U.S. patent application number 10/700339 was filed with the patent office on 2004-10-21 for system, apparatus and method for controlling ignition including re-ignition of gas and gas fired appliances using same.
Invention is credited to Chodacki, Thomas A., Ralson, James M., Solofra, Kevin C..
Application Number | 20040209209 10/700339 |
Document ID | / |
Family ID | 32314489 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040209209 |
Kind Code |
A1 |
Chodacki, Thomas A. ; et
al. |
October 21, 2004 |
System, apparatus and method for controlling ignition including
re-ignition of gas and gas fired appliances using same
Abstract
Featured is a gas control device being configured and arranged
so as to control operation of a hot surface igniter so it is
warmed-up to ignition temperatures of a gas when a call for heat is
made and, following ignition, to control operation of the igniter
so it is capable of rapidly re-igniting the gas without having to
continuously maintain the igniter at or above gas ignition
temperatures. More particularly, the gas control device includes
circuitry that controls energization of the igniter for ignition of
the gas and, after ignition of the gas is determined to have
occurred, controls energization of the igniter so that the igniter
can be warmed up to ignition temperature conditions within desired
re-ignition time periods. Also featured are systems and apparatuses
embodying such control devices as well as methods related
thereto.
Inventors: |
Chodacki, Thomas A.; (Stow,
MA) ; Solofra, Kevin C.; (Weare, NH) ; Ralson,
James M.; (Naperville, IL) |
Correspondence
Address: |
EDWARDS & ANGELL, LLP
P.O. Box 9169
Boston
MA
02209
US
|
Family ID: |
32314489 |
Appl. No.: |
10/700339 |
Filed: |
November 3, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60423509 |
Nov 4, 2002 |
|
|
|
Current U.S.
Class: |
431/66 |
Current CPC
Class: |
F23N 2223/08 20200101;
F23Q 7/12 20130101; F23N 2227/02 20200101; F23N 2237/02 20200101;
F23N 1/002 20130101; F23N 2227/38 20200101; F23N 2227/42
20200101 |
Class at
Publication: |
431/066 |
International
Class: |
F23N 005/00 |
Claims
What is claimed is:
1. A gas control system that controls energizing an electric
resistance igniter from a power source, said control system
comprising: a control device being configured and arranged so as to
control operation of the electric resistance igniter; wherein the
control device is configured and arranged so as to warm-up the
electric resistance igniter to temperature at or above an ignition
temperature for a gas being combusted; and wherein the control
device also is configured and arranged so that following successful
ignition of the gas, operation of the electric resistance igniter
is controlled so the electric resistance igniter is at a
temperature less than the gas ignition temperature and so the
electric resistance igniter can be re-heated so as to re-ignite the
gas within a desired re-ignition time period.
2. The gas control system of claim 1, wherein the gas control
system further controls operation of one or more gas control
valves, which valves control the flow of gas for combustion, and
wherein the control device is configured and arranged so as to open
the one or more gas valves after the control device determines that
the electric resistance igniter is heated to a temperature at least
equal to the gas ignition temperature.
3. The gas control system of claim 1, wherein the control device is
configured and arranged so as to selectively control energization
of the electric resistance igniter following successful ignition of
the gas, where the electric resistance heater is selectively
energized so that the electric resistance igniter is maintained at
a temperature that is less than gas ignition temperature and which
is established such that a time required to reheat the electric
resistance igniter from the temperature less than the gas ignition
temperature to a minimum temperature required for ignition of the
gas, is less than a desired time period for re-ignition.
4. The gas control system of claim 3, wherein the control device
includes: a switching mechanism operably connected between the
electric resistance igniter and the power source; a
micro-controller and an applications program for execution in the
micro-controller; and wherein the applications program includes
instructions and criteria for outputting control signals to the
switching mechanism to selectively control voltage being applied to
the electric resistance igniter, outputting control signals to the
switching mechanism to heat the electric resistance igniter to the
gas ignition temperature, and outputting control signals to the
switching mechanism, following successful ignition of the gas, to
maintain the electric resistance igniter at a temperature less than
the gas ignition temperature.
5. The gas control system of claim 4, wherein the applications
program further includes instructions and criteria for: heating the
electric resistance igniter to the temperature that is set so that
a time required to reheat the electric resistance igniter from the
temperature that is set to a minimum temperature required for
ignition of the gas, is within than a desired time period for
re-ignition.
6. A gas control system that controls energizing an electric
resistance igniter from a power source and that controls operation
of one or more gas control valves, which valves control the flow of
gas for combustion, said gas control system comprising: a control
device being operably coupled between the electric resistance
igniter and the power source and being operably connected to the
one or more gas valves; wherein the control device is configured
and arranged to selectively apply a voltage to the electric
resistance igniter responsive to an input signal calling for heat;
and wherein the control device is configured and arranged: so the
electric resistance igniter is heated by the selectively applied
voltage so as to be at a temperature at or above a temperature for
igniting the gas, a gas ignition temperature, such that upon
determining that the electric resistance igniter has been heated to
the gas ignition temperature, the one or more gas valves are
opened, and such that upon determining that the gas has been
successfully ignited, the voltage being applied to the electric
resistance igniter is controlled so as to maintain the electric
resistance igniter at an operational temperature that is less than
the gas ignition temperature.
7. The gas control device of claim 6, wherein the control device is
configured and arranged so the voltage being applied to the
electric resistance igniter after determining that the gas has been
successfully ignited is controlled so that the electric resistance
igniter is at a temperature set so that a time required to reheat
the electric resistance igniter from that temperature to a minimum
temperature required for ignition of the gas, is within than a
desired time period for re-ignition.
8. An ignition system comprising: a control device that can control
operation of an electric resistance igniter; wherein the control
device is configured to (i) heat the igniter to temperature at or
above an ignition temperature for a gas being combusted; and (ii)
following successful ignition of the gas, to control operation of
the igniter so the igniter is at a temperature less than the gas
ignition temperature and so the electric resistance igniter can be
re-heated so as to re-ignite the gas within a desired re-ignition
time period.
9. The ignition system of claim 8 wherein an electrical resistance
igniter is operably connected to the control device.
10. The ignition system of claim 9 wherein the electrical
resistance igniter is in electrical communication with the control
device.
11. The ignition system of claim 8 wherein the igniter is a
sintered ceramic igniter.
12. The ignition system of claim 8 wherein following gas ignition,
the igniter is maintained at a temperature less than the gas
ignition temperature but greater than ambient temperature.
13. The ignition system of claim 8 wherein the desired re-ignition
time period is about four seconds or less.
Description
[0001] The present application claims the benefit of U.S.
provisional application No. 60/423,509 filed Nov. 4, 2003, which is
incorporated herein by reference in its entirety.
1. FIELD OF INVENTION
[0002] The present invention generally relates to systems and
methods for controlling ignition of gas, more particularly to a
systems and methods for controlling ignition including re-ignition
of gas when using electrical resistance igniters, even more
particularly to systems and methods for controlling ignition of gas
for gas fired appliances and water heaters and more specifically to
such systems and methods that utilize
microprocessors/micro-controllers for performing such control
functionalities.
2. BACKGROUND OF THE INVENTION
[0003] There are a number of appliances such as cooking ranges and
clothes dryers and water heaters in which a combustible material,
such as a combustible hydrocarbon (e.g., propane, natural gas) is
mixed with air (i.e., oxygen) and continuously combusted within the
appliance or water heater so as to provide a continuous source of
heat energy. This continuous source of heat energy is used for
example to cook food, dry clothes and heat water to supply a source
of running hot water.
[0004] Because this mixture of fuel and air (i.e., fuel/air
mixture) does not self-ignite when mixed together, an ignition
source must be provided to initiate the combustion process and to
continue operating until the combustion process is self-sustaining.
In the not too distant past, the ignition source was what was
commonly referred to as a pilot light in which a very small
quantity of the combustible material and air was mixed and
continuously combusted even while the heating apparatus or
appliance was not in operation. For a number of reasons, the use of
a pilot light as an ignition source was done away with and an
igniter used instead.
[0005] An igniter is a device that creates the conditions required
for ignition of the fuel/air mixture on demand, including
spark-type igniters such as piezoelectric igniters and hot
surface-type igniters such as silicon carbide hot surface igniters.
Spark-type igniters that produce an electrical spark that ignites
gas, advantageously provide very rapid ignition, which is to say,
ignition within a few seconds. Problems with spark-type igniters,
however, include among other things the electronic and physical
noise produced by the spark.
[0006] With hot surface igniters, such as the silicon carbide hot
surface igniter, the heating tip or element is resistively heated
by electricity to the temperature required for the ignition of the
fuel/air mixture, thus when the fuel/air mixture flows proximal to
the igniter it is ignited. This process is repeated as and when
needed to meet the particular operating requirements for the
heating apparatus/appliance. Hot-surface-type igniters are
advantageous in that they produce negligible noise in comparison to
spark-type igniters. Hot surface-type igniters, however, can
require significant ignition/warm-up time to resistively heat the
resistance igniter sufficiently to a temperature that will ignite
the gas.
[0007] There are several manufacturers of hot surface igniters used
and an igniter from any one manufacturer, because of its particular
material composition, mass, and physical configuration, will
generally heat up at a different rate to a different final
temperature than an igniter from another manufacturer. For example,
when energized at 115 volts, igniters from one manufacturer may
heat up to a temperature sufficient to ignite gas, approximately
1600.degree. F., in approximately 5 seconds, and to a relatively
stable final temperature of approximately 2500.degree. F. when
energized for 20 seconds or longer. An igniter from another
manufacturer may require more or less time to heat up to
1600.degree. F. and may attain a lower or higher final temperature.
The rate of temperature change and the final temperature attained
also depends on the value of the applied voltage. Specifically,
when the nominal applied voltage is lower, the igniter heats up
slower and attains a lower final temperature than when energized at
higher voltage; when the applied nominal voltage is relatively
greater, the igniter heats up faster and attains a higher final
temperature.
[0008] Hot surface ignition systems include a control module that,
among other functions, establishes the length of the igniter
warm-up time period. When it is known that a particular igniter
having a fast warm-up time will be used, the length of the igniter
warm-up time period can be established at a relatively low value,
for example, at 15 seconds. However, when the particular igniter to
be used has a slow warm-up time or it is desirable that the system
is to be usable with either fast or slow warm-up time igniters, the
length of the igniter warm-up time period is established at a
relatively large value, for example, at 45 seconds.
[0009] With regard to system operation, the 15-45-second igniter
warm-up time period usually presents no particular problem because
it represents the period between a call for heat and the time
needed to enable the igniter to attain gas ignition temperature.
From the standpoint of cooking, drying clothes and heating water
such delays are expected and generally not noticeable to the user.
For example, the delay in ignition of an oven is significantly less
than the time to pre-heat the oven for baking or to reach broiling
conditions. Thus, to the typical user the 15-45 second delay for
gas ignition does not noticeably increase the preheating time or
the time to reach broiling conditions. Such igniter warm-up time
periods are, however, a disadvantage from the standpoint of
re-ignition of the gas during a combustion/heating process, which
gas re-ignition times by established industry standards are on the
order of 4 seconds or less.
[0010] One conventional oven gas burner control system that
includes re-ignition capability uses a bimetallic valve control
system, where the valve remains open, so the gas can flow through
for combustion, as long as the bimetallic element is subject to
heat energy above a predetermined amount. In order to keep the
valve open in these types of systems the igniter must remain on
(i.e., remain heated at or above the ignition temperature)
throughout the entire period of burner operation so as to provide
the required heat energy to the bimetallic valve. In addition for
ovens with self-cleaning capability, the igniter remains heated at
or above the gas ignition temperature, during that portion of the
cleaning cycle where the oven is heated to elevated temperatures to
remove and/or convert (e.g., to ash) residue (e.g., spills,
drippings, etc.) on the interior surfaces of the oven. This
maintenance of the igniter at or above the gas ignition temperature
during the entire cooking/heating or cleaning cycle necessarily
reduces the effective service life of the igniter.
[0011] There is found in U.S. Pat. No. 4,615,282 a control module
in a hot surface ignition system that includes a microcomputer
programmed to provide a pre-selected igniter warm-up time period
for enabling an igniter to heat up to a gas ignition temperature
during normal system operation (e.g., 15 or 45 seconds) and is
further programmed to provide, for test purposes only, an
accelerated igniter warm-up time period (e.g., 10 seconds) that is
shorter than the pre-selected igniter warm-up time period but
sufficiently long for enabling the igniter to heat up to a
temperature sufficiently high to ignite gas. The program for
providing the accelerated igniter warm-up time period is
automatically executed responsive to a unique signal from a
detachably connected test device to the control module. It is
further provided that this signal is unique and cannot be generated
by the system itself under normal or abnormal conditions.
[0012] It thus would be desirable to provide a new system,
apparatus and/or device to control the operation of the igniter so
the igniter is capable of re-igniting the gas within desired time
periods without having to maintain the igniter in a continuous "on"
state and methods for controlling igniter energization/operation.
It also would be desirable to provide such a control system and
method where the igniter is warmed-up to the ignition temperature
for igniting the gas and thereafter the operation of the igniter is
controlled so as to maintain the igniter in a state for rapid
re-ignition of the gas. It would be particularly desirable to
provide such a device and method that would control igniter
energization so as to extend the operational life of the igniter in
comparison to the operational life for igniters being controlled by
prior art control devices. Such gas control systems, apparatuses
and devices preferably would be simple in construction as compared
to prior art systems, apparatuses or control devices and such
methods would not require highly skilled users to utilize the
device.
SUMMARY OF THE INVENTION
[0013] The present invention features a gas control device being
configured and arranged so as to control operation of a hot surface
igniter so that such igniter is warmed-up to temperatures at or
above the ignition temperature of a gas when a call for heat is
made. Such a gas control device also is configured and arranged so
that following such ignition operation, the igniter is controlled
so the igniter is capable of rapidly re-igniting the gas (i.e.,
re-igniting the gas within desired re-ignition time period) without
having to continuously maintain the igniter at or above the gas
ignition temperature as is done with conventional gas control
circuitry. More particularly, the gas control device includes
circuitry that controls energization of the igniter for ignition of
the gas and, after ignition of the gas is determined to have
occurred, controls energization of the igniter so that the igniter
can be warmed up to ignition temperature conditions within desired
re-ignition time periods. Also featured are systems and apparatuses
embodying such control devices as well as methods related
thereto.
[0014] There also is featured a gas control system that controls
energizing an electric resistance igniter from a power source and
includes a control device being configured and arranged so as to
control operation of the electric resistance igniter. More
particularly, the control device is configured and arranged to
warm-up the electric resistance igniter to temperature at or above
an ignition temperature for a gas being combusted. Further, the
control device is configured and arranged so that following
successful ignition of the gas, operation of the electric
resistance igniter is controlled so the electric resistance igniter
is at a temperature less than the gas ignition temperature and so
the electric resistance igniter can be re-heated so as to re-ignite
the gas within a desired re-ignition time period.
[0015] In more specific embodiments, the gas control system further
controls operation of one or more gas control valves, which valves
control the flow of gas for combustion. In addition, the control
device is configured and arranged so as to open the one or more gas
valves after the control device determines that the electric
resistance igniter is heated to a temperature at least equal to the
gas ignition temperature.
[0016] Other aspects and embodiments of the invention are discussed
below.
Definitions
[0017] The instant invention is most clearly understood with
reference to the following definitions:
[0018] The term gas shall be understood to mean any gaseous
combustible material as is known to those skilled in the art used
in connection with gas-fired appliances, such as those used for
cooking of food and drying of clothes (e.g., stoves, ovens, clothes
dryers) and water heaters and further includes, but is not limited
to propane, natural gas, city gas, and manufactured gas.
BRIEF DESCRIPTION OF THE DRAWING
[0019] For a fuller understanding of the nature and desired objects
of the present invention, reference is made to the following
detailed description taken in conjunction with the accompanying
drawing figures wherein like reference character denote
corresponding parts throughout the several views and wherein:
[0020] FIG. 1 is a schematic block diagram of a gas-fired appliance
including a gas control system according to the present invention
illustrating control of a gas burner;
[0021] FIG. 2 is a schematic block diagram of a gas-fired appliance
including a gas control system according to the present invention
illustrating control of a plurality of gas burners;
[0022] FIGS. 3A-D illustrate a flow diagram of a control
methodology according to the present invention;
[0023] FIG. 4 is a schematic block diagram of a gas-fired appliance
including an exemplary igniter control circuitry for a gas control
system according to an embodiment of the present invention; and
[0024] FIG. 5 is a flow diagram illustrating the energizing process
for an igniter being controlled by the igniter control circuitry of
FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0025] As discussed above, we now provide an ignition system that
comprises a control device that can control operation of an
electric resistance igniter, such as a sintered electrical igniter.
Exemplary preferred igniters to use in an ignition system of the
invention include sintered ceramic igniters such as those igniters
disclosed e.g. U.S. Pat. Nos. 6,852,629; 6,474,492; and 5,801,361,
among others.
[0026] The control device is suitably configured to (i) heat the
igniter to temperature at or above an ignition temperature for a
gas being combusted, and (ii) following successful ignition of the
gas, to control operation of the igniter so the igniter is at a
temperature less than the gas ignition temperature and so the
electric resistance igniter can be re-heated so as to re-ignite the
gas within a desired re-ignition time period. Preferably, the
temperature of the igniter is maintained at desired levels (e.g. at
ignition temperature or below ignition temperature) by monitoring
amperage. Preferably, the system suitably may only switch on gas
flow when a predetermined current level is attained to the
igniter.
[0027] Suitably, the control device can operate so that the
electrical resistance igniter is maintained at a temperature of
about 100.degree. C. or more, such as 200.degree. C., 300.degree.
C., 400.degree. C., 500.degree. C., 600.degree. C. or 1000.degree.
C. or more less than a targeted gas ignition temperature (e.g. a
targeted gas ignition temperature may be about 1100.degree. C.,
1200.degree. C., 1300.degree. C. or 1400.degree. C., such as
1100.degree. C. to 1400.degree. C.). The electrical resistance
igniter also suitably may be maintained at a non-elevated
temperature (i.e. maintained at ambient temperature) during
non-ignition periods. For many applications, however, it will be
preferred that the igniter is maintained at some temperature above
room or ambient temperature, but below ignition temperature (e.g.
below about 1200.degree. C., 1150.degree. C. or 1100.degree. C.)
during periods where ignition is not needed or desired.
[0028] Preferably, an ignition system of the invention provides
rapid ignition to gaseous fuel, e.g. where ignition occurs within
about 6 seconds or less after activation of the system for ignition
(i.e. re-ignition time period), more preferably within about 5, 4,
3 or even 2 seconds after activation of the system for
ignition.
[0029] Referring now to the various figures of the drawing wherein
like reference characters refer to like parts, there is shown in
FIG. 1 a schematic block diagram of a gas-fired water heater or
gas-fired appliance 10 such as a gas range or oven including a gas
control system 100 according to the present invention. The
gas-fired appliance 10 also includes, a control mechanism 12, a
master or main gas valve 32, a burner or gas control valve 34, gas
supply tubing 36, a burner 38, a flamer sensing mechanism 50 and an
igniter 60. The electrical power for operating components of the
gas-fired appliance is from a power supply 20 and the gas being
combusted within the gas-fired appliance is from a gas source 30.
In exemplary illustrative embodiments the gas source 30 is a gas
supply line within a household, which gas line typically includes a
manual shut-off valve and is interconnected to a gas supply line(s)
of a gas utility. Also, the electrical power source 20 is the main
electrical panel within a household that is electrically coupled
via a breaker to the electrical lines of an electric utility.
[0030] It should be recognized that the electrical voltage or line
voltage being supplied is dependent upon the location in the world
as well as the operational range or variation permitted. In the
United States where the specified line voltage is 220 VAC, the
nominal line voltage typically ranges between about 208 VAC and
about 240 VAC. In Europe and other parts of the world where the
specified line voltage is 230 VAC, the nominal line voltage
typically ranges between about 220 VAC and about 240VAC. Thus, line
voltage variance universally can range anywhere between about 176
VAC and about 264 VAC. In the United States, there are cases where
other nominal line voltages are found; in one case the nominal line
voltage is 120VAC, which ranges between about 102 VAC and about 132
VAC and in another case the nominal line voltage is 24VAC, which
ranges between about 20 VAC and about 26 VAC.
[0031] The control mechanism 12 is any of a number of mechanisms or
switches known in the art that can provide output signals to the
micro-controller 110, responsive to user inputs/actions, so as to
selectively turn the gas burner 38 on and off as well as
selectively adjusting the heat-output of the gas burner. In an
exemplary illustrative embodiment, the control mechanism 12 is a
rotating switch as is known to those skilled in the art that is
selectively rotated by a user to thereby provide the necessary
signal outputs. In an alternative embodiment, the control mechanism
12 is one or more pressure sensitive switches used to turn the gas
burner 38 on and off and for selecting a power level (e.g., a
temperature). The pressure sensitive switch can be used in
combination with an LCD or other type of visual display that
displays the on-off condition and power level information to the
user.
[0032] In the illustrated embodiment, there is shown a redundant
gas valve sub-system comprised of a main valve 32 and a gas control
valve 34, however, this shall not be construed as being limiting
the present invention to the illustrative embodiment. The gas
control device 100 of the present invention is contemplated for,
and adaptable for, use with gas-fired appliances having a single
gas control valve between the gas source 30 and the gas burner 38.
The gas supply tubing 36 is any of a number of tubing products
known to those skilled in the art that are appropriate for use with
gas and appropriate for interconnecting the main valve 32, the gas
control valve 34 of the gas-fired appliance to the gas source 30
and in turn to the gas burner 38.
[0033] The main valve 32 is any of a number of valves known to
those skilled in the art, such as a solenoid valve, that are
selectively operable responsive to a control signal from the
micro-controller 110. In an illustrated embodiment, the main valve
32 is suitably configured to be an on/off valve and to be in one of
an open or closed position responsive to the signal(s) received
from a control device such as the micro-controller 110. Similarly,
the gas control valve 34 is any one of a number of control valves
known to those skilled in the art that can be selectively adjusted
into any of a number of positions between, and including, the
closed and full-open position responsive to control signals from a
control device such as the micro-controller 110. In this way, the
gas control valve 34 adjusts the amount of gas flowing through the
gas control valve to the burner and consequently selectively
controlling the amount of heat energy being produced by the gas
burner 38. The gas burner 38 is any of a number of burners as is
known in the art or structures developed using well-known
principles and/or techniques by which a combustible gas is
controllable intermixed with the surrounding atmosphere so as to
establish a combustion process.
[0034] The flame sensing mechanism 50 is typically provided for use
in determining the presence of continuous combustion of the
fuel/air mixture. In one embodiment, the sensing mechanism embodies
the flame electrical phenomena of flame rectification between the
igniter 60 and an isolated metal sheath surrounding the igniter as
the mechanism for detecting the presence of a flame. In this
embodiment, a flame is detected or determined to be present if a
current leakage between the igniter and the sheath is in excess of
a predetermined value. In other embodiments, the flame sensing
mechanism is a thermopile type of sensor that senses the
temperature of the area in which the fuel/air mixture is being
combusted or comprises an optical sensor. The flame sense mechanism
also may comprise the igniter shield and/or the grounded burner
element. The sensing mechanism 50 is operably coupled or
interconnected to the micro-controller 110 to provide indications
or signals representative of one of the presence of a flame or the
lack of a flame. The actions taken by the micro-controller 110
response to such indications is hereinafter described.
[0035] The igniter 60 is any of a number of electric resistance or
hot surface igniters known to those skilled in the art appropriate
for the intended use/application described herein. In a
particularly illustrative embodiment, the igniter 60 is a
ceramic/intermetallic hot surface igniter such as Norton Mini
Igniters.RTM. manufactured by St. Gobain Industrial Ceramics Norton
Igniter Products. Such an ignition device typically includes a
heating element that extends outwardly from an end of the base
which it is secured to. This shall be not limiting as the present
invention can be used with other types of hot surface igniters as
well as other types of ignition devices or igniters, such as for
example Norton CRYSTAR Igniters.RTM.. In specific exemplary
embodiments, the electric surface igniter 60 is an electrical
resistance igniter having a nominal operating voltage of 18, 60,
70, 80, or 150 volt (V)AC, however, it should be recognized that
the present invention is not particularly limited to these
exemplary nominal operating voltages.
[0036] The gas control system 100 includes a micro-controller 110,
a power switching mechanism 120 and a mechanism for monitoring the
igniter 60 so as to determine when the igniter has reached a
temperature suitable for ignition of the gas. In an illustrative
embodiment, the monitoring mechanism is a current sensing mechanism
130 as is known in the art that senses the igniter current. As is
known to those skilled in the art, a relationship can be
established relating the igniter current to the temperature of the
igniter 60. In this way, when the igniter current being sensed by
the current sensing mechanism 130 reaches a predetermined value,
hereinafter referred to as the current threshold, it is known that
the igniter 60 has achieved the minimum operating temperature
necessary to ignite the gas-air mixture. When the sensed igniter
current reaches the current threshold, this condition is sometimes
referred to as the ignition source being "proved". It should be
recognized that other mechanisms known to those skilled in the art
are contemplated for use in the present invention for determining
the operational condition of the igniter 60. For example, a
temperature sensitive element (e.g., a bimetallic element) can be
positioned proximal the igniter 60 so as to provide a signal
indicative of when a temperature is in excess of pre-determined
value.
[0037] The power switching mechanism 120 is any of a number of
circuits and/or circuit element(s) that, responsive to control
signals from the micro-controller 110, at least selectively
energizes the igniter 60 (i.e., turn the igniter on) so as to
heat-up or warm-up the igniter so the igniter is hot enough to
ignite the gas and to de-energize (i.e., turn the igniter off) to
stop the resistance heating of the igniter. As described
hereinafter, in one embodiment of the present invention, the power
switching mechanism 120 also is controlled by the micro-controller
110, after successfully igniting the gas, so as to maintain the
igniter 60 at a predetermined temperature or in a predetermined
temperature range, less than the gas ignition temperature. The
system may further comprise enhanced ignition element(s) as
disclosed in co-pending and commonly assigned U.S. Published Patent
Application 2003-0164368A1, which is discussed further below and
with particular reference to FIG. 4.
[0038] In an illustrative embodiment, the power switching mechanism
120 includes a thyristor, a rectifier which blocks current in both
the forward and reverse directions. In a more specific embodiment,
the thyristor is a triac as is known to those skilled in the art
that blocks current in either direction until it receives a gate
pulse from the microcontroller 110. Upon receiving the gate pulse,
current flows through the triac. The thyristor or triac is
electrically coupled to the electrical power source 20 and the hot
surface igniter 60 so as to control the flow of current from the
power source through the hot surface igniter. Thus, in the case
where the thyristor or triac is blocking current flow, the hot
surface igniter 60 is de-energized. In the case where the thyristor
or triac has received a gate pulse, current flows through the hot
surface igniter 60 thereby energizing the igniter and causing it to
be heated.
[0039] The microcontroller 110 includes a processing unit 112, a
random access memory 114, a nonvolatile memory 116 and an
applications program for execution in the processing unit. The
applications program includes instructions and criteria for
receiving and processing the various signals being inputted to the
microcontroller 110 from the igniter current sensing mechanism 130,
the flame sensing mechanism 50, and the gas-fired appliance control
mechanism 12. The applications program also includes instructions
and criteria so as to provide output control signals to the main
gas valve 32, the gas control valve 34 and the power switching
mechanism 120, thereby controlling the admission of gas to the
combustion area, energizing the hot surface igniter 60 and
maintaining the igniter in a standby condition to re-ignite the gas
within a predetermined time period. The applications program,
including the instructions and criteria thereof, is discussed below
in connection with FIGS. 3A-D.
[0040] The processing unit 112 is any of a number of
microprocessors known to those skilled in the art for performing
functions described herein and operating in the intended
environment. In an exemplary embodiment, the processing unit 112 is
Samsung S3C9444 or Microchip 12C671. The random access memory (RAM)
114 and the nonvolatile memory 116 is any of a number of such
memory devices, memory chips, or the like as is known to those
skilled in the art. The nonvolatile memory 116 more particularly
can comprise either flash or spindle type of memory. In more
particular illustrative embodiments, the nonvolatile memory 116
includes nonvolatile random access memory (NVRAM), read-only memory
(ROM) such as EPROM. In a particular embodiment, the processing
unit 112, RAM 114 and nonvolatile memory 116 are disposed/arranged
so as to be co-located on a single integrated chip. This is not
particularly limiting as these components can be configured and
arranged in any of a number of ways known to those skilled in the
art.
[0041] The operation of the gas control system 100 of the present
invention, as well as an exemplary illustrative gas-fired appliance
10 embodying such a system is best understood from the following
discussion and with reference to FIGS. 3A-D. Reference also should
be made to FIG. 1 and the foregoing discussion for features and
functionalities of the gas control system 100 not otherwise
provided or discussed hereinafter. As noted above, the following
also describes the functions as well as the instructions and
criteria of the applications program being executed in the
processor 112 of the micro-controller 110.
[0042] The gas control system 100 is operated so the hot surface
igniter 60 is de-energized and the main gas and gas control valves
32,34 are closed during those times when heat energy is not to be
produced by the gas-fired appliance device 10 such as a heating
unit e.g. a water heater. As such, during such non-heat producing
times the gas control system 100 is in an idle state. When heat
energy is to be produced by the gas-fired appliance 10, an input
signal is provided to the micro-controller 110 such as a signal
from the control mechanism 12. Such a signal corresponds to a
signal to start the process of energizing the surface igniter 60 so
as to ignite the gas/gas burner 38, step 402. In the case where the
gas control system 100 is powered down when in the idle state, such
as for example after a period of time has elapsed without receiving
signals to energize the igniter 60 and to ignite the gas/gas burner
38, such a signal can be manifested by restoring power to the
control system. Such signals also essentially are a call for the
production of heat energy.
[0043] After receiving signals calling for heat energy to be
produced, the micro-controller 110 performs a pre-start
verification to detect the presence of a flame, steps 404, 406.
More particularly, the micro-controller 110 evaluates the outputs,
if any, from the flame sensing mechanism 50 to determine if the
output signals indicate the presence of a flame. If it is
determined that a flame is present (YES, Step 406) where none
should be present, that indicated a fault and the micro-controller
110 outputs a lock-out signal so as to cause the gas-fired
appliance 10 to be placed in a lock-out mode, Step 408. In the
lock-out mode, the igniter 60 and the gas valves 32, 34 of the
gas-fired appliance 10 cannot be operated (e.g., igniter cannot be
energized and valves cannot be opened). Typically, the manufacturer
of the gas-fired appliance provides a mechanism by which the
lock-out mode can be reset, for example after a pre-specified
period of time has elapsed or after electrical power to the
appliance has been removed and thereafter restored.
[0044] If it is determined that a flame is not present (NO, Step
406), the micro-controller 110 outputs a control signal to energize
the igniter 60 to heat the igniter up to gas ignition temperature
conditions, Step 410. More particularly, the micro-controller 110
outputs a control signal(s) to the power switching mechanism 120 to
supply electrical power (i.e., voltage and current) to the igniter
60 to energize the igniter. In an illustrative exemplary
embodiment, the switching mechanism 120 is selectively operated by
the micro-controller 110 so the igniter 60 is heated up to gas
ignition temperatures.
[0045] Using outputs from the igniter monitoring mechanism the
micro-controller 110 monitors the igniter, for example the igniter
temperature or parameters (e.g., igniter current) that can be
related to igniter temperature, Step 412, and evaluates these
conditions to determine if the igniter temperature is at or above
the gas ignition temperature, Step 414. As indicated above, the
igniter current can be related to the temperature of the igniter.
Thus, in an exemplary embodiment, the micro-controller 110 monitors
the igniter current sensing mechanism 130 to determine if the
sensed or measured igniter current exceeds a current threshold.
Thus, if the sensed or measured igniter current is at or above the
current threshold, then the igniter temperature correspondingly is
at or above the gas ignition temperature.
[0046] If it is determined that the igniter temperature is below
the gas ignition temperature (NO, Step 414), a determination is
made as to whether a first time-out clock has expired, Step 416. In
other words, a determination is made whether the time that has
elapsed since the signal to energize the igniter 60 was generated
is equal to or greater than a pre-specified time period. As
indicated herein, a given igniter is typically characterized by a
specific time period required to warm-up the igniter so it reaches
the minimum temperature required for ignition of the gas. Thus, the
pre-specified time period for the first time out clock is
established based on the warm-up time period of the igniter being
used. In an illustrative embodiment, the pre-specified time period
is 15 seconds. If it is determined that the first time out clock
has expired (YES, step 416) then the micro-controller 110 outputs a
lock-out signal thereby causing the gas-fired appliance 10 to be
placed in a lock-out mode, Step 408. If it is determined that the
first time out clock has not expired (NO, Step 416), then the
process repeats the process set forth in steps 412 and 414.
[0047] If it is determined that the igniter temperature is at or
above the igniter temperature (NO, Step 414), the micro-controller
outputs one or more control signals causing the main gas valve 32
and the gas control valve 34 to open thereby allowing gas to flow
to the gas burner 38, Step 420. In the exemplary embodiment, the
micro-controller 110 evaluates the sensed or measured igniter
current and if it is determined that the sensed or measured current
is at or above the current threshold, the igniter 60 is determined
to be at a temperature at or above the gas ignition
temperature.
[0048] After opening of the gas valves 32, 34, a time period
typically is established by which the gas coming from the gas
burner 38 should have ignited and a continuous sustained combustion
of the gas should be established. Typically, a time period of about
four (4) seconds is set for the foregoing to be accomplished. Thus,
following opening of the valves 32, 34 a determination is made if a
second time out clock, relating to the foregoing time period, has
expired, Step 422. If the time period has not elapsed (NO, Step
422), the valves 32,34 are kept open and gas continues to flow to
the gas burner 38.
[0049] If it is determined that the second time out clock has
expired (YES, Step 422), the micro-controller 110, using signals
from the flame sensing mechanism 50, determines if flame(s) are
present indicative of the successful ignition of the gas and the
establishment of a continuous sustained combustion of the gas, Step
424. If a flame is detected (YES, Step 424), the micro-controller
110 continues to keep the valves open (e.g., continues to energize
the valves so as to keep them open), Step 430 and initiates or
establishes the re-ignition functionality of the present invention
as hereinafter described.
[0050] As the valves are kept open, signals also are generated to
control or regulate the heat output of the gas burner 38. More
particularly, the control mechanism 12 or a temperature-regulating
device of the gas-fired appliance further provides signals (e.g., a
line voltage signal) to control or regulate the heat output of the
gas burner 38. In an exemplary embodiment, the
temperature-regulating device or the control mechanism 12 outputs a
line voltage signal to the gas control valve 34 that in turn
regulates the amount of gas passing through the valve and thus the
amount of heat energy being produced by the gas burner.
[0051] The process also continues to evaluate the operational
status of the gas-fired appliance 10 to determine if the end of the
particular heating cycle is completed or ended, Step 432. The
heating process continues (NO, Step 432) until it is determined
that the heating cycle is ended (YES, Step 432). When the
particular heating cycle is completed or ended, the valves 32, 34
are closed, the igniter 60 is de-energized and the re-ignition
functionality is terminated, Step 434.
[0052] As indicated above, if a flame is detected (YES, Step 424),
the micro-controller 110 initiates or establishes the re-ignition
functionality of the present invention as hereinafter described.
More particularly, the micro-controller 110 outputs a control
signal(s) to the power switching mechanism 120 to continue to
energize the igniter 60 but so as to maintain the igniter at a
standby or re-ignition standby, Step 440 and continues to monitor
for the presence of a flame, Step 450. As to the energization of
the igniter 60, the micro-controller 110 controls the power
switching mechanism so that voltage and current being applied to
the igniter are such that the igniter is being maintained at a
temperature or in a temperature range that is lower than the gas
ignition temperature but high enough such that the igniter can be
warmed up to the minimum temperature for ignition of the gas in
less than predetermined time period. In exemplary embodiments, the
predetermined time period is 4 seconds or less, more particularly
about 2 seconds and more specifically within the range of from, and
including, about 2 seconds to about 4 seconds.
[0053] From the monitoring of the presence of the flame, Step 450,
a determination is made as to whether the flame is present or not,
Step 452. If it is determined that the flames is present (YES, Step
456) the process continues to perform Steps 450 and 452 until the
heating cycle is ended or a loss of flame is detected. In an
exemplary embodiment, the micro-controller 110 detects the loss of
flame within a second or less, more particularly within about 0.8
seconds. If it is determined that there is no flame present (NO,
Step 452), then the micro-controller 110 outputs a control
signal(s) to the power switching mechanism 120 so as to cause the
igniter 60 to be re-heated to gas ignition temperature conditions,
Step 454. Since the igniter 60 is maintained at a standby
temperature (Step 440), the time to warm-up the igniter and
re-establish gas ignition temperature conditions is within about 2
to 4 seconds as indicated above.
[0054] After a control signal is sent to energize the igniter and
to re-establish gas ignition temperature conditions (Step 454), it
is determined if a predetermined time period has elapsed since such
a control signal was generated, Step 456. If the predetermined time
period has not elapsed (NO, Step 456), the process continues to
perform Steps 454 and 456. If the predetermined time period has
elapsed (YES, Step 456), the process returns to Step 424 (FIG. 3B)
for an evaluation to determine if a flame is again detected.
[0055] If a flame is not detected (NO, Step 424) either when the
gas valves where initially opened after initially energizing the
igniter or after an attempt was made to re-ignite the gas following
the detection of a loss of flame, the micro-controller 110 outputs
a control signal(s) to the power switching mechanism 120 to
de-energize the igniter 60 and outputs control signals to close the
main and gas control valves 32, 34, Step 460. In addition, a
counter representing the number of trial-for-ignition cycles is
incremented by one and the number in the counter is compared with a
maximum number of trial-for-ignition cycles, STEP 462. If it is
determined that the counter equals the maximum number of
trial-for-ignition cycles (YES, Step 462), then the
micro-controller 110 outputs the lock-out signal, Step 408.
[0056] If it is determined that the number in the counter is less
than the maximum number of trial-for-ignition cycles (NO, Step
464), then the system is purged to dissipate unburned gas or
residual products of combustion, Step 464. A predetermined period
of time is set for such purging that is sufficient time for the
dissipation of unburned gas or residual products of combustion. The
process continues with such purging (NO, Step 466) until it is
determined that the predetermined trial-for-ignition time period
has elapsed (YES, Step 466). After the predetermined time period
has elapsed, the process returns to Step 404 (FIG. 3A) to perform
the pre-start verification process.
[0057] Referring now to FIG. 2, there is shown a schematic block
diagram of a gas-fired appliance having a plurality or more gas
burners 38a,b including a gas control system 100' according to the
present invention that configured to separately control each gas
control burner. In FIG. 2, alpha characters were added to the
numerical reference numerals used in FIG. 1 to identify the
components corresponding to those in FIG. 1 but provided for
controlling one of the gas burners illustrated in FIG. 2. Thus,
reference shall be made to the foregoing discussion of FIG. 1 and
FIGS. 3A-D for details of the corresponding elements/components and
functionality.
[0058] As to the micro-controller 110' of this embodiment, the
micro-controller including the applications program being executed
in the processor 112 of the micro-controller may be e.g. suitably
configured so that the micro-controller can separately control the
operation of each gas burner irrespective of the operation of the
other gas burner, or alternatively e.g. the microcontroller may be
configured to control a single burner at a time. For example, one
gas burner could be operating normally while the other of the gas
burners is going through re-ignition of the gas. However, in the
case of implementation of the lock-out mode (Step 408), all of the
gas burners can be affected due to closure of the main gas valve.
As to other aspects of the micro-controller 110 the constituents
thereof and the applications program for execution therein,
reference shall be made to the foregoing discussion regarding FIGS.
1 and 4A-D.
[0059] It should be recognized that although FIG. 2 is illustrative
of burners of a gas-fired range, the circuitry and system
configuration illustrated in FIG. 2 is easily adaptable for use in
controlling a wide range of gas-fired appliances having a plurality
of more of gas burners as well as the gas burners used in ovens for
baking and broiling. For example, in an exemplary illustrative
gas-fired oven according to the present invention, such an oven
would include a main gas valve in series with each of a bake gas
valve for controlling baking and a broil gas control valve for
controlling broiling. This is similar to the arrangement of the
first and second gas control valves 34a,b and the main gas control
valve 32 as shown in FIG. 2. However and in contrast to the
operation of a gas-fired range, in the case of an oven the bake gas
control valve and the broil gas control valve although separately
controllable are not energized nor opened at the same time because
an oven typically is used to bake or broil and not to do both at
the same time. As to other aspects, reference shall be made to the
foregoing discussion for FIGS. 1-3 for further details of the use
of the gas control system of the present invention for a gas-fired
oven as well as other gas-fired applications not otherwise
specifically enumerated herein.
[0060] Now referring to FIG. 4, there is shown a schematic block
diagram of a gas-fired appliance including a gas control system
according to an embodiment of the present invention. Reference
shall be made to U.S. Ser. No. 10/090,450, filed Mar. 4, 2002 (U.S.
Published Patent Application 2003-0164368A1 to Chodacki et al.
published Sep. 4, 2003), the teachings of which are incorporated
herein by reference in their entirety including for details not
otherwise shown in the drawing figures referred to hereinafter or
that described hereinafter. Reference also should be made to the
foregoing discussion for FIGS. 1 and 3A-D for details of common
structure/features/components and method steps not otherwise
described hereinafter.
[0061] The gas control system 300 further includes a zero crossing
circuit 302 and a line voltage measuring circuit 304 and the
applications program for execution in the processor 112 of the
micro-controller 110 further includes instructions and criteria for
controlling the energization of the igniter in accordance with this
embodiment of the present invention.
[0062] The zero cross circuitry 302 is electrically coupled to the
power source 20 to monitor the line voltage from the power source
and is operably coupled to the microcontroller 110. The zero cross
circuitry 302 is any of a number circuits known to those skilled in
the art that is configured and arranged so as to be capable of
detecting or determining when the AC line voltage crosses the time
axis, in other words passes through zero voltage. The zero cross
circuitry 302 also is configured and arranged so as to provide an
output signal to the microcontroller 110 when the AC line voltage
passes through zero voltage. In an exemplary embodiment, the output
signals are digital signals.
[0063] The line voltage measuring apparatus 304 is electrically
coupled to the power source 20 and is operably coupled to the
microcontroller 110. The line voltage measuring apparatus 304
includes any of a number of line voltage measuring circuits known
to those skilled in the art that is configured and arranged to
monitor and determine the line voltage from the power source 4 and
to provide output signals representative of the determined line
voltage. More particularly, such circuits are configured and
arranged so as to be capable of quickly determining the line
voltage and providing such output signals to the microcontroller
110. In a more particular embodiment, the line voltage measuring
apparatus 304 comprises a conventional resistor divider filter
circuit. In an exemplary embodiment, the output signals are analog
signals, however, the circuitry can be configured so as to provide
digital output signals.
[0064] The power switching mechanism 320 comprises a thyristor 322,
that is a rectifier which blocks current in both the forward and
reverse directions. In a more specific embodiment, the thyristor
322 is a triac as is known to those skilled in the art that blocks
current in either direction until it receives a gate pulse from the
microcontroller 110. Upon receiving the gate pulse, current flows
through the triac. The thyristor 322 or triac is electrically
coupled to the power source 4 and the hot surface igniter 60 so as
to control the flow of current from the power source through the
hot surface igniter. Thus, in the case where the thyristor 322 or
triac is blocking current flow, the hot surface igniter 60 is
de-energized. In the case where the thyristor 322 or triac has
received a gate pulse, current flows through the hot surface
igniter 60 thereby energizing the igniter and causing it to be
heated.
[0065] The operation of the gas control system 300 is best
understood from the following discussion and with reference to
FIGS. 3A-D and FIG. 5. Reference also should be made to FIG. 4 and
the foregoing discussion of FIG. 4 and FIG. 1 for features and
functionalities of the control system 300 not otherwise provided or
discussed hereinafter. As noted above, the following also describes
the functions as well as the instructions and criteria of the
applications program being executed in the processor 112 of the
micro-controller 110. The following discussion, however, is
principally limited to describing the particular process associated
with energizing the igniter (Step 410, FIG. 3A) according to this
embodiment of the present invention.
[0066] As indicated above in connection with FIG. 3A, if it is
determined that a flame is not present (NO, Step 406), the
micro-controller 110 outputs a control signal to energize the
igniter 60 to heat the igniter up to gas ignition temperature
conditions, Step 410. According to this embodiment, the
microcontroller 110 outputs a signal (e.g., a gate pulse) to the
triac or thyristor 322 to fire the thyristor so that current from
the power source 4 flows through the hot surface igniter 60. More
particularly, the microcontroller 110 controls the triac or
thyristor 322 so that such current flows continuously and so
"full-on" voltage is supplied to the hot surface igniter 60, step
502. This typically produces an "over voltage" condition, that is
the voltage developed across the hot surface igniter 60 is more
than nominal operating voltage for the igniter(s). Consequently,
the hot surface igniter 60 heats faster to a given temperature and
also will produce more heat energy in the igniter.
[0067] As indicated above, the line voltage measuring apparatus 304
monitors the line voltage of the power source 20 and provides
output signals representative of the line voltage to the
microcontroller. After receiving such an energizing signal, the
microcontroller 110 processes the output signals from the line
voltage measuring apparatus 304 to determine the amplitude of the
line voltage, step 510.
[0068] The microcontroller 110 evaluates the determined or measured
line voltage to determine the time period during which the
"full-line" voltage is to be applied or delivered to the hot
surface igniter 60, step 512. This time period is hereinafter
referred to as the "full-on" time period. More particularly, the
processor 112 compares the determined line voltage with a look-up
table to determine the "full-on" time period appropriate for the
determined line voltage. In more specific embodiment, the look-up
table is stored in the nonvolatile memory 116. In an exemplary
embodiment, this process of determining the "full-on" time period
is completed within about a second after the signal to energize the
igniter is received by the microcontroller 110.
[0069] Consequently, the processor 112 adjusts the "full-on" time
period each time the microcontroller 110 receives an input signal
to energize the hot surface igniter 60 based on the line voltage
being measured each time. In other words, the time the "full-on"
voltage will be applied or delivered to the hot surface igniter 60
will vary depending upon the line voltage being measured each time
the igniter is to be energized. For example, if the measured
voltage is at the lower-end of a given voltage range, then the
"full-on" time period would be adjusted to compensate for this by
applying the "full-on" voltage for a longer period of time.
Similarly, if the measured voltage is at the higher-end of a given
voltage range voltage, then the "full-on" time period would be
adjusted to compensate for this by applying the "full-on" voltage
for relatively shorter time than that for the low-end line
voltage.
[0070] After determining the "full-on" time period, the processor
112 continuously determines if this time has expired, step 504. If
it is determined that the time period has not expired (NO, step
504), then the microcontroller 110, more particularly the processor
112, controls the triac or thyristor 322 so that the "full-on"
voltage continues to be applied or delivered to the hot surface
igniter 60, step 502. If it is determined that the time period has
expired (YES, step 504), then the processor 112 controls the triac
or thyristor 322 to regulate the voltage being applied to the triac
or thyristor, step 506. Thereafter, the process return to Step 412
of FIG. 3A.
[0071] It should be recognized that the igniter energizing process
described in connection with FIGS. 4-5, also is adaptable for use
in energizing the igniter when re-igniting the gas following the
detection of a flame failure (Steps 450, 452, FIG. 3C). In such a
case, the igniter is in one non-heated condition or heated to a
stand-by temperature condition prior to applying the full-on
voltage as hereinabove described. In such cases, the
micro-controller 110 would similarly determine a full-on voltage
time period, control the application of the full-on voltage to the
igniter for the determined time period and after expiration of the
determined time period thereafter regulating the voltage to the
nominal operating voltage for the igniter.
[0072] Although a preferred embodiment of the invention has been
described using specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
* * * * *