JPH02223723A - Controller of forced combustion type burning device - Google Patents

Abstract

PURPOSE:To prevent a flame failure by the life of a flame by making a fuel increased speed fast or a decreased speed of an air flow quantity fast when an air fuel ratio is transferred to a rich side and reversing its actuation when it is transferred to a lean side. CONSTITUTION:Because an air fuel ratio detection means 4 for detecting an air fuel ratio with the use of a flame temperature produces a time lag to the change of actual flame temperature formed in a combustion part 1, an air fuel ratio controller 5 makes a fuel increased speed fast with the use of a fuel supply means 2 by a rich control means 6 when the air fuel ratio is transferred to a rich side or the decreased speed of an air flow quantity fast with the use of a blower 3. On the other hand, when it is transferred to a lean side, a fuel decreased speed is made slow or the decreased speed of the air flow quantity is made slow with the use of a lean control means 7. As the result, a flame failure by the lift of a flame can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects an air-fuel ratio based on the temperature of a flame formed in a combustion section, and maintains the detected air-fuel ratio within an appropriate range. The present invention relates to a control device for a forced combustion combustion device that controls at least one of the amount of fuel supplied and the amount of combustion air.

[Prior art] In addition to supplying fuel to the combustion section, combustion air necessary for complete combustion of the fuel supplied to the combustion section is forcibly supplied to the combustion section, and the fuel is combusted in the combustion section. There is a forced combustion type combustion device that performs this.

In this forced combustion type combustion device, the fuel supplied to the combustion section must be completely combusted by the combustion air forcibly supplied to the combustion section. For this reason, at least one of the fuel supply amount and the combustion air space is controlled by the control device so that the air-fuel ratio is maintained within an appropriate range with excess air (lean).

Note that this control device η requires an air-fuel ratio detection means to detect the air-fuel ratio. As this air-fuel ratio detection means,
Some devices detect the air-fuel ratio based on the temperature of the flame formed in the combustion section. As shown in FIG. 5, this means that the air-fuel ratio is 0.
This takes advantage of the fact that the combustion speed of the flame is fast at 0.9, and the combustion speed becomes slower as the air-fuel ratio moves away from 0.9.

This is because when the temperature of the flame is detected (leaner than the stoichiometric air-fuel ratio (assuming combustion is at !lII)), as the temperature rises, the air-fuel ratio decreases (shifts to the rich side), and vice versa. As the temperature decreases, the air-fuel ratio increases (shifts to the lean side).In other words, the air-fuel ratio can be detected by comparing the flame temperature and the amount of combustion.

For example, a thermocouple (
Some use thermocouples. This thermocouple is
When the air-fuel ratio changes and the flame temperature changes, it takes time to heat up or cool down.

Similarly, when the amount of combustion changes, it takes time for the thermocouple to heat up or cool down. Therefore, a time error x occurs between the actual change in the combustion state and the change in the combustion state detected by the thermocouple.

Therefore, if the air-fuel ratio changes and the combustion amount changes, the actual combustion state and the combustion state detected by the thermocouple will differ. The control device then controls at least one of the fuel supply amount or the combustion air supply amount based on a value different from the actual combustion state detected by the thermocouple, and attempts to maintain the air-fuel ratio within an appropriate range. do.

As a result, as shown in FIG. 10, the air-fuel ratio repeatedly overshoots and converges to the target air-fuel ratio.

Then, the speed at which the conventional air-fuel ratio is shifted to the rich side,
The speed at which the air-fuel ratio was shifted to the lean side was set at a similar speed. In other words, in order to perform air-fuel ratio control, the control device
The rate at which fuel increases and decreases, or the rate at which air flow increases and decreases, was kept the same. As a result, in the control of the conventional control device, the time when the combustion state exists on the rich side from the target air-fuel ratio due to overshoot and the time when the combustion state exists on the lean side are basically the same length.

[Problems to be Solved by the Invention] FIG. 11 shows time charts 1 to 1 showing the relationship between the output of the thermocouple and the state of the flame when the air-fuel ratio is changed. Note that the solid lines in the figure indicate the air-fuel ratio shifted from an appropriate value to the rich side, and the solid line ■ indicate the air-fuel ratio shifted from the appropriate value to the lean side.

As can be seen from the time chart in Figure 11, when the air-fuel ratio is shifted to the lean side, the combustion speed slows down, the flame lifts, and misfire occurs in a short time (15 seconds in this example), or vice versa. In contrast, shifting the air-fuel ratio to the rich side increases the combustion rate, and it takes a long time (
In this example, there is a margin of 200 seconds).

In other words, in the actual combustion state, the time when the target air-fuel ratio is on the rich side may be long, but the longer the time when the air-fuel ratio is on the rich side, the higher the possibility of reflux and misfire. Become.

For this reason, in conventional control devices, as mentioned above, the time when the actual combustion state exists on the rich side from the target air-fuel ratio due to overshoot is basically the same length as the time when the actual combustion state exists on the lean side. Therefore, the actual combustion state remained on the lean side for a long time, and there was a high possibility of misfire.

The present invention was made in view of the above circumstances, and its purpose is to shorten the time during which the actual combustion state exists on the lean side from the target air-fuel ratio, and to prevent misfires due to flame lift. The purpose of the present invention is to provide a control device for a forced combustion type combustion device.

[Means for Solving the Problems 1] In order to achieve the above object, the control device for the forced combustion type combustion apparatus of the present invention includes a combustion section that burns fuel, as shown in the schematic block diagram of FIG. 1, a fuel supply means 2 for supplying fuel to the combustion section 1, and a combustion air necessary for combusting the fuel supplied to the combustion section 1 by the fuel supply means 2 to be forced into the combustion section 1. Air blower f supplied to section 1
i3, and air-fuel ratio detection means 4 for detecting the air-fuel ratio based on the temperature of the flame formed in the combustion section 1.
and a control device 5 that corrects and controls at least one of the amount of fuel supplied by the fuel supply means 2 or the amount of air blown by the blower 3 according to the air-fuel ratio detected by the air-fuel ratio, and maintains the air-fuel ratio within an appropriate range. In the forced combustion type combustion apparatus, the control device 5 includes a rich control means 6 that increases the rate of increase in fuel or decreases the rate of air flow when shifting the air-fuel ratio to the ridge side, and controls the air-fuel ratio. The technical means is to include lean control means 7 that slows down the rate of decrease in fuel or slows down the rate of increase in air flow when shifting to the lean side.

1. Operation The operation of the control device for the forced combustion type combustion apparatus configured as described above will be explained.

b) The amount of fuel supplied to the combustion section increases, the amount of combustion air supplied decreases, and the actual air-fuel ratio shifts to the rich side, or the number of combustion sections increases, causing the flame temperature to increase. The air-fuel ratio control when the amount increases will be explained.

As the actual flame temperature increases, the flame temperature detected by the air-fuel ratio detection means also increases. However, the flame temperature detected by the air-fuel ratio detection means has a time delay with respect to the actual change in flame temperature, so a temperature lower than the actual temperature is detected.

When the air-fuel ratio detection means detects a temperature lower than the actual temperature, the control device attempts to maintain the air-fuel ratio within an appropriate range based on the temperature lower than the actual flame temperature. That is, the rich control means operates to return the air-fuel ratio to a proper value after shifting the air-fuel ratio to the rich side.

The rich control means shifts the air-fuel ratio to the rich side over a long period of time by increasing the rate of increase in fuel or increasing the rate of decrease in air flow. As a result, the time period during which the air-fuel ratio is richer than the target air-fuel ratio becomes longer than in the past.

Conversely, if the amount of fuel supplied to the combustion section decreases, the amount of combustion air increases and the actual air-fuel ratio shifts to the lean side, or the combustion section decreases, Air-fuel ratio control when the flame temperature drops will be explained.

As the actual flame temperature decreases, the flame temperature detected by the C1 air-fuel ratio detection stage also decreases. However, since the flame temperature detected by the air-fuel ratio detection means has a time delay with respect to the actual change in flame temperature, a temperature higher than the actual temperature is detected.

When the air-fuel ratio detection means detects a temperature higher than the actual flame temperature, the control device attempts to maintain the air-fuel ratio within an appropriate range based on the temperature higher than the actual flame temperature. In other words,
Lean control means is activated to shift the air-fuel ratio to the lean side and return the air-fuel ratio to an appropriate value.

The lean control means slowly shifts the air-fuel ratio to the lean side by slowing down the rate of decrease in fuel or slowing down the rate of increase in air flow. As a result, the time during which the air-fuel ratio is leaner than the target air-fuel ratio can be suppressed to be shorter than in the past.

[Effects of the Invention] Since the present invention is configured as described above,
This produces the effects described below.

With the air-fuel ratio detection means, when the air-fuel ratio shifts to the rich side, the time to shift to the ridge side becomes longer, and conversely, when the air-fuel ratio shifts to the lean side, the time to shift to the lean side becomes shorter. Become.

Therefore, it is possible to shorten the time that the air-fuel ratio exists on the lean side from the target air-fuel ratio, and prevent misfires due to flame lift. On the other hand, the time it takes to stay on the rich side is longer than before, but there is a long margin of time for problems (for example, misfires and backfires) to occur due to being on the rich side. No problem will occur even if the time it exists is a little longer than before.

[Embodiment 2] Next, a control device for a forced combustion type combustion apparatus of the present invention will be explained based on an embodiment shown in the drawings.

(First Embodiment) FIG. 2 shows a schematic diagram of a bypass mixing type gas water heater to which the present invention is applied.

This gas water heater is roughly divided into a combustion section 1 that burns gas.
1, a gas supply pipe 20, a water pipe 30, and a control device 40.

The combustion passage 10 includes a ceramic surface combustion type burner 12.
is placed inside. Upstream of this burner 12, the gas supplied from the gas supply pipe 20 is connected to the burner 12.
- A blower 13 is attached that forcibly supplies the combustion air necessary for combustion in the surface combustion section 11 to the combustion section 11. Further, downstream of the combustion passage 10, a combustion section 1 is provided.
Exhaust port for discharging the combustion gas generated in step 1 (not shown)
is provided.

The gas supply pipe 20 is a fuel supply means of the present invention, and supplies fuel gas to a nozzle 21 that opens on the inner periphery of the centrifugal fan 14 of the blower 13. Note that the gas flowing out from the nozzle 21 is mixed with combustion air by the air flow generated by the blower 13 and is supplied to the combustion section 11 . The gas supply piping 20 is connected to the main solenoid valve 22 and the main solenoid valve 23 from the downstream side.
, a proportional valve 24 are sequentially provided.

The downstream side of the proportional valve 24 is branched into two parts, one of which is provided with a switching solenoid valve 25 and the other with an orifice 26.

The main solenoid valve 22, the main solenoid valve 23, and the switching solenoid valve 25 control the gas supply pipe 20 to 17F!
The proportional valve 24 is closed, and its opening ratio changes depending on the amount of electricity supplied to adjust the gas 1 supplied to the nozzle 21.

The water pipe 30 is connected at one end to a water supply source and at the other end to a hot water supply inlet, and exchanges heat generated by combustion of gas with water flowing inside the water pipe 30. It includes a heat exchanger 31 that heats, and a bypass water channel 32 that bypasses this heat exchanger 31.

The water pipe 30 upstream of which branch of the heat exchanger 31 and the bypass waterway 32 has a governor valve function that keeps the amount of water flowing into the heat exchanger 31 and the bypass waterway 32 constant even if the water pressure flowing into the heat exchanger 31 and the bypass waterway 32 changes. An electric water flow control device 33 is provided which combines the functions of a water flow control valve and a water flow control valve that adjusts the water flow. The bypass waterway 32 is also provided with a throttle valve 34 that can adjust the amount of water passing through the bypass waterway 32 and open and close the bypass waterway 32 .

Note that the throttle ratio of the electric water flow control device 33 is the same as that of the heat exchanger 31.
In order to regulate the total amount of water flowing into the bypass waterway 32, it is provided to be the same as the throttle valve 34 or smaller than the throttle valve 34. In addition, an electric water flow control device 33 and a throttle valve 34
uses a geared motor to drive a valve body that can open and close the waterway as a means to adjust the amount of water.

As shown in FIG. 3, the control device 40 is composed of a microcomputer 41, a relay circuit 42, and a drive circuit 43, and controls the burner 12 according to the outputs of a controller 44 and various sensors operated by the user. a sparker 45 for igniting, a main solenoid valve 22, a main solenoid valve 23, a proportional valve 24, a switching solenoid valve 25, an electric water flow control device 33,
The throttle valve 34 is energized and controlled.

Various sensors of the control device 40 include a flame rod 46 that detects the flame of the burner 12, a thermocouple 47 that detects the air-fuel ratio by detecting the temperature of the flame of the burner 12, and an electric motor. Potentiometers 48 and 49 that are linked to the water flow control device 33 and the valve body of the throttle valve 34 and detect the opening degree of the valve body, a rotation speed sensor 50 that detects the rotation speed of the blower 130, a heat exchanger 31, and 16 of the bypass water channel 32. An inlet water temperature sensor 51 that detects the temperature of flowing water, a temperature sensor 52 that detects the temperature of hot water that has passed through the heat exchanger 31, and an outlet water temperature sensor that detects the temperature of the mixed hot water that has passed through the heat exchanger 31 and the bypass waterway 32. temperature sensor 53,
A Mercury detection sensor 54 is provided to detect the amount of water flowing into the heat exchanger 31 and the bypass waterway 32.

Next, combustion control by the computer 41 will be briefly explained.

The combustion control in this embodiment is a fan-driven type.

In the fan preceding type of this embodiment, the rotational speed of the blower 13 is determined so that the amount of air blown is obtained according to the combustion amount determined by the control bag W40, and from the rotational speed of the blower 13, the gas is is obtained in the combustion section 11, the proportional valve 24
and the opening/closing of the switching solenoid valve 25. and,
The amount of gas supplied to the combustion section 11 is corrected based on the temperature of the flame detected by the thermocouple 47 to keep the air-fuel ratio constant. In addition, the rotation speed of the air blower fi 13 is corrected based on the temperature of the flame detected by the thermocouple 47.
C. It may be provided so that the gas supply 1 does not change.

Specifically, when the user operates a switch connected to the hot water supply inlet and a water flow is generated in the water pipe 30, the water amount detection sensor 54
detects the flow of water and combustion begins. The amount of combustion after the start of combustion is determined by the amount of water obtained by various sensors, the temperature of water entering, the temperature of hot water passing through the heat exchanger 31, the temperature of mixing water, the temperature of hot water exiting, etc., so that the set temperature set by the controller 44 can be obtained. Determined by The voltage of the blower 13 is controlled so as to supply the burner 12 with an air volume corresponding to the determined combustion amount. Then, the proportional valve 24 and the switching solenoid valve 25 are controlled to be energized so that a gas amount corresponding to the rotational speed of the blower 13 and the temperature of the flame of the burner 12 is obtained.

The amount of combustion is determined so that the temperature of the water passing through the heat exchanger 31 is maintained at a temperature above (for example, 60° C.) at which water generated by combustion (drain water) does not adhere to the heat exchanger 31. .

Next, water flow control by the computer 41 will be briefly explained.

The throttle valve 34 is fixed at an appropriate opening calculated from the incoming water temperature, the set temperature, the temperature of the hot water that has passed through the heat exchanger 31, and the outlet temperature. Note that this fixation is set so that the flow rate flowing through the bypass waterway 32 is twice the amount of water flowing through the heat exchanger 31. In other words, the bypass waterway 32 and the heat exchanger 3
The ratio of flow resistance to 1 is approximately 2:1 by the throttle valve 34. Further, the opening degree of the throttle valve 34 is fixed when the amount of water entering is small or when the temperature of hot water coming out is lowered, and the opening degree of the throttle valve 34 is fixed so that the opening degree is calculated according to the amount of water entering and the temperature of hot water coming out. Energization is controlled.

Further, the electric water flow rate control device 33 is controlled to be energized so as not to exceed the maximum flow rate required to obtain the hot water temperature.

Next, the rich control means 55 and lean control means 56 programmed in the computer 41 will be explained.

As described above, the air-fuel ratio in the combustion section 11 is controlled by changing the gas supply amount according to the output of the thermocouple 47.

The electromotive force of the thermocouple 47 is as shown in FIG.
It corresponds to the amount of combustion. Further, as shown in FIG. 5, when the air-fuel ratio changes, the combustion rate changes. When the air-fuel ratio shifts to the richer side than the target air-fuel ratio, the combustion speed becomes faster and the flame temperature becomes higher. Conversely, when the air-fuel ratio shifts to the lean side, the combustion speed becomes slower and the flame temperature becomes lower. Therefore, by correcting and controlling the gas amount so that an electromotive force corresponding to the combustion amount is obtained, the air-fuel ratio can be maintained at an appropriate value.

Then, when the temperature of the flame detected by the thermocouple 47, that is, the electromotive force is lower than the electromotive force corresponding to combustion 1, the microcomputer 41 of the control device 40 of this embodiment
It is determined that the combustion state has shifted to the leaner side than the target air-fuel ratio, and the rich control means 55 is activated. This rich control means 55 shifts the air-fuel ratio to the rich side, and in this embodiment, the proportional valve 24 and the switching solenoid valve 25
control and increase the amount of gas supplied. The rate of increase is faster than the rate of decrease by the lean control means 56 described above, and the rate of increase is, for example, 500 kcal/
limited to s.

Conversely, the microcomputer 41 is connected to the thermocouple 4
When the flame temperature, that is, the electromotive force detected in step 7, is higher than the electromotive force corresponding to the combustion amount, it is determined that the combustion state has shifted to the richer side than the target air-fuel ratio, and the lean control means 5
6 is activated. The proportional control means 56 shifts the air-fuel ratio to the lean side, and in this embodiment, the proportional valve 2
4 and the switching solenoid valve 25 to reduce the gas supply amount. The rate of decrease is slower than the rate of increase by the rich control means 55 described above, and the rate of decrease is as follows:
For example, it is limited to 30 kcal/s.

Note that the thermocouple 47 changes due to changes in the temperature of the flame.
The temperature does not change suddenly even when heated or cooled.
Therefore, if the air-fuel ratio fluctuates or the combustion amount changes, and the actual flame temperature changes, the flame temperature detected by the thermocouple 47 will have a temporal error between it and the actual flame temperature. occurs.

Next, the operation of air-fuel ratio correction will be briefly explained.

α) Immediately after the amount of combustion increases, such as immediately after the amount of water detected by the water amount detection sensor 54 increases, or immediately after the set temperature of the controller 44 is set to a high temperature side, the time a to
As shown in b, the temperature detected by the thermocouple 47 does not follow the actual flame temperature and lags behind.

In other words, due to the delay in the detection speed of the thermocouple 47,
The thermocouple 47 outputs an electromotive force corresponding to a temperature lower than the actual flame temperature. Therefore, the microcomputer 41 determines that the combustion state has shifted to the leaner side than the target air-fuel ratio, and operates the rich control means 55. The rich control means 55 rapidly increases the amount of gas supplied. By rapidly increasing the amount of gas supplied, the air-fuel ratio quickly shifts to the rich side, the combustion speed increases in a short period of time, and the actual combustion amount also increases in a short period of time. As a result, the actual flame temperature increases rapidly.

As the temperature of the actual flame increases, the electromotive force of the thermocouple 41 exceeds the electromotive force set according to the rotational speed of the blower 13 (time b).

Since the actual air-fuel ratio was in a rich state between times a and b, the thermocouple 47
L, outputs a higher electromotive force than the electromotive force set according to the rotational speed of the blower 13 (times b to c), therefore,
The microcomputer 41 determines that the combustion state is moving toward the richer side l\ than the target air-fuel ratio, and operates the lean control means 56.

The lean control means 56 slowly reduces the amount of gas supplied. As the gas supply amount decreases, the air-fuel ratio slowly shifts to the lean side, the combustion speed slowly slows down, and the actual combustion amount also slowly decreases. As a result, the actual flame temperature decreases over a long period of time.

As the actual temperature of the flame decreases, the electromotive force of the thermocouple 47 falls below the electromotive force set according to the rotational speed of the blower 13 (time c).

In the second half of time b・-〇, the actual air-fuel ratio was in a lean state, so the thermocouple 47 overshooted again, and the electromotive force was lower than the electromotive force set according to the rotational speed of the air blower t1!13. Output electromotive force (time C-'-
d) Therefore, the microcomputer 41 determines that the combustion state has shifted to the leaner side than the target air-fuel ratio, and operates the rich control means 55.

The rich control means 55 and the lean control means 56 work alternately, and the actual air-fuel ratio repeatedly overshoots the target air-fuel ratio, until the actual air-fuel ratio converges to the target air-fuel ratio.

β) Immediately after the amount of water detected by the water amount detection sensor 54 decreases, or immediately after the set temperature of the controller 44 is set to a low temperature side, etc., contrary to the above example, immediately after the amount of combustion decreases, as shown in FIG. As shown at times e to f, thermocouple 4
The temperature detected by No. 7 does not follow the actual flame temperature and lags behind it.

In other words, due to the delay in the detection speed of the thermocouple 47,
The thermocouple 41 outputs an electromotive force corresponding to a temperature higher than the actual flame temperature. Therefore, the microcomputer 41 determines that the combustion state has shifted to the richer side than the target air-fuel ratio, and activates the lean control means 56. The lean control means 56 slowly reduces the amount of gas supplied. As the amount of gas supplied slowly decreases, the air-fuel ratio slowly shifts to a leaner side than the target air-fuel ratio, the combustion speed gradually slows down, and the actual combustion amount also slowly decreases.

As a result, the actual flame temperature also decreases slowly.

As the actual temperature of the flame decreases, the electromotive force of the thermocouple 47 becomes lower than the electromotive force set according to the rotational speed of the blower 13 (time f).

During times e to f, the actual air-fuel ratio was in a lean state, so the thermocouple 47 overshot to the lean side and the electromotive force was lower than the electromotive force set according to the rotational speed of the blower 13. Output power (time f to g),
Therefore, the microcomputer 41 determines that the combustion state has shifted to the richer side than the target air-fuel ratio, and operates the rich control means 55. This rich control means 5
5, the gas supply amount is quickly increased. By increasing the amount of gas supplied, the air-fuel ratio quickly shifts to the rich side, the combustion speed increases in a short period of time, and the actual combustion amount also increases quickly. As a result, the actual flame temperature also rises quickly.

As the temperature of the actual flame increases, thermocouple 47
The electromotive force exceeds the electromotive force set according to the rotational speed of the blower 13 (time g). In other words, time f~
In the latter half of g, the actual air-fuel ratio is in a rich state, so the thermocouple 47 again overshoots and outputs a higher electromotive force than the electromotive force set according to the rotational speed of the blower 13 ( time g~11), therefore,
The microcomputer 41 determines that the combustion state has shifted to a richer side than the target air-fuel ratio, and operates the lean control means 55.

That is, the lean control means 56 and the rich control means 55
act alternately, causing the actual air-fuel ratio to repeatedly overshoot and converge to the target air-fuel ratio.

As shown above, when the combustion amount changes, the actual air-fuel ratio repeatedly overshoots the target air-fuel ratio and converges to the target air-fuel ratio. When overshooting this overshoot, the actual air-fuel ratio takes a longer time to shift to the richer side than the target air-fuel ratio, and conversely, the time it takes to shift to the leaner side becomes shorter.

In other words, it is possible to shorten the time period during which the actual air-fuel ratio is on the opposite side of the target air-fuel ratio. Therefore, misfires due to flame lift can be prevented.

On the contrary, the time it remains on the rich side is longer than before, but since there is a long margin of time for backfire to occur due to existence on the rich side, the time it remains on the rich side is longer than before. Even if it does, no backfire will occur.

Note that although the air-fuel ratio changes due to overshoot, the range of the change is within a proper air-fuel ratio range, and no inconvenience occurs in combustion.

In addition, in the above embodiment, the case where the combustion amount changes is shown as an example, but when the gas supply amount or the combustion air amount changes, the same operation as above can be used to determine the actual The air-fuel ratio repeatedly overshoots and converges to the target air-fuel ratio. And when repeating overshoot,
The actual air-fuel ratio takes longer to shift to the rich side than the target air-fuel ratio, and conversely, it takes less time to shift to the lean side.

Therefore, the time that the air-fuel ratio remains on the lean side from the target air-fuel ratio can be shortened, and misfires due to flame lift can be prevented.

The factors that cause the gas supply amount to change during combustion include:
Possible causes include changes in the amount of gas used by other gas appliances connected to the same gas supply piping and fluctuations in the gas supply pressure. Furthermore, even if the rotational speed of the blower is constant, the amount of combustion air supplied during combustion changes due to the change in air amount that occurs when the ceramic burner 12 changes from a low temperature state at the initial stage of ignition to a high temperature (room temperature). Alternatively, an air resistance object may be placed at the opening for introducing combustion air into the combustion passage 10.

(Second example) FIG. 8 shows a schematic configuration diagram of the second embodiment.

In this embodiment, when the air-fuel ratio is shifted to the lean side by the lean control means 56, the air-fuel ratio is initially shifted to the lean side quickly,
This will later shift to the lean side at a slow speed.

In addition, in the forced combustion type combustion apparatus of this embodiment, as in the two-legged embodiment, the blower is driven at a rotational speed according to the combustion amount determined by the control device 40, and the rotational speed of the blower 13,
This is a fan-driven type in which the opening degree of the proportional valve 24 is determined by the temperature of the flame detected by the thermocouple 47.

As in the embodiment described above, the lean control means 56 determines that the air-fuel ratio is rich and starts subtracting the amount of current supplied to the proportional valve 24 when the temperature detected by the thermocouple 47 exceeds the target temperature. The lean control means 56 of this embodiment includes a lean transition speed switching means 57 to change the transition speed to the lean side.

This lean moving speed switching means 57 has a counting means 58.
, rapid transition means 59 , and low speed transition means 60 . The lean movement speed switching means 57 including the run I means 58, the rapid transition means 59, and the low speed transition means 60 is programmed into the microcomputer 41 of the control device v40.

When the temperature detected by the thermocouple 47 exceeds the target temperature and subtraction of the amount of current flowing through the proportional valve 24 is started, the counting means 58 calculates the total amount of current that has been subtracted.

The rapid transition means 59 speeds up the subtraction speed of the amount of current supplied to the proportional valve 24 until the total amount of subtraction counted by the counting means 58 reaches a predetermined value.

The gradient of this subtraction speed is set to be faster, for example, by 2/3, than the gradient of the addition speed of the proportional valve energization amount by the rich control means 55. In other words, the speed at which the air-fuel ratio shifts to the lean side is set to be slightly slower than the speed at which the air-fuel ratio shifts to the rich side.

The low-speed shifting means 60 slows down the speed at which the proportional valve energization amount is reduced when the total amount of subtraction counted by the counting means 58 reaches a predetermined value. To give a specific example, the speed at which the proportional valve energization amount is subtracted by the rapid transition means 59 is set to 1.
/10.

As a result, when the total amount subtracted by the counting means 58 reaches a predetermined value, the speed at which the air-fuel ratio shifts to the lean side becomes very slow.

Next, the above operation will be briefly explained using the time chart shown in FIG.

Immediately after the combustion amount increases due to the action of the control device I1.40, the temperature detected by the thermocouple 47 does not follow the actual flame temperature and lags, as shown at times a1 to b1 in Fig. 9. .

As a result, thermocouple 47 becomes thermocouple 4γ
Due to the delay in the detection speed, an electromotive force corresponding to a temperature lower than the actual flame temperature is output. Therefore, the microcomputer 41 determines that the combustion state has shifted to the leaner side than the target air-fuel ratio, and operates the rich control means 55. This rich control means 55 rapidly increases the amount of gas supplied. By rapidly increasing the amount of gas supplied, the air-fuel ratio quickly shifts to the rich side, and the actual flame temperature quickly rises by 10 degrees.

As the temperature of the actual flame increases -■-, the thermocouple 4
The electromotive force of No. 7 exceeds the electromotive force set according to the rotational speed of the blower 13 (time b1).

Since the actual air-fuel ratio was in a rich state between times a1 and b1, the thermocouple 47 outputs a higher electromotive force than the electromotive force set according to the overshoot and the rotation speed of the blower 13. (Time [1b1~・dl).

When the electromotive force of the thermocouple 47 exceeds the set electromotive force (b1), the means 58 to the counter 1 starts counting the total amount of the proportional valve energization amount subtracted, and the rapid transition means 59 is activated. Since the rapid transition means 59 reduces the opening degree of the proportional valve 24 at a high speed, the actual air-fuel ratio rapidly shifts to the lean side. As a result, the actual air-fuel ratio quickly approaches the target air-fuel ratio.

Then, when the total amount of decrement IT counted by the counting means 58 reaches a predetermined value (time C1), the slow shifting means 60 operates instead of the rapid shifting means 59. Since this low speed transition means 60 reduces the opening degree of the proportional valve 524 at a slow speed, the actual air-fuel ratio slowly shifts to the lean side, and the actual flame moves to the lift at a slow speed. Head towards.

As the actual temperature of the flame decreases, the electromotive force of the thermocouple 41 falls below the set electromotive force at time d1.

During the latter half of the period C1 to d1, the actual air-fuel ratio is in a lean state, so the output of the thermocouple 47 overshoots toward the lean side. The rich control means 55 then operates and opens the proportional valve 24 at a relatively far speed. Then, the actual air-fuel ratio shifts to the rich side, and the actual flame decreases toward backfire.

Thereafter, the rich control means 55 and the lean control means 56 work alternately, and the actual air-fuel ratio repeatedly overshoots the target air-fuel ratio, until the actual air-fuel ratio converges to the target air-fuel ratio. In addition, when overshooting to the rich side for the second time, since the overshoot time is short, the rapid transition means 5 is used.
9 to the low speed transition means 60, the rich control means 55 operates.

Note that this embodiment can suppress misfires caused by riff I and shorten the time period during which the engine overshoots toward the rich side. In other words, the difference between the actual air-fuel ratio and the target air-fuel ratio can be reduced, and the actual combustion state can be brought closer to the ideal combustion state than in the first embodiment.

In this embodiment, the total amount of Wit reduction is counted to switch the speed of shifting to the lean side, but a timer may be used to switch the speed.

(Modification) Although an example is shown in which a thermocouple is used as the air-fuel ratio detection means, other temperature detection means may be used as long as the temperature of the flame can be detected.

Although we have shown an example in which the rich control means and lean control means are programmed into a microcomputer, it is also possible to configure the rich control means and lean control means by using discrete circuits that combine operational amplifiers, etc., without using a microcomputer. It's okay.

Although the combustion control method is a fan-driven type, there are also other pond combustion control methods, such as a type that controls the amount of fuel supplied first (for example, a proportional valve-driven type) and an independent type that controls the amount of air flow and the amount of fuel supplied independently. The present invention may be applied to the system.

Although we have shown an example in which the speed of transition to the rich side and the speed of transition to the lean side are controlled only by increasing or decreasing the amount of fuel supplied, it is also possible to The speed of transition to the rich side and the speed of transition to the lean side may be controlled only by increasing or decreasing the amount.

Further, although a water heater with a bypass waterway is shown as an example, the present invention may be applied to a forced combustion type combustion device such as a combustion type heating device as well as a water heater without a bypass waterway.

Further, although an example using gas as fuel has been shown, the present invention may also be applied to a combustion device using liquid fuel such as kerosene or heavy oil.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 7 show a first embodiment of the present invention, in which FIG. 2 is a schematic configuration diagram of a bypass mixing type gas water heater, FIG. 3 is a schematic block diagram of a control device, and FIG. 4 is a graph showing the relationship between the combustion amount and the target output of the thermocouple, Fig. 5 is a graph showing the air-fuel ratio and combustion speed, and Fig. 6 explains the change in the air-fuel ratio when the combustion amount is increased. FIG. 7 is a time chart 1 for explaining changes in the air-fuel ratio when the combustion amount is reduced. Fig. 8 and Fig. 9 show a second embodiment of the present invention, Fig. 8 is a schematic diagram of a forced combustion type combustion device, and Fig. 9 shows a change in the air-fuel ratio when the combustion amount is increased. It is a time chart for explanation. Fig. 10 is a time chart showing the actual change in the air-fuel ratio when the C air-fuel ratio is corrected by a conventional control device, and Fig. 11 is a time chart showing the relationship between the air-fuel ratio, misfire, and flashback. In the figure: 1... Combustion section 2... Fuel supply means 3.
...Blower 4...Air-fuel ratio detection means 5...Control device 6...Rich control means 7...Lean control means

Claims (1)

[Scope of Claims] 1) A combustion section that burns fuel, a fuel supply means for supplying fuel to the combustion section, and combustion necessary to combust the fuel supplied to the combustion section by the fuel supply means. a blower that forcibly supplies air to the combustion section; and an air-fuel ratio detection means for detecting an air-fuel ratio based on the temperature of a flame formed in the combustion section, A forced combustion type combustion apparatus comprising: a control device that corrects and controls at least one of the amount of fuel supplied by the fuel supply means or the amount of air blown by the blower to keep the air-fuel ratio within an appropriate range; is equipped with a rich control means that increases the rate of increase in fuel or decreases the rate of air flow when the air-fuel ratio shifts to the rich side, and reduces the decrease in fuel when the air-fuel ratio shifts to the lean side. 1. A control device for a forced combustion type combustion device, characterized by comprising lean control means for slowing down the speed or slowing down the rate of increase in the amount of air blown.