US20110086319A1

US20110086319A1 - Fuel gas ignition system for gas burners including devices and methods related thereto

Info

Publication number: US20110086319A1
Application number: US12/837,459
Authority: US
Inventors: Thomas A. Chodacki; Michael W. Tanguay
Original assignee: Saint Gobain Ceramics and Plastics Inc
Current assignee: Coorstek Inc
Priority date: 2009-07-15
Filing date: 2010-07-15
Publication date: 2011-04-14
Also published as: EP2454527A2; EP2454527A4; WO2011009008A3; WO2011009008A2

Abstract

Featured is a gas burner ignition system using miniaturized hot surface igniters of various types configurations and material systems: The ignition system includes an electronic microprocessor which controls both the igniter operation and all functions of the ignition system.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 60/225,891 filed Jul. 15, 2009, the teachings of which are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to control systems for fuel burner igniters and more particularly to control systems for electrical resistance-type igniters for fuel burners and methods for controlling the voltage thereto.

BACKGROUND OF THE INVENTION

There are a number of appliances such as cooking ranges and clothes dryers and heating apparatuses such as boilers and furnaces in which a combustible material, such as a combustible hydrocarbon (e.g., propane, natural gas, oil) is mixed with air (i.e., oxygen) and continuously combusted within the appliance or heating apparatus so as to provide a continuous source of heat energy. This continuous source of heat energy is used for example to cook food, heat water to supply a source of running hot water and heat air or water to heat a structure such as a house.
Because this mixture of fuel and air (i.e., fuel/air mixture) does not self-ignite when mixed together, an ignition source is 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.
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 ceramic intermetallic hot surface igniters. Spark-type igniters that produce an electrical spark that ignites the fuel/air mixture, 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.
Also, the circuitry of the spark type ignition device is sometimes packaged in a module that is electrically connected between a cooktop power supply and the cooktop burner system. Power supply phase conductors and neutral conductors are input to the module, and the module output is fed to an electrode and an igniter for ignition or re-ignition of the burner flame as necessary. Known ignition modules for gas-fired burners, however, are susceptible to malfunctions in use. For example, the phase and neutral conductors of an alternating current power supply can sometimes be reversed and cause the modules to continuously spark. In addition, the modules are often sensitive to voltage on the neutral conductor which desensitizes the flame detection circuit and can lead to continuously generated sparks despite the presence of a flame on a burner. Still further, proper operation of the ignition modules is dependent upon proper connection of ground conductors and neutral conductors in electrical junction boxes that feed the ignition module in use. If the electrical junction box is not properly wired, the ignition module will continuously spark. Unnecessary sparking of the ignition module reduces energy efficiency and also shortens a useable life of the ignition module.
With hot surface igniters, such as the silicon carbide ceramic intermetallic 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 fuel-air mixture (e.g., gas-air). In some applications, this warm-up time can vary between about 15 and about 45 seconds.
In one conventional burner ignition system, the ignition system operates a millivolt type electronic gas safety valve via a flame sensing circuit. Typically millivolt valves are used with a thermopile that generates a voltage that is required to hold the valve coil of the millivolt type electronic gas safety valve open to deliver the gas flow to the burner. When the burner is to be operated, the user manually pushes in a special knob associated with the burner. While the knob is pushed in, gas (i.e., a gas-air mixture) is delivered to the burner until the thermopile has had time to heat up and deliver the millivolt signal to the valve. The elapsed time for this heat up of the thermopile can be in excess of ten seconds.
In this type of safety shutdown system if the burner flame is lost, the burner shuts down and the user re-initiates the burner operating sequence by re-setting the knob by the push and hold sequence. In some cases this type of thermo-electric gas valve operation can be slow to shut down due to accumulated heat at the thermopile, The accumulated heat causes the millivolt signal to be outputted to the valve thereby keeping the valve open until the thermopile cools down sufficiently to terminate the signal output which then allows the valve to close. As a result of the delayed closure, raw unlit gas (i.e., the combustible gas-air mixture) continues to be delivered. In addition to wasting fuel, if an ignition source is inadvertently put in proximity to the burner, the unlit gas would be ignited.
In U.S. Pat. No. 6,322,352, there is found a gas burner for a stove or cook top. Such a stove burner safety system includes an electromagnetic valve and a manual gas cock controlling the gas flow to the burner and a spark plug adjacent the burner which receives a spark pulse from the electric circuitry or electric module which also controls the electromagnetic valve. When the stem of the manual valve is actuated (i.e., pushed in) a switch turns on the electric module. If a flame failure is detected, a train of a certain number of spark pulses is supplied to the spark plug and if re-ignition does not occur within a certain number of pulses or a certain time, the electromagnetic valve is turned off. This system is arranged to use an electromagnet valve that is opened or closed by a signal and a manual valve that initially supplies the gas to start the combustion process.
In U.S. Pat. No. 6,923,640, there is found a flame burner ignition system that includes a burner, a power supply, an electrical system including a ground conductor, and an ignition module. The ignition module includes a first input, a second input, and an output. The output is operatively coupled to the burner, while one of the inputs is coupled to the ground conductor, and the other of the inputs is coupled to the power supply. The described system also includes an isolation transformer that is connected between a junction box and the ignition module. As the ignition module is isolated from the power source, a reversal of line or phase conductor and the neutral conductor does not effect the ignition module. In this way, it is described that the ignition module will operate correctly despite improper wiring of the junction box and so that a false detection of an extinguished flame is not detected by the flame sensing circuitry.
It thus would be desirable to provide a fuel gas ignition system for gas burners that uses hot surface igniters such as miniaturized hot surface igniters, and which includes mechanisms for burner shutdown that provides for safe and reliable operation of the heating device or appliance. It would be particularly desirable to provide such a fuel ignition system that is always on so as to provide a further safety mechanism particularly after actions are taken to terminate burner operations. It would be particularly desirable to provide such a fuel gas ignition system that would shutdown operation of a burner under specific conditions so that follow-on manual actions are taken to resolve the shutdown and/or to re-initiate burner operation. Preferably such an ignition control system would not increase the complexity of operation of the heating device or appliance in comparison to prior art devices.

SUMMARY OF THE INVENTION

The present invention features a fuel gas ignition system and methods for controlling fuel gas ignition. Such control systems and methods further control the energization of the igniter device.
In particular embodiments, such a fuel gas ignition system includes a miniaturized hot surface igniter that having any of a number of various types, configurations and material systems, a gas valve and an microcontroller or microprocessor. The microcontroller or microprocessor includes a software program having code segments, instructions and criteria for controlling operation of the igniter, operation of the gas valve and the ignition of the gas by the igniter.
Such an ignition system further includes a flame sensing means for continuously sensing presence of a burner flame such as by the flame rectification technique. In more particular embodiments, the flame rectification circuit design is established to eliminate the need for earthing or a ground, by the use of a comparator circuit actuated by a burner flame present between the igniter element and igniter assembly shielding.
In more particular embodiments, the instructions and criteria further include instructions and criteria for using the flame sensing signal to trigger an electronically actuated gas valve of the types commonly used in the industry. Specifically, the ignition system is configured so that it can operate a millivolt type electronic gas safety valve via the flame sensing circuit.
In more particular aspects/embodiments, the millivolt valve is activated by a valve driver circuit in the control circuitry. When the electrical contact is made through the knob activating the valve the microcontroller powers the coil in the valve to deliver gas to the burner. At the same time the microcontroller powers the miniaturized hot surface igniter installed in the burner to accomplish the ignition of the gas.
After an igniter activation period of 1 to 4 seconds, the microcontroller causes power to be removed from the igniter and thereafter the microcontroller continuously monitors the burner flame. In the event burner flame is not detected, the microcontroller powers the igniter for the defined igniter activation period to attempt to light/re-light the burner. In further embodiments, the microcontroller is configured to make multiple trials or attempts for such ignition or lighting of the burner. In yet further embodiments, the microcontroller is configured to make N attempts, N being ≧1, to light/re-light the burner. The microcontroller also is operated so that there is near instantaneous shut down of the gas valve by the flame sensing circuit thereby essentially eliminating the possible flow of raw un-lit gas to the appliance.
The microcontroller also is configurable so as to include a soft lock-out so that the valve delivering the gas to the burner is turned off if the burner fails to light as determined by the flame sensing circuit and cannot be thereafter turned on without user intervention. In further embodiments, the microcontroller is configured so the user is required to re-set the valve operation. This allows the user to determine the cause for the burner failing to light or determine the need for service to the appliance.
In alternative embodiments, if flame is not detected after making such multiple or N attempts to light the burner, the microcontroller is configured so as to continuously power the igniter thereafter until flame is detected or the user stops, ends or terminates operation of the burner (e.g., turns the knob to off position). In such a case, the igniter is energized in any of the manners described herein, but is generally energized using a regulated voltage until flame is detected or the user ends burner operations.
In yet a further alternative embodiment, the microcontroller is configured so as to maintain power to the igniter after the igniter activation period instead of removing power as described above, and thereafter the microcontroller continuously monitors the burner flame. In such a case, the microcontroller also is configured so as to continuously power the igniter thereafter until flame is detected or the user ends, stops or terminates operation of the burner (e.g., turns the knob to off position).
In further embodiments, the fuel gas ignition system includes at least one of an auditory signal device or a visual signal device to provide a warning or signal to the user. Also, the microcontroller is configurable so as to cause an auditory and/or a visual signal to be outputted or communicated to the user using such auditory/visual signal devices to identify that (a) the burner was unable to light after a predetermined number or tries (i.e., burner operation is stopped); (b) the burner was unable to light after a predetermined number or tries and the igniter is now in the continuous energized mode; or (c) that the initial attempt to light the was not successful and that the igniter is in the continuous energized mode. In this way, an indication is provided to the user so action to stop, end or terminate burner operation can be taken in the case of (b) and (c) if the burner does not light while the igniter is in the continuous on or energized mode and in the case of (a) to take the appropriate actions so that the user can again try and have the burner start. For example, turning the knob back to off position and then back to the knob position for causing ignition.
In further embodiments, the electronic control functionalities are either AC or DC voltage powered.
In more particular embodiments, the microcontroller is configured so that the igniter is heated up to the ignition temperature(s) and can achieve ignition of the fuel gas within time periods established by industry standards or practices. In yet more particular embodiments, the microcontroller is configurable so as to bring the hot surface igniter to the ignition temperature in 2 seconds or less.
In yet further embodiments, the control system more specifically, at least the microcontroller, is continuously powered.
In yet further embodiments, the microcontroller is configured so that the flame sensing circuit and sensor are checked for proper operation at the end of each burner operating sequence. This operation can be accomplished as these functionalities are continuously powered even after the burner operating sequence. In the case that the microcontroller determines that the flame sensing circuit and sensor are not operating properly, the microcontroller is configured to establish a lockout representative of a fault to prevent further use of the cooktop or at least the affected burner.
The microcontroller also is configurable so as to cause an auditory and/or a visual signal to be outputted or communicated to the user to identify the faulted condition. In this way, an indication is provided to the user to allow them to determine the reason for the fault, to correct the fault and/or to have the appliance serviced. The microcontroller also is configurable so as to allow the user to reset the appliance so that operation can be resumed. For example, the user could be required to actuate a rest button provided on a surface that is not normally accessed by the user or by causing the user to remove and re-apply electrical power to the appliance.
In yet further embodiments, the microcontroller is configured to check the flame sensing signal at the end of burner operation. In the event that the microcontroller detects that a flame is still present after the end of a burning operation, potentially indicating that closure of the gas valve has failed to have properly occurred, the microcontroller is configured to reactivate the valve opening and closure sequence as an attempt to properly close the gas valve. A number of opening and closing sequences can be conducted as required. The microcontroller also is configurable to cause an auditory and/or a visual signal to be outputted or communicated to the user to identify the faulted condition. In this way, an indication is provided to the user to allow them to determine the reason for the fault, to correct the fault and/or to have appliance serviced.
In yet further embodiments, the microcontroller is configurable so that it remains in an active operating mode, even after end-user cessation of operation, for ignition and re-ignition if the flame sensing circuit detects the presence of a gas flame.
In yet further embodiments, the igniter of the present design includes an integrated flame sensing shield which is configured so as to provide for an increase in the level of the flame sense signal due the unique shield geometry as compared to other shield designs.
Other aspects and embodiments of the invention are discussed below.

BRIEF DESCRIPTION OF THE DRAWING

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:

FIG. 1 is a perspective view of an exemplary conventional free standing gas range that can use a fuel gas ignition system of the present invention.

FIG. 2A is a schematic block diagram view of a fuel gas ignition system of the present invention including a burning area element(s) and a gas supply line(s) for clarity.

FIG. 2B is another schematic block diagram view of the fuel gas ignition system of FIG. 2A but configured with an igniter including an integrated flame sensing shield.

FIGS. 3A-B include a high level flow diagram of the process embodied in the fuel gas ignition system of the present invention, more particularly the process embodied in the microcontroller of the fuel gas ignition system.

FIGS. 4A-B are a various views of the insulator (FIG. 4A) and the shield feature (FIG. 4B) of hot surface igniter usable with the fuel gas ignition system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the various figures of the drawing wherein like reference characters refer to like parts, there is shown in FIG. 1 an exemplary conventional free standing gas range 10 that includes an outer body or cabinet 12 that incorporates a generally rectangular cooktop 14. An oven, not shown, is positioned below cooktop 14 and has a front-opening access door 16. A range backsplash 18 extends upward of a rear edge 20 of cooktop 14 and contains various control selectors (not shown) for selecting operative features of the heating elements for cooktop 14 and the oven.
In the exemplary free standing gas range 10, the cooktop 14 includes four gas fueled burners 22 which are positioned in spaced apart pairs positioned adjacent each side of the cooktop. Typically, each pair of burners 22 is surrounded by a recessed area 24 of the cooktop 14. The recessed areas 24 are positioned below an upper surface 24 of the cooktop 14 and typically serve to catch any spills from cooking utensils (not shown) being used with the cooktop. Each burner 22 extends upwardly through an opening in the recessed areas 24, and a grate 28 is positioned over each burner 22. Each grate 28 includes a flat surface thereon for supporting cooking vessels and utensils over the burners 22 for cooking of meal preparations placed therein.
While the cooktop 14 is shown with two pairs of grates 28 positioned over two pairs of burners 22, this shall not be considered limiting as it is known to those skilled in the art that cooktops are configurable so as to include greater or fewer number of burners. For example, the cook top can include three pairs of burners. As also known to those skilled in the art, such a cooktop can be configured so as to provide a grilling surface or griddle which use burners as a heat source for grilling food or the cooking of food on the griddle. Further, the construction and operation of the cooktop gas burners 22 are within the knowledge of those skilled in the art and thus further discussion of the details and construction of burners or the a cooktop not discussed further herein.
It should be recognized that the fuel gas ignition system 100 of the present invention can be embodied in cooktops which form the upper portion of a range, such as range 10, as well as with other forms of cooktops, such as, but not limited to, free standing cooktops that are mounted in kitchen counters. While the description of the present invention makes general reference to a gas-fired cooktop, it is contemplated and thus with in the scope of the present invention for the fuel gas ignition system of the present invention to be embodied with any of a number of other fuel burning apparatuses or combustion burners for a variety of combustible fuels as are known to those skilled in the art or hereinafter developed. Such other apparatuses or applications include, but are not limited to, gas heater devices, gas ovens, gas kilns, gas-fired meat smoker devices, and gas barbecues. In sum, the description provided below is therefore set forth only by way of illustration rather than limitation, and shall not be used to limit practice of the present invention to any particular application.
Referring now to FIG. 2A, there is shown a simplified schematic block diagram view of a cooktop 200 or other heating device that embodies or includes an igniter and fuel gas ignition control system 100 of the present invention, a combustion area 214 and control circuitry 240 that embodies a microcontroller 242 that forms the controlling part of the igniter and fuel ignition control system 100. The illustrated cooktop 200 is described hereinafter as being used with a gaseous hydrocarbon (such as natural gas, propane) as the material to be combusted therein to produce the heat energy. This shall not be construed as a limitation as the materials used for combustion are not limited to gaseous hydrocarbons but also include combustible liquid hydrocarbons and other gases (e.g., hydrogen) and liquids that continuously combust once they are ignited. Also while a single combustion area 214 representative of a burner is shown, this also shall not be considered limiting as the number of combustion areas is dependent upon the type of heating device or appliance embodying the present invention.
The igniter and fuel ignition control system 100 includes one or more igniter devices 120, burner tubes 104, fuel admission valves 108, one for each combustion area 214 or burner of the cooktop. As described further herein, the igniter and fuel ignition control system 100 can further include igniter control electrical circuitry 244 that is configured so that one or more voltage levels are applied to a hot surface igniter. The device control circuitry 240, more specifically the microcontroller 242 is electrically interconnected and operably coupled to the fuel admission valve 108 and the igniter control circuitry 244 so each can be selectively operated to produce heat energy as hereinafter described.
The fuel admission valve 108 is fluidly interconnected using piping or tubing to a source 2 of a combustible material as the fuel for the heating device 200. In the illustrated embodiment, the piping or tubing is interconnected to a source of a gaseous hydrocarbon such as natural gas or propane. The fuel source can be one of an external tank or an underground natural gas piping system as is known to those skilled in the art.
The control circuitry 240, more specifically the microcontroller 242, is electrical interconnected to an external switch device 190 that provides the appropriate signals to the control circuitry (microcontroller) for appropriate operation of the heating device. For example in the case of a cooktop, the external switch device 190 is a mechanical and/or electronic type of switch that can output one or more signals to the control circuitry/microcontroller so that a user can turn the a burner or other heating element (e.g., grill unit, griddle, oven) on and initiate the ignition of the gas/fuel, to regulate or adjust gas flow so as to thereby control the amount of heat energy being developed by the burner (e.g., high through low) and to turn the burner off when heat energy is no longer wanted. If the combustion area is for a heating device such as a furnace to heat a building structure or a hot water heater then the external switch device 190 is a thermostat as is known to those skilled in the art that senses a bulk temperature within the building structure or the hot water in the tank. Based on the sensed temperatures the thermostat outputs signals to the control circuitry 240 more particularly the microcontroller, to turn the furnace or hot water heater on and off.
In use, the control circuitry 240/microcontroller 242 receives a signal from the external switch device 190 calling for the cooktop 200 or other heating device (e.g., stove burner, oven, hot water heater, furnace, etc) to be turned on. In response to such a signal, the microcontroller outputs signals to the igniter control circuitry 244 so as to cause the hot surface igniter 120 to be heated up for ignition, (i.e., cause electricity to flow through the heating element of the igniter 120 to heat the heating element to the desired temperatures for causing a fuel/air mixture to ignite). These processes for energizing and heating of the igniter 120 and operation of the igniter control circuitry 244 are described further herein.
In a particular embodiment, after the igniter heating element is heated to the desired temperature, the fuel admission valve 108 is opened so that the fuel flows through the burner tube 104 to the igniter heating element. As is known in the art, air is mixed with the fuel that is presented to the igniter heating element so that a combustible mixture is thereby created and ignited by the igniter heating element. This ignited fuel/air mixture is located in the combustion area 114 so that useable heat energy can be extracted and used for the intended purpose of the heating device (e.g., to heat food or water). Although a single burner tube 104 is illustrated, as is known to those skilled in the art, a plurality or a multiplicity or more of burner tubes can be provided to generate a desired heat output where one or more fuel admission valves 108 can be provided for each burner tube. Typically, the one of the plurality or multiplicity or more of burner tubes is arranged with respect to the hot surface igniter 120.
While the igniter 120 is generally described herein as a hot surface igniter, this is a particularly preferred mechanism for causing the ignition of the fuel/air mixture. This embodiment shall not be considered as limiting as it is within the scope of the present invention for the combined igniter and fuel ignition control system 100 of the present invention to be adapted for use with any of a number of ignition devices as are known to those skilled in the art or hereinafter developed. Such ignition devices include spark type ignition devices.
A sensor 112 is typically located proximal the hot surface igniter and/or a region of the combustion area 214 for use in determining the presence of combustion of the fuel/air mixture including presence of continued combustion. In one embodiment, the sensor 112 is configured and arranged so as to embody the flame rectification method or technique. In another embodiment, the sensor 112 is a thermopile type of sensor that senses the temperature of the area in which the fuel/air mixture is being combusted.
In further embodiments and with reference to FIGS. 2B and 4A, B, the igniter 120 of the present invention is configured so to include an integrated flame sensing shield 122 (see FIG. 4B) that is secured to the insulator 124 (see FIG. 4A) and also embodied in or located within igniter. The flame sensing shield 122 functions as a shield for protection and also as the sensor 112 for use in determining or detecting the presence of a flame or the combustion process. As also shown in FIG. 2B, such a flame sensing shield is operably coupled to the microcontroller 242. Such a flame sensing shield is particularly suitable/adaptable for use in the flame rectification method or technique.
It shall be understood that when reference is made herein to a sensor that is used in connection with determining or detecting the presence of a flame or the combustion process, such a sensor includes the a flame sensing shield. In yet further embodiments, such a flame sensing shield 122 also is configured so as to provide for an increase in the level of the flame sense signal due the unique shield geometry as compared to other shield designs.
The sensor 112 is interconnected to the control circuitry 240/microcontroller 242 so that if the sensor does not output, for example, a signal indicating the safe and continuous ignition of the fuel/air mixture within a preset period of time, the control circuitry shuts or closes the fuel admission valve 108. As also described herein, the control circuitry 240 (microcontroller 242) also is configured and arranged to repeat this attempt to ignite the fuel/air mixture to start the heating process one or more times. After ignition is obtained, signals are outputted to the igniter control circuitry 244 to cutoff the electrical power to the hot surface igniter 120.
When the heating function is completed, the control circuitry 240/microcontroller 242 receives a signal from the external switch device 190 calling for the heating device to be turned off. In the case of a cooktop, this would be when the user actuates the external switch device 190 (e.g., control knob) to be in the off position. In response to such a signal, the control circuitry 240/microcontroller 242 closes the fuel admission valve 108 to cut off the flow of fuel, thereby stopping the combustion process. As also described herein, if the sensor 112 outputs a signal indicating that fuel is being combusted or burned after the external switch device 190 has been placed in the closed position, the control circuitry 240/microcontroller 242 takes additional actions to shut the fuel admission valve 108.
Referring now to FIGS. 3A-B, there is shown a high level flow diagram illustrating the process for controlling fuel gas ignition, controlling fuel gas admission and controlling the energization of the igniter. Also shown are processes for putting a burner into a safe condition when the igniter and fuel ignition control system 100 of the present invention detects out of normal conditions. More particularly, the flow charts describe the process embodied in the microcontroller 244. As is known to those skilled in the art, it is within the skill of one skilled in the computer programming arts to develop software code including code segments, instructions and criteria from the flow chart(s) provided herein. Also, while in particular embodiments the process is embodied in software code for execution in the microcontroller 244, it is within the skill of those in the arts, to embody the described process is hardware. As also known to those skilled in the art, the control circuitry 240/microcontroller 242 includes storage devices (e.g., NVRAM, EEPROM, and the like) for storing the program code and other parameters described herein) as well as interfaces (e.g., USB and the like) so the microcontroller can be operably coupled to display and input devices (mouse, keyboard).
In particular embodiments, the microcontroller 242 is continuously is powered (i.e., coupled to the power source 4) so that it capable of controlling operating under different operating modes of the cooktop, appliance or heating devices. The appliance, cooktop, heating device is put into operation, Step 300 by any of a number of actions. For example, the user turns the knob or a manual valve or switch representing the external switch device 190 or a signal from a switching or sensing device 190 (e.g., thermostat) is received. This action opens the manual valve and makes an electrical contact to initiate the sequence for powering the igniter. It should be noted that as the solenoid or other electronically actuated/controlled valve, which is inline with the manual valve, is closed, there is no flow of fuel gas to the burner.
With the relay activated in Step 300, full line voltage is applied to the selected igniter and the control circuitry 240/microcontroller 242 measures the line voltage, Step 302. In particular exemplary embodiments the line voltage is measured for the first 200 ms. Based on the measured line voltage from step 2 the control circuitry/microcontroller selects the required “jump start” timing from the lookup table, Step 304. The igniter is “jump started” for the defined time period. After the “jump start” time period has elapsed, the control circuitry/microcontroller regulates the voltage to the igniter for the remained of the igniter on time, Step 306.
When the jump start period is initiated, the control circuitry/microcontroller turns on the solenoid valve (fuel admission valve 108) to the burner, Step 308. In more particular embodiments, the solenoid valve(s) to both rings of the burner are turned on. After a predetermined period of time has elapsed thereafter the igniter is turned off, Step 310. The predetermined time is based on industry standards and practices and in an exemplary embodiment the predetermined time is 4 seconds.
Thereafter, the control circuitry/microcontroller moves into the flame sensing mode to determine if a flame is detected for more than a predetermined period of time (Step 312), where the predetermined period of time is based on industry standards and practices. In an exemplary embodiment the predetermined time is a 3 second duration.
In an embodiment of the present invention, if the flame sense circuit does not detect a flame (No, Step 312), then the solenoid valves are deactivated or turned off by the control circuitry 240/microcontroller 242, Step 320 (FIG. 3B) and the trial for ignition counter is incremented by one, Step 322. The control circuitry/microcontroller then counts the number of trials for ignition and determines if the number of trials is less than or equal to a preset number of trials (N), Step 324, where N is an integer greater than or equal to one (1). In an illustrative embodiment N is three. If the number of trials is less than or equal to N (No, Step 302), then the process returns to step 302 and the system initiates another ignition sequence.
If the number of trials is greater than N (Yes, Step 302), for example there have been 3 trials for ignition without a successful burner ignition, then the process proceeds to Step 326. In Step 326, the system moves to a lockout condition where the system will not allow any further attempts to ignite the burner and thus terminates the process that had been started. In particular embodiments, the burner logic is reset after such a lockout by having the user turn the manual knob 190 into the off position, which powers down the gas admission valve 108 and resets the manual valve switch. This should reset the system 100 thereby allowing the user to again try and turn the failed burner on (i.e., restarting the process at Step 300).
In alternative embodiments, if flame is not detected after making the N attempts to light the burner, the control circuitry 240/microcontroller 244 is configured so the igniter 120 is continuously powered thereafter until flame is detected or the user takes action to stop, end or terminate operation of the burner (e.g., turns the knob to off position). In such a case, the igniter is energized in any of the manners described herein such as using a jump voltage to initially heat up the igniter and thereafter continuously apply a regulated voltage. In general the igniter is energized until flame is detected or the user ends or stops operation of the burner (burner operations).
In yet a further alternative embodiment, the control circuitry 240/microcontroller 244 is configured so that when the system is being operated in the flame sensing mode, the igniter is not turned off as provided in Step 310, but rather as described above, the power to the igniter is maintained after the igniter activation period (e.g., regulated voltage continues to be applied to the igniter), and thereafter the control circuitry/microcontroller continuously monitors the burner flame. In such a case, the control circuitry/microcontroller also is configured so the igniter is continuously powered until flame is detected or the user takes actions to stop, end or terminate operation of the burner (e.g., turns the knob to off position). In this further alternative embodiment, the processes described in connection with Steps 320-324 need not be performed.
In further embodiments, the fuel gas ignition system 100 further includes at least one of a auditory signal device 251 (e.g., chime) or a visual signal device 253 (e.g., light) that is/are operably coupled to the control circuitry/microcontroller. These signal devices 251, 253 provide an auditory and/or a visual signal to the user to identify that (a) the burner was unable to light after a predetermined number or tries (i.e., burner operation) is stopped); (b) the burner was unable to light after a predetermined number or tries and the igniter is now in continuous energized mode; or (c) that the initial attempt to light the was not successful and that the igniter is in the continuous energized mode. In this way, an indication is provided to the user so action to stop, end or terminate burner operation can be taken in the case of (b) and (c) if the burner does not light while the igniter is in the continuous on or energized mode and in the case of (a) so the user can take the appropriate actions so the user can again try to have the burner start. For example, the user could turn the knob back to off position and then back to the knob position for causing ignition.
Referring now back to the process shown on FIG. 3A, if the flame sense circuit does detect a flame (Yes, Step 312), then the system is put into the run mode, Step 330 and the control circuitry 240/microcontroller 242, sets the trial for ignition counter to zero, Step 332.
When the gas flame is detected and the call for burner operation is active (the knob is turned on) and the system is in the run mode, the flame sense circuitry continuously monitors the gas flame of the active burner. Also, a determination is periodically made to determine if the burner is still active, Step 340. If there is a call for burner operation to end (No, Step 340) then the system stops operation of the burner, Step 350.
If burner operation is continuing and the system remains in the run mode, (Yes, Step 340) the solenoid valve(s) or gas admission valve(s) remain open or active, Step 342 and the flame sense circuitry continues to monitor the burner flame, Step 344. If flame is detected (Yes, Step 344), the system remains in the run mode and the process returns to steps 340. If the flame sense detects a loss of flame (No, Step 344), then the system moves to a rapid re-ignition mode, Step 346.
The rapid re-ignition mode, is used in the case where a flame failure is detected during gas burner operation. The rapid-re-ignition operation is a means by which a hot surface igniter can be made to re-light the burner in less than 4 seconds and without de-activating the gas supply to the burner. In the rapid re-ignition mode, the following operational sequences are performed: the burner is ignited and the igniter is operated in the flame sense mode; a determination is made as to flame failure; full line voltage is applied to the igniter for a time increment defined by measured line voltage level, the igniter “jump starts” to ignition temperature in about 2 seconds; the burner is re-ignited; the system regulates the voltage to the igniter for the remainder of the “on” time; the igniter shuts down and moves into the flame sense mode; and the flame sense operation continues to monitor the burner flame. As indicated above, in alternative embodiments, the re-ignition process for the igniter can include operating the igniter in a continuous on or energized mode such as that described above.
In the case where the user has ended the operating sequence (e.g., by turning the knob to off position, Step 350) and in further embodiments of the present invention, a post operation flame sense circuit check is made to determine if there is no flame, Step 360. If the flame sense circuit does not show the presence of a flame (Yes, Step 360), system operation is ended, Step 362.
If the flame sense circuit determines that flame is still present (No, Step 360) after the operating sequence is ended, the system is returned to a continuous operating mode, Step 364. In addition, the control circuitry/microcontroller outputs signals to cycle the fuel admission valve 108 (opening and closing sequences) in an attempt to properly close the valve and thus end gas flow to the burner, Step 366. A determination is made using the flame sense circuit to determine if the gas valve has closed. Step 368. If the gas valve is determined to have closed (Yes, Step 368), then the process proceeds to Step 362 and operation is ended. If it is determined that the gas valve has not closed (No, Step 368), the process returns to Step 364.
In the discussion regarding FIGS. 3A, B, reference is made to applying different voltages to the igniter at different times. In one embodiment of the present invention, the jump start voltage process referred to herein is the process and mechanisms described in U.S. patent application Ser. No. 12/589,253 as filed by at least one of the Applicants of the present invention. The teachings of this application are incorporated herein by reference and reference shall be made to that application for more specific details of the structure and operation of such processes and devices.
As more particularly described herein, the igniter and gas ignition control system 100 of the present invention is operated so the hot surface igniter 20 is de-energized during those times when heat energy is not to be produced by the appliance or heating device. As such, during such non-heat producing times the igniter control circuitry 244 is in an idle state. It also is within the scope of the present invention for the igniter to be de-energized and thus returned to the idle state after the fuel-air mixture is self-sustaining.
As described herein, when heat energy is to be produced by the appliance or heating device, an input signal is provided to the microcontroller 242, such a signal corresponds to a signal to energize the one or more hot surface igniters 120. Following receipt of this signal, the microcontroller outputs a signal (e.g., a gate pulse) to a triac or thyristor of the igniter control circuitry 244 to fire the thyristor so that current from the power source 4 flows through the one or more hot surface igniters 120. More particularly, the microcontroller 242 controls the triac or thyristor so that such current flows continuously and so a first regulated voltage is supplied to the hot surface igniter(s) 120. The first regulated voltage typically produces an over voltage condition, that is the voltage developed across the hot surface igniter (s) 120 is more than nominal operating voltage for the igniter(s). Consequently, the hot surface igniter (s) 120 heats faster to a given temperature and also will produce more heat energy in the igniter(s).
As indicated above, a line voltage measuring apparatus within the igniter control circuitry 244 monitors the line voltage of the power source 4 and provides output signals representative of the line voltage to the microcontroller 242. After receiving such an energizing signal, the microcontroller 242 processes the output signals from the line voltage measuring apparatus to determine the amplitude of the line voltage. 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 240 VAC. 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 120 VAC, which ranges between 102 VAC and 132 VAC and in another case the nominal line voltage is 24 VAC, which ranges between 20 VAC and 26 VAC.
The microcontroller 242 evaluates the determined or measured line voltage and the microprocessor thereof controls the triac or thyristor to regulate the voltage being applied or delivered to the hot surface igniter(s) 120 to maintain the voltage about a first voltage for the igniter. In more particular embodiments, the first voltage is a voltage that is higher than the second regulated voltage and is set so as cause the igniter to heat up rapidly thereby reducing warm up time so as to be in a set range. In further embodiments, the second voltage also is less than the voltage outputted by a power supply and/or power source 2. This includes the case where the power supply includes or embodies a mechanism that steps down the voltage. In more specific embodiments, the first voltage also is set so as to not significantly reduce operating life of the igniter.
In yet further embodiments, the first voltage is set so that the voltage being applied satisfies the following relationship: V_1st=V_nom+(V_nom×c), where V_1stis the first voltage, V_nomis the nominal operating voltage of the low voltage igniter and c is a number that satisfies the following relationship 0.1≦c≦0.4. It shall be understood that low voltage igniters, as that term is used in the subject application, shall mean igniters whose nominal operating voltage is about 60 volts or less such as for example, igniters whose nominal operating voltage is about 6 volts, 12 volts, 18 volts, 24 volts, or 60 volts.
In an exemplary embodiment, the microprocessor or microcontroller 242 controls the triac or thyristor so as to regulate the voltage being applied by duty cycling the AC line voltage in half-wave cycle increments. More particularly, the microprocessor uses the output signals from the zero cross circuitry to control the operation of the triac or thyristor in these half-wave cycle increments. In more specific embodiment's, the regulation method being implemented by the microprocessor regulates the voltage being applied by duty cycling the AC line voltage in half-wave cycle increments with a period of about 50 half-wave cycles that are divided further into sub-periods of about 5 half-wave cycles each to minimize flickering.
The following example illustrates the application of this regulation method in the case where a nominal voltage of 150 VAC is being applied to a hot surface igniter(s). If it is determined that 32 out of the 50 half-wave cycles are needed to regulate the voltage being applied so as to maintain a 150 VAC nominal voltage, then the half-cylces will be distributed in the sub-periods as follows: eight of the 10 sub-periods in the duty cycle would have three half-wave cycles (8×3=24) and the remaining two sub-periods would have four half-wave cycles (2×4=8). Assuming that the two sub-periods with four half-wave cycles are the first and second sub-periods (SP-1 and SP-2, respectively), the microprocessor regulates output voltage to the hot surface igniter(s) by turning on the triac or thyristor for four half-wave cycles and turning it off for one half-wave cycle during the first sub-period (SP-1); turning it on for another four half-wave cycles (SP-2); turning it off for one half-wave cycle; turning it on for three half-wave cycles (SP-3); and so forth to the tenth sub-period (SP-10).
In more particular embodiments, the control circuitry 240/microcontroller 242 further includes a nonvolatile memory that includes a look-up table that associates line voltage from the power source with the number of half-wave cycles needed to regulate the voltage being applied to the hot surface igniter 120 so the voltage being applied is maintained at or about the first voltage. Those skilled in the art can appreciate that the period of the half-wave cycle, the number of sub-periods, and/or the number of half-wave cycles per sub-period can be modified from that described herein and such modification is within the scope and spirit of the present invention.
In further embodiments, the microcontroller 242 evaluates the determined or measured line voltage and periodically makes adjustments to the duty cycle so that the second regulated voltage being applied to the hot surface igniter 120 is being maintained so that the hot surface igniter maintains a fairly consistent temperature. More particularly, the microprocessor/microcontroller compares the newly determined or measured line voltage with the look-up table and determines the number of half-wave cycles needed to regulate the voltage being applied to the hot surface igniter 120 so the voltage being applied is maintained at or about the nominal operating voltage for the igniter.
In further embodiments, the look up table further includes an on-time for applying the first regulated voltage to the hot surface igniter 120. In particular embodiments, the time period is set equal to the on-time and the microprocessor/microcontroller continuously determines if this time has expired. If it is determined that the time period has not expired, then the microcontroller controls the triac or thyristor so that the first regulated voltage continues to be applied or delivered to the hot surface igniter(s) 120. If it is determined that the time period has expired, then the microprocessor controls the triac or thyristor to regulate the voltage being applied by the triac or thyristor at a second regulated voltage.
After the first regulated voltage on-time has expired, the microprocessor controls the triac or thyristor to regulate the voltage being applied or delivered to the hot surface igniter(s) 120 to maintain the voltage at the second regulated voltage to the igniter. As described above, in an exemplary embodiment, the microprocessor controls the triac or thyristor so as to regulate the voltage being applied as the second regulated voltage by duty cycling the AC line voltage in half-wave cycle increments.
In more particular embodiments, the second regulated voltage is lower than the first regulated voltage. In more specific embodiments, the second regulated voltage is regulated so as to be at or about the nominal operating voltage specified for the hot surface igniter 120. In yet more specific embodiments, the second regulated voltage is regulated so as to be about the nominal operating voltage of the hot surface igniter 120, and in even yet more specific embodiments, the second regulated voltage is regulated so as to be essentially the nominal operating voltage of the hot surface igniter.
In more particular embodiments, the nonvolatile memory further includes in the look-up table an association of line voltage from the power source with the number of half-wave cycles needed to regulate the voltage being applied to the hot surface igniter 120 so the applied voltage is maintained at or about the second regulated voltage. Those skilled in the art can appreciate that the period of the half-wave cycle, the number of sub-periods, and/or the number of half-wave cycles per sub-period can be modified from that described herein and such modification is within the scope and spirit of the present invention. As also described above, in further embodiments, the microcontroller evaluates the determined or measured line voltage and periodically makes adjustments to the duty cycle so that the voltage being applied to the hot surface igniter 120 is maintained so that the hot surface igniter maintains a fairly consistent temperature.
Once the microprocessor has initiated the application of the second regulated voltage to the igniter 120, the microprocessor continuously determines if the energization cycle of the hot surface igniter is complete or done. Typically, the microprocessor receives an input signal from an external sensor or switch indicating that the heating process should be terminated or that a stable combustion process has been established within a heating device such that an ignition source is no longer required. If it is determined that the energization cycle is complete, then the microprocessor provides the appropriate outputs that blocks current flow through the triac or thyristor and continues to control the system. If it is determined that the energy station cycle is not complete, then the microprocessor continues to regulate the second regulated voltage being applied to the hot surface igniter 120.
In another embodiment, the heat-up or energization of the igniter 120 uses the methods, techniques, and/or systems described in U.S. Pat. No. 7,148,454, the teachings of which are incorporated herein by reference.
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.

INCORPORATION BY REFERENCE

All patents, published patent applications and other references disclosed herein are hereby expressly incorporated by reference in their entireties by reference.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents of the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

1. A fuel gas ignition system used in a fuel gas burning apparatus, said system including:

a hot surface igniter;

a gas valve;

an microcontroller having a microprocessor; and

a software program for execution on the microprocessor for controlling operation of the fuel gas ignition system; wherein the software program includes code segments, instructions and criteria for controlling operation of the igniter, operation of the gas valve and ignition of the gas by the igniter.

2. The fuel ignition system of claim 1, further including a flame sensing means for continuously sensing presence of a burner flame using a flame rectification technique.

3. The fuel ignition system of claim 2, wherein the flame sensing means further includes a comparator circuit actuated by a burner flame present between the igniter element and igniter assembly shielding.

4. The fuel ignition system of claim 2, wherein the provided instructions and criteria further include instructions and criteria for using a flame sensing signal to trigger an electronically actuated gas valve of one the types commonly used in the industry.

5. The fuel ignition system of claim 1, wherein

the fuel gas burning apparatus includes a control knob;

the gas valve is an electronically controllable valve; and

wherein the instructions and criteria include instructions and criteria for controlling the gas valve responsive to action of the control knob.

6. The fuel ignition system of claim 1, wherein the hot surface igniter is configured so as to include an integrated flame sensing shield including means for flame sensing when using a flame rectification technique.

7. The fuel ignition system of claim 1, wherein the microcontroller is configured and arranged so as to be continuously powered.

8. The fuel ignition system of claim 1, wherein the software program further includes code segments, instructions and criteria for controlling operation of the igniter so that ignition conditions are established with an activation period of between about 1 to 4 seconds.

9. The fuel ignition system of claim 8, wherein the software program further includes code segments, instructions and criteria for controlling operation of the igniter so the hot surface igniter is brought to an ignition temperature in about 2 seconds or less.

10. The fuel ignition system of claim 8, wherein the software program further includes code segments, instructions and criteria for controlling operation of the igniter so that power is removed from the igniter after ignition conditions are determined to have been established.

11. The fuel ignition system of claim 10, wherein the software program further includes code segments, instructions and criteria for:

continuously monitoring the burner flame after ignition conditions are established.

12. The fuel ignition system of claim 11, wherein the software program further includes code segments, instructions and criteria for:

detecting loss of burner flame;

powering the igniter for the defined igniter activation period to light the burner;

performing said powering for N times, N being ≧1, and

terminating gas flow and powering of the igniter, if performing said powering is unable to light the burner after N attempts.

13. The fuel ignition system of claim 12, wherein the software program further includes code segments, instructions and criteria for controlling operation of the igniter and gas valve so that further operation of the burner is contingent upon a user providing an input signal to allow further operation of the burner.

14. The fuel ignition system of claim 1, further includes:

a flame sensing means for sensing presence of a burner flame; and

wherein the software program further includes code segments, instructions and criteria for:

checking for the presence of a burner flame responsive to signals from the sensing means after burner operation is terminated; and

in the case burner flame is detected:

(a) performing gas valve opening and closure sequences,

(b) determining if burner flame is present or missing after performing said valve opening and closure sequences, and

(c) in the case burner flame is determined to be present, continue performing the operations of (a) and (b).

15. The fuel ignition system of claim 14, wherein the software program further includes code segments, instructions and criteria for providing one of an auditory or visual signal to user when said checking determines presence of burner flame after burner operation is terminated.

16. The fuel ignition system of claim 1, wherein the software program further includes code segments, instructions and criteria for checking the flame sensing means to determine if the flame sensing means is operating properly, said checking being performed at the end of each burner operating sequence.

17. The fuel ignition system of claim 16, wherein the software program further includes code segments, instructions and criteria for preventing further operation of at least the burner whose sensing means is determined not to be operating properly.

18. The fuel ignition system of claim 17, wherein the software program further includes code segments, instructions and criteria for providing one of an auditory or visual signal to user when it is determined that the sensing means is not operating properly.

19. The fuel ignition system of claim 2, wherein the sensing means includes a flame sensing circuit and a sensor.