JPH05332532A - Combustion controller - Google Patents

Abstract

PURPOSE:To improve control characteristics at the time of abrupt change of a combustion amount due to load change, a target value change, etc., while maintaining an optimum combustion zone by stopping an integral operation when signs of a limit deviation presence signal and an integral regulation signal are equal. CONSTITUTION:Integral trend judging means 32 judges that an integral operation output DELTAI is in a direction for releasing a limit if the relationship between an output of a limit deviation judging means 31 and a speed type integral regulation calculation signal DELTAI of speed type integral calculating means 23, i.e., both have different signs, and maintains an ON state of switch means 25, thereby conducting a normal integration. On the contrary, if both have equal signs, it judges that the output 61 is in a direction for increasing a limit, and turns OFF the means 25, thereby forcibly stopping the integral operation. Thus, a stable combustion can be obtained, and controllability at the time of a combustion amount change due to load change, a target value change, etc., can be improved while maintaining an optimum combustion zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device used in various combustion furnaces such as an industrial boiler, a steel heating furnace, a chemical heating furnace, and the like, and particularly in connection with load changes and target value changes. The present invention relates to a combustion control device that improves transient response characteristics of changes in combustion amount.

[0002]

2. Description of the Related Art Generally, in an industrial boiler, various combustion furnaces, etc., fuel and air are mixed and burned. In this combustion state, the fuel and air are closely related. Therefore, it greatly changes depending on the ratio of fuel to air (hereinafter referred to as an air-fuel ratio or an excess air ratio). Generally, the excess air ratio μ is expressed by an arithmetic expression of excess air ratio μ = actual air amount / theoretical air amount based on the theoretical air amount under the theoretical complete combustion condition of fuel, and depending on the actual air amount, In other words, the combustion state changes greatly depending on the magnitude of the excess air ratio μ.

By the way, in an actual combustion state, μ = 1.
It can be said that it is in the optimum combustion zone when it is about 02 to 1.10. Therefore, when the excess air ratio μ becomes larger than the optimum combustion zone equivalent value, the exhaust gas heat loss becomes large because the heated air that is not involved in combustion is discharged from the chimney as it is,
Along with this, the combustion efficiency decreases, but pollution due to the influence of NOx and the like occurs. On the contrary, when the excess air ratio μ becomes smaller than the optimum combustion zone equivalent value, the heat loss due to incomplete combustion becomes large, and the combustion efficiency also decreases and black smoke is generated in terms of pollution.

Therefore, the combustion of the combustion furnace of this kind should not always deviate from the optimum combustion zone regardless of the steady state or the excessive state, that is, the excess air ratio μ should always be maintained within a predetermined range. Need to control. FIG. 3 is a diagram showing a configuration of a conventional heating furnace combustion control device realized based on the above idea.

In this apparatus, a burner 1a is installed on a predetermined wall portion of a heating furnace 1, and burner (combustion generator) 1a is supplied with fuel and air from a fuel supply passage 2 and an air supply passage 3, respectively.
Is supplied to heat the object to be heated 1b in the heating furnace 1 by mixing the fuel and air to heat the material to be heated 1b, for example, to heat the raw material in the pipe 4, and then to the next step (not shown).

At this time, after the temperature of the raw material heating furnace outlet is detected by the temperature detector 5, the detected temperature is guided to the temperature adjusting means 6 as a feedback signal PV, where the target temperature S is set.
The deviation (SV-PV) between V and the feedback signal PV is calculated. Then, a PI (proportional / integral) or PID (proportional / integral / derivative) adjustment calculation is executed so that this deviation becomes zero, and the adjustment calculation signal is used as a command signal A of the fuel flow rate and the air flow rate to control the fuel flow rate. System and air flow control system. In many cases, the command signal A is a signal obtained by adding and synthesizing the feedforward control signal associated with the change in the raw material flow rate to the adjustment calculation signal. The fuel flow rate control system and the air flow rate control system employ a double cross limit control method.

Among them, the fuel flow rate control system side has a fuel flow rate limiting means 7 having an intermediate value selecting means 7a and two coefficient means 7b and 7c. The signal A and the air flow rate detection signal F _A proportional to the air flow rate are divided into the signal obtained by dividing the predetermined air-fuel ratio μs by the dividing means 8 into the coefficient (1 + K ₁ ) of the coefficient means 7b.
The intermediate value D is selected from the signal B obtained by multiplying the output signal of the dividing means 8 and the signal C obtained by multiplying the output signal of the dividing means 8 by the coefficient (1-K ₂ ) of the coefficient means 7c. The value D is supplied to the fuel flow rate adjusting means 9 as the target fuel flow rate D.

In the fuel flow rate adjusting means 9, adjustment calculation is performed so that the deviation between the target fuel flow rate D limited by the fuel flow rate limiting means 7 and the fuel flow rate F _F detected by the fuel flow rate detector 10 becomes zero. Is executed, and the obtained adjustment calculation signal is applied to a flow rate adjusting valve (which may be a solenoid valve or a variable speed pump or the like) 11 which is a fuel operating end provided in the fuel supply path 2 to variably adjust the fuel flow rate. ..

On the other hand, the air flow rate control system side has an air flow rate limiting means 13 which also has an intermediate value selecting means 13a and two coefficient means 13b and 13c. The coefficient means 13b is added to the command signal A and the fuel flow rate signal F _F from the fuel flow rate detector 10.
The intermediate value H between the signal E obtained by multiplying the coefficient (1 + K ₄ ) of the above and the signal G obtained by multiplying the fuel flow rate signal F _F by the coefficient (1-K ₃ ) of the coefficient means 13c similarly. Select and
A signal M obtained by multiplying the intermediate value H by the planned excess air ratio μs of the coefficient means 14 is supplied to the air flow rate adjusting means 15 as a target air flow rate.

In this air flow rate adjusting means 15, the planned air excess rate μs is limited by the air flow rate limiting means 13.
The target air flow rate M and the air flow rate detector 16
The adjustment calculation is executed so that the deviation from the signal F _F proportional to the air flow obtained through the square root calculation means 17 becomes zero, and the obtained adjustment calculation signal is used as the fuel supply path 3 The air flow rate is variably adjusted by applying it to a flow rate control valve (which may be a solenoid valve or a variable speed pump or the like) 18 which is an air operation end provided in the. The functions of the fuel flow rate limiting means 7 and the air flow rate limiting means 13 will be specifically described below.

The fuel flow rate limiting means 7 is composed of two coefficient means 7.
b, but have 7c, of which the coefficient unit 7b coefficient ₍₁ + K 1) (where, K _1> 0), the coefficient unit 7c coefficient (1-K ₂₎ (where, K _2> 0) has a relationship.
Signals obtained by dividing the air flow rate signal F _A by the planned air-fuel ratio μs by the dividing means 8 are input to the coefficient means 7b and 7c, respectively. Therefore, the output signal B of the coefficient means 7b and the output signal C of the coefficient means 7c are expressed by the following equations. B = (1 + K ₁ ) · F _A / μs …… (1) C = (1-K ₂ ) · F _A / μs …… (2)

Therefore, in the intermediate value selecting means 7a, the fuel flow rate command signal A, the output signal B and the output signal C are compared, and the signal D corresponding to the intermediate value is restricted.
Output as. That is, (a) when C ≦ A ≦ B, D = A (b) when C <B <A, D = B (c) when A <C <B, D = C

[0013] This means that the fuel flow rate command signal A
Means that it is limited by the planned upper limit value B and lower limit value C. Here, F _A / μs indicates the theoretical fuel flow rate calculated from the air flow rate, which means that the fuel flow rate command signal A is limited within a predetermined upper and lower limit value for the theoretical fuel flow rate.

On the other hand, the air flow rate limiting means 13 has two coefficient means 13b and 13c. Among them, the coefficient means 13b has a coefficient (1 + K ₄ ) (where K ₄ > 0) and the coefficient means 13c has a coefficient (1- K ₃ ) (however, K ₃ > 0). The fuel flow rate signal F _F from the fuel flow rate detector 10 is input to these coefficient means 13b and 13c, respectively. Therefore, the output signal E of the coefficient means 13b,
The output signal G of the coefficient means 13c is expressed by the following equation. E = (1 + K ₄ ) · F _F …… (3) G = (1−K ₃ ) · F _F …… (4)

Therefore, in the intermediate value selecting means 13a, the air flow rate command signal A, the output signal E and the output signal G are compared,
Among these, the one corresponding to the intermediate value is output as the limited signal H. That is, (d) when G ≦ A ≦ E, H = A (b) when G <E <A, H = E (c) when A <G <E, H = G

[0016] This means that the air flow rate command signal A
Is limited by the upper limit value E and the lower limit value G proportional to the fuel flow rate signal F _F , and the target air flow rate signal M of the air flow rate obtained by multiplying the upper limit value E and the lower limit value G is also limited. Indicates.

FIG. 4 shows the signals A, B, and
It is a figure which shows the magnitude relationship of C, E, and G. As is clear from this figure, in the steady state, the fuel flow rate intermediate value selection unit 7,
It is shown that the air flow rate intermediate value selection unit 13 selects the fuel flow rate and the air flow rate command signal A.

Next, FIG. 5 shows that in FIG. 4, K ₁ = K ₃ ,
And K ₂ = K _4, the response of the fuel supply system is a diagram showing the temporal change in the excess air ratio μ when slightly faster than the response of the air supply system.

That is, the steady state excess air ratio μ is controlled to the planned excess air ratio μs, but due to a sudden change in the target value or a sudden change in the raw material flow rate (load), for example, at time t ₁ , the fuel flow rate and the air flow rate are changed. When the command signal A suddenly increases,
The air-fuel ratio decreases excessively to (μs-K ₁ ) and then
After a while, it returns to the steady state again.

When the command signal A for the fuel flow rate and the air flow rate suddenly decreases at time t ₂ , the excess air ratio μ rises excessively to (μs + K ₂ ), and after a while, it returns to the steady state. Return.

On the other hand, when the response of the fuel supply system is slightly slower than the response of the air supply system, the temporal change of the excess air ratio μ is the opposite of that of FIG. 5, but in any case, the excess air ratio μ is the planned air. It is limited within a predetermined range above and below the excess rate μs.

[0022]

By the way, in recent plant operation, flexibility and speedup are becoming very important points, and even in the combustion control device, it is possible to cope with load change and target value change. It is demanded to be able to respond quickly, and it is strongly demanded that the limit of response be maximized in relation to the quality of products.

However, in the conventional combustion control device, as described above, when the steady state or the load change is small, or when the load change or the target value change is changing slowly, the air-fuel ratio falls within the predetermined range. The combustion efficiency can be increased while maintaining the combustion efficiency, and combustion with less pollution can be realized. However, when the command signal A for the fuel flow rate and the air flow rate changes significantly due to a sudden change in load change or target value change, the heating furnace outlet temperature is There is a problem that the overshoot greatly occurs and the controllability is greatly impaired.

The reason is that, when the command signal A for the fuel flow rate and the air flow rate changes abruptly, the fuel flow rate control system and the air flow rate control system impose upper and lower limits on the measured values F _A and F _F of the other party. As it follows the command signal A, if the limiting operation of the limiting means 7 and 13 is caught, the characteristics of the combustion system will change when viewed from the temperature controller 6. Therefore, if the temperature adjusting means 6 performs the PI or PID adjustment calculation while being caught in the limit without knowing any change in the characteristics, the PI or PID is calculated.
The accumulation effect by the I (integration) operation in the above works, and even if the deviation becomes zero, the accumulated amount by the integration operation cannot be cut off. As a result, the command signal A, which is the operation output of the temperature adjusting means 6, increases, and the temperature of the raw material overshoots accordingly.

Therefore, the above-mentioned combustion control device has a problem that the controllability is greatly deteriorated especially when the target value or the load is changed abruptly, and it is strongly demanded to improve the combustion control characteristics. ..

The present invention has been made in view of the above-mentioned circumstances, and while ensuring safe and stable combustion and maintaining an optimum combustion zone, a rapid change in the combustion amount due to a load change, a target value change, etc. An object of the present invention is to provide a highly reliable combustion control device with improved control characteristics at the time.

[0027]

In order to solve the above-mentioned problems, the invention corresponding to claim 1 mixes the fuel supplied from the fuel supply source and the air supplied from the air supply source and burns them. In the combustion control device that heats the heating target,

Proportional / integral or proportional / integral / differential adjustment calculation is executed so that the deviation between the detected temperature of the object to be heated and the target temperature is zero, and the obtained adjustment calculation signal is used to command the fuel flow rate and the air flow rate. An upper limit / lower limit limit value obtained from the adjusting means outputting as a signal and signals related to the air flow rate and the fuel flow rate, which are control objects opposite to each other, is given, and the command signal received from the adjusting means is limited to the upper / lower limit value. The fuel flow rate limiting means and the air flow rate limiting means that output while limiting the value, and the corresponding fuel flow rate using the outputs of the fuel flow rate limiting means and the air flow rate limiting means and the signals related to the fuel flow rate and the air flow rate, respectively. , Fuel flow rate adjusting means and air flow rate adjusting means for variably adjusting the air flow rate, and input / output of one or both of the fuel flow rate limiting means and the air flow rate limiting means It provided between, the input and of the limiting means
Limit deviation determining means for determining whether or not the command signal deviates from the upper / lower limit limit value based on the output signal, and an integration trend from the sign relationship between the output of the limit deviation determining means and the integral adjustment calculation signal. The combustion control device is provided with an integration trend determination means for making a determination and stopping the integration operation when the signs are the same.

[0029]

Therefore, the invention according to claim 1 takes the above-mentioned means, so that when the change of the command signal of the fuel flow rate and the change of the air flow rate is small or the change is slow, the command signal is changed. Since the upper and lower limit values of the limiting means are not caught, for example, the input / output difference signal of the limiting means becomes zero, and as a result, the normal adjusting operation is performed without stopping the integrating operation of the adjusting means. continue.

On the other hand, when the command signal is above the limiting means,
If the lower limit value is caught, turn on the limiting means.
The output difference signal has a value other than zero, and the limit deviation determining means determines that the command signal deviates from the upper limit value or the lower limit value. In this case, the integral trend judging means judges that the integral operation is in the direction of canceling the limitation when the sign of the output of the limit deviation judging means and the sign of the integral adjustment calculation signal are different signs, and the integral operation is not stopped. Not performed, normal integration operation continues.

However, when the command signal is caught by the limit value of the limiting means and has the same sign in the integral trend judging means, it is judged that the integral operation is in the direction of expanding the limit, and the integral operation is performed. Stop.

This means that the proportional / integral / derivative operation of the adjusting means is normally performed when the load change or the target value change is small or changes slowly in the steady state.
The advantages of the conventional device described above are fully utilized.

On the other hand, when the load and the target value change drastically and the command signal is caught in the limiting operation, the normal integrating operation is performed when the integrating operation is in the direction of canceling the limiting operation. Is in the direction of expanding the limit, the normal integration operation is forcibly stopped to completely prevent the integral accumulation effect due to the integration operation while being caught in the limit operation, thereby preventing a large overshoot of the control amount. It can be completely eliminated, and the control characteristics and safety can be greatly improved.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example in the case of being applied to, for example, a heating furnace outlet temperature control device, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. Will be described.

First, the temperature adjusting means 2 for obtaining the command signal A of the fuel flow rate control system and the air flow rate control system.
0 has been devised. That is, the temperature adjusting means 20
Is to provide a speed type PI or speed type PID adjustment calculation function, while separating the PI or PID operation to execute the adjustment operation while effectively utilizing the property of the I operation.

Specifically, the deviation calculating means 21 for obtaining the deviation between the detected temperature PV _n from the temperature detector 5 and the furnace outlet target temperature SV _n, and the deviation e _n obtained by this deviation calculating means 21 are respectively set. Speed type proportional calculation means 22, speed type integral calculation means 23 and speed type differential calculation means 24 for individually performing P, I or P, I, D adjustment calculation, and connection to the output side of this speed type integration calculation means 23 A switch means 25 which is turned on / off by receiving an on / off control signal from the outside, and a speed type integral adjustment calculation signal ΔI and a speed type proportional calculation means 22 taken out through the switch means 25.
Output of the speed type proportional adjustment calculation signal ΔP and the output of the speed type differential calculation means 24, the speed type differential adjustment calculation signal ΔD
And adding means 26 for outputting a speed-type regulating signal △ MV _n by adding the bets, fuel flow rate and air flow rate command signal is a position type manipulation outputs a speed-type regulating signal △ MV _n obtained by the addition means 26 A speed type-position type signal converting means 27 for obtaining A.

Second, the signal at the input / output end of the fuel flow rate limiting means 7, that is, the signal D limited from the fuel flow rate command signal A
The restriction deviation determining means 31 for determining whether the command signal A is within the range of BC or deviating from B or C is provided by subtracting. The command signal A
Is within the range of B-C, A = D and the output of the limit deviation determining means 31 becomes zero.

Thirdly, it is provided between the output side of the limit deviation judging means 31 and the output side of the speed type integral calculating means 23, and the signs of these outputs are the same sign or different signs, that is, the speed type. For the deviation of the limit of the command signal A obtained by the integration operation of the integral calculating means 23, it is judged whether the limit is canceled or the limit is expanded, and the direction is expanded. This is because there is provided an integral trend judging means 32 for stopping the integral operation by turning off the switch means 25 during the period. Next, the operation of the apparatus configured as described above will be described, and hereinafter, the operation of the improved components of the apparatus will be mainly described.

First, the temperature adjusting means 20 shows the case where the PID adjusting operation is performed in the speed type. In this speed type PID calculation, the calculation is executed according to the following equations (5) and (6). _{△ MV n = K P {(} e n -e n-1) + (△ t / T I) e n + (T D / △ t) · (e n -2e n-1 + e n-2)} ... (5) MV _n = MV _{n −1} −ΔMV _n (6)

However, in the above equation, K _P : proportional gain, T
_I : integration time, T _D : derivative time, en: current deviation, e
_n-1 : previous deviation, e _n-2 : previous previous deviation, Δt: control cycle, MV _n-1 : previous operation amount (previous command signal A), ΔMV
_n : change amount of operation amount (speed type adjustment signal), MV _n : current operation amount (current command signal A).

Therefore, as the temperature adjusting means 20, the deviation calculating means 21 uses the target value SV _n and the furnace outlet temperature PV _n.
And the deviation e _n = (SV _n −PV _n ) is calculated and then supplied to the respective computing means 22 to 24. Here, the velocity type proportional operation unit 22, the equation (5) _{from, △ P = K P · (} e n -e n-1) look, also likewise the velocity type integral calculation unit 23 the (5) _{from, △ I = K P · e} n · (△ t / T I) look, the more velocity type differential operation means 24, based on the same equation _{(5), △ D = K P · T} D · (e _n −2e _n−1 + e _n−2 ) / Δt is calculated.

Further, by adding and synthesizing the outputs of the respective computing means 22 to 24 in the adding means 26, the manipulated variable change amount ΔMV _n is obtained and then introduced into the speed type / position type signal converting means 27, where The above equation (6) is calculated to obtain the command signal A for the fuel flow rate and the air flow rate.

Therefore, the command signal A for the fuel flow rate and the air flow rate is obtained as described above. At this time, the command signal A
If the change in the fuel cell flow rate is small, the command signal A is in the range of BC, so the input signal A and the output signal D of the fuel flow rate limiting means 7 are
Are equal to each other, and the output ΔL of the limit deviation determining means 31 is ΔL = A−D = 0

Therefore, it is determined that the command signal A is not caught in the limiting operation. As a result, the integral trend judging means 3
2 is, for example, when ΔL is multiplied by ΔI, ΔL · ΔI = 0
Therefore, the integral operation is not forcibly stopped,
It is possible to take advantage of the function of the conventional device.

On the other hand, when the command signal A of the fuel flow rate and the air flow rate from the temperature adjusting means 20 changes abruptly, the command signal A is caught in the limiting operation exceeding the signal B or C. At this time, even if the fuel flow rate limiting means 7 is operating normally, ΔL = A−D> 0 or ΔL = A−D <0, and the limit deviation determining means 31 determines that there is a limit deviation, The output ΔL is sent to the integral trend judging means 32.

Here, in the integral trend judging means 32, the relationship between the output of the limit deviation judging means 31 and the speed-type integral adjustment calculation signal ΔI of the speed-type integral calculating means 23, that is, when the two have different signs, the integration is performed. It is determined that the operation output ΔI is in the direction of eliminating the limitation, and the ON state of the switch means 25 is maintained as it is, so that the normal integration is performed. On the other hand, if the two have the same sign, it is determined that the integral operation output ΔI is in the direction of expanding the limit, and the switch means 25 is turned off to forcibly stop the integral operation. Table 1 below summarizes the operation of the present apparatus as described above.

[0047]

[Table 1]

Therefore, in the device of the present invention, while the command signal A is caught by the fuel flow rate limiting means 7, the temperature adjusting means 2 is used.
The accumulation effect due to the integration operation of 0 is eliminated, the temperature overshoot is eliminated, and it greatly contributes to safety.

Incidentally, FIG. 2 is a diagram for comparing the responses of the conventional temperature control device and the temperature control device of the embodiment of the present invention with respect to a change in target value. FIG. 2A shows the response of the temperature PV to the change in the target value, and FIG. 2B shows the response of the operation output of the temperature adjusting means 20, that is, the command signal A of the fuel flow rate and the air flow rate, to the change in the target value. ing.

As is apparent from these figures, in the case of the conventional apparatus, the temperature characteristic 41a greatly overshoots with respect to the change of the target value, and the fuel flow rate and air flow rate command signal A (42a) also greatly overshoots. ..

On the other hand, in the temperature control device of the embodiment of the present invention, when the limiting operation is caught, the temperature adjusting means 20 is used.
By controlling the integration operation of, the accumulation effect due to the integration operation can be completely eliminated, and the temperature characteristic 4 as shown in FIG.
2a was obtained, which means that the overshoot disappeared and the control characteristics were greatly improved. Further, the operation output of the temperature adjusting means 20, that is, the command signal A of the fuel flow rate does not have the problem of overshooting as shown by the characteristic 42b of FIG. 2B, and sufficiently safe combustion can be realized.

Therefore, by obtaining the above characteristics, it can be expected to make a great contribution to the industrial world which is approaching the full-scale flexible era for the 21st century.

The present invention is not limited to the above embodiment. In the above embodiment, the limit deviation determining means 31 and the like are provided on the fuel flow rate control system side, but these limit deviation determining means 31 and the like may be provided, for example, corresponding to the air flow rate control system side, or both of them are controlled. The system may be provided with the limit deviation determining means 31 or the like, and the integration operation may be controlled by OR logical sum.

Further, although the switch means 25, the limit deviation judging means 31, the integral trend judging means 32 and the like have been described as hardware, they are processed by software when using a computer. Therefore, in this case, it may be possible to realize without the switch means 25. Further, in the above-described embodiment, the example in which the heating furnace outlet temperature control device is applied has been described, but the present invention is not limited to this, and may be similarly applied to various combustion furnace combustion control devices such as a boiler combustion control device. Besides, the present invention can be variously modified and implemented without departing from the scope of the invention.

[0055]

As described above, according to the present invention, one or both of the fuel flow rate limiting means and the air flow rate limiting means are provided to give a predetermined limit value to the command signals of the fuel flow rate and the air flow rate. Whether or not there is a limit deviation is judged from the input / output difference signal, and when the sign of the limit deviation signal and the integral adjustment signal according to this judgment are the same sign, it is judged that the integration operation is in the direction of expanding the limit. Since the integral operation is stopped, safe and stable combustion can be ensured, and the controllability when the amount of combustion changes due to load changes or target value changes, etc. can be improved while maintaining the optimum combustion zone, and extremely reliable. A high combustion control device can be provided.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a combustion control device according to the present invention.

FIG. 2 is a comparison diagram of response characteristics of the device of the present invention and the conventional device.

FIG. 3 is an overall configuration diagram of a conventional device.

FIG. 4 is a diagram showing a relationship between an upper limit and a lower limit for command signals of fuel flow rate and air flow rate.

FIG. 5 is a diagram showing an example of a temporal change of an excess air ratio.

[Explanation of symbols]

1a ... Combustion generator, 1b ... Object to be heated, 5 ... Temperature detector,
7 ... Fuel flow rate limiting means, 9 ... Fuel flow rate adjusting means, 10 ...
Fuel flow detector, 11 ... Flow control valve, 13 ... Air flow control means, 15 ... Air flow control means, 16 ... Air flow detector, 18 ... Flow control valve, 20 ... Temperature control means, 22 ... Velocity type proportional calculation Means, 23 ... Velocity type integral calculation means, 24 ...
Speed type differential operation means, 25 ... switch means, 26 ... addition means, 27 ... signal conversion means, 31 ... limit deviation determination means,
32 ... Integral trend judging means.

Claims (1)

[Claims] 1. A combustion control device for heating an object to be heated by mixing and burning fuel supplied from a fuel supply source and air supplied from an air supply source, the detected temperature and the target temperature of the object to be heated. The control means executes proportional / integral or proportional / integral / derivative adjustment calculation so as to make the deviation of zero, and outputs the obtained adjustment calculation signal as a command signal of fuel flow rate and air flow rate, and control objects opposite to each other. And a fuel flow rate limiting means for outputting a command signal received from the adjusting means while limiting the command signal received from the adjusting means with the upper and lower limit values. Using the flow rate limiting means and the outputs of the fuel flow rate limiting means and the air flow rate limiting means and the signals relating to the fuel flow rate and the air flow rate, the corresponding fuel flow rate and air flow rate can be controlled. A fuel flow rate adjusting means and an air flow rate adjusting means for changing and adjusting, and one or both of the fuel flow rate limiting means and the air flow rate limiting means are provided between the input / output terminals, and based on the input / output signals of the limiting means. Limit deviation determining means for determining whether or not the command signal deviates from the upper / lower limit limit values, and the integral operation expands the limitation based on the sign relation between the output of the limit deviation determining means and the integral adjustment calculation signal. A combustion control device comprising: an integration trend determination means for stopping the integration operation when moving in the direction.