JPH02242014A - Combustion control device - Google Patents

Abstract

PURPOSE:To eliminate an influence caused by a delayed response of a thermo-couple at an initial stage of ignition, provide a stable ignited state, prevent a noise of resonance sound and further prevent a red heat of a burner plate by a method wherein an air fuel ratio correcting means is provided with a time counting means for counting an elapsed time after ignition and a reference temperature is set low until a predetermined time elapses after ignition. CONSTITUTION:In case that a temperature of a thermo-couple 15 is low and its output voltage is lower than a reference voltage Vs, an initial reference voltage Vs0 corresponding to an elapsed time (t) is calculated at an air fuel ratio correction part and a calculation of this initial reference voltage Vs0 is repeatedly carried out unless the elapsed time (t) exceeds a predetermined time (ta). In case that an output voltage V of the thermo-couple 15 is lower than the initial reference voltage Vs0, fuel gas of which fuel supplying volume is increased under a correction of fuel is injected out of a nozzle 13. Accordingly, much volume of fuel gas in respect to the combustion air is supplied in a mixing chamber 10b, resulting in that a gas rich state is attained and a positive ignition is attained. Thereafter, as the elapse time (t) after ignition to be counted with a timer part continues, the initial reference voltage Vs0 is gradually increased.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a combustion control system in which a burner is arranged in a combustion chamber and has an air-fuel ratio correction function that corrects the ratio between the amount of fuel supplied and the amount of combustion air supplied. Regarding the device, it is particularly effective in all-air burners where fuel and combustion air are premixed.

[Prior Art] For example, in a combustion device equipped with an all-air burner, the amount of combustion air supplied varies depending on the temperature of the burner plate even if the control state of the blower remains the same. For this reason, air-fuel ratio control is performed to correct the fuel supply amount so that an appropriate air-fuel ratio is obtained. In this air-fuel ratio control, for example, a thermocouple detects the temperature of the burner plate to determine whether a combustion temperature corresponding to an appropriate air-fuel ratio is obtained, and the output voltage is set as a reference voltage corresponding to an appropriate air-fuel ratio. Compare and correct excess or deficiency in fuel supply amount.

As a result, for example, at the initial stage of cold ignition such as initial ignition (if not re-ignited), the temperature of the burner plate is low, so more combustion air is supplied than during steady combustion, but at this time, Because the temperature of the thermocouple is low and its output voltage is insufficient, a fuel starvation condition is detected.

Therefore, since the burner is supplied with fuel in an amount that makes it gas richer than the appropriate air-fuel ratio at steady state, such cold
It can also be used to ignite a fire reliably.

After ignition, the thermocouple is heated over time, the amount of fuel supplied is corrected accordingly, and the blower and proportional valve are respectively controlled so that an appropriate air-fuel ratio is obtained.

As such a combustion control device, there is one that controls a blower based on the determined target heating amount, and controls a proportional valve by detecting the operating state such as the rotation speed of the blower.

[Problem to be Solved by the Invention] In this way, in a device that detects the temperature of the burner plate and corrects the fuel supply amount, in order to obtain a gas-rich state at the time of ignition, the corrected fuel supply amount must be The amount of fuel supplied during steady state must be sufficiently large.

Therefore, during steady combustion when the temperature of the burner plate is high to a certain extent, the relationship between the 1i flow value of the proportional valve and the rotational speed of the blower for supplying combustion air and fuel at an appropriate air-fuel ratio is shown by the solid line in Figure 6. In the case shown in H, the current value of the proportional valve during ignition must be considerably larger than the current value during steady combustion, as shown by the broken line I, and along with this, the air-fuel ratio changes. It is necessary to widen the correction width W1 sufficiently, at least to the side where the current value is increased.

As a result, in the conventional system, when the determined target heating amount is the minimum heating amount in the combustion region, the blower control state corresponds to the minimum heating amount, whereas the proportional valve control state corresponds to the minimum heating amount. The condition is subject to air/fuel ratio correction by a thermocouple. At this time, the temperature of the thermocouple has not risen sufficiently since it has just been ignited, so the fuel correction by the thermocouple will increase the amount of fuel by more than the amount that is actually insufficient. As a result, the amount of fuel supplied corresponding to the supplied combustion air cannot be obtained, and more fuel than the amount of fuel corresponding to the determined minimum heating amount is supplied.

At this time, as shown by the broken line J in FIG. 7, the output voltage of the thermocouple has a response delay, so it becomes a voltage that is significantly short of the thermocouple reference voltage 1 for the target heating amount. Therefore, as shown by the solid line K, the amount of fuel supplied will be excessive with respect to the target heating amount until the voltage of the thermocouple exceeds the reference voltage It takes time for the supply to decrease. Also, during this period, the air-fuel ratio is not maintained properly with respect to the supplied combustion air, resulting in excess fuel, which causes the burner plate to become red hot and the combustion state to become unstable. Combustion equipment such as water heaters with exhaust pipes that require extensions of exhaust pipes as necessary tend to generate noise such as resonance.

The present invention eliminates the influence of the response delay of a thermocouple at the initial stage of ignition in a total air burner in which combustion air is supplied by a blower, stabilizes the combustion state, and eliminates noise such as resonance and the red heat of the burner plate. It is an object of the present invention to provide a combustion control device that can prevent the combustion amount from occurring in the vicinity of the minimum heating amount and obtain a combustion amount corresponding to a target heating amount by eliminating excessive combustion amount especially near the minimum heating amount.

[Means for Solving the Problems] The present invention includes a burner disposed within a casing, a fuel control valve provided in a fuel supply path to the burner, and a blower for supplying combustion air to the burner. temperature detection means for controlling the fuel control valve and the blower according to a target heating amount and detecting the temperature of the burner, and supplying fuel to the burner according to the temperature detected by the temperature detection means with respect to a reference temperature. In the combustion control device, the air-fuel ratio correction means includes a timer that measures the elapsed time after ignition, and the air-fuel ratio correction means determines the correction amount of the supply amount. The technical means is to set the reference temperature low.

[Operation] In the present invention, since the temperature detected by the temperature detection means is low at the start of the ignition operation in the cold state, which is the initial ignition,
The amount of fuel supplied is large, and sufficient fuel is supplied to the supplied combustion air, resulting in gas richness and easy ignition.

On the other hand, the reference temperature is set low in order to correct the fuel supply amount until a predetermined period of time has passed after ignition. Therefore, after a certain amount of time has passed, the detected temperature exceeds the reference temperature even if the temperature detected by the temperature detection means does not become sufficiently high.

At this time, the supplied fuel is reduced, and the amount of fuel supplied can be reduced relatively quickly after ignition.

As a result, the target heating amount is quickly reached.

Therefore, at the initial stage of ignition, when the temperature of the thermocouple is not sufficiently higher than during steady combustion, it is less affected by the response delay of the temperature detection means, and the amount of fuel supplied can be quickly reduced.

[Effects of the Invention] In the present invention, since the reference temperature is set low until a predetermined time has elapsed after ignition, the fuel supply amount can be reduced relatively quickly, and the temperature detection means at the initial stage of ignition can be reduced. The influence of response delay can be reduced.

Therefore, it is possible to prevent the burner plate from becoming red hot, and the combustion state is stabilized, so that noise such as resonance noise is less likely to occur.

In addition, when using fuel that requires a certain amount of fuel correction relative to the supplied combustion air at the time of ignition, by setting the range of the fuel correction amount of the air-fuel ratio correction means to a certain extent, Since sufficient fuel can be supplied at the time of ignition, it is possible to ignite one fruit.

[Example] Next, the present invention will be explained based on examples.

In the gas water heater 1, the outline of which is shown in FIG. A blower 12 is provided below 10 to supply combustion air.

The blower 12 includes an impeller 12b inside a scroll casing 12a, and a motor (not shown) drives the impeller 12b.
drive the rotation. The scroll gauging 12a is provided with a nozzle 13 for ejecting fuel gas.

A large number of flame ports 11a are formed in the burner plate 11, and the water heater case 10 and the burner plate 11 are connected to the burner plate 11.
A secondary pneumatic burner is formed, and combustion exhaust gas is discharged to the outside of the water heater case 10 from an exhaust port (not shown). Furthermore, mixing chamber 1
01), a rectifying plate LOc provided with a large number of holes is disposed in order to evenly supply the air-fuel mixture supplied by the blower 12 to the burner plate 11.

In the combustion chamber 10a, a sparker electrode 14 for performing spark discharge and a thermocouple 15 for detecting the temperature of the burner plate 11 are provided near the burner plate 11.

Here, in order to prevent the thermocouple 15 from being directly affected by the flame, the flame port 11a is not formed in the vicinity of the thermocouple 15 in the burner plate 11.

A heat exchanger 16 connected to a water supply source and a hot water inlet (not shown) is provided in the combustion chamber 10a, and a flow rate sensor 17 is provided between the heat exchangers 16 and the flow rate to detect the amount of inflow water.
, an inlet water temperature thermistor 18 for detecting the temperature of incoming water is provided, and an outlet water temperature thermistor 19 for detecting the temperature of heated hot water is provided downstream of the heat exchanger 16.

The fuel pipe 2o that guides the fuel gas to the nozzle 13 includes a main solenoid valve 21 and a main solenoid valve 22 for shutting off the fuel gas in order from the upstream side, and a pressure on the downstream side of the fuel gas that is adjusted according to the current value. A governor proportional valve 23 is provided, respectively.

The control device 40 performs necessary control operations based on a pre-installed program centered on a microcomputer, and as shown in FIG. It consists of each functional section.

When the inflow of water into the heat exchanger 16 is detected, the ignition control unit 41 opens each electromagnetic valve 21, 22 in a predetermined sequence and performs ignition control to cause spark discharge at the sparker electrode 14.

The temperature control unit 42 determines the combustion amount for controlling the combustion control unit 43 based on the detection signals from the flow rate sensor 17, the inlet water temperature thermistor 18, and the outlet water temperature thermistor 19, and the temperature set by the controller 50.

The combustion control section 43 includes a blower control section 44 and a proportional valve control section 4.
5. It consists of each functional section of the air-fuel ratio correction section 46.

The blower control section 44 controls the voltage applied to the motor of the blower ll112 between the minimum voltage VIIin and the maximum voltage v +max according to the combustion amount determined by the temperature control control section 42 .

The proportional valve control unit 45 controls the rotation speed N of the motor of the blower fi12.
is detected, and the current value to the governor proportional valve 23 is controlled based on the detected rotational speed N.

Here, as shown by the solid line A in FIG. 3, the reference current value Is is set between the minimum rotation speed Ngiin and the maximum rotation speed N IIa
Determine.

The reference current value Is is corrected to a correction current value 1r with a correction width Wa between the broken line and the broken line in FIG. The valve 23 is energized with a correction current value Ir.

As a result, the current value I to the governor proportional valve 23 is, for example,
At the minimum rotation speed Nm1n of the blower 12, the current value is 11~■
2, and at the maximum rotation speed Nmax, the current value is 1
It is corrected between 3 and I4.

The air-fuel ratio correction unit 46 adjusts the output voltage of the thermocouple 15
The correction amount of the fuel supply amount is determined according to the correction amount, and the reference current value Is of the proportional valve control section 45 is corrected based on the correction amount.

Here, when the output voltage ■ of the thermocouple 15 is higher than the reference voltage Vs, the correction amount is determined to reduce the fuel supply amount, and when it is low, the correction amount is determined to increase the fuel supply amount. Determine the amount.

Here, as shown by broken lines C and D in FIG. 3, the fuel correction amount is determined so as to obtain a sufficient correction width Wa for the reference current value Is shown by solid line A. As shown, the ignitability at the time of ignition is improved by providing a sufficient increase correction amount, and the dashed line is used to cope with the case where the amount of combustion air supplied is reduced due to an extension of the exhaust pipe (not shown), etc. As shown in the figure, the reduction correction amount is also set so that the correction current value Ir is considerably smaller than the reference current value Is.

This reference voltage Vs is a constant voltage set based on the temperature of the burner plate 11 during steady combustion when the temperature of the burner plate 11 has become sufficiently high.
This is the reference value after a predetermined time ta (for example, 3 molecules WJ) has elapsed after ignition.

An initial reference voltage Vs is set as a reference value before a predetermined time ta has elapsed after ignition.

The initial reference voltage V s 6 is set in order to prevent the combustion amount from becoming excessive when the determined heating amount is around the minimum heating amount, and is shown in the single point g line E in Figure 4. The reference voltage Vs is set lower than the reference voltage Vs, and becomes the reference voltage Vs when the elapsed time t after ignition measured by the timer section 46a exceeds a predetermined time ta.

Here, in order to eliminate sudden changes in the air-fuel ratio, the voltage is gradually increased according to the elapsed time t after ignition measured by the timer section 46a, and becomes the reference voltage Vs after a predetermined time ta has elapsed.

Therefore, even if the output voltage V of the thermocouple 15 is the same, different fuel correction amounts are determined depending on the elapsed time t after ignition, and the amount of fuel gas is increased or decreased accordingly.

Furthermore, if the determined heating amount is not near the minimum heating amount, the temperature of the thermocouple 15 will rise relatively quickly, so if the output voltage of the thermocouple 15 becomes higher than the reference voltage Vs. At that point, the timer section 46a
, and the reference voltage Vs is set as the reference value.

Next, the operation of the gas water heater 1 of this embodiment having the above configuration will be explained with reference to FIG. 5, focusing on the control of the setting of the reference voltage Vs.

At time t, when the user operates a faucet (not shown) to start hot water supply and water flow is detected, the timer section 46a starts measuring time (step 1), and the ignition side... will be held.

In this ignition control, a voltage is applied to the blower 12 according to the combustion amount determined by the temperature control control section 42. Further, the governor proportional valve 23 is energized with a reference current value Is corresponding to the rotational speed N of the blower 12 and a corrected current value Ir corrected according to the output voltage (■) of the thermocouple 15.

If the temperature of the thermocouple 15 is low and its output voltage ■ is lower than the reference voltage Vs, the result is YE in step 2.
S), an initial reference voltage V s corresponding to the elapsed time t is calculated in the air-fuel ratio correction unit 46 (Step 3), and this initial reference voltage V s 6 is calculated if the elapsed time rWi1 does not exceed the predetermined time ta. (NO in step 4)
), repeated. At this time, the initial reference voltage Vso in the air-fuel ratio correction section 46 for determining the fuel correction amount
is lower than the reference voltage Vs.

The output voltage ■ of the thermocouple 15 is the initial reference voltage Vso
If it is lower, fuel gas whose fuel supply amount has been increased by fuel correction is ejected from the nozzle 13. Therefore,
In the mixing chamber 10b, a large amount of fuel gas is supplied to the combustion air, so that a gas-rich state is obtained and ignition is reliably achieved.

Thereafter, the initial reference voltage Vs gradually increases with the elapsed time t after ignition measured by the timer section 46a.

Further, as shown by the broken line F, the temperature of the thermocouple 15 also gradually rises after ignition, and at time t2, its output voltage becomes higher than the initial reference voltage Vso, which is being changed with the elapsed time t. On the contrary, the fuel supply amount decreases, as shown by the solid line G, and the combustion amount decreases.

At time t3, when the predetermined time ta has elapsed (YES in step 4), the reference value for determining the fuel supplement N,t is fixed to the reference voltage Vs (step 5), and from then on, the output voltage of the thermocouple 15 is is compared with the reference voltage Vs, and the fuel correction amount is determined according to the difference.

On the other hand, for example, if the determined heating amount is large and the output voltage (■) of the thermocouple 15 exceeds the reference voltage Vs before the predetermined time ta has elapsed (N
o), the timer unit 46a finishes measuring the time (step 6).
, immediately set the reference voltage Vs as a reference value (step 5),
The fuel correction amount is determined by comparison with the reference voltage VS.

As described above, in this example, the fuel supply amount can be reduced even if the temperature of the thermocouple 15 is low, so the conventional combustion control device that corrects the fuel supply amount based on a constant reference voltage can be used. In comparison, the amount of fuel supplied can be reduced quickly. In addition, even if the heating amount determined by the temperature control unit 42 is small and near the minimum heating amount, as in the conventional case,
It is not affected by the response delay of the thermocouple 15, and at the time rfjfl ts, the fuel supply amount can be reliably reduced to around the amount corresponding to the determined combustion amount.

In addition, since the correction width Wa of the air-fuel ratio control section 46 can be widened, the air-fuel ratio can be reliably corrected even if the supplied gases are made of slightly different raw materials or fuel with poor combustibility. Therefore, noise such as resonance noise is less likely to be generated, and red heat of the burner plate 11 can be prevented.Although a gas water heater is shown in this embodiment, a heater may also be used, and the heating source is limited to gas. However, it may also be a combustion device using petroleum or the like.

In this embodiment, a combustor is shown in which a ceramic burner plate is arranged inside the casing, but the burner plate may be made of metal. Effective when heat capacity is large.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the functional configuration of the control device for the gas water heater of this embodiment, Fig. 2 is a schematic diagram showing the configuration of the gas water heater of this embodiment, and Fig. 3 is a block diagram showing the configuration of the gas water heater of this embodiment. Characteristic diagram showing the relationship between the rotation speed and the current value of the governor proportional valve, No. 4
The figure is a time chart for explaining the operation in this embodiment, Figure 5 is a flowchart for explaining the operation in this embodiment, and Figure 6 is the rotation speed of the blower and the current value of the governor proportional valve in a conventional combustion control device. FIG. 7 is a time chart showing the operation of a conventional combustion control device. In the figure, 10... water heater case (casing), 11...
...Burner plate (burner), 12...Blower, 1
5...Thermocouple (temperature detection means), 20...
Fuel pipe (fuel supply path), 23... Governor proportional valve (fuel control valve), 40... Control device (combustion control device), 46
...Air-fuel ratio control section (air-fuel ratio correction means), 46a...
Timer section (timekeeping means).

Claims (1)

[Claims] 1) A burner is disposed within a casing, a fuel control valve is provided in a fuel supply path to the burner, and a blower is provided for supplying combustion air to the burner, and a target heating amount is provided. temperature detection means for controlling the fuel control valve and the blower according to the temperature and detecting the temperature of the burner; and a correction amount for the amount of fuel supplied to the burner according to the temperature detected by the temperature detection means with respect to a reference temperature. In the combustion control device, the air-fuel ratio correction means includes a timer for measuring the elapsed time after ignition, and the reference temperature is maintained at the reference temperature until a predetermined time elapses after ignition. A combustion control device characterized by setting a low value.