US3710192A

US3710192A - Burner ignition system

Info

Publication number: US3710192A
Application number: US00154429A
Authority: US
Inventors: S Budlane
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-06-18
Filing date: 1971-06-18
Publication date: 1973-01-09
Anticipated expiration: 1990-01-09

Abstract

A burner ignition system for connection to a source of alternating current electric energy. The system has a spark generator, including an ignition transformer. The primary of ignition transformer is connected to a controlled rectifier. The trigger circuit for the controlled rectifier includes a series arrangement of a rectifier, a capacitance and a voltage breakdown device.

Description

United States Patent 1 Budlane [4 1 Jan. 9, 1973 s41 BURNER IGNITION SYSTEM 3,529,910 9/1970 Potts et al 431/27 3,561,900 2/1971 Walbridge ,...43l/256 [75 1 Invent sm'ley Budhn" Fulmn' 3,589,848 6/1971 Potts ..43l/78 [73] Assignee: General Electric Company 3,596,133 7/1971 Warren et al... ..3l7/79 X Filed: J 1971 3,632,285 l/l972 Foster ..43l/264 [21] Appl. No.: 154,429 Primary Examiner-Volodymyr Y. Mayewsky Att0rneyJohn M. Stoudt et al.

[52] US. Cl. ..317/96, 315/206, 431/24,

431/78, 431/264 [57] ABSTRACT [51] Int. Cl ..F23g 3/00 A b n r i nition system for connection to a source of Fleld of Search alternating current electric energy. The system has a 315/206 spark generator, including an ignition transformer. The primary of ignition transformer is connected to a 1 References Clted controlled rectifier. The trigger circuit for the con- UNITED STATES PATENTS trolled rectifier includes a series arrangement of a rect1fier, a capaeltance and a voltage breakdown 3,393,039 7/1968 Eldridge, Jr. et a1. ..-'.3l7/96 X device. 3,457,456 7/1969 Dietz 3,488,131 1/1970 Myers et al ..43 1/24 8 Claims, 1 Drawing Figure I! 54 II o e i PATENTEDJMI 9 ms 3.710.192

I I L L INVENTOR. Sta nley \IBudLane,

ATTO E7.

BURNER IGNITION SYSTEM BACKGROUND OF THE INVENTION This invention relates generally to burner ignition systems and, more particularly, to such systems for use with gas fueled burners such as domestic furnaces, for instance.

Automatic control systems for burners, such as domestic gas furnaces for instance, normally provide means for automatic ignition of the gas. For a number of years the most common approach was the use of a standing pilot. In such igniters, a small pilot flame burned continuously and was used to ignite the gas mixture at the main burner when heat was called for. Such systems have a number of drawbacks including the possibility of the pilot flame being accidentally extinguished.

Over the last several years there has developed the practice of using spark or arc igniters in such control systems. Spark igniters create sparks or an electric arc to ignite the gas mixture. Many spark igniters are of the continuous duty type; that is, they repeatedly provide a full power charge or are so long as heat is being called for. Such a manner of operation results in undue wear of the igniter. Many spark igniters will continue to attempt to light the gas mixture indefinitely in the event heat is called for and the gas mixture does not ignite. This also can cause excessive wear. Some controls include expensive and complicated additional components to stop operation in the event the gas mixture is not ignited. Also prior art ignition systems provide a spark or are of only one energy level. Thus, they must be designed to provide sufficient energy to ignite the gas mixture even under border line or adverse conditions. Thus, such ignition systems always operate to provide an arc of greater energy than is really needed in most instances. This also leads to excessive wear.

SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide an improved burner ignition system.

Another, more specific, object is to provide an improved ignition system of the electric arc type.

Still another-object is to provide such an improved ignition system in which unnecessary arcing is effectively minimized.

Yet another object is to provide such an improved system in which the energy levels of the arcs produced are minimized.

A further object of the present invention is to provide such an improved ignition system which automatically terminates operation after a predetermined period of time.

In carrying out the invention, in one form, I providea burner ignition system including spark generating means and a controlled rectifier adapted to operatively connect the spark generating means to a supply of alternating current electric energy. The controlled rectifier has a gate for application of a control signal to cause conduction of the controlled rectifier during half cycles of applied electric energy of a first polarity. A trigger circuit, including a series arrangement of a rectifier, a capacitance and a voltage breakdown device, connects the gate to the supply of alternating current electric energy to cause conduction of the controlled rectifier during predetermined half cycles of electric energy.

The above mentioned and other features and objects of this invention, as well as the manner of attaining them will become more apparent, and the invention itself will be better understood by reference to the following description taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a schematic electric circuit diagram of an improved burner ignition system in accordance with one form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing there is shown in somewhat schematic form a burner ignition system designed to provide a timed ignition trail for a fuel burner. Upon successful ignition, the system will maintain the fuel valve in an open condition until power is removed from the circuit. At the same time the system automatically will cease the ignition trail and close the gas valve in the event ignition does not occur within the timed period.

The system includes a pair of supply conductors 11 and 12 for connecting the ignition system to a suitable source of alternating current electric energy, such as a volt household circuit in the case of a domestic gas furnace application for instance. For purposes of illustration conductor 11 may be considered to be a power conductor and conductor 12 the ground conductor, as indicated by the ground symbol 13. From conductor 11 to conductor 12 a branch circuit extends through a rectifier or diode 14, a control coil 15 for the gas valve and a controlled rectifier 16 to a conductor 17 which leads to the ground conductor 12. A filter capacitor 18 is connected across the control coil 15 so that the control coil will operate properly on half wave electrical energy. The controlled rectifier 16 includes an anode 16a, a cathode 16c and a gate 16g.

Another branch circuit extends from the conductor 11 through a rectifier or diode 19, resistor 20, capacitor 21 and the primary 22 of a pulse or ignition transformer 23 to the conductor 17. The pulse transformer 23 also includes a secondary 24 with the secondary having a substantially greater number of turns than the primary so that a pulse in the primary winding will cause pulse of higher voltage in the secondary winding. A free wheeling or circulating diode or rectifier 25 is connected across the primary 22 of the transformer. A conductor 26 connects the junction between resistance 20 and capacitor 21 and the junction between the control coil 15 and the anode 16a of the controlled rectifier 16.

A trigger circuit including a series arrangement of a capacitor 27, a diode or rectifier 28 and a voltage breakdown deice in the form of neon tube 29 is connected between the anode 16a and the gate 16g of the controlled rectifier 16. A resistor 30 is connected between the gate of the controlled rectifier 16 and the conductor 17 so as to effectively be connected between the gate 16g and the cathode 16c of the controlled rectifier. A discharge circuit for the capacitor 27 includes a resistor 31 and a switch 32. As indicated by broken line 33, the switch 32 is interconnected with a switch 34 sothat when switch 32 is open switch 34 is closed and when switch 32 is closed switch 34 is open.

Both switches may, for instance, be controlled by a heating thermostat (not shown) so that, when heat is desired, switch 34 is closed and switch 32 is open; and, when no heat is desired, switch,34 is open and the switch 32 is closed. L"

The secondary 24 of the pulse transformer is connected between conductor 17 anda spark or arc electrode 35 which, in turn, is spaced slightly from the gas burner schematically illustrated at 36. Thus, when a pulse is generated in the secondary 24, an electric are or spark is caused between the electrode 35 and the burner 36. Gas is provided to the burner 36 through a supply pipe or conduit 37 from a suitable source (not shown) and the flow of gas may be controlled by valve schematically illustrated at 38. It will be understood that the control coil is interconnected with the valve 38 to control the opening and closing of the valve so that the valve is open only when the coil is energized. It will be understood that, as is well-known in the art, the control coil 15 may be directly connected to the valve 38 or may be the control coil of a relay with the relay being in an additional circuit which controls the energization of the valve.

A flame sensor schematically illustrated at 40 is electrically connected by conductors 41 and 42 to a flame detection circuit schematically illustrated by the block 43. The flame detection circuit is provided with electrical energy by

conductors

44 and 45 which are connected to the supply conductors 11 and 12 respectively. The flame detection circuit 43 is connected to the junction between diode 28 and neon tube 29 through diode or rectifier 46. The flame sensor 40 and flame detection circuit 43 may take any one of a number of forms which are well-known in the art. An electrical signal is provided through the diode 46 in response to the flame sensor sensing flame (such as that illustrated schematically at 47). By the same token, when the flame sensor does not sense flame no signal is provided by the flame detection circuit through the diode 46. it will be understood that the flame sensor may be an ultraviolet detector, a thermocouple or other well-known sensor, for instance.

When the control thermostat calls for no heat, switch 34 is open de-energizing the entire circuit and causing the flame at burner 36 to be extinguished. At the same time switch 32 is closed so as to bleed off any charge which has accumulated on the capacitor 27. When the thermostat subsequently calls for heat, switch 34 is closed and switch 32 is opened. The capacitor 21 charges through the diode l9, resistor and diode 25. When the charge on capacitor 21 reaches a level just above the firing voltage for the neon tube 29, which may conveniently be approximately 90 volts, the neon tube fires or conducts and a gate signal is provided to the controlled rectifier 16, which then goes into conduction. The anode 16a of the controlled rectifier quickly drops to within about 1 volt of ground. However, the capacitor 27 has gained a small incremental charge due to the gate current flowing through it. This charge is clamped or held on capacitor 27 due to the plurality of the diode 28.

As the supply voltage passes through zero, that is as the voltage on conductor 11 passes through zero between a condition positive relative to conductor 12 and a condition negative relative to conductor 12, the

controlled rectifier 16 turns off. When the line voltage again becomes positive, that is the voltage of conductor 11 becomes positive with respect to conductor 12, the capacitor 21 is recharged so as to again cause conduction of the controlled rectifier. However, this second charge on capacitor 21 must reach a value just above the firing voltage of the neon tube 29 plus the incremental charge on capacitor 27 before a gate signal will be provided to the gate 16g of the controlled rectifier. When a sufficient charge accumulates on capacitor 21, a gate signal is again provided to gate 16g through the capacitor 27, diode 28 and neon lamp 29 so that the control rectifier 16 again conducts. The voltage at the anode 16a of the control rectifier quickly falls to within about one volt of ground. During this second firing an additional incremental charge accumulates on the capacitor 27 due to the gate signal. This action is repeated each positive half cycle until the sum of the voltage on capacitor 27 and the firing voltage of neon tube 29 approaches the peak line voltage. When this occurs, no more gate current is available via the capacitor 27.

Each time the controlled rectifier 16 is gated, current flows through diode 14 and control coil 15. The capacitor 18 acts as a half wave d.c. filter and provides current to the coil 15 during negative half cycles so that the half wave energy provided by controlled rectifier 16 is sufficient to hold the valve 38 in an open condition and fuel or gas is provided to the burner 36.

Also, each time the controlled rectifier 16 is gated, capacitor 21 discharges through the control rectifier and the primary 22 of the high tension pulse transformer 23. The high turns ratio between the primary 22 and the secondary 24 of the transformer 23 generates a high voltage in the secondary sufficient to cause a spark or arc between the electrode 35 and the burner 36. This spark or are is designed to cause the gas mixture at the burner to ignite. The diode 25 in addition to serving as a path for charging the capacitor 21 also serves as a free wheeling diode for the transformer primary 22 to allow the field in a primary to collapse during negative half cycles.

Since the charge on capacitor 21 must build to a higher voltage level each succeeding positive half cycle, in order to overcome the firing voltage of neon tube 29 plus the incremental voltage charge of capacitor 27, the voltage generated in the secondary 24 of the transformer at each firing is greater than the' previous voltage and each spark or arc is of a greater energy level than the previous one. Thus, the energy of the arc begins at a low level and increases with each arc to provide an even greater chance of ignition while keeping wear to a minimum.

Assuming there is some sort of malfunction so that a flame is not produced, as soon as the incremental charge on capacitor 27 builds to a level sufficient to prevent further gate signals through that capacitor the controlled rectifier will cease to be gated. This halts the half wave current flow through the control coil 15 and the gas valve 38 is de-energized and closes. Also the ignition arcs or sparks will stop as capacitor 21 no longer is being dumped. This prevents unnecessary wear due to continuous high level arcing over long periods of time and prevents a dangerous situation from developing as a result of continued unignited gas flow.

Assuming that a flame is established, the flame sensor 40 will sense the flame and provide a control signal through conductors 41 and 42 to the flame detection circuit. The flame detection circuit, which may take any one of a number of forms, provides a signal every half cycle through diode 46. This signal is larger than the breakdown or firing voltage of the neon lamp 29 so as to gate the control rectifier 16. This keeps the control coil energized so that the control valve 38 is maintained opened and gas flow continues to the burner. This action of the flame sensor and flame detection circuit does allow repeated partial charging of the capacitor 21 and then its dumping through the control rectifier l6 and primary 22 of the high tension transformer 23. However, the gating of the control rectifier by the detection circuit may be designed to occur relatively early in each positive half cycle so that the energy available in capacitor 21 and the line voltage at that time is relatively low and the are provided is ofa relatively low energy level.

Such operation will continue so long as the thermostat calls for heat. When the thermostat calls for no heat, switch 34 is opened to completely de-energize the circuit. This closes the gas valve 38 and the flame is extinguished. At the same time switch 32 is closed to provide a circulating path for discharging the incremental voltage accumulated on capacitor 27. Thus, the next time the thermostat calls for heat the capacitor 27 will begin in a noncharged state and the initial are between electrode 35 and burner 36 will be of a relatively low level.

I have found that one suitable circuit in accordance with the schematic diagram shown may be provided utilizing the following components:

diode l4 General Electric 1N5060 controlled rectifier General Electric C106B capacitance 18 20 microfarads, 160 volts diode l9 General Electric 1N5060 resistance 20 1.3 kilohms, 5 watts capacitance 21 1.0 microfarad diode 25 General Electric 1N5060 capacitance 27 .22 microfarad diode 28 General Electric 1N5060 neon lamp 29 General Electric SAB resistance 30 l kilohm, :6 watt resistance 31 15 kilohms, 1% watt diode 46 General Electric 1N5060 with the above indicated components and values the ignition trial period provided is approximately 20 seconds.

It should be apparent to those skilled in the art that while I have described what, at present, is considered to be the preferred embodiments of this invention, in accordance with the Patent Statutes, changes may be made in the disclosed system without actually departing from the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A burner ignition system, including:

a. spark generating means;

b. a controlled rectifier adapted to operatively connect said spark generating means to a supply of al ternating current electric energy for providing spark generating power to said spark generating means upon conduction of said controlled rectifier;

2. A burner ignition system as set forth in claim 1 further including means selectively effective to discharge said capacitance.

3. A burner ignition system as set forth in claim 1 wherein said controlled rectifier includes an anode, a cathode and a gate; said trigger circuit being connected between said anode and said gate.

4. A burner ignition system, for connection to a source of alternating current electric energy, including:

a. an ignition transformer having a primary winding and a secondary winding; spark generating device connected to said secondary winding;

c. a controlled rectifier adapted to operatively connect said primary in a supply circuit from the source of electric energy for providing electric energy to said primary winding upon conduction of said controlled rectifier;

d. said controlled rectifier having a gate terminal for application of a control signal to said controlled rectifier to cause conduction of said controlled rectifier during half cycles of applied electric ener 8};

e. a trigger circuit for connecting said gate terminal to the source of electric energy; and

f. said trigger circuit including a series arrangement of a rectifier, adapted to conduct during half cycles of the same polarity as said controlled rectifier, a capacitance and a voltage breakdown device.

5. A burner ignition system as set forth in claim 1 further including means selectively effective to discharge said capacitance.

6. An ignition system as set forth in claim 4 wherein said controlled rectifier includes an anode, a cathode and a gate; said trigger circuit being connected between said anode and said gate.

7. A burner ignition system for connection to a 50 source of alternating current electric energy, including:

a. an ignition transformer having a primary winding and a secondary winding;

a spark generating device connected to said secondary winding;

c. a controlled rectifier having an anode, a cathode and a gate;

. first circuit means connecting said anode and cathode across the source of alternating current electric energy;

e. a storage capacitance; second circuit means connecting said storage capacitance across the source of alternating current electric energy when said controlled rectifier is nonconductive and connecting said storage capacitance in series with said primary of said ignition transformer through the anode-cathode path of said controlled rectifier when said controlled rectifier is conductive;

f. a trigger circuit, including a series arrangement of a rectifier, a second capacitance and a voltage breakdown device, connected between said anode and said gate of said controlled rectifier.

8. A burner ignition system as set forth in claim 7, further including means selectively effective to discharge said capacitance.

Claims

1. A burner ignition system, including: a. spark generating means; b. a controlled rectifier adapted to operatively connect said spark generating means to a supply of alternating current electric energy for providing spark generating power to said spark generating means upon conduction of said controlled rectifier; c. said controlled rectifier having a gate for application of a control signal to said controlled rectifier to cause conduction of said controlled rectifier during half cycles of applied electric energy of a first polarity; d. a trigger circuit for connecting said gate to a supply of alternating current electric energy; and e. said trigger circuit including a series arrangement of a rectifier, adapted to conduct during half cycles of the same polarity as said controlled rectifier, a capacitance and a voltage breakdown device.

4. A burner ignition system, for connection to a source of alternating current electric energy, including: a. an ignition transformer having a primary winding and a secondary winding; b. spark generating device connected to said secondary winding; c. a controlled rectifier adapted to operatively connect said primary in a supply circuit from the source of electric energy for providing electric energy to said primary winding upon conduction of said controlled rectifier; d. said controlled rectifier having a gate terminal for application of a control signal to said controlled rectifier to cause conduction of said controlled rectifier during half cycles of applied electric energy; e. a trigger circuit for connecting said gate terminal to the source of electric energy; and f. said trigger circuit including a series arrangement of a rectifier, adapted to conduct during half cycles of the same polarity as said controlled rectifier, a capacitance and a voltage breakdown device.

7. A burner ignition sysTem for connection to a source of alternating current electric energy, including: a. an ignition transformer having a primary winding and a secondary winding; b. a spark generating device connected to said secondary winding; c. a controlled rectifier having an anode, a cathode and a gate; d. first circuit means connecting said anode and cathode across the source of alternating current electric energy; e. a storage capacitance; second circuit means connecting said storage capacitance across the source of alternating current electric energy when said controlled rectifier is nonconductive and connecting said storage capacitance in series with said primary of said ignition transformer through the anode-cathode path of said controlled rectifier when said controlled rectifier is conductive; f. a trigger circuit, including a series arrangement of a rectifier, a second capacitance and a voltage breakdown device, connected between said anode and said gate of said controlled rectifier.