JPH038963Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a root face measuring device necessary for end face shape inspection in a steel pipe manufacturing process.

[Conventional technology]

The end face of a steel pipe manufactured through the steel pipe manufacturing process after chamfering consists of a sloped part and a flat part, as shown in Figure 3. This flat part is called the root face, and its measurement is an important part of end face shape inspection. It is an item. The outer surface of the sloped surface serves as a welding groove between the pipes, and the inner surface serves to prevent an increase in fluid resistance when a step shift occurs between the welded pipes.

To measure this root face using an optical method, as shown in the figure, a floodlight and an image sensor camera such as a CCD are used to measure the root face (diameter) at each rotational position while rotating the steel pipe 10. The camera views the end face of the pipe as shown in Figure 3 and scans in the radial direction. Therefore, the video output has a waveform as shown in FIG. 4(3). Conventionally, this has been processed using a circuit as shown in FIG. 2 to measure the root phase.

In Fig. 2, 12 is the camera, 14 is a comparator, 1
6 is a reference value setter, 18 is an AND gate, 20 is a counter, 22 is a latch memory, 24 is a display and/or recorder, 26 is a clock generator, 28 is a frequency divider, and 30 and 32 are one-shot circuits. If the number of image sensors arranged in one row of the camera 12 is n, then by giving n clocks, as shown in Fig. 4(3),
One line of video output like this can be obtained, and the steel pipe 10
By performing such processing at each rotational position, one line of video output at each rotational position can be obtained. The frequency divider 28 divides the frequency of the clock output by the clock generator 26 to 1/n, and outputs the one-shot circuit 3.
0 produces an output of a predetermined width at the rise of the output of the frequency divider 28, and inputs this to the camera 12 as a start pulse SP. The camera 12
Upon receiving SP, it starts outputting the video signal.
The start pulse SP is also a one-shot circuit 32.
The counter 20 reset pulse RP is entered into the counter 20, and the counter 20 reset pulse RP is entered into the latch memory 22, and the contents of the counter 20 immediately before the reset is taken into the latch memory.

When the camera 12 receives the start pulse SP and starts outputting a video signal, the comparator 14 compares this with a reference value from the setting device 16, and when the video signal is equal to or higher than the reference value, the comparator 14 outputs an H (high) signal.
A level output is generated and the eye gate 18 is opened. Therefore, the clock from the clock generator 26 passes through the AND gate 18 and enters the counter 20, and since this counter has been cleared to zero by the reset pulse RP generated following the start pulse SP, the clock starts counting from zero. do. When the video signal falls below the reference value, the AND gate 18 closes.
Clock input to the counter stops. Therefore, the counter 20 remains in the counting state up to that point, and sends the counted value to the latch memory 22 when the next start pulse SP is generated. The contents of this memory 22 are displayed/recorded on a display/recorder 24.

[Problem that the invention attempts to solve]

With this conventional circuit, the root phase measurement accuracy is not very high. That is, the periphery of the end face of the steel pipe is sloped, and as a result of this, the video signal output from the camera 12 has slow rising and falling parts, as shown in FIG. 4. Therefore, the counter count value varies greatly depending on how the reference value is set, making it difficult to determine the exact route phase.

The boundary between the root face and the slope portion forms a bend, and the amplitude of the video signal changes greatly. The present invention focuses on this point and attempts to shape the waveform of the video signal to emphasize the boundary portion, thereby enabling accurate root phase measurement.

[Means for solving problems]

The present invention consists of a camera that images the end face of a steel pipe, a comparator that compares one line of video signal output by the camera with a reference value, and generates a gate open output when the video signal is greater than or equal to the reference value; A delay-type integration circuit for smoothing a video signal outputted by the camera in a root phase measurement device for an ERW tube, which includes a counter that counts clocks input through the gate and generates a root phase measurement output; A first differentiating circuit that differentiates the output of the integrating circuit, a second differentiating circuit that differentiates the output of the first differentiating circuit, and determining the difference between the output of the delay type integrating circuit and the output of the second differentiating circuit. The present invention is characterized in that it is further provided with a subtraction circuit which inputs .

〔Example〕

FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals. As is clear from comparing the two, in the present invention, a delay integration circuit (low-pass filter) 34, a first differentiation circuit 36, a second differentiation circuit 38, and a subtracter 40 are inserted into the circuit for the video signal output from the camera 12. This point differs from conventional circuits.

To explain the operation of the circuit shown in FIG. 1 with reference to the waveform diagram shown in FIG.
The individual image sensors are
A charge corresponding to the amount of light incident on the element is generated, and the charge is transferred in series, resulting in a potential change at the output end, and the potential change becomes a video signal, so the video signal is processed in multiple stages as shown in Figure 4.3. Become wavy. The delay type integration circuit 34 smooths this as shown in FIG. 4 so that the subsequent differential processing is not hindered. The first differentiating circuit 36 differentiates this and the result is shown in FIG.
The second differentiating circuit 38 further differentiates this to produce an output as shown in FIG. 4. The subtracter 40 takes the difference between the output of the delay type integrating circuit 34 and the output of the second differentiating circuit 38, and produces the output shown in FIG. 4. When compared with FIG. 4, FIG. 4 clearly shows sharp rises and falls, and the rising/falling portions correspond to the boundaries. This is compared with an appropriate reference value in the comparator 14, and as shown in FIG.
get the output of If the AND gate 18 is opened by the output of the comparator shown in FIG. 4 and the counter 20 counts the number of clocks during this period, the root phase can be accurately measured. Since the rising and falling edges are sharp (standing upright), no large measurement error will occur even if the reference value is slightly inappropriate. FIG. 4 is a diagram illustrating the state in which clocks are counted by the counter 20.

[Effects of the Invention] As explained above, according to the present invention, the root face and the slope portion can be easily and accurately separated, and highly accurate root face measurement becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional example, Fig. 3 is a diagram explaining the route phase measurement procedure, and Fig. 4 is a waveform diagram for explaining the operation. . In the drawing, 10 is a steel pipe, 12 is a camera, 14 is a comparator, 20 is a counter, 34 is a delay type integration circuit, 3
6 and 38 are first and second differentiating circuits, and 40 is a comparator.

Claims (1)

[Claim for Utility Model Registration] Comparing a camera that images the end face of a steel pipe and one line of video signal outputted by the camera with a reference value,
Root phase measurement of an ERW pipe, comprising a comparator that generates a gate open output when the video signal is above a reference value, and a counter that counts clocks input through the opened gate and generates a root phase measurement output. The apparatus includes: a delay-type integrating circuit that smooths a video signal output by the camera; a first differentiating circuit that differentiates the output of the integrating circuit; and a second differentiating circuit that differentiates the output of the first differentiating circuit; A steel pipe root phase measuring device, comprising: a subtraction circuit that calculates the difference between the output of the delay type integrating circuit and the output of the second differentiating circuit and inputs the difference to the comparator.