit 40 continues heating until it detects that the elapsed time from the start of heating has reached the heating time tr. When it detects that the elapsed time from the start of heating has reached the heating time tr (Yes in step S06A), the control unit 40 stops heating the first and second structures 13 and 23 by stopping the power supply to the first and second heating elements 14 and 24 (step S07).

[0096] When heating of the first and second structures 13 and 23 is stopped, the first and second structures 13 and 23 and the retort food PF enter a state of thermal equilibrium. When the control unit 40 detects that the temperature of the first and second structures 13 and 23 has reached the target temperature T0, or that the elapsed time has reached the end time t0 (Yes in step S08), it notifies the user that heating of the retort food PF is complete. Specifically, it displays that the retort food PF has been heated to the target temperature T0 (step S09).

[0097] As described above, the heating element control method according to this embodiment can also raise the temperature of the structure in a short time while suppressing overheating, and therefore the same effects as the heating element control method according to the first embodiment can be expected.

[0098] <Third Embodiment> For example, in the first embodiment described above, the first and second structures 13 and 23 are temporarily heated to a target temperature Tr that is higher than the target temperature T0, thereby heating the retort food PF to the desired temperature in a short time. On the other hand, if an upper limit temperature Tc is set for the heater 1 due to factors such as the heat resistance of the components of the heater 1, the target temperature Tr may be Tr > Tc. Therefore, below, as a third embodiment of this disclosure, an example of a method for controlling the heating element when an upper limit temperature Tc is set for the heater 1 will be described.

[0099] The heating element control method according to this embodiment can be implemented using the heater 1 described in the first embodiment. Furthermore, for steps in the heating element control method according to this embodiment that are the same as those in the heating element control method according to the first embodiment, the same reference numerals used in the heating element control method according to the first embodiment are used, and their explanations are omitted. The following explanation will focus on steps that differ from those in the first embodiment.

[0100] The heating element control method according to this embodiment includes at least the steps of: setting a target temperature T0 of the retort food PF (S01); heating at least one of the first and second structures 13 and 23 that come into contact with the retort food PF by operating at least one of the first and second heating elements 14 and 24 (S02); detecting the heating rate of the first and second structures 13 and 23 at a predetermined timing after the heating has started (S04); and determining from the heating rate when the retort food PF reaches the target temperature T0. The process includes a step of calculating the time t0 to reach the target temperature (S05B), a step of detecting whether the temperature of the first and second structures 13 and 23 has reached a predetermined upper limit temperature Tc that is higher than the target temperature T0 (S06B), a step of controlling the first and second heating elements 14 and 24 to maintain the upper limit temperature Tc when it is detected that the temperature of the first and second structures 13 and 23 has reached the upper limit temperature Tc (S07B), and a step of notifying that the time to reach the target temperature T0 has elapsed (S09). The process will be explained in more detail below, mainly with reference to Figures 10 and 11.

[0101] Figure 10 is a flowchart showing an example of a method for manufacturing a heating element according to a third embodiment of this disclosure. Figure 11 is a graph showing an example of the temperature transition of a structure when the heating element control method shown in Figure 10 is implemented. In Figure 11, the solid line graph shows the temperature transition of the first and second structures 13 and 23 detected by the first and second temperature detection units 17 and 27 in this embodiment, and the dashed line graph shows the estimated temperature of the contents of the retort food PF at the same point in time.

[0102] When the retort food PF is placed in the installation section 30 and the start switch 43 is pressed, the control unit 40 acquires the target temperature T0 in the same manner as the heating element control method according to the first embodiment (step S01). Next, the control unit 40 operates the first and second heating elements 14 and 24 to perform heating, detects whether the elapsed time from the start of heating has reached a predetermined time t1, and if the elapsed time t1 is detected, calculates the heating rate S corresponding to the temperature change of the first and second structures 13 and 23 (steps S02 to S04).

[0103] Once the heating rate S is calculated, the control unit 40 then calculates the termination time t0 for ending the heating (step S05B). The termination time t0 can be calculated, for example, by predicting the time required for the first and second structures 13 and 23 to reach the upper limit temperature Tc, and the time from when the first and second structures 13 and 23 reach the upper limit temperature Tc until the retort food PF reaches the target temperature T0, based on the performance of the first and second heating elements 14 and 24 and the heat capacity of the first and second structures 13 and 23.

[0104] Once the end time t0 is calculated, the control unit 40 continues to monitor the detection results of the first and second temperature detection units 17 and 27, and continues heating until it detects that the detected temperature, i.e., the temperature of the first and second structures 13 and 23, has reached the upper limit temperature Tc. When it detects that the temperature of the first and second structures 13 and 23 has reached the upper limit temperature Tc (Yes in step S06B), the control unit 40 starts temperature holding control, which controls the first and second heating elements 14 and 15 so that the temperature of the first and second structures 13 and 23 is maintained at the upper limit temperature Tc (step S07B). Details of the temperature holding control are as described above. Furthermore, the temperature holding control continues from the time the temperature of the first and second structures 13 and 23 reaches the upper limit temperature Tc (time t2) until the retort food PF reaches the target temperature T0.

[0105] Due to the temperature-holding control described above, the retort food PF is continuously heated. When the elapsed time reaches the end time t0 (Yes in step S08B), the control unit 40 notifies the user that the heating of the retort food PF is complete. Specifically, it displays that the retort food PF has been heated to the target temperature T0 (step S09).

[0106] As described above, the heating element control method according to this embodiment can also raise the temperature of the object to be heated in a short time while suppressing overheating, so the same effects as the heating element control method according to the first embodiment can be expected. In addition, when heating the retort food PF, heating is not performed above the upper limit temperature Tc of the heater 1, so damage to the heater 1 can be avoided.

[0107] <Fourth Embodiment> In the first to third embodiments described above, the temperature change of the first and second structures 13 and 23 is determined by calculating the heating rate S after a predetermined time t1 has elapsed since the start of heating, but the present disclosure is not limited thereto.Therefore, as a fourth embodiment of the present disclosure, an example of a heating element control method in which the temperature change of the first and second structures 13 and 23 is calculated in a different way will be described below.

[0108] The heating element control method according to this embodiment can be implemented using the heater 1 described in the first embodiment. Furthermore, many steps in the heating element control method according to this embodiment can be the same as those in the third embodiment. Therefore, for steps in the heating element control method according to this embodiment that are the same as those in the heating element control method according to the third embodiment, the same reference numerals used in the heating element control method according to the third embodiment will be used, and their explanations will be omitted. The following explanation will focus on steps that differ from those in the third embodiment.

[0109] The heating element control method according to this embodiment includes at least the steps of: setting a target temperature T0 of the retort food PF (S01); heating at least one of the first and second structures 13 and 23 that come into contact with the retort food PF by operating at least one of the first and second heating elements 14 and 24 (S02); stopping the heating at a predetermined timing after the heating has started (S04C1); detecting the temperature change ΔT of the first and second structures 13 and 23 after the heating has stopped (S04C2); and calculating the time t0 for the retort food PF to reach the target temperature T0 from the temperature change ΔT. The process includes a step (S05C1), a step (S05C2) to operate the first and second heating elements 14 and 24 to restart the heating of the first and second structures 13 and 23, a step (S06B) to detect whether the temperature of the first and second structures 13 and 23 has reached a predetermined upper limit temperature Tc that is higher than the target temperature T0, a step (S07B) to control the first and second heating elements 14 and 24 to maintain the upper limit temperature Tc when it is detected that the temperature of the first and second structures 13 and 23 has reached the upper limit temperature Tc, and a step (S09) to notify that the time to reach the target temperature T0 has elapsed. The process will be explained in more detail below, mainly with reference to Figures 12 and 13.

[0110] Figure 12 is a flowchart showing an example of a method for manufacturing a heating element according to the fourth embodiment of this disclosure. Figure 13 is a graph showing an example of the temperature transition of a structure when the heating element control method shown in Figure 12 is implemented. In Figure 13, the solid line graph shows the temperature transition of the first and second structures 13 and 23 detected by the first and second temperature detection units 17 and 27 in this embodiment, while the dashed line graph shows the estimated temperature of the contents of the retort food PF at the same point in time.

[0111] When the retort food PF is placed in the installation section 30 and the start switch 43 is pressed, the control unit 40 acquires the target temperature T0 (step S01). Next, the control unit 40 operates the first and second heating elements 14 and 24 to start heating (step S02), and detects whether the elapsed time from the start of heating has reached a predetermined time t1 (step S03).

[0112] When a predetermined time t1 is detected to have elapsed (Yes in step S03), the control unit 40 stops the first and second heating elements 14 and 24 and temporarily stops the heating of the first and second structures 13 and 23 and the retort food PF (step S04C1).

[0113] When the first and second heating elements 14 and 24 stop, the temperatures of the first and second structures 13 and 23 and the retort food PF decrease. The control unit 40 then detects the temperature change of the first and second structures 13 and 23 that decreases as heating stops (step S04C2). The temperature change can be determined by calculating an approximate formula from the temperature detected multiple times at predetermined intervals, similar to how the heating rate S is calculated. Then, from the detected temperature change ΔT, the time (completion time) t0 until the retort food PF reaches the target temperature T0 is calculated (step S05C1).

[0114] At the time the end time t0 is calculated (time t3), the control unit 40 restarts the first and second heating elements 14 and 24 to resume heating of the first and second structures 13 and 23 and the retort food PF (step S05C2). After resuming heating, the control unit 40 continues to monitor the detection results of the first and second temperature detection units 17 and 27 and continues heating until it detects that the detected temperature, i.e., the temperature of the first and second structures 13 and 23, has reached the upper limit temperature Tc. When it detects that the temperature of the first and second structures 13 and 23 has reached the upper limit temperature Tc (Yes in step S06B), the control unit 40 starts temperature holding control, which controls the first and second heating elements 14 and 15 so that the temperature of the first and second structures 13 and 23 is maintained at the upper limit temperature Tc (step S07B). Furthermore, temperature control is maintained from the point when the temperature of the first and second structures 13 and 23 reaches the upper limit temperature Tc (time t2) until the retort food PF reaches the target temperature T0.

[0115] Due to the temperature-holding control described above, the retort food PF is continuously heated. When the elapsed time reaches the end time t0 (Yes in step S08B), the control unit 40 notifies the user that the heating of the retort food PF is complete. Specifically, it displays that the retort food PF has been heated to the target temperature T0 (step S09).

[0116] As described above, the heating element control method according to this embodiment can also raise the temperature of the object to be heated in a short time while suppressing overheating, so the same effects as the heating element control method according to the first embodiment can be expected. In addition, since the temperature change of the structure is calculated with the heating element stopped, the influence of noise can be suppressed, and the accuracy of calculating the time t0 to reach the target temperature T0 can be improved.

[0117] <Variation> The end time t0 calculated in each of the embodiments described above can also be calculated by applying a virtual heat circuit to the heater 1 and utilizing that heat circuit. Below, a method for calculating the end time t0 using a heat circuit will be described as a modified example of each of the embodiments described above.

[0118] Figure 14 is a schematic diagram showing a virtual heat circuit applied to the heater shown in Figure 1. Figure 15 is an enlarged view of section E in Figure 14. The heater 1 described above can be represented by a virtual heat circuit, as shown in Figures 14 and 15. Here, i0 is the heater output (i.e., heat flow rate) (W), C1 is the heat capacity (J / K) of the part of the first heating section 12 that is outside the first heating element 14, C2 is the heat capacity (J / K) of the part of the first heating section 12 that is inside the first heating element 14 (i.e., the retort food PF side), C3 is the heat capacity of the retort food PF (J / K), R1 is the thermal resistance (K / W) from the first heating element 14 to the first cover member 15 side, R2 is the thermal resistance (K / W) from the first heating element 14 to the first structure 13, R3 is the thermal resistance (K / W) of the retort food PF, and V1 is the first V2 is the average temperature (°C) on the outside of the structure 13 (i.e., the side opposite to the retort food PF), V3 is the average temperature (°C) on the inside of the first structure 13, i1 is the heat flow (W) flowing to the outside of the first structure 13, i2 is the heat flow (W) flowing to the inside of the first structure 13, i3 is the heat flow (W) flowing into the retort food PF, q1 is the amount of heat (J) accumulated on the outside of the first structure 13, q2 is the amount of heat (J) accumulated inside the first structure, and q3 is the amount of heat (J) accumulated in the retort food PF.

[0119] The thermal circuit shown in Figure 14 has a symmetrical structure centered on the retort food PF. Therefore, in the following, we will focus on the left half of the thermal circuit (part E in Figure 14) of the total thermal circuit shown in Figure 15 and detect the temperature of each part. In this case, the heat capacity (J / K) of the retort food PF, indicated by C3, will be half its value.

[0120] From the thermal circuit shown in Figure 14, we can obtain equation (3) below using Kirchhoff's laws.

number

[0121] From equation (3) above, the temperatures V2(t) and V3(t) of the first structure 13 and the retort food PF at a certain time t can be expressed by the following equation (4).

number

[0122] Here, the coefficients a, b, c, λ1, λ2, A, and B can each be expressed by the following equation (5).

number

[0123] The device constants can be determined as follows. In detail, first measure V2 under different conditions and find the device constants that best match equation (6) below. Here, the constants c3 and R3 for the retort food PF are currently unknown. On the other hand, if the retort food PF is not set in the installation section 30, it can be assumed that c3 is sufficiently small and R3 is sufficiently large. For example, set c3=1 and R3=1000. The unknowns are the four device constants c1, c2, R1, and R2, so measure the four conditions and solve the simultaneous equations to find the device constants.

number

[0124] Next, the temperature V2 of the first structure 13 is measured. Specifically, for example, four or more time points are measured. Then, the values ​​are identified by fitting. Through this process, the device constants can be determined. The least squares method can also be used for fitting. Furthermore, measurements can be taken while varying the initial temperatures V1(0) and V2(0).

[0125] On the other hand, when heating the object to be heated, the constants c3 and R3 of the unknown object to be heated (e.g., retort food PF) are calculated when the temperature of structures 13 and 14 rises. Specifically, the calculation is performed using equation (6) described above.

[0126] Let's consider an example of the control process shown in Figure 11. First, when the heating elements 14 and 24 are activated, the temperature V2 of the structures 13 and 23 rises. Since there are two unknowns at this time, identification is performed by fitting using the least squares method or similar from any two or more points. For example, the constants c3 and R3 are calculated by obtaining the temperatures V2(t1) and V2(t2) at two different times within a predetermined detection time. Next, using the obtained c3 and R3, the end time t0 at which the temperature V3 of the object being heated reaches the desired temperature is determined by equation (7) below. Here, an approximate solution can also be obtained for the calculation of the end time t0 using, for example, the Newton-Raphson method.

number

[0127] In the modified example described above, we illustrated a method for identifying c3 and R3 during the heating of the object to be heated (e.g., retort food PF) and obtaining the heating time (specifically, the end time t0). However, if c3 and R3 can be estimated, for example, if the volume and type of the object to be heated can be identified, the end time t0 can also be determined by programming a simple relationship from equations (6) and (7) described above.

[0128] If the heat capacity and thermal resistance of the object to be heated are known, c3 and R3 can also be calculated theoretically. The heat capacity C and thermal resistance Rth can be determined by the following equation (8).

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[0129] Alternatively, a data sheet like the one shown in Figure 6 can be created in advance through experiments, and the completion time t0 can be estimated by comparing the calculated heating rate or temperature change with the data sheet. Furthermore, the data shown in Figure 6 can be stored in the form of a calculation formula (similar to equation (2) above), and the completion time can be calculated from the heating rate or temperature change using this formula.

[0130] This disclosure is not limited to the embodiments described above, and can be implemented with various modifications without departing from the spirit of this disclosure. All such modifications are included in the technical concept of this disclosure. [Explanation of Symbols]

[0131] 1 Heater 13. The first structure (an example of a structure) 14. The first heating element (an example of a heating element) 17. First temperature detection unit (an example of a temperature detection unit) 23. Second Structure (An Example of a Structure) 24. Second heating element (an example of a heating element) 27. Second temperature detection unit (an example of a temperature detection unit) 30 Installation part 40 Control Unit PF retort foods (an example of items to be heated) P Pouch

Claims

1. A step of setting the target temperature of the object to be heated, A step of heating the structure that comes into contact with the object to be heated by operating a heating element, A step of detecting the rate of heating or temperature change of the structure at a predetermined timing after the start of heating, A step of calculating the time it takes for the object to be heated to reach the target temperature from the heating rate or temperature change, The process includes a step of notifying that the time required to reach the target temperature has elapsed, The step of calculating the time it takes for the object to be heated to reach the target temperature from the heating rate or temperature change is as follows: A step of applying a virtual thermal circuit consisting of the heating element, the structure, and the thermal resistance and heat capacity corresponding to the object to be heated, The thermal resistance and heat capacity corresponding to the heating element and the structure are assumed to be known, and the thermal resistance and heat capacity corresponding to the object to be heated are assumed to be unknown. The process involves determining the thermal resistance and heat capacity of the object to be heated, which are the unknowns, from the detected temperature change data. The process includes a step of calculating the heating time required for the object to be heated to reach the target temperature, using the thermal resistance and heat capacity of the object to be heated as determined above. A method for controlling a heating element.

2. Before the step of notifying that the time to reach the target temperature has elapsed, A step of detecting whether the temperature of the structure has reached a predetermined upper limit temperature that is higher than the target temperature, The system further includes a step of controlling the heating element to maintain the upper limit temperature when it is detected that the temperature of the structure has reached the upper limit temperature. A method for controlling a heating element according to claim 1.

3. A step of setting the target temperature of the object to be heated, A step of heating the structure that comes into contact with the object to be heated by operating a heating element, A step of detecting the rate of heating of the structure at a predetermined timing after the start of heating, A step of calculating the temperature to be reached of the structure, which is higher than the target temperature, and the time it takes for the object to be heated to reach the target temperature, based on the heating rate. A step of detecting whether the temperature of the structure has reached the target temperature, The process of stopping the heating of the heating element when it is detected that the temperature of the structure has reached the target temperature, The process includes a step of notifying that the time required to reach the target temperature has elapsed. A method for controlling a heating element.

4. The predetermined timing is the timing when the rate of change of the heating rate per unit time becomes 3% or less, the timing when a predetermined elapsed time from the start of heating has elapsed, or the timing when the structure reaches a predetermined temperature. A method for controlling a heating element according to claim 3.

5. The object to be heated contains a liquid, and the heating element is controlled to raise the temperature of the liquid to the target temperature. A method for controlling a heating element according to claim 3.

6. The step of calculating the time it takes for the object to be heated to reach the target temperature from the heating rate involves applying a virtual thermal circuit to the heater including the heating element, and using the detected heating rate to calculate the time it takes for the object to be heated to reach the target temperature using the thermal circuit. A method for controlling a heating element according to claim 3.

7. The installation section where the object to be heated is placed, A structure that comes into contact with the object to be heated and is installed in the aforementioned installation section, A heating element for heating the aforementioned structure, A temperature detection unit for detecting the temperature of the aforementioned structure, The system includes a control unit that performs each step of the heating element control method according to any one of claims 1 to 6 based on the detection result of the temperature detection unit, Heater.

8. The mounting portion is provided between a pair of structures that are facing each other at a predetermined distance apart, and the heating element is provided on at least one of the pair of structures. The heater according to claim 7.

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