U.S. patent application number 17/375006 was filed with the patent office on 2022-01-27 for combustion apparatus.
This patent application is currently assigned to NORITZ CORPORATION. The applicant listed for this patent is NORITZ CORPORATION. Invention is credited to Yusuke Abe, Eiji Kanki, Makoto Kusakabe, Shota Mizuno.
Application Number | 20220026066 17/375006 |
Document ID | / |
Family ID | 1000005770345 |
Filed Date | 2022-01-27 |
United States Patent
Application |
20220026066 |
Kind Code |
A1 |
Abe; Yusuke ; et
al. |
January 27, 2022 |
COMBUSTION APPARATUS
Abstract
A combustion apparatus includes a combustion part, a blower fan,
an ignition device, and a control part. The control part
selectively performs continuous combustion in which the combustion
part is operated to burn continuously and intermittent combustion
in which a combustion period and a non-combustion period of the
combustion part are repeatedly provided. When the continuous
combustion is stopped, the control part extinguishes the combustion
part and operates the blower fan to perform a scavenging operation.
When the combustion period in the intermittent combustion is ended,
the control part extinguishes the combustion part and operates the
blower fan to perform a scavenging operation in the non-combustion
period. A total air blowing amount of the blower fan in the
scavenging operation during the non-combustion period is set to be
less than a total air blowing amount of the blower fan in the
scavenging operation when the continuous combustion is stopped.
Inventors: |
Abe; Yusuke; (HYOGO, JP)
; Kusakabe; Makoto; (HYOGO, JP) ; Mizuno;
Shota; (HYOGO, JP) ; Kanki; Eiji; (HYOGO,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NORITZ CORPORATION |
Hyogo |
|
JP |
|
|
Assignee: |
NORITZ CORPORATION
Hyogo
JP
|
Family ID: |
1000005770345 |
Appl. No.: |
17/375006 |
Filed: |
July 14, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24H 1/145 20130101;
F23N 3/002 20130101; F24H 9/2035 20130101; F23N 5/203 20130101 |
International
Class: |
F23N 3/00 20060101
F23N003/00; F24H 9/20 20060101 F24H009/20; F23N 5/20 20060101
F23N005/20 |
Claims
1. A combustion apparatus, comprising: a combustion part for
burning a fuel; a blower fan that blows an air to the combustion
part; an ignition device for igniting the combustion part; and a
control part that controls operations of the combustion part, the
blower fan, and the ignition device, wherein the control part is
configured to selectively perform a continuous combustion in which
the combustion part is operated to burn continuously and an
intermittent combustion in which a combustion period and a
non-combustion period of the combustion part are repeatedly
provided, when the continuous combustion is stopped, the control
part extinguishes the combustion part and operates the blower fan
to perform a scavenging operation, when the combustion period in
the intermittent combustion is ended, the control part extinguishes
the combustion part and operates the blower fan to perform a
scavenging operation in the non-combustion period, and a total air
blowing amount of the blower fan in the scavenging operation during
the non-combustion period is set to be less than a total air
blowing amount of the blower fan in the scavenging operation when
the continuous combustion is stopped.
2. The combustion apparatus according to claim 1, wherein when the
continuous combustion is stopped, the control part performs: a
first scavenging operation in which the blower fan is operated at a
first rotation speed for a first time, and a second scavenging
operation in which the blower fan is operated at a second rotation
speed for a second time; wherein the total air blowing amount of
the blower fan in the scavenging operation during the
non-combustion period is set to be: greater than or equal to a
total air blowing amount of the blower fan in the first scavenging
operation, and less than a total value of the total air blowing
amount of the blower fan in the first scavenging operation and a
total air blowing amount of the blower fan in the second scavenging
operation.
3. The combustion apparatus according to claim 1, wherein when the
continuous combustion is stopped, the control part performs: a
first scavenging operation in which the blower fan is operated at a
first rotation speed for a first time, and a second scavenging
operation in which the blower fan is operated at a second rotation
speed for a second time, wherein during the non-combustion period,
the control part performs only the first scavenging operation.
4. The combustion apparatus according to claim 1, wherein the
combustion apparatus is installed in a hot water supplier, and the
hot water supplier comprises: a heating flow path that passes
through a heat exchanger for heating a low-temperature water by a
heat amount generated by the combustion part; and a temperature
detector that detects a temperature of a high-temperature water
output from the heat exchanger, wherein in the intermittent
combustion, the control part switches between the combustion period
and the non-combustion period according to a comparison between a
detection temperature of the temperature detector and a target
temperature range.
5. The combustion apparatus according to claim 4, wherein in the
intermittent combustion, the control part extinguishes the
combustion part when the detection temperature becomes greater than
an upper limit value of the target temperature range in the
combustion period and ignites the combustion part when the
detection temperature becomes less than a lower limit value of the
target temperature range in the non-combustion period.
6. The combustion apparatus according to claim 1, wherein the
control part performs the intermittent combustion when a required
heat generation amount is less than a lower limit value of a heat
generation amount range of the continuous combustion.
7. The combustion apparatus according to claim 2, wherein when the
continuous combustion is stopped, the control part performs: a
first scavenging operation in which the blower fan is operated at a
first rotation speed for a first time, and a second scavenging
operation in which the blower fan is operated at a second rotation
speed for a second time, wherein during the non-combustion period,
the control part performs only the first scavenging operation.
8. A combustion apparatus, comprising: a combustion part for
burning a fuel; a blower fan that blows an air to the combustion
part; an ignition device for igniting the combustion part; and a
control part that controls operations of the combustion part, the
blower fan, and the ignition device, wherein the control part is
configured to perform an intermittent combustion in which a
combustion period and a non-combustion period of the combustion
part are repeatedly provided, when the intermittent combustion is
stopped, the control part extinguishes the combustion part and
operates the blower fan to perform a scavenging operation, when the
combustion period in the intermittent combustion is ended, the
control part extinguishes the combustion part and operates the
blower fan to perform a scavenging operation in the non-combustion
period, and a total air blowing amount of the blower fan in the
scavenging operation during the non-combustion period is set to be
less than a total air blowing amount of the blower fan in the
scavenging operation when the intermittent combustion is stopped.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Japan
application serial no. 2020-124994, filed on Jul. 22, 2020. The
entirety of the above-mentioned patent application is hereby
incorporated by reference herein and made a part of this
specification.
BACKGROUND
Technical Field
[0002] The disclosure relates to a combustion apparatus.
Description of Related Art
[0003] Japanese Patent Laid-Open No. H09-170813A (Patent Document
1) discloses a forced air supply type hot water dispenser including
a gas burner, a heat exchanger that is heated by the gas burner to
convert cold water into hot water, and an air supply fan that
supplies combustion air for the gas burner to a combustion chamber.
In Patent Document 1, after the hot water supply is stopped, the
air supply fan is continuously operated for a certain period of
time to perform post-purge. As a result, post-boiling due to the
temperature rise around the heat exchanger after the hot water
supply is stopped is suppressed, and unexpected high-temperature
water is prevented from being output when the hot water is
re-supplied during intermittent use.
RELATED ART
Patent Document
[0004] [Patent Document 1] Japanese Patent Laid-open No.
H09-170813A
SUMMARY
Technical Problem
[0005] However, during the application of intermittent combustion
with repeated combustion and non-combustion periods of the burner,
while performing the post-purge described above each time the
combustion period is ended can prevent unexpected high-temperature
hot water from being output when the next combustion period starts,
the temperature drop of hot water is accelerated by cooling the
heat exchanger after the combustion is stopped, so the
non-combustion period until the start of the next combustion period
may be shortened. As a result, the cycle length corresponding to
the sum of each combustion period and non-combustion period is
shortened, and the ignition and extinguishing of the burner are
frequently repeated.
[0006] Since thermal stress is frequently applied to equipment such
as the heat exchanger when the burner is ignited and extinguished,
there is a concern that fatigue failure of the equipment will be
increased and a problem will occur in the equipment durability.
[0007] The disclosure has been made to solve such a problem, and
the disclosure provides a combustion apparatus capable of
suppressing frequent switching between a combustion period and a
non-combustion period when intermittent combustion is applied.
Solution to the Problem
[0008] According to an aspect of the disclosure, a combustion
apparatus includes a combustion part for burning a fuel, a blower
fan that blows an air to the combustion part, an ignition device
for igniting the combustion part, and a control part that controls
operations of the combustion part, the blower fan, and the ignition
device. The control part is configured to selectively perform a
continuous combustion in which the combustion part is operated to
burn continuously and an intermittent combustion in which a
combustion period and a non-combustion period of the combustion
part are repeatedly provided. When the continuous combustion is
stopped, the control part extinguishes the combustion part and
operates the blower fan to perform a scavenging operation. When the
combustion period in the intermittent combustion is ended, the
control part extinguishes the combustion part and operates the
blower fan to perform a scavenging operation in the non-combustion
period. A total air blowing amount of the blower fan in the
scavenging operation during the non-combustion period is set to be
less than a total air blowing amount of the blower fan in the
scavenging operation when the continuous combustion is stopped.
Effects
[0009] According to the disclosure, it is possible to provide a
combustion apparatus capable of suppressing frequent switching
between a combustion period and a non-combustion period when
intermittent combustion is applied.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic configuration diagram of a hot water
supplier to which a combustion apparatus according to an embodiment
of the disclosure is applied.
[0011] FIG. 2 is a mode transition diagram of the hot water
supplier.
[0012] FIG. 3 is a functional block diagram of the temperature
control in the combustion mode of the hot water supplier by the
controller.
[0013] FIG. 4 is a conceptual diagram showing an example of the
basic control operation in the intermittent combustion.
[0014] FIG. 5 is a flowchart for explaining the scavenging
operation when the transition from the continuous combustion to the
combustion standby mode is performed.
[0015] FIG. 6 is a diagram for explaining the scavenging operation
when the transition from the continuous combustion to the
combustion standby mode is performed.
[0016] FIG. 7 is a flowchart for explaining an embodiment of the
scavenging operation in the intermittent combustion.
DESCRIPTION OF THE EMBODIMENTS
[0017] Hereinafter, embodiments of the disclosure will be described
in detail with reference to the drawings. Further, in the
following, the same or corresponding parts in the drawings will be
designated by the same reference numerals, and the descriptions
will not be repeated in principle.
[0018] [Configuration of Hot Water Supplier]
[0019] FIG. 1 is a schematic configuration diagram of a hot water
supplier to which a combustion apparatus according to an embodiment
of the disclosure is applied.
[0020] With reference to FIG. 1, a hot water supplier 100 includes
a combustion can body 25 (hereinafter also simply referred to as
the "can body") in which a heat exchanger 39, a burner 31 and the
like are housed, a gas valve 30, a blower fan 36, a venturi mixer
38, a water inlet pipe 50, a can body pipe 52, a hot water outlet
pipe 54, a bypass valve 60, and a controller 80.
[0021] The water inlet pipe 50 is connected to the can body pipe 52
and a bypass pipe 58 via the bypass valve 60. Low temperature water
such as tap water is supplied to the water inlet pipe 50. The
low-temperature water in the water inlet pipe 50 is distributed to
the can body pipe 52 and the bypass pipe 58 via the bypass valve
60.
[0022] The can body pipe 52 is connected to the heat exchanger 39.
Low-temperature water introduced from the water inlet pipe 50 into
the can body pipe 52 is heated by passing through the heat
exchanger 39 by the heat amount generated by the burner 31.
[0023] The gas valve 30 is disposed in a gas supply pipe to the
burner 31. Though not shown, the gas valve 30 includes a solenoid
valve having a function of turning on and off the supply of fuel
gas to the burner 31 and a gas proportional valve that controls the
gas flow rate of the gas supply pipe according to the opening
degree. The heat amount generated by the burner 31 can be
controlled by the gas flow rate of the gas supply pipe.
[0024] The burner 31 is configured to be capable of controlling the
heat amount generated not only by adjusting the gas flow rate but
also by switching control of the number of combustion capacity
stages (hereinafter also simply referred to as "the number of
combustion stages"). Though not shown, the burner 31 has a
plurality of combustion nozzles capable of individually supplying
fuel by a gas on-off switching valve (capacity switching valve).
The number of combustion nozzles to be operated for combustion can
be selectively changed and adjusted by controlling and switching
the on and off of each capacity switching valve by the controller
80. For example, a plurality of combustion nozzles are divided into
a plurality of groups, and fuel gas can be selectively supplied to
the plurality of groups by the on-off switching of the capacity
switching valve. As a result, the number of combustion stages can
be switched to a plurality of stages. In addition, the heat amount
generated can be varied by varying the flow rate of gas supplied to
the combustion nozzles of each stage. By continuous variable
control of the generation capacity, the heating capacity of the
combustion apparatus can be varied. The burner 31 corresponds to an
embodiment of the "combustion part."
[0025] The venturi mixer 38 mixes the fuel gas supplied from the
gas supply pipe with the combustion air. Hereinafter, the fuel gas
mixed with the combustion air is also referred to as the "mixed
gas." The mixed gas is supplied to the burner 31 by the blower fan
36 via a mixing chamber 34.
[0026] The air blowing amount of the blower fan 36 is controlled so
that the air-fuel ratio with the amount of gas supplied from the
burner 31 as a whole becomes a predetermined value (for example,
the stoichiometric air-fuel ratio). Since the air blowing amount of
the blower fan 36 is proportional to the fan rotation speed, the
rotation speed of the blower fan 36 is controlled according to the
target rotation speed set according to the change in the supply gas
amount. The blower fan 36 is provided with a rotation speed sensor
37 for detecting the fan rotation speed.
[0027] When an ignition device 32 is operated by the controller 80,
a high frequency voltage is applied to a spark plug 33 to generate
a spark in the spark plug 33. When the mixed gas is ignited by this
spark, the fuel gas is burned and a flame is generated. A flame
detection device 35 is configured by a thermocouple or the like for
detecting a flame. The controller 80 detects that the burner 31 has
been ignited by comparing the output voltage of the thermocouple
with a threshold value.
[0028] The combustion heat generated by the flame of the burner 31
is provided to the heat exchanger 39 in the can body 25. The heat
exchanger 39 heats the passing low-temperature water by heat
exchange with the combustion heat. As a result, high-temperature
water heated by the heat exchanger 39 is output to the hot water
outlet pipe 54. An exhaust duct 40 for discharging the exhaust gas
after combustion is provided on the downstream side of the can body
25 in the flow direction of the combustion gas.
[0029] The bypass pipe 58 and the hot water outlet pipe 54 are
connected at a confluence point 56. Therefore, from the hot water
supplier 100, hot water at an appropriate temperature adjusted by
mixing the high-temperature water output from the can body 25 and
the low-temperature water from the bypass pipe 58 is supplied to a
hot water tap 70 or a predetermined hot water supply destination
such as a bath pouring circuit (not shown).
[0030] The bypass valve 60 controls the ratio of the flow rate of
the can body pipe 52 to the flow rate of the bypass pipe 58 by
controlling the valve opening degree according to a control command
from the controller 80. The flow rate ratio k of the bypass valve
60 is defined by k=q2/q1 by using the ratio of the can body flow
rate q1 from the water inlet pipe 50 to the can body pipe 52 to the
bypass flow rate q2 from the water inlet pipe 50 to the bypass pipe
58. The controller 80 has acquired a correspondence relationship
between the opening degree of the bypass valve 60 and the flow rate
ratio k in advance and, in the outlet hot water temperature control
described later, sets the opening degree of the bypass valve 60 for
realizing the desired flow rate ratio k by using the correspondence
relationship.
[0031] A temperature sensor 62 is disposed in the can body pipe 52
and detects the temperature of the low-temperature water
(hereinafter also referred to as the "inlet water temperature Tw").
A temperature sensor 64 is disposed in a section on the upstream
side (the heat exchanger 39 side) of the hot water outlet pipe 54
with respect to the confluence point 56 and detects the temperature
of the high-temperature water (hereinafter also referred to as the
"can body temperature Tb"). A temperature sensor 66 is disposed in
a section on the downstream side of the hot water outlet pipe 54
with respect to the confluence point 56 and detects the outlet hot
water temperature Th after the high-temperature water and the
low-temperature water is mixed. A flow rate sensor 68 is disposed
in the can body pipe 52 and detects the can body flow rate q1.
[0032] The controller 80 can be configured by, for example, a
microcomputer. The controller 80 receives a detection value of each
sensor and a user operation and generates a control command to each
device in order to control the overall operation of the hot water
supplier 100. The user operation includes an operation on/off
command for the hot water supplier 100 and a command for the set
value of the outlet hot water temperature (outlet hot water target
temperature Tr*), which are input by operating an operation switch
provided on a remote controller (not shown).
[0033] [Operation Mode of Hot Water Supplier]
[0034] FIG. 2 is a mode transition diagram of the hot water
supplier 100.
[0035] As shown in FIG. 2, the operation mode of the hot water
supplier 100 includes an "operation off mode," an "operation on
mode," and a "combustion mode." The operation off mode corresponds
to the power off state of the hot water supplier 100. When the
operation switch (SW) is turned on in the operation off mode, the
hot water supplier 100 transitions to the operation on mode.
[0036] In the operation on mode, the fuel supply to the burner 31
is cut off, and the combustion of the burner 31 is continuously
stopped. In this state, combustion stands by until the minimum
operating flow rate (MOQ) is detected. Hereinafter, the state in
which the flow rate in the hot water supplier 100 exceeds the MOQ
is also referred to as the "MOQ on," and the state in which the
flow rate does not exceed the MOQ is also referred to as the "MOQ
off."
[0037] When the MOQ on is detected in the operation on mode, the
combustion mode is started. In the combustion mode, the gas valve
30 is opened and fuel gas is supplied to the burner 31.
Hereinafter, the operation on mode is also referred to as the
"combustion standby mode."
[0038] In the combustion mode, a required heat generation amount
Qrq for the burner 31 is set by the temperature control for
controlling the outlet hot water temperature Th to the outlet hot
water target temperature Tr*, and the operation state (the number
of combustion stages and the gas flow rate) of the burner 31 is
controlled according to the required heat generation amount Qrq. In
the temperature control of the combustion mode, one of "continuous
combustion," in which the combustion period of the burner 31 is
continuously provided, and "intermittent combustion," in which the
combustion period and the non-combustion period of the burner 31
are repeatedly provided, is applied. The temperature control in the
combustion mode will be described later.
[0039] In the combustion mode, when the MOQ off is detected, the
operation mode transitions to the operation on mode (the combustion
standby mode). As a result, the combustion of the burner 31 is
continuously stopped.
[0040] When the operation SW is turned off in the combustion
standby mode or the combustion mode, the hot water supplier 100
transitions to the operation off mode. When the operation SW is
turned off in the combustion mode, the combustion of the burner 31
is also stopped.
[0041] [Temperature Control in Combustion Mode]
[0042] FIG. 3 is a functional block diagram of the temperature
control in the combustion mode of the hot water supplier 100 by the
controller 80. The function of each block in FIG. 3 can be realized
by software processing in which the controller 80 executes a
program stored in advance. Alternatively, it is also possible to
realize a part or all of each block by hardware processing using a
dedicated electronic circuit.
[0043] With reference to FIG. 3, the controller 80 has a can body
temperature control part 810 and a flow rate ratio control part
820. The can body temperature control part 810 includes a required
heat amount calculation part 812, a burner control part 814, and a
fan control part 816.
[0044] The required heat amount calculation part 812 calculates the
required heat generation amount Qrq for the burner 31 based on the
can body flow rate q1 (the flow rate sensor 68), the inlet water
temperature Tw (the temperature sensor 62), the can body
temperature Tb (the temperature sensor 64), and the target
temperature Tb* of the can body temperature Tb.
[0045] The burner control part 814 determines the operation state
(the number of combustion stages, the gas flow rate and the like)
of the burner 31 for controlling the heat amount generated by the
burner 31 according to the required heat generation amount Qrq from
the required heat amount calculation part 812. Then, a control
command to the burner 31 and the gas valve 30 is generated
according to the determined operation state of the burner 31.
Further, the burner control part 814 determines the target fan
rotation speed Fr* of the blower fan 36 according to the determined
operation state of the burner 31.
[0046] The fan control part 816 sets the target fan rotation speed
Fr* of the blower fan 36 according to the required heat generation
amount Qrq from the burner control part 814. Then, a control
command to the blower fan 36 is generated according to the set
target fan rotation speed Fr*.
[0047] The flow rate ratio control part 820 generates a control
command to the bypass valve 60 for controlling the outlet hot water
temperature Th to the outlet hot water target temperature Tr* based
on the outlet hot water target temperature Tr* and the temperature
(Tb, Th, Tw) detected by the temperature sensors 62 to 66.
[0048] With reference back to FIG. 2, in the combustion mode, the
burner 31 generates a heat amount according to the required heat
generation amount Qrq by selectively applying the continuous
combustion and the intermittent combustion.
[0049] When the combustion standby mode is transitioned to the
combustion mode, the ignition control of the burner 31 is first
performed. In the ignition control, the burner 31 is ignited by
operating the ignition device 32 in a state where the gas valve 30
is controlled according to a predetermined ignition condition. When
the ignition of the burner 31 is detected based on the output of
the flame detection device 35, the continuous combustion or the
intermittent combustion is started depending on the magnitude of
the required heat generation amount Qrq.
[0050] In the continuous combustion, the burner 31 is operated to
burn continuously in an operation state set according to the
required heat generation amount Qrq. The maximum heat generation
amount in the continuous combustion is the heat generation amount
in a state where the number of combustion stages is maximized and
the gas flow rate is maximized. In addition, the minimum heat
generation amount Q1 in the continuous combustion corresponds to
the heat generation amount when the number of combustion stages is
minimized and the gas flow rate is set to the lower limit value at
which a stable combustion state can be ensured. That is, the
minimum heat generation amount Q1 corresponds to the lower limit
value of the heat generation amount range in the continuous
combustion.
[0051] Therefore, the burner control part 814 controls the burner
31 so that the continuous combustion is applied when the required
heat generation amount Qrq is greater than or equal to Q1, while
the intermittent combustion is applied when the required heat
generation amount Qrq is less than Q1. In this way, it is possible
to deal with even the case where the required heat generation
amount Qrq is less than Q1. Therefore, when Qrq <Q1 after the
ignition control or during the continuous combustion, the
intermittent combustion is applied, and the combustion mode is
continued.
[0052] In the intermittent combustion, the combustion of the burner
31 in the operation state that generates the minimum heat
generation amount Q1 is intermittently performed. That is, the
burner 31 is extinguished and reignited so that a combustion period
Ton for generating the minimum heat generation amount Q1 and a
non-combustion period Toff in which the combustion is temporarily
stopped are repeatedly provided.
[0053] When the required heat generation amount Qrq rises during
the intermittent combustion and Qrq>Q1* is established, the
transition from the intermittent combustion to the continuous
combustion is performed. The determination value Q1* at this time
is preferably set greater than Q1 in order to avoid hunting.
[0054] On the other hand, during the intermittent combustion, when
the required heat generation amount Qrq further decreases and
becomes less than a predetermined lower limit value Q2, the
combustion mode is ended and the transition to the combustion
standby mode is performed.
[0055] Further, in each of the continuous combustion and the
intermittent combustion, the transition to the combustion standby
mode is performed also when the MOQ off is detected. After the
transition to the combustion standby mode, the combustion of the
burner 31 is stopped until the combustion mode is started
again.
[0056] FIG. 4 is a conceptual diagram showing an example of the
basic control operation in the intermittent combustion.
[0057] With reference to FIG. 4, during the intermittent
combustion, the combustion period (corresponding to Ton in the
figure) and the non-combustion period (corresponding to Toff in the
figure) are switched according to the comparison between the can
body temperature Tb (the temperature sensor 64) and the target
temperature range of the can body temperature Tb. The upper limit
value TH of the target temperature range of the can body
temperature Tb is set to a temperature .alpha. .degree. C. higher
than the target temperature Tb* in the temperature control
(TH=Tb*+.alpha.). The lower limit value TL of the target
temperature range is set to a temperature .beta..degree. C. lower
than the target temperature Tb* (TL=Tb*-.beta.). .alpha. and .beta.
are constants. Further, .alpha. and .beta. may have the same value
or different values.
[0058] In the operation example of FIG. 4, at the time t1 during
the combustion period, in response to the case where Tb>TH, the
burner 31 is extinguished, and the non-combustion period is
started. When the non-combustion period is started, the combustion
of the burner 31 is stopped, so that the can body temperature Tb
gradually decreases. At the time t3 during this non-combustion
period, when Tb<TL, the combustion period is started, and the
burner 31 is reignited. After that, the non-combustion period is
started at the time t5 and the time t7 when Tb>TH, while the
combustion period is started at the time t6 and the time t8 when
Tb<TL.
[0059] In this way, the combustion period and the non-combustion
period of the burner 31 are repeatedly provided in accordance with
the transition of the can body temperature Tb.
[0060] As shown in FIG. 4, during the application of the
intermittent combustion, at the start of the combustion period, an
ignition operation for reigniting the burner 31 is performed. When
the ignition operation is started, the burner control part 814
(FIG. 3) operates the ignition device 32. The ignition device 32
applies a high frequency voltage to the spark plug 33. When the
high frequency voltage is applied, a spark is generated in the
spark plug 33, and this spark ignites the mixed gas from the burner
31 to ignite the burner 31. When the burner control part 814
detects that the burner 31 has been ignited based on the comparison
between the output voltage from the flame detection device 35 and
the threshold value, the burner control part 814 stops the ignition
device 32 and transitions from the ignition operation to the
combustion operation.
[0061] Further, if the ignition is not detected within a
predetermined set time, the burner control part 814 stops the
ignition device 32 and then re-operates the ignition device 32. The
burner control part 814 repeatedly operates the ignition device 32
until the ignition is detected. In the case where the ignition is
not detected and it cannot be transitioned to the combustion
operation even after the operation is repeated for a predetermined
number of times, the burner control part 814 ends the ignition
operation. In this case, the hot water supplier 100 transitions
from the combustion mode to the combustion standby mode.
[0062] At the start of the non-combustion period, after
extinguishing the burner 31, a scavenging operation is performed
for discharging (scavenging) the combustion exhaust gas and the
unburned mixed gas lingering in the vicinity of the burner 31
through the exhaust duct 40. When the scavenging operation is
started, the fan control part 816 (FIG. 3) operates the blower fan
36. Effective scavenging can be performed by increasing the
rotation speed of the blower fan 36 during the scavenging operation
to be greater than the fan rotation speed during the ignition
operation and the combustion operation.
[0063] Further, the scavenging operation is performed even after
the combustion of the burner 31 is stopped when the hot water
supplier 100 transitions from the combustion mode to the combustion
standby mode. That is, the scavenging operation is performed when
the MOQ off is detected in the continuous combustion and the
transition to the combustion standby mode is performed.
[0064] FIG. 5 is a flowchart for explaining the scavenging
operation when the transition from the continuous combustion to the
combustion standby mode is performed. The control process according
to the flowchart shown in FIG. 5 can be performed by the controller
80 during the application of the continuous combustion.
[0065] With reference to FIG. 5, the controller 80 determines in
step S01 whether the continuous combustion is in progress. When the
continuous combustion is in progress (when YES is determined in
S01), the controller 80 determines in step S02 whether the MOQ off
is detected. When the continuous combustion is not in progress
(when NO is determined in S01), the controller 80 does not perform
the process after S02.
[0066] When the MOQ off is detected during the continuous
combustion (when YES is determined in S02), the controller 80
proceeds the process to S03, extinguishes the burner 31, and stops
the combustion of the burner 31. Subsequently, the controller 80
proceeds the process to steps S04 to S08 to perform the scavenging
operation in accordance with the predetermined scavenging
condition. The scavenging condition includes a condition that
defines the rotation speed of the blower fan 36 and the operation
time of the blower fan 36.
[0067] FIG. 6 is a diagram for explaining the scavenging operation
when the transition from the continuous combustion to the
combustion standby mode is performed. FIG. 6 shows an example of
the fan rotation speed Fc and the operation time Ts of the blower
fan 36 during the scavenging operation.
[0068] With reference to FIG. 6, the scavenging operation includes
a first scavenging operation and a second scavenging operation. In
the first scavenging operation, the blower fan 36 is operated at a
fan rotation speed Fc1 for a time Ts1. The fan rotation speed Fc1
is, for example, 6000 rpm, and the operation time Ts1 is, for
example, 5 seconds. In the second scavenging operation, the blower
fan 36 is operated at a fan rotation speed Fc2 for a time Ts2. The
fan rotation speed Fc2 is, for example, 3000 rpm, and the operation
time Ts2 is, for example, 30 seconds. In the example of FIG. 6, it
is set that Fc1>Fc2 and Ts1<Ts2, but the magnitude
relationship between Fc1 and Fc2 and the magnitude relationship
between Ts1 and Ts2 are not limited to thereto.
[0069] The first scavenging operation is mainly performed for
discharging the combustion exhaust gas and the unburned mixed gas
lingering in the vicinity of the burner 31. In particular, this is
because if the unburned mixed gas lingers, when the burner 31 is
reignited, a flame propagates through this mixed gas, which may
cause a phenomenon of explosive ignition with loud noise, the
so-called explosive welding. The fan rotation speed Fc1 of the
first scavenging operation is preferably set to be greater than the
fan rotation speed during the continuous combustion in order to
efficiently discharge the combustion exhaust gas and the unburned
mixed gas.
[0070] The second scavenging operation is mainly performed for
removing the residual heat of the heat exchanger 39 and the like
after the combustion is stopped, and for discharging air with moist
present in the can body 25. That is, the second scavenging
operation corresponds to the post-purge. By performing the
post-purge, it is possible to suppress post-boiling due to the
residual heat of the heat exchanger 39 after the combustion is
stopped, and to prevent temporary high-temperature water from being
provided when hot water is re-delivered.
[0071] As described above, since the second scavenging operation
does not aim at discharging the lingering gas as in the first
scavenging operation, the fan rotation speed Fc2 may be set to be
less than or equal to the fan rotation speed Fc1 of the first
scavenging operation. Further, unlike the first scavenging
operation, the second scavenging operation mainly aims at cooling
the heat exchanger 39 and the like. Therefore, the operation time
Ts2 may be set longer than the operation time Ts1 of the first
scavenging operation in consideration of the heat capacity of the
heat exchanger 39 and the like.
[0072] With reference back to FIG. 5, when the scavenging operation
is started, the controller 80 first performs the first scavenging
operation in step S04. In step S04, the controller 80 sets the
target fan rotation speed Fr* of the blower fan 36 to Fc1, and
controls the blower fan 36 so that the fan rotation speed Fc
detected by the rotation speed sensor 37 matches the target fan
rotation speed Fr*. Further, when the first scavenging operation is
started, the controller 80 activates a timer to start measuring the
operation time of the first scavenging operation. Assuming the
timer value Ts=0 at the start of the first scavenging operation,
the timer value Ts is automatically increased according to the
operation time.
[0073] During the first scavenging operation, the controller 80
compares the timer value Ts with the preset operation time Ts1 in
step S05. When Ts<Ts1 (when NO is determined in S05), the
controller 80 returns to S04 and continues the first scavenging
operation. As a result, the first scavenging operation is
continuously performed until the timer value Ts reaches Ts1.
[0074] When the timer value Ts reaches the operation time Ts1 (when
YES is determined in S05), the controller 80 ends the first
scavenging operation and clears the timer value Ts. Further, the
controller 80 proceeds the process to step S06 and performs the
second scavenging operation. In step S06, the controller 80 sets
the target fan rotation speed Fr* of the blower fan 36 to Fc2, and
controls the blower fan 36 so that the fan rotation speed Fc
detected by the rotation speed sensor 37 matches the target fan
rotation speed Fr*. Further, when the second scavenging operation
is started, the controller 80 re-activates the timer and starts
measuring the operation time of the second scavenging operation.
Assuming the timer value Ts=0 at the start of the second scavenging
operation, the timer value Ts is automatically increased according
to the operation time.
[0075] During the second scavenging operation, the controller 80
compares the timer value Ts with the preset operation time Ts2 in
step S07. When Ts<Ts2 (when NO is determined in S07), the
controller 80 returns to S06 and continues the second scavenging
operation. As a result, the second scavenging operation is
continuously performed until the timer value Ts reaches Ts2.
[0076] When the timer value Ts reaches the operation time Ts2 (when
YES is determined in S07), the controller 80 ends the scavenging
operation in step S08 and clears the timer value Ts. Further, the
controller 80 proceeds the process to step S09 and ends the
continuous combustion. As a result, the transition to the
combustion standby mode is performed, and the combustion of the
burner 31 is continuously stopped.
[0077] As described above, by performing the scavenging operation
after the burner 31 is extinguished, it is possible to prevent the
occurrence of explosive welding when the burner 31 is reignited and
to suppress the post-boiling in the heat exchanger 39 after the
combustion is stopped.
[0078] However, if it is configured that the above-described
scavenging operation is performed every time the combustion period
is ended during the application of the intermittent combustion,
though it is possible to prevent the occurrence of explosive
welding when the next combustion period starts, during the
non-combustion period, there is a concern that the heat exchanger
39 after the combustion is stopped is unnecessarily cooled. Since
the low-temperature water keeps passing through the heat exchanger
39 even during the non-combustion period, the occurrence of
post-boiling in the heat exchanger 39 is suppressed.
[0079] According to this, in the operation example shown in FIG. 4,
the decrease of the can body temperature Tb during the
non-combustion period is accelerated, and as a result, the elapsed
time from the start of the non-combustion period to the time when
Tb<TL (time Toff in FIG. 4) is shortened. Then, as the
non-combustion period is shortened, the cycle length (Ton+Toff)
corresponding to the sum of each combustion period and
non-combustion period is also shortened.
[0080] When the cycle length in the intermittent combustion is
shortened, since the combustion period and the non-combustion
period are frequently switched, the number of ignitions of the
burner 31 increases. As a result, thermal stress is frequently
applied to equipment such as the heat exchanger 39 as the burner 31
is repeatedly ignited and extinguished, which may increase fatigue
failure of the equipment and cause a problem in the equipment
durability. In addition, there is a concern that the consumption of
fuel gas may increase due to unnecessary combustion of the burner
31. Therefore, it is necessary to suppress the cooling of the heat
exchanger 39 during the non-combustion period and suppress the
shortening of the non-combustion period.
[0081] Therefore, in the combustion apparatus according to the
embodiment, the scavenging operation performed during the
non-combustion period of the intermittent combustion is configured
to reduce the total air blowing amount, which is the total value of
the air blowing amount of the blower fan 36, compared with the
scavenging operation performed when the continuous combustion is
stopped.
[0082] Specifically, the total air blowing amount of the blower fan
36 can be estimated by multiplying the air blowing amount per unit
time of the blower fan 36 and the operation time of the blower fan
36. Further, since the air blowing amount per unit time of the
blower fan 36 is proportional to the fan rotation speed, in the
following description, the total air blowing amount shall be
calculated by the product of the fan rotation speed and the
operation time of the blower fan 36 (the fan rotation
speed.times.the operation time).
[0083] In the operation example of FIG. 6, the total air blowing
amount in the first scavenging operation is indicated by the
product (Fc1.times.Ts1) of the fan rotation speed Fc1 and the
operation time Ts1. The total air blowing amount in the second
scavenging operation is indicated by the product of the fan
rotation speed Fc2 and the operation time Ts2 (Fc2.times.Ts2).
Further, the total air blowing amount of the scavenging operation
performed when the normal combustion is stopped can be indicated by
the total value (Fc1.times.Ts1+Fc2.times.Ts2) of the total air
blowing amount of the first scavenging operation (Fc1.times.Ts1)
and the total air blowing amount of the second scavenging operation
(Fc2.times.Ts2).
[0084] On the other hand, the total air blowing amount in the
scavenging operation during the non-combustion period is set to a
value less than the above-described total value
(Fc1.times.Ts1+Fc2.times.Ts2). The hatched region in FIG. 6
illustrates the scavenging operation during the non-combustion
period. In the example of FIG. 6, the blower fan 36 is operated at
the fan rotation speed Fc2 for a time Ts1 #during the
non-combustion period. This time Ts1 #is longer than Ts1 and
shorter than Ts2 (Ts1<Ts1 #<Ts2). The area of the hatched
region in FIG. 6 corresponds to the total air blowing amount in the
scavenging operation during the non-combustion period.
[0085] As described above, during the non-combustion period, the
cooling of the heat exchanger 39 can be suppressed by reducing the
total air blowing amount of the blower fan 36 as compared with the
case after the continuous combustion is stopped. Therefore, the
rate of decrease of the can body temperature Tb during the
non-combustion period can be slow, and the shortening of the
non-combustion period can be suppressed. As a result, since it is
possible to prevent frequent switching between the combustion
period and the non-combustion period, the equipment durability can
be improved, and wasteful consumption of fuel gas can be
suppressed.
[0086] Further, during the application of the intermittent
combustion, since the fluctuation cycle of the can body temperature
Tb becomes longer as the cycle length (Ton+Toff) corresponding to
the sum of each combustion period and non-combustion period becomes
longer, the stability of the outlet hot water temperature Th can be
improved.
[0087] However, even in the scavenging operation during the
non-combustion period, it is necessary to ensure the prevention of
explosive welding when the burner 31 is reignited. Therefore, the
total air blowing amount in the scavenging operation during the
non-combustion period is at least greater than or equal to the
total air blowing amount in the first scavenging operation
(Fc1.times.Ts1).
[0088] For such an embodiment, it is possible to exemplify a
configuration in which only the first scavenging operation shown in
FIG. 6 is performed and the second scavenging operation is not
performed during the non-combustion period. According to this, when
the combustion period is ended during the application of the
intermittent combustion and the burner 31 is extinguished for the
start of the non-combustion period, the controller 80 operates the
blower fan 36 at the fan rotation speed Fc1 for the time Ts1, and
then stops the blower fan 36.
[0089] FIG. 7 is a flowchart for explaining an embodiment of the
scavenging operation in the intermittent combustion. The control
process according to the flowchart shown in FIG. 7 can be performed
by the controller 80 during the application of the intermittent
combustion.
[0090] Further, in the flowchart shown in FIG. 7, the process of
steps S02 to S08 shows the control process when transitioning from
the intermittent combustion to the combustion standby mode, and is
the same as the control process when transitioning from the
continuous combustion to the combustion standby mode shown in FIG.
5. Therefore, the description of the process of S02 to S08 will be
omitted.
[0091] With reference to FIG. 7, the controller 80 determines in
step S01A whether the intermittent combustion is in progress. When
the intermittent combustion is not in progress (when NO is
determined in S01A), the controller 80 does not perform the process
after S02.
[0092] On the other hand, when the intermittent combustion is in
progress (when YES is determined in S01A), the controller 80
determines in step S02 whether the MOQ off is detected. When the
MOQ off is detected during the intermittent combustion (when YES is
determined in S02), the controller 80 proceeds the process to S03,
extinguishes the burner 31, and stops the combustion of the burner
31. Subsequently, the controller 80 performs the scavenging
operation according to steps S04 to S08. When the scavenging
operation is ended (step S08), the controller 80 proceeds the
process to step S09A and ends the intermittent combustion. As a
result, the transition to the combustion standby mode is performed,
and the combustion of the burner 31 is continuously stopped.
[0093] On the other hand, if the MOQ off is not detected during the
intermittent combustion (when NO is determined in S02), the
controller 80 proceeds the process to step S10 and switches the
combustion period and the non-combustion period according to the
comparison between the can body temperature Tb (the temperature
sensor 64) and the target temperature range of the can body
temperature Tb.
[0094] During the intermittent combustion, the controller 80
determines in step S10 whether the combustion period is in
progress. When the combustion period is not in progress (when NO is
determined in S10), the controller 80 does not perform the process
after S11. On the other hand, when the combustion period is in
progress (when YES is determined in S10), the controller 80
proceeds the process to step S11 and compares the can body
temperature Tb and the upper limit value TH of the target
temperature range. When Tb.ltoreq.TH (when NO is determined in
S10), the controller 80 does not perform the process after S11.
[0095] On the other hand, when Tb>TH (when YES is determined in
S11), the controller 80 extinguishes the burner 31 in order to
start the non-combustion period in step S12. During the
non-combustion period, the controller 80 proceeds the process to
steps S13 to S15 to perform the scavenging operation according to
the predetermined scavenging condition.
[0096] Specifically, the controller 80 performs the first
scavenging operation in step S13. In step S13, the controller 80
sets the target fan rotation speed Fr* of the blower fan 36 to Fc1,
and controls the blower fan 36 so that the fan rotation speed Fc
detected by the rotation speed sensor 37 matches the target fan
rotation speed Fr*. Further, when the first scavenging operation is
started, the controller 80 activates a timer to start measuring the
operation time of the first scavenging operation. Assuming the
timer value Ts=0 at the start of the first scavenging operation,
the timer value Ts is automatically increased according to the
operation time.
[0097] During the first scavenging operation, the controller 80
compares the timer value Ts with the preset operation time Ts1 in
step S14. When Ts<Ts1 (when NO is determined in S14), the
controller 80 returns to S13 and continues the first scavenging
operation. As a result, the first scavenging operation is
continuously performed until the timer value Ts reaches Ts1. When
the timer value Ts reaches the operation time Ts1 (when YES is
determined in S14), the controller 80 ends the scavenging operation
in S15 and clears the timer value Ts.
[0098] During the non-combustion period, the controller 80 compares
the can body temperature Tb with the lower limit value TL of the
target temperature range in step S16. When Tb.gtoreq.TL (when NO is
determined in S16), the controller 80 does not perform the process
in S17, and the non-combustion period is continued. On the other
hand, when Tb<TL (when YES is determined in S16), the controller
80 proceeds the process to step S17 and reignites the burner 31 in
order to start the combustion period. According to the above
procedure, the combustion period and the non-combustion period of
the burner 31 are repeatedly provided in accordance with the
transition of the can body temperature Tb, and the first scavenging
operation is performed during the non-combustion period. When the
MOQ off is detected during the intermittent combustion (when YES is
determined in S02), the controller 80 proceeds the process to steps
S03 to S09A, extinguishes the burner 31, and performs the first and
second scavenging operations.
[0099] For another embodiment of the scavenging operation in the
intermittent combustion, as illustrated in FIG. 6, it is possible
to exemplify a configuration in which, on condition that the total
air blowing amount of the blower fan 36 is greater than or equal to
the total air blowing amount in the first scavenging operation
(Fc1.times.Ts1) and less than the total value
(Fc1.times.Ts1+Fc2.times.Ts2) of the total air blowing amount of
the first scavenging operation (Fc1.times.Ts1) and the total air
blowing amount of the second scavenging operation (Fc2.times.Ts2),
the fan rotation speed Fc of the blower fan 36 is set to a rotation
speed less than Fc1 and the time Ts1 #is set to a time longer than
Ts1. In addition, the embodiment of the scavenging operation is not
limited to these embodiments, and may be set as desired according
to the heat capacity of the heat exchanger 39 and the like under
the above conditions.
[0100] As described above, according to the combustion apparatus
according to the embodiments, the total air blowing amount of the
blower fan in the scavenging operation during the non-combustion
period is set to be less than the total air blowing amount of the
blower fan in the scavenging operation when the normal combustion
is stopped, whereby during the non-combustion period, the cooling
of the heat exchanger can be suppressed as compared with the case
after the continuous combustion is stopped. According to this, the
rate of decrease of the can body temperature during the
non-combustion period can be slow, and the shortening of the
non-combustion period can be suppressed, so frequent switching
between the combustion period and the non-combustion period can be
prevented. As a result, the equipment durability can be improved,
and wasteful consumption of fuel gas can be suppressed.
[0101] Further, during the application of the intermittent
combustion, since the fluctuation cycle of the can body temperature
Tb becomes longer as the cycle length corresponding to the sum of
each combustion period and non-combustion period becomes longer,
the stability of the outlet hot water temperature Th can be
improved.
[0102] Further, in the above-described embodiments, the control
operation in the combustion apparatus to which the continuous
combustion and the intermittent combustion are selectively applied
in the combustion mode has been described, but the control
operation in the intermittent combustion according to the
embodiment can also be applied to a combustion apparatus to which
only intermittent combustion is applied in the combustion mode. In
this case, the total air blowing amount of the blower fan in the
scavenging operation during the non-combustion period is set to be
less than the total air blowing amount of the blower fan in the
scavenging operation when the intermittent combustion is stopped,
whereby the same effect as that of the above-described embodiments
can be obtained. For example, according to the control process
according to the flowchart shown in FIG. 7, it may be configured
that when the intermittent combustion is stopped, the first
scavenging operation and the second scavenging operation are
performed, while during the non-combustion period, only the first
scavenging operation is performed, and the second scavenging
operation is not performed.
[0103] Further, in the above-described embodiments, an example in
which the combustion part is configured by the burner 31 using gas
as fuel is shown, but the energy source for heating can be any
energy source. Further, in the above-described embodiments, an
example in which the combustion apparatus is applied to the bypass
mixing type hot water supplier controlled by the bypass valve 60 is
described, but the combustion apparatus according to the
embodiments may be applied to a hot water supplier having a
configuration other than the bypass mixing type.
[0104] It should be considered that the embodiments disclosed
herein are exemplary in all aspects and are not restrictive. The
scope of the disclosure is shown by the scope of claims rather than
the above description, and it is intended to include all
modifications within the meaning and scope equivalent to the scope
of claims.
* * * * *