Patent Application
20100108658
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.
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 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.
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.
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 heated 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.
There have been efforts made in the past to develop a robust, low-noise igniter that can ignite gas rapidly, which is to say within a few seconds. There is found in U.S. Pat. No. 4,925,386 a control system for electrical resistance-type igniters, and more specifically for tungsten heater elements embedded in a silicon nitride insulator. The relatively narrow temperature operating range of silicon nitride igniters necessitates such a control system. Indeed, the operating range of silicon nitride igniters must remain between the lowest temperature that will ignite the fuel-air mixture and the temperature at which the igniter fails, i.e., the tungsten heater element breaks down.
Over time, this narrow range of operating temperatures is further narrowed due to a process referred to as “aging”. As the tungsten heater elements are repeatedly heated to relatively high temperatures, the tungsten filaments oxidize or “age”. Aging manifests as a cross-sectional change, i.e., decrease, in the tungsten filament. As a result, acceptable operating temperatures routinely decrease and continue to decrease with further aging. The described control system includes a microprocessor and a learning routine to control and modulate a solid-state switching means so that the igniter can be heated rapidly to and maintained at or near a suitable ignition temperature, which is below the maximum operating temperature. Moreover, the described learning routine maintains the temperature of the igniter just above the temperature needed to ignite the gas, to provide quick ignition, while continuously monitoring the maximum allowable temperature to prevent damage to the igniter.
Similarly, there is found in U.S. Pat. No. 5,725,368 a refined control system that controls the energizing of a silicon nitride igniter that, purportedly, enables ignition within approximately two seconds. The described control system includes a microcomputer in combination with a triac in series with an igniter and a learning routine. The microcomputer determines the level of power to be applied to the igniter as a function of the voltage available to energize the igniter and the resistance of the igniter. The triac delivers time-dependent power to the igniter using an irregular firing sequence.
There are, however, several shortcomings with these two control systems. First, they are drawn to a specific igniter type that is subject to “aging”. As a result, the systems require hardware and software to enable the learning routine. They also continuously maintain the temperature of the igniter slightly above the minimum ignition temperature, e.g., about 1200 degrees Centigrade (° C.).
There is found in U.S. Pat. No. 7,148,454 systems and methods for energizing an electric resistance igniter by applying line voltage as the input voltage to the electric resistance igniter for a set period of time and then reducing the input voltage to the nominal voltage after the time period time expires. In this way it is described that the electric resistance igniter can be advantageously heated up rapidly as compared to the then typically heat up times of 15-45 seconds and also allow a wider range of igniters to be utilized.
The described system has been found to work very well with electric resistance igniters that are designed to operate at voltages slightly below the nominal voltage range. For example with a 230 volt supply a 120 to 150 volt hot surface igniter operates very well using the above described system. For low voltage igniters, such as 12 or 24 volt electric resistance igniters for example, when using the such a system the accuracy of the voltage regulation and the overpowering of the igniter to reduce warm up time becomes much more sensitive and thus more difficult to control. Because of this, use of the described system for heating up a low voltage igniter can cause a reduction in igniter reliability and/or actual damage to the igniter element itself. Furthermore the potential for high inrush currents when the low voltage igniters are overpowered with a high supply voltage requires the specification of higher power rated components in the control circuit design which relates to higher system costs.
Notwithstanding the above described systems, conventional control systems and methods for supplying voltage to low voltage igniters (e.g., typically 12 and 24 volt nominal in US, although this is not limiting), utilize simple voltage transformers (e.g., simple step-down transformers) to supply the operating voltage to the igniter. These transformers take in the supply voltage (typically 100 to 277 volts) and convert it to a lower secondary voltage, which is used to power the low voltage igniter. Because of operational characteristics of the transformers, the secondary voltage varies during normal operation, which voltage variations follow the variance in the typical supply voltage of +10% to −15% of the nominal voltage.
Consequently, the voltage being supplied to the igniter by the transformer will vary as well between +10% to −15% of the nominal supply voltage. That being the case, a low voltage igniter must be designed and specified so that they can function properly to ignite the gaseous fuel (i.e., fuel-air mixture) at the lower secondary voltage level and still operate reliably with reasonable service life at the higher secondary voltage level. As a consequence of these variations in the supply voltage, the time response of the typical low voltage igniter will vary significantly as the secondary voltage varies, with typical warm up times ranging from 3 to 10 seconds depending on the required temperature for ignition of the fuel-air mixture.
It thus would be desirable to provide a robust control system and methods related thereto for energizing low voltage hot surface-type igniters so as to reduce igniter warm-up time without significantly increasing the risk of igniter failure or significantly reducing operational life of the igniter. It would be particularly desirable to provide such a control system and method that would reduce warm-up times while minimizing the risk of overpowering the igniter such as that cause by the large current inrushes and reducing the need for higher power rated components.
The present invention features a control system for a hot-surface-type igniter, the control system comprising a control device that is configured and arranged to continuously monitor the line voltage to the system, and when it is time to ignite the fuel-air mixture, to regulate the voltage being applied to the electrical resistance igniter to a first voltage for a given period of time and upon expiration of the period of time to regulate the voltage being applied to the electrical resistance igniter to a second voltage. The control system also includes a switching means that selectively controls the voltage being applied to the electrical resistance igniter responsive to signals from the control device.
In more particular embodiments, the first voltage is a voltage level that is higher than the second voltage level and is set so as to cause the igniter to heat up rapidly thereby reducing warm up time so as to be in a set range. 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: V1st=Vnom+(Vnom×c), where V1st is the first voltage, Vnom is 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 (volts AC or DC).
In more particular embodiments, the second voltage is lower than the first voltage. In more specific embodiments, the second voltage is at or about the nominal operating voltage specified for the igniter. In yet more specific embodiments, the second voltage is about the nominal operating voltage and in even yet more specific embodiments, the second voltage is essentially the nominal operating voltage of the igniter. In yet further exemplary embodiments, the first and second voltages and the time period are set so that the time to warm the igniter up to the igniter's normal operating temperature for igniting the fuel-air mixture satisfies the following relationship 1 sec≦twarmup≦3 sec, less than 4 seconds or less than 5 seconds.
In more particular embodiment, the control device comprises a microprocessor and the switching device comprises a thyristor or more particularly a triac. The microprocessor is any of a number of microprocessor is known to those skills in the art including a central processing unit (CPU), one or more memories, and an application program for execution in the CPU. In a more specific embodiment the one or more memories comprises two memories; one memory accessed by the CPU and the second nonvolatile type of memory for storing information such as look-up tables for determining the first and second voltages and the on-time time for regulating and applying the regulated first voltage and thereafter controlling application of the second voltage. In further embodiments, the CPU and the one or more memories are disposed on a single chip.
The thyristor or triac is operably coupled to the control device and the electric resistance igniter so as to be selectively controlled by the control device and so as to selectively control the first and second voltages being applied to the electrical resistance igniter. In more particular embodiments, the thyristor or triac is controlled by the control device so that the first voltage, as described above, is applied for a predetermined period of time and thereafter the control device controls the thyristor or triac so a second voltage corresponding to the another voltage level or the nominal operating voltage is being applied. In a more specific embodiment, the control device controls the thyristor or triac by duty cycling the AC line voltage in half-wave cycle increments. In yet a more specific embodiment, the control device monitors the line voltage and regulates the first and second voltages being applied so that a fairly constant voltage is applied to the electric resistance igniter.
In yet further embodiments, the control device regulates the voltage being applied to the electrical resistance igniter so that the voltage initially being applied to the electrical resistance igniter is controlled so that the voltage varies as a function of time until it reaches the first voltage and thereafter regulates the voltage so as to be at or about the first voltage until expiration of the period of time. In more particular embodiments, the voltage is controlled so that the voltage varies according to a predetermined algorithm. In an exemplary embodiment, the voltage varies linearly.
In more specific embodiments, the algorithm is established so as to minimize the inrush current (e.g., peak inrush current) as compared to the inrush current that would occur in the case where voltage being applied initially was applied without such voltage control. In more particular embodiments, the algorithm is established so that the peak inrush current with such control is about at least 30 percent less than the peak inrush current when there is no such voltage control; more specifically is about at least 40 percent less than the peak inrush current when there is no such voltage control; and yet more specifically at least about 50 percent less than the peak inrush current when there is no such voltage control.
In further embodiments, the power supply or voltage source that supplies the voltage to the thyristor or triac embodies a means for reducing the nominal supply voltage to a lower or third voltage level so as to reduce shock hazards or risks to users, where the third voltage is higher than the first voltage. In particular embodiments, the third voltage is set so that the nominal output voltage of the step down transformer satisfies the following relationship: V3rd=V1st+(V1st×c), where V3rd is the third voltage, V1st is the first voltage level and c is a number that satisfies the following relationship 0.1≦c≦0.4.
According to another aspect of the present invention, there is featured a method of controlling energizing of one or more electrical resistance igniters. This method includes providing a first voltage to the electrical resistance igniter for a time period; and thereafter providing a second voltage to the electrical resistance igniter after expiration of the time period. In more particular embodiments, such providing a first voltage includes setting the first voltage so as to be at a voltage that is higher than the second voltage level and also so as to cause the igniter to heat up rapidly thereby reducing warm up time so as to be in a set range. In yet further embodiments, such setting the first voltage includes setting the voltage so as to also be at a voltage that does not significantly reduce operating life of the igniter.
In further embodiments, such setting the first voltage includes setting the first voltage so that the first voltage satisfies the following relationship: V1st=Vnom+(Vnom×c), where V1st is the first voltage, Vnom is 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 (volts AC or DC).
In more particular embodiments, such providing a second voltage includes setting the second voltage so it is lower than the first voltage. In more specific embodiments, the second voltage is at or about the nominal operating voltage specified for the igniter. In yet more specific embodiments, the second voltage is about the nominal operating voltage and in even yet more specific embodiments, the second voltage is essentially the nominal operating voltage of the igniter. In yet further exemplary embodiments, the first and second voltages and the time period are set so that the time to warm the igniter up to the igniter's normal operating temperature for igniting the fuel-air mixture satisfies the following relationship 1 sec≦twarmup≦3 sec, less than 4 seconds or less than 5 seconds.
In yet further embodiments, regulating the voltage being applied to the electrical resistance igniter to a first voltage for a given period of time is performed so that the voltage initially being applied to the electrical resistance igniter is controlled so that the voltage varies as a function of time until it reaches V1st and thereafter is regulated so as to be at or about V1st until expiration of the period of time. In more particular embodiments, the voltage is controlled so that the voltage varies according to a predetermined algorithm. In an exemplary embodiment, the voltage varies linearly.
In more specific embodiments, the algorithm is established so as to minimize the inrush current (e.g., peak inrush current) as compared to the inrush current that would occur in the case where voltage being applied initially was applied without such voltage control. In more particular embodiments, the algorithm is established so that the peak inrush current with such control is about at least 30 percent less than the peak inrush current when there is no such voltage control; more specifically is about at least 40 percent less than the peak inrush current when there is no such voltage control; and yet more specifically at least about 50 percent less than the peak inrush current when there is no such voltage control.
The control system and method of the present invention provide a robust control system and methodology for energizing one or more hot surface igniters of a type that is not susceptible to significant aging. Furthermore, the control system and method of the present invention provide a control system and methodology that do not maintain the igniter continuously at above an ignition temperature (e.g., 1200 degrees Centigrade) but rather resistively heats the one or more hot surface igniters with a first regulated input voltage for a predetermined time period and thereafter regulates the input line voltage so that a voltage at another voltage level, a nominal operating voltage for the igniter, is applied.
Also featured is a heating apparatus, the device or an appliance including an igniter control system according to the present invention. Such a heating apparatus, device or appliance further includes mechanisms for controlling and admitting combustion gas in proximity to the igniter.
Other aspects and embodiments of the invention are discussed below.
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:
Referring now to the various figures of the drawing wherein like reference characters refer to like parts, there is shown in
In a particularly illustrative embodiment, the low voltage igniter 20 is a ceramic/intermetallic hot surface igniter such as Norton Mini Igniters® 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®. In specific exemplary embodiments, the low voltage electric surface igniter 20 is an electrical resistance igniter having a nominal operating voltage of 6 volts, 12 volts, 18 volts, 24 volts, or 60 volts (V) AC or DC, however, it should be recognized that the present invention is not particularly limited to these exemplary nominal operating voltages. For simplicity, reference is made hereinafter to resistance hot surface igniter; however, it shall be understood that this refers to a low voltage resistance hot surface igniter.
The power source 4 for the resistance hot surface igniter 20 and the control system 10a has sufficient capacity to heat-up the heating element of the igniter to the temperature required for ignition of the combustible mixture (i.e., fuel-air mixture) as well as for operation of the various functionalities of the control system. The electrical power source 4 is any of a number of sources of electrical power that are known to those skilled in the art. In an exemplary embodiment, the electrical power source 4 is the electrical wiring of the building or structure in which is located the heating device 100 (
The control system 10a according to one aspect of the present invention is configured and arranged so as to control the operation, including the energizing, of the electric surface igniter 20. The control system 10a according to the present invention includes a thyristor 12, zero cross circuitry 14, a power supply 16a, a line voltage measuring apparatus 18 and a microcontroller 30a.
The zero cross circuitry 14 is electrically coupled to the power source 4 to monitor the line voltage from the power source and is operably coupled to the microcontroller 30a. The zero cross circuitry 14 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 14 also is configured and arranged so as to provide an output signal to the microcontroller 30a when the AC line voltage passes through zero voltage. In an exemplary embodiment, the output signals are digital signals.
Power supply 16a is electrically coupled to the power source 4 and to the microcontroller 30a. The power supply 16a is any of a number of power sources known to those skilled in the art that is configured and arranged to provide the appropriate voltage and current required for operation of the microcontroller 30a. In an exemplary embodiment, the power supply 16a includes a series connected capacitor and zeiner diode that steps the line voltage down to the operating voltage of the microcontroller 30a.
As described further herein, in more particular embodiments the power supply 16a is operated so that the electric surface igniter 20 is initially heated up or energized by a increasingly varying AC voltage to the first voltage over a predetermined time period. Thereafter, the power supply 16a is operated so that the electric surface igniter 20 is energized by the first voltage so as to maintain the electric surface igniter 20 at or about a desired operating temperature.
In further embodiments, the electrical power supply 16a or the power source embodies or includes a step down transformer or similar electrical component that steps the voltage down to a voltage having a value less than that being inputted to the transformer. Such a transformer provides a mechanism by which a voltage higher than that used to warm-up the igniter is provided to the circuitry as hereinafter described, but which reduces the voltage to a level that reduces or minimizes shock hazards or risks in the event there is a component failure in the circuitry.
The line voltage measuring apparatus 18 is electrically coupled to the power source 4 and is operably coupled to the microcontroller 30a. The line voltage measuring apparatus 18 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 30a. In a more particular embodiment, the line voltage measuring apparatus 18 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.
The microcontroller 30a includes a processing unit 32, random access memory 34, a nonvolatile memory 36 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 30a from the line voltage measuring apparatus 18 and the zero cross circuit 14 and to provide output control signals to the thyristor 12, thereby controlling the energizing of the hot surface igniter 20. It is within the skill of those knowledgeable in the art and thus within the scope of the present invention, for an application specific integrated circuit (ASIC) or other circuitry component(s) to be used in place of the microcontroller 30b. The applications program, including instructions and criteria thereof, is discussed below in connection with
The processing unit 32 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 32 is a Samsung S3C9444 or Microship 12G671. The random access memory (RAM) 34 and the nonvolatile memory 36 are 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 36 more particularly can comprise either flash or spindle type of memory. In more particular illustrative embodiments, the nonvolatile memory 36 includes nonvolatile random access memory (NVRAM), read-only memory (ROM) such as EPPROM. In a particular embodiment, the processing unit 32, RAM 34 and nonvolatile memory 36 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.
The thyristor 12 is a rectifier which blocks current in both the forward and reverse directions. In a more specific embodiment, the thyristor 12 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 30a. Upon receiving the gate pulse, current flows through the triac. The thyristor 12 or triac is electrically coupled to the power source 4 and the hot surface igniter 20 so as to control the flow of current from the power source through the hot surface igniter. Thus, in the case where the thyristor 12 or triac is blocking current flow, the hot surface igniter 20 is de-energized. In the case where the thyristor 12 or triac has received a gate pulse, current flows through the hot surface igniter 20 thereby energizing the igniter and causing it to be heated.
Now referring to
The AC-DC converter or DC Voltage power supply is electrically coupled to the power source 4 and to the microcontroller 30b. The DC Voltage power supply 16b is any of a number of power sources known to those skilled in the art configured and arranged to provide the appropriate DC voltage and current required for energizing electric surface igniter 20 under the control of the microcontroller 30. In an exemplary embodiment, the DC voltage power supply 16b is an AC-DC switching power supply as is known to those skilled in the art, which converts AC voltage and current to DC voltage and current and which is controllable (e.g., by the microcontroller 30b) so as to output the first and second voltages.
As described further herein, in more particular embodiments, the DC Voltage power supply 16b is operated so that the electric surface igniter 20 is initially heated up or energized by an increasingly varying DC voltage to the first voltage over a predetermined time period. Thereafter, the DC Voltage power supply 16b is operated so that the electric surface igniter 20 is energized by at or about the first voltage so as to maintain the electric surface igniter 20 at or about a desired operating temperature.
In further embodiments, the DC Voltage power supply 16b or the power source embodies or includes a step down transformer or similar electrical component that steps the AC voltage down to an AC voltage having a value less than that being inputted to the transformer. Such a transformer provides a mechanism to reduce the AC voltage to a level that reduces or minimizes shock hazards or risks in the event there is a component failure in the circuitry.
As described above, the microcontroller 30b includes a processing unit 32, random access memory 34, a nonvolatile memory 36 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 30b from the line voltage measuring apparatus 18 to provide output control signals to the DC Voltage power supply 16b, thereby controlling the energizing of the hot surface igniter 20. The applications program, including instructions and criteria thereof, is discussed below in connection with
As indicated above, reference should be made to the above discussion regarding
The operation of the igniter control system 10a, b is best understood from the following discussion and with reference to
As more particularly described below in connection with
When heat energy is to be produced by the appliance or heating device 100, an input signal is provided to the microcontroller 30a, b of the igniter control system 10a, b; such a signal corresponds to a signal to energize the one or more hot surface igniters 20 of the heating device, step 204. Alternatively, in the case where the igniter control system 10a, b is powered down in the idle state, such a signal can be manifested by restoring power to the control system.
Following receipt of this signal, the microcontroller 30a, b outputs a signal (e.g., a gate pulse) to the triac or thyristor 12 to fire the thyristor so that AC current from the power source 4 flows through the one or more hot surface igniters 20 or the DC Voltage power supply 16b is energized so that DC current flows through the one or more hot surface igniters 20. More particularly, the microcontroller 30a, b controls the DC Voltage power supply 16b or the triac or thyristor 12 so that such current flows continuously and so a first regulated voltage is supplied to the hot surface igniter(s) 20, step 206. The first regulated voltage typically produces an over voltage condition, that is the voltage developed across the hot surface igniter (s) 20 is more than nominal operating voltage for the igniter(s). Consequently, the hot surface igniter(s) 20 heats faster to a given temperature and also will produce more heat energy in the igniter(s).
As indicated above, the line voltage measuring apparatus 18 monitors the line voltage of the power source 4 and provides output signals representative of the line voltage to the microcontroller 30a, b. After receiving such an energizing signal, the microcontroller 30a, b processes the output signals from the line voltage measuring apparatus 18 to determine the amplitude of the line voltage, step 206. 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 voltage is 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 30a, b evaluates the determined or measured line voltage and the microprocessor 32 controls the DC Voltage power supply 16b or the triac or thyristor 12 to regulate the voltage being applied or delivered to the hot surface igniter(s) 20 to maintain the voltage about a first voltage for the igniter, step 208. 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 DC voltage outputted by the DC Voltage Power supply 16b or in the case of application of AC voltage, the power supply 16a and/or the power source 4. This includes the case where the power supply 16a 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.
As shown in
In more specific embodiments, the algorithm is established so as to minimize the inrush current (e.g., peak inrush current) as compared to the inrush current that would occur if the case where voltage being applied initially was applied without such voltage control. In more particular embodiments, the algorithm is established so that the peak inrush current with such control is about at least 30 percent less than the peak inrush current when there is no such voltage control, more specifically, is about at least 40 percent less than the peak inrush current when there is no such voltage control; and yet more specifically at least about 50 percent less than the peak inrush current when there is no such voltage control. The specific algorithm controlling the voltage is selected so that the hot surface igniter (s) 20 still will heat faster to a given temperature and produce more heat energy in the igniter(s) while minimizing the peak inrush current during such heating.
In yet further embodiments, the first voltage is set so that the voltage being applied satisfies the following relationship: Vst=Vnom+(Vnom×c), where V1st is the first voltage, V. is 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 and where AC voltage is being applied, the microprocessor 32 controls the triac or thyristor 12 so as to regulate the voltage being applied to the igniter by duty cycling the AC line voltage in half-wave cycle increments. More particularly, the microprocessor 32 uses the output signals from the zero cross circuitry 14 to control the operation of the triac or thyristor 12 in these half-wave cycle increments. In more specific embodiment's, the regulation method being implemented by the microprocessor 32 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-cycles 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 32 regulates output voltage to the hot surface igniter(s) by turning on the triac or thyristor 12 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 nonvolatile memory 36 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 20 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 similar embodiments and in the case where DC voltage is applied to the igniter(s) 20, the nonvolatile memory 36 includes a look-up table that associates line AC voltage with a DC voltage to be outputted by the DC Voltage power supply 16b. In this way, the microcontroller 30b of the igniter control system 10b is configurable so as to energize the hot surface igniter(s) 20 with DC voltage.
In further embodiments, the microcontroller 30a 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 20 is being maintained so that the hot surface igniter maintains a fairly consistent temperature. More particularly, the microprocessor 32 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 20 so the voltage being applied is maintained at or about the nominal operating voltage for the igniter. Similarly, in the case where the control system 10b is configured to apply DC voltage to the igniter, the nonvolatile memory 36 includes a look-up table that associates line AC voltage with a DC voltage to be outputted by the DC Voltage power supply 16b. In this way, the microcontroller 30b of the igniter control system 10b is configurable to regulate the DC voltage being applied to the hot surface igniter 20 so it is maintained at or about the second regulated voltage and/or 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 20. In particular embodiments, a time period is set equal to the on-time and the processor 32 continuously determines if this time has expired, step 210. If it is determined that the time period has not expired (NO, step 210), then the microcontroller 30a, b, more particularly the processor 32, controls the DC voltage power supply 16b (DC voltage) or the triac or thyristor 12 (AC voltage) so that the first regulated voltage continues to be applied or delivered to the hot surface igniter(s) 20, step 208. If it is determined that the time period has expired (YES, step 210), then the microcontroller 30a, b or the processor 32 thereof controls the DC Voltage power supply 16b or the triac or thyristor 12 to regulate the voltage being applied by either of the DC Voltage power supply 16b (DC voltage) or the triac or thyristor (AC voltage), step 212 to a second regulated voltage.
As indicated above, it is within the scope of the present invention to further regulate the AC/DC voltage as it is being initially applied to the igniter (Step 207). In this case, in yet a further embodiment the determined on-time for applying the first regulated voltage is determined so as to include the time taking initially to increase the voltage from zero volts to the first voltage/first regulated voltage.
After the first regulated voltage on-time has expired (YES, step 210), the microprocessor 32 controls the DC Voltage power supply 16b (DC voltage) or the triac or thyristor 12 (AC voltage) so as to regulate the voltage (AC or DC) being applied or delivered to the hot surface igniter(s) 20 to maintain the voltage at or about the second regulated voltage to the igniter, Step 212. As described above, in an exemplary embodiment, the microprocessor 32 controls the triac or thyristor 12 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 20. 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 20, 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 36 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 20 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 30a evaluates the determined or measured line voltage and periodically make adjustments to the duty cycle so that the voltage being applied to the hot surface igniter 20 is maintained so that the hot surface igniter maintains a fairly consistent temperature.
In similar embodiments and in the case where DC voltage is applied to the igniter(s) 20, the nonvolatile memory 36 includes a look-up table that associates line AC voltage with a DC voltage to be outputted by the DC Voltage power supply 16b. In this way, the microcontroller 30b of the igniter control system 10b is configurable so as to energize the hot surface igniter(s) 20 with DC voltage.
Once the microprocessor 32 has initiated the application of the second regulated voltage to the igniter 20 (Step 212), the microprocessor 32 continuously determines if the energization cycle of the hot surface igniter 20 is complete or done, step 214. Typically, the microprocessor 32 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 (YES, step 214), then the microprocessor 32 provides the appropriate outputs that block current flow through the triac or thyristor 12 or causes the DC Voltage power supply 16b to discontinue outputting DC voltage and continues to control the system to the idle condition (step 202). If it is determined that the energy station cycle is not complete (NO, step 214), then the microprocessor 32 continues to regulate the second regulated voltage being applied to the hot surface igniter (step 212).
The igniter control system 10a, b according to the present invention yields a control system that allows a low voltage hot surface igniter(s) 20 to be heated up more quickly and thus shorten the ignition time for the heating device or apparatus. This control system, after a predetermined time period has expired, also reduces the regulated voltage being applied thereafter so the hot surface igniter maintains a fairly consistent operating temperature and so as to not unduly shorten the operational life of the hot surface igniter(s). In further embodiments, such a control system includes a mechanism for controlling the voltage being initially applied so as to minimize inrush current to the igniter. In further embodiments, the methodology for regulating the voltage also yields a method that provides the least amount of electrical emissions, such that a line filter need not be provided, thereby reducing hardware requirements as well as associated costs, such as for manufacturing.
Now referring to
Such a heating device includes an igniter device 20, a burner tube 104, device control circuitry 106, a fuel admission valve 108 and the igniter control system 10. The device control circuitry 106 is electrically interconnected to the fuel admission valve 108 and the igniter control system 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, the fuel for the heating device 100. 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 106 is electrical interconnected to an external switch device 190 that provides the appropriate signals to the control circuitry for appropriate operation of the heating device 100. For example, if the heating device 100 is 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 106 to turn the furnace or hot water is heater on and off. If the heating device 100 is a heating appliance such as a stove, then the external switch device 190 typically is a mechanical and/or electronic type of switch. The switch outputs signals to the control device by which a user can turn the heating device 100 (e.g., stove burner, oven) on and off and also regulate or adjust the amount of heat energy to be developed by the heating device.
In use, the control circuitry 106 receives a signal from the eternal switch device 190 calling for the heating device 100 (e.g., stove burner, oven, hot water heater, furnace, etc) to be turned on. In response to such a signal, the control circuitry 106 provides a signal to the igniter control system 10 to energize the hot surface igniter(s) 20, and thereby cause electricity to flow through the heating element of the igniter(s) 20 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 are as described above in connection with
A sensor 112 is typically located proximal the hot surface igniter for use in determining the presence of continuous combustion of the fuel/air mixture. In one 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 another embodiment, the sensor 112 is configured and arranged to as to embody the flame rectification method or technique. The sensor 112 is interconnected to the control circuitry 106 so that if the sensor does not output, for example, a signal to the control circuitry indicating the safe and continuous ignition of the fuel/air mixture within a preset period of time, the control circuitry shuts the fuel admission valve 108. As is known to those skilled in the art, in certain applications the control circuitry 106 also can be configured and arranged to repeat this attempt to ignite the fuel/air mixture to start the heating process for the heating device 100 or appliance one or more times. Typically, the electrical power to the hot surface igniter 20 also is terminated in such cases.
When the heating function is completed, the control circuitry 106 again receives a signal from the external switch device 190 calling for the heating device to be turned off. In response to such a signal, the control circuitry 106 closes the fuel admission valve 108 to cut off the flow of fuel, thereby stopping the combustion process. In addition, and as indicated above, the igniter control system would be placed in the idle or standby condition (step 202,
Although a number of embodiments of the present invention have been described, it will become obvious to those of ordinary skill in the art that other embodiments to and/or modifications, combinations, and substitutions of the present invention are possible, all of which are within the scope and spirit of the disclosed invention.
All patents, published patent applications and other references disclosed herein are hereby expressly incorporated by reference in their entireties by reference.
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.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/196,759 filed Oct. 20, 2008, and U.S. Provisional Application Ser. No. 61/239,279 filed Sep. 2, 2009, the teachings of all of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61196759 | Oct 2008 | US | |
| 61239279 | Sep 2009 | US |
