JP2003185109A - Combustion equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide combustion equipment capable of maintaining an optimum combustion condition while performing self-diagnosis of a combustion condition. <P>SOLUTION: This device has a combustion condition detecting means 7 provided adjacent to main flame or/and sub flame burning in a thin combustion burner 20 and a control device 6 for controlling the rotational speed of an air supply fan 4 according to an output value detected by the combustion condition detecting means. When combustion continues at less than prescribed combustion amount for more than a prescribed time after the combustion of a thick and thin combustion burner is started, the rotational speed of the air supply fan is raised step by step against the output of a fuel supply proportional valve 33, a change in the output detected by the combustion condition detecting means is detected, and an output value around a value in which the output value rapidly starts dropping is stored as a lower limit to correct the rotational speed of the air supply fan so as to be lower than the lower limit of rotational speed by a fixed rotational speed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion device such as a water heater, and more particularly to a technique for controlling the rotation speed of an air supply fan provided in the combustion device.

[0002]

2. Description of the Related Art Conventionally, as a combustion device used in a water heater or the like, a light burner burner section for lean-burning a light gas with a large primary air ratio as a main flame and a rich gas with a small primary air ratio for a secondary flame are used. A large number (a plurality) of rich-lean burners combined with a rich-burn burner for Bunsen / Semi-Bunsen combustion as sleeve fire are arranged, and this rich-burn burner is burned as required by controlling the fuel supply proportional valve and the air supply fan. BACKGROUND ART A combustion device is known in which proportional combustion is performed according to the amount.

[0003]

However, in the conventional combustion apparatus, the state of flame is different between when the engine is cold immediately after ignition and when it is warmed up after sufficient combustion, and also depending on the type of gas. Variations in the combustion state and variations in the combustion state due to equipment performance, aging, ambient temperature, etc. can be eliminated by simply controlling the conventional fuel supply proportional valve and air supply fan. Then, it was difficult to stabilize the combustion state to the optimum. Furthermore, the surface temperature of the flame mouth of the rich-lean combustion burner tends to rise with the lapse of time from the start of combustion, and the flame state also approaches the flame mouth, especially in flames with a small combustion capacity. Since it adheres to the surface, there is a possibility that a flashback occurs, the combustion state deteriorates, and the durability is significantly impaired.

Further, conventionally, there has been proposed a combustion device in which a flame rod detects a current value of a flame and the rotation speed of an air supply fan is controlled in accordance with the current value (actually developed). 63-184340),
This is to increase or decrease the number of rotations of the air supply fan for a strong or weak external back wind so as to perform balanced combustion, and there is no function to maintain an optimum combustion state.

The present invention has been made to solve the above problems, and detects the current value (also the resistance value) of a flame by a flame rod, which is an example of a combustion state detecting means, and supplies it to an air supply fan. It is an object of the present invention to provide a combustion device capable of maintaining an optimal combustion state while controlling the rotation speed of the engine while self-diagnosing the combustion state.

[0006]

In order to solve the above-mentioned problems, a combustion apparatus according to the present invention (claim 1) comprises a lean burner section for burning a lean gas having a large primary air ratio as a main flame. The fuel supply proportional valve is equipped with a rich-lean burner in combination with a rich-burn burner that burns rich gas with a small primary air ratio as sleeve flame of an auxiliary flame, and proportionally burns this rich-burn burner according to the required combustion amount. And a combustion device provided with an air supply fan, comprising a control device for controlling the number of revolutions of the air supply fan in accordance with the required primary air amount, and the control device is for a fixed time after the combustion of the rich-lean combustion burner is started. Each time the above has elapsed, the rotational speed of the air supply fan with respect to the combustion amount is controlled to be increased stepwise.

As a result, when a certain time or more has elapsed from the start of combustion, the amount of primary air supplied to the rich / lean combustion burner is increased due to the increase in the number of revolutions of the air supply fan, and the burner flame nozzle tends to increase with the passage of time. The surface temperature of is improved to a stable tendency, and the combustion state is stabilized. In this case, the fixed time and the amount of increase in the number of revolutions are determined in advance by an optimum value by a test and stored as a constant to be controlled.

The combustion device of the present invention (claim 2) is
Equipped with a rich-lean burner that combines a light-burner burner that burns a light gas with a high secondary air ratio as the main flame and a rich burner burner that burns a rich gas with a low primary air ratio as sleeve heat of a secondary flame. In a combustion device provided with a fuel supply proportional valve and an air supply fan for proportionally burning the rich-lean burner according to the required combustion amount, in the vicinity of the main flame and / or the sub-flame burning in the lean burner section. The combustion state detection means provided, and a control device for controlling the rotation speed of the air supply fan according to the output value detected by the combustion state detection means, the control device, after the start of combustion of the rich-lean combustion burner When the combustion amount is equal to or less than a certain amount and continues for a certain amount of time or more, the rotation speed of the air supply fan with respect to the combustion amount is increased stepwise to detect a change in output detected by the combustion state detecting means. However, the output value in the vicinity of which this output value starts to suddenly drop is stored as a lower limit value, and the rotation speed of the air supply fan is corrected to a state in which the rotation speed is lower than the rotation speed at the lower limit value by a constant rotation speed. It is configured to control.

As a result, when the combustion amount is maintained below a certain combustion amount and continues for a certain time or more, the output value detected by the combustion state detecting means is corrected to the rotation speed of the air supply fan corresponding to a value higher than the lower limit value. It The combustion state at the lower limit is an unstable state in which the state changes abruptly as indicated by the detected output value. Specifically, a flame blowout (hereinafter referred to as "lift") due to excessive primary air amount And is corrected to a stable state immediately before the lifted state. As a result, the paragraph (000
It is possible to eliminate the instability due to the variation of 3) and maintain the optimum combustion state while self-diagnosing the combustion state.

In the above combustion device (claim 2), the control device has a combustion amount of less than or equal to a constant amount of combustion after the start of combustion of the rich / lean combustion burner and continues for a certain amount of time or more, and an output value of the combustion state detecting means is the lower limit value. When the upper limit value that is higher than the constant value is detected, the output value suddenly increases while detecting the change in the output detected by the combustion state detection unit by gradually increasing the rotation speed of the air supply fan with respect to the combustion amount. The output value in the vicinity of the lower limit value is stored as the lower limit value, and the rotation speed of the air supply fan is controlled to be corrected to a state in which the rotation speed is lower than the rotation speed at the lower limit value,
When the output value of the combustion state detecting means is detected to be equal to or lower than the lower limit value, there is a mode in which the rotation speed of the air supply fan is controlled to return to the initial value (claim 3).

Further, in the combustion device (claims 2 and 3), the control device detects and stores the output value of the combustion state detecting means when the rich-lean combustion burner is not burning, and stores the initial value (when first used). There is a mode (claim 4) in which the rotation speed of the air supply fan is corrected using the result as a judgment reference value by adding the difference to the upper limit value and the lower limit value.

In the combustion apparatus (claims 2, 3 and 4), there is a mode (claim 5) in which the control by the control device is executed in a low combustion load region where the fuel supply proportional valve output is small. .

Further, in the combustion device (claims 2, 3, and 4), the control by the control device is based on the current value detected in the low combustion load region where the fuel supply proportional valve output is small, as a reference value, and the entire combustion load region. There is a mode (claim 6) which is adapted to be executed in.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of a water heater provided with a combustion device of the present invention, and FIG. 2 is a partial cross-sectional view of a rich / lean combustion burner provided in the combustion device.

In the figure, reference numeral 1 is a combustion apparatus, which includes a burner unit 2, a fuel supply system 3, and an air supply fan 4.

The burner unit 2 comprises a large number of rich-lean burn burners 20 arranged side by side.
As shown in FIG. 2, the light combustion burner portion 22 that discharges the light gas having a low fuel gas concentration and a large primary air ratio from the main flame port 21 at the upper end and burns it lean as a main flame, and the fuel gas concentration The concentrated gas with a high primary air ratio and small primary air ratio
Is combined with the rich combustion burner portions 24, 24 which are discharged from the auxiliary flame ports 23, 23 adjacent to each other on both sides to cause Bunsen / Semi-Bunsen combustion as sleeve fire of the auxiliary flame. The hot water supply system 5 is provided above the burner unit 2.
The heat exchanger 50 is provided and the water from the water supply pipe 51 is heated by the heat exchanger 50 and taken out from the hot water outlet pipe 52.

The fuel supply system 3 is for supplying fuel gas to each of the rich / lean combustion burners 20 of the burner unit 2 and has a nozzle holder 31 connected to a gas supply pipe 30.
, A fuel nozzle 32 is attached so as to face the gas injection port of each rich-lean combustion burner 20, and the gas supply pipe 3
A fuel supply proportional valve 33 that adjusts the fuel gas supply amount according to the hot water discharge temperature and the hot water discharge amount is provided in the middle of 0.
In the figure, 34 is a main valve, and 35, 35 are capacity switching valves.

The air supply fan 4 is for supplying air. Primary air sucked and supplied from the gas inlet of each rich-burn combustion burner 20 together with fuel gas, and a large number of rich-burn burners are provided. The secondary air is supplied to the flame from between 20 and 20. By the air supply fan 4 and the fuel supply proportional valve 33, the rich / lean combustion burner 20 is burned in proportion to the required combustion amount.
In this case, the detection signals from the water amount sensor 53 provided in the water supply pipe 51 and the hot water temperature thermistor 54 provided in the hot water supply pipe 52 are input to the control device 6, and upon receipt of the detection signals, the control device 6 causes the fuel supply proportional valve to operate. Fuel gas supply amount by 33,
The number of revolutions (air flow rate) of the air supply fan 4 is controlled so as to have a constant air-fuel ratio.

The main flame port 21 of the rich / lean combustion burner 20 is also provided.
A frame rod 7 is installed above the frame, and the frame rod 7 detects the flame currents of the main flame, the lean flame, and the auxiliary flame, the rich flame, and the detected current value is input to the control device 6. As a result, the combustion state is detected, and as a result, it functions as a safety device to maintain combustion. Further, a timer 60 is installed in the control device 6, and the timer 60 can control the rotation speed of the air supply fan 4 over time.

Next, the air supply fan 4 by the controller 6
The rotation speed control of will be described. First, the control by the timer 60 will be described with reference to FIG. In the control by the timer 60, the control device 6 gradually increases the rotation speed of the air supply fan 4 with respect to the output of the fuel supply proportional valve 33 when the combustion of a certain time or more has elapsed after the ignition of the rich / lean combustion burner 20. To control. For example, for 1 minute after the start of combustion, combustion control is performed according to the stored initial characteristics, that is, the relationship between the air supply fan rotation speed and the combustion amount as shown by the line in FIG. 3A, and when a fixed time (1 minute) elapses. As shown by the line in FIG. 3B, the rotation number of the air supply fan 4 is 50
When the rpm is increased and then a fixed time (3 minutes) elapses, the speed is further increased by 50 rpm as shown by the line C in FIG. 3 and then, when the fixed time (30 minutes) elapses, the speed is further increased by 50 rpm.

In this case, originally, the rich / lean combustion burner 20 is
The combustion state immediately after ignition in the cold state tends to lift, especially in the low combustion load range, and becomes stable as the burner body warms over time, but depending on the type of gas (back test gas: 13A-2 , Flammability test gas 13A-3), a flame may approach the flame mouth surface and stick to the flame surface over time, so-called solid fire. Therefore,
By performing the control as described above in the low combustion load region where combustion is unstable, the combustion state is improved over time, the temperature rise of the main flame port 21 portion due to the solid fire is reduced, and the rich-lean combustion burner 20 is While improving durability, flammability,
The reliability can be improved.

Next, the control by the frame rod 7 will be described with reference to FIG.
Will be described. The flame rod 7 detects the current value of the flame, and detects the state of the flame during steady combustion, that is, the combustion state. As shown in FIG. 4 showing the relationship between the current value of the flame generated by the frame rod 7 and the rotation speed of the air supply fan 4, the rotation speed (1
Above 900 rpm), as the amount of air supply increases (the number of revolutions increases), the flame becomes in a lifted state, the flame becomes leaner, and the resistance value of the flame increases, so it is detected by the frame rod 7. The applied current value drops sharply. Therefore, the lower limit current value is obtained near the point where the current value suddenly decreases, and by burning in a place where the current value is slightly higher than this lower limit current value, the amount of air is always excessive and the flame is unstable in a lifted state. It is possible to maintain the optimum combustion state immediately before (preliminary) the state.

Therefore, when the combustion state has passed for a certain period of time after ignition of the rich / lean combustion burner 20, the fuel supply proportional valve 3
While gradually increasing the number of revolutions of the air supply fan 4 with respect to the output of 3 and monitoring the change in the current value, the current value near the point where the current value suddenly drops is obtained as the lower limit current value,
The rotational speed of the air supply fan 4 is controlled to be corrected to a state in which the rotational speed is lower than the rotational speed at the lower limit current value by a constant value. For example, as shown in FIG. 4, after the start of combustion, the rotation speed of the air supply fan 4 is increased by 50 rpm from 1800 rpm every fixed time (2 minutes), and the increase upper limit of the rotation speed is set to 200 rpm. In this way, when the rotation speed of the air supply fan 4 rises to around 1900 rpm, the flame is lifted and the current value detected by the frame rod 7 drops sharply from 10 μA (indicated by Z in FIG. 4). Since there is the above), the current value in this Z portion is set as the lower limit current value. Then, the air supply amount at this lower limit current value is
It cannot be said that the combustion is stable because the flame is in the boundary state where it is in a lifted state. Therefore, the rotation speed of the air supply fan 4 is reduced to 50 rpm below the rotation speed at the lower limit current value. Is controlled so as to correct. As a result, it is possible to avoid the lift state of the flame and the solid fire state while maintaining the optimum combustion state regardless of the type of gas while self-diagnosing the combustion state.

Next, the control by the frame rod 7 will be described with reference to the flow chart shown in FIG. First, in the combustion of the rich / lean combustion burner 20, if it is determined that there is a combustion instruction (step S2) after the operation switch is turned on (step S1), the air supply fan is turned on (step S3).
become. Next, turn on the air supply fan (step S
If 4) is determined, it is determined that there is no pseudo flame (step S5) based on the current value of the frame rod 7, and the ignition sequence is ON (step S6). If the air supply fan is OFF in step 4 (NO), the alarm is activated (step S7) after a certain time (30 seconds) has elapsed,
If there is a pseudo flame in step 5 (NO), a fixed time (1
After the elapse of 0 seconds, the alarm is activated (step S8). Next, the flame detection associated with the ignition sequence being turned on (step S6) is judged by the current value of the frame rod 7 (step S9), and when the flame is detected (YES), the ignition sequence is turned off (step S10). Then, the proportional combustion control is started (step S11). In addition, step 9
If the flame is not detected in (NO), the ignition sequence is turned off (step S12), and it is judged whether or not the re-ignition operation is the first time (step S13). If the first time (Y)
In (ES), the ignition sequence is turned ON again (step S6), and if it is the first time or more (NO), the alarm is activated (step S14), and the air supply fan performs forced air purge for several seconds (5 seconds) (step S15). )I do.

When the proportional combustion control is started (step S11), the current value is detected by the flame rod 7 (step S16) for a fixed time (30 seconds), and the detected current value I is taken as the sampling current value Im. After that (step S17), it is determined whether the rotation speed of the air supply fan has increased to a constant rate (15%) (step S18).
If there is an increase (YES), the step-up for increasing the rotation speed is confirmed (step S19). Next, the current value I of the frame rod 7 that accompanies this increase in the number of rotations is read, and it is judged whether or not the current value I is the sampling current value Im or more (I ≧ Im) (step S20). In the case of (YES), steps S11 to S20 are repeated, and when the current value I becomes smaller than the sampling current value Im (NO), the current value I at that time is stored as the lower limit value, and the rotation speed at this lower limit value is stored. The rotation number of the air supply fan 4 is reduced to a state in which the rotation number is reduced by a certain amount (step S21), and is fixed to the corrected rotation number (step S22). If there is no increase (NO) in step 18, the process proceeds to step S22, and the rotation speed of the air supply fan 4 is fixed.

The control by the frame rod 7 is as follows.
As shown by the line 6D in FIG. 6, the fuel supply proportional valve 33 is set so as to be executed in a low combustion load region where the output is small. This is because the flame is closer to the burner flame mouth, and because the stability of the flame remarkably occurs during fluctuations in the rotational speed, the current value detected in this low combustion load range is used as the reference value. By executing the above control in the entire combustion load range, the optimum combustion state can be maintained in the entire load range as shown by the line E in FIG. 6F shows the state before correction.

Further, there is a concern that the frame rod 7 may gradually start to leak due to deterioration of insulation due to aging due to use, and that the flame rod 7 itself may deteriorate in flame detection sensitivity due to aging. Is concerned. Therefore,
When the lower limit current value changes due to the leakage current, the current value detected by the frame rod 7 (the output value detected by the combustion state detecting means) is corrected over time according to the amount of change. That is, when an upper limit value in which the current value of the frame rod 7 is higher than the already stored lower limit value by a certain amount is detected due to leakage current due to aging and deterioration of sensitivity, the upper limit value is stored as a new lower limit value, and , The rotational speed of the air supply fan 4 is controlled to be corrected by a constant rotational speed lower than the rotational speed at the new lower limit value, and the current value of the frame rod 7 is equal to or lower than the already stored lower limit value. Is detected, the rotational speed of the air supply fan 4 is controlled to return to the initial value.

When electric leakage occurs in the frame rod 7, the leakage current is detected by the frame rod 7 even when the rich / lean combustion burner 20 is not combusted (when the fire is extinguished). In this case, the total current value detected by the frame rod 7 increases by the amount of the current value detected during non-combustion, so the current value of the frame rod 7 during non-combustion is detected and stored. Every other time, the difference from the initial value (detection value at the time of non-combustion when first used) is added to the upper limit value and the lower limit value, and the result is used as a judgment reference value to control the rotation speed of the air supply fan 4 to be corrected. To do.

[0029]

As described above, according to the present invention (Claim 1), after the ignition of the rich / lean combustion burner, the rotation speed of the air supply fan is controlled to increase stepwise. It is possible to stabilize the combustion state, reduce the temperature rise of the flame mouth portion due to the solid fire, improve the durability of the rich-lean combustion burner, and improve the reliability.

Further, according to the present invention (Claim 2), while the change of the flame current value is monitored by the frame rod, the rotation speed is lower than the rotation speed at the lower limit current value near the point where the current value suddenly drops. Since the configuration is such that the rotation speed of the air supply fan is fixed in a state in which the number of air drops is reduced, the self-diagnosis of the combustion state is performed, while avoiding the flame lift state and the solid fire state, and in addition, regardless of the type of gas. Instead, the optimum combustion state can be maintained.

Further, according to the present invention (claims 3 and 4), when the insulation of the frame rod is deteriorated due to aging due to use, the rotation of the air supply fan is changed according to the change amount of the leakage current. Since the number is corrected, it is possible to maintain the optimal combustion state even if the flame rod has some leakage, and it is possible to extend the life of the flame rod.

Further, according to the present invention (Claim 5), the control by the control device is executed in a low combustion load region where the output of the fuel supply proportional valve is small, that is, in a region where the lift state of the flame remarkably occurs. Since it is configured, the control that reliably reflects the combustion state can be performed, and the above control is executed in the entire load range using the current value detected in this low combustion load range as the reference value (claim 6). It is possible to maintain the optimum combustion state in the entire load range.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of a water heater equipped with a combustion device of the present invention.

FIG. 2 is a partial cross-sectional view of a rich / lean combustion burner provided in a combustion device.

FIG. 3 is a diagram showing a relationship between a combustion amount and a rotation speed of an air supply fan showing an example of timer control.

FIG. 4 is a diagram showing a relationship between a flame current value generated by a frame rod and a rotation speed of an air supply fan.

FIG. 5 is a flowchart showing an example of frame rod control.

FIG. 6 is a diagram showing a relationship between a combustion amount and the number of rotations of an air supply fan showing an example of flame rod control.

[Explanation of symbols]

1 Combustion device 2 burner unit 20 Dark and light combustion burner 21 Main flame mouth 22 Light burn burner section 23 Secondary fire mouth 24 Dense burner section 3 Fuel supply system 30 gas supply pipe 31 nozzle holder 32 fuel nozzle 33 Fuel supply proportional valve 34 Yuanben 35 Capacity switching valve 4 Air supply fan 5 Hot water supply system 50 heat exchanger 51 water pipe 52 Hot water pipe 53 Water sensor 54 hot water thermistor 6 control device 60 timer 7 frame rod

Continued front page    F term (reference) 3K003 JA06 KA05 KB02 LA01 LA06                       NA04 NA07 NA08                 3K005 WA01 WB02 WC02 YA11 YA18                 3K017 AA01 AA02 AB01 AC01                 3K065 TA18 TB02 TC02 TD05 TE02                       TE07 TF03 TG01 TH04 TH16                       TM02 TN00 TN01 TN16

Claims (6)

[Claims] 1. A combination of a light burner burner section that burns a light gas having a high primary air ratio as a main flame and a rich burner burner section that burns a rich gas having a low primary air ratio as sleeve flame of a secondary flame. In the combustion device, which is provided with a rich-lean burner burner, and which is provided with a fuel supply proportional valve and an air supply fan for proportionally burning the rich-lean burner according to the required combustion amount, the rotation speed of the air supply fan is required to be the required primary air amount. The control device controls so as to stepwise increase the rotation speed of the air supply fan with respect to the combustion amount every time a certain time or more has elapsed after the combustion of the rich / lean combustion burner has started. Combustion device characterized by. 2. A light-burning burner section that burns a light gas having a large primary air ratio as a main flame, and a rich-burning burner portion that burns a rich gas having a low primary air ratio as sleeve heat of an auxiliary flame are combined. In a combustion device provided with a rich-lean burner, a fuel supply proportional valve for proportionally burning the rich-lean burner according to a required combustion amount, and an air supply fan, the main flame or / and A combustion state detecting means provided in the vicinity of the secondary flame and a control device for controlling the rotation speed of the air supply fan according to the output value detected by the combustion state detecting means are provided, When the combustion amount of the combustion burner is equal to or less than a certain amount and continues for a certain amount of time or more after the start of combustion, the number of revolutions of the air supply fan with respect to the amount of combustion is increased stepwise and detected by the combustion state detecting means. While detecting a change in output, the output value near the point where this output value starts to suddenly drop is stored as a lower limit value, and the rotation speed of the air supply fan is reduced to a constant rotation speed lower than the rotation speed at this lower limit value. Combustion device characterized by controlling so as to correct. 3. The combustion device according to claim 2, wherein the control device continues for a certain amount of time or less after the combustion of the rich / lean combustion burner is started and for a certain time or more, and the output value of the combustion state detecting means is the lower limit. When an upper limit value that is higher than the constant value is detected, this output value is detected while increasing the number of revolutions of the air supply fan with respect to the combustion amount in steps to detect a change in the output detected by the combustion state detecting means. The output value in the vicinity of abruptly descending is stored as a lower limit value, and the rotation speed of the air supply fan is controlled to be corrected to a state in which the rotation speed is lower than the rotation speed at the lower limit value by a constant value.
A combustion apparatus, wherein when the output value of the combustion state detecting means is less than or equal to the lower limit value, the rotation speed of the air supply fan is controlled to return to an initial value. 4. The combustion device according to claim 2 or 3, wherein the control device detects and stores the output value of the combustion state detecting means when the rich / lean combustion burner is not burning, and the difference from the initial value is the upper limit value. In addition to the lower limit value and the lower limit value, a combustion device is controlled so that the rotation speed of the air supply fan is corrected using the result as a judgment reference value. 5. The combustion device according to claim 2, 3 or 4, wherein the control by the control device is executed in a low combustion load region where the output of the fuel supply proportional valve is small. 6. The combustion device according to claim 2, 3 or 4, wherein the control by the control device is based on an output value detected in a low combustion load region where the fuel supply proportional valve output is small, in the entire combustion load region. A combustion device characterized by being adapted to be executed.