JPH06201651A - Electromagnetic induction-type sensor - Google Patents

Abstract

PURPOSE:To inspect a spot-welded nugget part without detaching a spot-welding electrode and with sufficient inspection accuracy. CONSTITUTION:Iron sheets 1a, 1b are spot-welded by individual spot-welding electrodes 10, 14, a nugget 7 is produced, the spot-welding electrode 10 is used as an iron core for a first sensor 5 and a second sensor 6, and the part of the nugget 7 is inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction type sensor used in an electromagnetic induction type inspection apparatus for inspecting an abnormality of an object to be inspected by a change in electromagnetic induction, and particularly to foods, chemical tablets, synthetic resin products, The present invention relates to an electromagnetic induction type sensor used in an electromagnetic induction type inspection device for inspecting an abnormality of an inspection object such as a work.

[0002]

2. Description of the Related Art When an object is placed in an alternating magnetic field, the value of a magnetic circuit changes and the magnetic flux changes, and the value of an electromotive voltage induced in a coil (reception coil) placed in the same alternating magnetic field is changed. It is known to change.

In this case, the value of the magnetic circuit is a value according to the permittivity, magnetic permeability, physical size, position in the magnetic field, etc. of an object placed in an alternating magnetic field. Placing the object in an alternating magnetic field with some of them constant will allow other unknowns to be accurately identified.

Many electromagnetic induction type inspection apparatuses have been proposed that apply this principle and have a nondestructive inspection function such as identification of an object to be inspected and recognition of the presence or absence of a specific substance.

FIG. 5 is a block diagram showing an example of such an electromagnetic induction type inspection apparatus. The electromagnetic induction type inspection apparatus shown in this figure has an inspection coil 10 arranged in the vicinity of the inspection object 101.
2 and an inductance balancing coil (inductor) 103, two balancing resistors 104 and 105, an AC power supply 107 for driving the bridge circuit 106, and an output from the bridge circuit 106. An amplifier circuit 108 is provided which takes in a detection signal (a signal having a value corresponding to the balance deviation of the bridge circuit 106) and amplifies and outputs it.

Then, in a state in which a reference inspection object (reference object) is placed in the magnetic field 109 generated by the inspection coil 102, the respective values of the resistors 104 and 105 and the inductor 103 are adjusted to adjust the bridge circuit. By balancing 106 and keeping the value of the detection signal output from the bridge circuit 106 to zero, the object to be inspected 10 in the magnetic field 109 generated by the inspection coil 102.
When 1 comes in, if the object 101 to be inspected is different from the reference object, the value of the magnetic circuit through which the magnetic field 109 generated by the inspection coil 102 is changed and the self-inductance is changed.

As a result, the balance of the bridge circuit 106 is lost, the value of the detection signal output from the bridge circuit 106 becomes a value other than zero, and the detection signal is amplified by the amplifier circuit 108 and output to the outside. To be done.

In this case, the value of the detection signal output from the bridge circuit 106 includes the material and magnetic permeability of the reference object, the physical size, the moving speed, and the material and magnetic permeability of the inspection object 101. When the reference object and the object to be inspected 101 are different from each other in terms of material, magnetic permeability, physical size, moving speed, etc. Can be detected and notified to the outside.

In addition to the electromagnetic induction type inspection apparatus described above, for example, the electromagnetic induction type inspection apparatus shown in FIG. 6 is also known. The electromagnetic induction type inspection apparatus shown in this figure includes an AC power supply 115 that generates an AC current, and a transmission coil 116 that is excited by the AC current obtained by the AC power supply 115.
And the magnetic field 1 generated by the transmission coil 116, which is arranged at a predetermined distance from the transmission coil 116.
First receiving coil 11 for generating an induced electromotive voltage by means of 17
8 is wound in the opposite direction to the first receiving coil 118 and is spaced apart from the transmitting coil 116 by a predetermined distance, and an induced electromotive voltage is generated by the magnetic field 117 generated by the transmitting coil 116. The second receiving coil 119 and an amplifier circuit 120 for amplifying a difference signal (detection signal) between the induced electromotive voltage of the second receiving coil 119 and the induced electromotive voltage of the first receiving coil 118 are provided.

The transmitter coil 116 and the first and second coils
The position of the first receiving coil 118 or the second receiving coil 119 is adjusted in a state where the inspection object 121 is not present between the receiving coils 118 and 119 (inspection path) 122, and the first receiving coil 118 and the second receiving coil 119 are adjusted.
The induced electromotive force obtained by the receiving coil 118, and the second
By setting the induced electromotive force obtained by the receiving coil 119 to be offset, when the inspection object 121 enters the inspection path 122, this inspection object 12
The induced electromotive voltage generated in the first receiving coil 118 and the induced electromotive voltage generated in the second receiving coil 119 are not balanced according to the position of 1, and output from these first and second receiving coils 118 and 119. The detected signal has a value other than zero, is amplified by the amplifier circuit 120, and is output to the outside.

In this case, the first and second receiving coils 118,
Since the value of the detection signal output from 119 is a unique value determined by the material, magnetic permeability, physical size, moving speed, etc. of the inspection object 121, the value of the reference inspection object is measured in advance. By doing so, when the material, magnetic permeability, physical size, moving speed, etc. of the inspection object 121 are different from the reference inspection object, this can be detected.

[0012]

By the way, each of such electromagnetic induction type inspection devices has the following problems. That is, in the electromagnetic induction type inspection apparatus shown in FIG. 5, the inspection object 101 has to be arranged within the range to be inspected by the inspection coil 102. Therefore, when inspecting a nugget portion made by spot welding, After welding, the spot welding electrode must be removed to attach the inspection coil 102 to the nugget portion, which is troublesome and the inspection coil 102
Therefore, the position of the nugget is often displaced, and there is a problem that sufficient inspection accuracy cannot be ensured.

Further, the electromagnetic induction type inspection apparatus shown in FIG. 6 has a problem that it is impossible to inspect the nugget portion made by spot welding because the entire inspection path 122 is in the inspection range. In view of the above circumstances, the present invention provides an electromagnetic induction sensor capable of inspecting the quality of a nugget portion with sufficient inspection accuracy without removing the spot welding electrode when inspecting the nugget portion of spot welding. The purpose is to do.

[0014]

In order to achieve the above-mentioned object, an electromagnetic induction type sensor according to the present invention is an object for inspecting a transmitting coil for generating a magnetic field, an electrode for spot welding, and a magnetic field generated by the transmitting coil. The rod-shaped member used as a magnetic path for concentrating on the nugget, and the receiving coil for generating an induced electromotive voltage according to the magnetic field transmitted through the nugget.

[0015]

In the above structure, after the spot welding is performed by the rod-shaped member to form the nugget, the magnetic field is generated by the transmitting coil, the magnetic field is concentrated on the nugget by the rod-shaped member, and the nugget is generated by the receiving coil. A magnetic field transmitted through this nugget is detected and an induced electromotive voltage is generated.

[0016]

1 is a block diagram showing an example of an electromagnetic induction type inspection apparatus using an example of an electromagnetic induction type sensor according to the present invention.

The electromagnetic induction type inspection apparatus shown in this figure has a first sensor (first electromagnetic induction type sensor) 5, one spot welding electrode 10, and a second sensor (second electromagnetic induction type sensor) 6.
And the other spot welding electrode 14 and the control device 8 are provided, and the tip (lower end in FIG. 1) of one spot welding electrode 10 is brought into contact with one iron plate 1a,
After the tip (upper end in FIG. 1) of the other spot welding electrode 14 is brought into contact with the other iron plate 1b to spot weld them, the controller 8 drives the first sensor 5 and the second sensor 6 and First sensor 5
And based on the detection result of the second sensor 6, it is detected whether or not there is an abnormal portion in the nugget 7 portion formed by spot welding, and the detection result is notified.

One spot welding electrode 10 is a copper rod-shaped member which is arranged so as to penetrate the center of the first sensor 5 and the center of the second sensor 6, and a part of the rod-shaped electrode is held by a plug 21. While the voltage is being applied via the cord 20 connected to the plug 21, the voltage is applied to one iron plate 1a which is used as a spot welding electrode and the lower end portion of which is in contact. Further, while the application of the voltage is stopped, the magnetic flux generated by the second sensor 6 is used as a magnetic circuit of the first sensor 5 and the second sensor, and the magnetic flux generated by the second sensor 6 is a tip portion (a lower end portion in the figure). Concentrate on.

The other spot welding electrode 14 is a rod member made of copper which is arranged at a position facing the one spot welding electrode 10 with the iron plates 1a and 1b interposed therebetween, and a part of the rod member is a plug. The other iron plate 1b which is sandwiched by 16 and whose upper end is in contact when a voltage is applied through the cord 12 connected to this plug 16
A voltage is applied to the iron plate 1a and the iron plate 1a is spot-welded to form a nugget 7.

The first sensor 5 includes a transmitting coil 11 wound around the spot welding electrode 10 and a receiving coil 13 wound around the outer periphery of the transmitting coil 11.
When an alternating current is output from the control device 8, the transmitting coil 11 generates an alternating magnetic field and the receiving coil 13 generates an induced electromotive voltage according to the magnitude of the alternating magnetic field. This is supplied to the second sensor 6.

The second sensor 6 is provided with a transmission coil 15 wound around the lower side of the one spot welding electrode 10 and a reception coil 17 wound around the outer periphery of the transmission coil 15. When an alternating current is output from the control device 8, an alternating magnetic field is generated by the transmission coil 15,
The one spot welding electrode 10 concentrates this on the tip, and the receiving coil 17 generates an induced electromotive voltage according to the magnitude of the alternating magnetic field. Further, this induced electromotive voltage and the first sensor 5 output the induced electromotive voltage. The induced electromotive voltage is added in reverse phase to generate a differential voltage, which is supplied to the control device 8 as a detection signal.

In this case, each spot welding electrode 10, 14
By spot welding the iron plates 1a, 1b to the nugget 7
Since the spot welding electrode 10 is used as an iron core of the first sensor 5 and the second sensor 6 to inspect the nugget 7 portion, the nugget 7 is produced immediately after spot welding.
The quality of the portion is inspected and the inspection result is supplied to the control device 8 in the form of a differential voltage.

The control unit 8 has a drive unit 25 as shown in FIG.
, Analog processing unit 26, and upper limit value setting switch circuit 2
7, the lower limit value setting switch circuit 28, and the reset circuit 2
9, a digital processing unit 30, two display lamps 31,
32 and an LED indicator 33, which generate an alternating current to generate a second coil 11 and a second coil of the first sensor 5.
The transmitter coil 15 of the sensor 6 is excited, and the differential voltage (detection signal) between the induced electromotive voltage of the receiving coil 13 of the first sensor 5 and the induced electromotive voltage of the receiving coil 17 of the second sensor 6 is taken in and is used. Is digitized to create detection data, which is displayed by the LED display 33, and the level is discriminated to inspect whether or not there is an abnormality in the nugget 7 portion.
Displayed by 32.

The driving unit 25 oscillates at a preset frequency to generate an AC signal as shown in FIG.
5, an amplifier circuit 36 for taking in and amplifying the AC signal output from the oscillator circuit 35, a variable resistor 37 for zero adjustment operated when performing zero adjustment, and an amplifier circuit 36 for output. A voltage limiting circuit 38 that takes in an alternating current signal to generate two alternating current signals, and sets one of the alternating current signals to a magnitude set by the variable resistor 37, and outputs from the voltage limiting circuit 38. And a power amplifier circuit 39 for amplifying the electric power by taking in two AC signals. The two AC currents are generated to generate the transmission coil 11 of the first sensor 5 and the transmission coil 15 of the second sensor 6, respectively. While being excited in the same phase, a synchronization signal (AC signal) synchronized with the AC current is generated and supplied to the analog processing unit 26.

The analog processing unit 26 takes in the differential voltage (detection signal) between the induced electromotive force of the receiving coil 13 of the first sensor 5 and the induced electromotive force of the receiving coil 17 of the second sensor 6 and pre-amplifies it. The preamplifier circuit 40 and the detection signal output from the preamplifier circuit 40 are taken in,
A phase detection circuit 41 that synchronously rectifies the detection signal based on a synchronization signal output from the drive unit 25, and a span adjustment variable resistor 4 that is operated when performing span adjustment.
2, a low-pass filter circuit 43 that takes in the detection signal output from the phase detection circuit 41 and cuts high-frequency components in the detection signal based on the span set by the variable resistor 42, and this low-pass filter. An A / D conversion circuit 44 is provided, which captures the detection signal output from the circuit 43 and digitizes the captured detection signal in synchronization with the sampling signal output from the digital processing unit 30 to generate detection data. ing.

The receiving coil 1 of the first sensor 5
The differential voltage (detection signal) between the induced electromotive voltage of No. 3 and the induced electromotive voltage of the receiving coil 17 of the second sensor 6 is taken in, and the detection signal is synchronously rectified based on the synchronous signal output from the drive unit 25. After that, low-pass filtering is performed to cut high-frequency components, and every time a sampling signal is output from the digital processing unit 30, the detection signal with the high-frequency components cut is A / D converted to generate detection data. Is supplied to the digital processing unit 30.

The upper limit value setting switch circuit 27 is provided with a switch necessary for setting the upper limit value data of the preset number of bits, and the data set by this switch, that is, the inspection target. The upper limit value data necessary for determining whether or not there is an abnormality in the nugget 7 portion is supplied to the digital processing unit 30. Further, the lower limit value setting switch circuit 28 includes a switch necessary for setting the lower limit value data of the preset number of bits, and the data set by this switch, that is, the nugget to be inspected. The lower limit data necessary for determining whether or not there is an abnormality in the 7th part is supplied to the digital processing unit 30.

Further, the reset circuit 29 is provided with a switch operated when resetting the entire apparatus,
When this switch is operated, a reset signal is generated and supplied to the digital processing unit 30.

The digital processing section 30 has a starting switch 50 which is operated when the apparatus is started as shown in FIG.
And a setting switch 51 that is operated when reading the respective data set in the upper limit value setting switch circuit 27 and the lower limit value setting switch circuit 28, and the output of the setting switch 51 and the starting switch. 5
A microprocessor 52 that performs various data processing based on the output of 0 and the output of the reset circuit 29, and a decode circuit 53 that takes in and decodes the selection data output from the microprocessor 52 to generate a selection signal. I have it.

Further, when the reset signal is output from the reset circuit 29, the digital processing unit 30 is reset, and the detection data output from the analog processing unit 26 and the upper limit value setting switch circuit 27 are output. Upper limit value data, lower limit value setting switch circuit 2
The lower limit data output from 8 is taken in, and among these detection data, upper limit data, and lower limit data,
The data designated by the selection signal output from the decoding circuit 53 is selected and supplied to the microprocessor 52, and the data is stored in the address designated by the address data output from the microprocessor 52. Read constant data etc.,
An ultraviolet erasable EP-ROM circuit 55 for supplying this to the microprocessor 52, and numerical data output from the microprocessor 52 based on a control signal output from the microprocessor 52 are fetched and decoded. And an LED decode driver circuit 56 for generating LED drive data.

Then, the microprocessor 52 operates based on the outputs of the setting switch 51, the output of the starting switch 50 and the output of the reset circuit 29 to control the selection circuit 54, and the analog processing section 26 The LED decoder driver circuit 5 is selectively loaded with any one of the detection data output, the upper limit value data output from the upper limit value setting switch circuit 27, and the lower limit value data output from the lower limit value setting switch circuit 28.
After converting the value of the detection data into LED drive data by 6, the data is supplied to the LED display 33, and the upper limit value data, the lower limit value data, and the detection data are compared to obtain the detection data. It is determined whether the value is in the correct range, and when the detection data is in the correct range, a good signal is generated and supplied to one of the display lamps 31, and the detection data is out of the correct range. When it is out, a defective signal is generated and supplied to the other display lamp 32.

One of the display lamps 31 is provided with a lamp that lights up when a good signal is output from the digital processing section 30 and a blue lamp cover that transmits light.
When a good signal is output from the digital processing unit 30, it lights up and emits blue light, and there is no abnormal portion in the nugget 7 inspected by the first sensor 5 and the second sensor 6 by an operator or the like. To inform.

The other display lamp 32 is provided with a lamp that lights up when a defect signal is output from the digital processing section 30 and a red lamp cover that transmits light. When a defect signal is output, it lights up and emits red light to notify the operator or the like that the nugget 7 inspected by the first sensor 5 and the second sensor 6 has an abnormal portion.

Further, the LED display 33 is provided with a plurality of segment display elements, and takes in the LED drive data output from the digital processing section 30 and displays the LED drive data numerically by each segment display element.

As described above, in this embodiment, the iron plates 1a and 1b are spot-welded by the spot-welding electrodes 10 and 14 to form the nugget 7, and then the spot-welding electrodes 10 are attached to the first sensor 5 and the second sensor. Since the nugget 7 part is inspected by using it as an iron core of No. 6, it is possible to inspect the quality of the nugget 7 part immediately after spot welding, and when the nugget part made by spot welding is inspected, It is possible to inspect the quality of the nugget 7 portion with sufficient inspection accuracy without removing the welding electrode 10.

[0036]

As described above, according to the present invention, when the nugget portion of spot welding is inspected, the quality of the nugget portion can be inspected with sufficient inspection accuracy without removing the spot welding electrode. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an electromagnetic induction type inspection apparatus using an embodiment of an electromagnetic induction type sensor according to the present invention.

FIG. 2 is a block diagram showing a circuit configuration example of a control device shown in FIG.

FIG. 3 is a block diagram showing a detailed circuit configuration example of a drive unit and an analog processing unit shown in FIG.

FIG. 4 is a block diagram illustrating a detailed circuit configuration example of a digital processing unit illustrated in FIG.

FIG. 5 is a configuration diagram showing an example of a conventionally known electromagnetic induction type inspection apparatus.

FIG. 6 is a configuration diagram showing another example of a conventionally known electromagnetic induction type inspection device.

[Explanation of symbols]

 1a, 1b Iron plate 5 1st sensor 6 2nd sensor 7 Nugget 8 Control device 10, 14 Spot welding electrode 11, 15 Transmitting coil 13, 17 Receiving coil

Claims (1)

[Claims] 1. A transmission coil for generating a magnetic field, an electrode for spot welding, a rod-shaped member used as a magnetic path for concentrating the magnetic field generated by the transmission coil on a nugget to be inspected, and the nugget transmitted therethrough. An electromagnetic induction type sensor comprising: a receiving coil that generates an induced electromotive voltage according to a magnetic field.