JPS61246610A - Thickness measuring device using ultrasonic wave - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an apparatus for measuring thickness using ultrasonic waves. This thickness measuring device is used, for example, in a device that automatically measures the thickness of steel pipes.

[Conventional technology and its problems] Many devices that measure thickness using ultrasonic waves are known to date, but all of these measurement devices always have many problems and drawbacks. . These conventional measuring devices fall into two types of devices. That is, they are classified into electromagnetic coupling type devices and devices using piezoelectric transducers.

The first type of conventional measuring devices all use one electromagnetic acoustic transducer. This transducer acts alternately as a transmitter and a receiver.

When acting as a transmitter, this transducer generates transverse waves perpendicular to the surface of the thickness to be measured, and when acting as a receiver, it detects the reflected waves of the generated transverse waves. By measuring the time interval between two successive reflected waves, the thickness of the object to be measured is determined.

These measuring devices essentially have three problems. In order to obtain the required magnetic field, it is necessary to set the magnetic pole gap very small. As a result, when measuring the thickness of a component or element placed on a production line, it is difficult to
The device cannot be used for measurements. For example, in the case of a steel pipe, it must be straight. Such requirements are rarely met in industrial production lines. It is also necessary for such a measuring device that the inner and outer surfaces defining the thickness to be measured are parallel to some extent. The reason is that if these surfaces are tilted to each other by more than a certain angle, the ultrasound signal will not be detected by the receiver. Finally,
Determining the thickness requires determining the maximum value of the envelope of the reflected signal, which reduces the accuracy of the measurement.

Conventional measuring devices of the second type (using piezoelectric transducers) have further drawbacks. In other words, in this measurement device, in order to transmit the ultrasonic waves from the piezoelectric crystal that generates the ultrasonic waves to the part to be measured, it is necessary to provide a transmission medium such as water, oil, or special grease. .

The object of the invention is therefore to obtain a thickness measuring device which does not have the above-mentioned drawbacks.

[Means for Solving the Problems and Their Effects J In the thickness measuring device according to the invention, ultrasonic waves are generated directly on the surface of the part to be measured. The action for generating ultrasonic waves on the surface of the part is an electromagnetic action and does not require physical contact between the transmitter or receiver and the part to be measured. Further, the method of generating the magnetic field is a method that allows a large space to be provided at the location where the magnetic field is generated, and there is sufficient room within this space to insert and arrange the converter.

Therefore, the present invention relates to a thickness measuring device using ultrasonic waves having a coil for generating an electromagnetic field, a shoe, and a circuit extending thereto, wherein the coil for generating an electromagnetic field is the associated circuit comprises a control circuit; the control circuit comprises a pulse generator; the output of the pulse generator is connected through an amplifier to a transmitter coil mounted on the shoe; a receiving coil is mounted within the shoe at a distance from the transmitting coil;
The receiving coil is connected to logic and control l through a receiver circuit.
the output end of the logic and TSM circuit is connected to a measurement result indicating device through a digital circuit, and the shoe is located in the center of the annular coil. A measurement device is obtained.

In practice, pancake-shaped coils are used.

This pancake-shaped coil is composed of a plurality of parallel conductors, through which large current pulses flow in a circular manner. Create an image of the current in the coil (as occurs in a transformer). This image current interacts with a continuous strong magnetic field within the space in which the part to be measured exists, producing a normal force at an angle to the plane created by the magnetic field and current. In this way, tension and compression forces are created on the surface of the object to be measured, and these forces generate ultrasound waves. Conversely, when ultrasonic waves that have been generated and propagated in various compatible modes enter the area corresponding to the receiving coil, a current is generated in the receiving coil, and by measuring and processing this current as a signal. The thickness of the part to be measured can be determined.

The coil used in this case is a pancake-shaped coil with a plurality of parallel conductors through which a current circulates. Because of the shape of the coil, the if flow circulates in opposite directions in adjacent conductors.

An alternating force acts on the lower region of each conductor, and this force causes vibrations on the surface of the portion. This vibration generates ultrasonic waves that propagate in all directions inside the part.

Since the coupling efficiency of the type described above is significantly lower than in conventional measuring devices, special electronic techniques and strong magnetic fields are required to carry out measurements in this case.

Depending on the material of the object to be measured, in some cases such measurements can take advantage of the occurrence of magnetostrictive phenomena, in which case it is possible to carry out measurements over very small magnetization ranges. can be done. This is especially true in the case of soft carbon steel.

Ultrasonic waves are generated and kW41! ! In I, longitudinal and transverse waves are generated on the surface of the part being measured, and the same happens with each successive reflection.

At the same time, sound waves are generated that are specific to the thickness of the material being measured.

With each reflection, a new train of longitudinal and transverse waves is generated as a characteristic wave, and eventually a mixed series of these waves reaches the receiver.

Examples The present invention will be better understood from the following description with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the invention.

FIG. 1 shows a thickness measuring device according to the present invention, which measures the thickness of a steel pipe. It is assumed that this steel pipe is moving in the direction of the arrow. A shoe 3 is placed on the steel pipe 1 and slides over the steel pipe 1. Shoe 3 is rotatably attached to base 5 by interlocking arms 4a and 4b. One end of the arm 4a is connected to one end of the air piston 6. The other end of this air piston 6 is the base 5
can be attached to. The air piston 6 allows the shoe 3 to move in the vertical direction, and maintains contact between the shoe 3 and the steel pipe 1. An ultrasonic transmitter and receiver are mounted on the shoe 3, and the transmitter and receiver are separated by a set distance.

The shoe 3 is in the magnetic field created by the toroidal coil 2.

Information regarding changes in the thickness of the steel pipe 1 is obtained through changes in the phase of the ultrasonic waves. The signals used result from successive reflections and generation of longitudinal and transverse waves, so that the information enters the receiver in continuous form.

With this measurement device, information is not lost even when the inner and outer surfaces of the steel pipe are not parallel, and the problem of the narrow gap between the magnetization yoke and the part to be measured in conventional devices can be avoided. is avoided.

The electronic circuit shown in FIG. 2 generates a high frequency current of about 2 MHz, which is transmitted by a transmitter toward the surface of the steel pipe 1 to be measured. Ultrasonic waves are generated at the surface of the steel pipe 1, and the ultrasonic waves propagate through the thick portion of the steel pipe at an angle of about 30°, are reflected at the inner surface of the steel pipe 1, and propagate again toward the outer surface. When the ultrasound waves reach the outer surface, they are reflected again. The above process is continuously repeated until the wavefront reaches the receiving coil 11. The elapsed time from the time the ultrasound is emitted to the time it arrives is measured, and from this time data and the propagation velocity of the ultrasound in the medium being measured, the path length traveled by this ultrasound train is determined. .

The important thing to note here is that the information regarding the thickness change is not given as an amplitude change as is conventional, but as a phase change.

For this reason, the thickness measuring device according to the invention is less susceptible to electrical noise. This electrical noise had a large effect on conventional measuring devices.

The device for measuring thickness includes a control circuit 12, a transmitter circuit 13, a pancake-shaped transmitting coil 10, a pancake-shaped receiving coil 11, a receiver circuit 14, an analog circuit 15, and a digital circuit. 16. The control circuit 12 is connected to an actual transmitter circuit 13 , which is connected to the pancake-shaped transmit coil 10 . The pancake-shaped receiving coil 11 is the actual receiver circuit 1
4, and this actual receiver circuit 14 is interconnected to an analog circuit 15, a digital circuit 16 and a control circuit 12. The output of this digital circuit 16 is connected to an indicating device 17 for displaying the measurement results obtained and to a graphic recorder 18.

The control circuit 12 includes a synchronous oscillator 19 and a pulse train generator 20. The synchronous oscillator 'a19 generates a clock signal synchronized with the 50MH2 oscillator, and the output end of the synchronous oscillator 19 is connected to the pulse train generator 20. The surface of the object to be measured is excited with these pulses, thereby generating ultrasonic waves within the volume of the object to be measured. The output of the pulse train generator 20 sends out a pulse train at a frequency of 1.79 MHz every 2 milliseconds.

The output end of this pulse train generator 20 is connected to the transmitter circuit 13. This transmitter circuit 13 is composed of a transmitter amplifier 21. This transmitter circuit 13 amplifies the pulse train generated by the 11J I11 circuit 12 and supplies a current of about 50 amperes to the pancake-shaped transmitting coil 10.

A pancake-shaped receiver coil 11 receives the radiated signal and sends this signal to a receiver circuit 14. This receiver circuit 1
4 is composed of a receiver amplifier 22. This amplifier 22 converts the signal peak-to-peak.
k) Amplify to the extent of 3 or 4 volts in amplitude.

The output line of this receiver amplifier 22 is connected to the analog circuit 15.

This analog circuit 15 is comprised of a device that passes the received and amplified pulse train signal through a filter, and further amplifies and shapes it. Due to the operation of this device, the pulse trains appearing at the output of the analog circuit 15 all have the same amplitude, but the information is contained in the phase of each output pulse with respect to the original pulse train.

The output end of analog circuit 15 is connected to digital circuit 16 . This digital circuit 16 is connected to the pulse selection circuit 2
3, a window generator 24, a counter 25, and a DA converter 26. The pulse selection circuit 23 is connected to the window generator 24 and the counter 25, the output terminal of the counter 25 is connected to the DA converter 26, and the input terminal of the counter 25 is connected to the pulse selection circuit 23 through an AND gate. It is connected to receiver circuit 14 and window generator 24 . The output of the DA converter 26 is connected to the graphics recorder 18 and the support device 17 for display.

The digital circuit 16 is the central point where all the signals of the measuring device converge. These signals are processed here and then sent to the graphics recorder 18 and the indicating device 17.
sent to. The indicating device 17 is in this case, for example, a millimeter. These display devices visually display variations in the thickness of the steel pipe 1.

Window generator 24 is also connected to synchronization generator 19, which indicates the time at which the time count has to start.

The pulse selection circuit 23 can send out a predetermined signal by the selection switch 27 and select a given pulse. As a result, the thickness can be determined by measuring the movement within the II.

The counter 25 is connected to a central oscillator providing a 50MH2 pulse signal. This signal has very short pulse intervals and is used to precisely count time.

The window signal from the window generator 24, the pulse selection signal from the pulse selection circuit 23, and the signal sent from the receiving coil 11 are combined to obtain two pulses. The first pulse corresponds to the start of the window and the second pulse corresponds to the selected pulse. These two pulses are fed to a counter 25. The counter 25 is
Count the 50 MHz pulses from the moment the first pulse triggers until the moment the second pulse stops the counter 25.

This information is sent to a DA converter 26 where it is converted to a continuous current of variable amplitude. The amplitude of this continuous current is visually displayed on the indicator 17, which indicates the thickness.

A graphic recorder 18 is connected in parallel with the pointing device 17. This graphic recorder 18 continuously displays thickness variations.

FIG. 3a shows a thickness variation curve obtained with a measuring device according to the invention, and FIG. 3b shows a thickness variation curve obtained with a conventional measuring device.

The steel pipe used for the above two measurements is 16.81 API
It is a J-35 steel pipe, and its thickness is 8.94 mm.

In the measurement shown in FIG. 3a using the measuring device of the invention, the steel pipe 1 is moving at a speed of 0.8 m/s and the recording paper of the graphic recorder 18 is moving at a speed of 50 IIR/s. is moving. The conventional measuring device used is a RAMER DM-2 ultrasound device with a frequency of 2 MHz.

Using a conventional measuring device, 42 measurements were carried out on the stopped steel pipe and by interpolation of the measurements obtained, the final variation curve shown in FIG. 3b was obtained.

Although the problem of time loss when using a conventional measuring device compared to the measuring device according to the invention is not an issue, the accuracy of the curve obtained by the measuring device according to the invention (FIG. 3a) is lower than that of the conventional measuring device. Songs 1!3 (3
It should be clear that the accuracy is far superior to that shown in Figure b).

FIG. 3a shows only a portion of the measured results, which correspond to an area of about 2 m of the steel pipe. Conventional measuring equipment was used for this 2 m range.

FIG. 4 shows a second preferred embodiment of the electrical circuit of the measuring device according to the invention.

This embodiment includes a control circuit 12, a transmitter circuit 13, a pancake-shaped transmitting coil 10, a pancake-shaped receiving coil 11, a receiver circuit 14, a logic and 1II111 circuit 15, and a digital circuit 16. have The υ11m circuit 12 is connected to an actual transmitter circuit 13, and this transmitter circuit 13 is connected to the pancake-shaped transmitting coil 10.

The pancake-shaped receiver coil 11 is connected to a receiver circuit 14 which is interconnected with logic and control circuits 15, digital circuits 16 and control circuits 12.

The output of the digital circuit 16 is connected to an indicating device 17 for displaying the measurement results obtained and to a graphic recorder 1.
Connected to 8.

Control circuit 12 has a microprocessor 30 . This microb0 setter 30 monitors the main functions of the measuring device.

This microprocessor 30 includes a scale verification circuit 31,
There is mutual communication between the synchronous generator 32, the PLL (Phaselocked 1 loop) variable frequency oscillator 33, the pulse train generator 34, and the 1 loop generator 37 provided in the actual receiver circuit 14. connected to.

A PLL type variable frequency oscillator 33 is connected to a pulse train generator 34, and the output end of this pulse train generator 34 is connected to the transmitter circuit 13. This transmitter circuit 13 is composed of an amplifier 35 which amplifies the received pulse train and supplies the amplified signal to the pancake-shaped transmitting coil 10.

Pancake-shaped receive coil 11 receives the transmitted signal and passes this signal to bandpass filter and amplifier 36 . This bandpass filter and amplifier 36 is connected to an envelope generator 37 whose output is connected to the logic and control circuit 15.

The output of the logic and control circuit 15 is connected to a counter 38;
It is connected to AND gate 39 and variable frequency oscillator 33 . The counter 38 and the AND gate 39 form part of the digital circuit 16, and the variable frequency oscillator 33 forms part of the control circuit 12. counter 38
further includes a D-A converter 40 and a frequency of 200 MH
A signal generator 41 that generates a signal of z, and an AND gate 3
9 and the microprocessor 30.

The output end of the DA converter 40 is connected to the indicating device 17 and the graphic recorder 18.

Digital circuit 16 also includes a window generator 42 . This window generator 42 is connected to the input of the AND gate 39, to the synchronous generator 32, and to the pulse train generator 34.

In scale verification mode, microbe 0 setter 30 is PLL
The variable frequency oscillator 33 is commanded to scan a fixed frequency range. Then, the pulse train generator 34 sends the pulses of this frequency to the amplifier 35 for power amplification.
The amplifier 35 sends a large current pulse signal to the transmitting coil 10.

Receiving coil 11 receives the transmitted signal from transmitting coil 10, and the received signal is sent to a bandpass filter and amplifier 36 stage. This signal is received by envelope generator 37 and fed back to microprocessor 30.

The above process is repeated until the maximum amplitude is detected in the receiving coil 11. If a maximum amplitude is detected, this indicates that the fundamental mode for this scale calibration thickness is excited.

Once this frequency is detected, the operating mode is switched.

In this mode of operation, microprocessor 30 identifies the output frequency of variable frequency oscillator 33 and synchronous generator 32
Set. When the synchronization generator 32 is set, the window generator 42 is set. Wind generator 42 makes it possible to determine the position of the sine wave zone, and this positioned sine wave is used to measure the point at which it passes through zero.

The observed frequency is also used for feedback, changing the frequency of the variable frequency oscillator 33. This is done in such a way that the variable frequency oscillator 33 follows thickness variations such that the amplitude of the signal detected by the receiving coil (receiving transducer) 11 is maximum.

The pulse train generator 34 sends a pulse train at a frequency determined by the PLL oscillator 33 to the amplifier 35 . The amplifier 35 converts this pulse train into a large current pulse, and sends this large current pulse to the transmitting coil (transmitting converter) 10.

The receiving coil 11 receives and receives signals propagating within the object to be measured. The mechanism of signal generation here is as described above.

The received signal is sent to a bandpass filter and amplifier 36. These signals are branched to logic and control circuit 1
5, and signal processing is performed in this logic and control circuit 15.

The total number of times through zero to be calculated is an item of information that must be entered into microprocessor 30 based on predetermined logic.

The elapsed time between the first and last time of crossing zero defines a time that is proportional to the thickness.

This time measurement is performed by setting a signal given from the logic and control circuit 15 and then counting pulses of a frequency of 200 MH2 or higher output from the signal generator 41.

The information output from the counter 38 is sent to a DA converter 40, which converts the signal into an analog signal. This analog signal is recorded on the graphic recorder 18 and visually displayed on the indicating device 17. It is also possible to obtain digital values, with which the entire thickness measuring device can be controlled and monitored on the basis of a microprocessor, logic programmer or computer.

[Effects of the Invention] As is clear from the above description, the present invention provides a thickness measuring device that can automatically and precisely measure the thickness of an object to be measured. The thickness measuring device according to the present invention uses a pancake-shaped transmitting coil to generate ultrasonic waves directly on the surface of the part to be measured through electromagnetic coupling, and measures the thickness of the part. This has the advantage that a transmission medium for transmitting the ultrasonic waves generated by the ultrasonic generator to the part to be measured is not required. Also, depending on the material being measured, the electromagnetic coupling efficiency may be small, but this point must be solved by appropriately designing the transmitter, transmission filter, and circuit configuration for amplifying and processing the signal obtained by the receiving coil. It is solved by

Since the magnetic field of the measuring device according to the invention is generated by a toroidal coil, it also has the advantage of having sufficient space for inserting and arranging an ultrasonic transducer.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of the thickness measuring device of the present invention. FIG. 2 is a block diagram showing a first preferred embodiment of the electric circuit of the thickness measuring device according to the present invention. FIG. 3a is a measurement diagram showing the measurement results obtained by the thickness measurement device according to the present invention, and FIG. 3b is a measurement diagram showing the measurement results obtained by the conventional thickness measurement device. FIG. 4 is a block diagram showing a second preferred embodiment of the electric circuit of the thickness measuring device according to the present invention. [Explanation of symbols] 1... Steel pipe 2... Annular coil 3... Shoe (ShO13> 12... Control circuit 13... Transmitter circuit 10... Transmitting coil 11... Receiving coil 14 ... Receiver circuit 15 ... Analog circuit 16 ... Digital circuit 17 ... Indication device 18 ... Graphic recorder 30 ... Microprocessor 32 ... Synchronous generator 33 ... PLL type Variable variable frequency oscillator 34/pulse train generator 31...scale verification circuit 37...envelope generator 36...bandpass filter and amplifier 24.42...window generator 25.38...force/interval 41 ... Signal generator 26.40 ... D-A converter 23 ... Pulse selection circuit 27 ... Pulse selection switch

Claims (13)

[Claims] (1) A thickness measuring device using ultrasonic waves having a coil for generating an electromagnetic field, a shoe, and a circuit related thereto, wherein the coil for generating an electromagnetic field is annular. and the associated circuitry has a control circuit, and the output of the control circuit is connected through a transmitter circuit to a transmitter coil attached to the shoe;
a receive coil is mounted within the shoe at a set distance from the transmit coil; the receive coil is connected to analog circuitry through a receiver circuit; and the analog circuit is associated with digital circuitry. the digital circuit is interconnected with the control circuit, the output of the analog circuit is connected to a measurement result indicating device, and the shoe is located at the center of the annular coil. The thickness measuring device using ultrasonic waves is characterized in that: (2) The thickness measuring device according to claim 1, wherein the transmitting coil and the receiving coil are pancake-shaped coils. (3) In claim 1, the control circuit includes a microprocessor, and the microprocessor includes a synchronous generator, a variable frequency oscillator, a pulse train generator, the receiver circuit, a scale verification circuit, and the digital circuit. the variable frequency oscillator is connected to the pulse train generator; and the output of the pulse train generator is connected to the transmitter circuit. . (4) The thickness measuring device according to claim 1, wherein the transmitter circuit is an amplifier. (5) In claims 1 and 3, the receiver circuit includes an envelope generator, and the envelope generator is connected to the microprocessor, bandpass filter, and amplifier circuit. , wherein inputs of the bandpass filter and amplifier circuit are connected to the receiving coil; and outputs of the bandpass filter and amplifier circuit are connected to the analog circuit. (6) The thickness measuring device according to claim 1, wherein the analog circuit includes a filter and a pulse shaping device. (7) In claims 1 and 3, the digital circuit includes a window generator, the window generator is connected to the synchronous generator, and the window generator is an AND a counter connected to the analog circuit, the microprocessor, the generator, the output of the AND gate, and the input of the D-A converter; The thickness measuring device is characterized in that an output of the device is connected to the measurement result indicating device. (8) The method according to claim 1, further comprising a synchronous generator connected to an input of a pulse train generator, and an output of the pulse train generator being connected to the transmitter circuit. Thickness measuring device. (9) The thickness measuring device according to claim 1, wherein the transmitter circuit is an amplifier. (10) The thickness measuring device according to claim 1, wherein the receiver circuit is an amplifier. (11) The thickness measuring device according to claim 1, wherein the analog circuit includes a filter and a pulse shaping device. (12) In claims 1 and 8,
the digital circuit has a pulse selection circuit;
The pulse selection circuit is connected to a pulse selection switch and a window generator, the window generator is connected to the period generator, and the window generator is connected to a D-A converter through a counter. and an output of the DA converter is connected to the measurement result indicating device. (13) The thickness measuring device according to claim 1, wherein the measurement result indicating device is at least one device from the group consisting of a milliammeter and a graphic recorder.