U.S. patent application number 17/321703 was filed with the patent office on 2021-11-25 for combustion device.
The applicant listed for this patent is RINNAI CORPORATION. Invention is credited to Shingo Matsuura.
Application Number | 20210364192 17/321703 |
Document ID | / |
Family ID | 1000005637340 |
Filed Date | 2021-11-25 |
United States Patent
Application |
20210364192 |
Kind Code |
A1 |
Matsuura; Shingo |
November 25, 2021 |
COMBUSTION DEVICE
Abstract
The present invention provides a combustion device. In ON-OFF
combustion control processing for intermittently performing the
combustion operation of burners (4), a control unit (30) of a
combustion device (water heater) (1), which includes the burners
(4), a fuel supply unit (5), and a combustion fan (10), controls
the fuel supply unit (5) and the combustion fan (10) so as to
change the amount of a fuel to be supplied to the burners (4) and
the number of rotations of the combustion fan (10) according to a
required amount of heat for the temperature control of a target
fluid (water for hot water supply) when the burners (4) are ignited
to restart a combustion operation after the burners (4) are
extinguished.
Inventors: |
Matsuura; Shingo; (Aichi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RINNAI CORPORATION |
Nagoya-shi |
|
JP |
|
|
Family ID: |
1000005637340 |
Appl. No.: |
17/321703 |
Filed: |
May 17, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23N 5/242 20130101;
F24H 1/107 20130101; F24H 9/2035 20130101; F23N 1/042 20130101 |
International
Class: |
F24H 9/20 20060101
F24H009/20; F24H 1/10 20060101 F24H001/10; F23N 1/04 20060101
F23N001/04; F23N 5/24 20060101 F23N005/24 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2020 |
JP |
2020-089507 |
Claims
1. A combustion device comprising: a burner which generates heat
for heating a target fluid by a combustion operation; a fuel supply
unit which supplies a fuel to the burner; a combustion fan which
supplies air for combustion to the burner; and a control unit which
has a function for determining a required amount of heat for
temperature control of the target fluid and for controlling the
fuel supply unit and the combustion fan according to the required
amount of heat, wherein the control unit is configured to be
capable of performing ON-OFF combustion control processing, which
is processing for controlling the fuel supply unit and the
combustion fan so as to intermittently perform the combustion
operation of the burner, and is also configured to control the fuel
supply unit and the combustion fan so as to change an amount of a
fuel to be supplied to the burner and a number of rotations of the
combustion fan according to the required amount of heat for
temperature control of the target fluid at the time of igniting the
burner to restart the combustion operation of the burner after the
burner is extinguished in the ON-OFF combustion control
processing.
2. The combustion device according to claim 1, wherein the control
unit has a function for detecting a degree of blockage of a
supply/exhaust flow path, which is a flow path of air for
combustion or combustion exhaust gas, while operating the
combustion fan at a predetermined number of rotations in an
extinguished state of the burner in the ON-OFF combustion control
processing, and is configured to control the combustion fan so as
to change the number of rotations of the combustion fan at the time
of ignition following an extinguished state of the burner according
to the required amount of heat for the temperature control of the
target fluid and the degree of blockage in a case where at least
the degree of blockage is higher than a predetermined value.
3. The combustion device according to claim 1, wherein the control
unit has a function for detecting a degree of blockage of a
supply/exhaust flow path, which is the flow path of air for
combustion or combustion exhaust gas, while operating the
combustion fan at a predetermined number of rotations in an
extinguished state of the burner in the ON-OFF combustion control
processing, and is configured to control, in a case where the
degree of blockage is lower than a predetermined value, the fuel
supply unit and the combustion fan so as to change the amount of a
fuel to be supplied to the burner and the number of rotations of
the combustion fan according to the required amount of heat for the
temperature control of the target fluid at the time of igniting the
burner to restart the combustion operation of the burner after the
burner is extinguished, and to control, in a case where the degree
of blockage is higher than a predetermined value, the fuel supply
unit so as to set the amount of a fuel to be supplied to the burner
at the time of igniting the burner to restart the combustion
operation of the burner after the burner is extinguished to a
predetermined amount, and to control the combustion fan so as to
set the number of rotations of the combustion fan to a number of
rotations set according to the degree of blockage.
4. The combustion device according to claim 1, wherein the control
unit is configured to control, in a case where the ignition of the
burner is not detected at the time of igniting the burner to
restart the combustion operation of the burner after the burner is
extinguished, the fuel supply unit and the combustion fan so as to
increase the amount of fuel to be supplied to the burner and the
number of rotations of the combustion fan as compared with the time
of ignition at which the ignition was not detected.
5. The combustion device according to claim 2, wherein the control
unit is configured to control, in a case where the ignition of the
burner is not detected at the time of igniting the burner to
restart the combustion operation of the burner after the burner is
extinguished, the fuel supply unit and the combustion fan so as to
increase the amount of fuel to be supplied to the burner and the
number of rotations of the combustion fan as compared with the time
of ignition at which the ignition was not detected.
6. The combustion device according to claim 3, wherein the control
unit is configured to control, in a case where the ignition of the
burner is not detected at the time of igniting the burner to
restart the combustion operation of the burner after the burner is
extinguished, the fuel supply unit and the combustion fan so as to
increase the amount of fuel to be supplied to the burner and the
number of rotations of the combustion fan as compared with the time
of ignition at which the ignition was not detected.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a combustion device such as
a water heater and a heating device.
2. Description of the Related Art
[0002] As a combustion device adapted to heat a target fluid
subject to temperature control, such as water for hot water supply
or water for heating, by using the combustion heat of a burner so
as to maintain the temperature of the fluid at a temperature in the
vicinity of a required target temperature, there has conventionally
been known a combustion device that intermittently performs the
combustion operation of a burner (the combustion operation and the
suspension thereof being alternately repeated) when a required
amount of heat necessary for the temperature control of a target
fluid is small, as seen, for example, in Japanese Utility Model
Application No. 59-23555 (hereinafter referred to as Patent
Document 1) or Japanese Patent Application Laid-Open No. 2020-29971
(hereinafter referred to as Patent Document 2). Hereinafter, the
control for intermittently performing the combustion operation of a
burner as described above may be referred to as "the ON-OFF
combustion control" of the burner.
[0003] According to the technologies described in Patent Documents
1 and 2, in the ignition processing for restarting the combustion
operation of the burner while the ON-OFF combustion control of the
burner is being carried out, the amount of a fuel to be supplied to
the burner and the number of rotations of a combustion fan for
supplying air for combustion to the burner are controlled
independently of a required amount of heat for the temperature
control of a target fluid. For this reason, the amount of
combustion heat generated by the burner at the time of ignition to
restart the combustion operation of the burner or immediately after
the ignition tends to be excessive or insufficient with respect to
the required amount of heat.
[0004] In this case, if the amount of heat generated at the time of
ignition of the burner or immediately after the ignition is larger
than the required amount of heat, then the temperature of a target
fluid is apt to overshoot a required target temperature and the
number of rotations of a combustion fan is higher than necessary,
thus frequently causing the operation sound of the combustion fan
to become a noise.
[0005] On the other hand, if the amount of heat generated at the
time of ignition of the burner or immediately after the ignition is
smaller than the required amount of heat, then the rise of the
temperature of the target fluid tends to be delayed or ignition
failure frequently tends to occur.
SUMMARY OF THE INVENTION
[0006] The present invention has been made in view of the
background described above, and an object of the invention is to
provide a combustion device capable of properly performing the
ignition of a burner in the ON-OFF combustion control of the burner
in a manner suited for the temperature control of a target
fluid.
[0007] To this end, a combustion device in accordance with the
present invention includes: a burner which generates heat for
heating a target fluid by a combustion operation; a fuel supply
unit which supplies a fuel to the burner; a combustion fan which
supplies air for combustion to the burner; and a control unit which
has a function for determining a required amount of heat for
temperature control of the target fluid and for controlling the
fuel supply unit and the combustion fan according to the required
amount of heat,
[0008] wherein the control unit is configured to be capable of
performing ON-OFF combustion control processing, which is
processing for controlling the fuel supply unit and the combustion
fan so as to intermittently perform the combustion operation of the
burner, and is also configured to control the fuel supply unit and
the combustion fan so as to change an amount of a fuel to be
supplied to the burner and a number of rotations of the combustion
fan according to a required amount of heat for temperature control
of the target fluid at the time of igniting the burner to restart
the combustion operation of the burner after the burner is
extinguished in the ON-OFF combustion control processing (a first
aspect of the invention).
[0009] In the present invention, the term "temperature control" of
a target fluid means to control the temperature of the target fluid
such that the temperature coincides or substantially coincides with
a required target temperature.
[0010] According to the first aspect of the invention, in the
ON-OFF combustion control processing, the fuel supply unit and the
combustion fan are controlled such that the amount of a fuel to be
supplied to a burner and the number of rotations of the combustion
fan change according to the required amount of heat for the
temperature control of a target fluid when the burner is ignited to
restart the combustion operation of the burner after the burner is
extinguished. This enables the ignition of the burner that can
prevent the temperature of the target fluid from overshooting a
required target temperature or prevent a delay in a temperature
rise of the target fluid at the time of ignition of the burner or
immediately after the ignition.
[0011] Further, when the burner is ignited after being
extinguished, the required amount of heat of the burner does not
increase much, so that the number of rotations of the combustion
fan at the time of ignition can be suppressed to a small number of
rotations, thus making it possible to suppress the operation sound
of the combustion fan when igniting the burner.
[0012] Consequently, according to the first aspect of the
invention, the ignition of a burner in the ON-OFF combustion
control of the burner can be properly performed in a manner suited
to the temperature control of a target fluid.
[0013] In the aforesaid first aspect of the invention, preferably,
the control unit has a function for detecting a degree of blockage
of a supply/exhaust flow path, which is a flow path of air for
combustion or combustion exhaust gas, while operating the
combustion fan at a predetermined number of rotations in an
extinguished state of the burner in the ON-OFF combustion control
processing, and is configured to control the combustion fan so as
to change the number of rotations of the combustion fan at the time
of ignition following the extinguished state of the burner
according to a required amount of heat for the temperature control
of the target fluid and the degree of blockage in the case where at
least the degree of blockage is higher than a predetermined value
(a second aspect of the invention).
[0014] With this arrangement, the degree of blockage of the
supply/exhaust flow path can be properly detected using various
publicly known techniques by operating the combustion fan at a
predetermined number of rotations in the extinguished state of the
burner in the ON-OFF combustion control processing. Further, if at
least the degree of blockage is higher than a predetermined value,
then air for combustion in an amount that meets a required amount
of heat can be supplied to the burner by controlling the combustion
fan as described above, compensating for an influence whereby the
amount of air for combustion to be supplied to the burner tends to
decrease as the degree of blockage of the supply/exhaust flow path
increases. Therefore, even if the blockage of the supply/exhaust
flow path progresses to a certain degree, the burner can be
satisfactorily ignited with a proper required amount of heat.
[0015] In the aforesaid first aspect of the invention, a mode may
be adopted, in which the control unit has a function for detecting
the degree of blockage of the supply/exhaust flow path, which is
the flow path of air for combustion or combustion exhaust gas,
while operating the combustion fan at a predetermined number of
rotations in the extinguished state of the burner in the ON-OFF
combustion control processing, and is configured to control, in the
case where the degree of blockage is lower than a predetermined
value, the fuel supply unit and the combustion fan so as to change
the amount of a fuel to be supplied to the burner and the number of
rotations of the combustion fan according to a required amount of
heat for the temperature control of the target fluid at the time of
igniting the burner to restart the combustion operation of the
burner after the burner is extinguished, and to control, in the
case where the degree of blockage is higher than a predetermined
value, the fuel supply unit so as to set the amount of a fuel to be
supplied to the burner at the time of igniting the burner to
restart the combustion operation of the burner after the burner is
extinguished to a predetermined amount, and to control the
combustion fan so as to set the number of rotations of the
combustion fan to a number of rotations set according to the degree
of blockage (a third aspect of the invention).
[0016] With this arrangement, as with the second aspect of the
invention, the degree of blockage of the supply/exhaust flow path
can be properly detected using various publicly known techniques by
operating the combustion fan at a predetermined number of rotations
in the extinguished state of the burner in the ON-OFF combustion
control processing. Further, when the degree of blockage is lower
than a predetermined value, the effect described in the first
aspect of the invention can be obtained by controlling the fuel
supply unit and the combustion fan as with the first aspect of the
invention.
[0017] Further, if the degree of blockage of the supply/exhaust
flow path is higher than a predetermined value, then the fuel
supply unit is controlled to set the amount of a fuel, which is
supplied to the burner at the time of igniting the burner when
restarting the combustion operation of the burner after the burner
is extinguished, to a predetermined amount, and the combustion fan
is controlled to set the number of rotations of the combustion fan
to a number of rotations set according to the degree of blockage,
thereby making it possible to stably and satisfactorily ignite the
burner, compensating for the influence that the amount of air for
combustion to be supplied to the burner tends to decrease as the
degree of blockage of the supply/exhaust flow path increases.
[0018] In the first aspect of the invention, the control unit is
preferably configured to control, in the case where the ignition of
the burner is not detected at the time of igniting the burner to
restart the combustion operation of the burner after the burner is
extinguished, the fuel supply unit and the combustion fan so as to
increase the amount of a fuel to be supplied to the burner and the
number of rotations of the combustion fan as compared with the time
of ignition at which the ignition was not detected (a fourth aspect
of the invention). The same applies to the second aspect of the
invention and the third aspect of the invention described above (a
fifth aspect of the invention and a sixth aspect of the
invention).
[0019] With this arrangement, if a misfire occurs due to ignition
failure at the time of ignition after the burner is extinguished in
the ON-OFF combustion control processing, then the amount of a fuel
to be supplied to the burner and the number of rotations of the
combustion fan are increased before reigniting the burner, so that
the reliability of proper ignition of the burner by the reignition
can be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a diagram schematically illustrating the overall
configuration of a water heater as an example of a combustion
device of an embodiment;
[0021] FIG. 2 is a flowchart illustrating the processing in a first
embodiment of the control unit illustrated in FIG. 1; and
[0022] FIG. 3 is a flowchart illustrating the processing in a
second embodiment of the control unit illustrated in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0023] A first embodiment of the present invention will be
described below with reference to FIG. 1 and FIG. 2. Referring to
FIG. 1, a water heater 1 of the present embodiment has a heat
source unit 2 installed outdoors. A combustion casing 3 having a
combustion chamber 3a formed therein is installed in the heat
source unit 2. Burners 4 as heating units are disposed at a lower
part of the combustion chamber 3a in the combustion casing 3.
[0024] The burners 4 are gas burners in the present embodiment. The
burners 4 are composed of a plurality of burners, e.g., three types
of burners, namely, first burners 4a, second burners 4b, and third
burners 4c that can separately perform a combustion operation. In
the illustrated example, the first burners 4a, the second burners
4b, and the third burners 4c have different combustion areas from
each other. However, the combustion area of each of two or more
burners constituting the burners 4 may be the same.
[0025] The heat source unit 2 includes a fuel supply unit 5 for
supplying a fuel gas to the burners 4. The fuel supply unit 5 has a
main gas supply line 6, to which a fuel gas is supplied from a gas
supply source (not illustrated) and three secondary gas supply
lines 6a. 6b, and 6c branched from the main gas supply line 6. Each
of the secondary gas supply lines 6a, 6b, and 6c is introduced into
the combustion chamber 3a from outside the combustion casing 3 such
that a fuel gas can be supplied separately to the first burners 4a,
the second burners 4b, and the third burners 4c.
[0026] The fuel supply unit 5 further includes a main valve 7
interposed in the main gas supply line 6 such that the main gas
supply line 6 can be opened and closed, a gas amount regulating
valve 8 interposed in the main gas supply line 6 such that the
amount of a fuel gas to be supplied to the burners 4 can be
adjusted, and switching valves 9a, 9b, and 9c interposed in the
secondary gas supply lines 6a. 6b, and 6c, respectively, such that
each of the secondary gas supply lines 6a. 6b, and 6c can be opened
and closed. Each of the main valve 7 and the switching valves 9a.
9b, and 9c is composed of, for example, a solenoid valve. The gas
amount regulating valve 8 is composed of, for example, a
proportional valve or an electric flow control valve.
[0027] In the present embodiment, the fuel supply unit 5 is
configured as described above, so that the total amount of
combustion heat of the burners 4 can be changed over an extensive
range by changing the combination of the open/closed state of each
of the switching valves 9a. 9b, and 9c, with the main valve 7
controlled to be open, when performing the combustion operations of
the burners 4. The burners 4 are not limited to burners composed of
a plurality of burners, the combustion operations of which can be
separately performed, and may be configured such that all of the
burners 4 perform combustion operations at the same time. In other
words, a fuel gas may be supplied from a single gas supply line to
all of the burners 4.
[0028] Further, the heat source unit 2 includes an electric
combustion fan 10 as an air blower for supplying air for combustion
to the burners 4. The combustion fan 10 is installed at the bottom
of the combustion casing 3 such that outside air serving as the air
for combustion can be taken in and the air taken in can be supplied
to the burners 4 (all the first to the third burners 4a, 4b and 4c)
by the rotation operation of the combustion fan 10. In addition,
the amount of the air for combustion to be supplied to the burners
4 can be changed by variably controlling the number of rotations
(rotation speed) of the combustion fan 10.
[0029] An exhaust port 3b for exhausting the combustion exhaust gas
of the burners 4 from the combustion chamber 3a is opened at an
upper part of the combustion casing 3. The exhaust port 3b is in
communication with the outside of the heat source unit 2 through an
exhaust passage (not illustrated). Further installed to the
combustion casing 3 are an ignition electrode 12 that generates a
spark discharge to ignite the burners 4 by activating an igniter
(not illustrated) mounted on the heat source unit 2, and a flame
detection sensor 13 for detecting the presence of a combustion
flame of the burners 4. The flame detection sensor 13 is composed
of, for example, a flame rod, a thermocouple, or the like.
[0030] The heat source unit 2 is provided with a configuration
related to the water flow for the water for hot water supply as a
target fluid (fluid to be heated) in addition to the aforesaid
configuration related to the combustion operation of the burners 4.
More specifically, the combustion chamber 3a in the combustion
casing 3 is provided with a heat exchanger 21 placed such that the
heat exchanger 21 can be heated by the combustion heat of the
burners 4. Further, a water flow passage 22 through which water can
flow via the heat exchanger 21 is provided.
[0031] The water flow passage 22 is connected to the inlet of a
water flow passage 21a of the heat exchanger 21, and includes a
water supply passage 22a through which water for hot water supply
is supplied from a water supply source (not illustrated), a hot
water supply passage 22b connected to the outlet of the water flow
passage 21a of the heat exchanger 21, and a bypass passage 22c that
connects the water supply passage 22a to the hot water supply
passage 22b such that the water for hot water supply can be
circulated to the hot water supply passage 22b from the water
supply passage 22a, bypassing the heat exchanger 21. Further, the
downstream side of the hot water supply passage 22b is disposed
such that the water for hot water supply can be supplied to a hot
water supply target (a faucet or the like), which is not
illustrated, in a kitchen, a washroom, a bathroom, or the like.
[0032] Thus, the water flow passage 22 is configured such that the
hot water obtained by combining, in the hot water supply passage
22b, the water for hot water supply that has been heated passing
through the heat exchanger 21 from the water supply passage 22a,
and the water for hot water supply passing through the bypass
passage 22c from the water supply passage 22a can be supplied from
the hot water supply passage 22b to a hot water supply target
during the combustion operation of the burners 4.
[0033] In the water supply passage 22a, an electric water amount
control valve 23 for adjusting the supply water flow rate, which is
the flow rate of water flow of the water supply passage 22a, and a
water amount sensor 24 that detects the supply water flow rate are
provided on the upstream side of a branched part of the bypass
passage 22c. Further, the hot water supply passage 22b is provided
with a temperature sensor 25 that detects a hot water supply
temperature, which is the temperature of water for hot water supply
to be supplied to a hot water supply target (the temperature of hot
water flowing toward the downstream side from a part connecting the
bypass passage 22c and the hot water supply passage 22b), and a
temperature sensor 26 that detects the temperature of heat
exchanger discharged hot water, which is the temperature of the
water for hot water supply that flows out from the heat exchanger
21 to the hot water supply passage 22b.
[0034] A control valve for adjusting the ratio between the flow
rate of the water for hot water supply flowing via the bypass
passage 22c and the flow rate of the water for hot water supply
that passes through the water flow passage 21a of the heat
exchanger 21 (so-called bypass ratio) may be provided at, for
example, a part connecting the bypass passage 22c and the water
supply passage 22a or the hot water supply passage 22b, or in the
middle of the bypass passage 22c. Further, one or both of the water
amount control valve 23 and the water amount sensor 24 may be
provided, for example, in the hot water supply passage 22b on the
downstream side with respect to the part connecting the hot water
supply passage 22b and the bypass passage 22c.
[0035] A description will now be given of the configuration related
to the operation control of the water heater 1 (including the
combustion operation control of the burners 4). The water heater 1
includes a control unit 30 having a function for controlling the
operation thereof, and a remote controller 40 for operating the
water heater 1.
[0036] The remote controller 40 is a terminal installed in a
kitchen, bathroom, or the like, and is provided with a plurality of
operation switches, indicators, and the like (not illustrated). The
remote controller 40 may have a publicly known configuration. By
operating the operation switches of the remote controller 40, it is
possible to perform operations, including the turning ON/OFF of the
hot water supply of the water heater 1, and setting the target
value of a hot water supply temperature (hereinafter referred to as
a target hot water supply temperature). The water heater 1 may be
provided with a plurality of remote controllers including the
remote controller 40.
[0037] The control unit 30 is composed of one or more electronic
circuit units that include processors, such as microcomputers,
memories (RAMs. ROMs. and the like), interface circuits, and the
like (not illustrated), and is installed in the heat source unit 2.
The control unit 30 is capable of communicating with the remote
controller 40 in a wired or wireless manner, and receives the
operation information of the remote controller 40 (on/off signals
of the hot water supply operation, set values of the target hot
water supply temperature, and the like) by this communication. In
addition, the control unit 30 receives the detection signals of
sensors (including the flame detection sensor 13, the water amount
sensor 24, and temperature sensors 25 and 26 described above)
provided in the water heater 1.
[0038] Further, the control unit 30 has a function for controlling
the combustion operation of the burners 4 as a function for
implementing one or both of installed hardware configuration and
program (software configuration). The combustion operation of the
burners 4 is controlled through the main valve 7, the gas amount
regulating valve 8, the switching valves 9a. 9b, and 9c, and the
combustion fan 10 and through the operation control of an ignitor
(not illustrated).
[0039] The operation of the water heater 1 of the present
embodiment will now be described. The control unit 30 monitors the
presence of a water flow in the water flow passage 22 on the basis
of an output of the water amount sensor 24, and causes the burners
4 to perform the combustion operation upon detection of the
occurrence of a water flow of a predetermined flow rate or more in
the water flow passage 22. In this case, the control unit 30
performs the temperature control of the water for hot water supply
such that the hot water supply temperature detected by the
temperature sensor 25 coincides or substantially coincides with a
target hot water supply temperature set by the remote controller 40
by controlling the combustion heat amount of the burners 4 after
igniting the burners 4.
[0040] In the temperature control, the control unit 30 selectively
performs continuous combustion control processing as the control
processing for continuously performing the combustion operation of
the burners 4 and the ON-OFF combustion control processing as the
control processing for intermittently performing combustion
operation of the burners 4 (alternately repeating the combustion
operation of the burners 4 and the suspension thereof).
[0041] According to the present embodiment, the control unit 30
performs the continuous combustion control processing if, for
example, a set target hot water supply temperature is a
predetermined temperature or higher, or the required amount of
heat, which indicates the required value of the combustion heat
amount of the burners 4 for the temperature control of the water
for hot water supply is a predetermined value or more. Further, the
control unit 30 performs the ON-OFF combustion control processing
if a set target hot water supply temperature is lower than a
predetermined temperature, or the required amount of heat of the
burners 4 for the temperature control of the water for hot water
supply is lower than a predetermined value.
[0042] In the continuous combustion control processing, the control
unit 30 sequentially determines, after the burners 4 are ignited,
the required amount of heat of the burners 4 primarily on the basis
of the detection values of the temperature of the water for hot
water supply detected by the temperature sensors 25 and 26, and the
detection value of the flow rate of the water flow for hot water
supply detected by the water amount sensor 24, performs control of
opening/closing the switching valves 9a, 9b, and 9c of the fuel
supply unit 5 according to the determined required amount of heat,
and also controls the amount of a fuel gas and the amount of air
for combustion to be supplied to the burners 4 so as to achieve the
required amount of heat by the combustion operation of the burners
4 at a required air-fuel ratio. In this case, the supply amount of
a fuel gas is controlled by controlling the gas amount regulating
valve 8, and the supply amount of the air for combustion is
controlled by controlling the number of rotations of the combustion
fan 10.
[0043] Meanwhile, the ON-OFF combustion control processing is
performed according to the flowchart of FIG. 2 if a water flow (a
water flow of a predetermined flow rate or more) in the water flow
passage 22 is started in a state in which the target hot water
supply temperature has been set to be lower than a predetermined
temperature, or if the target hot water supply temperature is
changed to a temperature that is lower than a predetermined
temperature during the combustion operation of the burners 4 by the
continuous combustion control processing, or if the required amount
of heat of the burners 4 becomes lower than a predetermined value
due to a change of the target hot water supply temperature, or the
like.
[0044] More specifically, the control unit 30 determines in STEP1
whether the burners 4 are performing the combustion operation, and
if a result of the determination is affirmative, then the control
unit 30 performs the processing from STEP13, which will be
described later. Further, if the result of the determination in
STEP1 is negative, then the control unit 30 sequentially repeats in
STEP2 the processing for determining whether there is a request for
igniting the burners 4 until the determination result becomes
affirmative.
[0045] In this case, for example, if it is confirmed that the water
heater 1 has no abnormality in initial check processing immediately
after a water flow of a predetermined flow rate or more is started
in the water flow passage 22, then the determination result of
STEP2 becomes affirmative. At this time, the control unit 30
drives, in STEP3, the combustion fan 10 at a predetermined small
number of rotations for purging the combustion chamber 3a. Then,
the control unit 30 determines whether the degree of blockage of
the supply/exhaust flow path (the air supply path or the exhaust
path) in communication with the combustion chamber 3a is higher
than a predetermined threshold value while the combustion fan 10 is
operating.
[0046] Here, according to the present embodiment, the control unit
30 acquires, in STEP4, a detection value of a fan current, which is
the energizing current of an electric motor (not illustrated) that
drives the combustion fan 10 through a current sensor (not
illustrated) as an index value that indicates the degree of
blockage of the supply/exhaust flow path. The detection value of
the fan current decreases as the degree of blockage of the
supply/exhaust flow path increases. Further, if the detection value
of the fan current is smaller than a predetermined value, then the
control unit 30 determines that the determination result of STEP4
is affirmative, and if the detection value of the fan current is
equal to or greater than the predetermined value, then the control
unit 30 determines that the determination result of STEP4 is
negative.
[0047] Whether the degree of blockage of the supply/exhaust flow
path is high or low may be determined using other methods. For
example, the air volume or pressure in the supply/exhaust flow path
can be detected, and the degree of blockage of the supply/exhaust
flow path can be determined by using the detection values.
[0048] If the determination result of STEP4 is negative, then in
STEP5, the control unit 30 calculates the required amount of heat
of the burners 4 for the temperature control of the water for hot
water supply and also determines, according to the required amount
of heat, the ignition number of rotations for the ON-OFF
combustion, which is a target number of rotations of the combustion
fan 10 when igniting the burners 4 while the ON-OFF combustion
control processing of the burners 4 is being performed. The
ignition number of rotations for the ON-OFF combustion is
determined on the basis of the required amount of heat by using a
map prepared in advance or an arithmetic expression. In this case,
the ignition number of rotations for the ON-OFF combustion is
determined such that the ignition number of rotations increases
within the range from a predetermined lower limit value to a
predetermined upper limit value as the required amount of heat
increases.
[0049] The control unit 30 further determines in STEP7 whether the
burners 4 were burning immediately before (in other words, whether
the burners 4 were in suspension of the combustion operation in the
ON-OFF combustion control processing). In this case, the
determination result of STEP7 becomes negative when the first
(initial) combustion operation of the burners 4 is started in the
ON-OFF combustion control processing. At this time, the control
unit 30 performs the ignition processing of the burners 4 in
STEP8.
[0050] In the ignition processing, the control unit 30 activates
the combustion fan 10 at a normal ignition number of rotations. The
normal ignition number of rotations is the same as the number of
rotations of the combustion fan 10 in the ignition processing of
the burners 4 when the continuous combustion control processing is
started. The number of rotations is a predetermined number of
rotations established in advance and lies between a number of
rotations corresponding to a minimum required amount of heat and a
number of rotations corresponding to a maximum required amount of
heat in the continuous combustion control processing.
[0051] In the ignition processing of STEP8, the control unit 30
further activates an ignitor (not illustrated) while performing the
control for opening the main valve 7 and the switching valve 9a and
the control of the gas amount regulating valve 8 so as to supply a
fuel gas in a predetermined flow rate corresponding to the normal
ignition number of rotations of the combustion fan 10 to
predetermined burners for the ON-OFF combustion control processing,
e.g., the first burners 4a, among the burners 4. In this case, a
control value of the gas amount regulating valve 8 that corresponds
to the fuel gas in the predetermined flow rate is established in
advance.
[0052] Thus, a spark discharge is generated at the ignition
electrode 12 to ignite the burners 4 while the air for combustion
in a flow rate corresponding to the normal ignition number of
rotations of the combustion fan 10 and a fuel gas in a flow rate
corresponding to the ignition number of rotations are being
supplied to the burners 4.
[0053] Further, the determination result of STEP7 becomes
affirmative at a start of the combustion operation of the burners 4
in each cycle from the second time and after in the ON-OFF
combustion control processing. At this time, the control unit 30
performs the ignition processing of the burners 4 in STEP9.
[0054] In the ignition processing, the control unit 30 activates
the combustion fan 10 at the ignition number of rotations for the
ON-OFF combustion determined in STEP5. Further, the control unit 30
activates the ignitor (not illustrated) while performing the
control for opening the main valve 7 and the switching valve 9a and
the control of the gas amount regulating valve 8 so as to supply
the fuel gas in the flow rate corresponding to the ignition number
of rotations for the ON-OFF combustion of the combustion fan 10 to
the burners (the first burners 4a) for the ON-OFF combustion
control processing among the burners 4. In this case, the control
value of the gas amount regulating valve 8 corresponding to the
flow rate of the fuel gas to be supplied to the burners 4 is
determined by a map, an arithmetic expression, or the like
according to the ignition number of rotations for the ON-OFF
combustion of the combustion fan 10 or the required amount of heat
of the burners 4.
[0055] Thus, a spark discharge is generated at the ignition
electrode 12 to ignite the burners 4 while the air for combustion
in a flow rate corresponding to the ignition number of rotations
for the ON-OFF combustion of the combustion fan 10 and a fuel gas
in a flow rate corresponding to the ignition number of rotations
are being supplied to the burners 4. The flow rates of the air for
combustion and the fuel gas to be supplied to the burners 4 in the
ignition processing of STEP9 are smaller than the flow rates of the
air for combustion and the fuel gas to be supplied to the burners 4
in the ignition processing of STEP8.
[0056] If the determination result of the aforesaid STEP4 is
affirmative (if it is determined that the degree of blockage of the
supply/exhaust flow path is higher than a predetermined threshold
value), then the control unit 30 determines, in STEP6, an ignition
number of rotations obtained by correcting the normal ignition
number of rotations of the combustion fan 10 described above
according to the degree of blockage of the supply/exhaust flow path
(a detection value of the fan current as an index value indicating
the degree of blockage in the present embodiment).
[0057] In this case, the control unit 30 corrects the normal
ignition number of rotations according to a detection value of the
fan current so as to increase the ignition number of rotations
after the correction to be greater than the normal ignition number
of rotations as the degree of blockage of the supply/exhaust flow
path increases (as the detection value of the fan current
decreases). As a method for the correction, for example, the method
disclosed by the applicant of the present application in Japanese
Patent Application Laid-Open No. 2017-129313 can be adopted.
[0058] Then, the control unit 30 further performs the ignition
processing of the burners 4 in STEP10. In the ignition processing,
the control unit 30 activates the combustion fan 10 at the
corrected ignition number of rotations determined in STEP6.
Further, the control unit 30 activates an ignitor (not illustrated)
while performing the control for opening the main valve 7 and the
switching valve 9a and the control of the gas amount regulating
valve 8 so as to supply the fuel gas in the flow rate corresponding
to the normal ignition number of rotations of the combustion fan 10
(the fuel gas in the same flow rate as that of the ignition
processing in STEP8) to the burner for the ON-OFF combustion
control processing (the first burners 4a) among the burners 4. In
this case, the control value of the gas amount regulating valve 8
that corresponds to the flow rate of the fuel gas to be supplied to
the burners 4 is the same as the control value in STEP8. Thus, a
spark discharge is generated at the ignition electrode 12 to ignite
the burners 4 while the air for combustion and the fuel gas in the
flow rates equivalent to those of the ignition processing in STEP8
are being supplied to the burners 4.
[0059] The control unit 30 determines in STEP11 whether the burners
4 have been ignited on the basis of an output of the flame
detection sensor 13 while performing the ignition processing in
STEP8 or STEP9 or STEP10 as described above. Further, if the
determination result of STEP1 is negative, then the control unit 30
increases the ignition number of rotations of the combustion fan 10
by a predetermined amount from a current number of rotations and
performs the ignition processing of the burners 4 again in STEP12.
Further, the control unit 30 performs the determination processing
of STEP11. In this case, the control unit 30 controls the gas
amount regulating valve 8 so as to also increase the amount (the
flow rate) of the fuel gas to be supplied to the burners 4 (the
first burners 4a) by a predetermined amount in STEP12.
[0060] If the ignition of the burners 4 is not detected in STEP11
even after the ignition processing in STEP12 is performed by a
predetermined number of times, then the control unit 30 suspends
the control of the combustion operation of the burners 4 and
outputs information indicating the occurrence of an abnormality
through the remote controller 40.
[0061] If the burners 4 are ignited and the determination result of
STEP11 becomes affirmative (if the combustion operation of the
burners 4 is started by the ignition processing of any one of STEPs
8, 9, 10, and 12), or if the determination result of STEP1 is
affirmative (if the burners 4 are already in the combustion
operation), then the control unit 30 sequentially performs, in
STEP13, the processing for determining whether the hot water supply
temperature detected by the temperature sensor 25 has increased to
a temperature that is higher than a first threshold value
temperature TH1, which has been set to be higher than a target hot
water supply temperature by a predetermined value, until the
determination result becomes affirmative.
[0062] Further, if the determination result of STEP13 becomes
affirmative, then the control unit 30 performs the extinguishment
processing of the burners 4 (the first burners 4a) and also drives
the combustion fan 10 at a predetermined small number of rotations
for purging the combustion chamber 3a in STEP14. In this case, in
the extinguishment processing of the burners 4, the control unit 30
performs the control for closing the switching valve 9a (or the
main valve 7) corresponding to the first burners 4a, which perform
the combustion operation in the ON-OFF combustion control
processing, thereby cutting off the supply of the fuel gas to the
first burners 4a.
[0063] Further, while operating the combustion fan 10 at the small
number of rotations for purging as described above, the control
unit 30 sequentially performs, in STEP15, the processing for
determining whether the hot water supply temperature detected by
the temperature sensor 25 has decreased to a temperature that is
lower than a second threshold value temperature TH2, which has been
set to be lower than the target hot water supply temperature by a
predetermined value, until the determination result becomes
affirmative. Further, if the determination result of STEP15 becomes
affirmative, then the control unit 30 restarts the processing from
the aforesaid STEP4.
[0064] In the present embodiment, the ON-OFF combustion control
processing is performed as described above. In this case, if the
degree of blockage of the supply/exhaust flow path is low, then
control is performed such that the ignition number of rotations of
the combustion fan 10 and the amount (the flow rate) of the fuel
gas to be supplied to the burners 4 in the ignition processing of
the burners 4 from the second time and after changes according to
the required amount of heat of the burners 4 (increases as the
required amount of heat increases). As a result, it is possible to
suppress the occurrence of overshoot of the hot water supply
temperature with respect to a target hot water supply temperature
or excessive delay of temperature rise to the target hot water
supply temperature. Consequently, the hot water supply temperature
can be stably maintained at a temperature in the vicinity of the
target hot water supply temperature.
[0065] Further, in the ignition processing of the burners 4 from
the second time and after, the required amount of heat of the
burners 4 is normally small, so that the ignition number of
rotations of the combustion fan 10 in the ignition processing can
be suppressed to a lower number of rotations. Consequently, the
operation sound of the combustion fan 10 in the ignition processing
of the burners 4 from the second time and after can be
suppressed.
[0066] Further, if the degree of blockage of the supply/exhaust
flow path is high, then the ignition processing in STEP10 is
performed, so that the reliability of the ignition of the burners 4
being properly performed can be enhanced.
[0067] In addition, if the ignition of the burners 4 is not
detected in STEP11, then the number of rotations of the combustion
fan 10 and the amount of the fuel gas to be supplied to the burners
4 are increased before the ignition processing of the burners 4 is
performed again, so that the reliability of the reignition of the
burners 4 being properly performed can be enhanced.
Second Embodiment
[0068] A description will now be given of a second embodiment of
the present invention with reference to FIG. 3. The present
embodiment differs from the first embodiment only partly in the
control processing by a control unit 30, so that the same matters
as those of the first embodiment will not be described.
[0069] In the present embodiment, the ON-OFF combustion control
processing by the control unit 30 is performed as illustrated by
the flowchart of FIG. 3. In this case, according to the present
embodiment, if the determination result of STEP4 is affirmative (if
the degree of blockage of the supply/exhaust flow path is higher
than a predetermined threshold value), then the control unit 30
performs the processing of STEP6x instead of the processing of
STEP6 and STEP10 in the first embodiment, and then performs the
processing from STEP7 as with the first embodiment.
[0070] In the aforesaid STEP6x, the control unit 30 determines the
ignition number of rotations for the ON-OFF combustion according to
the required amount of heat of the burners 4 for the temperature
control of the water for hot water supply and the degree of
blockage of the supply/exhaust flow path. More specifically, the
control unit 30 determines a reference ignition number of rotations
for the ON-OFF combustion by the same processing as the processing
of STEP5. Further, the control unit 30 corrects the reference
ignition number of rotations according to the degree of blockage of
the supply/exhaust flow path (according to the detection value of a
fan current in the present embodiment), thereby determining the
ignition number of rotations used for the actual control of the
combustion fan 10. In this case, the ignition number of rotations
is corrected such that a corrected ignition number of rotations
will be a number of rotations that is higher than the reference
ignition number of rotations as the degree of blockage of the
supply/exhaust flow path becomes higher.
[0071] In STEP6x, the ignition number of rotations of the
combustion fan 10 may alternatively be determined by using a map or
the like on the basis of the required amount of heat of the burners
4 and the degree of blockage of the supply/exhaust flow path (the
detection value of a fan current in the present embodiment).
[0072] The present embodiment is the same as the aforesaid first
embodiment except for the matters described above. According to the
present embodiment, the amount (the flow rate) of the fuel gas to
be supplied to the burners 4 and the number of rotations of the
combustion fan 10 at the time of ignition of the burners 4 from the
second time and after in the ON-OFF combustion control processing
are controlled to a supply amount and a number of rotations that
meet a required amount of heat of the burners 4 not only in the
case where the degree of blockage of the supply/exhaust flow path
is low but also in a situation in which the degree of blockage
becomes higher to a certain degree.
[0073] Consequently, the hot water supply temperature can be stably
maintained at a temperature in the vicinity of a target hot water
supply temperature, and the operation sound of the combustion fan
10 at the time of ignition from the second time and after in the
ON-OFF combustion control processing can be suppressed. Further, in
a state in which the degree of blockage of the supply/exhaust flow
path becomes higher to a certain degree, the ignition number of
rotations of the combustion fan 10 is set to a number of rotations
obtained by correcting the reference ignition number of rotations
as described above. This makes it possible to satisfactorily ignite
the burners 4 from the second time and after, as with the case
where the degree of blockage of the supply/exhaust flow path is
low.
[0074] In addition, if the ignition of the burners 4 is not
detected in the aforesaid STEP11, then the number of rotations of
the combustion fan 10 and the amount of a fuel gas to be supplied
to the burners 4 are increased before the ignition processing of
the burners 4 is performed again, as with the first embodiment, so
that the reliability of the burners 4 being properly reignited can
be enhanced.
Other Embodiments
[0075] The present invention is not limited to the first embodiment
or the second embodiment described above, and other embodiments can
be adopted. For example, the combustion device according to the
present invention is not limited to a water heater, which heats
water for hot water supply as a target fluid, and may be a
combustion device that heats, for example, a heat medium (a liquid
or a gas) for heating as a target fluid. Further, a fuel of the
burners 4 is not limited to a fuel gas, and may alternatively be a
liquid fuel, such as kerosene.
* * * * *