Patent Application
20190293298
The present subject matter relates generally to cooktop appliances, including cooktop appliances configured for precise temperature control.
Cooktop appliances generally include heating elements for heating cooking utensils, such as pots, pans and griddles. A user can select a desired heating level, and operation of the heating elements is modified to match the desired heating level. For example, certain cooktop appliances include electric heating elements. During operation, the cooktop appliance operates the electric heating elements at a predetermined power output corresponding to a selected heating level.
Operating the electric heating elements at the predetermined power output corresponding to the selected heating level poses certain challenges. For example, the predetermined power output is only an indirect measurement of the actual cooking temperature. Some cooktop appliances employ a temperature sensor to directly measure the temperature of a cooking utensil and/or articles contained within the cooking utensil. The measured temperature may then be used to adjust the power output above or below the predetermined level in order to achieve a cooking temperature closer to the selected heating level.
However, in certain cooktop appliances, such as radiant cooktop appliances, precise temperature control can be difficult to achieve due to noise, thermal lag or hysteresis, and limitations on the useful life of controls.
Accordingly, a cooktop appliance with features for improved precision in temperature control would be useful.
Aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.
In an exemplary aspect of the present disclosure, a cooktop appliance is provided. The cooktop appliance includes an electric heating element positioned at a cooktop surface of the cooktop appliance and a controller operably connected to the electric heating element. The controller is configured for generating a temperature setting and initiating a first cycle. The first cycle includes applying a first voltage across the electric heating element and monitoring a temperature with a temperature sensor until the monitored temperature reaches a threshold temperature. The threshold temperature is less than or equal to the temperature setting. The controller is further configured for performing a second cycle when the monitored temperature reaches the threshold temperature. The second cycle includes monitoring the temperature with the temperature sensor, calculating a difference between the monitored temperature and the temperature setting and applying a second voltage across the electric heating element over a first period of time. The second voltage is less than the first voltage. The second cycle further includes deactivating the electric heating element for a second period of time. A duration of the first period of time is based on the calculated difference between the monitored temperature and the temperature setting.
In another exemplary aspect of the present disclosure a cooktop appliance is provided. The cooktop appliance includes an electric heating element positioned at a cooktop surface of the cooktop appliance and a controller operably connected to the electric heating element. The controller is configured for generating a temperature setting and operating the electric heating element at a first power level. The controller is also configured for monitoring a temperature with a temperature sensor and inputting the monitored temperature into a closed control loop. The controller is further configured for operating the electric heating element at a second power level based at least in part on an output of the closed control loop.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. As used herein, terms of approximation, such as “generally,” or “about” include values within ten percent greater or less than the stated value.
A cooking surface 14 of cooktop appliance 12 includes a plurality of heating elements 16. For the embodiment depicted, the cooktop appliance 12 includes five heating elements 16 spaced along cooking surface 14. The heating elements 16 are generally electric heating elements. In certain exemplary embodiments, cooktop appliance 12 may be a radiant cooktop appliance with resistive heating elements or coils mounted below cooking surface 14. However, in other embodiments, the cooktop appliance 12 may include any other suitable shape, configuration, and/or number of heating elements 16, for example, the cooktop appliance 12 may be an open coil cooktop with the heating elements 16 positioned at or above surface 14. Additionally, in other embodiments, the cooktop appliance 12 may include any other suitable type of heating element 16, such as an induction heating element. Each of the heating elements 16 may be the same type of heating element 16, or cooktop appliance 12 may include a combination of different types of heating elements 16.
As shown in
As will be discussed in greater detail below, the cooktop appliance 12 includes a control system 50 (
Referring now to
In some example embodiments, the cookware temperature sensor 28 may be attached to or integrated into the cooking utensil 18 and configured to sense a temperature of, e.g., a bottom surface of the cooking utensil 18 or bottom wall of the cooking utensil 18. For example, the cookware temperature sensor 28 may be embedded within the bottom wall of the cooking utensil 18 as illustrated in
Additionally, the food temperature sensor 30 may be positioned at any suitable location to sense a temperature of one or more food items 32 (see
In certain exemplary embodiments, one or both of the cookware temperature sensor 28 and the food temperature sensor 30 may utilize any suitable technology for sensing/determining a temperature of the cooking utensil 18 and/or food items 32 positioned in the cooking utensil 18. The cookware temperature sensor 28 and the food temperature sensor 30 may measure a respective temperature by contact and/or non-contact methods. For example, one or both of the cookware temperature sensor 28 and the food temperature sensor 30 may utilize one or more thermocouples, thermistors, optical temperature sensors, infrared temperature sensors, etc.
Referring again to
Referring now also to
As stated, the cooktop appliance 12 includes a receiver 34 associated with one or more of the heating elements 16, for example a plurality of receivers 34 each associated with a respective heating element 16. For the embodiment depicted, each receiver 34 is positioned directly below a center portion of a respective heating element 16. Moreover, for the embodiment depicted, each receiver 34 is configured as a wireless receiver 34 configured to receive one or more wireless signals. Specifically, for the exemplary control system 50 depicted, both of the cookware temperature sensor 28 and the food temperature sensor 30 are configured as wireless sensors in wireless communication with the wireless receiver 34 via a wireless communications network 54. In certain exemplary embodiments, the wireless communications network 54 may be a wireless sensor network (such as a Bluetooth communication network), a wireless local area network (WLAN), a point-to point communication networks (such as radio frequency identification (RFID) networks, near field communications networks, etc.), a combination of two or more of the above communications networks, or any suitable wireless communications network or networks.
Referring still to
Referring still to
Further, the controller 52 is operably connected to each of the plurality of heating elements 16 for controlling a power level of each of the plurality of heating elements 16 in response to one or more user inputs through the user interface 62 (e.g., control panel 22 and controls 24). Specifically, for the embodiment depicted, the controller 52 is operably connected to a plurality of power level control devices 64, each power level control device 64 associated with a respective one of the heating elements 16. For example, wherein one or more of the heating elements 16 are configured as electric resistance heaters, the controller 52 may be operably connected to respective relays, triodes for alternating current (TRIACS), or other devices for controlling an amount of power to such electrical resistance heaters. Alternatively, in embodiments wherein one or more of the heating elements 16 are configured as induction heating elements, the controller 52 may be operably connected to respective current control devices.
In some exemplary embodiments, the power level as described herein may be a function of applied voltage and time. For example, in embodiments where the heating elements 16 are resistance heating elements, the resistance heating elements 16 may be operated over a duty cycle which includes a defined period of time, such as about thirty seconds. The total time period of the duty cycle may be allocated between an on duration and an off duration. Continuing the example, if the total duty cycle is thirty seconds long, the on duration may be twenty-seven seconds, where the off duration would then be three seconds, after which a subsequent duty cycle may be performed. Thus, the power level e.g., the average power supplied in a given duty cycle, is a function of applied voltage and time, e.g., the length of the on duration of the duty cycle. Accordingly, the average power supplied in a given duty cycle can be controlled by varying the magnitude of applied voltage and/or the proportion of the duty cycle in which the voltage is applied (e.g., the on duration). Thus, for example, operation of the cooktop appliance 12 may include a first cycle, such as a preheat cycle, wherein a first voltage is applied across the electric heating element 16 continuously throughout the first cycle. The first cycle may be followed by one or more subsequent cycles, e.g., a second cycle, a third cycle, etc. In some embodiments, the one or more subsequent cycles may include one or more duty cycles. In the one or more duty cycles, a voltage, e.g., the first voltage or a second voltage less than the first voltage, is applied across the electric heating element over a first period of time, e.g., an on duration, and the electric heating element 16 is deactivated for a second period of time, e.g., an off duration, and the first and second periods of time collectively define the duty cycle.
An exemplary resistance heating element 16 is illustrated in
In some exemplary embodiments, the power level control device 64 may include one or more relays configured to connect selected terminals of the heating element 16 to electrical conduits configured to operate at a desired voltage with respect to ground. One such example is illustrated in
As another example, only the first relay 63 may be provided in some embodiments. For example, as illustrated in
For example, operating the heating element 16 at the predetermined power level in response to the temperature setting may include applying the first voltage across the electric heating element 16, as illustrated at step 206 of method 200. In some embodiments, applying the first voltage across the electric heating element 16 may include connecting the first terminal 100 of the electric heating element 16 to the first electrical conduit 110 and connecting the second terminal 102 of the electric heating element 16 to the second electrical conduit 112.
As mentioned above, the method 200 may include monitoring a temperature with a temperature sensor, e.g., at step 208. The temperature may be monitored with one or both of the cookware temperature sensor 28 and the food temperature sensor 30, e.g., temperature values may be continuously measured by the temperature sensor(s) 28 and/or 30 over time during the operation of the cooktop appliance 12. Thus, it should be understood that “monitored,” “monitoring,” or other cognates thereof as used herein include continuous or repeated measuring or sampling of data, e.g., temperature, over a period of time. Further, in various embodiments, the temperature sensor used in the monitoring steps, e.g., step 208, may be one or both of the cookware temperature sensor 28 and the food temperature sensor 30, and the monitored temperature may be one or both of a temperature of cooking utensil 18 and a temperature of food item 32.
The method 200 may also include determining, at step 210, whether the monitored temperature is greater than or equal to the threshold temperature. When the monitored temperature is less than the threshold temperature, e.g., when the determination at step 210 is negative, the preheat cycle continues by returning to method step 206 and continuing to operate at the first power level, e.g., applying the first voltage. When the monitored temperature is greater than or equal to the threshold temperature, the method 200 may initiate a second cycle, e.g., a duty cycle at step 212.
For example, the controller 52 may perform step 212, e.g., the controller 52 may be configured to initiate a duty cycle of the cooktop appliance 12 when the monitored temperature reaches the threshold temperature. Performing the duty cycle may also include monitoring the temperature with the temperature sensor at step 214. In various embodiments, as generally shown in
As noted above, the duty cycle encompasses a time period including both an on duration and an off duration. The relative length of time in the on duration and the off duration affects the power level, e.g., the average power of the duty cycle. Moreover, one or both of the temperature sensors 28 and 30 may continuously supply a temperature reading to the controller 52 during the duty cycle such that the duty cycle may include monitoring the temperature with the temperature sensor(s) 28 and/or 30, e.g., at step 214. At various points in time throughout the duty cycle, the monitored temperature may vary above and below the temperature setting. The controller 52 may be configured for calculating a difference between the monitored temperature and the temperature setting, e.g., at step 216. The duty cycle may include operating the electric heating element 16 over a first period of time, e.g., the on duration. The adjustment of the power level may be based at least in part on the monitored temperature, e.g., may be based at least in part on the calculated difference between the monitored temperature and the temperature setting. For example, the difference between the monitored temperature and the temperature setting may be input into a control loop, which is generally a closed control loop, such as a proportional-integral-derivative (PID) control loop or a proportional-integral (PI) control loop, and the controller 52 may be configured for adjusting the power level of the heating element 16 based on the output of the control loop, e.g., by determining a duration of the first period of time based on the calculated difference between the monitored temperature and the temperature setting.
The on duration may be embodied by step 218 of applying a second voltage across the heating element 16 over a first period of time. Note that the heating element 16 is active and operating during the on duration, e.g., the second voltage applied at step 218 is a non-zero voltage. In various embodiments, a magnitude of the second voltage may be less than a magnitude of the first voltage. For example, applying the second voltage across the electric heating element 16 may include connecting the first terminal 100 of the electric heating element 16 to the neutral conduit 108 and connecting the second terminal 102 of the electric heating element 16 to the second electrical conduit 112. Accordingly, in some such embodiments, the first voltage may be two hundred forty volts with respect to ground and the second voltage may be one hundred twenty volts with respect to ground.
The duty cycle may also include an off duration, e.g., deactivating the heating element 16 for a second period of time, as shown at method step 220 in
As discussed above, the duty cycle includes the on duration and the off duration, such that adjusting one of the on duration and the off duration also necessarily adjusts the other of the on duration and the off duration by the same amount. For example, as noted above, the duty cycle may comprise thirty seconds, the on duration may comprise twenty-seven seconds, and the off duration may comprise three seconds. In such embodiments, if the difference between the monitored temperature and the temperature setting indicates the power level should be decreased, the on duration may be adjusted to twenty-four seconds, whereby the off duration would then be six seconds. Thus, in these embodiments, each duty cycle during operation of the cooktop appliance 12 includes monitoring a temperature (e.g., step 214), calculating a difference between the monitored temperature and a temperature setting (e.g., step 216), and determining the on and off durations of the present duty cycle (e.g. the first and second time periods in steps 218 and 220) based on the calculated difference.
In some example embodiments, the method 300 may include and/or the controller 52 may be configured for inputting the monitored temperature into a closed control loop, e.g., a PID control loop or a PI control loop, at step 310. In some embodiments, the method 300 may also include calculating a difference between the monitored temperature and the temperature setting, e.g., at step 308, and inputting the calculated difference as well as or instead of the monitored temperature into the control loop at step 310.
The method 300 may further include and/or the controller 52 may further be configured for operating the heating element 16 at a second power level based at least in part on an output of the control loop. For example, the second power level may be an average power of a second duty cycle subsequent to the first duty cycle described above. Accordingly, operating the electric heating element 16 at the first power level may comprise applying a first voltage across the electric heating element for a first duration, e.g., an on duration of the first duty cycle, and operating the electric heating element 16 at the second power level may comprise applying a second voltage across the electric heating element 16 for a second duration, e.g., an on duration of the second duty cycle. In some embodiments, the second voltage may be different from, e.g., less than, the first voltage. In various embodiments, the first duration and the second duration may be the same, or the first duration and the second duration may differ.
In some embodiments, the first power level may be a preheat power level. For example, the controller 52 may be configured for operating the electric heating element at the first power level until the monitored temperature reaches a threshold temperature, the threshold temperature less than the temperature setting, and inputting the monitored temperature into the closed control loop after the monitored temperature reaches the threshold temperature.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
