JPH0465743B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a device for measuring the level of molten metal in a mold in a vacuum melting furnace.

[Prior art and its problems] In equipment that performs continuous casting, it is necessary to automatically detect the level of molten metal poured into the mold. The molten metal level is measured using the brightness and darkness of the molten metal. The principle is that the mold is scanned using an optical sensor installed at a predetermined position that distinguishes between brightness and darkness, and the level of the molten metal is indirectly detected based on the scanning time of the bright areas of the molten metal. Detection of the molten metal level is also necessary in continuous casting equipment using a vacuum melting furnace, and in this case, the sensor is installed outside the vacuum melting furnace, so detection is carried out through a peephole provided in the vacuum melting furnace. However, in order to prevent metal vapor from adhering to the glass of this peephole, a disc with a slit is rotated inside the peephole so that it faces the glass of the peephole. Therefore, in the above measurement method, when the non-slit portion faces the sensor, the path is optically blocked by the disc, making it impossible to measure the molten metal level. For this purpose, it is necessary to synchronize the scanning and the rotation of the slit, which has the disadvantage of complicating the measuring device.

[Object of the Invention] This invention was made to eliminate the above-mentioned problems, and an object thereof is to provide a level measuring device that can be used in a conventional vacuum furnace.

[Structure of the Invention] This invention uses a viewing window provided in the vacuum melting furnace and a rotary plate having a slit provided inside the viewing window to measure the molten metal level in a mold provided in the vacuum melting furnace. A sensor that has a plurality of light receiving elements arranged in a straight line and detects bright and dark areas between the molten metal part on the upper surface of the mold inside the furnace and the mold part by scanning each light receiving element; minimum value storage means for storing a minimum value t _a at each detection time point when changing from a dark state to a bright state in each of the plurality of scans by the sensor; maximum value storage means for storing the maximum value t _b within the bright state scanning time t _b − obtained from the time points t a and t _b stored by the storage means _;
The method is characterized by comprising a calculation means for outputting t _a as a signal indicating the molten metal level.

[Embodiment] FIG. 1 shows an embodiment according to the present invention.

1 is a vacuum melting furnace; 2 is this vacuum melting furnace 1
It is a mold that is placed inside. 1a is vacuum melting furnace 1
3 is a rotating disc installed to prevent metal vapor from adhering to the glass of the viewing window 1a. A slit 3a is provided which is long and symmetrical about the center. The disc 3 is located almost parallel to the glass surface of the viewing window 1a, and is provided so that the upper half of the disc 3 faces the viewing window 1a.By rotating the disc 3, two slits are formed. 3a alternates with peephole 1a
The light image of the molten metal and mold passes through this slit 3a.
It can be seen intermittently through the viewing window 1a. 4 is a motor that rotates the disc 3. Reference numeral 5 denotes a linear sensor for light detection having a scanning function, which outputs a voltage representing the amount of light received by each light-receiving element by arranging a large number of light-receiving elements in a straight line. This linear sensor 5 detects the brightness and darkness of the molten metal in the mold 2.
is projected as an image onto the sensor array 5b by the lens 5a. The bright and dark areas are detected by scanning, and the linear sensor 5 outputs "H" and "L" signals corresponding to the brightness and darkness. This output signal is input to the minimum value storage circuit 6 and the maximum value storage circuit 7. The minimum value storage circuit 6 stores the minimum value at the time when the signal sent from the linear sensor 5 changes from L to H every time a scan is performed, and the maximum value storage circuit 7 similarly stores the minimum value at the time when the signal sent from the linear sensor 5 changes from L to H. The maximum value at the time of the change is stored. 8 is an arithmetic circuit which subtracts the minimum value from the maximum value stored in the storage circuit and outputs the result as a level signal.

Next, the functions of the device configured as described above will be explained.

FIG. 2 is an enlarged view of the rotating disk 3, and the scanning direction of the linear sensor 5 is such that when the slit 3a of this disk 3 is in a vertically oriented position,
The direction is set at a certain angle α with respect to the direction a to prevent optical cutting by the slit 3a during scanning.

In the above-described projection through the slit 3a, not all of the mold 2 is projected, but only a portion of the mold 2 is projected, and the projected location differs depending on the position of the slit 3a during scanning. come. Therefore, in this embodiment, the slit 3a
The linear sensor is scanned multiple times within a predetermined time period t _x that is an integral multiple of the rotation period of , and the output signals obtained from each scan are combined and restored.

FIG. 3 shows an example in which scanning is performed three times within the predetermined time t _x , and the detection signal changes from dark to bright at the time point t ₁ , t ₃ , and t ₅ , which is the minimum. Time t ₅ is stored in the minimum value storage circuit 6, and time t 4, which is the maximum of the times t ₂ , t _{4 and} t ₆ when the light changes from bright to dark, is stored in the maximum value storage circuit 7. Therefore, after the predetermined time _tx , the arithmetic circuit 8 calculates _t4 - _t5 and outputs the result. Further, at this time, the numerical values stored in the minimum value storage circuit 6 and maximum value storage circuit 7 are cleared by the reset signal. From the time length of t ₄ - t ₅ (corresponding to t _a - t _b above), (H ₁ - _{H 2} ) shown in Figure 1 can be estimated, and this
Since H ₂ is predetermined based on the relative positional relationship between the mold 2 and the linear sensor 5, the molten metal level H can be determined by adding the H ₂ value to the above (H ₁ - _{H 2} ) value. .

Figure 4 A and B show that n scans are performed during the above predetermined time t _x .
This shows a signal in which the minimum value and maximum value of the output signal are stored by the output signal of the linear sensor 5 when the rotation is repeated, and the minimum value storage circuit 6 and maximum value storage circuit 7. The third scan is when nothing is detected due to the position of the slit 3a, and the linear sensor 5 during the fourth and fifth scans.
The intermittent “H” signals in the output waveform of the molten metal are detected as dark areas due to insoluble matter floating on the surface of the molten metal. However, according to the method described above, as shown in FIG. is ignored. In addition, since the molten metal level is detected by scanning multiple times, there is no need to synchronize the rotational speed of the disk 3 with the scanning, and the molten metal level can be detected by simply adding a linear sensor 5 etc. to a conventional vacuum melting furnace. can be detected. Incidentally, by using the above-described measuring device as a level measuring device for a melting furnace other than a vacuum melting furnace, and by providing a rotary plate having slits, it is possible to prevent dust from adhering to the lens portion of the sensor.

[Effects of the Invention] As detailed above, this invention performs multiple scans to detect the molten metal level, and combines the signals obtained from each scan to restore a single signal. Even if there is a rotating plate that intermittently interrupts the optical path, the molten metal level can be accurately measured.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is an enlarged plan view of the rotating disk in Fig. 1, and Figs. FIG. 4B is a waveform diagram in which the respective output signals in FIG. 4A are combined. 5...Linear sensor, 6...Minimum value storage circuit, 7...Maximum value storage circuit, 8...Arithmetic circuit.

Claims (1)

[Claims] 1. The level of molten metal in a mold provided in a vacuum melting furnace is controlled through a viewing window provided in the vacuum melting furnace and a rotary plate having a slit provided inside the viewing window. A measuring device comprising: a sensor having a plurality of linearly arranged light-receiving elements and detecting bright and dark areas between the molten metal part on the upper surface of the mold inside the furnace and the mold part by scanning each light-receiving element; and the sensor. a minimum value storage means for storing a minimum value t _a at each detection time point when changing from a dark state to a bright state in each of the plurality of scans; maximum value storage means for storing the maximum value t _b ; and a bright state scanning time t _b − obtained from the time points t _a and t _b stored by the storage means;
A level measuring device for continuous casting equipment using vacuum melting, characterized in that it is equipped with a calculation means for outputting t _a as a signal indicating the molten metal level.