JPH03245001A - Magnetic detecting head and noncontact type range finder using same - Google Patents

Abstract

PURPOSE:To detect the distance to an object to be measured accurately by detecting alternating magnetic flux which is generated by a magnetizing coil covered with a core case for magnetic shielding by a magnetic sensor through the object to be measured. CONSTITUTION:The magnetic flux which is generated with a magnetizing coil 22 passes through a core case 11 for magnetic shielding and a central core member 12. The magnetic flux is outputted as the magnetic flux 24 through an opening 11a of the case 11. The flux is inputted into a free end 12a of the member 12 through the inside of a metal plate 8 and a magnetism sensor 13. The density of the magnetic flux passing the sensor 13 is changed in response to the change in distance l between the sensor 13 and the metal plate 8. A core 14 of the sensor 13 is excited to a saturat ing region beforehand. Therefore, when the outer magnetic flux is changed, positive and negative crest values Va and -Vb of the AC voltage generated in a detecting coil 15 are changed. Then, the crest values Va and -Vb are detected in a detecting circuit 19, and a difference value Vo is operated. In a distance computing circuit 20, the distance l corresponding to the detected voltage Vo is read out of a table wherein it is stored beforehand and outputted.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a magnetic detection head that uses a magnetic sensor to detect the magnetic flux density of magnetic flux that has passed through or passed through a measurement object, and a magnetic detection head that uses a magnetic sensor to detect the magnetic flux density of a magnetic flux that has passed through or passed through a measurement object. This invention relates to a non-contact distance meter that measures the distance to a non-contact distance.

[Prior Art] For example, when measuring the width, thickness, etc. of a product on-line while the product is being continuously conveyed on a conveyor roller in a factory production line, etc., and If it is not possible to directly touch the product with a measuring jig, use a non-contact distance meter to measure the distance to the product and check the product's cutting quality.

When the object to be measured is made of a metal material such as an F#4 plate, the non-contact distance meter has been developed to utilize eddy current. It is a schematic diagram showing the principle of determining dl of a non-contact distance meter.In other words, a cylindrical core 1 is attached to the tip of a measuring head, a detection coil 2 is wound around this core 1, and a detection coil 2 is wound around the core 1. A high-frequency current is applied from a high-frequency light output circuit (not shown) to generate an alternating magnetic field.When the magnetic flux 3 due to this alternating magnetic field crosses the steel plate 4 as the measurement target,
Eddy currents 5 are generated within the steel plate 4.

Since the magnitude of this eddy current 5 depends on the magnetic flux density of the magnetic flux 3 reaching this steel plate 4, it naturally changes depending on the distance g from the measuring head to the steel plate 4.

Then, the amount of change in this eddy current 5 is measured as the amount of change in impedance of the detection coil 2, and the distance ρ between the measurement head and the steel plate 4 is determined from this impedance value.

Note that the relationship between the impedance value and the distance g is not a linear relationship, so first calculate the relationship between each known distance and each impedance value, and convert the obtained impedance value to distance using a conversion table. do.

By utilizing eddy currents in this manner, the distance d111 from the measurement head to the object to be measured such as the steel plate 4 can be determined continuously without contact.

[Problems to be Solved by the Invention] However, the non-contact distance meter using eddy current as shown in FIG. 5 also has the following problem.

In other words, since the magnitude of the 54g eddy current 5 generated in the steel plate 4 is minute, the amount of change in the impedance value of the detection coil 2 corresponding to the amount of change in this eddy current 5 is even smaller. Therefore, in order to ensure measurement accuracy of a certain level or higher in distance g measurement, it is necessary to increase the outer diameter of the detection coil 2 and to set the measurement distance range (span) short. Generally, it is used under conditions that satisfy the following formula.

2D>fl Therefore, if the distance g to the measurement target is large or if it is necessary to use it in a large variation range (span), it is necessary to set the outer diameter of the detection coil 2 large.

As a result, the measurement throat becomes larger and the manufacturing cost increases.

In addition, if the measuring head becomes larger, it becomes impossible to measure in a narrow place, and the width of the steel plate 4 to be measured needs to be wider than the outer diameter of the measuring head, so conversely, the required minimum width of the measuring object becomes smaller. There is a problem in that it is only possible to measure the dimensions of a steel plate 4 that is wide and has a narrow width.

Furthermore, as described above, the change in the eddy current 5 that corresponds to a change in the distance p is small, and the amount of change in the impedance value of the detection coil 2 that corresponds to the amount of change in the eddy current 5 is even smaller, so external noise is reduced. Very easy to get into.

The present invention was made in view of these circumstances, and
By detecting the alternating current magnetic flux generated by the magnetizing coil covered by the magnetic shielding core case via the measurement target using a magnetic sensor, it is possible to accurately measure changes in magnetic flux that correspond to the distance between the magnetic sensor and the measurement target. The present invention aims to provide a magnetic detection head.

In addition, by using the magnetic detection head described above, a non-contact rangefinder can be created that can accurately measure the distance to a measurement target even if the measurement target is made of a metal material other than a magnetic material using a small magnetic detection head. The purpose is to provide.

[Means for Solving the Problems] In order to solve the above problems, the magnetic detection head of the present invention has the following features:
A magnetizing coil that generates alternating magnetic flux that passes through or passes through the measurement target made of a metal body, and a magnetization coil that is placed on the measurement target side within this magnetization coil to detect the density of the magnetic flux that passes through or passes through the measurement target. a core case for a magnetic shield made of a magnetic material that covers the outer peripheral surface of the magnetizing coil and has a bottomed cylindrical shape with an opening on the side facing the measurement target; The central core part +4 is connected to the bottom of the core case [2] 1, and the other end is formed at one end opposite to the opposite end of the magnetic sensor to be measured.

In the non-contact rangefinder of another invention, the magnetic detection head calculates the amount of encapsulation of the distance from the magnetic sensor to the object by calculating p from the amount of intersection of magnetic flux density detected by the magnetic sensor.
It is equipped with a distance p (1 path).

[Function] When the magnetic sensor configured as described above is installed, the central core portion is located at the central axis within the core case for the magnetic route, which is closed at one end. Then, when an alternating current is passed through the magnetized coil, an alternating magnetic field is generated, or this magnetized coil is attached to the core case for magnetic shielding.
In addition, since the central core member exists, the magnetic flux of the alternating magnetic field generated by the magnetization coil is sent out through the opening of the magnetic shielding core case in the direction of the measurement object, and if the measurement object is made of a magnetic material, Via this measurement target (bypass)
and input to the central core member via the magnetic sensor. In addition, if the measurement target is made of a metal other than a magnetic material, the magnetic flux passes through the measurement target in the outward direction and in the opposite direction, and passes through the magnetic sensor to the central core member. input.

Here, if the object to be measured is made of a magnetic material, if the distance from the magnetic sensor to the object changes, the
11 The number of magnetic fluxes passing through (bypassing) the constant object changes. If the number of magnetic fluxes passing through (bypassing) the measurement illusion changes, the density of magnetic flux passing through the magnetic sensor will naturally change as well. That is, in this magnetic detection head, the magnetic sensor detects the magnetic flux density corresponding to the distance to the measurement target.

On the other hand, if the object to be measured is made of a metal body other than a magnetic material, the magnetic flux sent out from the opening of the magnetic shielding core case in the direction of the object will pass through the object as it is. In this case, since the metal body is generally a good conductor and the magnetic flux is an alternating magnetic flux, the strength of the magnetic field fluctuates periodically. Therefore, when the magnetic flux passes through, this fluctuating magnetic field causes eddy currents to occur in the measurement object made of a metal body. When this eddy current flows within a constant object, a secondary magnetic field is generated by this eddy current. The secondary magnetic flux caused by this secondary magnetic field affects the magnetic flux density of the magnetic flux manually applied to the magnetic sensor. Since the eddy current changes in accordance with the magnetic flux density of the transmitted magnetic flux, as a result, when the distance from the magnetic sensor to the object to be measured changes, the magnetic flux density detected by the magnetic sensor changes. That is, the magnetic sensor detects the magnetic flux density corresponding to the distance to the measurement target.

However, in a non-contact distance meter that incorporates a magnetic detection head with such a configuration, the distance and magnetic flux density are determined in advance depending on whether the object to be measured is a magnetic material or a metal other than a magnetic material. By setting the relationship between the measured magnetic flux density and the measured magnetic flux density in a storage unit, for example, the distance to the measurement target can be determined from the measured magnetic flux density.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the overall configuration of a non-contact range finder according to an embodiment, and FIG. 2 is an external view showing a magnetic detection sensor used in this non-contact range finder. A non-contact distance meter can be broadly divided into two magnetic detection heads, which are arranged perpendicularly and facing each other with respect to the surface of a metal plate 8 to be measured, and which drive the magnetic detection head 9. Based on the signal, the distance to the metal plate 8 i1i! The control section 10 calculates R.

The magnetic detection head 9 is fixed to a frame of a building when the metal plate 8 to be measured is being transported, for example, on a transport roller. In the magnetic detection head 9, a central core member 12 made of the same material is integrally formed with the magnetic shielding core case 11 at the center of the bottom surface of the magnetic shielding core case 11 having a cylindrical shape with a bottom. ing. The magnetic shielding core case 11 is made of, for example, a magnetic material, and has a magnetic shielding function of preventing magnetic flux from leaking to the outside and preventing magnetic flux from being input from the outside. In addition, the central core member 12
shares the central axis with the magnetic shielding core case 11. A magnetic sensor 13 is supported by the magnetic shielding core case 1 by a support member (not shown) at a position facing the free end 12a of the central core member 12 in the χ·J direction.

The magnetic sensor 13 is made of a ferromagnetic material and includes a core 14 formed in a columnar shape, and a detection coil 15 wound around the core 4.
It is made up of. This detection coil 15 is provided with a drive signal generation circuit 16 provided in an external control section]0.
An alternating current excitation &i1 current having a predetermined frequency is supplied from the amplifiers 'J, 7JS and a fixed impedance 18. The core 4 of the magnetic sensor 13 is excited by the AC excitation current to a saturation region. Further, the terminal voltage of the fixed resistor 8 on the side of the magnetic sensor 13 is detected by one detection circuit and subjected to a voltage difference. Detection circuit] 9
The amplified detection voltage V output from. is converted into a distance in the next distance calculation circuit 20. The distance g outputted from the distance calculation circuit 20 is recorded on a recorder or displayed on a CRT display device or the like.

In addition, the core case 1 for magnetic shielding of the magnetic detection head 9
A magnetizing coil 22 wound around the outer peripheral surface of the coil bobbin 2 along the inner peripheral surface of the magnetic shield core case 1 is inserted into the core case 1. Then, an excitation current obtained by frequency-dividing the AC excitation current outputted from the drive signal generation circuit 6 by frequency division 2g23 is applied to the magnetizing coil 22.

Therefore, the magnetization coil 22 is connected to the magnetic IT sensor 13.
The detection coil 15 is excited at a frequency (1/N) lower than that of the detection coil 15.

Next, the operation of the non-contact type H[2 distance meter configured as described above will be explained.

First, a case where the metal plate 8 to be measured is made of a magnetic material such as a steel plate will be described with reference to FIG. Since the magnetizing coil 22 is arranged along the inner circumferential surface of the magnetic shielding core case 11, the magnetizing coil 22
The magnetic flux generated by the magnetic field passes through the inside of the magnetic shielding core case 11 and the central core member 12. Then, the opening 11a of the magnetic shielding core case 11
The magnetic flux 24 outputted from the magnetic flux 24 passes through (bypasses) the inside of the metal plate 8 made of a magnetic material, passes through the magnetic sensor 13, and is applied to the free end 12a of the central core member 12. That is, one end of the magnetizing coil 22, the magnetic shielding core case 11°, the opening of the magnetic shielding core case 11]a, the metal plate 8. Magnetic sensor 13. Central core member 1
2, the inside of the central core member 12d, the bottom of the magnetic shielding core case 11, and the magnetizing coil 2.
A kind of magnetic circuit is formed at the other end of 2.

In this magnetic circuit, the number of magnetic fluxes passing through the metal plate 8 naturally changes depending on the distance g from the magnetic sensor 13.

Therefore, the magnetic flux density passing through the magnetic sensor 13 changes according to a change in the distance M1 between the magnetic sensor 13 and the metal plate 8. Since the core 14 of the magnetic sensor 13 is excited to the saturation region in advance, when the external magnetic flux changes, the positive and negative peak values Va, ~v of the AC voltage generated in the detection coil 15 change.
b changes. Here, in the detection circuit 19, the positive and negative peak values Va, -Vb are detected and converted into DC values. And the difference value V.

(=Va-Vb) is settled. Therefore, the detection circuit 1
Detection voltage V sent from the source to the distance calculation circuit 20. teeth,
It will change in accordance with the change in the distance g.

The distance calculation circuit 20 includes each known distance ρ and each known detected voltage V measured in advance with respect to the magnetic material. It is stored in the form of a table. Then, the detection voltage V is output from the detection circuit 19. This detection voltage V is input. The distance g corresponding to is read out from the table and output.

Next, a case where the metal plate 8 to be measured is made of a good conductive material other than a magnetic material, such as aluminum material, will be explained with reference to FIG. 3.

That is, the opening 11a of the magnetic shielding core case 11
Since the metal plate 8 is made of a material other than magnetic material, the magnetic flux 24 outputted from the metal plate 8 passes through the metal plate 8 as it is. In this case, since the metal body 8 is a good conductor and the magnetic flux 24 is an alternating magnetic flux, the magnetic flux density of the magnetic field periodically fluctuates at a frequency set by the drive signal generation circuit 16 and the frequency divider 23. Therefore, when the magnetic flux 24 passes through the metal plate 8, an eddy current 25 is generated in the metal plate 8 due to the fluctuating magnetic field. When this eddy current 25 flows into the metal plate 8, a secondary magnetic field is generated by the eddy current 25, and a secondary magnetic flux 26 is generated by the secondary magnetic field.

This secondary magnetic flux 26 is the magnetic flux 2 manually applied to the magnetic sensor 13.
It affects the magnetic flux density of 4. Since the crystal current 25 changes in accordance with the magnetic flux density of the transmitted magnetic flux 24, as a result, when the distance from the magnetic sensor 13 to the metal plate 8 changes, the magnetic flux density detected by the magnetic sensor 13 changes. do. The magnetic flux density detected by the magnetic sensor 13 is detected by the detection circuit 19 at a voltage V as in the previous series. and sent to the distance calculation circuit 20.

In the distance calculation circuit 20, each known distance ρ and each known detected voltage V are stored in advance for a good conductor material as well as for a magnetic material. It is stored in the form of a table. Then, the detection voltage ■ is output from the detection circuit 19. When input, this detection voltage V. Read the distance corresponding to from the table and output it.

In the magnetic detection head 9 configured as described above and the non-contact distance meter using the magnetic detection head 9, the strength of the magnetic field generated by the magnetic detection head 9 is determined by the magnetization ability of the magnetization coil 22.

By increasing the excitation current flowing through the second magnetizing coil 22, a large magnetic field can be easily generated with a small volume. Therefore, the density of the magnetic flux 24 reaching the metal plate 8 facing the magnetic detection head 9 can be easily increased. Therefore, even if the distance ρ to the metal plate 8 is large, the density of the magnetic flux that passes through the metal plate 8 or passes through (bypass) the magnetic sensor 13 increases.

As a result, as the distance ρ changes, the magnetic flux passing through the magnetic sensor 13 also changes significantly. Therefore, even if the distance is large, small distance changes in the vicinity of the distance can be detected with high accuracy as magnetic flux density changes.

Next, the effect of covering the outside of the magnetic detection head 9 with the magnetic shielding core case 11 having the central core member 12 will be explained with reference to FIG.

FIG. 4(a) shows a case where the magnetic shielding core case 11 is not used at all. In this case, the magnetic flux 32 output from one magnetic pole of the magnetizer 31 made of an electromagnet or a permanent magnet
is input to the other magnetic pole of the magnetizer 31 via the magnetic sensor 34 through the measurement object 33 or through the magnetic sensor 34 . In this case, since the magnetizer 31 and the magnetic sensor 34 are open to the outside, magnetic flux is manually applied from the outside or magnetic flux is radiated to the outside. Therefore, the measurement accuracy of magnetic flux density is reduced and other external devices are adversely affected.

Further, as shown in FIG. 4(b), if only the magnetic shielding core case 11 is provided, a good magnetic shielding effect on the outside can be obtained. The number of magnetic fluxes 32 reaching the external measurement object 33 decreases. Therefore, of the magnetic flux passing through the magnetic sensor 34, the magnetic flux that has passed through or passed through the measurement object 33 is reduced. Therefore, the detection accuracy of magnetic flux density decreases.

On the other hand, as shown in FIG.
When the core case 11 for magnetic shielding is used, a magnetic circuit including this central core member 12 is formed, and the density of the magnetic flux output from the opening 11a of the core case 11 for magnetic shielding toward the metal plate 8 direction as the measurement target. becomes larger. Therefore, it is possible to exhibit a magnetic shielding effect against the outside and to improve the detection accuracy of magnetic flux density by the magnetic sensor 13.

Furthermore, by providing the core case 11 for magnetic shielding, the opening 1 of the core case 11 for magnetic/magnetic shielding is
Since the directivity of the magnetic flux 24 outputted from 1a to the metal plate 8 direction can be improved, the measurement area of the metal plate 8 to be measured can be reduced, and the measurement distance range (measurement span) can be expanded. . Moreover, the distance #1g between a very narrow area on the surface of the metal plate 8 and the magnetic sensor 13 can be measured, and for example, the influence of defects existing in other parts of the metal plate 8 or local thickness variations can be prematurely removed. .

In addition, since alternating magnetic flux is generated in the magnetizing coil 22, even if the object to be measured is made of a metal with good conductivity other than a magnetic material, the secondary magnetic flux 26 that changes in accordance with the distance ME can be 202/X' by detecting the change in the magnetic flux 26 using the magnetic sensor]'3. You can measure your own bag separation.

In this way, the distance to the target object can be measured with high accuracy, whether it is a metal object, magnetic object, or non-magnetic object. The range of applications can be greatly expanded.

[Effects of the Invention] As explained above, according to the magnetic detection head of the present invention,
The alternating current magnetic flux generated by the magnetizing coil covered by the magnetic shielding core case is detected by a magnetic sensor via the object to be measured. Therefore, it has a complete magnetic shielding effect against the external environment, and can increase the magnetic flux density applied to the measurement target, allowing the magnetic sensor to accurately measure changes in magnetic flux corresponding to the distance between the magnetic sensor and the measurement target. can.

In addition, in a non-contact rangefinder using a magnetic detection head with such a feature, an alternating magnetic flux is applied to the metal object to be measured by a magnetizing coil.
Even if the object to be measured is made of a metal material other than a magnetic material, the distance to the object to be measured can be accurately measured. In addition, sufficient measurement sensitivity can be ensured even if the magnetic detection/nod is made small.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the general configuration of a non-contact rangefinder according to an embodiment of the present invention, and FIG. 2 is a diagram showing a magnetic detection head according to an embodiment of the present invention incorporated in the rangefinder according to the embodiment. Fig. 3 is a diagram for explaining the operating principle of the magnetic detection head of the embodiment, Fig. 4 is a reference diagram for explaining the effect of the magnetic detection head of the embodiment, and Fig. 5 is a diagram of the conventional vortex. FIG. 2 is a diagram showing the operating principle of a non-contact distance meter that uses electric current. 8...Metal plate, 9...Magnetic detection head, 10...Control unit, 11. Core case for magnetic shielding, 12...Center core member, 13...Magnetic sensor, 14...Core, 1
5...Detection coil, 16...Drive signal generation circuit, 1
9...Detection circuit, 20...Distance calculation circuit, 22...
- Magnetizing coil, 24... magnetic flux, 26... secondary magnetic flux.

Claims (2)

[Claims] (1) A magnetizing coil that generates an alternating current magnetic flux that passes through or passes through the measurement object formed of a metal body, and a magnetization coil that is disposed at a position on the measurement object side within the magnetization coil and that passes through or passes through the measurement object. A magnetic sensor that detects the density of magnetic flux,
a magnetic shielding core case made of a magnetic material and having a bottomed cylindrical shape that covers the outer circumferential surface of the magnetizing coil and is open on the side facing the measurement object; and one end is inside the magnetic shielding core case. a central core member connected to the bottom of the magnetic sensor, the other end of which is formed at a free end facing the opposite end of the magnetic sensor to be measured. (2) A magnetizing coil that generates an alternating current magnetic flux that passes through or passes through the measurement object formed of a metal body, and a magnetization coil that is disposed at a position on the measurement object side within the magnetization coil and that passes through or passes through the measurement object. A magnetic sensor that detects the density of magnetic flux,
a magnetic shielding core case made of a magnetic material and having a bottomed cylindrical shape that covers the outer circumferential surface of the magnetizing coil and is open on the side facing the measurement object; and one end is inside the magnetic shielding core case. a central core member connected to the bottom of the magnetic sensor, the other end of which is formed at a free end facing the opposite end of the magnetic sensor to the measurement target; and the magnetic sensor measures the amount of change in distance from the magnetic sensor to the measurement target. A non-contact distance meter comprising a distance calculation circuit that calculates from the detected amount of change in the magnetic flux density.