JPH0558828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold level control device in a continuous casting machine.

[Conventional technology]

BACKGROUND ART Conventionally, there has been known a mold level control device as shown in FIG. 7, which maintains the level of molten metal in a mold at a target level in a continuous casting machine.

That is, FIG. 7 is an explanatory diagram of the configuration of a continuous casting machine equipped with a mold level control device, and the reference numeral 51 shown in the figure is a molten steel ladle.
A bottom plate 53 having a through hole having the same diameter as the molten steel outlet hole of the tundish 52 is fixed to the lower surface of the tundish 52 installed below. A seal plate 54 having a through hole with the same diameter as the molten steel outflow hole is provided below this plate 53 at a predetermined distance apart, and between both plates 53 and 54, the molten steel outflow hole of the tundish 52 is provided. A slide valve 55 is provided with a through hole having the same diameter as that of the slide valve 55. This slide valve 55 is for adjusting the amount of molten steel injected into the mold 56 from the tundish 52 to become the slab 57, and the level of the molten steel in the mold 56 is controlled by a mold level control device, which will be described later. The opening degree of the through hole is corrected and adjusted so as to maintain the target hot water level.

To explain the structure of the mold level control device, as shown in the figure, a hydraulic cylinder 61 is attached to an upper bracket 52a fixed to the side surface of the tundish 52, and a piston rod of this hydraulic cylinder 61 is attached to the upper bracket 52a fixed to the side surface. The tip of the link 61a is pin-connected to one end of a link 62 which is swingably supported by a lower bracket 52b fixed to the tundish 52 below the upper bracket 52a. Furthermore, this link 6
The other end of the valve 2 is connected to the slide valve 55 via a connecting rod 63. Also, 64
is a differential transformer for detecting the position (displacement) of the piston rod 61a of the hydraulic cylinder 61, and its main body is fixed to the hydraulic cylinder 61 etc. by a support member (not shown), and its rod-shaped core is moved together with the piston rod 61a. , a voltage signal is output depending on the position of the piston rod 61a.

Further, 65 is a level meter consisting of an eddy current type, an electrode tracking type, etc., which detects the level of the molten metal in the mold 56;
65a is a level meter amplifier; 66 is a target hot water level setting device for setting the target hot water level; 67
inputs the output of the level meter 65 via the amplifier 65a and the output of the target hot water level setting device 66, calculates the deviation of these using a PID calculation circuit, etc., and outputs a value according to the difference between the two outputs. This is a valve opening command section, and 68 is a cylinder control section composed of a normal directional control valve, a servo amplifier, etc., and is used to control the output and positioning of the valve opening command section 67. The output of the differential transformer 64 is input, and the operation of the hydraulic cylinder 61 is controlled to maintain the level of hot water in the mold 56 at the target level according to the output of the valve opening command section 67. It is.

Next, to explain the operation of the mold level control device configured as described above, an imbalance occurs between the amount of molten steel injected into the mold 56 via the slide valve 55 and the amount of slab 57 pulled out, and the level meter 6
When a deviation occurs between the output of 5 and the output of the target hot water level setting device 66, an output corresponding to the difference between the two outputs is given from the valve opening command section 67 to the cylinder control section 68. The cylinder control unit 68 operates the hydraulic cylinder 61 in response to this. For example, mold 5
When the hot water level in the hot water level in the hot water tank 6 is higher than the target hot water level level, the piston rod 61a of the hydraulic cylinder 61 is extended, and the slide valve 55 is slid through the link 62 and the connecting rod 63 to reduce its opening degree. The amount of molten steel injected into the mold 56 is adjusted to decrease.

[Problem to be solved by the invention]

However, although the above mold in-mold level control device is useful to some extent, it still has problems in the control accuracy of the level as described below.

In other words, since the hydraulic cylinder is actuated and the slide valve is slid through a connecting part such as a link or a connecting rod to adjust its opening, the opening is adjusted due to the play between the holes in this connecting part. There was a discrepancy between the amount of expansion and contraction of the piston rod of the hydraulic cylinder and the amount of sliding of the slide valve, making it impossible to accurately control the hot water level.

In particular, when changing the sliding direction of the slide valve, which is important for controlling the hot water level, or in other words, when changing the operating direction of the hydraulic cylinder, the looseness of this connection causes a delay in control, causing the hot water level to change. There was a problem in that the fluctuations became large and as a result, the quality of the slab deteriorated.

Note that the play value of this connecting part changes due to the high temperature atmosphere during casting compared to the value before starting casting, and slide valves, links, connecting rods, etc. are replaced with the tundish. Since the value is different each time it is exchanged,
It is of such a nature that it is difficult to know its value as a constant value in advance.

This invention was made in order to solve the above-mentioned problems, and it detects the value of play that exists between the slide valve and the piston rod of the hydraulic cylinder during the hot water level control operation, and adjusts the hydraulic pressure. The purpose of the present invention is to provide an in-mold molten metal level control device that can accurately control the molten metal level in the mold by operating the cylinder an extra amount corresponding to this backlash when changing its operating direction.

[Means to solve the problem]

In order to achieve the above object, the mold level control device according to the present invention includes a hydraulic cylinder that expands and contracts a piston rod to adjust the opening degree of a slide valve that adjusts the amount of molten steel injected into the mold from a tundish; A position detector detects the position of the piston rod, a level meter detects the level of hot water in the mold, and the deviation between the output of the level meter and the output of the target level setter is calculated, and the difference between the two outputs is calculated. and a valve opening command section that outputs a corresponding value, and the hydraulic cylinder is operated according to the output of the valve opening command section to maintain the hot water level in the mold at the target hot water level. , a mold level control device in a continuous casting machine, which calculates a rate of change in the level of molten metal in the mold based on the output of the level meter, and maintains a constant rate of change in the level of molten metal in the mold, and a piston rod of the hydraulic cylinder. a play detecting means for detecting the amount of movement of the piston rod when the piston rod is expanding and contracting as a value of play existing between the slide valve and the piston rod based on the output of the position detector; The direction in which the valve opening command section operates is determined based on the output of the valve opening command section, and the play value obtained by the play detection means is added to the output of the valve opening command section when changing the operating direction. The apparatus is characterized by comprising a backlash correction control means for adding.

[Effect]

The backlash measurement principle according to this invention will be explained based on FIG. 6 of the explanatory diagram.
As shown in Figure a, it varies due to the imbalance between the amount of molten steel injected into the mold and the amount of slab pulled out. Then, the amount of molten steel injected changes by correcting the opening degree of the slide valve, and the resulting change in the amount of unbalance appears as a change in the rate of change in the molten metal level (dL/dt). That is, when the opening degree of the slide valve is actually corrected by the operation of the hydraulic cylinder, the rate of change in the hot water level changes. Therefore, as shown in Figures 6b and 6c, the value of the play in the connection between the slide valve and the piston rod is determined when the rate of change in the hot water level is constant and the piston rod of the hydraulic cylinder expands and contracts. It can be determined as the amount of movement (ΔX _o ) of the piston rod during operation.

In the mold level control device according to the present invention, the play value is determined by the play detection means based on the outputs of the level meter and the position detector based on the play measurement principle described above. Then, the direction in which the hydraulic cylinder is operated is determined based on the output of the valve opening command section, and the above-mentioned backlash value is added to the output of the valve opening command section when changing the operating direction. Thereby, the opening degree of the slide valve can be reliably and precisely corrected by the expansion and contraction movement of the piston rod of the hydraulic cylinder.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of the configuration of a continuous casting machine equipped with a mold level control device showing an embodiment of the present invention, in which the continuous casting machine has the same configuration as that explained in FIG. 7. 1 is a molten steel ladle, 2 is a tundish, 3 is a bottom plate, 4 is a seal plate, 5 is a slide valve whose opening degree is adjusted by a mold level control device to be described later, and 6 is a slide valve. The mold, 7, is a slab.

As shown in the figure, the mold level control device has a hydraulic cylinder 8 mounted on an upper bracket 2a fixed to the side of the tundish 2.
is attached, and the tip of the piston rod 8a of this hydraulic cylinder 8 is attached to a pin at one end of a link 9 which is swingably supported by a lower bracket 2b fixed to the tundish 2 below the upper bracket 2a. connected. Further, the other end side of this link 9 is connected to the above-mentioned slide valve 5 via a connecting rod 10. Also,
Reference numeral 11 denotes a differential transformer for detecting the position (displacement) of the piston rod 8a of the hydraulic cylinder 8. Its main body is fixed to the hydraulic cylinder 8 etc. by a support member (not shown), and its rod-shaped core moves together with the piston rod 8a. and outputs a voltage signal depending on the position of the piston rod 8a.

Further, 12 is a level meter for detecting the level of the hot water inside the mold 6, 12a is an amplifier for the level meter, 13 is a target level setting device for setting the target hot water level, and 14 is a level meter that detects the level via the amplifier 12a. Total 12
and the output of the target hot water level setting device 13 as inputs, calculate the deviation of these using a PID calculation circuit, etc., and output a value according to the difference between the two outputs; 15 is a level control unit; A play detection method that uses the total 12 outputs and the output of the differential transformer 11 as input, and detects the value of play that exists between the slide valve 5 and the piston rod 8a due to the link 9, the connecting rod 10, etc. according to the procedure described later. The means 16 is a play correction control means which receives the output of the valve opening command unit 14 and the play value signal from the play detection means 15 and outputs a valve opening correction signal according to the procedure described later; is a cylinder control section consisting of a normal directional control valve, a servo amplifier, etc., and is connected to the valve opening correction signal and the differential transformer 11.
The output of the hydraulic cylinder 8 is inputted to control the operation of the hydraulic cylinder 8 according to the valve opening correction signal.

The backlash detection means 15 and backlash correction control means 16 are constructed by a programmed microcomputer. That is, backlash detection means 1
5, as shown in FIG. 2, a CPU, a memory in which programs and predetermined control data are stored,
The output of the level meter 12 and the output of the differential transformer 11 are respectively inputted via an A/D converter, and the obtained play value signal is sent to the play correction control means. It is now being given to the 16th. In addition, the backlash correction control means 16 includes a CPU, memory,
and an input/output interface circuit, into which the output of the valve opening command unit 14 is input via the A/D converter, and the valve opening correction signal is input to the cylinder control unit 17 via the D/A converter. It is beginning to be given to

Next, the operation of the hot water level control device having the above structure will be explained below with reference to the drawings.

First, according to the flowchart shown in Figure 4,
An example of a method for detecting the play value using the play detection means 15 will be explained (see FIG. 6). In the explanation of the flowchart, N1, N2, . . . indicate processing procedure (step) numbers.

First, when control is started, the hot water level obtained by the level meter 12 and the position of the piston rod 8a obtained by the differential transformer 11 are read at predetermined sampling intervals Δt. and,
The rate of change in the hot water level calculated based on the current hot water level L _o and the previous hot water level L _o-1 [=(L _o −
It is determined whether or not L _o-1 )/Δt] is constant (step N1). If the rate of change in the hot water level is not constant, this step N1 is repeated. If the rate of change in the hot water level is constant, it is determined whether the piston rod 8a has moved from its previous and current positions (step N2). Here, if the piston rod 8a has not moved, the process returns to step N1, and if the piston rod 8a has moved, the movement start position _Xs of the piston rod 8a is stored (step N3). Next, based on the newly read hot water level obtained by the level meter 12, it is determined whether or not the rate of change in the hot water level is constant (step N4). In other words, when the opening degree of the slide valve 5 is not corrected due to backlash even though the piston rod 8a has been moved, the newly read piston rod 8a
The moving position _XE is memorized (step N5). This step N5 is repeated for each read hot water level and position of the piston rod 8a until the rate of change of the hot water level changes, thereby sequentially updating the movement position _XE of the piston rod 8a.

If it is detected in step N4 that the rate of change in the hot water level has changed, that is, if it is confirmed that the backlash has been resolved and the opening degree of the slide valve 5 has been corrected, the above-mentioned piston rod 8
The current backlash value ΔX _o is determined from the difference between the movement position X _E of a and its movement start position X _s (step N6), and the process returns to step N1. Then, the average value of the predetermined number of previously determined backlash values and the current backlash value ΔX _o is determined, and this is provided as the playback average value K to the backlash correction control means 16 (step N6). Note that this play average value K is provided to the play correction control means 16 every time it is updated. In addition, by calculating this average value, variations in the backlash value ΔX _o due to thermal expansion of the slide valve 5, link 9, etc., and detection error of the change point of the rate of change of the hot water level can be rounded off. The accuracy can be increased.

Next, according to the flowchart shown in Figure 5,
An example of a correction control method by the backlash correction control means 16 will be described. In addition, while explaining the flowchart,
S1, S2...indicate the number of the processing procedure (step).

First, when control is started, the output MV _o from the valve opening command section 14 is output at predetermined sampling intervals.
(having a positive or negative sign) is read. and,
From the sign of the product of the output MV _o read this time and the output MV _o-1 read last time, the hydraulic cylinder 8
Determine the direction in which to operate this time (step S1),
When operating the hydraulic cylinder 8 in the same direction as last time, the current output MV _{o is directly output as a valve opening correction signal to the cylinder control unit 17 via the D/A converter (step S2), and then the current output MV o} is outputted as a valve opening correction signal to the cylinder control section 17 (step S2), and then Return to

On the other hand, in step S1, the hydraulic cylinder 8
If it is determined that the valve should be operated in the opposite direction from the previous time, as shown in the figure, the latest play given by the play detection means 15 is applied to the current output MV _o of the valve opening command section 14. Add the average value K,
The output MV _oa corrected by the backlash average value K, that is, the current output MV _o of the valve opening command unit 14, is increased by an amount corresponding to the backlash value.
Alternatively, the output MV _oa for reverse operation is output as a valve opening correction signal to the cylinder control section 17 via the D/A converter (step S3). Note that in the first correction control, a predetermined initial value input in advance as the average backlash value K may be used.

As a result of the above, the value of the backlash that exists between the slide valve and the piston rod of the hydraulic cylinder that drives it repeats and sequentially increases during the level control.
It is automatically detected, and when changing the operating direction of the hydraulic cylinder, the hydraulic cylinder is detected and operated extra to compensate for the backlash, so the hot water level is controlled with extreme precision to maintain the target hot water level. .

In the above embodiment, the differential transformer 11 is used to detect the position (displacement) of the piston rod 8a of the hydraulic cylinder 8, but a potentiometer or the like may be used as the position detector.

In addition, the mold level control device according to the present invention has a configuration in which a hydraulic cylinder is disposed on the bottom side of the tundish, or the mold level level is adjusted by operating a hydraulic cylinder and controlling the opening of a stopper nozzle. Of course, it is also applicable to those with a configuration that does.

〔Effect of the invention〕

As explained above, the mold level control device for a continuous casting machine according to the present invention sequentially adjusts the value of play existing between the slide valve and the piston rod of the hydraulic cylinder that drives the slide valve during the level control. In other words, there is a backlash detection means that automatically detects the backlash online based on the outputs of the level meter and the position detector, and when the operating direction of the hydraulic cylinder is changed, the backlash detected by this backlash detection means. It is equipped with backlash correction control means that operates an extra amount corresponding to the backlash value.

Therefore, according to the hot water level control device according to the present invention, it is possible to replace the slide valve or the connecting part connecting it to the piston rod, or to change the backlash value due to changes in ambient temperature, friction, etc. during control. Even if there is a problem, the molten metal level during casting can be maintained at the target molten metal level very accurately and quickly, and this can contribute to improving the quality of the slab.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of a continuous casting machine equipped with a mold level control device showing an embodiment of the present invention, Fig. 2 is a configuration diagram of a microcomputer as a backlash detection means, and Fig. 3 is a backlash correction diagram. FIG. 4 is a flowchart showing an example of a backlash value detection means by backlash detection means; FIG. 5 is a flowchart showing an example of a control procedure by backlash correction control means; FIG. 6 is an explanatory diagram of the backlash measurement principle according to the present invention, and FIG. 7 is an explanatory diagram of the configuration of a continuous casting machine equipped with a conventional mold level control device. (Explanation of symbols), 1... Molten steel ladle, 2... Tundish, 2a... Upper bracket, 2b... Lower bracket, 3... Bottom plate, 4... Seal plate, 5... Slide valve, 6... template,
7... Slab, 8... Hydraulic cylinder, 8a... Piston rod, 9... Link, 10... Connection rod, 11... Differential transformer, 12... Level meter,
12a...Level meter amplifier, 13...Target level setting device, 14...Valve opening command section, 15
...Backlash detection means, 16...Backlash correction control means,
17... Cylinder control section.

Claims (1)

[Scope of Claims] 1. A hydraulic cylinder that extends and contracts a piston rod to adjust the opening degree of a slide valve that adjusts the amount of molten steel injected into the mold from a tundish; a position detector that detects the position of the piston rod; a level meter that detects the hot water level; and a valve opening command section that calculates the deviation between the output of the level meter and the output of the target hot water level setting device, and outputs a value according to the difference between the two outputs. A mold level control device for a continuous casting machine, wherein the hydraulic cylinder is operated according to the output of the valve opening command section to maintain the mold level at a target level. Calculate the rate of change in the level of hot water in the mold based on the output of the level meter, and move the piston rod of the hydraulic cylinder when the rate of change in the level of hot water is constant and the piston rod of the hydraulic cylinder is expanding and contracting. play detecting means for detecting the amount of play existing between the slide valve and the piston rod based on the output of the position detector; and the direction in which the hydraulic cylinder is operated based on the output of the valve opening command section. and a backlash correction control means for determining based on the amount of play and adding the backlash value obtained by the backlash detection means to the output of the valve opening command section when changing the operating direction. Features: A mold level control device in a continuous casting machine.