U.S. patent application number 10/867143 was filed with the patent office on 2004-11-11 for ignition control system and method.
Invention is credited to Campbell, Bradley J., Reifel, Allan J..
Application Number | 20040224269 10/867143 |
Document ID | / |
Family ID | 22006032 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040224269 |
Kind Code |
A1 |
Reifel, Allan J. ; et
al. |
November 11, 2004 |
Ignition control system and method
Abstract
The invention is directed to an ignition control system that
dynamically adjusts the warm-up time of an igniter within a
predetermined range depending on the success or failure of the
previous ignition or start-up cycle. The system activates the
igniter and waits a predetermined or computed warm-up time. At the
end of the warm-up time, the system opens a gas valve. The system
then waits a preset time from the opening of the gas valve to
determine whether ignition was successful or not. If the ignition
was successful, the system computes a new igniter warm-up time by
decrementing the current time and stores this new value for use
during the next start sequence. If the ignition was unsuccessful,
the system computes a new warm-up time by incrementing the current
value and retrying the start sequence. Preferably, a successful
ignition is always determined by checking for the presence of flame
a fixed time following the opening of the gas valve.
Inventors: |
Reifel, Allan J.;
(Florissant, MO) ; Campbell, Bradley J.;
(Chesterfield, MO) |
Correspondence
Address: |
CESARI AND MCKENNA, LLP
88 BLACK FALCON AVENUE
BOSTON
MA
02210
US
|
Family ID: |
22006032 |
Appl. No.: |
10/867143 |
Filed: |
June 14, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10867143 |
Jun 14, 2004 |
|
|
|
10056693 |
Nov 7, 2001 |
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Current U.S.
Class: |
431/11 |
Current CPC
Class: |
F23N 5/242 20130101;
F23N 5/203 20130101; F23N 1/002 20130101; F23N 2223/48 20200101;
F23N 2227/02 20200101; F23N 2227/38 20200101 |
Class at
Publication: |
431/011 |
International
Class: |
F23N 005/00 |
Claims
What is claimed is:
1. An ignition control system for use in attempting to start a fuel
operated device, the ignition control system comprising: a burner;
a fuel valve moveable between an open position and a closed
position for selectively providing fuel to the burner; an igniter
for igniting a fuel from the burner; a flame sensor configured and
arranged to issue a signal indicative of the presence or absence of
flame at the burner; and a controller operatively coupled to the
igniter and the fuel valve, and in communicating relationship with
the flame sensor, wherein the controller activates the igniter for
a predetermined warm-up time, at the end of the predetermined
warm-up time, the controller moves the fuel valve to the open
position, after a first preset time following the opening of the
fuel valve, the controller deactivates the igniter, after a second
preset time following the opening of the fuel valve, the controller
checks the flame sensor signal to see whether or not flame is
present, thereby indicating a successful or an unsuccessful
ignition, and if the ignition was successful, the controller
decrements the igniter warm-up time during the next start and, if
the ignition was unsuccessful, the controller increments the
igniter warm-up time and, after a predetermined time at which the
valve is moved to the closed position to terminate fuel flow, tries
to start the device again.
2. The ignition control system of claim 1 wherein the igniter
warm-up time is decremented to a minimum warm-up time and
incremented to a maximum warm-up time.
3. The ignition control system of claim 2 wherein the minimum
warm-up time is one of approximately six and 12 seconds, and the
maximum warm-up time is one of approximately 36 and 54 seconds.
4. The ignition control system of claim 1 wherein the second preset
time is approximately five seconds.
5. The ignition control system of claim 1 wherein the controller
includes a micro-processor and a programmable memory device.
6. The ignition control system of claim 1 wherein the warm-up time
is incremented and decremented in steps of one of approximately
three, six, 12 and 24 seconds each.
7. The ignition control system of claim 1 wherein, after an
unsuccessful ignition followed by a successful retry attempt, the
controller performs subsequent ignitions using the warm-up time of
the successful retry attempt.
8. The ignition control system of claim 7 wherein the controller
performs a preset number of subsequently successful ignitions
before decrementing the warm-up time.
9. The ignition control system of claim 8 wherein the preset number
is approximately 250.
10. The ignition control system of claim 1 wherein the fuel is one
of natural gas and propane.
11. The ignition control system of claim 1 wherein the device is
one of a furnace and an appliance.
12. An ignition method for use in attempting to start a fuel
operated device having a burner, a fuel valve moveable between an
open and a closed position for selectively providing fuel to the
burner, an igniter for igniting a fuel from the burner, and a flame
sensor configured and arranged to issue a signal indicative of the
presence or absence of flame at the burner, the ignition method
comprising the steps of: activating the igniter for a predetermined
warm-up time; moving the fuel valve to the open position at the end
of the predetermined warm-up time; deactivating the igniter after a
first preset time following the opening of the fuel valve; checking
the flame sensor signal to see whether or not flame is present,
thereby indicating a successful or an unsuccessful ignition, after
a second preset time following the opening of the fuel valve; if
the ignition was successful, decrementing the igniter warm-up time
during the next start; and if the ignition was unsuccessful,
incrementing the igniter warm-up time and, after a predetermined
time at which the valve is moved to the closed position to
terminate fuel flow, trying to start the device again.
13. The method of claim 12 further comprising the steps of:
blocking the igniter warm-up time from being decremented below a
minimum warm-up time; and blocking the igniter warm-up time from
being incremented above a maximum warm-up time.
14. The method of claim 12 further comprising the step entering a
lock-out state following a set number of unsuccessful ignition
attempts whereby further attempts at ignition are suspended while
in the lock-out state.
15. The method of claim 13 further comprising the steps of:
following a successful retry after an unsuccessful ignition
attempt, utilizing the last computed igniter warm-up for one or
more subsequent ignition attempts.
16. The method of claim 15 further comprising the steps of: after
an unsuccessful ignition attempt, determining whether there have
been a fixed number of consecutive successful ignitions, and if so,
decrementing the igniter warm-up time during the next ignition
attempt.
17. The method of claim 16 wherein the fixed number is
approximately 250.
18. The method of claim 12 wherein the igniter warm-up time is
incremented and decremented in steps of one of approximately three,
six, 12 and 24 seconds each.
19. The method of claim 13 wherein the minimum warm-up time is one
of approximately six and 12 seconds, and the maximum warm-up time
is one of approximately 36 and 54 seconds.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of commonly
assigned copending U.S. patent application Ser. No. 10/056,693,
which was filed on Nov. 7, 2001, by Allan Reifel et al. for a
IGNITION CONTROL SYSTEM AND METHOD and is hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to furnaces and, more specifically,
to ignition control systems for use with furnaces.
[0004] 2. Background Information
[0005] Furnaces and other fuel-based appliances typically include a
fuel control system for supplying and controlling the flow of fuel,
e.g., natural gas, to the furnace and for starting, i.e., igniting,
that fuel to produce heat. A fuel control system includes a burner,
a valve for controlling the flow of fuel to the burner and an
igniter for igniting the fuel provided to the burner. Most igniters
are electrical resistance type igniters, and a power source is
applied across the igniter causing it to heat up.
[0006] Typically, the igniter is electrically energized for a
predetermined time period, sometimes referred to as the igniter
warm-up time, to enable it to reach a temperature sufficiently high
enough to ignite the fuel. There are several manufacturers of
igniters used in such systems. An igniter from any one
manufacturer, because of its particular material composition, mass,
and physical configuration and properties, will generally heat up
at a different rate and to a different final temperature than an
igniter from another manufacturer. Even the same model igniters
from the same manufacturer can have significantly different warm-up
rates and final temperatures. Furthermore, the time it takes a
given igniter to warm-up to a sufficient temperature changes over
the life of the igniter.
[0007] When it is known that a particular igniter having a fast
warm-up time will be used, the length of the igniter warm-up time
period can be established at a relatively low value, for example,
at 15 seconds. However, when the particular igniter to be used has
a slow warm-up time or it is desirable that the system is to be
usable with either fast or slow warm-up time igniters, the length
of the igniter warm-up time period is established at a relatively
large value, for example, at 45 seconds. The use of such a long
warm-up time, however, can reduce the life of many igniters which
do not require such lengthy warm-ups. It also increases the
electrical power consumption of the furnace, thereby resulting in
added operational costs. Accordingly, a fuel control system that
minimizes igniter warm-up time and yet still starts the furnace or
appliance successfully is desirable.
[0008] U.S. Pat. No. 5,364,260 to Moore discloses a
microcomputer-driven igniter system in which the microcomputer is
programmed to generate a unique igniter warm-up time for use during
each burner start cycle. The microcomputer of the '260 patent
determines the time it takes from when the fuel valve is opened to
when flame is first detected at the burner. If the ignition attempt
is successful, the igniter warm-up time is reduced during the next
burner cycle based on a decrease in the length of the flame
detecting time period for the current burner cycle over the length
of the flame detecting period on a previous burner cycle. If the
igniter doesn't ignite the fuel during a so-called valve trial time
period, the flow of fuel to the burner is terminated and there is a
lock-out until manual resetting of the system takes places. The
igniter warm-up time period is increased when a second event
occurs, such as a lapsing of a pre-determined number of burner
cycles which can be coupled to an increase in the length of the
flame detecting time period.
SUMMARY OF THE INVENTION
[0009] Briefly, the invention relates to an ignition control system
that dynamically adjusts the warm-up time of an igniter within a
predetermined range depending on the success or failure of the
previous ignition or start-up cycle. The system, which is
preferably utilized in a furnace, includes a microprocessor coupled
to an electrical programmable read only memory (EPROM) configured
to store a series or program instructions relating to an ignition
sequence to be executed by the microprocessor. The furnace includes
a burner in which the igniter is disposed, an inducer motor for
delivering combustion air to the burner, and a fuel valve for
selectively providing fuel to the burner. The microprocessor is
coupled to and controls the inducer motor, the igniter and the fuel
valve. It may also receive signals from one or more sensors, such
as a flame sensor positioned to detect the presence or absence of
flame at the burner, and one or more pressure and/or limit switches
for confirming the flow of air through the furnace and the absence
of an over-temperature condition.
[0010] In response to a call for heat, the microprocessor accesses
and executes the program instructions stored at the EPROM. In
particular, it activates the igniter causing it to warm-up. It may
also run the inducer motor, thereby forcing any residual or
leftover combustible materials out of the furnace. At the end of a
first predetermined igniter warm-up time, e.g., 30 seconds, the
microcontroller opens the fuel valve, thereby causing fuel to be
delivered to the burner, which, in turn, directs the fuel to the
hot igniter. At a first preset time following the opening the fuel
valve, e.g., 3 seconds, the microcontroller deactivates the
igniter. The microprocessor then waits a second preset time
following the opening of the fuel valve, e.g., 5 seconds, to check
the flame sensor and see whether flame is present, thereby
indicating a successful or unsuccessful ignition.
[0011] If the ignition sequence was successful, the microprocessor
decreases or decrements the igniter warm-up time by a certain
amount, e.g., 3, 6, 12 or 24 seconds, during the next furnace
start. This process is repeated at each start and, assuming
ignition is successful each time, the igniter warm-up time
continues to be decremented until a minimum warm-up time is
reached, e.g., 6 seconds. If, during any furnace start, ignition is
unsuccessful, i.e., flame is not present after waiting the second
preset time, the micro-processor increases the igniter warm-up time
by a certain amount, e.g., 3, 6, 12 or 24 seconds, and retries the
ignition sequence. The warm-up time can be increased up to a
maximum warm-up time, e.g., 54 seconds. If ignition is continues to
be unsuccessful after some number of tries at the maximum warm-up
time, the microprocessor enters a "lock-out" mode in which start-up
of the furnace is blocked for a preset time interval.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention description below refers to the accompanying
drawings, of which:
[0013] FIG. 1 is a highly schematic partial block diagram of a
furnace including the ignition control system of the present
invention;
[0014] FIGS. 2A-B is a flow diagram of a preferred method of the
present invention; and
[0015] FIGS. 3-5 are flow diagrams of alternative methods in
accordance with the present invention.
DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT
[0016] FIG. 1 is a block diagram of an ignition control system 100
in accordance with the present invention. System 100 includes a
controller 102 having a microprocessor (.mu.p) 104 and a memory
106, such as an electrically programmable read only memory (EPROM).
As described herein, memory 106 stores program instructions
executable by the microprocessor 104. Controller 102 may also
include a port 108, such as a RS-232 port, which can be used to
modify or change the program instructions stored at memory 106.
System 100 further includes a burner 110, which receives fuel from
a gas line 112, a gas valve 114 disposed in the gas line 112, and
an igniter 116. Burner 110, gas valve 114 and igniter 116 are each
operatively controlled by the controller 102. In particular, the
gas valve 114 is moveable between a closed and an open position,
thereby selectively controlling the supply of gas to the burner
110. The igniter 116 is disposed proximate to the burner 110 so as
to ignite fuel therefrom. System 100 also includes a flame sensor
118, which is configured to detect the presence of a flame from the
burner 110, and to report that condition to the controller 102.
System 100 may further include an inducer blower motor 122 for
providing combustion air to the burner 110, and one or more
pressure and/or limit switches, such as pressure switch 124 and
limit switch 126, for providing furnace operational information to
the controller 102. A thermostat 120 is also included for providing
calls, such as a call for heat, to the controller 102.
[0017] Controller 102 is preferably a printed circuit board having
a plurality of interconnected components. Suitable components, such
as microprocessors and/or EEPROMs, for use with the present
invention are commercially available from Microchip Technology Inc.
of Chandler, Arizona and Motorola Inc. of Schaumburg, Ill. among
others.
[0018] When the space being heated falls below a preset
temperature, the thermostat 120 issues a call for heat signal to
the controller 102, which responds by activating the furnace. As
part of the furnace activation process, the controller 102 runs the
inducer blower motor 122 for some time, e.g., 30 seconds, to force
any residual combustion products out of the furnace. The controller
102 also confirms that the pressure switch 124 is open, thereby
confirming that the inducer blower is operating properly, and that
the limit switch 126 is closed, thereby confirming that an
over-temperature condition does not exist. Assuming the pressure
and limit switches indicate proper operation of the furnace, the
controller 102 energizes the igniter 116 for a predetermined
warm-up time. The controller 102 then opens the gas valve 114
delivering fuel to the burner 110. The fuel is then ignited by the
hot igniter 116. In accordance with the present invention, the
controller 102 dynamically modifies and/or adjusts the amount of
time that the igniter 116 is warmed up each time the furnace is
activated so as to prolong the life of the igniter 116 and yet
still achieve a successful ignition of the furnace.
[0019] FIG. 2 is a flow diagram of a preferred method in accordance
with the present invention. The control system 100 initially
remains in a suspended state waiting for a call for heat from the
thermostat 120, as indicated at block 202. Upon receiving a call
for heat, the controller 102 runs the inducer blower motor 122 for
sufficient time to force residual combustion materials, if any, out
of the furnace, as indicated at block 204. The controller 102 then
checks the status of the pressure and limit switches 124, 126 to
confirm that the inducer blower is operating properly and that the
furnace is not in an over-temperature condition, as indicated at
block 206. If so, the controller 102 energizes the igniter 116, as
indicated at block 208, and waits a predetermined or computed
igniter warm-up time, as indicated at block 210. For the first or
initial start of the furnace, the predetermined igniter warm-up
time is approximately 30 seconds. At the end of the igniter warm-up
time, the controller 102 opens the gas valve 114, as indicated at
block 212. The controller 102 then de-energizes the igniter 116
after a first preset time following the opening the gas valve 114,
e.g., approximately 3 seconds, as indicated at block 214. Next, the
controller 102 waits a second preset time also following the
opening of the gas valve 114, e.g., approximately 5 seconds, and
checks to see if a flame is present, as indicated at block 216.
Specifically, the controller 102 checks the signal from the flame
sensor 118 at the expiration of the second preset time.
[0020] Based on the presence or absence of a flame at the
expiration of the second preset time, the controller 102 makes a
determination as to whether or not there has been a successful
ignition by the burner 110, as indicated by decision block 218.
That is, if a flame is determined to be present upon the expiration
of the second preset time, the controller 102 concludes that
ignition was successful. In response to a successful ignition, the
controller 102 determines whether the igniter warm-up time is
already set to a preset minimum warm-up time, e.g., six seconds, as
indicated by decision block 220. In this case, the response is No,
as the initial igniter warm-up period was 30 seconds, as described
above. As a result, in this case, the controller 102 computes a new
igniter warm-up time for use during the next start cycle, as
indicated at block 222. In particular, the controller 102 decreases
the current igniter warm-up time, i.e., 30 seconds, by a preset
downward increment or step, e.g., three seconds. In other words,
the microprocessor 104 computes a new igniter warm-up time as
follows: 30-3=27 seconds, and stores this new warm-up time at for
use during the next start cycle of the furnace, as also indicated
at block 222. The new warm-up time may be stored at memory 106, or
at some other memory, such as a register or a random access memory
(RAM). Processing then returns to the wait state represented by
block 202, as shown by arrow 221.
[0021] During the next start cycle, steps 202-216 are repeated,
although this time the igniter is only energized for 27 seconds at
block 210 before the controller 102 opens the gas valve 114. If
ignition is again successful, the warm-up time is again reduced by
the pre-set increment, e.g., three seconds, at block 222, in this
case, to a value of 24 seconds, and this new value is stored for
use during the next start cycle. The new value, e.g., 24 seconds,
replaces the previous value, e.g., 27 seconds. For example, the
memory location may be overwritten with the new value. This process
is repeated, assuming ignition is successful each time, until the
igniter warm-up time is reduced to the preset minimum, e.g., six
seconds. At this point, the result of decision block 220 is yes and
processing simply returns to the wait state of block 202 without
making any further changes to the igniter warm-up time. That is,
the controller 102 (FIG. 1) does not reduce the warm-up time below
the preset minimum, e.g., six seconds.
[0022] After each successful ignition, the controller 102
preferably increments a counter so as to keep track of the number
of furnace starts.
[0023] If, during any start cycle including the initial start,
ignition is unsuccessful, i.e., no flame is detected after waiting
the second preset time following the opening of the gas valve 114,
then processing moves from decision block 218 via No arrow 219 to
block 224 (FIG. 2B). Here, the controller 102 determines whether
the current start cycle is the furnace's initial cycle, i.e., the
first start of the furnace. If it is not, the controller 102 then
determines whether the current igniter warm-up time is set to a
preset maximum warm-up time, e.g., 54 seconds, as indicated by No
arrow 225 leading to decision block 226. If the current warm-up
time is less than the preset maximum, the controller 102 computes a
new igniter warm-up time for use during a retry, as indicated at
block 228. In particular, the controller 102 increases the current
igniter warm-up time by a preset upward increment or step, e.g., 3
seconds. The new warm-up time is also stored. Using this new
warm-up time, the ignition sequence, i.e., steps 204-216, are
repeated as indicated by block 230, and the controller 102
determines whether ignition was successful on this re-try, as
indicated by decision block 232. If so, the controller 102 next
determines whether the furnace has been started a total of 250
times or less, as indicated at decision block 234. If so, the
controller uses the current warm-up time during the next start
cycle, as indicated at block 236, and checks for successful
ignition, at decision block 232.
[0024] By virtue of block 226, the ignition control system 100
limits the igniter warm-up time to a preset maximum value, e.g., 54
seconds. Accordingly, the warm-up time can range between the preset
minimum, e.g., six seconds, and the preset maximum, e.g., 54
seconds. With each successful start, the warm up time is reduced
preferably in three second increments or steps down to the minimum
of six seconds. And, with each failed start, the warm-up time is
increased preferably in three second increments or steps up to the
maximum of 54 seconds.
[0025] Returning to decision block 224 (FIG. 2B), if the failed
ignition occurred on the initial start of the furnace, the
controller 102 repeats the start sequence, i.e., steps 204-216,
using the predetermined warm-up time, e.g., 30 seconds, as
indicated at block 230. The controller 102 preferably maintains a
counter that is incremented for each consecutive ignition failure.
If ignition is still unsuccessful, the controller 102 determines
whether the number of consecutive ignition failures is equal to or
less than a preset limit, e.g., five, as indicated by decision
block 238. If so, processing returns via Yes arrow 239 to decision
block 224. If the controller 102 is unable to start the furnace
after six consecutive retries, it enters a lock-out state, as
indicated by block 240. During the lock-out period, e.g., 1 hour,
the controller 102 is prevented from trying to start the furnace.
At the end of the lock-out period, the controller returns to the
wait state as represented by block 202 (FIG. 2A).
[0026] Upon entering the lock-out state, the controller 102 may
activate a diagnostic indicator, such as a set or row of LEDs, to
notify service personnel of the particular type of failure or error
condition.
[0027] Referring to decision block 234, if the furnace has been
successfully started over 250 times with the current warm-up time,
the controller 102 computes a new igniter warm-up time by
decreasing the current warm-up time by the preset downward
increment, e.g., three seconds, as indicated by No arrow 235, which
returns processing to block 222 (FIG. 2A). The controller 102 then
returns to the wait state represented by block 202.
[0028] It should be understood that the maximum and minimum warm-up
times and the upward and downward increments or steps, e.g., three
seconds, can be modified and still achieve the objectives of the
present invention. Indeed, by using port 108, a service technician
can reprogram the instructions steps as well as the maximum,
minimum and increment or step values stored at memory 106, thereby
tuning the ignition sequence performed by the controller 102.
[0029] FIGS. 3A and 3B are a flow diagram of an alternative start
cycle implemented by the controller 102. The steps of blocks
302-316 (FIG. 3A) correspond to the steps of blocks 202-216 of FIG.
2A described above. Based on the presence or absence of a flame at
the expiration of the second preset time, the controller 102 makes
a determination as to whether or not there has been a successful
ignition of the burner 110, as indicated by decision block 318.
That is, if a flame is determined to be present upon the expiration
of the second preset time, the controller 102 concludes that
ignition was successful. In response to a successful ignition, the
controller 102 determines whether the igniter warm-up time is set
to a preset minimum, which, in is this embodiment, is preferably
twelve seconds, as indicated by decision block 320. In this case,
the response is No as the initial igniter warm-up period was 30
seconds. As a result, the controller 102 computes a new igniter
warm-up time for use during the next start cycle, as indicated at
block 322. In particular, the controller 102 decreases the current
igniter warm-up time, i.e., 30 seconds, by a preset downward
increment, e.g., three seconds. In other words, the microprocessor
104 computes a new igniter warm-up time as follows: 30-3=27
seconds, and stores this new warm-up time for use during the next
start cycle of the furnace, as also indicated at block 322. As
indicated by arrow 323, processing then returns to the wait state
represented by block 302.
[0030] During the next start cycle, steps 302-316 are repeated,
although this time the igniter is only energized for 27 seconds at
block 310 before the controller 102 opens the gas valve 114. If
ignition is again successful, the warm-up time is reduced by
another downward increment, e.g., three seconds, at block 322, to a
value of 24 seconds, and this new value is stored for use during
the next start cycle. This process is repeated, assuming ignition
is successful each time, until the igniter warm-up time is reduced
to the preset minimum, e.g., twelve seconds. At this point, the
result of decision block 320 is yes and processing simply returns
to the wait state of block 302 without making any further changes
to the igniter warm-up time as indicated by Yes arrow 321 leading
to block 302. Thus, a minimum warm-up time, which, in this
embodiment, is preferably twelve seconds, is established.
[0031] After each successful ignition, the controller 102
preferably increments a counter so as to keep track of the number
of furnace starts.
[0032] If, during any start cycle including the initial start,
ignition is unsuccessful, i.e., no flame is detected after waiting
the second preset time following the opening of the gas valve 114,
then processing moves from decision block 318 to block 324 (FIG.
3B). Here, the controller 102 determines whether the failed
ignition occurred during a first or second retry. If not, i.e., if
the failed ignition is a third retry, the controller 102 then
determines whether the current igniter warm-up time is set to a
preset maximum value, e.g., 36 seconds, as indicated by decision
block 326. If it is not, the controller 102 computes a new igniter
warm-up time for use during the next retry, as indicated at block
328. In particular, the controller 102 increases the current
igniter warm-up time by a preset upward increment, e.g., six
seconds. The new warm-up time is also stored. Using this new
warm-up time, the start cycle, i.e., steps 304-316, are repeated,
as indicated by block 330, and the controller 102 determines
whether ignition was successful on this retry, as indicated by
decision block 332. If it is, the controller 102 next determines
whether the furnace has been started less than 250 consecutive
times, as indicated at decision 334. If so, the controller uses the
currently computed warm-up time during the next start cycle, as
indicated at block 336, and checks for successful ignition, at
decision block 332.
[0033] By virtue of block 326, the ignition control system 100
limits the igniter warm-up time to the preset maximum, which in
this case is preferably 36 seconds. Accordingly, the warm-up time
can range between a preset minimum of twelve seconds and a preset
maximum of 36 seconds. With each successful start, the warm up time
is reduced, preferably in three second increments, down to the
preset minimum. And, with each failed start, the warm-up time is
increased, preferably in three or six second increments, up to the
preset maximum.
[0034] Returning to decision block 324 (FIG. 3B), if the failed
ignition occurred after the first or second retry, the controller
102 computes a new warm-up by increasing the current warm-up time
by the preset upward increment, e.g., three seconds, and repeats
the start sequence, i.e., steps 304-316, using newly computed the
warm-up time, as indicated at block 352. The controller 102
preferably maintains a counter that is incremented for each
consecutive ignition failure. If ignition is still unsuccessful,
the controller 102 determines whether the number of consecutive
ignition failures is less than five, as indicated at decision block
338. If so, and the warm-up time is not at the preset maximum
value, e.g., 36 seconds, as in block 354, then processing returns
to decision block 324, as indicated by No arrow 355. Otherwise, the
ignition sequence is repeated according to block 330. If the
controller 102 is unable to start the furnace after five
consecutive re-tries, it enters a lock-out state, as indicated by
block 340. During the lock-out period, which may be on the order of
1 hour, the controller 102 is prevented from trying to start the
furnace. At the end of the lock-out period, the controller returns
to the wait state as represented by block 302 (FIG. 3A).
[0035] Referring to decision block 334, if the furnace has been
successfully started 250 times or more consecutively, the
controller 102 computes a new igniter warm-up time by decreasing
the current warm-up time by the preset downward increment, e.g.,
three seconds, as indicated at block 322 (FIG. 3A). The controller
102 then returns to the wait is state represented by block 302.
[0036] FIGS. 4A and 4B are a flow diagram of yet another furnace
start cycle in accordance with the present invention. The steps
corresponding to blocks 402-416 (FIG. 4A) correspond to the steps
of blocks 202-216 of FIG. 2A described above. Based on the presence
or absence of a flame at the expiration of the second preset time,
the controller 102 makes a determination as to whether or not there
has been a successful ignition of the burner 110, as indicated by
decision block 418. In response to a successful ignition, the
controller 102 decreases the igniter warm-up time for use during
the next start cycle by a first preset downward increment, which,
in this case, is preferably 24 seconds, as indicated by block 422.
In other words, the microprocessor 104 computes a new igniter
warm-up time as follows: 30-24=6 seconds, and stores this new
warm-up time for use during the next start cycle of the furnace, as
also indicated at block 422. Thus, in this embodiment, the warm-up
time is rapidly reduced to a minimum warm-up time, e.g., six
seconds, by the controller 102. The preset minimum is then used
during the next start cycle, as indicated at block 423.
Furthermore, this start cycle, including the six second warm-up
time, is repeated, assuming ignition is successful, each time, as
indicated by decision block 450 by which checks for successful
ignition and Yes arrow 451 which loops processing back to block
423.
[0037] If, during the initial start cycle, ignition is
unsuccessful, i.e., no flame is detected after waiting the second
preset time following the opening of the gas valve 114, then
processing moves from decision block 418 to block 424 (FIG. 4B).
Here, the warm-up time is increased by a first preset upward
increment, e.g., 24 seconds, and ignition is re-tried.
[0038] If ignition at the preset minimum igniter warm-up time,
e.g., six seconds, is unsuccessful, then processing moves from
decision block 450 (FIG. 4A) to block 426 (FIG. 4B) where the
warm-up time is increased by a second preset upward increment,
e.g., 12 seconds, and ignition is retried. At decision block 434,
if there is successful ignition, then the warm-up time is decreased
by a second preset downward increment, e.g., six seconds, at the
next call for heat as shown at block 436. Otherwise, the warm-up
time is increased by a third preset upward increment, e.g., six
seconds, as shown at block 438, and ignition is retried. At
decision block 444, if there is successful ignition after either
increasing or decreasing the warm-up time as in blocks 436 and 438,
then, if the warm-up time is at the preset minimum value, e.g., six
seconds, as determined at decision block 446, the ignition sequence
is repeated with the value of six seconds at the next call for heat
as shown in block 464. If the warm-up time is not at the preset
minimum value, it is preferably decreased by a third downward
increment, e.g., three seconds, as shown in block 452, on the next
call for heat. If, at decision block 444, ignition was not
successful, the warm-up time is increased by a third upward
increment, e.g., three seconds, and ignition is retried, as shown
at block 454. Whether the warm-up time was increased or decreased
by three seconds (blocks 454 and 452 respectively), if there is
successful ignition, as shown by decision block 460, and if there
have been no more than 251 consecutive successful ignitions, then
the ignition sequence is repeated as indicated by block 464 with
the current warm-up time at the next call for heat.
[0039] If, at decision block 460, ignition was unsuccessful, but
there have been five or less consecutive retries as determined by
decision block 466, and the warm-up time is at the preset maximum
value, e.g., 54 seconds, as determined by decision block 462, and
this is the first trial at the preset maximum value, as shown at
decision block 440, then ignition is retried at a warm-up time at
the preset maximum, as shown at block 442. If it is not the first
trial at 54 seconds, then a lock-out occurs, as shown in block 432,
followed by another attempt at ignition at a warm-up time of 30
seconds. The lock-out may extend for about one hour.
[0040] If, at decision block 462, the warm-up time has not reached
the preset maximum, then the warm-up time is increased by the third
preset upward increment, e.g., three seconds, and ignition is
retried, as shown in block 454. If there have been more than five
consecutive retries, as shown in decision block 466, then a
lock-out occurs as in block 432, followed by another ignition
attempt at block 402 at the initial warm-up time, e.g., 30
seconds.
[0041] If, at decision block 458, there are more than 250
consecutive successful ignitions, and if, at decision block 456,
the warm-up time is at the preset minimum, e.g., six seconds, then
the ignition sequence with the warm-up time at the preset minimum
is repeated at the next call for heat, as shown in block 464. But
if the warm-up time is greater than the preset minimum, e.g.,
greater than six seconds, but is not at a preset intermediate time,
e.g., nine seconds, as shown at decision block 448, then the
warm-up time is decreased by the second preset downward increment,
e.g., six seconds, on the next call for heat as shown in block 436.
If the warm-up time is at the intermediate time, the warm-up time
is decreased to the preset minimum, e.g., six seconds, on the next
call for heat, as shown in block 452.
[0042] It should be noted that each "successful ignition" decision
block in FIG. 4B indicates that the ignition sequence represented
by block 402-416 has been performed in response to a call for heat
with the current warm-up time.
[0043] As in other embodiments, upon entering the lock-out state,
the controller 102 may activate a diagnostic indicator, such as a
set or row of LEDs, to notify service personnel of the failure or
error condition. And, as in other embodiments, the maximum and
minimum warm-up times and the increment or step values, e.g., 24,
12, six and three seconds, can be modified and still achieve the
objectives of the present invention.
[0044] FIGS. 5A and 5B are a flow diagram of another start cycle in
accordance with the present invention. The steps represented by
blocks 502-516 correspond to the steps of blocks 202-216 of FIG. 2A
described above. Based on the presence or absence of a flame at the
expiration of the second preset time, the controller 102 makes a
determination as to whether or not there has been a successful
ignition of the burner 110, as indicated by decision block 518. In
response to a successful ignition, the controller 102 decreases the
igniter warm-up time for use during the next start cycle preferably
by 24 seconds, as indicated by block 522. In other words, the
microprocessor 104 computes a new igniter warm-up time as follows:
30-24=6 seconds, and stores this new warm-up time for use during
the next start cycle of the furnace, as indicated at block 523. As
with the start cycle of FIGS. 4A-4B, a minimum warm-up time,
preferably of six seconds, is quickly established, and start cycles
with this warm-up time are repeated, assuming ignition is
successful each time.
[0045] If, during the initial start cycle, ignition is
unsuccessful, i.e., no flame is detected after waiting the second
preset time following the opening of the gas valve 114, then
processing moves from decision block 518 to block 524 (FIG. 5B).
Here, the warm-up time is increased preferably by 24 seconds, and
ignition is retried.
[0046] If ignition is unsuccessful, then processing moves from
decision block 550 to block 526 where warm-up time is increased
preferably by 12 seconds and ignition is re-tried. At decision
block 534, if there is successful ignition, then the warm-up time
is decreased preferably by six seconds at the next call for heat,
as shown at block 536. Otherwise, the warm-up time is increased
preferably by six seconds, as shown at block 538, and ignition is
retried. At decision block 544, if there is successful ignition
after either increasing or decreasing the warm-up time, as in
blocks 536 and 538, then, the warm-up time is decreased preferably
by three seconds and the ignition sequence is repeated with the new
value, e.g., six seconds, at the next call for heat. If ignition is
not successful at decision block 544, the warm-up time is increased
preferably by three seconds and ignition is retried, as shown in
block 554.
[0047] Whether the warm-up time was increased or decreased (blocks
554 and 552 respectively), if there is successful ignition, as
shown in decision block 560, and if there have been no more than a
set number, which in this case is preferably 100, of consecutive
successful ignitions, and the warm-up time is at the preset
minimum, e.g., six seconds, as tested at decision block 556, then
the ignition sequence is repeated, as in block 564, at the preset
minimum warm-up time at the next call for heat. If the warm-up time
is greater than the preset minimum, as tested as decision block
556, then the warm-up time is decreased preferably by three
seconds, as shown at block 552, and that warm-up time is used at
the next call for heat. If there have been more than 100
consecutive successful ignitions, as determined at decision block
558, then the current warm-up time is used on the next call for
heat. If, at decision block 560, there has not been successful
ignition, but there have been less than a set number, e.g., six,
consecutive retries, as shown by decision block 566, and the
warm-up time is at the preset maximum value, e.g., 54 seconds, as
shown in decision block 562, then ignition is retried at the preset
maximum warm-up time, as shown at block 542.
[0048] If, at decision block 562, the warm-up time has not reached
the preset maximum, then the warm-up time is increased, as shown in
block 554, preferably by three seconds and ignition is retried. If
there have been more than five consecutive retries, as shown in
decision block 566, then a lock-out preferably occurs as indicated
at block 532, followed by another ignition attempt at block 502
preferably with a warm-up time at the initial value, e.g., 30
seconds.
[0049] It should be noted that each "successful ignition" decision
block in FIG. 5B indicates that the ignition sequence 502-516 has
been performed with the current warm-up time as a result of a call
for heat.
[0050] Although the ignition control system 100 is preferably
utilized with a furnace (not shown), those skilled in the art will
recognize that system 100 may be used to control other devices or
appliances, such as a dryer. It may also be used with propane as
well as natural gas burners.
[0051] The foregoing description has been directed to specific
embodiments of this invention. It will be apparent, however, that
other variations and modifications may be made to the described
embodiments, with the attainment of some or all of their
advantages. Therefore, it is an object of the appended claims to
cover all such variations and modifications as come within the true
spirit and scope of the invention.
* * * * *