JPH0459371B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides temperature control for controlling a heated object within a heating zone to a uniform temperature in a furnace having a plurality of heating zones that are adjacent to each other and have temperature interference, without providing partition walls between the heating zones. It is related to the device. In order to heat the object to be heated in the heating furnace to a uniform temperature, the inside of the heating furnace is divided into a plurality of adjacent heating zones, and the temperature in each heating zone is controlled independently to each target temperature. is being carried out. However, in order to obtain high temperature control accuracy in such cases, it is necessary to reduce mutual interference between the heating zones, so partition walls must be provided between the heating zones, which complicates the structure of the heating furnace. Another drawback was that the heating furnace was expensive. The present invention was made against the background of the above-mentioned circumstances, and its purpose is to provide a partition wall between the heating zones in a furnace having a plurality of adjacent heating zones that interfere with each other in temperature. It is an object of the present invention to provide a temperature control device that heats an object to be heated to a uniform temperature without any heating. In order to achieve such an object, the temperature control device of the present invention includes: (1) a plurality of temperature sensors provided in each of the plurality of heating regions and outputting a temperature signal representing the temperature of the heating region; (2) (3) a plurality of heating devices provided in each of the plurality of heating regions to heat the heating region; (3) comparing a predetermined target temperature with the temperature of each heating region represented by the temperature signal; adjusting means for calculating the deviation and outputting a control signal corresponding to each of the heating areas so that the deviation becomes zero; and adjusting each control signal based on the degree of temperature interference between the heating areas. Cross calculation means for calculating respective operation signals representing operation amounts corresponding to the heating areas, and a calculation control device for causing the heating device to heat each of the heating areas according to the operation signals. shall be. In this way, the heating device for heating each heating zone can respond not only to the control signal corresponding to the heating zone, but also to the control signals corresponding to other heating zones and the degree of temperature interference between the heating zones. Since it is operated in accordance with the operation signal calculated based on this, even in a furnace that does not have partition walls between heating zones and has relatively large temperature interference, the object to be heated can be heated extremely uniformly. In other words, while conventionally the temperature of each heating zone was controlled independently by minimizing the temperature interference between the heating zones, the temperature control device of the present invention controls the temperature based on the degree of temperature interference between the heating zones. Then, the operation signal for the heating area is calculated based on the control signal corresponding to the heating area and the control signal corresponding to the other heating area that affects the heating area, and the temperature between the heating areas is calculated. Since the heating region is heated by the heating device in response to an operation signal that takes interference into account in advance, extremely high temperature control accuracy can be obtained. Further, according to another aspect of the present invention, the arithmetic and control device responds to other heating regions other than a predetermined heating region of the heating region among the control signals output by the adjustment means. The present invention is characterized in that it further includes updating means for holding the control signal for a predetermined period of time and periodically updating the control signal after the predetermined period of time. In this way, the temperature of the predetermined heating area is continuously controlled by the operation signal that is continuously changed by the adjusting means and the cross calculating means, and the temperature of the other heating area is controlled by the updating means. Since the temperature is controlled in accordance with the operation signal calculated based on the control signal periodically updated by , the temperature control system becomes more stable and higher temperature control characteristics can be obtained. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below based on the drawings. In FIG. 1, a heated object 12 placed in a furnace 10 is conveyed by rollers 14 in a direction perpendicular to the feeding direction of the heated object 12, That is, thermocouples 16, 18, 20 as temperature sensors and burners 22, 24, 26 as heating devices are installed in the width direction of the furnace 10. Therefore, the inside of the furnace 10 is divided into a first heating area A, which is mainly heated by the burner 22 and whose temperature is detected by the thermocouple 16, and a first heating area A, which is mainly heated by the burner 24 and whose temperature is detected by the thermocouple 18. The second heating area B, which is detected, and the third heating area C, which is mainly heated by the burner 26 and whose temperature is detected by the thermocouple 20, are formed without providing a partition wall in the width direction of the furnace 10. ing. Therefore, these heating areas A, B, and C exert a certain temperature interference with each other. Such a furnace 10 is equipped with a control device shown in FIG. That is, burners 22, 24, 26
A gas pipe 28 is connected to each via control valves 30, 32, and 34, and an air pipe 36 is connected to the
are connected via air control valves 38, 40, and 42, respectively. Orifices 44 and 46, which are flow rate sensors, are installed in the base pipes of the gas pipe 28 and the air pipe 36, and the orifice 44 sends a gas flow signal GF representing the total flow rate of the fuel gas to the gas flow rate indicator 4.
8 and is also supplied to a flow rate regulator 52 via a multiplier 50. The multiplier 50 has O ₂ installed in the setting device 54 or the flue of the furnace 10.
A correction signal SA from the meter 56 is supplied,
The multiplier 50 multiplies the gas flow rate signal GF by the correction signal SA and supplies the result to the flow rate controller 52 . Also, the air flow signal AF is sent from the orifice 46 to the flow controller 5.
The flow controller 52 determines the air flow rate relative to the gas flow rate so as to obtain a predetermined air-fuel ratio, and sends a flow rate command signal CF representing the air flow rate through a corrector 58. Multiplier 6
0,62,64. On the other hand, from the thermocouples 16, 18, 20, temperature signals T1, T2, T3 representing the temperatures of the first heating zone A, the second heating zone B, and the third heating zone C are sent to a temperature controller 66 as a regulating means. , 8, 70, the voltage/current converter 7
2, 74, and 76, respectively. Each of the temperature controllers 66, 68, and 70 has a target temperature set in advance, and the deviation between the target temperature and the actual temperature of each heating area A, B, and C is calculated, and the temperature is calculated based on the deviation. Control signals mT1, mT2, and mT3 are outputted from the temperature controllers 66, 68, and 70 so that the deviation becomes zero. Here, the target temperatures set for each of the temperature controllers 66, 68, and 70 are generally a common temperature or different temperatures close to the common temperature in consideration of the characteristics of each heating area A, B, and C. These control signals mT1, mT2, mT3 are supplied to calculation units 78, 80, 82 as cross calculation means provided corresponding to each heating area A, B, C, respectively. Contacts 84 of the sampling device are inserted in series on the input and output sides of the temperature controllers 68 and 70, respectively, and are periodically closed for about 1 second at predetermined time intervals (about several tens of seconds). control signals mT2, from temperature controllers 68 and 70,
mT3 is periodically output to hold circuits 85, 85. Hold circuit 85, 8
5, the control signals mT2, mT3 are held for a predetermined time interval, and when new control signals mT2, mT3 are supplied, the control signals held in the hold circuits 85, 85 are held. It is now updated to new control signals mT2 and mT3.
That is, the contact 84 of the sampling device and the hold circuits 85, 85 form the updating means. Arithmetic units 78, 80, 82 each control signal
Based on mT1, mT2, mT3 and the degree of temperature interference between heating zones A, B, and C, operation signals m1, m2, and m3 representing operation amounts corresponding to each heating zone are sent to limiters 86, 88, and 90, respectively. via the characteristic converter 92,
94, 96 and the aforementioned multipliers 60, 62, 64, respectively. In addition, Limita 86, 88, 90
is for cutting fuel at a flow rate below a certain level in order to avoid unstable combustion in the burners 22, 24, and 26. Here, the temperature of each heating zone A, B, C of the furnace 10 is
T1, T2, and T3, and in order to control the temperature of each heating area A, B, and C, the operation signal to be supplied to the control valve, which is an operating device belonging to each heating area, is m1,
Assuming m2 and m3, the interference linear heating model equations (1), (2), and (3) as shown in the following equations are obtained. T1=m1+bm2+cm3 --(1) T2=m2+am1+c'm3 --(2) T3=m3+a'm1+b'm2 --(3) However, a, a', b, b', c, c' in the above equation are 1 greater than zero indicating the degree of interference between heating areas A, B, and C
It is a numerical value smaller than , and is determined experimentally for each heating model. Based on the heating model equations (1), (2), and (3) above, control signals mT1, mT2, mT3 and operation signal m1,
The non-interference control equation showing the relationship between m2 and m3 is derived as follows. m1=A1・mT1+B1・mT2+C1・mT3 --(4) m2=A2・mT1+B2・mT2+C2・mT3 --(5) m3=A3・mT1+B3・mT2+C3・mT3 --(6) However, [A1=1− b′c′/K, B1=b′c−b/K,
C1=bc'-c/K A2=a'c'-a/K, B2=1-a'c/K, C2
=ac-c'/K A3=ab'-a'/K, B3=a, b-b'/K,
C3=1−ab/K ∵K=a′bc′+ab′c+1−ab−a′c−b
′c′]. The arithmetic units 78, 80, and 82 respectively generate the operation signals m1,
It is configured to calculate m2 and m3. The characteristic converters 92, 94, 96 are configured to establish a linear relationship between the operation signals m1, m2, m3 and the gas flow rate based on the relationship between the valve opening degrees of the gas control valves 30, 32, 34 and the flow rate. operation signals m1, m2, m3
, respectively. Characteristic converter 92,9
The signals output from the gas control valves 4 and 96 are passed through current/pneumatic converters 98, 100, and 102 to the gas control valves 3 and 3.
0, 32, and 34, respectively. The multipliers 60, 62, 64 are connected to the flow rate controller 5.
The flow rate command signal CF output from 2 is multiplied by the operation signals m1, m2, m3, respectively, and the results are transmitted through characteristic converters 104, 106, 108 and current/pneumatic converters 110, 112, 114, respectively. Supplied to air control valves 38, 40, 42. That is, in each heating area A, B, C, gas control valves 30, 32, 3
Air at a fixed ratio to the fuel flowed by 4 is flown by the air control valves 38, 40, and 42, and the flow rate command signal CF is the flow rate of air to be flowed relative to the fuel gas flow rate. Ratio (air fuel ratio)
It represents. Note that the characteristic converter 104,1
06, 108 are the aforementioned characteristic converters 92, 94, 9
6, and the output signals from the multipliers 60, 62, 64 and the air flow rate have a linear relationship. In the control device configured as described above, the operation signals m1, m2, m3 used for temperature control of each heating area A, B, C are not only control signals for the heating area but also other signals. Heating area control signal and heating area A,
Since it is determined from the degree of temperature interference between B and C, for example, the operation signal m1 for heating area A is the control signal mT1 for controlling the temperature of heating area A.
as well as control signals for other heating zones B and C.
Coefficients derived from the degree of temperature interference between mT2, mT3 and the heating regions (A1 to A3, B1 to B3 in sections (4), (5), and (6),
C1 to C3), extremely suitable temperature control characteristics can be obtained without providing partition walls between heating zones A, B, and C. That is,
Rather than lowering the degree of mutual interference between heating zones A, B, and C by providing partition walls, the existence of mutual interference is taken into account in advance, and control signals for other heating zones are used to control the heating zone. It controls the temperature. Moreover, the control signal mT1 corresponding to heating area A is continuously changed, and heating areas B and C
Since the corresponding control signals mT2 and mT3 are held for a predetermined period of time and periodically updated, the temperature control system is stabilized with a simple configuration, and more desirable and highly accurate temperature control characteristics can be obtained. It is. According to the inventor's experiments, the results shown in Table 1 were obtained. That is, as shown in FIG.
The common target temperature at time 0 seconds is 50%,

[Table] Each heating area A shown by the broken line, solid line, and dashed-dotted line when the target temperature of the temperature controller 66 in one of the heating areas is set to 70% at a time of 1000 seconds and disturbance is applied. , B, C, the predetermined degree of interference is set to 0.3 or 0.5, and each heating area A, B,
When the temperature of C is controlled independently (hereinafter referred to as single), and in the control system shown in Figure 2, the manipulated variable is calculated using the non-interfering control equations (4), (5), and (6) described above. When temperature control is determined and temperature control is performed (hereinafter referred to as cross), the degree of interference is observed by simulation and the controllability at predetermined times (after 1000 seconds and after 2000 seconds) is judged by the temperature amplitude.
If it is 0.3, even when the control variables mT2 and mT3 are continuously changed without opening or closing the contact 84,
As shown in the two examples at the top of Table 1, the cross case was more stable than the single case. Furthermore, even when the sampling device is activated, as shown in Figure 4, when the update cycle changes from 15 seconds to 30 seconds, the single case becomes significantly unstable, while the cross case becomes completely unstable. It is stable. Also, if the degree of interference is set to 0.5, the fifth
As shown in the figure, the cross case is much more stable than the single case even if the update period changes. Incidentally, the degree of interference in an actual furnace generally does not exceed 0.5 at most. Also,
Although the vertical axis in FIG. 3 is expressed in %, it can be replaced with an appropriate temperature range. Although one embodiment of the present invention has been described above,
The invention also applies to other aspects. For example, in the above-mentioned embodiment, the heating area was divided in the width direction within the heating furnace 10;
It may be divided in the direction of movement of the object to be heated 12. Moreover, it goes without saying that the object to be heated 12 does not have to be integral over each heating area, and may be partially divided. A heating area A formed in the heating furnace 10,
B and C had three zones, but the number of zones was changed to two or four or more as appropriate. In such a case, there is no problem even if there are two or more heating regions in which control signals are continuously output from the temperature controller to the computing unit. Although a burner was used as the heating device in the embodiments described above, other heating means such as a heater may be used. It goes without saying that the adjustment means, cross operation means, and update means in the above-described embodiments can be constructed by a so-called microcomputer equipped with a signal processing program that performs the functions of each of these means. The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a heating furnace equipped with an embodiment of the present invention. FIG. 2 is a diagram showing the temperature control system provided in FIG. 1. FIG. 3 is a diagram showing an example of the transient response characteristics of the temperature control system shown in FIG. 2. FIGS. 4 and 5 are diagrams showing the relationship between the temperature amplitude after a predetermined time and the sampling period in the transient response, comparing the single case and the cross case. In FIG. 4, the degree of interference is 0.3. , and FIG. 5 shows a state where the degree of interference is 0.5. 10... Furnace, 12... Heated object, 16, 18,
20...Thermocouple (temperature sensor), 22, 24, 2
6... Burner (heating device), 66, 68, 70...
...Temperature controller (adjustment means), 78, 80, 82...
...Arithmetic unit (cross calculation means), {85...hold circuit, 84...contact} (update means).

Claims (1)

[Scope of Claims] 1. A temperature control device for controlling an object to be heated in the heating zones to a uniform temperature in a furnace having a plurality of heating zones that are adjacent to each other and have temperature interference, comprising: a plurality of temperature sensors that are respectively provided in the heating areas and output temperature signals representing the temperature of the heating areas; a plurality of heating devices that are respectively provided in the plurality of heating areas that heat the heating areas; and a predetermined target. adjusting means for comparing the temperature with the temperature of each heating area represented by the temperature signal, calculating a deviation therebetween, and outputting a control signal corresponding to each heating area so that the deviation becomes zero; , cross calculation means for calculating respective operation signals representing the operation amount corresponding to the heating area based on the respective control signals and the degree of temperature interference between the heating areas, the operation signal being applied to the heating device. 1. A temperature control device for a furnace having a plurality of heating zones, comprising: an arithmetic and control device that heats each of the heating zones. 2. In a furnace having a plurality of heating zones that are adjacent to each other and have temperature interference, a temperature control device that heats the object to be heated in the heating zone to a uniform temperature, which is provided in each of the plurality of heating zones, and a plurality of temperature sensors that output temperature signals representing the temperature of the heating regions; a plurality of heating devices that are respectively provided in the plurality of heating regions and heat the heating regions; and a predetermined target temperature and the temperature signal. an adjusting means for comparing the temperatures of the respective heating zones and calculating a deviation thereof, and outputting a control signal corresponding to each of the heating zones so that the deviation becomes zero; an updating means for holding a control signal corresponding to a heating area other than a predetermined heating area for a predetermined period of time and periodically updating it after the said period; a control signal updated by the updating means; cross calculation means for calculating a control signal corresponding to the predetermined heating area and an operation signal representing an operation amount corresponding to each heating area based on the degree of temperature interference between the heating areas; A temperature control device for a furnace equipped with a plurality of heating zones, characterized in that the heating device includes an arithmetic control device that causes the heating device to heat each of the heating zones according to the operation signal.