U.S. patent application number 15/927192 was filed with the patent office on 2019-09-26 for cooktop appliance.
The applicant listed for this patent is Haier US Appliance Solutions, Inc.. Invention is credited to James Lee Armstrong, Michael Blum.
Application Number | 20190293298 15/927192 |
Document ID | / |
Family ID | 67984944 |
Filed Date | 2019-09-26 |
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United States Patent
Application |
20190293298 |
Kind Code |
A1 |
Armstrong; James Lee ; et
al. |
September 26, 2019 |
COOKTOP APPLIANCE
Abstract
A cooktop appliance includes an electric heating element
positioned at a cooktop surface 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.
Inventors: |
Armstrong; James Lee;
(Louisville, KY) ; Blum; Michael; (Louisville,
KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Haier US Appliance Solutions, Inc. |
Wilmington |
DE |
US |
|
|
Family ID: |
67984944 |
Appl. No.: |
15/927192 |
Filed: |
March 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 1/0266 20130101;
F24C 7/046 20130101; F24C 7/087 20130101; H05B 2213/07 20130101;
H05B 6/062 20130101; F24C 7/082 20130101 |
International
Class: |
F24C 7/08 20060101
F24C007/08; F24C 7/04 20060101 F24C007/04 |
Claims
1. A cooktop appliance, comprising: 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 configured for: generating a temperature setting;
initiating a first cycle, the first cycle comprising 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 less than or equal to the temperature setting; and
performing a second cycle when the monitored temperature reaches
the threshold temperature, the second cycle comprising monitoring
the temperature with the temperature sensor, calculating a
difference between the monitored temperature and the temperature
setting, applying a second voltage across the electric heating
element over a first period of time, the second voltage less than
the first voltage, and deactivating the electric heating element
for a second period of time, wherein a duration of the first period
of time is based on the calculated difference between the monitored
temperature and the temperature setting.
2. The cooktop appliance of claim 1, further comprising a first
relay coupled to a first terminal of the electric heating element
and a second relay coupled to the second terminal of the electric
heating element, the first relay configured to selectively connect
the first terminal of the electric heating element to one of a
neutral electrical conduit and a first electrical conduit
configured to operate at a third voltage with respect to ground,
the second relay configured to selectively connect the second
terminal of the electric heating element to one of a second
electrical conduit configured to operate at a fourth voltage with
respect to ground, wherein applying the first voltage across the
electric heating element comprises connecting the first terminal of
the electric heating element to the first electrical conduit and
connecting the second terminal of the electric heating element to
the second electrical conduit, wherein applying the second voltage
across the electric heating element comprises connecting the first
terminal of the electric heating element to the neutral conduit and
connecting the second terminal of the electric heating element to
the second electrical conduit, and wherein deactivating the
electric heating element comprises connecting the second terminal
of the electric heating element to the open circuit.
3. The cooktop appliance of claim 1, further comprising a relay
coupled to a first terminal of the electric heating element, the
relay configured to selectively connect the first terminal of the
electric heating element to one of a neutral electrical conduit and
a first electrical conduit configured to operate at a third voltage
with respect to ground, and a second terminal of the electric
heating element connected to a second electrical conduit configured
to operate at a fourth voltage, wherein applying the first voltage
across the electric heating element comprises connecting the first
terminal of the electric heating element to the first electrical
conduit, and wherein applying the second voltage across the
electric heating element comprises connecting the first terminal of
the electric heating element to the neutral conduit.
4. The cooktop appliance of claim 3, wherein the relay is a first
relay, further comprising a second relay coupled to the second
terminal of the electric heating element, the second relay
configured to selectively connect the second terminal of the
electric heating element to one of the second electrical conduit
and an open circuit, and wherein deactivating the electric heating
element comprises connecting the second terminal of the electric
heating element to the open circuit.
5. The cooktop appliance of claim 1, wherein the monitored
temperature is a temperature associated with a cooking utensil
positioned on the electric heating element.
6. The cooktop appliance of claim 1, wherein the temperature sensor
is wirelessly connected to the controller.
7. The cooktop appliance of claim 1, further comprising a user
interface operatively connected to the controller, wherein the
controller is configured to generate the temperature setting in
response to a user input received via the user interface.
8. The cooktop appliance of claim 6, wherein the user interface
comprises a remote user interface on a remote user interface device
operatively connected to the controller via a wireless
connection.
9. The cooktop appliance of claim 1, wherein the electric heating
element is a resistance heating element.
10. The cooktop appliance of claim 1, wherein the controller is
further configured for performing a third cycle after the second
cycle, the third cycle comprising applying the first voltage across
the electric heating element.
11. A cooktop appliance, comprising: 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 configured for: generating a temperature setting;
operating the electric heating element at a first power level;
monitoring a temperature with a temperature sensor; inputting the
monitored temperature into a closed control loop; and operating the
electric heating element at a second power level based at least in
part on an output of the closed control loop.
12. The cooktop appliance of claim 11, wherein operating the
electric heating element at the first power level comprises
applying a first voltage across the electric heating element for a
first duration, and wherein operating the electric heating element
at the second power level comprises applying a second voltage
across the electric heating element for a second duration, the
second voltage less than the first voltage.
13. The cooktop appliance of claim 11, wherein the controller is
further 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 or equal
to the temperature setting, and inputting the monitored temperature
into the closed control loop after the monitored temperature
reaches the threshold temperature.
14. The cooktop appliance of claim 11, wherein the closed control
loop is a proportional-integral control loop.
15. The cooktop appliance of claim 11, wherein the closed control
loop is a proportional-integral-derivative control loop.
16. The cooktop appliance of claim 11, further comprising a user
interface operatively connected to the controller, wherein the
controller is configured for generating the temperature setting in
response to a user input received via the user interface.
17. The cooktop appliance of claim 16, wherein the user interface
comprises a remote user interface on a remote user interface device
operatively connected to the controller via a wireless
connection.
18. The cooktop appliance of claim 11, wherein the monitored
temperature is a temperature associated with a cooking utensil
positioned on the electric heating element.
19. The cooktop appliance of claim 11, wherein the temperature
sensor is wirelessly connected to the controller.
20. The cooktop appliance of claim 11 wherein the electric heating
element is a resistance heating element.
Description
FIELD
[0001] The present subject matter relates generally to cooktop
appliances, including cooktop appliances configured for precise
temperature control.
BACKGROUND
[0002] 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.
[0003] 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.
[0004] 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.
[0005] Accordingly, a cooktop appliance with features for improved
precision in temperature control would be useful.
BRIEF DESCRIPTION OF THE INVENTION
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] 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.
[0011] FIG. 1 provides a perspective view of a range having a
cooktop appliance according to one or more exemplary embodiments of
the present subject matter.
[0012] FIG. 2 provides a top, schematic view of the exemplary
cooktop appliance of FIG. 1.
[0013] FIG. 3 provides a schematic diagram of a control system as
may be used with the exemplary cooktop appliance of FIG. 2.
[0014] FIG. 4 provides a close up view of an exemplary heating
element according to one or more exemplary embodiments of the
present subject matter.
[0015] FIG. 5 provides a schematic wiring diagram for the heating
element of FIG. 4 in accordance with one or more exemplary
embodiments of the present disclosure.
[0016] FIG. 6 provides a schematic wiring diagram for the heating
element of FIG. 4 in accordance with one or more additional
exemplary embodiments of the present disclosure.
[0017] FIG. 7 provides a flowchart illustrating an exemplary
operation of a cooktop appliance according to one or more
embodiments of the present subject matter.
[0018] FIG. 8 provides a flowchart illustrating an exemplary
operation of a cooktop appliance according to one or more
embodiments of the present subject matter.
DETAILED DESCRIPTION
[0019] 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.
[0020] FIG. 1 provides a perspective view of a range appliance, or
range 10, including a cooktop appliance 12. Range 10 is provided by
way of example only and is not intended to limit the present
subject matter to the arrangement shown in FIG. 1. Thus, the
present subject matter may be used with other range 10 and/or
cooktop appliance 12 configurations, e.g., double oven range
appliances, standalone cooktop appliances, cooktop appliances
without an oven, etc.
[0021] 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.
[0022] As shown in FIG. 1, a cooking utensil 18, such as a pot,
pan, or the like, may be placed on a heating element 16 to heat the
cooking utensil 18 and cook or heat food items placed in cooking
utensil 18. Range appliance 10 also includes a door 20 that permits
access to a cooking chamber (not shown) of range appliance 10,
e.g., for cooking or baking of food items therein. A control panel
22 having controls 24 permits a user to make selections for cooking
of food items. Although shown on a backsplash or back panel 26 of
range appliance 10, control panel 22 may be positioned in any
suitable location. Controls 24 may include buttons, knobs, and the
like, as well as combinations thereof. As an example, a user may
manipulate one or more controls 24 to select a temperature and/or a
heat or power output for each heating element 16. The selected
temperature or heat output of heating element 16 affects the heat
transferred to cooking utensil 18 placed on heating element 16.
[0023] As will be discussed in greater detail below, the cooktop
appliance 12 includes a control system 50 (FIG. 3) for controlling
one or more of the plurality of heating elements 16. Specifically,
the control system 50 may include a controller 52 (FIG. 3) operably
connected to the control panel 22 and controls 24. The controller
52 may be 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
received through the control panel 22 and controls 24.
[0024] Referring now to FIG. 2, a top, schematic view of the
cooktop appliance 12 of FIG. 1, or more specifically of the cooking
surface 14 of the cooktop appliance 12 of FIG. 1, is provided. As
stated, the cooking surface 14 of the cooktop appliance 12 for the
embodiment depicted includes five heating elements 16 spaced along
the cooking surface 14. A cooking utensil 18, also depicted
schematically, is positioned on a first heating element 16 of the
plurality of heating elements 16. For the embodiment depicted, a
cookware temperature sensor 28 and a food temperature sensor 30 are
also associated with the cooking utensil 18.
[0025] 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 FIG. 3.
Alternatively, however, the cookware temperature sensor 28 may be
attached to or integrated within the cooking surface 14 of the
cooktop appliance 12. For example, the cookware temperature sensor
28 may be integrated into one or more of the heating elements 16,
as illustrated in FIG. 4. With such an exemplary embodiment, the
cookware temperature sensor 28 may be configured to physically
contact the bottom surface of a bottom wall of the cooking utensil
18 when the cooking utensil 18 is placed on the heating element 16
of the cooking surface 14. Alternatively, cookware temperature
sensor 28 may be positioned proximate to the bottom surface or
bottom wall of the cooking utensil 18 when the cooking utensil 18
is placed on the heating element 16 of the cooking surface 14.
[0026] 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 FIG. 3) positioned within the cooking
utensil 18. For example, the food temperature sensor 30 may be a
probe type temperature sensor configured to be inserted into one or
more food items 32. Alternatively, however, the food temperature
sensor 30 may be configured to determine a temperature of one or
more food items positioned within the cooking utensil 18 in any
other suitable manner.
[0027] 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.
[0028] Referring again to FIG. 2, the cooktop appliance 12
additionally includes at least one receiver 34. In the illustrated
example of FIG. 2, the cooktop appliance 12 includes a plurality of
receivers 34, each receiver 34 associated with an individual
heating element 16. Each receiver 34 is configured to receive a
signal from the food temperature sensor 30 indicative of a
temperature of the one or more food items 32 positioned within the
cooking utensil 18 and from the cookware temperature sensor 28
indicative of a temperature of the cooking utensil 18 positioned on
a respective heating element 16. In other embodiments, a single
receiver 34 may be provided and the single receiver 34 may be
operatively connected to one or more than one of the sensors. In at
least some exemplary embodiments, one or both of the cookware
temperature sensor 28 and the food temperature sensor 30 may
include wireless transmitting capabilities, or alternatively may be
hard-wired to the receiver 34 through a wired communications
bus.
[0029] Referring now also to FIG. 3, a schematic view of a system
for operating a cooktop appliance 12 in accordance with an
exemplary embodiment of the present disclosure is provided.
Specifically, FIG. 3 provides a schematic view of a heating element
16 of the exemplary cooktop appliance 12 of FIGS. 1 and 2 and an
exemplary control system 50.
[0030] 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.
[0031] Referring still to FIG. 3, each receiver 34 associated with
a respective heating element 16 is operably connected to a
controller 52 of the control system 50. The receivers 34 may be
operably connected to the controller 52 via a wired communication
bus (as shown), or alternatively through a wireless communication
network similar to the exemplary wireless communication network 54
discussed above. The controller 52 may generally include a
computing device 56 having one or more processor(s) 58 and
associated memory device(s) 60. The computing device 56 may be
configured to perform a variety of computer-implemented functions
to control the exemplary cooktop appliance 12. The computing device
56 can include a general purpose computer or a special purpose
computer, or any other suitable computing device. It should be
appreciated, that as used herein, the processor 58 may refer to a
controller, a microcontroller, a microcomputer, a programmable
logic controller (PLC), an application specific integrated circuit,
and other programmable circuits. Additionally, the memory device(s)
60 may generally comprise memory element(s) including, but not
limited to, computer readable medium (e.g., random access memory
(RAM)), computer readable non-volatile medium (e.g., a flash
memory), a compact disc-read only memory (CD-ROM), a
magneto-optical disk (MOD), a digital versatile disc (DVD), and/or
other suitable memory elements. The memory 60 can store information
accessible by processor(s) 58, including instructions that can be
executed by processor(s) 58. For example, the instructions can be
software or any set of instructions that when executed by the
processor(s) 58, cause the processor(s) 58 to perform operations.
For the embodiment depicted, the instructions may include a
software package configured to operate the system to, e.g., execute
the exemplary methods described below.
[0032] Referring still to FIG. 3, the control system 50
additionally includes a user interface 62 operably connected to the
controller 52. For the embodiment depicted, e.g., in FIG. 3, the
user interface 62 is configured in wired communication with the
controller 52. However, in other exemplary embodiments, e.g., as
shown in FIG. 2, the user interface 62 may additionally or
alternatively be wirelessly connected to the controller 52 via one
or more suitable wireless communication networks (such as the
exemplary wireless communication network 54 described above). In
certain exemplary embodiments, user interface 62 may be configured
as the control panel 22 and plurality of controls 24 on the cooktop
appliance 12 (see FIG. 1). Additionally, or alternatively, the user
interface 62 may be configured as an external computing device or
remote user interface device, such as a smart phone, tablet, or
other device capable of connecting to the controller 52 of the
exemplary control system 50. For example, in some embodiments, the
remote user interface may be an application or "app" executed by a
remote user interface device such as a smart phone or tablet.
Signals generated in controller 52 operate appliance 12 in response
to user input via the user interface 62.
[0033] 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.
[0034] 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.
[0035] An exemplary resistance heating element 16 is illustrated in
FIG. 4. In the illustrated example embodiment, the heating element
16 comprises a temperature limiter 122 and a plurality of
terminals. In particular, the exemplary heating element 16
illustrated in FIG. 4 includes a first terminal 100, a second
terminal 102, a third terminal 104, and a fourth terminal 106. As
shown, the exemplary heating element 16 includes three rings, e.g.,
a first ring 116 corresponding to the second terminal 102, a second
ring 118 corresponding to the third terminal 104, and a third ring
120 corresponding to the fourth terminal 106. A voltage may be
applied across all or a selected one or more of the rings 116, 118,
and 120 by connecting a voltage source across the first terminal
100 and one of the second terminal 102, third terminal 104, and
fourth terminal 106.
[0036] 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 FIG. 5, where the power level
control is provided by a first relay 63 and a second relay 65. That
is, in the illustrated exemplary embodiment, the power level, e.g.
the average power supplied during a duty cycle, may be controlled
at least by operating the heating element at a variable voltage
using the relays 63 and 65, as described in more detail herein. As
illustrated, the first relay 63 is coupled to the first terminal
100 of the electric heating element 16 and configured to
selectively connect the first terminal 100 of the electric heating
element 16 to one of a neutral electrical conduit 108 and a first
electrical conduit 110 configured to operate at a third voltage
with respect to ground. Thus, first electrical conduit 110 may be
coupled or connected to a first voltage source operating at the
first voltage with respect to ground. Also as shown in FIG. 5, the
second relay 65 is coupled to the second terminal 102 of the
electric heating element 16. In the particular exemplary embodiment
illustrated by FIG. 5, the second relay 65 is also connected to the
third terminal 104 and fourth terminal 106. In other embodiments,
the heating element 16 may include only the first and second
terminals 100 and 102. In still further embodiments where the
heating element 16 comprises a plurality of rings, e.g., the first,
second, and third rings 116, 118, and 120 as in the illustrated
exemplary embodiment, and a corresponding number of terminals, each
terminal may be connected to a dedicated relay with each dedicated
relay only connected to a single terminal and no other terminals.
For example, a third relay may be provided connected to the third
terminal 104 and a fourth relay may be provided connected to the
fourth terminal 106, etc. The second relay is configured to
selectively connect the second terminal 102 of the electric heating
element 16 to one of a second electrical conduit 112 configured to
operate at a fourth voltage with respect to ground, and an open
circuit 114. The second electrical conduit 112 may be coupled or
connected to a second voltage source operating at the second
voltage with respect to ground. Neutral electrical conduit 108 is
configured for operating at neutral. Thus, neutral electrical
conduit 108 may be grounded. The first, second and neutral
electrical conduits 108, 110, and 112 may be any suitable
electrical conduits, such as wires, cables, etc. In the illustrated
example embodiment, the second relay is also configured to
selectively connect one or both of the third terminal 104 and
fourth terminal 106 to one of the second electrical conduit 112 and
the open circuit 114.
[0037] As another example, only the first relay 63 may be provided
in some embodiments. For example, as illustrated in FIG. 6, the
relay 63 may be a three-way relay that switches between off, the
first voltage and the second voltage. In such embodiments, the
relay 63 may be configured to connect a selected one of the neutral
electrical conduit 108, the second electrical conduit 112, and the
open circuit 114 to one or more of the second terminal 102, the
third terminal 104, and the fourth terminal 106. In such
embodiments, the first terminal 100 may be connected to the first
electrical conduit 110 without an intervening switch or relay. The
first voltage and the second voltage may have opposite polarities.
In addition, a magnitude of the first voltage with respect to
ground may be about equal to a magnitude of the second voltage with
respect to ground. As used herein, the term "about" corresponds to
within ten volts of a stated voltage when used in the context of
voltage. As an example, the magnitude of the first and second
voltages may be about one hundred and twenty volts with respect to
ground. Thus, e.g., first electrical conduit 110 may be coupled to
one phase of a two hundred and forty volt household electrical
supply, and second electrical conduit 112 may be coupled to the
second phase of the two hundred and forty volt household electrical
supply. Neutral electrical conduit 108 may be grounded.
[0038] FIG. 7 illustrates an exemplary method 200 of operating a
cooktop appliance, such as the exemplary cooktop 12. In some
embodiments, the controller 52 may be configured to perform some or
all of the steps of method 200. The method 200 may include a step
202 of generating or receiving a temperature setting. For example,
the cooktop appliance 12 and/or a controller 52 thereof may be
configured to generate a temperature setting, e.g., the temperature
setting may be generated by the controller 52 in response to a user
input received via the user interface 62 (FIG. 3). The controller
52 may be further configured for initiating the first cycle, e.g.,
preheat cycle, e.g., at step 204 of the exemplary method 200. The
preheat cycle may include operating a heating element 16 at a
predetermined power level corresponding to the temperature setting
and monitoring a temperature with temperature sensor 30 until the
monitored temperature reaches a threshold temperature. In some
embodiments, the threshold temperature may be less than the
temperature setting. For example, the threshold temperature may be
a predetermined percentage of the temperature setting, such as
about ninety-five percent (95%) or less, such as about ninety
percent (90%) or less, such as about eighty percent (80%) or less,
such as about seventy-five percent (75%) or less. Providing the
threshold temperature less than the temperature setting accounts
for thermal lag, e.g., a decrease in the rate of temperature
increase will lag behind a decrease in the supplied power level,
such that the threshold temperature less than the temperature
setting may reduce or avoid overshooting the temperature setting at
the end of the preheat cycle.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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 FIG. 7, the duty
cycle may include adjusting a power level of the heating element 16
based at least in part on the monitored temperature. As noted above
and discussed in more detail below, the power level may be a
function of the voltage applied and the length of the on duration
in the duty cycle. As such, adjusting one or both of the applied
voltage and the length of the on duration and off duration may
adjust the power level.
[0043] 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.
[0044] 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.
[0045] 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 FIG. 7. In some embodiments,
deactivating the electric heating element 16 may include connecting
the second terminal 102 of the electric heating element 16 to the
open circuit 114. One of ordinary skill will recognize that the
heating element 16 is not operating during the off duration. The
controller 52 may be configured for deactivating the heating
element 16 for the second period of time based at least in part on
the monitored temperature, e.g., based at least in part on the
calculated difference between the monitored temperature and the
temperature setting. For example, when the monitored temperature is
greater than the temperature setting, the controller 52 may
deactivate the heating element 16 for the second period of time,
e.g., a length of an off duration, based on the magnitude of the
difference between the monitored temperature and the temperature
setting. Following the off duration, the controller 52 may initiate
a subsequent duty cycle, e.g., as shown in FIG. 6, the method may
return to step 214 after step 220.
[0046] 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.
[0047] FIG. 8 provides an illustrative flow chart of an example
method 300 of operating a cooktop appliance. It should be
understood that the control system 50 and/or controller 52
described hereinabove may be configured for performing some or all
of the steps of the exemplary method 300. As shown in FIG. 8, the
method 300 may include generating a temperature setting at step
302, e.g., in response to a user input received via a user
interface. The method 300 may also include a step 304 of operating
the heating element 16 at a first power level. As discussed above,
the first power level may be an average power of a first duty
cycle, which may be determined by a voltage applied during an on
duration of the first duty cycle and a time length of the on
duration. The method 300 may also include a step 306 of monitoring
a temperature, e.g., of cooking utensil 18 and/or food item 32,
with a temperature sensor, e.g., one or both of the cookware
temperature sensor 28 and the food temperature sensor 30.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
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