JPS6281594A - Automatic inspection apparatus - Google Patents

Abstract

PURPOSE:To make it possible to inspect the quality of a matter to be inspected including the interior thereof with high accuracy, by arranging a transmitting coil and a receiving coil each of which has a magnetic body as a magnetic core in opposed relationship and exciting said coils by a high frequency current to measure the amplitude signal and phase signal of a receiving current. CONSTITUTION:A transmitting coil 1 and a receiving coil 2 each of which has a magnetic body such as ferrite as a magnetic core are arranged to both sides of a conveyor 3 feeding a product 4 and an exciting current is supplied to the coil 1 from the high-frequency oscillator located in a sensor main body 5. Now, when the product 4 approaches the gap between both coils, magnetic flux is concentrated to the metal part of the product 4 and mutual inductance changes. With the change of the mutual inductance, the receiving current of the coil 2 increases and, by comparing an amplitude signal and a phase signal with standard values, the quality of the product 4 is judged. By this method, the inspection of a whole shape can be performed including internal change such as the change of a wall thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to an automatic inspection device used, for example, to inspect the quality of objects to be detected such as products on a production line.

(Prior art and its problems) Conventional automatic inspection devices include the following.

(1) First conventional example A photoelectric switch having a light emitting part and a light receiving part is provided around the moving path of the object to be detected, and a shiny metal piece attached to a part of the object to be detected is detected. A large number of these photoelectric switches are provided to detect the area where the object to be detected is present, to detect the size of the object to be detected, and to inspect the quality of the object to be detected.

(ii) Second conventional example An ultrasonic sensor consisting of a transmitter that projects ultrasonic waves and a receiver that receives reflected ultrasonic waves is installed around the moving path of the object to be detected, and when the ultrasonic waves are transmitted, The size of the object to be detected and the presence of an opening were detected based on detection of the time difference from the time of reception and ultrasonic transmission detection, and the quality of the object was inspected.

In addition, when the object to be detected is a non-metal such as glass or plastic, and although it is outside the scope of the present invention, it is possible to Some devices are equipped with a proximity switch around the moving path of the detection object.

However, in the case of conventional examples having such a configuration, the purpose is to detect the shape of a part of the object to be detected, the presence or absence of an attached member, or the size of the object to be detected. This method had the disadvantage that it was not possible to inspect the entire shape or internal structure of an object.

Furthermore, for example, when inspecting a detected object transported by a belt conveyor, if the position where the detected object is placed on the belt conveyor changes, the detected object cannot be detected.
There was a drawback that inspections were likely to be omitted.

(Object of the Invention) The present invention has been made in view of the above circumstances, and is intended to enable accurate inspection of the entire shape of an object to be detected, including its interior, without causing any inspection omissions. The purpose is to

(Structure and Effects of the Invention) In order to achieve such an object, the present invention includes a transmitting coil whose magnetic core is a magnetic body disposed on one side in the width direction of a movement path of a metal object to be detected; a receiving coil whose magnetic core is a magnetic material disposed on the other side of the moving path in the width direction; a high-frequency oscillation circuit that outputs an excitation current to the transmitting coil; The apparatus is configured to include a determining means for detecting an amplitude signal and a phase signal corresponding to the detected object, and comparing the detected amplitude signal and phase signal with each of the preset amplitude signal and phase signal to determine whether the detected object is good or bad.

According to this configuration, when an excitation current is output from the high-frequency oscillation circuit to the transmitting coil, a magnetic field is formed across the transmitting coil and the receiving coil, and this magnetic field induces a current in the receiving coil. . When a metal object to be detected approaches the magnetic field, magnetic flux passes through the object, reducing the magnetic resistance on the receiving coil side, increasing the density of the magnetic flux linking the receiving coil, and increasing the receiving current. increase or
Alternatively, a level change occurs due to a decrease in the receiving current of the receiving coil due to eddy current loss, and in any case,
The level of the received current changes compared to when the detected object is not close. Based on the received current, an amplitude signal and a phase signal corresponding to the detected object are detected. These amplitude signals and phase signals are compared with preset amplitude signals and phase signals, such as those obtained by passing a magnetic field using a standard product as an object to be detected. If the difference is smaller than the set range, it is determined to be appropriate, and if it is larger, it is determined to be inappropriate, and based on this, the quality of the detected object is determined.

Therefore, a magnetic field is formed between the transmitting coil and the receiving coil, and the overall shape of the detected object is detected based on the change in the received current as the detected object crosses this magnetic field. For example, even if the object to be detected is box-shaped, if its wall thickness changes, this change will affect the received current as well, making it possible to accurately inspect the entire shape of the object, including its interior. Now you can.

In addition, it is only necessary for the object to be detected to cross the magnetic field formed between the transmitting coil and the receiving coil. Even if it shifts in the width direction of the conveyor,
It is now possible to avoid inspection omissions without being affected by the deviation. (Explanation of Embodiments) The present invention will be described in detail below based on embodiments shown in the drawings. FIG. 1 shows an automatic inspection device according to an embodiment of the present invention,
FIG. 2 is a perspective view showing a schematic configuration of the device, and FIG. 2 is a front view thereof.

In these figures, 1 is a transmitting coil, and 2 is a receiving coil, each of which is wound around a magnetic core made of a magnetic material such as ferrite. 3 is a belt conveyor that conveys a product 4 as an object to be detected, and the transmitting coil 1 is placed on one side of the moving path R formed by this belt conveyor 3 in the width direction, and the receiving coil 1 is placed on the other side of the moving path R formed by the belt conveyor 3. A coil 2 is provided respectively.

Reference numeral 5 denotes a sensor main body housing an electric circuit section, and this sensor main body 5, the transmitting coil 1, and the receiving coil 2 are connected to each other.
Each is connected via a power transmission cable 6.

As shown in FIG. 3, the transmitting coil l includes a high frequency oscillation circuit (O20) 7 that outputs an excitation current, a variable attenuator (ATT) 8, and a bandpass filter 9 that removes harmonic components from the excitation current. and a power amplifier circuit 10 that amplifies the excitation current after removing its harmonic components. ! An excitation means 2 consisting of : is connected.

A voltage amplification circuit 12 that amplifies the received current is connected to the receiving coil 2, and a rectifier circuit 13 that converts the received current into an amplitude signal is further connected to the voltage amplification circuit 12. The voltage amplification circuit 12 also includes a rectification circuit 13.
A phase comparison circuit (P/D) 14 is connected in parallel with the phase comparison circuit 14, and the high frequency signal from the excitation means 11 is inputted to the phase comparison circuit 14, and the phase comparison between the excitation current and the received current is performed and a phase signal is output. It is supposed to be done.

15 is a multiplexer (MPX), which includes an amplitude signal from the rectifier circuit 13 and a phase comparison circuit! It is designed to input any of the phase signals from 4.

16 is a CPU which outputs a control signal to the variable attenuator 8 to keep the output level of the transmitting coil 1 constant, and also outputs a control signal to the multiplexer 15 to control the reception from the receiving coil 2. The multiplexer 15 sequentially outputs an amplitude signal and a phase signal corresponding to the current.

17 is an A/D converter (ADC) that converts the amplitude signal and phase signal output from the multiplexer 15 into digital signals and inputs the digital signals to the CPU 16.

With such a configuration, as shown in FIG. 2, when a metal product 4 approaches the magnetic field formed between the transmitting coil l and the receiving coil 2, the metal part of the product 4 Magnetic flux concentrates on , and the mutual inductance between the transmitting coil I and the receiving coil 2 changes. Along with this, the receiving current of the receiving coil 2 increases, and based on the level change of this receiving current, a corresponding amplitude signal and a phase signal are obtained, and these amplitude signals and phase signals are sent to the multiplexer I.
5 and its multiplexer I5 to A
After /D conversion, the signal is input to the CPU 16, and the amplitude signal and the phase signal are each processed in the CPU 16.

The CPU 16 reads the digitally converted amplitude signal and phase signal input from the A/D converter 17, and detects the amplitude signal and phase signal corresponding to the product 4 based on both digital signals. The device is equipped with a determining means that compares the amplitude signal and phase signal set in advance to determine the quality of the product 4. Next, the operation of this determining means is described in the flowchart of FIG. This will be explained using the memory configuration diagram shown in the figure.

First, in the receiving coil 2, determine whether there is an amplitude change (F1), output a detection signal when there is an amplitude change (F2), and set a positive integer n in the memory area as shown in FIG. (F3).

Next, read the amplitude value induced in the receiving coil 2,
Store at memory addresses A and ~An (F4)
. Next, read the phase change and store P1 to Pn in the memory.
Store at address (F5).

After that, it is determined whether the amplitude value An just read has exceeded a predetermined threshold level (F6).
.

Here, if it is equal to or higher than the threshold level, the process moves to step F7j to increase (increment) n by 1, and then returns to step F4.

If it is above the threshold level, it is determined whether it is in the initial setting mode (F8), and if it is in the initial setting mode, the amplitude value An and phase value Pn read so far are stored at the standard value address SAn in the memory.

Store in SPn and return to step Fl. (F9~F1
0).

In step F8, if it is determined that it is not the initial setting mode, the amplitude standard value SAn and the amplitude value A read so far are
The absolute value DAn of the difference with n is calculated (Fil), and the absolute value DPn of the difference between the phase standard value SPn and the phase value Pn read so far is calculated (F12). Next, the sums ΣDAn and Σ of the absolute values DAn and DPn of the differences, respectively, are calculated.
An additional value T (=ΣDAn+ΣD P n) of DPn is calculated (F13).

Thereafter, the added value T reaches a predetermined threshold level δ
(F14), and if the added value T is smaller than the threshold level δ, it is assumed that the changes in the amplitude signal and phase signal of the product 4 detected and measured this time are similar to the standard object. OK double signal output F
15), return to step Fl. On the other hand, if the additional value T is equal to or higher than the threshold level 6, the product 4 is rejected as an object that is not similar to the standard object and does not conform to the standard object.
The signal is output F'16) and the process returns to step Fl.

Based on the above configuration, when determining the quality of the product 4, first, the product 4 as a standard object is conveyed by the belt conveyor 3, and based on the amplitude signal and phase signal, the sixth
As shown by solid lines in (a) and (b) of Fig. 7, the standard amplitude value SAn and the standard phase value SPn
, and store it in memory as mentioned above.

After that, the product 4 to be inspected is transported by the belt conveyor 3, and the product 4 approaches the magnetic field formed by the transmitting coil 1 and the receiving coil 2, causing a level change in the received current. (see Figure 7(c)), two-dot chain line L2 is drawn in (a) and (b) of Figures 6 and 7, respectively.
As shown in , the amplitude value An and phase value Pn obtained from the product 4 are determined, and the absolute value DAn of the difference,
Calculate DPn. Finally, the absolute value of the difference DAn
, DPn, calculate the added value T, that is, the area of the shaded portion in each of FIGS. 6, 7 (a) and (b), and compare the added value T with the threshold level δ for discrimination. Based on the discrimination results, Figure 7 (
As shown in d), an OK signal or an NG signal is output to determine whether the product 4 is good or bad.

As the standard amplitude value SAn and the standard phase value SPn, values specified from the design of the product 4 may be assigned. In short, the amplitude signal and the phase signal, which serve as standards for determining the quality of the product 4, All you have to do is set it in advance.

[Brief explanation of drawings]

1 is a perspective view showing a schematic configuration of an automatic inspection device according to an embodiment of the present invention, FIG. 2 is a front view of FIG. 1, FIG. 3 is a circuit block diagram, and FIG. 4 shows the operation of the discriminating means. 5 is a memory configuration diagram, FIG. 6 is an explanatory diagram of the discrimination method, and FIG. 7 is a time chart. l...Transmission coil, 2...Reception coil, 4...
-Product as an object to be detected, 7...High frequency oscillation circuit, R...Movement route.

Claims (1)

[Claims] (1) A transmitting coil whose magnetic core is a magnetic body disposed on one side in the width direction of the moving path of the metal detection object, and a magnetic core is a magnetic body placed on the other side in the width direction of the moving path. a receiving coil; a high-frequency oscillation circuit that outputs an excitation current to the transmitting coil; and detecting an amplitude signal and a phase signal corresponding to the detected object based on the received current of the receiving coil, and detecting preset amplitude signals and phase signals. An automatic inspection device comprising: a determining means for comparing the amplitude signal and the phase signal to determine whether the object to be detected is good or bad.