CN109028172B - Electric stove for preventing edible oil from spontaneous combustion in cooking by using temperature control and method thereof - Google Patents
Electric stove for preventing edible oil from spontaneous combustion in cooking by using temperature control and method thereof Download PDFInfo
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- CN109028172B CN109028172B CN201810584331.2A CN201810584331A CN109028172B CN 109028172 B CN109028172 B CN 109028172B CN 201810584331 A CN201810584331 A CN 201810584331A CN 109028172 B CN109028172 B CN 109028172B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C7/00—Stoves or ranges heated by electric energy
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C7/00—Stoves or ranges heated by electric energy
- F24C7/06—Arrangement or mounting of electric heating elements
- F24C7/067—Arrangement or mounting of electric heating elements on ranges
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C7/00—Stoves or ranges heated by electric energy
- F24C7/08—Arrangement or mounting of control or safety devices
- F24C7/082—Arrangement or mounting of control or safety devices on ranges, e.g. control panels, illumination
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electric Stoves And Ranges (AREA)
- Control Of Resistance Heating (AREA)
- Frying-Pans Or Fryers (AREA)
Abstract
An electric stove and a method thereof for preventing spontaneous combustion of edible oil during cooking using temperature control. The invention discloses a method for preventing edible oil from spontaneous combustion in cooking by controlling the temperature of a heating area and an electric stove thereof. The electric stove at least comprises a piece of glass, at least one heat source is arranged below the glass, each heat source also comprises a temperature sensor and a control unit, wherein the temperature sensor measures the temperature at the bottom of the glass in the heating area, the control unit is electrically connected with the heat source and compares the measured temperature with the upper limit and the lower limit of the preset temperature, and then the output power of the heat source is reduced or increased, so that the highest temperature of the edible oil in the cooker can be limited below the self-ignition point of the edible oil, and the lowest temperature of the edible oil can still meet the required cooking performance. The preset upper and lower temperature limits are determined by the corresponding relation between the temperature of the heating area and the temperature of the edible oil in the cooker.
Description
Technical Field
The invention relates to an electric stove with temperature limiting control function, in particular to an electric stove with glass panel heating, which can prevent edible oil from self-igniting during cooking by limiting the highest temperature of a glass heating area, and can still provide the lowest oil temperature required by cooking performance.
Background
In many countries, the main cause of kitchen fires is unattended cooking. When people cook food in homes, student apartments, senior apartments, hotel suites with kitchens, etc., due to carelessness, forgetfulness, or lack of consciousness of safe cooking, a cooker filled with edible oil is left on a heat generating area of an electric stove, and since the temperature of the heat generating area can be raised to 650 ℃, which is much higher than the self-ignition point of the edible oil, generally 360 ℃ to 400 ℃, the edible oil left on the heat generating area for a long time is spontaneously ignited at high temperature.
Cooking fires and smoke can cause a number of preventable deaths, personal injuries and property losses each year. Therefore, preventing the ignition of cooking oil in cooking is very important for individuals, housing management companies, insurance companies, fire departments, cooking equipment manufacturers, and governments. Safety problems caused by ignition of edible oil during cooking have gradually attracted attention. For example, from 2015, UL858(UL household fire safety standard) requires that fires using mosquito coil hot plates must pass the UL 85860A mosquito coil hot plate oil auto-ignition test. According to the UL 85860A test requirements, a pan containing edible oil is placed on the surface of the mosquito coil heating plate and the electric stove should be capable of heating at the highest power setting for 30 minutes without causing spontaneous combustion of the edible oil. This new safety standard is currently only applied to electric fires using mosquito coil heating plates, and for this type of fire manufacturers have provided some solutions. However, cooktop manufacturers do not provide a solution for effectively preventing the spontaneous ignition of edible oils on other electric stoves, particularly electric stoves using glass plates, and thus UL and other safety standards have not required that the prevention of spontaneous ignition of edible oils be imposed on other electric stoves.
In each of the two sets of electric furnaces sold in north america, there is one set of glass plate electric furnace. The electric stove has simple structure, low manufacturing cost, high reliability, easy maintenance and wide use all over the world. The electric furnace is internally provided with a temperature limiter which is connected with the heating source in series, and the surface temperature of the glass plate of the electric furnace is limited below 600 ℃ so as to prevent the damage of internal components or the glass plate due to overhigh temperature. However, the temperature limiter limits only the surface temperature of the glass plate of the electric stove, and cannot prevent the edible oil from self-igniting during the cooking process.
U.S. patent 7307246 to Smolenski provides a system for sensing and limiting the temperature of cookware placed on an electric ceramic stove. However, it does not provide a solution to prevent spontaneous ignition of the edible oil during cooking, nor does it maintain a minimum edible oil temperature for desired cooking performance.
United states patent 9132302 to Longo provides a measuring device and algorithm for preventing spontaneous combustion of cooking oil in gas, mosquito coil and electric ceramic stoves. However, it does not disclose details of how the system works on a glass sheet fire, such as sensor placement and wiring, upper and lower temperature limit settings, control cycles, etc. In addition, the algorithm controls the bottom temperature of the cookware to be always below the edible oil auto-ignition temperature, which is not an effective way to prevent the edible oil from auto-igniting while still maintaining the desired cooking performance.
These above inventions merely replace the real-time temperature of the cookware based on the temperature measured by the sensor under the glass heating zone, while assuming that this is also the true temperature of the cooking oil and compare it with the self-ignition temperature of the cooking oil. However, there is a significant difference between the temperature measured under the glass and the true temperature of the cooking oil, subject to a number of factors, the temperature transfer model (temperature transfer from under the glass plate to the cooking oil in the cookware) of which includes the design of the temperature sensor itself, the placement of the temperature sensor (e.g., whether the sensor is in direct contact with the bottom of the glass, or if there is a gap between the sensor and the glass), the hot plate type and output power, and the cookware type. In the case where the relationship between the oil temperature in the cooker and the temperature under the glass heat generation region is not determined, the temperature of the cooking oil in the cooker cannot be effectively controlled, and the minimum oil temperature required for the desired cooking performance cannot be maintained. The present invention addresses these problems.
The differences from the background of the invention will be clearly understood from the disclosure, drawings and description of the invention given below.
Disclosure of Invention
The technical problem underlying the present invention is to provide an electric stove and a method for temperature limit control using a heat generating zone, by which the electric stove is capable of preventing spontaneous combustion of edible oil during cooking while still maintaining a minimum oil temperature required for desired cooking performance.
The technical scheme adopted by the invention for solving the technical problems is to provide an electric stove with the function of preventing the edible oil from spontaneously combusting in cooking, which at least comprises: a glass plate for supporting and heating a cooker; at least one heating plate is arranged below the glass plate; each heating plate is provided with a sensor for measuring the temperature of the glass heating area and a control unit connected with the heating plate and used for adjusting the output power of the heating plate; the control unit compares the measurement result of the temperature sensor with a preset upper temperature limit and a preset lower temperature limit, and the temperature limit is determined by the corresponding relation between the temperature of the glass heating area and the temperature of the cooking edible oil; when the measured temperature reaches the upper temperature limit, the control device reduces the output power of the heating plate; when the measured temperature reaches the lower temperature limit, the control unit increases the output power of the heating plate, so that the temperature of the edible oil in the cooker is limited to be circulated in a controllable range, the highest oil temperature is kept below the self-ignition point of the edible oil, and meanwhile, the lowest oil temperature required by cooking is still kept.
The electric furnace described above, wherein the upper temperature limit is determined based on the relationship between the temperature of the glass heat generation area measured by the sensor and the temperature of the edible oil in the cooker and the self-ignition temperature of the edible oil, and is affected by: the type of the temperature sensor, the installation method and the position of the temperature sensor, the type and the output power of the heating plate, the type of the cooker, and the like. The upper temperature limit is set so that when the temperature of the heating area reaches the upper temperature limit, the highest temperature of the edible oil in the cooker approaches to but never reaches the self-ignition point of the edible oil.
The electric stove as described above, wherein the lower temperature limit is determined based on the relationship between the temperature of the glass heat generation area measured by the sensor and the temperature of the edible oil in the cooker and the minimum oil temperature required for cooking, and the lower temperature limit is set such that when the temperature of the heat generation area reaches the lower temperature limit, the temperature of the edible oil in the cooker reaches the minimum temperature required for cooking.
The electric furnace comprises a temperature limiter, wherein the temperature limiter comprises a control unit connected with the heating plate and a temperature probe encapsulated in a multilayer sleeve with an inner heat insulation layer and an inner heat insulation layer; the sleeve reduces the heat radiated from the heating plate to the temperature probe, so that the temperature measured by the temperature probe reflects the temperature of the glass heating area; and the control unit of the temperature limiter compares the temperature measured by the probe with a preset upper temperature limit and a preset lower temperature limit, and controls the output power of the heating plate.
The electric furnace as described above, wherein the multi-layered sleeve is made of ceramic, glass or steel.
The electric furnace described above wherein the multilayer sleeve further comprises a metal reflective coating between the inner and outer insulating layers.
The electric furnace, wherein the temperature sensor is arranged at the bottom of the glass heating area and used for measuring the temperature of the glass heating area and sending the temperature measurement result to the control circuit and the control unit; the control unit integrated in the control circuit is electrically connected with the heating plate.
The electric furnace, wherein the temperature sensor comprises a temperature probe, a heat insulating material and a ceramic shell; the temperature probe directly contacting the glass is surrounded by an insulating material, wherein the insulating material is compressed between the glass and the ceramic case, thereby isolating heat radiated from the heat generating plate to the probe and the small piece of glass wrapped in the insulating material, whereby the cooker placed on the heat generating area of the glass becomes a main heat source of the probe and the small piece of glass wrapped in the insulating material.
The electric furnace as described above, wherein the temperature sensor is adhered to the bottom of the glass heat generating area.
The electric furnace as described above, wherein the temperature sensor is pressed against the bottom of the glass heating zone by elastic means.
In the electric furnace, when the heating wire in the heating plate is placed, a non-heating area is left under the temperature sensor, so as to further reduce the heat radiated from the heating plate to the sensor.
The electric furnace, wherein the temperature sensors can be single or a plurality of same devices, are distributed at different areas at the bottom of the glass heating area.
The electric furnace, wherein the temperature sensor may be a fiber optic temperature sensor, a resistance temperature sensor, a high temperature thermistor, a Polymer Derived Ceramic (PDC) sensor, or a thermocouple.
The electric furnace is characterized in that an infrared coating is added on the surface of the sensor, which is in contact with the glass, so that the temperature measurement performance is improved.
The electric furnace as described above, wherein the control unit is a single relay, a group of relays, or a Silicon Controlled Rectifier (SCR).
The electric furnace described above, wherein the temperature sensor and the control unit are integrated in one temperature controller, and the temperature controller is placed at the bottom of the glass heat generation region.
The electric furnace described above, wherein the temperature controller comprises a temperature sensor, a control unit, a heat insulating material and a ceramic case; wherein, the temperature sensor of the controller is directly contacted with the bottom of the glass heating area and is electrically connected with the control unit; the control unit is electrically connected with the heating plate; the temperature sensor and control unit are surrounded by an insulating material, wherein the insulating material is compressed between the glass and the ceramic housing for insulating heat transferred from the heat-generating plate to the sensor and glass within the insulating material, thereby making the cookware placed on the glass heat-generating region the primary heat source for the sensor box and glass within the insulating material.
The electric furnace, wherein the temperature controller is adhered to the bottom of the glass heating area.
The electric furnace, wherein the temperature controller is pressed against the bottom of the glass heating area by an elastic device.
In the electric furnace, when the heating wire in the heating plate is placed, a non-heating area is left under the temperature controller, so as to further reduce the heat transferred from the heating plate to the controller.
In the above electric furnace, the temperature controller is a bimetallic temperature controller.
The electric fire above wherein further comprising a "hot glass" indicator light connected to a sensor that measures the temperature of the hot zone of the glass and configured to illuminate when the temperature of the hot zone reaches a predetermined temperature to alert a user that the hot zone is hot.
The electric stove further comprises an automatic shutdown function, namely after any heating plate is electrified to work, the power selector of the electric stove is not changed by a user within a preset time, and all the heating plates are forcibly turned off.
The electric stove described above, wherein the control unit is configured to achieve rapid cycling of temperatures between 10-60 seconds by using a narrow range of upper and lower temperature limits to meet cooking requirements for higher cooking temperatures while still preventing spontaneous ignition of the edible oil.
The electric furnace, wherein the heating plate has a rated output power of 500W to 3500W.
The electric furnace, wherein the heating plate is a radiation heating plate.
The electric furnace, wherein the heating plate is an infrared halogen lamp.
In the electric furnace, the heating plate is an electromagnetic heating element.
Another technical solution adopted by the present invention to solve the above technical problems is to provide a method for preventing spontaneous combustion of edible oil in cooking using temperature control, in which a heating zone temperature limit control is applied to an electric cooker to prevent spontaneous combustion of edible oil in the cooking process while maintaining a minimum oil temperature required for desired cooking performance, comprising a. testing to determine a relationship between a temperature of a heating zone and a temperature of edible oil in a cooker; b. setting an upper temperature limit for controlling the output power of the heating source based on the relationship, limiting the highest temperature of the edible oil in cooking below the self-ignition point of the edible oil, and setting a lower temperature limit to keep the temperature of the edible oil above the minimum temperature required by the expected cooking performance; c. forming a small heat insulation area in the heat generation area to cut off heat transfer from the heat source to the heat insulation area, and using a cooker placed on the heat generation area as a main heat source of the heat insulation area; d. the temperature sensor measures the temperature of the heat insulation area; e. comparing the measured temperature with the upper and lower temperature limits, and reducing the output power of the heating source when the measured temperature reaches the upper temperature limit; when the measured temperature reaches the lower temperature limit, the output power of the heating source is increased.
Compared with the prior art, the invention has the following beneficial effects: the invention provides an electric stove for preventing edible oil from spontaneous combustion in cooking by using temperature control and a method thereof. The sensor directly contacts with the bottom of the glass heating area to measure the temperature of the glass, the control unit is electrically connected with the heating plate, the temperature of the heating area measured by the sensor is compared with the preset upper and lower temperature limits to adjust the output power of the heating plate, and the temperature of the glass heating area is controlled and limited to prevent the spontaneous combustion of the edible oil in the cooking process and simultaneously keep the required cooking performance.
In order to limit the temperature of the cooking oil below the self-ignition point, it is necessary to obtain the temperature of the cooking oil in the cooker by measuring the temperature of the glass heat generation region in contact with the cooker.
Based on a large number of experiments, the invention establishes a transfer model of the edible oil with temperature transferred into the cooker from the lower part of the glass heating area. The real-time edible oil temperature can be obtained by utilizing the temperature transfer model and the measured heating area temperature. The upper and lower preset temperature limits of the control unit are determined based on the temperature transfer model, the temperature ignition point of the edible oil and the cooking performance requirements.
When the temperature of the edible oil in the cooker is close to (but can not reach) the self-ignition point of the edible oil, usually 360 ℃ to 400 ℃, the measured temperature of the heating area reaches the upper limit temperature, the control unit reduces the output power of the heating plate, and the highest temperature of the edible oil is limited below the self-ignition point; when the temperature of the edible oil in the cooker is reduced to the minimum cooking temperature required to be cooked, the measured temperature of the heating area reaches the lower limit temperature, and the control unit increases the output power of the heating plate, so that the temperature of the edible oil is increased or maintained to maintain the minimum cooking temperature required to be cooked. Thereby creating a controlled cycle of the temperature of the edible oil and the power change of the heating pan and the maximum temperature of the edible oil is limited below the self-ignition point of the edible oil while the electric stove still meets the minimum oil temperature required for the desired cooking performance.
Drawings
The particular features and advantages of the invention, as well as other objects, will become apparent from the following description of the drawings in which:
FIG. 1 is a perspective view of an electric furnace with a glass surface removed;
FIG. 2 is a front view of the glass surface of the electric furnace shown in FIG. 1;
FIG. 3 is a partial front view of the furnace shown in FIG. 1 with the temperature limiter of the hot plate using a long sleeve and with the furnace glass partially removed;
FIG. 4 is a partial front view of the furnace shown in FIG. 1 with the temperature limiter of the hot plate using a short sleeve and with the furnace glass partially removed;
FIG. 5 is a partially exploded view of an electric fire including a heat generating plate, a temperature sensor and a portion of glass;
fig. 6 is a front view of the heat generating tray shown in fig. 5;
figure 7 is a flow chart of a control circuit for the fire of figures 5 and 6;
FIG. 8 is a cross-sectional view of a portion of an electric furnace in which a 2-in-1 temperature controller is mounted on one side of a heat-generating plate;
fig. 9 is a cross-sectional view of a portion of an electric furnace in which a 2-in-1 temperature controller is mounted in the center of a heat-generating plate.
Detailed Description
The invention is further described below with reference to the figures and examples.
In one embodiment, as shown in fig. 1, 2, 3 and 4, a two-hole electric ceramic furnace comprises a glass plate 201, two heating plates 103 under the glass, a temperature limiter 104 of each heating plate and two heating zones 202. When the heating plate is powered on, heat is transferred from the heating wire to the bottom of the glass heating area and then to the cookware and the edible oil in the cookware. In this embodiment, the tailored temperature limiter comprises a temperature sensor and a control unit in series with the heat generating tray. A temperature sensor 303 having a long sleeve 105 (for some large heat-generating pans) or a short sleeve 401 (for some small heat-generating pans) is made of an expandable metal and is placed within a multi-layer sleeve 301 formed by an inner and an outer insulating layer. The inner and outer insulation layers may be made of ceramic, glass or steel. A metal reflective coating is applied between the two thermal barriers. The length of the outer insulation layer is shorter than or equal to that of the inner insulation layer. By using the special sleeve, the sensor can detect the bottom temperature of the glass heating area, and only a small amount of heat of the heating plate is transferred to the temperature sensor. The control unit 302 of the temperature limiter compares the temperature measured by the sensor with preset upper and lower temperature limits and then turns on or off the power supply of the heat generating plate to control the temperature of the cooking oil in the cooker.
The following table sets forth an example of the experimental temperature transfer model of this embodiment, in which an expanded metal temperature sensor with a long sleeve, an inner insulation layer made of steel, and an outer insulation layer made of glass is placed in the center of a 2300W thermal radiation heat-generating disk and is 1.5mm lower than the glass; this example uses a cast iron frying pan and the lowest cooking temperature is defined as 250 ℃, which is the boiling point of most edible oils; in the test, the temperature of the edible oil in the cooker was measured, and the upper and lower temperature limits of the temperature limiter were determined.
| Temperature (DEG C) of the bottom of the glass heating area measured by a sensor | Temperature of edible oil (. degree.C.) | Temperature limit (. degree. C.) |
| 260 | 150 | |
| 324 | 245 | 330; lower temperature limit |
| 400 | 285 | |
| 510 | 340 | 505; upper temperature limit |
In this example, when the measured temperature of the glass heating area reaches the upper temperature limit, 505 ℃, and the temperature of the edible oil in the cooker approaches 340 ℃, the temperature limiter cuts off the power of the heating plate, and the heating wire stops heating; when the measured temperature of the sensor approaches the lower temperature limit of 330 ℃, the temperature limiter energizes the heating plate, and the heating wire starts to generate heat. Thus, the controlled temperature circulation of the edible oil is formed in the cooker, the maximum temperature of the edible oil is limited to 340 ℃, the temperature is lower than the self-ignition point of the common edible oil and ranges from 360 ℃ to 400 ℃, and the minimum temperature of the edible oil is about 250 ℃, so that the required cooking requirement is ensured. Changing the lower temperature limit will affect the controlled oil temperature cycle and the average oil temperature, which will meet different cooking performance requirements. For example, for a user who prefers high temperature cooking, raising the lower temperature limit will shorten the controlled oil temperature cycle to provide a higher cooking temperature while still preventing the edible oil from spontaneously igniting.
In some embodiments, such as a two-pronged electric ceramic furnace similar to that shown in fig. 1, as shown in fig. 5 and 6, each heating plate includes a temperature sensor 501 mounted at the bottom of the glass heating zone and a control unit integrated in the furnace control circuit 107, in addition to a standard temperature limiter 104. The temperature sensor 501 may be mounted on the sleeve 105 of the temperature limiter 104 or on a separate support tube. As shown in fig. 5, the temperature sensor 501 includes a temperature probe 602 surrounded by an insulating material 603, the insulating material 603 being compressed between the glass plate 201 and the ceramic housing 604 of the sensor. The temperature sensor is in direct contact with the bottom of the glass heat generating region 202, either glued to the bottom of the glass or pushed against the glass by a resilient means such as a coil or leaf spring 608. The insulation material surrounding the probe creates an insulated or cold zone 502 above the hot zone 202. Since the heat insulating material blocks heat from the heating plate from radiating to the probe and the cold area, and the microcrystalline glass material of the electric furnace is highly transparent to heat radiation and low in heat conductivity, when the probe measures the temperature of the cold area glass, the cooker sitting on the glass heating area radiates heat through the glass and becomes the main heat source of the cold area, namely, the heat sensed by the probe is mainly the heat of the cooker. To further reduce the amount of heat radiated directly from the heater to the probe, heater 609 is positioned to form a non-heated zone 605 directly below the temperature sensor. The output signal of the temperature sensor is sent to the control unit of the control circuit 107 shown in fig. 2 through the high temperature resistant wire 606. Fig. 7 shows an example of a flowchart of the control circuit of the present embodiment. The control unit compares the glass temperature measured by the sensor with the preset upper and lower temperature limits, and then increases or decreases the output power of the heating plate to form a controlled edible oil temperature cycle in the cooker. Accordingly, the maximum temperature of the edible oil is limited to below the self-ignition point of the edible oil, and the desired cooking performance can still be ensured.
The temperature probe in this embodiment may be a fiber optic temperature sensor, a resistive temperature sensor, a thermocouple, a high temperature thermistor, a Polymer Derived Ceramic (PDC) sensor, or any kind of temperature detector. The temperature probe may have an infrared radiation transmissive coating applied to the surface of the probe that is in contact with the glass to further improve sensor performance.
The control unit in this embodiment may be a relay, a group of relays, or a Silicon Controlled Rectifier (SCR) to adjust the output power of the heat generating plate.
The following table sets forth an example of the experimental temperature transfer model of this example, in which a polymer-derived ceramic (PDC) temperature probe was bonded to the bottom of the glass heat generation zone; the surface of the probe which is in contact with the glass is coated with a 0.1mm infrared radiation transmitting coating; the sensor is placed 35mm away from the center of the heating plate and is surrounded by a 10mm ceramic fiber heat insulation layer; the control unit is a long-life DPST power relay; in this example, a 2300W heat radiation heating pan and a cast iron frying pan were used; the minimum cooking temperature is defined as 265 ℃ which is slightly above the boiling point of typical edible oils; in the test the temperature of the edible oil in the cooker is measured and the temperature limit of the control unit is determined.
In this embodiment, when the measured temperature of the probe reaches the upper temperature limit of 340 ℃, and the actual temperature of the edible oil approaches 340 ℃, the control unit reduces the power of the heating plate, so that the heating plate generates less heat; when the measured temperature of the sensor is close to the lower temperature limit of 325 ℃, the control unit increases the power of the heating plate, so that the heating plate generates more heat. A controlled temperature cycle of the edible oil is established in the cooker and the maximum temperature of the edible oil is limited to 340 c below the self-ignition point of the edible oil while the stove is still able to maintain the minimum cooking temperature 265 c required for cooking.
In some embodiments, as shown in fig. 8, a two-in-one electric ceramic oven similar to that shown in fig. 1, each heating plate includes a two-in-one temperature controller 900 that integrates a temperature sensor 901 and a control unit 902 in a single device in addition to the standard temperature limiter 104. The temperature controller is surrounded by an insulating layer 903 which is compressed between the ceramic housing 904 and the glass. The temperature controller may be mounted on the sleeve 105 of the temperature limiter 104 or on a separate support tube. The temperature controller is in direct contact with the glass heat generating region 202, is glued to the bottom of the glass heat generating region, or is pushed against the glass by a resilient means such as a coil spring 906. The control unit is connected in series with the heating wire 609 by a conductor 905. The insulating material creates an insulating or cold zone 908 in the heat generating zone 202. The sensor in direct contact with the glass measures the cold zone glass temperature, which takes the cookware sitting on the hot zone as the main heat source, and the heat is transferred to the sensor through the cold zone glass. To further reduce direct heat radiation from the heater 609 to the temperature controller, the heater is positioned to form a non-heated region directly below the temperature controller. The control unit compares the preset upper and lower temperature limits with the temperature measured by the sensor, and then turns on or off all or part of the heating plate to supply power, thereby limiting the temperature of the edible oil in the cooker and maintaining the minimum oil temperature required for cooking.
The following table shows an example of an experimental temperature transfer model of this embodiment, in which a temperature controller, a bimetal thermostat, is adhered to the bottom of the glass heating zone 30mm from the center of the heating plate. A ceramic fiber heat-insulating layer of 10mm is arranged between the temperature controller and the ceramic outer body of the temperature controller. The surface of the temperature controller contacting the glass is coated with a 0.1mm infrared radiation transmitting coating. In this embodiment, a 2300W thermal radiation heating plate and a cast iron frying pan are used. The minimum cooking temperature was defined as 265 c, slightly above the boiling point of the edible oil, and the temperature of the edible oil in the cooker was measured in the test and the upper and lower temperature limits of the thermostat were determined.
| Temperature (DEG C) of the bottom of the glass heating area measured by a sensor | Temperature of edible oil (. degree.C.) | Temperature limit (. degree. C.) |
| 200 | 150 | |
| 275 | 265 | 280 parts of; lower temperature limit |
| 310 | 285 | |
| 380 | 340 | 375; upper temperature limit |
In this example, when the temperature measured by the cold zone glass of the thermostat reaches the upper temperature limit of 375 ℃, the thermostat powers off the heating plate, causing the heating plate to stop generating heat; when the measured glass temperature reaches the lower temperature limit of 280 ℃, the temperature controller energizes the heating disc to enable the heating disc to generate heat. A controlled temperature cycle of the edible oil is formed in the cooker and the maximum temperature of the edible oil is limited to 340 c below the self-ignition point of the edible oil while the electric stove still maintains the minimum cooking temperature required for cooking, 265 c.
Fig. 9 shows another embodiment, which is similar to the embodiment shown in fig. 8. In this embodiment, however, the temperature controller 900 is placed in the center of the heating element and the temperature limiter has a short sleeve 401.
The following table lists an example of an experimental temperature transfer model of this embodiment, in which the temperature controller is a bimetal thermostat, adhered to the bottom of the glass heat generating zone, and directly below the center of the heat generating zone. When the heating wire is wired, a non-heating area is left in the center of the heating plate and right below the temperature controller. Other test conditions were the same as in the example of fig. 8.
| Temperature (DEG C) of the bottom of the glass heating area measured by a sensor | Temperature of edible oil (. degree.C.) | Temperature limit (. degree. C.) |
| 200 | 150 | |
| 260 | 265 | 265 of a nitrogen-containing gas; lower temperature limit |
| 300 | 285 | |
| 340 | 340 | 335; upper temperature limit |
In this embodiment, when the temperature measured by the cold zone of the temperature controller reaches the upper temperature limit of 335 ℃, the temperature controller powers off the heating plate, and the heating plate stops generating heat; when the measured temperature reaches the lower temperature limit of 265 ℃, the temperature controller energizes the heating plate to make the heating plate generate heat. A controlled temperature cycle of the edible oil is formed in the cooker and the maximum temperature of the edible oil is limited to 340 c below the self-ignition point of the edible oil while the electric stove still maintains the minimum cooking temperature required for cooking, 265 c.
In some embodiments, the hot plate of the electric furnace has a rated output power between 500W and 3500W.
In some embodiments, the hot plate of the fire may be a thermal radiation hot plate, an infrared halogen lamp, or an electromagnetic hot plate.
In some embodiments, the electric stove may be a single or multiple heat generating coil head.
In some embodiments, the fire may be a fire with an oven having at least 4 heat generating pans.
In some embodiments, the electric fire uses a narrow range of preset upper and lower temperature limits that can shorten the controlled temperature cycle time, increase the cooking temperature, and still prevent spontaneous combustion of the edible oil. For example, the electric stove may be configured for a temperature control cycle time of 10-60 seconds and maintain a relatively high average cooking oil cooking temperature, 300 ℃ to 340 ℃, to provide the desired cooking performance for users requiring relatively high cooking temperatures, while still preventing spontaneous combustion of the edible oil.
In some embodiments, the fire includes a hot glass surface indicator 204, shown in fig. 2, controlled by the control circuit 107 to alert a user that the hot glass region is hot. The control circuit receives a measured temperature from a temperature sensor that measures a temperature below the heat generating region and then calculates a surface temperature of the heat generating region based on an experimental temperature transfer model. If the surface temperature of the heat-generating area is higher than a preset point, for example 50-60 ℃, the indicator is lightened until the surface temperature of the heat-generating area is lower than the preset point, and then the indicator is turned off.
In some embodiments, the fire includes an automatic shut down feature. After the heat generating plates are powered on, if the power selector 203 of fig. 2 is set to the maximum power and the user does not change the power selector of any of the heat generating plates for a preset time, for example, 60 minutes, the electric furnace automatically turns off all the heat generating plates; if the power selector is set to a point between the minimum power and the maximum power, the preset time is extended, for example, 60 to 120 minutes.
A number of preferred embodiments are described more fully above with reference to the accompanying drawings. The scope of the claims should not be limited by the preferred embodiments and examples, but should be given the broadest interpretation consistent with the description as a whole.
Claims (18)
1. An electric cooker having a function of preventing spontaneous combustion of edible oil during cooking, comprising at least:
a microcrystalline glass plate for supporting and heating a cooker;
at least one heating plate is arranged below the glass plate;
each heating plate is provided with a temperature sensor for measuring the temperature of the glass heating area and
the control unit is connected with the heating plate and is used for adjusting the output power of the heating plate;
the control unit compares the measurement result of the temperature sensor with a preset upper temperature limit and a preset lower temperature limit, and the temperature limit is determined by the corresponding relation between the temperature of the glass heating area and the temperature of the cooking edible oil;
when the measured temperature reaches the upper temperature limit, the control device reduces the output power of the heating plate;
when the measured temperature reaches the lower temperature limit, the control unit increases the output power of the heating plate, so that the temperature of the edible oil in the cooker is limited to circulate within a controllable range, the highest oil temperature is kept below the self-ignition point of the edible oil, and meanwhile, the lowest oil temperature required by cooking is still kept;
the temperature sensor is placed at the bottom of the glass heating area and used for measuring the temperature of the glass heating area and sending the temperature measurement result to the control circuit and the control unit; the control unit integrated in the control circuit is electrically connected with the heating plate; the temperature sensor comprises a temperature probe, a heat insulating material and a ceramic shell; the temperature probe directly contacting the glass is surrounded by the heat insulating material, the heat insulating material wrapping the temperature probe creates a heat insulating or cold zone on the heat generating zone, wherein the heat insulating material is compressed between the glass and the ceramic case, thereby isolating the heat radiated from the heat generating plate to the probe and the small glass wrapped in the heat insulating material, whereby the cooker placed on the heat generating zone of the glass becomes the main heat source of the probe and the small glass wrapped in the heat insulating material,
when the heating wire in the heating plate is placed, a non-heating area is reserved under the temperature sensor.
2. The electric fire according to claim 1 wherein the upper temperature limit is determined based on the relationship between the temperature of the glass heat generation region measured by the sensor and the temperature of the edible oil in the cooker and the self-ignition temperature of the edible oil, and is affected by: the type of the temperature sensor, the installation method and the position of the temperature sensor, the type and the output power of the heating plate and the type of the cooker; the upper temperature limit is set so that when the temperature of the heating area reaches the upper temperature limit, the highest temperature of the edible oil in the cooker approaches to but never reaches the self-ignition point of the edible oil.
3. The electric fire according to claim 1 wherein the lower temperature limit is determined based on the relationship between the temperature of the heat generation area of the glass measured by the sensor and the temperature of the cooking oil in the cooker and the minimum oil temperature required for cooking, and the lower temperature limit is set so that the temperature of the cooking oil in the cooker reaches the minimum temperature required for cooking when the temperature of the heat generation area reaches the lower temperature limit.
4. The electric furnace according to claim 1, characterized in that the temperature sensor is glued or pressed against the bottom of the glass heating area by elastic means.
5. The electric furnace according to claim 1, characterized in that the temperature sensors are single or multiple identical devices distributed in different areas at the bottom of the glass heating zone.
6. The electric furnace according to claim 1, wherein the temperature sensor is a fiber optic temperature sensor, a resistive temperature sensor, a high temperature thermistor, a Polymer Derived Ceramic (PDC) sensor, or a thermocouple.
7. The furnace according to claim 1 wherein an infrared coating is added to the sensor surface in contact with the glass to improve thermometry.
8. The electric fire of claim 1 wherein the control unit is a single relay, a group of relays, or a Silicon Controlled Rectifier (SCR).
9. The electric furnace according to claim 1, characterized in that the temperature sensor and the control unit are integrated in one temperature controller and the temperature controller is placed at the bottom of the glass heating zone.
10. The electric furnace according to claim 9, wherein the temperature controller comprises a temperature sensor, a control unit, an insulating material, and a ceramic case; wherein, the temperature sensor of the controller is directly contacted with the bottom of the glass heating area and is electrically connected with the control unit; the control unit is electrically connected with the heating plate; the temperature sensor and control unit are surrounded by an insulating material, wherein the insulating material is compressed between the glass and the ceramic housing for insulating heat transferred from the heat-generating plate to the sensor and glass within the insulating material, thereby making the cookware placed on the glass heat-generating region the primary heat source for the sensor box and glass within the insulating material.
11. The electric furnace according to claim 9, wherein the temperature controller is stuck to the bottom of the glass heat generating area or pressed against the bottom of the glass heat generating area by an elastic means.
12. The electric furnace according to claim 9, wherein the temperature controller is a bimetallic thermostat.
13. The fire of claim 1 further comprising a "hot glass" indicator light connected to a sensor that measures the temperature of the hot glass zone and configured to illuminate when the temperature of the hot zone reaches a predetermined temperature to alert a user that the hot zone is hot.
14. The electric fire according to claim 1 further comprising an automatic shutdown function in which after any one of the heat generating trays is operated by power on, the power selector thereof is not changed by a user for a predetermined time, and all the heat generating trays are forcibly turned off.
15. The electric fire of claim 1 wherein the control unit is configured to rapidly cycle temperatures between 10-60 seconds by using narrow range upper and lower temperature limits to meet cooking requirements for higher cooking temperatures while still preventing spontaneous combustion of the edible oil.
16. The electric furnace according to claim 1, wherein the heat generating tray has a rated output power of between 500W and 3500W.
17. The electric fire of claim 1 wherein the heat-generating plate is a radiant heat-generating plate, an infrared halogen lamp, or an electromagnetic heating element.
18. A method of preventing spontaneous combustion of cooking oil during cooking using temperature control, wherein the method of preventing spontaneous combustion of cooking oil during cooking while maintaining a minimum oil temperature required for desired cooking performance by applying a heat generating zone temperature limit control on an electric stove of any one of claims 1 to 17, comprises:
a. testing to determine the relationship between the temperature of the heating area and the temperature of the edible oil in the cooker;
b. setting an upper temperature limit for controlling the output power of the heating source based on the relationship, limiting the highest temperature of the edible oil in cooking below the self-ignition point of the edible oil, and setting a lower temperature limit to keep the temperature of the edible oil above the minimum temperature required by the expected cooking performance;
c. forming a small heat insulation area in the heating area;
blocking heat transfer from the heat source to the insulating region;
the cooker placed on the heating area is used as a main heat source of the heat insulation area;
d. the temperature sensor measures the temperature of the heat insulation area;
e. comparing the measured temperature with the upper and lower temperature limits, and reducing the output power of the heating source when the measured temperature reaches the upper temperature limit; when the measured temperature reaches the lower temperature limit, the output power of the heating source is increased.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810584331.2A CN109028172B (en) | 2018-06-08 | 2018-06-08 | Electric stove for preventing edible oil from spontaneous combustion in cooking by using temperature control and method thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810584331.2A CN109028172B (en) | 2018-06-08 | 2018-06-08 | Electric stove for preventing edible oil from spontaneous combustion in cooking by using temperature control and method thereof |
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| CN107543217B (en) * | 2016-06-28 | 2019-07-26 | 佛山市顺德区美的电热电器制造有限公司 | Electric cooking pot and its control method and device |
| CN207132985U (en) * | 2017-08-07 | 2018-03-23 | 上汽通用汽车有限公司 | Exhaust gas temperature sensor mounting structure |
| CN107860035A (en) * | 2017-11-08 | 2018-03-30 | 海盐东海电器有限公司 | A kind of electric ceramic heaters heat-generating disc with temperature limiting control function |
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