fryer

Abstract

To provide a fryer capable of detecting, at an early stage, a decrease in level and abnormal heating of fry oil of various forms.SOLUTION: A fryer 1 includes: a tank plate temperature sensor 45 (high limit HL) that detects a temperature of a tank plate 13 of an oil tank 10; and a controller 63 that controls oil tank heating means 20. The controller 63 stops heating and / or issues an alarm in consideration of a relationship between an elapsed time after start of heating and a detection temperature of the tank plate temperature sensor 45.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fryer for deep-frying various foods, which is used in fast food restaurants, convenience stores, pubs, restaurants, etc. In particular, the present invention relates to a fryer with enhanced user-oriented safety functions that can detect various types of frying oil level drops, empty cooking, and abnormal heating at an early stage, and prevent smoke and fire at an early stage. [Background technology]

[0002] JP 2016-67661 A discloses a technology to detect the so-called "dry-heating state" in which heating continues when there is no cooking oil in the oil vat. It states that "a temperature sensor for detecting dry-heating is provided which constantly monitors the temperature of the oil vat, and when the detected temperature exceeds a threshold value (300°C), it is determined that the oil vat is in a dry-heating state." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2016-67661 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0004] The technology of Patent Document 1 above was significant as a technology for preventing a fryer from heating without food. The present invention aims to provide a fryer with enhanced user-oriented safety functions that can detect various types of frying oil level drops, heating without food, and abnormal heating at an early stage and prevent smoke and fire at an early stage. [Means for solving the problem]

[0005] In this "Summary" and "Claims," ​​reference signs to various parts in the attached drawings are shown in parentheses, but this is for reference only and is not intended to limit the scope of the rights to those in the attached drawings.

[0006] A fryer (1) according to a first aspect of the present invention is a fryer (1) comprising an oil vat (10) for storing frying oil, a heating means (20) for heating the oil vat, a vat plate temperature sensor (45, high limit HL) for detecting the temperature of a vat plate (13) of the oil vat (10), and a controller (63) for controlling the heating means (20), wherein the controller (63) stops heating and / or issues an alarm in consideration of the relationship between the elapsed time after the start of heating and the temperature detected by the vat plate temperature sensor (45). For example, if the HL temperature exceeds a predetermined temperature T2 (eg, 100° C.) before a predetermined time (eg, 140 seconds or 180 seconds) has elapsed after the start of heating, it can be determined that an abnormality has occurred.

[0007] According to the first aspect of the present invention, the relationship between the oil level in the oil vat and the rise in the HL temperature is taken into consideration, and if the HL temperature reaches (exceeds) a predetermined temperature (e.g., 100°C) within a predetermined time (e.g., 140 seconds or 180 seconds) from the start of heating, it is determined that the oil level is abnormally low, and measures such as stopping heating (turning off the inverter of the IH coil) or emitting an alarm (sound / light) are taken. Note that the reason why it is difficult to determine an oil level abnormality using the oil temperature sensor (41, OS) that detects the temperature of the frying oil in the oil vat (10) is that when the oil level drops and the OS is exposed to the air, the temperature of the OS does not rise but rather falls.

[0008] According to this first aspect, an abnormally low oil level in the oil tank (10) can be detected early and heating can be stopped early. According to the technology of the above-mentioned Patent Document 1, the relationship between the time after heating starts and the high limit temperature is not taken into consideration, and heating is stopped simply by detecting when the high limit temperature reaches a certain threshold temperature (300°C in the example of Patent Document 1). In this case, the abnormality is detected later than the above-mentioned 180 seconds. Note that even if the threshold temperature is lowered, 220°C is the limit. This is because the cooking temperature for deep-frying seafood, green vegetables, and other watery ingredients is 200°C (high temperature), and if a temperature close to this is used as the threshold temperature, there is a risk of an alarm being erroneously activated during high-temperature cooking.

[0009] In the first embodiment of the present invention, it is possible to check whether the HL temperature at the start of heating is room temperature (T1, for example, 50° C. or lower), and to make the abnormality judgment of claim 2 only if it is room temperature.

[0010] If reheating is started before the oil cools down after it has been heated once, the HL temperature may reach the specified temperature T2 within a certain time after heating starts, even if the oil level is normal. In such a case, there is no need to judge it as abnormal, and measures such as stopping the heating in an emergency would interfere with the cooking process. Therefore, the judgment of the first mode is limited to cases where the oil temperature has dropped sufficiently when heating starts.

[0011] A fryer (1) according to a second aspect of the present invention is a fryer (1) comprising: an oil vat (10) for storing frying oil; a heating means (20) for heating the oil vat; an oil temperature sensor (41, OS) for detecting the temperature of the frying oil in the oil vat (10); a vat plate temperature sensor (45, HL) for detecting the temperature of a vat plate (13) of the oil vat (10); and a controller (63) for receiving signals of the temperatures detected by the oil temperature sensor (41) and the vat plate temperature sensor (45) and for controlling the heating means (20), The oil temperature sensor (41) is provided so as to protrude into the oil vat, and is located below the appropriate frying oil level in the oil vat and above the vat plate temperature sensor (45); The controller (63) stops heating and / or issues an alarm, taking into consideration the difference between the temperature (TOS) detected by the oil temperature sensor (41) and the temperature (THL) detected by the tank plate temperature sensor (45).

[0012] The operation of the oil level abnormality detection of the fryer of this second embodiment will be described in detail later with reference to the drawings (paragraphs 0050-0057). Note that the judgment using this temperature difference may be made only when the HL temperature at the start of heating exceeds room temperature (T1, for example, 50°C or lower), or the judgment considering the temperature difference may be made even when the start temperature is room temperature.

[0013] In the present invention, the tank plate temperature sensor (45, HL) is in contact with the tank plate to detect its temperature, and is preferably disposed at a level lower than the oil temperature sensor (41, OS) and not lower than the heating means (20).

[0014] In the second embodiment of the present invention, The controller (63) can determine that an abnormality has occurred when THL-TOS≧ΔT1 (e.g., 41° C., 55° C.) and stop heating and / or issue an alarm. In the embodiment (FIG. 5) described later, even when THL-TOS≦ΔT1, the abnormality is determined as "there is a risk that the temperature sensor may be broken or that installation may not be necessary," and such a specific method is also preferable.

[0015] When the oil level is at the normal level, after heating starts and when the temperature rises, THL>TOS. This is because the pan plate receives heat from the heating means and has good thermal conductivity, so its temperature rises easily. In contrast, the OS is immersed in frying oil that is rising from room temperature (generally), and the rise in temperature of the oil is brought about by the Joule heat of the pan plate being transferred to the frying oil. Therefore, there is a time lag in the rise in temperature of the frying oil, or conversely, the pan plate temperature rises first.

[0016] However, the oil level is abnormal low Due to this (mostly due to insufficient oil at the start of heating), if the frying oil level is below the OS and it is exposed to the air above the oil surface, the OS temperature will be lower than the oil temperature. Meanwhile, the coil output remains full in an attempt to raise the oil temperature, so the HL temperature continues to rise. Therefore, when THL-TOS≧ΔT1 (e.g. 55°C), it is considered that the OS is exposed to the air, and the oil level is determined to be abnormal. It is also preferable to perform the oil level abnormality detection by combining the first and second aspects.

[0017] The third aspect of the present invention is a fryer (1) having the same components as the second aspect of the fryer, The oil temperature sensor (41) is provided so as to protrude into the oil tank, and is located below the appropriate frying oil level of the oil tank and above the tank plate temperature sensor (45). Furthermore, when the controller (63) determines that it is abnormal when THL - TOS ≥ ΔT2 (for example, 30°C) after TOS reaches the set temperature, the controller stops heating and / or issues an alarm. Here, TOS is the detected temperature of the oil temperature sensor (41, OS), and THL is the detected temperature of the tank plate temperature sensor (45, HL).

[0018] After TOS reaches the set temperature, TOS is higher in temperature than THL (temperature difference, for example, 10 - 30°C). This is because heating temporarily stops when the temperature rise is completed (= the set temperature is reached), and then ON - OFF control of the coil current is started to maintain the oil temperature (temperature control). Since the reference for temperature control is the OS temperature, the temperature of HL, which is located lower than OS, becomes THL < TOS due to the influence of oil convection. (For a detailed example explanation, see paragraphs 0059 and 0054).

[0019] Specifically, as will be described later (paragraphs 0060 - 0065), when an oil leak occurs and the oil level drops below the oil temperature sensor (41), the oil temperature sensor (41) becomes exposed and touches the air, resulting in a temperature drop. On the other hand, the tank plate temperature sensor (45, high limit) has the characteristic of increasing in temperature when the oil level drops. From the temperature characteristics of the oil temperature sensor and the high limit during the above - mentioned oil leak, when an oil leak occurs, the temperature change trend of the oil temperature sensor and the high limit tends to reverse. That is, when the reversal range of the temperature change of the oil temperature sensor and the high limit detects a predetermined value ΔT2 (for example, 30°C), it is determined that an oil leak has occurred, and heating is stopped.

[0020] The fryer (1) according to the fourth aspect of the present invention is a fryer (1) including an oil tank (10) for storing frying oil, an IH coil (20) for heating the oil tank, and a tank plate temperature sensor (45, high limit, HL) for detecting the temperature of the tank plate (13) of the oil tank (10). The tank plate temperature sensor (45, HL) is in contact with the tank plate to detect its temperature, and is characterized in that it detects a temperature at a level not lower than that of the IH coil (20), is not adversely affected by electromagnetic waves from the coil, and is located in close proximity to the coil.

[0021] In order to fully utilize the above-mentioned safety function of the present invention, it is preferable to devise the position and installation form of the tank plate temperature sensor (high limit). That is, the position of the high limit in this embodiment is a position that is not affected by electromagnetic waves from the heating coil, is close enough to the coil heating surface, and can quickly detect thermal changes due to heating. In addition, a preferred form of the high limit temperature sensor is a form in which a fulcrum such as a stud is welded to the back surface of the oil tank near the gap between the heating coil and the coil base, and a thermocouple with a round terminal is installed at that location.

[0022] Note that while this method of detecting abnormal overheating has been explained using a fryer as a specific example, it can also be applied to electric fryers whose heat source is a sheath heater, and noodle boiling machines that cook different types of food. Effect of the Invention

[0023] Compared to the conventional method of determining that the oil level is abnormally low when the THL exceeds a threshold, this method can detect various types of low frying oil levels, empty cooking, and abnormal heating at an early stage, making it possible to provide fryers with enhanced user-driven safety functions that can prevent smoke and fire at an early stage. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional side view showing an overall configuration of a fryer 1 according to an embodiment of the present invention. [Diagram 2] Fig. 2(A) is a front cross-sectional view of the fryer 1 in Fig. 1. Fig. 2(B) is a plan view of the fryer 1 in Fig. 1. [Diagram 3] FIG. 2 is a block diagram showing the configuration of a power supply system and a control system of the fryer according to the embodiment of the present invention. [Figure 4] FIG. 2 is a side cross-sectional view showing different oil levels in the fryer 1 of FIG. 1. (A) shows the normal level, (B) shows the OS exposed to air, (C) shows the HL exposed to air, and (D) shows the empty state. [Diagram 5] 5 is a flowchart showing the overall operation of an oil level abnormality determination program. [Figure 6] 1 is a graph plotting the relationship between the elapsed time after the start of heating and the temperature detected by the high limit temperature sensor, with the oil level in the oil vat 10 being changed. The vertical axis represents temperature, and the horizontal axis represents elapsed time. [Figure 7] 1 is a graph showing an example of the transition of temperatures detected by the oil temperature sensor (OS) and the high limit temperature sensor (HL) after the start of heating when the frying oil is at a normal level and the oil temperature at the start of heating is room temperature. The vertical axis is temperature and the horizontal axis is elapsed time. [Figure 8] 1 is a graph showing an example of the transition of the temperature (TOS) detected by the oil temperature sensor (OS) and the temperature (THL) detected by the high limit temperature sensor (HL) when frying oil is leaking from the normal level while the set oil temperature is being maintained. The vertical axis is temperature, and the horizontal axis is elapsed time. [Figure 9] This is a graph showing how the temperature detected by the HL sensor is affected by electromagnetic induction of the coil when the HL sensor is installed near an IH coil. The vertical axis is temperature, and the horizontal axis is elapsed time. [Explanation of symbols]

[0025] 1; flyer, 2; main frame 10; Oil tank, 10a; Upper half 10a, 10b; Middle lower part, 10c; Lower part, 10x; Bottom bottom surface 11; side wall, 11F; front panel, 11B; rear panel, 11R·11L; left and right panel 13; Slanted bottom (tank plate), 14; waste collection section, 14b; bottom wall, 14d; side wall (side surface), 19; oil drain port, 19a; oil drain pipe, 19b; opening and closing valve 20; IH coil (heating means), 22; coil base 41;OS (oil temperature sensor), 45;HL (tank plate temperature sensor) 61; remote control, 63; controller, 65; switch, 67; inverter DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. In each drawing, the directions "up" and "down" indicated by the arrows are directions along the earth's gravity. "Front" is the side where the chef stands and puts ingredients into the oil vat 10 or scoops them up. "Back" is the opposite, farther direction as seen from the chef. "Left" and "right" are the left and right directions as seen by the chef facing the fryer 1.

[0027] First, the overall structure of a fryer according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a schematic side cross-sectional view showing the overall structure of a fryer 1 according to an embodiment of the present invention. Figure 2(A) is a front cross-sectional view of the fryer 1 of Figure 1. Figure 2(B) is a plan view of the fryer 1 of Figure 1. The fryer 1 has an oil tank 10 for storing oil for frying food, and an electromagnetic induction coil 20 for heating the oil tank 10. These are housed in a main body frame 2.

[0028] The main body frame 2 is a rectangular parallelepiped box that is long from front to back. The main body frame 2 rests on a stand or legs (not shown), and the height of the top surface of the oil vat 10 is, for example, 800 mm. An operation panel (remote control 61, see Figure 3) is attached to the front of the main body frame 2.

[0029] The oil vat 10 consists of an upper half 10a, a lower middle section 10b in the vertical center, and a lower section 10c (residue collection section 14). The upper half 10a of the oil vat extends over most of the upper surface of the main body frame 2. The front side of the side wall 11 of the upper half 10a of the oil vat is formed by an upright front plate 11F. The rear side of the upper half 10a of the oil vat is formed by an upright rear plate 11B. The left and right sides of the upper half 10a of the oil vat are formed by upright left and right side plates 11R and 11L as shown in Figure 2(A).

[0030] The lower middle section 10b of the oil vat 10 is a quadrangular pyramid shape formed by an inclined bottom plate 13 (the inclination angle θ is, for example, 15 to 25°) that is inclined toward the lower center. A coil base 22 around which an IH coil 20 is wound is attached to the lower surface of the inclined bottom plate 13.

[0031] The lower part 10c of the oil vat 10 is a rectangular solid waste collection section 14. The waste collection section 14 is a section for collecting fried food waste and other food waste. The waste collection section 14 has a nearly vertical side wall 14d that is formed continuously from the lower end of the inclined bottom plate 13 and extends downward, and a bottom wall 14b. The bottom wall 14b is slightly inclined, and an opening 19 for draining oil is formed at its lowest part. An oil drain pipe 19a is connected below the opening 19, and an opening / closing valve 19b is attached to the pipe.

[0032] The upper half side walls 11 and the inclined bottom plate 13 of the oil tank 10 are made of a magnetic material. Examples of the magnetic material that can be used include ferritic stainless steel (such as SUS430) and non-magnetic materials coated with a magnetic material. On the other hand, the side walls and bottom wall of the waste storage section 14 (lower part 10c) are made of a non-magnetic material. Examples of the non-magnetic material that can be used include austenitic stainless steel (SUS304, 316, etc.).

[0033] The IH coil 20 is wound around the periphery of the waste storage section 14 on the lower surface of the inclined bottom plate 13 so as to make a number of turns. 10x The coil 20 is fixed to the coil base 22.

[0034] The coil 20 is made of copper stranded wire (one example), and both ends of the coil 20 are connected to an inverter 67 (see also FIG. 3) via conductors. When a current flows through the coil 20, magnetic lines of force are generated. When these magnetic lines of force pass through the inclined bottom plate 13, eddy currents are generated. These eddy currents are converted into heat by electrical resistance and heat the bottom plate (induction heating). The oil above the heated inclined bottom plate 13 is heated and flows upward around the periphery of the oil vat 10. It then flows toward the inside where the temperature is lower, and sinks downward. In other words, convection occurs from the periphery of the oil vat 10 to the center, then flows downward near the center, and then flows back toward the periphery. Such convection occurs on all four sides of the oil vat 10, heating the oil in the vat (the heated area is called the hot zone).

[0035] On the other hand, the scum storage section 14 at the bottom center of the oil vat 10 is made of a non-magnetic material, and induction heating by the magnetic flux generated by the coil 20 does not occur. Furthermore, the above-mentioned convection hardly occurs in the scum storage section 14, which is separated at the bottom of the oil vat 10, and the scum storage section 14 forms a cool zone. For example, when the temperature of the oil in the hot zone H is 180°, the temperature of the oil in the cool zone C is about 80 to 100°.

[0036] The oil temperature control temperature sensor 41 (abbreviated as "OS" and its detected temperature is called TOS) detects the temperature of the frying oil stored in the oil vat 10, and the temperature signal is used for controlling the oil temperature. The OS 41 is located at the bottom of the upper half 10a. As shown in Figs. 1 and 2, the OS is a thermocouple housed inside a thin sheath (closed-end cylinder). The sheath of the OS penetrates the side wall 11 of the oil vat 10, and its tip protrudes about 12 mm into the oil vat 10. The height position of the OS is 125 mm from the top surface of the oil vat 10, 40 mm below the normal oil level, and about 15 mm above the top end of the inclined bottom surface 13. Note that these values ​​are for an example of a tabletop fryer with a frying oil capacity of 8 liters and an IH coil 20 capacity of 3 kW.

[0037] The abnormality detection temperature sensor 45 (high limit, abbreviated as "HL" and its temperature is referred to as "THL") is used to detect an abnormal rise in temperature of the oil vat 10 and stop heating or issue an alarm. The HL45 is a thermocouple with a round terminal, and is attached so as to be in close contact with the bottom surface of the upper part of the inclined bottom surface 13 of the oil vat 10.

[0038] In the present invention, the HL temperature alarm is performed in three embodiments described below, and in order to obtain better effects from these embodiments, it is important to select (determine) the position of the high limit temperature sensor. This will be described in detail later (paragraphs 0074-0078), but here, various states of the frying oil level will be described with reference to FIG. 4.

[0039] Figure 4 is a side cross-sectional view showing different oil levels in the fryer 1 of Figure 1. (A) shows the normal level, (B) shows the state where the OS is exposed to the air, (C) shows the state where the HL is exposed to the air, and (D) shows the empty state. This figure is a schematic diagram showing the state where the oil level drops in the order of (A) ⇒ (B) ⇒ (C) ⇒ (D) as oil leaks from the oil drain pipe 19a of the fryer 1.

[0040] First embodiment Figure 6 is a graph plotting the relationship between the elapsed time after heating started and the temperature detected by the high limit temperature sensor while changing the oil level in the oil tank 10. The vertical axis is temperature, and the horizontal axis is elapsed time (seconds). The experiment that collected this temperature data was conducted in a fryer with a frying oil capacity of 8 liters and an IH coil capacity of 3 kW.

[0041] In the figure, the thin two-dot chain line at the bottom indicates the transition of the temperature detected by the thermometer (OS, 41) for controlling the oil temperature when the oil level is normal. The second thick solid line from the bottom indicates the change in the temperature detected by the high limit temperature sensor (HL, 45) when the oil level in the oil tank is normal. The third thin solid line from the bottom (fourth from the top) indicates the case where the oil level in the oil tank is 60 mm lower than normal. 4 shows the transition of the detected temperature of the high limit temperature sensor (HL, 45) in the above. The fourth thick dashed line from the bottom (third from the top) indicates the case where the oil level in the oil tank is 70 mm lower than normal. 4 shows the transition of the detected temperature of the high limit temperature sensor (HL, 45) in the above. The second thin dashed line from the top shows the high-level oil level when the oil tank is 90 mm lower than normal. The graph shows the change in temperature detected by the mitt temperature sensor (HL, 45). The top dashed dotted line indicates the transition of the temperature detected by the high limit temperature sensor (HL, 45) when the oil tank is empty of oil.

[0042] As shown by the thin two-dot chain line at the bottom of the figure, the OS temperature (oil temperature) when the oil level is at the normal level gradually rises and reaches approximately 35°C after 180 seconds. As shown in Figure 7, it takes approximately 20 minutes for this oil temperature to reach the set cooking temperature, for example 175°C, in the fryer used in this experiment. Note that up to an oil level of approximately -35mm, it is within the "normal level range" (the range of frying oil consumption during normal cooking).

[0043] The HL temperature of "normal oil level", the second thick solid line from the bottom, gradually rises from room temperature (about 20°C) when heating starts, to over 50°C after 50 seconds, to about 75°C after 120 seconds, and to about 80°C after 180 seconds.

[0044] The HL temperature (oil level -60mm) indicated by the third thin solid line from the bottom above the normal level HL temperature (thick solid line) is almost the same as the normal level (thick solid line) for about 30 seconds from the start of heating. After that, the thin solid line (oil level -60mm) is higher than the thick solid line (normal level). Generally, the smaller the amount of frying oil, the smaller the heat capacity of the oil, and the easier it is for the oil temperature and the temperature of the walls of the oil tank 10 to rise.

[0045] The HL temperature indicated by the fourth thick dashed line (oil level -70 mm) is the same as the thin solid line (oil level -60 mm). HL is higher than the oil level indicated by the second thin dashed line from the top (oil level -90mm). The HL temperature is even higher. The HL temperature indicated by the top dashed line (empty oil) is even higher. In other words, the lower the oil level, the faster the HL temperature rises. This is because the smaller the amount of frying oil, the smaller the heat capacity of the oil, and the easier it is for the oil temperature and the temperature of the walls of the oil vat 10 to rise.

[0046] Here, looking at the HL temperature 180 seconds after the start of heating, it is about 80°C at the normal level, about 120°C at oil level -60mm, about 160°C at oil level -70mm, and about 170°C at oil level -90mm. 250° C. In the first embodiment of the present invention, attention is focused on the relationship between the oil level and the rise in the HL temperature, and if the HL temperature reaches (exceeds) a predetermined temperature (e.g., 100° C.) within a predetermined time (e.g., 180 seconds) from the start of heating, it is determined that the oil level is abnormally low, and heating is stopped (IH coil 20 inverter is turned off).

[0047] The above-mentioned predetermined time of 180 seconds and high limit temperature of 100°C are merely examples of set values. The control program stored in the controller 63 is designed to be able to change parameters to speed up the detection time or lower the detection temperature. The above-mentioned set values ​​are set in consideration of the influence of erroneous detection due to temperature errors and the reliability of detection performance. That is, if the set time is too short or the set temperature is too low, heating may be stopped or an alarm may sound even if the oil level is not a problem, which may cause an impediment to cooking. On the other hand, if the set time is too long or the set temperature is too high, the oil level abnormality may be determined too late or smoke may increase before the abnormal stop.

[0048] According to this embodiment, an abnormally low oil level in the oil vat 10 can be detected early and heating can be stopped. Unlike the embodiment of the present invention, if heating is stopped simply by detecting when the high limit temperature reaches a certain threshold temperature (e.g., 220°C) without considering the relationship between the time after heating starts and the high limit temperature, the detection is made due to heat conduction caused by overheating of the oil vat itself, so abnormality detection is delayed (e.g., 150 seconds when empty of oil, in the case of a tabletop fryer). On the other hand, it takes about 55 seconds after heating starts for the HL temperature to reach 100°C when empty of oil. Comparing 150 seconds and 55 seconds, the embodiment of the present invention is about one-third faster.

[0049] If the situation worsens before reaching the 150 seconds mentioned above, a large amount of smoke may be generated, filling the kitchen with smoke and causing the smoke detector to go off (in the worst case scenario, it may ignite or catch fire, with a flash point of 300-320°C and an ignition point of 370-400°C). If this happens, it can seriously disrupt the business of the store where the fryer is installed and the surrounding stores.

[0050] Second embodiment Next, a second embodiment of the present invention will be described. 7 is a graph showing an example of the transition of the temperatures detected by the oil temperature sensor (OS) and the high limit (HL) temperature sensor after the start of heating when the frying oil is at a normal level and the oil temperature at the start of heating is room temperature. The vertical axis is temperature and the horizontal axis is elapsed time. In the figure, the thin two-dot chain line indicates the change in temperature detected by the oil temperature control thermometer (OS, 41) when the oil level is normal, and the thick solid line indicates the change in temperature detected by the high limit temperature sensor (HL, 45) when the oil level in the oil tank is normal.

[0051] The OS temperature (thin double-dashed line) hardly rises for about two minutes after heating starts. This happens because the oil heated by the IH coil 20 rises up from the OS due to convection. After two minutes from when heating starts, the oil at the OS level also begins to rise in temperature. The curve of the temperature rise is almost linear (with some ups and downs). Then, once it reaches the set temperature (175°C in this case), it remains almost constant (with some ups and downs due to the ON / OFF control of the IH coil).

[0052] The HL temperature (thick solid line) rises suddenly for about 1.5 minutes after heating starts. This happens because the tank plate that the HL is in contact with has good thermal conductivity, so it is easily heated by the heat from the heating means. After 1.5 minutes after heating starts, the HL temperature rise curve is almost linear. Then, once the oil temperature reaches the set temperature, 175°C in this case, it remains almost constant (there are some slight fluctuations due to the effects of ON / OFF control).

[0053] Looking at the relationship between the OS temperature and the HL temperature, when the temperature rises after heating has started, HL>OS. This is because the bath plate to which the HL is in contact receives heat from the heating means and has good thermal conductivity, so its temperature rises easily, whereas the OS is immersed in frying oil, which is gradually rising in temperature from room temperature. Frying oil is heated through the following physical phenomena: IH coil electromagnetic induction ⇒ bath plate Joule heat ⇒ heat transfer to the frying oil ⇒ the entire oil rises in temperature as the oil convects. Therefore, there is a time lag in the rise in temperature of the frying oil, or conversely, the temperature of the bath plate rises first.

[0054] After the temperature rise is completed (about 20 minutes later in the graph of Fig. 7), the relationship between the OS temperature (TOS) and the HL temperature (THL) is TOS > THL. This is the case in this example due to the following reasons. That is, when the temperature rise is completed (= the set temperature is reached), the heating temporarily stops, and then the ON-OFF control of the coil current is started to maintain the oil temperature (temperature control). Since the reference for temperature control is the OS temperature, the temperature of HL, which is located lower than OS, becomes THL < TOS due to the influence of oil convection. Also, since the position of HL is slightly above the upper end of the IH coil 20 and is slightly away from the part of the tank wall heated by the IH coil 20, THL > TOS does not occur even for the duration of the ON time of the ON-OFF control.

[0055] In the state of Fig. 7 (normal oil level, heating starts from normal oil temperature), the maximum temperature difference between the HL temperature and the OS temperature is 41 °C about 2 minutes after the heating starts. This is what happens when the oil level is abnormally low. In that case, the OS temperature sensor comes out into the air above the oil surface (see Fig. 4(B)). Then, the OS temperature becomes lower than the oil temperature, and the temperature difference between the HL temperature and the OS temperature during the temperature rise becomes larger. Then, during the temperature rise after the heating starts, the above maximum temperature difference of 41 °C can be considered as the maximum temperature difference when the oil level is normal.

[0056] In addition, when a situation occurs where the oil catches fire and the flame hits the OS temperature sensor, the OS temperature rises. However, since the theme of the oil level abnormality detection technology of the present invention is the state before the oil catches fire or ignites, the oil ignition / ignition state does not need to be considered.

[0057] As shown in Figure 6, when the oil level is abnormally low, the HL temperature is higher than when the oil level is normal, except immediately after heating starts (because the OS temperature is the air temperature, the IH coil 20 is kept fully energized and the temperature of the tank plate rises steadily). Therefore, when the oil level is abnormally low, the HL temperature - OS temperature (temperature difference) is larger than when the oil level is normal. Therefore, when THL - TOS ≥ ΔT1 (for example, 55°C), it is possible that the oil level is abnormally low, and it can be determined that there is an abnormality. In other words, when the temperature difference between the oil temperature and the high limit is detected to be 41°C or more (for example, 55°C) after heating starts, it is determined that the oil level is below the appropriate oil level line, and by adding a function to stop heating, the oil level abnormality detection function can be improved.

[0058] Third embodiment (oil leak detection) Next, oil level abnormality detection (oil leakage detection) according to the third embodiment will be described. Figure 8 is a graph showing an example of the transition of the temperature (TOS) detected by the oil temperature sensor (OS) and the temperature (THL) detected by the high limit temperature sensor (HL) when the set oil temperature is being maintained and frying oil leaks and drops below the normal level. The vertical axis represents temperature and the horizontal axis represents elapsed time. A typical situation in which oil leakage occurs is when the opening / closing valve 19b of the oil drain pipe 19a is open. In the figure, the thin two-dot chain line indicates the change in the temperature (TOS) detected by the oil temperature control thermometer (OS, 41), and the thick solid line indicates the change in the temperature (THL) detected by the high limit temperature sensor (HL, 45).

[0059] In the graph of FIG. 8, the oil level drops further to the right (as time passes), and at 60 seconds, as indicated by the vertical dashed line at A, the OS begins to come into contact with the air. Between 0 and 60 seconds, the temperature (TOS) detected by the oil temperature sensor (OS) and the temperature (THL) detected by the high limit temperature sensor (HL) are almost constant. During this period, TOS is the actual temperature of the frying oil, and is a constant set value. In this example, THL during this period is about 15°C lower than TOS. The reason that THL is lower than TOS is as described above (paragraph 0054).

[0060] After about 60 seconds (time A) when the OS starts to come into contact with the air, the TOS (two-dot chain line) starts to gradually decrease. This is because the upper part of the sheath of the OS in contact with the frying oil comes into contact with the air and starts to cool. The air above the oil surface is cooled by air convection. Note that the time described in this embodiment is an example and will vary depending on factors such as the speed of oil leakage. Also, the TOS may start to decrease a little after the OS starts to come into contact with the air (because the sheath has good thermal conductivity).

[0061] In the graph of Figure 8, from about 60 seconds (point A), THL gradually rises. This is because TOS starts to drop from the set temperature, so the output of the IH coil 20 increases in an attempt to restore (raise) the oil temperature to the set value, and the temperature of the vat plate of the oil vat 10 rises. Then, at about 70 seconds (vertical dashed line B), the TOS, which is dropping, and the THL, which is rising, intersect, and thereafter THL becomes higher than TOS.

[0062] After that, at about 100 seconds, THL becomes about 180°C, TOS becomes about 150°C, and THL becomes about 30°C higher than TOS. In other words, it can be confirmed that the state of TOS>THL from 0 to 60 seconds (vertical dashed line A) is clearly reversed at about 100 seconds. In this embodiment, it is determined at this point that an oil leakage abnormality has occurred. In the graph of Figure 8, even after 100 seconds, THL continues to gradually increase and TOS continues to gradually decrease. However, this is the case in an experiment in which oil leakage and coil power supply continued, and in an actual machine, the power to the IH coil 20 is cut when the above-mentioned temperature reversal is confirmed, so after that, each temperature drops rapidly.

[0063] In this embodiment, after the OS reaches the set temperature, if HL-OS≧ΔT2 (e.g., 30°C), the OS temperature sensor 41 is deemed to be exposed to air and an abnormality is detected. This makes it possible to detect an oil leak early on at a low THL (e.g., 170°C) and prevent the oil temperature from rising any further.

[0064] The main points of the operation and configuration of this embodiment are summarized below. (1) An oil leak occurs, the oil level falls below the TOS, the TOS begins to come into contact with air, and a temperature drop occurs (around "60 seconds" in Figure 8). (2) On the other hand, THL has the characteristic of increasing temperature when the oil level drops below a certain level (after "around 60 seconds" in Figure 8). (3) According to the above temperature characteristics (1) and (2) of TOS and THL during an oil leak, when an oil leak occurs, the temperature transitions of the oil temperature sensor and the high limit tend to reverse. Therefore, when the reversal range of the temperature transitions of the oil temperature sensor and the high limit detects a difference of 30°C, it is determined that an oil leak has occurred and heating is stopped.

[0065] The above setting of a 30°C temperature difference between the oil temperature sensor and the high limit is just one example of the set time, and the software can be configured to narrow the temperature difference by changing the parameters of the program installed in the controller. The 30°C temperature difference setting is an example of a set value that takes into account the impact of false detection due to temperature errors, etc., and the reliability of detection performance.

[0066] 3 is a block diagram showing the configuration of a power supply system and a control system of a fryer according to an embodiment of the present invention. A power line 72 is connected from a three-phase power source R·S·T shown in the upper left of the figure to an inverter 67 via an earth leakage breaker (ELB) 71. The inverter 67 converts commercial AC current into high-frequency current. An IH coil 20 is connected to the inverter 67, and high-frequency current is applied to the coil 20. The IH coil 20 forms a high-frequency magnetic field, which induces eddy currents in the vat plate of the oil vat 10 (the inclined bottom surface (oil vat bottom) 13 in FIG. 1) located in the magnetic field, generating Joule heat due to the resistance of the vat plate.

[0067] The oil vat 10 is equipped with a temperature sensor OS41 for controlling the oil temperature and a high limit temperature sensor 45 for detecting abnormally high temperatures. The configuration and arrangement of these temperature sensors are as described above (paragraphs 0036-0038). The important points are that OS41 protrudes from the vat plate into the vat and detects the temperature of the frying oil in the vat, and HL45 is in close contact with the outer surface of the vat plate slightly above the IH coil and detects the temperature of the vat plate. In addition, OS41 is located 25 mm (for example) higher than HL45.

[0068] The signal lines from both temperature sensors 41 and 45 are connected to a controller 63, and temperature signals are sent from the sensors to the controller. A remote control 61 is also connected to the controller 63. The remote control can be used to set the fryer's temperature and other operating parameters.

[0069] A switch 65 for cutting off the heating current is connected to the controller 63. The controller 63 performs the temperature-related calculations described in the embodiment, judges abnormality alarms, issues commands to cut off the heating current, etc. The abnormality judgement and command control program to be installed in the controller can be created by using a commercially available sequencer, or a commercially available thermocontroller and PLC (Programmable Logic Controller), etc., and adding a program conforming to the flowchart in Figure 5 (by requesting a PLC manufacturer, for example).

[0070] 5 is a flowchart showing the overall operation of the oil level abnormality judgment program. First, when heating starts (S101), it is judged whether the HL temperature at the start of heating is below 50°C (S102). If the judgment is Y (if the oil temperature at the start of heating is close to room temperature), the process proceeds to S103, where it is judged whether the HL reaches 100°C (Y) or not (N) within 180 seconds after the start of heating. If it is Y, the process proceeds to S104, where it is judged that the oil level is abnormal and heating is stopped.

[0071] If HL is not below 50°C when heating starts in S102 (N), proceed to S105, where the temperature difference between HL and OS is checked to determine whether the difference is above 55°C. If the difference is above 55°C (Y), proceed to S104, where it is determined that the oil level is abnormal and heating is stopped. If S105 is No (N), proceed to S106.

[0072] In S106, it is checked whether the OS has reached the set temperature (cooking temperature). If the set temperature has been reached (Y) (after the cooking temperature has been reached), the process proceeds to S107, where it is determined whether the HL is 30° C. or more higher than the OS (Y) or not (N). If S106 is N, the process returns to the original S102. If S107 is Y, proceed to S104, determine that the oil level is abnormal, and stop heating. If S107 is N, return to the original S102.

[0073] In the fryer temperature control shown in this flowchart, the oil level abnormality detection of the first embodiment (S103), the second embodiment (S105), and the third embodiment (S106-S107) are combined, which enables prompt detection of an abnormal drop in the oil level after heating starts, as well as timely detection of an abnormal drop in the oil level during the temperature rise stage and the temperature maintenance stage.

[0074] Detailed explanation of temperature sensor location The points regarding the location of the HL temperature sensor are listed below. (1) At a position not lower than IH coil 20 If the HL temperature is lower than the IH coil 20, the HL temperature does not rise until the oil level drops significantly, which is bad because oil leaks and abnormally low oil levels cannot be detected at the beginning of operation (first embodiment). Also, if the HL temperature is lower in the heated side wall, the rise curve of the HL temperature becomes gentler, which makes it impossible to achieve the purpose of this embodiment of detecting oil leaks as early as possible, which is also bad. If the HL temperature is located at a position overlapping with the IH coil 20, the HL temperature may become higher than the OS temperature during temperature maintenance, and the temperature inversion phenomenon of the third embodiment (3 in FIG. 6) may become unclear.

[0075] (2) A location that is not affected by electromagnetic waves from the IH coil If the HL temperature sensor is located within about 10 mm from the end of the IH coil 20, the electromagnetic waves generated by the coil may prevent the sensor from detecting the temperature accurately, which may interfere with normal cooking. Figure 9 is a graph showing the temperature detected by the HL temperature sensor when it is attached near the coil (3 mm from the end). The vertical axis is temperature (°C) and the horizontal axis is time.

[0076] In the graph of FIG. 9, the HL temperature from the start of heating to the temperature holding state is shown by a thick solid line. It can be seen that there is a spike (sharp peak) on the temperature line. This spike is thought to be caused by electromagnetic noise from the IH coil adversely affecting the thermoelectromotive force of the HL temperature sensor (thermocouple with round terminal shape). The presence of this spike poses the risk of an adverse effect in which the temperature cannot be detected accurately. To avoid this risk, it is preferable to position the HL about 10 mm away from the end of the IH coil 20.

[0077] (3) Closest to the coil heating surface It is necessary to quickly detect thermal changes due to heating, and for that purpose, it is preferable to install the HL temperature sensor in a position that is not affected by electromagnetic waves from the coil and is closest to the coil heating surface, for example, between 10 and 15 mm from the end of the IH coil 20.

[0078] (4) After the set temperature is reached, it is preferable that THL is lower than TOS by about 10 to 30° C. This is to clearly recognize the “reversal of the OS temperature and the HL temperature” in the third embodiment.

Claims

1. An oil tank (10) for storing frying oil; A heating means (20) for heating the oil tank; a tank plate temperature sensor (45, high limit, HL) for detecting the temperature of the tank plate (13) of the oil tank (10); A fryer (1) comprising: The controller (63) takes into consideration the relationship between the elapsed time after the start of heating and the temperature (HL temperature) detected by the tank plate temperature sensor (45) and stops heating and / or issues an alarm.

2. 2. The fryer according to claim 1, wherein the fryer is judged to be abnormal if the temperature HL exceeds a predetermined temperature T2 before a predetermined time has elapsed after the start of heating.

3. 3. A fryer according to claim 2, wherein the controller (63) checks whether the HL temperature at the start of heating is room temperature (T1 or lower) or not, and performs the judgment of claim 2 only if the HL temperature is room temperature.

4. An oil tank (10) for storing frying oil; A heating means (20) for heating the oil tank; an oil temperature sensor (41, OS) for detecting the temperature of the frying oil in the oil tank (10); a tank plate temperature sensor (45, HL) for detecting the temperature of the tank plate (13) of the oil tank (10); a controller (63) which receives signals of temperatures detected by the oil temperature sensor (41) and the tank plate temperature sensor (45) and controls the heating means (20); A fryer (1) comprising: the oil temperature sensor (41) is provided so as to protrude into the oil vat, and is located below an appropriate frying oil level in the oil vat and above the vat plate temperature sensor (45); The controller (63) stops heating and / or issues an alarm taking into consideration a difference between a temperature detected by the oil temperature sensor (41) (TOS) and a temperature detected by the tank plate temperature sensor (45) (THL).

5. 5. The fryer according to claim 4, wherein the tank plate temperature sensor (45, HL) is in contact with the tank plate to detect its temperature, and is disposed at a level lower than the oil temperature sensor (41, OS) and not lower than the heating means (20).

6. The fryer according to claim 4 or 5, characterized in that the controller (63) judges that an abnormality occurs when THL-TOS≧ΔT1, and stops heating and / or issues an alarm.

7. An oil tank (10) for storing frying oil; A heating means (20) for heating the oil tank; an oil temperature sensor (41, OS) for detecting the temperature of the frying oil in the oil tank (10); a tank plate temperature sensor (45, HL) for detecting the temperature of the tank plate (13) of the oil tank (10); a controller (63) which receives signals of temperatures detected by the oil temperature sensor (41) and the tank plate temperature sensor (45) and controls the heating means (20); A fryer (1) comprising: the oil temperature sensor (41) is provided so as to protrude into the oil vat, and is located below an appropriate frying oil level in the oil vat and above the vat plate temperature sensor (45); the controller (63) stops heating and / or issues an alarm in consideration of the relationship between the elapsed time after the start of heating and the temperature (HL temperature) detected by the tank plate temperature sensor (45); The controller (63) takes into consideration a difference between the temperature detected by the oil temperature sensor (41) and the temperature detected by the tank plate temperature sensor (45) to stop heating and / or issue an alarm.

8. An oil tank (10) for storing frying oil; A heating means (20) for heating the oil tank; an oil temperature sensor (41, OS) for detecting the temperature of the frying oil in the oil tank (10); a tank plate temperature sensor (45, HL) for detecting the temperature of the tank plate (13) of the oil tank (10); a controller (63) which receives signals of the detected temperature (TOS) of the oil temperature sensor (41, OS) and the detected temperature (THL) of the tank plate temperature sensor (45, HL) and controls the heating means (20); A fryer (1) comprising: the oil temperature sensor (41) is provided so as to protrude into the oil vat, and is located below an appropriate frying oil level in the oil vat and above the vat plate temperature sensor (45); The fryer is further characterized in that the controller (63) judges that an abnormality has occurred when THL-TOS≧ΔT2 after the OS has reached a set temperature, and stops heating and / or issues an alarm.

9. 9. The fryer according to claim 8, wherein after the frying oil level reaches the OS set temperature at a normal level, the THL is about 10 to 30° C. lower than the TOS.

10. An oil tank (10) for storing frying oil; an induction coil (20) for heating the oil tank; A fryer (1) comprising a tank plate temperature sensor (45, high limit, HL) for detecting the temperature of a tank plate (13) of the oil tank (10), The tank plate temperature sensor (45, HL) is in contact with the tank plate to detect its temperature, and is disposed at a level not lower than that of the IH coil (20), in a position not adversely affected by electromagnetic waves from the coil, and in close proximity to the coil.

11. a tank for a liquid medium for heating the object to be heated is provided instead of the oil tank (10); 11. The liquid medium heating device according to claim 1, further comprising a temperature sensor for detecting the temperature of the liquid medium, instead of the oil temperature sensor (41, OS).

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