JPH074559Y2 - Surface defect inspection device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a surface defect inspection apparatus, which is characterized by the difference in the infrared radiation amount between the sound part and the defect part of the surface of the material to be inspected. An apparatus for surely discriminating a sound part and a defective part.

It is a well-known fact that when a surface defect such as a crack exists in the material to be inspected, the surface defect portion has a different temperature rising rate as compared with a sound portion when the surface of the material to be inspected is heated. Surface defect inspection using the fact that when heated by an induction heating device, surface defects such as cracks show a larger temperature rise than healthy parts due to the edge effect and the infrared radiation amount increases in proportion to the temperature rise. The device has been put to practical use. On the other hand, surface defects such as a part of the material to be inspected, such as a hair drop, lifted up from the base material have a large surface area and large heat radiation, so natural cooling is fast after the heating is stopped, so the temperature is lower than that in a sound area. It is also possible to detect surface defects by utilizing the difference in infrared radiation amount due to this temperature difference.

[Conventional technology]

FIG. 2 is a diagram showing a conventional surface defect inspection apparatus of this type. In FIG. 2, (1) is an inspected material, (2) is an inspected material conveying device, (3) is a heating device, (4) is an infrared detector, (5) is a scanning device, (6) is an amplifier, (7) is a signal separation circuit, (8) is a synchronization circuit, (9) is a delay circuit, (1
0) is a subtraction circuit, (11) is a judgment circuit, and (12) is an indicator.

In the conventional surface defect inspection apparatus of this type, the inspected material (1) conveyed in a predetermined direction by the inspected material conveying apparatus (2)
The surface of is heated by a heating device (3) at a predetermined position, and the infrared light emitted from the unheated region before heating and the infrared light emitted from the heated region after heating are both transferred to the unheated region by the scanning device (5). The heating area is detected by an infrared detector (4) which is scanned in a predetermined sequence. The detected infrared signal is usually amplified by the amplifier (6) and then unheated by the signal separation circuit (7) based on the synchronization signal generated by the synchronization circuit (8) in synchronization with the scanning of the scanning device (5). The infrared signal of the area and the infrared signal of the heating area are separated. The infrared signal in the unheated area is delayed by a predetermined amount by the delay circuit (9), and the infrared signal in the heated area and the delayed infrared signal in the unheated area are subtracted by the subtraction circuit (10). As the delay amount of the delay circuit, the time during which the material to be inspected is conveyed from the unheated area to the heated area is usually used. Next, when the subtracted value exceeds a predetermined judgment value, the judgment circuit (11) judges that there is a defect, and the display (12) displays the presence or absence of the defect. In this type of conventional surface defect inspection apparatus, a division circuit may be used instead of the subtraction circuit (10), and improvements such as logarithmic conversion of an infrared signal as preprocessing for subtraction or division are also added. ing.

[Problems to be solved by the device]

The conventional surface defect inspection apparatus has the following problems.

In other words, there is a problem that some parts of the sound part have a large temperature rise due to heating or parts that cool quickly after heating, and these parts may be mistakenly regarded as defects. For example, when a rectangular column-shaped material to be inspected is heated by an induction heating device, each corner of the column exhibits a large temperature rise due to the edge effect, so even if the difference in the amount of infrared radiation increase due to the temperature rise is simply detected. It is not possible to distinguish between surface defects such as cracks and the corners of sound areas. This invention was made to solve the above problems.

[Means for Solving the Problems]

The surface defect inspection apparatus according to the present invention scans a plurality of heating areas for the purpose of detecting a difference in change in the infrared radiation amount on the surface of the material to be inspected caused by the lapse of time after heating, and the infrared radiation amount of each heating area is detected. Is provided with a plurality of delay circuits and a plurality of arithmetic circuits for detecting a difference in change from the infrared radiation amount in the unheated area.

[Action]

In this invention, since the calculated values of the infrared signals delayed by the delay circuit detect the difference in the infrared radiation amount on the surface of the material to be inspected caused by the lapse of time after heating, It is possible to discriminate between a sound portion and a defective portion based on the difference in the change in the infrared radiation amount on the surface of the material to be inspected over time.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention.
(8), (11) to (12) are exactly the same as the conventional device. (9) is a first delay circuit, (13) is a second delay circuit, (10) is a first subtraction circuit, and (14) is a second subtraction circuit.

The operation will be described. The surface of the material to be inspected (1) conveyed in a predetermined direction by the material to be inspected conveyance device (2) is heated by a heating device (3) at a predetermined position, and infrared rays and heating emitted from an unheated region before heating. The infrared rays radiated by the subsequent heating area are both detected by the infrared detector (4) which scans the unheated area and the heating area in a predetermined order by the scanning device (5).

At this time, the heating area is scanned in two different areas along the conveyance direction of the material to be inspected. In this embodiment, the first heating region is set to be a region immediately after heating, and the second heating region is set to be a region after a predetermined time, for example, about 5 seconds has elapsed after heating. The detected infrared signal is amplified by the amplifier (6) and then the signal separation circuit (7) generates an unheated area based on the synchronization signal generated by the synchronization circuit (8) in synchronization with the scanning of the scanning device (5). Of the first infrared signal, the second infrared signal of the first heating area, and the third infrared signal of the second heating area.

The first infrared signal in the unheated area is delayed by the first delay circuit (9), and the second infrared signal in the first heated area is delayed by the second delay circuit (13) by different predetermined amounts. The third infrared signal of the second heating region and the first infrared signal of the unheated region delayed by the first delay circuit (9) are subtracted by the first subtraction circuit (10). On the other hand, the third infrared signal of the second heating area and the second infrared signal of the first heating area delayed by the second delay circuit (13) are also subtracted by the second subtraction circuit (14). It As the delay amount of the delay circuit, the time during which the material to be inspected is conveyed from the unheated area to the first heated area and the second heated area is usually used. In this embodiment, it takes, for example, about 5 seconds before the material to be inspected is conveyed from the first heating area to the second heating area. Therefore, the delay amount of the first delay circuit is larger than the delay amount of the second delay circuit. It is set 5 seconds more.
For example, a surface defect such as a hair drop has a small heat capacity, and the heating time is short, but the cooling time is short, so that the temperature almost returns to that before heating, for example, after about 5 seconds, so the first subtraction circuit While the subtraction value output of (10) is large and the subtraction value output of the second subtraction circuit (14) is small,
The heat capacity of each corner portion of the prismatic inspection material is large and a temperature difference hardly occurs after a lapse of time of, for example, about 5 seconds. Therefore, the subtraction value output of the first subtraction circuit (10) and the second subtraction circuit ( Since there is no large difference in the subtraction value output of 14), the subtraction value output of the first subtraction circuit is a predetermined amount or more and the subtraction value output of the second subtraction circuit is the criterion as the judgment criterion of the judgment circuit (11). If the defect is present only when the amount is less than a certain amount, it becomes possible to discriminate between a surface defect such as a part of the inspected material floating up from the base material and a sound corner of the prismatic inspected material.

[Effect of device]

As described above, according to this invention, it is possible to detect a surface defect such as a hair drop without erroneously recognizing a sound corner portion of the inspection object as a defective portion. In the embodiment of the present invention, the case where the corner healthy part of the prismatic test material and the surface defect such as a heddle are discriminated when the test material having the prismatic shape is heated by the induction heating device has been described. It is not necessary to use an induction heating device as a device, and even if the defect to be detected is not a surface defect such as a baldness, it shows a large temperature rise at the time of heating, and if there is a defect that cools rapidly after heating, it can be any defect. It goes without saying that the same effect is exhibited. Also, like the conventional device of this kind, a division circuit may be used instead of the subtraction circuit, and any method for detecting a change in the infrared signal before and after heating, such as logarithmic conversion of the infrared signal as a preprocessing of the subtraction or division, may be performed. Even if an arithmetic circuit is used, the effect of the present invention will not be impaired.

Further, in recent years, a two-dimensional array detector has been put into practical use as an infrared detector. In this case, a scanning process performed by a scanning device, a synchronization process performed by a synchronization circuit, a signal separation process performed by a signal separation circuit, and a delay performed by a delay circuit. The processing is often performed by image processing using hardware, software, or both. In this case, the present invention also exerts the same effect. The synchronization circuit (8) and the signal separation circuit (7) are in the unheated area. The scanning device is provided for the purpose of separating the infrared signal, the infrared signal of the first heating region, and the signal of the second heating region, and an unheated region, a first heating region, and a second heating region individually. If the (5), the infrared detector, and (4) the amplifier (6) are provided, the synchronizing circuit (8) and the signal separating circuit (7) can be omitted. Is all It goes without saying that the same effect is exhibited.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface defect inspection device, and FIG. 2 is a diagram showing a conventional surface defect inspection device. In the figure, (1) is an inspected material, (2) is an inspected material conveying device, (3) is a heating device, (4) is an infrared detector,
(5) is a scanning device, (6) is an amplifier, (7) is a signal separation circuit, (8) is a synchronization circuit, (9) is a delay circuit, (10) is a subtraction circuit, (11) is a determination circuit, ( 12) is an indicator, (13)
Is a second delay circuit, and (14) is a second subtraction circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Scope of utility model registration request] 1. An inspecting material conveying device for conveying an inspecting material in a predetermined direction, a heating device for heating the surface of the inspecting material at a predetermined position, an unheated region before heating and heating by the heating device. The first and second heating regions having different time lapses after heating are scanned in a predetermined order, and an infrared detector for detecting infrared rays emitted by the region scanned by the scanning device, and An amplifier for amplifying the output of the infrared detector, a first delay circuit for delaying and outputting a first infrared signal from the unheated region amplified by the amplifier for a predetermined time, and the amplifier amplified by the amplifier. A second delay circuit for delaying and outputting a second infrared signal from one of the first and second heating regions by a time different from the delay time of the first delay circuit, and amplified by the amplifier. The first,
A first arithmetic circuit for subtracting or dividing the third infrared signal from the other of the second heating regions and the output signal of the first delay circuit, the third infrared signal and the second delay A second arithmetic circuit that subtracts or divides the output signal of the circuit, the output value of the first arithmetic circuit and the output value of the second arithmetic circuit are compared, and the surface of the material to be inspected according to the magnitude relationship. A surface defect inspection apparatus comprising a determination circuit for determining the presence or absence of a defect. 2. An inspected material conveying device for conveying the inspected material in a predetermined direction, a heating device for heating the surface of the inspected material at a predetermined position, an unheated region before heating and heating by the heating device. The first and second heating regions having different time lapses after heating are scanned in a predetermined order, and an infrared detector for detecting infrared rays emitted by the region scanned by the scanning device, and An amplifier for amplifying the output of the infrared detector, a first delay circuit for delaying and outputting a first infrared signal from the unheated region amplified by the amplifier for a predetermined time, and the amplifier amplified by the amplifier. A second delay circuit for delaying and outputting a second infrared signal from one of the first and second heating regions by a time different from the delay time of the first delay circuit, and amplified by the amplifier. The first,
A first arithmetic circuit for subtracting or dividing the third infrared signal from the other of the second heating regions and the output signal of the first delay circuit, the third infrared signal and the second delay A second arithmetic circuit that subtracts or divides the output signal of the circuit, compares the output value of the first arithmetic circuit and the output value of the second arithmetic circuit with a predetermined determination value, respectively, and compares the results. A surface defect inspection apparatus having a determination circuit for determining whether or not there is a surface defect in the material to be inspected.