JPS5830499B2 - Combustion amount control method with two types of control modes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a combustion amount control method having two types of control modes for adjusting the output amount of a burner.

Conventionally, combustion output control of a burner has been performed by stopping combustion, since combustion becomes unstable due to the characteristics of the burner and the like when the combustion amount of the burner becomes small to a certain extent.

In other words, if the combustion amount instructed as a control output is greater than a certain value, the combustion amount is adjusted continuously or intermittently, and if it is less than a certain value, combustion is stopped until it reaches that value again. was.

Therefore, these methods have the disadvantage that when the control output is below a certain value, the furnace temperature adjustment is also stopped, resulting in large fluctuations in the furnace temperature.

Furthermore, even when the burner restarts combustion, the amount of combustion tends to be more than necessary, which is not preferable for the furnace, burner, etc.

The present invention has been made in view of the above-mentioned drawbacks of the conventional art, and its purpose is to improve the control performance for burners, etc., and to control the combustion amount by having two control modes that enable efficient use of the furnace, burners, etc. The purpose is to provide a method.

Next, the present invention will be explained with reference to the drawings, which are one embodiment.

FIG. 1 is a system diagram showing a control system of a heat treatment furnace that implements the control method according to the present invention.

In the figure, 1 is a heat treatment furnace provided with a vanina 2 and a temperature sensor 3.

The burner 2 receives fuel gas from a pipe 5 having a valve 4 disposed in the middle thereof.

Although combustion air is not shown, it is supplied in the same way as fuel gas.

Further, the sensor 3 measures the furnace temperature and sends the furnace temperature measurement value T to the PID calculator 6.

The PID calculator 6 calculates a control amount from the furnace temperature set value To input in advance, other constants, and the furnace temperature measurement value T,
It is input to the changeover switch 7 as a current type i (ΔT).

That is, the control output i(△T
) and the boundary value i (k) specified by the boundary value setter 8
The control output i (△T) is the boundary value i (k)
In the above cases, the connection is switched to the right side in the figure, and in other cases, the connection is switched to the left side.

In this case, when i (ΔT) and i (k) are equal, the switch is made to the right, but of course this is not limited to this.

Here, if the ratio of the value at the boundary between the stable and unstable regions to the maximum combustion amount of burner 2 is k (%, l), and the magnitude of the control output to produce this state is 1 (k), then , the boundary value setter 8 sets the preset ratio k
[Yes] is converted into a current type boundary value 1(k) and inputted to the changeover switch 7 and the ON-OFF time proportional converter 9.

Note that the value of the ratio is a characteristic value determined by the burner 2, and the magnitude of the set value can be adjusted.

Therefore, the PID calculator 6 operates directly when the changeover switch 7 is connected to the right side, and 0 when the changeover switch 7 is connected to the left side.
Actuator 1 via N-OFF time proportional converter 9
This will lead to 0.

The ON-OFF time proportional converter 9 outputs only a current equal to a constant value, that is, the boundary value i (k), for an output time t.

The amount of combustion is adjusted by

Output time t. is determined in proportion to the control output i(ΔT).

The actuator 10 is connected to the valve 4, and adjusts the flow rate by changing the rotation angle, that is, the opening degree, in proportion to the magnitude of the input current (2).

Therefore, when the control output i (△T) is the boundary value 1 (k) or more (stable region), the input current ■ is the control output i (△
T), and the opening degree of the valve 4 is continuously controlled (continuous control).

Further, when the controlled amount i (△T) is smaller than the boundary value i (k) (unstable region), the valve 4 is proportionally controlled for the 0N-OFF time by the 0N-OFF time proportional converter 9. .

Next, the calculations in the device will be specifically explained.

First, the PID calculator 1 calculates the deviation ΔT and the control output i(ΔT) using the following equation.

here To: Furnace temperature set value (described above) P, T1. T: PID constant It is.

Note that the control output i (△T) according to equation (2) is 4 mA
< i (△T ) <20 −・−・・−(
3) Decide the constant classes so that

The boundary value setter 8 converts the ratio □□□] to the boundary value i (k) according to the following equation.

The ratio k (%) is a variable amount determined according to the characteristics of the burner 2, and is usually around 30 yen.

Comparison calculation at changeover switch 7 (control output i(△T)
- boundary value i (k) ), the following two types of control are performed as described above.

1) When i(△T) -1(k)>0, I=i(△T) (mA) --(5
) Here, ■ is the input current of the actuator i (
k)<I≦20 (mA:)...
...-(6).

The relationship between the control output i (ΔT) and the input terminal ■ is shown in FIG.

1i) When i(△T)-i(k)<O, the output time t.

is the control output i in the ON-OFF time proportional converter 9
(ΔT).

Here, ts is a cycle time, which is an empirical value determined by the furnace structure, processing material, processing amount, etc., and is a variable amount, and is input in advance.

For example, one cycle (time ts
) The relationship between the elapsed time t and the input current value is as follows: The input current value between O≦t≦to is I −i (k)...
(8) The input current value between 1o<1<13 is I=0(9), and as long as i(△T)1(k)<O, (8
).

(9) is repeated.

The relationship between time t and input current (2) in this case is shown in FIG.

Subsequently, the actuator 10 adjusts the opening degree of the valve 4 using the input current (2).

As described above, the supply amount of fuel, etc., and therefore the furnace temperature are adjusted.

Note that although the example in which the furnace temperature is controlled by the combustion amount of the burner has been described above, the present invention can also be applied to heating/cooling control using a heat medium or the like in other devices.

Further, in FIG. 1, the broken line portion may be replaced with a microcontroller.

In this case, the microcontroller is programmed in advance with a furnace temperature set value To, a ratio k [φ], a PID constant T1. Tp and cycle time are stored and then controlled according to the schematic flow shown in FIG.

That is, first, the furnace temperature setting value To and the PID constant P.

T1. PID calculation is performed from T (steps 1, 3) and the furnace temperature measurement value T (step 2) (step 4).

Control output 1 (△T), which is the calculated value, is compared with the boundary value i (k), and depending on whether the control output i (△T) is smaller than the boundary value (k) or more than the cutting depth, one of the two methods described below is selected. A branch to either is made (steps 5-7).

If the control output l (△T) is greater than or equal to the boundary value i (k), then i
(ΔT) is taken as the output (step 8), and in other cases,
Furthermore, read the cycle time ts (step 9),
Calculate 0N-OFF time proportionality (step 10)
Output (step 11).

Thereafter, the state returns to the original state (step 12) and the steps described above are repeated.

In this way, since control is performed only by signals from the microcontroller, other attached equipment is not required, and the equipment can be simplified.

As is clear from the above explanation, according to the present invention, the changeover switch is continuously controlled according to the magnitude of the control output,
Since control is performed by switching to either OFF time proportional control, not only can a wide range of control be performed, but even when the control output is small, combustion is performed in a stable range and is controlled by combustion time, so the furnace Responsiveness to temperature fluctuations is improved and control accuracy can be improved.

Furthermore, since the amount of combustion is maintained at an appropriate level, the life of the furnace and heating elements (burners, heaters, etc.) can be extended, and the quality of processed products can be improved.

[Brief explanation of drawings]

Figure 1 is a system diagram of the control system of a gas fuel reactor that implements the method according to the present invention, Figures 2 and 3 are diagrams showing continuous control and ON-OFF time proportional control, and Figure 4 is a schematic flowchart of the microcontroller. FIG. 1...Furnace, 2...Burner, 3...
...Temperature sensor, 6...PID calculator, 7...
...Selector switch, 8...Boundary value setter,
9...0N-OFF time proportional converter, 10...
...actuator, To...furnace temperature set value, T...furnace temperature measurement value, △T...deviation,
i (△T)... Control output, i (k)...
··Boundary value.

Claims (1)

[Claims] 1. In the burner combustion amount control performed by calculating the control output from the deviation between the furnace temperature measurement value and the furnace temperature setting value, the control device is made to compare the control output with a preset boundary value, and the power of the control output is A combustion amount control force method having two types of control modes, characterized in that continuous control is performed when the control output is larger, and ON-OFF time proportional control is performed when the control output is smaller.