JP3307170B2 - Flow velocity measuring method and its measuring device, continuous casting method and its device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method and a measuring device for measuring a surface velocity of a molten steel flow in a mold for casting molten steel in a continuous casting process, and a continuous casting method and a device therefor.
It relates to the location.

[0002]

2. Description of the Related Art In a continuous casting line, molten steel 3 is poured into a copper mold 4 from a tundish 1 through a nozzle 2 and cast as shown in FIG. The molten steel poured into the mold hits the mold wall and is divided into an upflow 7 and a downflow 8. The ascending flow produces flows 9a and 9b on the surface. If the left and right balance of the molten steel flow on the surface is lost, a vortex 11 is generated as shown in the figure, and the powder 5 scattered on the molten steel surface is involved. Further, if the molten steel flow on the surface becomes excessive, a part 10 of the powder on the molten steel surface is cut off as shown in the figure.

[0003] In any case, inclusions are trapped in the slab, which causes product defects. For this reason, stabilizing the flow of molten steel in a mold has become a very important issue, and in particular, it has been strongly required to continuously measure the flow velocity near the surface of molten steel.

[0004] Conventional measurement of the flow velocity near the surface of molten steel has been mainly of the contact type as described in, for example, Japanese Patent Application Laid-Open No. 5-60774. In this method, as shown in FIG. 45, a rod 12 made of fine ceramics is immersed in molten steel 14, and the pressure F applied to the rod by the flow of molten steel is detected by a pressure receiving sensor 13 to measure the flow velocity. However, in this method, since the ceramic rod is immersed in the molten steel at a high temperature, continuous measurement for a long time is impossible.

On the other hand, it is also known that the speed can be measured in a non-contact manner using magnetism. This is because when the conductor 15 moves in a uniform magnetic field as shown in FIG. 46, a velocity electromotive force of E = v × B is generated in the conductor, and the velocity electromotive force induces an eddy current Jv in the conductor. Then, an induced magnetic field Bv is generated on the conductor, and the original magnetic field is distorted from B to B 'so as to be dragged in the velocity direction of the conductor. Since the degree of this distortion changes according to the speed of the conductor, the speed of the target conductor can be measured by measuring the amount of distortion.

An apparatus for measuring the speed in a non-contact manner using such magnetism is described in Japanese Patent Application Laid-Open No. 2-31766. This is because, as shown in FIG. 47 (a), an alternating current is supplied to the primary coil 19 arranged in parallel with the flow of the molten steel 18 so that the alternating magnetic field 1 parallel to the molten steel surface is formed.
7 is applied to the molten steel surface, and two 2
The secondary coils 20a and 20b are arranged. Then, a magnetic field parallel to the target surface is detected by the secondary coils 20a and 20b.

In the detection operation by the secondary coils 20a and 20b, first, when the conductor is stationary, as shown in FIG. There is no difference between the electromotive forces of the next coils 20a and 20b, and the output becomes 0. When the conductor is moving, the magnetic field is distorted in the speed direction of the conductor due to the speed effect of the magnetic field and is not symmetrical with the excitation coil 19 interposed therebetween, as shown in FIG. Next coil 20a, 2
A difference occurs in the electromotive force generated at 0b, and a signal corresponding to the amount of distortion of the magnetic field, that is, the speed is obtained as the difference between the output voltages of the two secondary coils. Then, the secondary coils 20a, 20b
The speed of the conductor is determined based on the difference between the output voltages. Further, in the method of measuring the speed in a non-contact manner using magnetism, the speed sensitivity changes depending on the distance between the device and the object to be measured.
The distance between the apparatus and the object to be measured has been measured and corrected based on the output voltage of one of the secondary coils for detecting a magnetic field parallel to the object surface.

Another method for measuring the speed using magnetism is disclosed in Japanese Patent Application Laid-Open No. 61-223564. This is because, as shown in FIG. 48 (a), an E-shaped core and a winding made of an E-shaped core
Type magnetic field generator 21 is disposed such that the open ends of the magnetic poles face the conductor side and three magnetic poles 21a, 21b, 21c are parallel to the target surface, and a magnetic sensor 22 having a ring-shaped magnetic core Are arranged so as to surround the center magnetic pole 21c of the E-type magnetic field generator. A direct current is passed through the E-type magnetic field generator 21 so that adjacent magnetic poles generate magnetic fields in opposite directions. When the conductor 24 moves, an eddy current flows in the conductor due to the speed effect. The eddy current causes the center magnetic pole 21c and the left and right magnetic poles 21
a and 21b are generated between the magnetic poles N2 and S2 of opposite polarity. The horizontal component of the magnetic field generated from the electrode with respect to the target surface is detected by using the ring-shaped magnetic sensor 22 to detect the speed.

As another method for measuring the speed by using magnetism, there is one described in Japanese Patent Application Laid-Open No. Hei 5-297012. This is because, as shown in FIG. 49, the primary coil 151 is arranged perpendicular to the measurement object 152, an alternating current is applied to the primary coil 151, and the magnetic field 153 is applied.
And the secondary coils 154a and 154 are vertically arranged on both sides of the primary coil 151 with respect to the object 152 to be measured.
b, the primary coil 151, the secondary coil 154a,
It has iron cores 155, 156a, 156b wound with 154b. And the flow rate is the secondary coil 154
a, 154b were detected from the phase difference of the electromotive force generated. Such a velocity measuring method using magnetism can measure the velocity in a non-contact manner, and thus has been very promising because the velocity can be continuously measured for a long time even for a high-temperature liquid metal such as molten steel.

[0010]

However, the conventional non-contact velocity measuring method using magnetism has the following problems. 1. In the method of exciting the magnetic field in the horizontal direction, when the distance from the target is increased, the magnetic field is greatly attenuated, and the detection capability is reduced. In addition, the speed effect is maximized when a magnetic field is applied perpendicularly to the target, so that the efficiency is deteriorated. 2. In the method of detecting the horizontal magnetic field distortion, the magnetic field distortion is small and the speed sensitivity is low. 3. The detection sensitivity is low, and the sensitivity is insufficient for measuring a low flow velocity such as the flow velocity of molten steel in a continuous casting mold. 4. Due to thermal deformation of the magnetic field generator caused by a slight temperature change of the magnetic field generator, a pseudo signal is superimposed on a magnetic field distortion signal output from the magnetic sensor due to a temperature drift not corresponding to the speed. 5. In the method of detecting the distance between the device and the object to be measured by using the output voltage of one of the secondary coils for detecting the magnetic field parallel to the target surface and performing the correction, the distance accuracy is poor and the speed detection accuracy of the correction result is also poor. Would. 6. In the method of detecting the electromotive force generated in the secondary coil arranged parallel to the object to be measured and measuring the flow velocity by taking the voltage difference, the excitation magnetic field at the magnetic field detection point is large, and the velocity is Since the change due to the effect distortion is small, the voltage detection accuracy affects the flow velocity detection accuracy, and it is not possible to obtain sufficient detection accuracy. 7. In the method of measuring the flow velocity from the phase difference of the electromotive force generated in the secondary coil, it is difficult to improve the detection precision of the phase, and the detection precision affects the detection precision of the flow velocity, and a sufficient detection precision is obtained. Can not do. 8. When measuring a relatively small flow velocity in an environment with a large amount of disturbance magnetic field, such as continuous casting, the method that uses a DC excitation magnetic field and detects magnetic field distortion due to the velocity effect as a DC signal compared to the magnetic field distortion signal The disturbance magnetic field signal is large and accurate measurement cannot be performed. 9. When an object made of a magnetic material or a conductor approaches the side surface of the excitation / detection device, the zero level of the sensor changes due to the distortion of the excitation magnetic field, which makes it impossible to measure the flow velocity accurately. 10. If there is a strong disturbance magnetic field in the surroundings, even if the frequency of the excitation / detection magnetic field is measured away from the disturbance magnetic field, the effect cannot be sufficiently removed, resulting in noise, and the measurement accuracy is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. The present invention provides a method of controlling the flow velocity of a high-temperature object such as a molten metal at a position distant from the object even in an environment with a large disturbance. without the influence of the change, and also to changes in distance to the target surface, a very high sensitivity and stable, non-contact continuously detecting a flow rate measuring method and the measuring apparatus can be, parallel
And continuous casting method using its flow velocity measurement method and the like
For the purpose of Rukoto obtain the equipment.

[0012]

According to a first aspect of the present invention, there is provided a flow velocity measuring method, comprising: a magnetic field generating means having at least three magnetic poles.
By generating a magnetic field perpendicular to the moving conductive measurement object, at least the magnetic pole of the center
Two detectors installed between the magnetic poles at both ends
Thus , at least two magnetic field components perpendicular to the measurement target object are provided at different positions in the movement direction of the measurement target object,
In addition, the flow velocity of the object to be measured is calculated based on a differential signal of at least two magnetic fields detected at a position where the magnetic field is a target and detected at a position where the magnetic field is symmetric. A flow velocity measuring method according to a second invention is the method according to the first invention, wherein an AC magnetic field is used as an exciting magnetic field, and only a component having a specific phase at the same frequency as the exciting magnetic field is detected in a difference signal of the detected magnetic field. Based on the detected signal, the flow velocity of the object to be measured is calculated. The flow velocity measuring method according to the third aspect of the present invention provides a method for measuring a moving conductive object to be measured, via a conductive non-magnetic shield plate.
A magnetic field having two frequency components perpendicular to each other is generated, and at least two magnetic field components perpendicular to the object to be measured are separated by two frequencies at different positions in the moving direction of the object to be measured and at positions where the magnetic field is symmetric. The flow velocity of the object to be measured is calculated based on a difference signal of at least two magnetic fields, which is detected for each component and is detected for each of two frequency components at a position where the magnetic field is symmetric. A flow velocity measuring method according to a fourth invention is the method according to the first, second or third invention, wherein a distance between a detection position of the magnetic field component and the object to be measured is detected, and the detected magnetic field is determined based on the distance. The component is corrected.

[0013] flow rate measuring apparatus according to the fifth invention, less
Both have three poles, and magnetic field generating means for generating a magnetic field perpendicular to the measured object conductive moving, small
At least the position of the magnetic pole between the center magnetic pole and the magnetic poles at both ends.
At least two detecting means for detecting a magnetic field component perpendicular to the object to be measured at different positions in the moving direction of the object to be measured and at a position where the magnetic field is symmetrical; And a measuring means for calculating the flow velocity of the object to be measured based on a difference signal of at least two magnetic fields detected by the detecting means. According to a sixth aspect of the present invention, in the flow velocity measuring apparatus according to the fifth aspect, an AC exciting current is supplied to the magnetic field generating means to generate an AC magnetic field. Only a component having a specific phase in frequency is detected, and the flow velocity of the measurement object is calculated based on the detected signal.

According to a seventh aspect of the present invention, the flow velocity measuring device according to the fifth or sixth aspect, further comprises a correction means for measuring a temperature distribution of the magnetic field generating means and correcting a flow velocity value of the measurement object. According to an eighth aspect of the present invention, in the flow velocity measuring apparatus according to the fifth, sixth or seventh aspect, the magnetic field generating means and the detecting means are provided in a cooling means having at least a bottom surface made of a non-magnetic non-conductor. is there.

According to a ninth aspect of the present invention, there is provided a flow velocity measuring device comprising:
In the sixth, seventh or eighth invention, the detection means is fixed to at least magnetic poles at both ends. A flow velocity measuring apparatus according to a tenth aspect of the present invention is the flow velocity measuring apparatus according to the fifth, sixth, seventh, eighth or ninth aspect, wherein the magnetic field generating means and the detecting means cover the magnetic field generating means and the detecting means except for a portion facing the object to be measured. It has a shield box. According to an eleventh aspect of the present invention, there is provided the flow velocity measuring apparatus according to the fifth, sixth, seventh, eighth, ninth or tenth aspect , wherein the magnetic field generating means and the conductive means inserted between the detecting means and the object to be measured. The measuring means further supplies an exciting current having two frequencies to the magnetic field generating means, and separates the magnetic field component detected by the detecting means into two frequency components. , Based on the magnetic field components divided for each of the two frequency components.

According to a twelfth aspect of the present invention, there is provided a flow velocity measuring apparatus according to the fifth, sixth, seventh, eighth, ninth, tenth or eleventh aspect , wherein the distance between the detecting means and the object to be measured is determined. A distance detecting means for detecting, and the measuring means further comprises:
The magnetic field component is corrected based on the distance detected by the distance detecting means. The flow velocity measuring device according to the thirteenth invention is directed to a fifth, sixth, seventh, eighth, ninth, tenth, eleventh or eleventh embodiment.
In the twelfth aspect , the magnetic field generating means has at least two magnetic poles arranged in parallel with the object to be measured, and generates a magnetic field perpendicular to the object to be measured and in a direction opposite to that of the magnetic pole adjacent to the object by the exciting current. To be generated. The continuous casting method according to a fourteenth aspect of the present invention provides a continuous casting method in which a molten steel is poured from a tundish into a mold, and the flow rate of the molten steel poured into the mold is measured by a flow rate measurement method according to any one of the first to fourth aspects. A measuring step of measuring and monitoring the flow rate by the method or any one of the fifth to thirteenth inventions, and a control step of controlling the flow velocity monitored in the measuring step to stabilize the flow. And a casting step of performing continuous casting from a mold. A continuous casting apparatus according to a fifteenth aspect of the present invention is directed to a tundish into which molten steel is poured, a mold into which molten steel is poured from the tundish, a mold for performing continuous casting, and a fifth invention to measure and monitor the flow rate of the molten steel poured into the mold. first
According to a third aspect of the present invention, there is provided a flow rate measuring device, and control means for controlling a flow rate monitored by the flow rate measuring device to stabilize the flow.

[0017]

According to the present invention, a magnetic field is excited perpendicularly to an object to be measured, and a magnetic field component perpendicular to the target surface is detected to measure the flow velocity of the surface of the molten steel flow in the mold.
The operation will be described in the following (a) to (f).

(A) Excitation method The operation principle of the present invention will be described based on the embodiment of FIG.
In the present invention, as shown in FIG. 1, the magnetic poles are excited by the magnetic field generator 28 so that the directions of the adjacent magnetic poles are opposite to each other and the magnetic field is perpendicular to the surface of the conductor 29 to be measured. The two magnetic sensors 26a and 26b are disposed between the magnetic pole 25c and the magnetic pole 25a and between the magnetic pole 25c and the magnetic pole 25b. These magnetic sensors 26a and 26b are arranged to detect a magnetic field component in a direction perpendicular to the conductor surface. Note that the entirety of the magnetic sensors 26a and 26b and the magnetic field generator 28 is referred to as a sensor head 200.

As described above, by directing one or more magnetic poles toward the conductor surface, a magnetic field can be excited perpendicular to the conductor surface. As described above, since the velocity effect is represented by v × B, the velocity effect is maximized when the velocity of the target and the magnetic field are perpendicular. Here, since the speed to be measured is parallel to the target surface, if the magnetic field is excited perpendicularly to the target surface, the speed effect will be greater and the speed detection sensitivity will be greater than when the magnetic field is excited horizontally.

If a magnetic field generator having two or more magnetic poles is used to excite adjacent magnetic poles so as to generate magnetic fields in opposite directions, the magnetic field concentrates between the magnetic poles, so that the magnetic field is excited in the lateral direction. The spread of the magnetic field is suppressed as compared with the case where it is, and even when the distance between the sensor and the object is large, the magnetic field can be effectively excited in the object.

(B) Detection method As shown in FIG. 2A, when the conductor 29 is stopped, the magnetic field is symmetrical about the center magnetic pole. Therefore, when the conductor moves, as shown in FIG. 2B, the magnetic field is distorted by the eddy current generated in the conductor corresponding to the speed, and the magnetic field at the position of each magnetic sensor is distorted. Output changes. The change of the output of each magnetic sensor will be described in more detail with reference to FIGS. 3 (a) and 3 (b). FIG. 3A shows the amount of distortion of the magnetic field when the speed of the conductor is low. The amount of distortion plots the difference in the magnetic field distribution between the magnetic poles when the object is stopped and when the object is moving. It was done. 3A shows the distortion amount of the magnetic field component perpendicular to the conductor surface, and FIG. 3B shows the distortion amount of the magnetic field component horizontal to the conductor surface. As can be seen from FIGS. 3A and 3B, for the same speed, the vertical component of the magnetic field has a larger amount of change due to distortion than the horizontal component.

The change in the vertical magnetic field component due to the distortion of the magnetic field increases between the center position of the center magnetic pole and the magnetic poles at both ends and near the magnetic poles at both ends. Therefore, as in the present invention, if the magnetic sensors 26a and 26b are arranged at positions from the center of the center magnetic pole and the magnetic poles at both ends to the magnetic poles at both ends, and a magnetic field component perpendicular to the target surface is detected, the change in the magnetic field due to the distortion is obtained. Can be caught most efficiently, and speed measurement with excellent detection sensitivity can be performed.

Also, as shown in FIG. 2B, the directions of the distortion are opposite at the positions of the two magnetic sensors 26a and 26b, respectively, and the disturbance noise and the direct magnetic field from the magnetic field generator are the two magnetic sensors. Since the position is in the same direction, by taking the difference between the outputs of the two magnetic sensors, only the extra signal can be excluded, and only the distortion amount corresponding to the speed can be further reduced by S /
N can be detected well. Also, an AC exciting current is supplied to the magnetic field generator to generate an AC magnetic field, and a phase detector or the like is used to detect a component of a specific phase at the same frequency as the exciting magnetic field in the differential signal of the detected magnetic field. If only the frequency is detected, if the frequency of the disturbance magnetic field is small as the excitation frequency, the influence of the disturbance magnetic field can be reduced, and the flow velocity can be measured accurately. Here, when the detection phase is excited at a low frequency, the amount of distortion is proportional to v × B and may be the same as the excitation magnetic field, that is, the excitation current. However, when the frequency is high, the phase of the magnetic field in the measurement object is -dB / d
Since it changes due to the eddy current proportional to t, it is necessary to select a phase at which the magnetic field distortion signal due to the speed becomes maximum for each frequency. When a pickup coil is used as the magnetic sensor, the magnetic field and the output voltage of the coil are-
Since there is a 90 ° phase difference, the excitation current and -9
Attention must be paid to the component that is shifted by 0 °.

(C) Measurement-resistant environment In an environment where there is only a disturbance of about the earth magnetism, such as when measuring the flow velocity of molten steel in a continuous casting machine without an electromagnetic stirrer, a magnetic core composed of a magnetic core and a winding is used as a magnetic field generator. By using a type coil and a magnetic sensor having a magnetic core, high-speed measurement can be performed. On the other hand, in an environment with a large disturbance magnetic field, such as a continuous casting facility with a device that generates a large magnetic field such as an electromagnetic stirrer, an air-core coil consisting of only windings is used as a magnetic field generator. Further, an air-core coil having only windings as shown in FIG. 33 to be described later is used as a magnetic sensor. Further, the exciting current of the magnetic field generator is set to an alternating current, and its frequency avoids a frequency with a large disturbance magnetic field, such as the frequency of an electromagnetic stirrer. Furthermore, after passing the output of the air-core coil through a band-pass filter with the frequency of the magnetic field generator as the center frequency,
By inputting the signal to the synchronous detector or the phase detector, the disturbance velocity signal can be excluded and the flow velocity can be measured with high accuracy even under a high disturbance magnetic field. In addition, as can be seen from the apparatus configuration example in FIG.
In general, the magnetic core used for the magnetic field generator and the magnetic core used for the magnetic sensor are larger in the magnetic core of the generator, so that the magnetic core of the magnetic sensor is more likely to be magnetically saturated even with a smaller disturbance magnetic field. Therefore, if the magnetic field from the electromagnetic stirrer is small and the magnetic core of the generator is still at a level that does not cause magnetic saturation, the magnetic sensor alone may be an air-core coil without using the magnetic field generator as an air-core. In this way, the magnetic core can be used for excitation, so that the excitation magnetic field can be generated efficiently with a smaller number of turns than when the magnetic field is generated only with the air-core coil.

By the way, such a flow velocity measuring apparatus using a magnetic field detects the amount of distortion caused by the velocity effect of the exciting magnetic field to measure the flow velocity. Therefore, for example, as shown in FIG. When the magnetic body 31 approaches, the excitation magnetic field is distorted, and the signal changes even if the flow velocity does not change (hereinafter, referred to as a pseudo signal). This is because the exciting magnetic field does not flow only in the target direction but leaks slightly to the side surface. This phenomenon is the same not only when the approaching object is a magnetic substance but also when it is conductive or when there is a large disturbance magnetic field around it. Hereinafter, these are collectively referred to simply as disturbance. In the actual continuous casting process, such disturbances include a mold, a mold cover, a tundish, and a magnetic field caused by electromagnetic stirring.

The distortion of the exciting magnetic field due to such a disturbance is 2
If the two detector positions are the same, the difference between the two detectors is obtained, so that this disturbance can be canceled. However, FIG.
As shown in (a), for example, when a magnetic body approaches a location closer to one of the detection devices, the distortion of the magnetic field due to disturbance at two locations differs, and a pseudo signal remains even if the difference is obtained.

Therefore, as shown in FIG.
Is surrounded by a shield box 32 made of a magnetic material having only the surface facing the measurement object opened. Here, FIG. 5A is a view of the shield box 32 and the sensor head 200 as viewed from above, and FIG. 5B is a view as viewed from below. In this way, as shown in FIG. 4B, the exciting magnetic field does not leak to the side surface, flows only in the measurement target direction, and the magnetic body 31
The excitation magnetic field will not be distorted even if the distance approaches. In addition, even when there is a magnetic field outside, the magnetic field flows through the inside of the shield wall, so that the magnetic field does not affect the sensor head.

As the material of the shield box 32, it is necessary to select a magnetic material having a small coercive force, such as pure iron or permalloy, so that the shield itself does not affect the measurement as a magnet. In addition, here, as shown in FIG. 5, the shield box 32 surrounds all surfaces except the bottom surface facing the measurement object, but the cause of the disturbance is that the sensor head 200 has a side surface perpendicular to the arrangement of the two detection devices. If it is in the direction, as shown in FIG. 6, a U-shaped shield consisting of only two side surfaces and a top surface is applied. If the cause of the disturbance is in the side direction parallel to the arrangement of the two detection devices with respect to the sensor head 200, it is sufficient to provide a U-shaped shield consisting of only the two side surfaces and the top surface as shown in FIG. is there. By surrounding the sensor head 200 with the shield box 32 in this manner, it is possible to accurately measure the flow velocity even in a place where there are many disturbances. (D) Method for Improving Cooling Ability To detect the flow velocity of a high-temperature conductor, the temperature of the device changes. At this time, even if the sensor head is cooled, the temperature of the sensor head in the air-cooled chassis slightly changes. Then, when a magnetic core is used as the magnetic field generator 28 of the sensor head 200 as shown in FIG. 8A, the magnetic core thermally expands or contracts (48).
Even when an air-core coil is used, if there is a temperature change, the windings thermally expand and contract.

When the position of each magnetic pole changes due to the thermal expansion and contraction, the magnetic field at the position of the magnetic sensor changes unless the position of the magnetic sensor changes. As a result, the output of the magnetic sensor 26b on one side changes, and a pseudo signal is generated even when the conductor is not moving. This pseudo signal is a drift signal that increases or decreases as the temperature rises or falls.

In order to suppress such a temperature drift, it is necessary to have a structure capable of minimizing a change in the position between the excitation and detection devices due to thermal deformation when the temperature of the device changes. For this purpose, as shown in FIG. 8B, the magnetic sensors 26a and 26b are fixed to the magnetic poles 25a and 25b at both ends. In this way, even if the magnetic pole expands significantly due to thermal expansion, the magnetic sensor also moves with the magnetic pole,
The magnetic field at the position of the magnetic sensor does not change much compared to before the expansion. Thus, if the magnetic sensor is fixed to the magnetic poles at both ends, the magnetic sensor is fixed separately from the magnetic field generator,
Temperature drift can be suppressed. When the temperature change is small, the magnetic sensor need not be fixed, but may be located between the center of the center magnetic pole and the magnetic poles at both ends and between the magnetic poles at both ends. However, when there is a temperature difference in the sensor head even when the magnetic sensor is fixed, for example, when the temperature differs between the left and right legs, FIG.
As shown in (c), the thermal deformation is not uniform on the left and right (48a ≠
48b), a temperature drift remains. Therefore, in the present invention, the following features are given to the cooling means so that the temperature of the sensor head can be kept uniform even when the ambient temperature changes.

First, as shown in FIG.
The bottom and side walls of 9 are doubled, and cooling air flows between the double walls. By doing so, a convection layer of air is formed between the sensor head and the surroundings, and a change in the surrounding temperature can be absorbed by the air flowing therethrough. Further, the inner wall of the cooling chassis close to the sensor head is uniformly cooled by the flow of the air, so that it is possible to prevent the inner wall from locally changing the temperature and transmitting it locally to the sensor head.

Second, as shown in FIG. 10B, the sensor head is set so as not to directly touch the bottom and side surfaces of the cooling chassis 49. The direct cooling chassis 4 as shown in FIG.
9, heat is transmitted from the cooling chassis 49 to the sensor head 200 through the contact surface, and the temperature of the sensor head 200 becomes locally uneven at the contact surface.

Third, as shown in FIG. 11B, the sensor head 200 is cooled by convection inside the chassis without directly applying cooling air to the sensor head 200. If the cooling air is directly applied to the sensor head to cool it, the surface hit by the air is locally cooled, and the temperature of the sensor head becomes uneven. Further, when the material of the cooling chassis 49 is conductive, the conductivity of the chassis greatly changes due to a change in ambient temperature, which affects the output signal of the device. Therefore, the chassis forms all or at least the bottom surface facing the target through which the magnetic field from the sensor head passes, using a nonconductor.

By increasing the cooling capacity, the sensor head 200
If the temperature of the cooling air supplied to the cooling chassis changes due to a change in room temperature even if the temperature of the sensor head is kept constant, the temperature of the sensor head also changes and the temperature in the sensor head becomes non-uniform. . Therefore, in the present invention, as shown in FIG. 12 of an embodiment to be described later, the cooling air is passed through a control device 301 that keeps the temperature constant, and then blown into the cooling chassis, so that the cooling air is changed due to a change in air temperature or the like. The effect of temperature change was reduced.

Further, in the present invention, as a method of suppressing a temperature change, a cooling chassis is installed in a high-temperature measuring temperature environment without flowing cooling air in advance, and a temperature rise in the chassis is measured. A method of setting the cooling temperature to that temperature is used. By doing so, the temperature becomes the same as the surrounding environment from the beginning, so that there is no change in the temperature of the sensor head in the cooling chassis, and the temperature drift can be suppressed. This method is effective when the temperature rise of the sensor head due to the surroundings is relatively low at about 100 ° C. or less. Also, the temperature rise of the sensor head due to
If the temperature of the cooling air is set relatively high even at 0 ° C. or higher, the difference from the ambient temperature can be reduced, and the temperature non-uniformity of the sensor head can be suppressed.

(E) Correction of Temperature Drift Even if the cooling capacity is improved or the cooling air is controlled, the temperature of the sensor head is slightly unbalanced due to the change of the ambient temperature, and the temperature drift slightly remains. . Therefore,
In the first method of the present invention, the non-uniformity of the temperature is measured, and the remaining drift is corrected by an arithmetic processing. Here, a speed measuring device having a configuration as shown in FIG. 12 will be described as an example. As shown in FIG. 12, the temperatures of the target positions of the legs at both ends of the magnetic core 25 are measured using thermocouples 315, 316 and the like. FIG. 13 shows the temperature difference between the two points and the state of the output signal of the current meter. As can be seen from this figure, there is a correlation between the temperature difference between the two legs (FIG. 13C) and the temperature drift of the signal (FIG. 13A), and it can be seen that the temperature drift can be corrected from the information on the temperature difference.

FIG. 12 shows an example of the correction circuit 304 for that purpose. After taking the difference between the temperature signals from the thermocouples 315 and 316 at both ends of the magnetic core 25, the temperature signals are multiplied by a coefficient for correction through an amplifier 313 and subtracted from the signal of the flow velocity. Here, the magnification of the amplifier, that is, the correction coefficient, is determined by performing a heating test offline for the entire apparatus including the magnetic field generator and the cooling chassis.

Next, a temperature drift correction method according to the second method of the present invention will be described. This is because the magnetic field generator is excited by a current having two frequencies, a shield plate is inserted between the magnetic field generator and the object to be measured, and the two frequency components of the magnetic field distortion signal are detected and calculated. This excludes the temperature drift that has occurred (see FIG. 28).
reference). This principle will be described with reference to FIGS.

FIG. 29 shows changes in the speed sensitivity of the speed measuring device when the excitation frequency is changed.
It is expressed as a specific output with the speed sensitivity at 0 [Hz] as 1.
Here, the speed sensitivity is the magnitude of the magnetic field distortion signal for a speed of 1 m / sec. As shown in FIG. 29, the speed sensitivity is attenuated by the eddy current generated in the shield plate, and greatly decreases as the frequency is increased.

FIG. 30 shows that the temperature of the magnetic field generator is 1 ° C.
The amount of change in the output signal of one magnetic sensor when the excitation frequency was changed was measured by changing the excitation frequency.
The output signal of [Hz] is expressed as a specific output with 1 being set. As shown in FIG. 30, the change in the signal due to the temperature change is constant regardless of the excitation frequency. The actual temperature drift is
The difference between the magnetic field changes at the two magnetic sensors located at both ends due to thermal deformation of the magnetic poles at both ends is shown in FIG. 30. As is clear from FIG. It is considered that the difference between the outputs of the two magnetic sensors is constant regardless of the frequency.

Therefore, the magnetic field generator is excited by an exciting current having a waveform obtained by superimposing a sine wave of two frequencies of a low frequency of about 1 to 1000 Hz and a high frequency higher than the low frequency in the range of 1 to 1000 Hz. . In addition, a shield plate is inserted between the magnetic field generator and the object to be measured, and the output signal of the magnetic sensor is detected, divided into two frequency components, and the difference is obtained. The difference signal of the two frequencies is obtained by adding the difference of the distortion of the magnetic field due to the speed effect of the two frequency components and the difference of the temperature drift of the two frequency components.
Here, the distortion of the magnetic field due to the speed effect is significantly different between a low frequency and a high frequency. On the other hand, since the temperature drift is the same at the two frequencies, it disappears when the difference between the two frequency components is taken. In this way, by exciting at two frequencies and detecting and calculating the components of each frequency of the magnetic field distortion due to the speed effect, only the temperature drift can be excluded and only the magnetic field distortion signal corresponding to the speed can be obtained. Note that the phase at the time of detection here is due to the eddy current generated in the shield plate, and the phase of the magnetic field in the measurement object changes at high frequencies as well as at low frequencies. Different phases must be selected.

(F) Lift-off correction When the distance between the sensor head and the object to be measured changes, the speed sensitivity also changes.
The distance to the target surface is measured with a high-accuracy feedback amplification type eddy current rangefinder, and the output signal after removing the temperature drift from the magnetic field distortion signal of the magnetic sensor output is calculated based on this distance signal to determine the speed sensitivity. to correct.

Here, the principle of the lift-off correction will be described with reference to FIG. 14, FIG. 15, and FIG. FIG. 14 shows a change in speed sensitivity of the speedometer when the distance between the sensor seed and the target surface is changed. As shown in FIG. 14, the distance l to the target surface and the speed sensitivity G have the following relationship. G = A · e− ^{B · l} Therefore, assuming that the magnetic field distortion signal according to the present invention when the distance is 1 is S (l), the speed v of the target at that time can be calculated by the following equation. v = S (l) / (A · e− ^{B · l} ) = A ′ · S (l) ·
e ^{B · l} (where A and B are constants, A ′ = 1 / A)

This equation is, for example, as shown in FIG.
Excitation / detection circuit 50 and drive / detection circuit 5 for eddy current distance meter
1. A correction circuit including an amplifier 52 having exponential characteristics, a multiplier 54, and a linear amplifier 53 can be realized. As shown in FIG. 16, an eddy current distance meter 56 is provided in front of the magnetic pole 25c at the center of the magnetic field generator 28. And
The distance 1 to the target surface is detected by the eddy current distance meter 56 and the drive / detection circuit 51. The detected distance signal 58 is applied to an exponential amplifier 52 to calculate an exponent e ^{B · l} .

Further, the multiplier 54 excites the speedometer
After multiplying by the speed detection signal 57 output from the detection circuit 50, the gain is multiplied by a constant by the linear amplifier 53 having a variable gain. Thus, the speed can always be measured with a constant speed sensitivity even if the distance changes. Although the correction equation is realized by the circuit here, the output of the speedometer and the output signal of the eddy current distance meter may be A / D converted, and thereafter, the calculation of the correction equation may be performed by software.

Here, since the coefficient B of the exponential function varies depending on the shape of the magnetic field generator, it is necessary to measure the distance-speed sensitivity curve with respect to the target surface as shown in FIG. 14 in advance. The proportionality constant A, that is, the gain of the linear amplifier 73 can be adjusted in advance by using a speed signal measured by another method such as a method of dipping a rod described in Japanese Patent Application Laid-Open No. 5-60774. Just fine.

[0047]

【Example】

Embodiment 1 FIG. FIG. 1 is a front view showing the appearance of a sensor head of a velocity measuring device according to one embodiment of the present invention. FIG. 16 is a perspective view showing the appearance of a sensor head to which an eddy current rangefinder is attached.
FIG. 9 is an explanatory diagram when a sensor head is arranged in an air-cooled box, and FIG. 12 is a block diagram showing a configuration of a measuring circuit of the speed measuring device of this embodiment. Here, as the velocity measuring device, the magnetic field generator 28 and the magnetic sensors 26a and 26b which are the basis of velocity measurement as shown in FIG. , An air-cooling box 49 for measurement in a high-temperature environment as shown in FIG. 9, and a temperature control device 301 for controlling the temperature of cooling air supplied to the air-cooled chassis.

The magnetic field generator 28 of this embodiment has a magnetic core type exciting coil using a magnetic material. As shown in FIG. 1, an E-shaped magnetic core 25 made of a magnetic material and windings 27a, 27b, 2
7c. Here, when measuring the velocity under a normal environment, any magnetic core can be used as long as it can excite a large magnetic field to some extent. For example, a magnetic core laminated with 3% silicon steel sheet can be used. However, in a high-temperature measurement environment, in order to suppress thermal deformation of the magnetic core due to a temperature change, it is better to use an integrated core such as a ferrite core than to use a laminated magnetic core.

As shown in FIG. 1, two magnetic sensors 26a, 26b using a magnetic core are provided inside magnetic poles 25a, 25b at both ends of a magnetic field generator 28, as shown in FIG.
Are arranged to detect a component of a magnetic field in a direction perpendicular to the conductor surface. Here, the magnetic sensor is fixed to the magnetic poles at both ends of the magnetic field generator in order to suppress temperature drift. When the temperature change is small, the center magnetic pole may be located between the magnetic poles at both ends from the center of the magnetic poles at both ends without fixing the magnetic sensor. Here, as the magnetic sensor, a magnetic measuring device using a magnetic core as shown in JP-A-1-308982 was used. Thermocouples 315 and 316 are attached to the legs at both ends of the E-shaped magnetic core of the sensor head as shown in FIG. Further, an eddy current meter 56 is disposed in front of the magnetic pole 25c at the center of the magnetic field generator 28 as shown in FIG. Here, a differential feedback type eddy current distance meter as shown in Japanese Patent Publication No. Sho 62-30562 is used as the eddy current distance meter 56. According to this, high-precision distance measurement becomes possible even if the distance becomes large.

When measuring the speed in a high temperature environment, a magnetic field generator, a magnetic sensor, and an eddy current meter are arranged in an air-cooled box 49 as shown in FIG.
00 is cooled evenly. This air-cooled box 49
Sensor head 20 composed of an outer box and an inner box made of ceramics
10 is suspended from the upper lid of the cooling chassis by the member 321 as shown in FIG. 10B, and does not contact the bottom surface of the inner box. This is because when measuring the flow velocity on the surface of the molten steel flow in the mold that casts molten steel in the continuous casting process, heat radiation from the lower surface of the device is dominant, and the temperature of the bottom of both the outer box and the inner box is the highest. Because it changes, the sensor
This is because when 0 is in contact, heat is directly transmitted to the sensor head 200 from the contact surface. There is a space between the outer box 59a and the inner box 59b as shown in FIG. 9, and a cooling air is blown from one side and discharged from the other side to form an air layer between the outer box and the inner box. Absorb the temperature change of the outside environment with
Do not pass through the inner box 59b.

In the inner box 59b, as shown in FIG.
There are air blowing ports 55a, b, c and d. Although FIG. 9 shows only the front side blow-out port, there are actually four blow-down ports on the opposite surface and at the same position. Each air hole is arranged so that cooling air does not directly hit the E-shaped sensor head. Air is blown into the inner box from the blowing port to create a flow of air around the sensor head, thereby cooling the sensor head.

The cooling air blown between the inner and outer boxes and into the inner box is first passed through a temperature control device 301 as shown in FIG. As a temperature control device, for example, an electric heater 306 or the like is applied to the air piping,
With reference to the value of the thermometer 314 attached near the air inlet in the cooling chassis 49, if the value is lower than the set value,
This can be achieved by using a control device that moves the heater and turns off the heater if it is expensive.

As a measurement circuit, a circuit for one frequency shown in FIG. 31 is used as shown in FIG. This is because drift calibration using two frequencies is not performed here. This measurement circuit includes an excitation circuit 302, a detection circuit 303, a temperature drift correction circuit 304, and a lift-off correction circuit 97. First, the excitation circuit 302 includes the excitation windings 27a, 27
A current is passed through b and 27c to excite a magnetic field in the object to be measured.
It comprises an oscillator 309 and a constant current amplifier 310.
An oscillator generates a sine wave of 1 to 1000 Hz and sends an exciting current to an exciting coil via a constant current amplifier 310. The excitation coils 27a, 27b, and 27c are set so that the excitation currents flow so that the adjacent excitations have a phase difference of 180 ° and the magnetic poles adjacent to each other have the opposite direction at each moment. Has become. Here, if the excitation frequency is too high (about 1 kHz or more)
The eddy current generated in the measurement object increases, the property of the eddy current distance meter becomes stronger than that of the velocimeter, and the noise due to the waving of the surface of the object increases. On the other hand, if the frequency is too low (about 1 Hz or less), the electromotive force generated in the detection coil is weakened, and the detection sensitivity is reduced. Therefore, the excitation frequency was set to 14 Hz here.

The output signals from the magnetic sensors 26a and 26b enter the detection circuit 303. Here, the detection circuit 3
03 will be described. The magnetic sensors 26a and 26b are arranged to detect magnetic field components in opposite directions, respectively.
The signal lines are connected in series and connected to the detection circuit 81 of the magnetic sensor. By connecting in this way and detecting the magnetic field with one detection circuit, the difference between the magnetic field components at the two points can be directly detected, and the direct magnetic field from the dominant excitation magnetic field at the positions of the two points is cancelled. However, only the magnetic field distortion due to the speed effect can be accurately detected.

On the other hand, when a pair of magnetic sensors are separately connected to a detection circuit, and a magnetic field is detected once to generate a voltage signal and the difference is obtained, a direct magnetic field from the excitation magnetic field is obtained at two positions. Since the magnetic field distortion is small and the magnetic field distortion is small, if the accuracy of the detection circuit is insufficient, the magnetic field distortion due to the speed effect cannot be accurately detected. Although a circuit using a supersaturated magnetic sensor disclosed in JP-A-1-308982 is shown here, a pickup coil in which a winding is simply applied to a magnetic core may be used instead.
In this case, the detection circuit 81 is not necessary, and the signal from the winding may be directly obtained as a difference and then input to the phase detector.

When the accuracy in manufacturing the device is insufficient, the symmetry of the exciting magnetic field at the two magnetic sensor positions is poor, and the exciting magnetic field cannot be canceled by simply taking the difference, a bridge circuit is provided after the magnetic sensor. And the difference may be taken. Further, the output signal of the detection circuit 81 of the magnetic sensor passes through a band-pass filter 312 having the excitation frequency as a center frequency to remove an unnecessary noise signal, and the synchronous detector 311 (or a phase detector) outputs the same signal as the excitation current. Is detected (in this case, the phase is low, so the phase may be the same). The magnitude of the signal after the detection is a magnetic field distortion signal corresponding to the flow velocity.

Further, the temperature drift correction circuit 304 removes a temperature drift component from the magnetic field distortion signal. In the temperature drift correction circuit 304, the E-type magnetic field generator 2
8, the difference between the outputs of the thermocouples 315 and 316 attached to both ends of the magnetic field generator, a temperature difference signal near the detection windings at both ends of the magnetic field generator is output, and the temperature drift is included through an amplifier 313 set to an appropriate magnification. Subtract from the magnetic field distortion signal. Here, the magnification of the amplifier, that is, the correction coefficient, is determined by performing a heating test offline for the entire apparatus including the magnetic field generator and the cooling chassis. Thereafter, the magnetic field distortion signal excluding the temperature drift is supplied to the eddy current meter 56.
A lift-off correction is performed by a lift-off correction circuit 97 together with a distance signal from the target to the target surface. In the lift-off correction circuit 97, the output signal of the eddy current range finder is
After being converted into a distance signal by the detection circuit 85, the signal is multiplied by a divider 87 with a magnetic field distortion signal excluding temperature drift through an exponential characteristic amplifier 86, and a final speed output signal is obtained through a linear amplifier 88 having a variable gain. Become. Here, the exponential characteristic amplifier can be assembled, for example, by a broken line circuit. Further, as described above, the coefficient of the exponential function is obtained by previously measuring the distance-speed sensitivity curve with respect to the target surface, and the gain of the linear amplifier 88 is calculated in advance using the speed signal measured by another method. Make adjustments.

Next, an example of the measurement result of this embodiment is shown in FIG.
This will be described with reference to FIGS. 18, 19, 20, and 21. FIG. 17 is a diagram showing an output example in which the velocity of the low melting point alloy metal is measured by the velocity measuring device of this embodiment. FIG. 17A shows a value obtained by detecting the speed of the object to be measured by another method, and FIG. 17B shows a speed signal detected by the speed measuring device of this embodiment. This is temperature drift correction,
This is a magnetic field distortion signal due to a raw speed effect before the lift-off correction. As shown in FIG. 17B, in a room temperature environment, if the distance from the target surface does not change significantly, a signal that follows the speed of the measurement target can be obtained without any particular correction.

FIG. 18 shows a comparison of the temperature change of the magnetic field generator due to the difference in the structure of the air-cooled chassis. FIG.
(A), (b), and (c) show the results of the air-cooled chassis of FIG. 9 described above, and FIGS. 18 (d) and (e) show that air is simply blown from both sides of the chassis as shown in FIG. 11 (a). The result depends on the type. Here, heat is applied from the bottom of the air-cooled chassis to raise the temperature of the entire apparatus. Note that FIG.
In (a), (b), and (c), the sensor head is separated from the bottom of the inner box, and is in contact with each other in FIGS. 18 (a), (b) and (c) show the results with a double air-cooled box, and FIGS. 18 (d) and (e) show the results with a single air-cooled box. 18A shows the temperature of the outer wall surface of the outer case of the air-cooled chassis, FIG. 18B shows the temperature of the outer wall surface of the inner case of the air-cooled chassis, and FIG. 18C shows the temperature of the magnetic field generator.
2 is the temperature of the center leg, and 403 is the temperature of the leg at one end of the magnetic field generator. FIG. 18D shows the temperature of the outer wall surface of the air-cooled chassis, and FIG.
04 is the temperature of the center leg, and 405 is the temperature of the leg at one end of the magnetic field generator.

Here, the flow rate of the cooling air blown into the inner box in FIGS. 18 (a), (b) and (c) is the same as the flow rate of the cooling air blown into the chassis in FIGS. 18 (d) and (e). ing. As can be seen from FIG. 18 (b), the bottom surface and the side wall of the cooling chassis are doubled, and the structure in which the cooling air flows between the double walls suppresses a rise in the temperature of the wall of the inner box. Thus, the amount of heat transmitted to the sensor head in the chassis can be reduced.

As can be seen from FIG. 18 (e), when cooling air is directly applied to the sensor head, E
The temperature at both ends of the mold core is suppressed from rising at a lower temperature, and becomes lower than the temperature at the center where the temperature is not applied while the temperature is changing. On the other hand, by convection inside the chassis without directly applying cooling air to the sensor head, FIG.
As shown in (c), the temperature at both ends of the E-shaped core and the inclination of the temperature rise at the center leg are close. Therefore, it can be seen that the temperature difference during the temperature change is small, and the temperature of the sensor head can be kept more uniform.

FIGS. 19A and 19B show output signals of the flow velocity measuring device when the temperature of the cooling air changes. Here, there is nothing below the flow rate measuring device, and only a change in the signal when the temperature of the cooling air changes is shown. FIG. 19A shows the temperature of the cooling air, and FIG. 19B shows the output signal of the flow velocity measuring device before the temperature drift correction. Thus, it can be seen that the flow velocity signal greatly changes due to the temperature change of the cooling air. On the other hand, FIGS. 19 (c) and (d)
Is an output signal after the cooling air temperature is controlled. Here, FIG. 19C shows the temperature of the cooling air, and FIG. 19D shows the output signal of the flow velocity measuring device before the temperature drift correction. It can be seen that the flow velocity signal becomes stable if the temperature of the cooling air is kept constant.

Next, an example of a measurement result under a high temperature environment will be described.
FIG. 20 is an example in which the flow rate of high-temperature molten steel is measured by the present measuring device. Here, since molten steel flows under the measuring apparatus, the ambient temperature changes greatly due to heat radiation from under the measuring apparatus. FIG. 20A shows a value obtained by calculating the flow velocity of the measurement target from the weight of the flow and the cross-sectional area of the flow. FIG.
(B) is a magnetic field distortion signal before temperature drift correction detected by the present flow velocity measuring device. FIG. 20C shows the temperature of the two legs at both ends of the magnetic field generator, and FIG. 20D shows the temperature difference between the two legs. FIG. 20E shows the flow velocity measurement signal after the temperature drift correction. In this way, the temperature drift correction method described above reduces the effect of temperature drift due to changes in ambient temperature, and for high-temperature liquid metals such as molten steel,
It can be seen that the flow velocity can be measured stably even under a temperature change of the environment.

FIG. 21 shows a similar measurement result when the temperature setting value of the cooling air is set to 60 ° C. Here, FIG. 21 (a) is the flow velocity of the measurement target, FIG. 21 (b) is the temperature of the two legs at both ends of the magnetic field generator, and FIG. 21 (c) is before the temperature drift correction detected by the present flow velocity measurement apparatus. This is a magnetic field distortion signal. Thus, by setting the temperature inside the cooling chassis high from the beginning, it can be seen that the temperature of the sensor head becomes non-uniform, and the temperature drift is greatly reduced without any correction.

Next, the case where the distance to the target surface fluctuates will be described. FIG. 22 is a diagram illustrating an example of a measurement result when the distance to the target surface changes. FIG. 22A shows a distance signal measured by the eddy current rangefinder, and FIG. 22B shows an output signal of the speedometer before lift-off correction. FIG. 23 (b)
23 is corrected by the correction circuit 97 shown in FIG. 20 using the signal shown in FIG. 23A, and the result shown in FIG. 23C is obtained. With such a lift-off correction method, the speed can be measured stably even if the distance to the target surface changes.

FIG. 23 shows a first example in which the flow velocity measuring device of this embodiment is applied to a continuous casting line. Tundish 1
The sensor head 200 of the present embodiment, which is put in an empty box (not shown) from the lower surface of 02, is hung and placed on the molten metal surface. Thus, the flow rate 105 of the molten steel in the mold 104 is monitored, the flow rate is controlled to stabilize the flow, and the occurrence of quality defects due to the fluctuation of the surface flow during continuous casting can be prevented. In addition, by arranging two of these sensor heads in the long side direction at symmetrical positions around the nozzle, the left-right asymmetry of the surface flow can be monitored.

FIG. 24 shows a second example in which the flow velocity measuring device of this embodiment is applied to a continuous casting line. Here, the long side 215 of the molten steel is sandwiched by the water-cooled mold 206.
During the molding of the nozzle, the nozzle 213
The sensor head 20 of the present embodiment between
Set 0. The orientation of the sensor head 200 is such that two detection windings (not shown) are arranged in parallel to the molten metal surface as shown in FIG. With this arrangement, the flow velocity 209 on the mold surface can be measured. Further, as shown in FIG. 24, by arranging two sensor heads 200 symmetrically around the nozzle in the long side 215 direction, the left-right asymmetry of the surface flow can be monitored. In addition to this, if the position and the direction of the sensor are changed, not only the surface flow velocity but also various flow rates in the mold can be measured.

For example, as shown in FIG. 25, the sensor head 200 is
If two detection windings are arranged between the nozzle and the mold short side 214 so as to be arranged in parallel with the discharge flow from the nozzle 213 (can be estimated from the angle of the discharge port of the nozzle), the nozzle 21
3 can be measured. Further, nozzle 2
By arranging two sensor heads 200 symmetrically with respect to 13, the imbalance between the left and right of the nozzle discharge flow can be monitored, and the right and left flow velocity balance can be estimated on the surface of the molten steel.

Further, as shown in FIG. 26, the sensor head 200
If the two detection windings are arranged in parallel with the flow descending from the nozzle 213 between the nozzle 3 and the short side 214 of the mold, the descending flow 211 can be measured. If the descending flow is too strong, inclusions contained in the molten steel cannot be lifted, but are carried to a deeper position in the molten steel layer, and are directly captured by the slab, resulting in a product defect. Therefore, if this descending flow can be monitored, the occurrence of a defect can be predicted and preventive measures can be taken.

As described above, the sensor head 20 is
If 0 is set, since the mold is water-cooled, there is no need to cool the sensor head 200 particularly by placing it in an air-cooled chassis. However, in this case, since the excitation is performed with a copper mold having a thickness of about 50 mm interposed, the excitation frequency needs to be set low.

FIG. 27 shows a third example in which the flow velocity measuring device of this embodiment is applied to a continuous casting line. here,
The sensor head 200 is installed immediately below the long side mold. As shown in FIG. 27, the orientation of the sensor head 200 is set so that the two detection windings are arranged in parallel to the direction in which the slab is pulled out. If installed in this way, the downward flow of molten steel 2
Measurement of the flow velocity of No. 11 becomes possible. In the second example described above, the descending flow can be measured, but in the former case, since the copper mold is interposed, in order to excite the magnetic field, the frequency must be set at a considerably low frequency, and the start of the detection winding is generated. The power will be low. With this arrangement, there is only a solidified shell between the sensor head 200 and the molten steel flow. In the case of continuous casting of molten steel, in general, the conductivity of the solidified shell is 1% of copper.
/ 80, which is quite small, and the thickness is about 30 to 40 mm, which is thinner than that of the copper mold. Therefore, the frequency may be higher than that of the second example, and the electromotive force of the detection winding is relatively high, and the detection accuracy is improved. . In this case, the sensor head 200
The shell between the steel flow and the molten steel flow is also drawn downward and has a velocity, and the output of the sensor head 200 detects the sum of this velocity and the molten steel downward flow. However, since the speed of the shell is as low as several m / min, there is no significant influence on the downflow velocity.

Embodiment 2 FIG. FIG. 31 is a block diagram showing a configuration of a measuring circuit of the speed measuring device of this embodiment. In the present embodiment, similarly to the first embodiment, an eddy current meter 56 is used as shown in FIG. 16, and an air-cooled box 49 is used as shown in FIG. Here, as in the case of the first embodiment, the velocity measuring device includes a magnetic field generator 28 and magnetic sensors 26a and 26b which are the basis of the velocity measurement as shown in FIG. And an air-cooled box 49 for measurement in a high-temperature environment as shown in FIG. 9 between the magnetic field generator 28 and the measurement target surface 29. , A shield plate 30 is provided.

The magnetic field generator 28 of this embodiment also has a magnetic core type exciting coil using a magnetic material. As shown in FIG. 1, an E-shaped magnetic core 25 made of a magnetic material and windings 27a, 27b, 2
7c. Here, when measuring the velocity under a normal environment, any magnetic core can be used as long as it can excite a large magnetic field to some extent. For example, a magnetic core laminated with 3% silicon steel sheet can be used. However, in a high-temperature measurement environment, in order to suppress thermal deformation of the magnetic core due to a temperature change, it is better to use an integrated core such as a ferrite core than to use a laminated magnetic core.

As shown in FIG. 28, the magnetic poles 25a and 25b at both ends of the magnetic field generator 28
Inside, two magnetic sensors 26a, 26 using a magnetic core
b is arranged to detect a component of a magnetic field in a direction perpendicular to the conductor surface. Here, the magnetic sensor is fixed to the magnetic poles at both ends of the magnetic field generator in order to suppress temperature drift.
Further, here, as the magnetic sensor, Japanese Patent Application Laid-Open No. 1-308
No. 982, a magnetic measuring apparatus using a magnetic core is used, and a copper plate 5
What was laminated by mm was used. The shield plate 30 may be made of any material as long as it is a conductive and non-magnetic shield plate.

Further, as shown in FIG. 16, an eddy current rangefinder 56 is arranged in front of the magnetic pole 25c at the center of the magnetic field generator 28 for lift-off correction. Here, the eddy current distance meter 56
A differential feedback type eddy current distance meter as shown in Japanese Patent Publication No. Sho 62-30562 was used. When measuring the speed in a high-temperature environment, a magnetic field generator, a magnetic sensor, and an eddy current meter are arranged in an air-cooled box 49 as shown in FIG. 9 to cool the sensor head 200 evenly.

As shown in FIG. 31, the measurement circuit includes an excitation circuit 94, a detection circuit 96, and a temperature drift correction circuit 95.
And a lift-off correction circuit 97. Next, the operation of the measurement circuit of this embodiment will be described. First,
The excitation circuit 94 supplies a current to the magnetic field generator 28 and excites a magnetic field to the object to be measured.
Hz low frequency f ₁ of the oscillator 77 and the high frequency f ₂ of the oscillator 78 from the low frequency f ₁ in the range of 1～1000Hz, adder 79, and a constant current amplifier 80. The two frequencies are used for temperature drift correction described later. The operation of the excitation circuit 94 firstly includes the oscillator 77,
At 78, a sine wave of two frequencies is generated,
9, the two waveforms are superimposed and sent to the exciting coil via the constant current amplifier 80. The excitation coils 27a, 27
b, 27c are 180 ° adjacent to each other
Excitation current flows such that adjacent magnetic poles have opposite directions at the time of each instant.

The output signals from the magnetic sensors 26a and 26b enter the detection circuit 96. Here, the detection circuit 96
Will be described. The magnetic sensors 26a and 26b are arranged so as to detect magnetic field components in opposite directions, and are connected to a detection circuit 81 of the magnetic sensor by connecting signal lines in series. By connecting in this way and detecting the magnetic field with one detection circuit, the difference between the magnetic field components at the two points can be directly detected, and the direct magnetic field from the dominant excitation magnetic field at the positions of the two points is cancelled. However, only the magnetic field distortion due to the speed effect can be accurately detected. Further, the output signal of the detection circuit 81 of the magnetic sensor is divided into two, and first passes through band-pass filters 75 and 76 having center frequencies corresponding to the low frequency f ₁ and the high frequency f _{2 of the} excitation frequency. The two synchronous detectors 83 and 84 (or phase detectors) detect the exciting current and the specific phase component corresponding to low frequency f ₁ and high frequency f ₂ , respectively. Then, the magnitude of the signal after the detection becomes a magnetic field distortion signal corresponding to the speed at each frequency.

Further, in the temperature drift correction circuit 95, the difference between the two detected frequency components is obtained from the magnetic field distortion signal, and the temperature drift is excluded. Thereafter, the magnetic field distortion signal excluding the temperature drift is supplied to the lift-off correction circuit 9 together with the distance signal from the eddy current rangefinder 56 to the target surface.
7, the lift-off correction is performed. Lift-off correction circuit 9
In FIG. 7, the output signal of the eddy current rangefinder is converted into a distance signal by the drive / detection circuit 85 of the rangefinder and then multiplied by the divider 87 with the magnetic field distortion signal excluding the temperature drift through the exponential characteristic amplifier 86. Then, the final speed output signal is passed through a linear amplifier 88 having a variable gain.

Next, an example of the measurement result of this embodiment will be described with reference to FIG. FIG. 32 is a diagram showing measurement results obtained by measuring the flow velocity of high-temperature molten steel by the velocity measuring device of this embodiment. Here, since molten steel flows under the measuring device, the temperature of the device greatly changes due to heat radiation from below the device, and a temperature drift occurs.

FIG. 32A shows a value obtained by calculating the flow velocity of the object to be measured from the weight of the flow and the cross-sectional area of the flow. FIG. 32 (b) shows the results of measuring the temperatures of the magnetic poles at both ends of the magnetic field generator with a thermocouple (100, 101), and FIG.
(C) of FIG. 32 is a magnetic field distortion signal before temperature drift correction for a low frequency detected by the velocity measuring device, and (d) of FIG.
Is a magnetic field distortion signal for a high frequency. As shown in FIG. 32, even if the entire magnetic field generator is cooled evenly by an air-cooled box and the magnetic sensor is fixed to the iron core of the magnetic field generator,
Temperature drift due to temperature change of the iron core still remains,
Also, the temperature drift for the low frequency is equal to the temperature drift for the high frequency, and the speed signal for the low frequency is
It can be seen that it is larger than the speed signal for the high frequency. Then, if the temperature drift is corrected by subtracting the low frequency signal from the high frequency signal, a signal as shown in FIG. 32 (e) is obtained. With such a temperature drift correction method, it is possible to stably measure the flow velocity of a high-temperature liquid metal such as molten steel even under environmental temperature changes, excluding temperature drift.

Embodiment 3 FIG. FIG. 33 is a front view showing the appearance of the sensor head of the speed measuring device according to another embodiment of the present invention,
FIG. 34 is a block diagram showing a configuration of a measuring circuit of the speed measuring apparatus according to the present embodiment. In this embodiment, an air-core type exciting coil and an air-core type detecting coil are used. The velocity measuring device of this embodiment is mainly used under a large disturbance magnetic field, for example, when measuring the flow velocity of molten steel in a continuous casting facility having a device for generating a large magnetic field such as an electromagnetic stirrer. Is used for the purpose of measuring.

Here, the sensor head 200 which is the basis of the velocity measurement as shown in FIG. 33 has an eddy current distance used for lift-off correction when the distance between the magnetic field generator 110 and the magnetic sensors 111a and 111b and the surface to be measured changes. A magnetic field generator 11 (see FIG. 9) for measuring in a high temperature environment.
A shield plate (see FIG. 28) is provided between 0 and the measurement target surface 29. The magnetic field generator 110 is an air-core type exciting coil composed of only windings, and has windings 27a, 27b, and 27c on three legs of a bobbin 112 made of an E-type ceramic as shown in FIG. In a high-temperature measurement environment, it is necessary to fix the windings with an adhesive so that the relative positions between the windings do not shift due to thermal expansion.

The magnetic sensor is an air-core detecting coil consisting of only windings. As shown in FIG. 33, inside the legs 114a and 114b at both ends of the magnetic field generator, windings 116a and 116b are formed on ceramic bobbins 115a and 115b. The device provided with 116b is arranged so as to detect a component of a magnetic field in a direction perpendicular to the conductor surface. Here, the magnetic sensors 111a, 11a
The bobbins 115a and 115b of 1b are adhered to both sides of the bobbin 112 of the magnetic field generator 110 or processed integrally with the bobbin 112 of the magnetic field generator 110 to suppress temperature drift. Further, an eddy current rangefinder is arranged in front of the magnetic pole at the center of the magnetic field generator 110 as in the first embodiment for lift-off correction. When measuring the speed in a high-temperature environment, a sensor head including a magnetic field generator, a magnetic sensor, and an eddy current rangefinder is arranged in an air-cooled box 49 as shown in FIG.
The both ends of the magnetic field generator are uniformly cooled so that the temperature drift is reduced.

As shown in FIG. 34, the measuring circuit of this embodiment has an exciting circuit 118, a temperature drift correcting circuit 11
9, a detection circuit 120, and a lift-off correction circuit 121. Next, the operation of the measurement circuit of this embodiment will be described. First, the excitation circuit 118 supplies a current to the magnetic field generator 110 to excite the magnetic field in the measurement target. The excitation circuit 118 has a low frequency f ₁ of _{1 to} 1000 Hz and a low frequency f ₁ in the range of ₁ to 1000 Hz. high frequency f ₂ of the oscillator 124 from _1, adder 125, and a constant current amplifier 126. The two frequencies are used for temperature drift correction described later.

Here, it is necessary to set the excitation frequency to a value sufficiently distant from the frequency band where the disturbance magnetic field is large. For example, in the case of electromagnetic stirring, the frequency is 1 to
Since it is a very low frequency of about 2 Hz, if the excitation frequency is set to several tens Hz or more, no large disturbance magnetic field exists at that frequency. Sine waves of two frequencies are generated by oscillators 123 and 124 and superimposed by adder 125,
It is sent to the exciting coil via the constant current amplifier 126. In addition,
Exciting current is supplied to the exciting coils 27a, 27b, and 27c such that adjacent magnetic poles have a phase difference of 180 °, and the adjacent magnetic poles have opposite directions at each instant of time. .

The output signals from the detection coils 116a and 116b enter the detection circuit 120,
a, 116b, the signal is divided into two. First, a band-pass filter 1 having a center frequency corresponding to each of the low-frequency f ₁ and high-frequency f ₂ excitation frequencies.
29, 130, a signal due to a large disturbance magnetic field is excluded in advance. Further, two synchronous detectors 131 and 132 (or phase detectors) detect the exciting current and the specific phase component corresponding to the low frequency f ₁ and the high frequency f ₂ , respectively. Here, the difference between the signals from the two detection coils was simply calculated, but the accuracy in manufacturing the device was insufficient, the symmetry of the excitation magnetic field at the position of the two air-core detection coils was poor, and the difference was simply calculated. When the excitation magnetic field cannot be canceled, a difference may be obtained by inserting a bridge circuit after the air-core detection coil. The magnitude of the signal after the detection is a magnetic field distortion signal corresponding to the velocity at each frequency.

Further, the temperature drift of the magnetic field distortion signal is excluded in the temperature drift correction circuit 119 as in the second embodiment. Here, the magnetic sensors 111a, 111b
Since the magnetic field detection sensitivity increases in proportion to the frequency, it is necessary to perform frequency correction before temperature drift correction. Here, f ₁ the frequency of the high frequency component low frequency, when the frequency of the high frequency and f _2, the low-frequency component as shown in FIG. 34 in the intact, f ₁ the frequency component by an amplifier 133
/ F ₂ times. Thereafter, the difference between the two frequency components is taken to exclude the temperature drift.

The magnetic field distortion signal excluding the temperature drift is
Along with the distance signal from the eddy current distance meter 56 to the target surface, similarly to the second embodiment, the eddy current distance meter drive / detection circuit 135, exponential characteristic amplifier 136, multiplier 137, and linear amplifier 13
The lift-off correction is performed by a lift-off correction circuit 121 composed of the lift-off circuit 8. Next, an example of the measurement results of this embodiment is shown in FIG.
5 will be described. FIG. 35 is an output example in which a magnetic field of several hundred G is applied to the present velocity measuring device at a low frequency from the outside, and the flow rate of the low melting point alloy metal is measured under the magnetic field. FIG. 35A shows a value obtained by detecting the speed of the measurement object by another method.
(B) is a velocity signal detected by the velocity measuring apparatus, which is a magnetic field distortion signal due to a raw velocity effect before temperature drift correction and lift-off correction. Thus, by using the air-core type excitation coil and the air-core type detection coil, and further canceling the disturbance magnetic field with a band-pass filter, it is possible to obtain a signal that follows the speed of the measurement target. Application to the continuous casting line of the speed measuring device of this embodiment can be realized with the same arrangement as that of the second embodiment.

Although the same temperature drift correction method as that of the second embodiment has been described here, the temperature drift may be corrected from the temperature distribution of the speed detection device as in the first embodiment. At that time, the thermocouple for detecting the temperature difference may be attached to, for example, the excitation windings 27a and 27c at both ends.

Embodiment 4 FIG. FIG. 36 is a front view showing the appearance of the sensor head of the speed measuring device according to another embodiment of the present invention. In this embodiment, an iron core type excitation coil similar to that of the first embodiment is used as a magnetic field generator, and an air core type detection coil similar to the third embodiment is used as a magnetic sensor. This device is used for the purpose of measuring the speed under the disturbance magnetic field when the magnitude of the disturbance magnetic field is relatively smaller than that of the third embodiment and the magnetic core of the magnetic field generator is not magnetically saturated. You. In this embodiment, similarly to the third embodiment, the magnetic field generator 28 and the magnetic sensors 111a,
b, an eddy current range meter (not shown) used for lift-off correction when the distance to the surface to be measured changes, an air-cooled box for measurement in a high temperature environment (FIG. 9), and a measurement circuit (similar to FIG. 34) (Omitted). Although not shown in FIG. 36, the magnetic field generator 28 and the measurement target surface 2 are similar to the first embodiment.
9, a shield plate (see FIG. 28) is provided. The magnetic field generator is a magnetic core type excitation coil using a magnetic material, and an E-shaped magnetic core 25 made of a magnetic material as shown in FIG.
It consists of windings 27a, 27b, 27c. Here, the magnetic core used was a laminate of 3% silicon steel sheets. As a magnetic sensor, as shown in FIG. 36, two air-core detection coils 111a, b. b is arranged to detect a component of a magnetic field in a direction perpendicular to the conductor surface. Here, the bobbins of the air-core detection coil were adhered to the legs at both ends of the magnetic field generator to suppress temperature drift. Further, the eddy current range meter for lift-off correction, the air-cooled box for speed measurement in a high-temperature environment, and the measurement circuit are all the same as those in the third embodiment, and the description is omitted here.

Next, the measurement result of this embodiment will be described with reference to FIG. FIG. 37 is an output example in which a magnetic field of several tens G is applied to the present speed measuring device at a low frequency from the outside, and the flow rate of the low melting point alloy metal is measured under the applied magnetic field. FIG. 37A shows a value obtained by detecting the speed of the object to be measured by another method, and FIG. 37B shows a speed signal detected by the present speed measuring device, which is a raw signal before temperature drift correction and lift-off correction. This is a magnetic field distortion signal due to the speed effect. Under such a disturbance magnetic field, the magnetic core of the magnetic field generator did not magnetically saturate. However, if the magnetic sensor using the magnetic core used in Example 1 was used as the magnetic sensor, accurate magnetic field detection could be performed. Did not. As described above, if the disturbance magnetic field is small and the magnetic core is not saturated, a signal that follows the speed of the measurement target can be obtained even with the use of the magnetic core type excitation coil and the air core type detection coil. Here, a detection coil having the same specifications as in the third embodiment is used as the magnetic sensor, and the number of turns around the magnetic core is set so that the output magnetic field from the magnetic field generator is the same as in the third embodiment. -The excitation current was determined. Therefore, the sensitivity to the flow velocity in this embodiment and the third embodiment is almost the same.
On the other hand, as for the size of the magnetic field generator, in FIG. 36, the number of turns of the excitation winding can be significantly reduced as compared with the third embodiment because of the use of the magnetic core. Was smaller than that of Example 3. Embodiment 5 FIG. FIG. 38 is a front view showing the appearance of the sensor head of the speed measuring device according to another embodiment of the present invention. Here, the magnetic field generator 28 has a magnetic core type exciting coil using a magnetic material as in the first embodiment, and as shown in FIG. 1, an E-shaped magnetic core 25 made of a magnetic material and windings 27a, 27b, 27c. It is composed of Here, a magnetic core laminated with 3% silicon steel sheet was used.

As shown in FIG. 38, the magnetic poles 25a, 25b at both ends of the magnetic field generator 28 are used as the magnetic sensor.
Inside, two magnetic sensors 26a, 26 using a magnetic core
b is arranged to detect a component of a magnetic field in a direction perpendicular to the conductor surface. Here, the magnetic sensor is fixed to the magnetic poles at both ends of the magnetic field generator in order to suppress temperature drift.
The magnetic field generator may be a ceramic bobbin with a winding wound as shown in FIG. 33 without using a magnetic core. Here, the sensor head 200 is surrounded by a magnetic shield box 32. Magnetic shield box 32
Here, a type surrounding four side surfaces and an upper surface as shown in FIG. 5 was used. The material is pure iron and the plate pressure is 10mm
It is.

In addition, in the flow velocity measuring device of the present embodiment, a measuring circuit similar to that of the first embodiment as shown in FIG. 39 was used. The operation of the circuit is the same as that of the first embodiment, except that the temperature drift correction circuit and the lift-off correction circuit are not provided. In addition, a lift-off correction circuit, a distance meter, a temperature drift correction circuit, and an air-cooling box are added when there is a distance fluctuation or when the temperature is high as in the first and second embodiments. In this embodiment, no addition is made since there is no distance fluctuation or temperature rise.

Next, an example of the measurement result of this embodiment will be described with reference to FIGS. FIG. 41 shows the result of measuring the influence of the disturbance on the signal. Here, a state of a change in the output signal of the flow velocity measuring device when the magnetic body plate 31 is brought close to the detection surface on one side of the magnetic field generator 28 in parallel as shown in FIG. 40 is shown. FIG. 41A shows a case where there is no shield.
(B) is a case where there is a shield. As shown in FIG. 41A, when there is no shield, the signal greatly changes due to the approach of the magnetic material, but when the shield is present, the influence on the signal is greatly reduced.

FIG. 43 shows how the output signal of the flow velocity measuring device changes when a magnetic field is applied to the magnetic field generator 28 from outside. Here, the two coils 207 as shown in FIG. 42 were used to excite the magnetic poles on one side in the direction perpendicular to the arrangement of the detectors. FIG. 43A shows a case without a shield, and FIG. 43B shows a case with a shield.
The frequency of the magnetic field applied from the outside is the same as the exciting current, 14 Hz
The excitation current was determined such that a magnitude of 1 G was generated at the center of the two coils 207 when the size was empty. From FIG. 43A, it can be seen that the signal greatly changes when there is a magnetic field when there is no shield as shown in FIG. From the above results, it can be seen that with the shield, a stable signal can be obtained even when there is disturbance.

[0096]

As described above, according to the first aspect, a magnetic field is generated perpendicularly to a moving conductive measurement object, and at least two magnetic field components perpendicular to the measurement object are measured. Detected at different positions in the moving direction of the target object and at a position where the magnetic field is symmetric, and based on a difference signal of at least two magnetic fields detected at the position where the magnetic field is symmetric, the flow velocity of the measurement target object Is calculated, the measurement can be performed at a position distant from the measurement target object, and the flow velocity can be measured with very high sensitivity. Further, the magnetic field generating means has at least three magnetic poles.
The detecting means includes at least a central magnetic pole and magnetic poles at both ends.
High sensitivity because it is installed at a position between the poles
The flow velocity can be measured. According to the second aspect, an AC magnetic field is used as the exciting magnetic field, and among the detected magnetic field difference signals, only a component of a specific phase is detected at the same frequency as the exciting magnetic field, and based on the detected signal, Since the flow velocity of the object to be measured is calculated, the effect of the disturbance magnetic field is reduced, and the flow velocity can be measured accurately.

According to the third aspect of the present invention, a magnetic field having two frequency components is vertically generated on a moving conductive object to be measured via a conductive non-magnetic shield plate. At least two magnetic field components perpendicular to the object are detected in two different frequency components at different positions in the moving direction of the measurement target object and at positions where the magnetic field is symmetric, and two frequencies are detected at positions where the magnetic field is symmetric. Since the flow velocity of the object to be measured is calculated based on difference signals of at least two magnetic fields detected for each component,
There is an effect that the influence of the temperature change is reduced and the flow velocity can be measured stably. According to the fourth aspect, the distance between the detection position of the magnetic field component and the object to be measured is detected, and the detected magnetic field component is corrected based on the distance. Even if the distance to the object to be measured changes, the flow velocity can be accurately measured.

According to the fifth aspect, the magnetic field generating means generates a magnetic field perpendicular to the conductive measuring object moving by the exciting current, and the at least two detecting means generates a magnetic field perpendicular to the measuring object. The magnetic field component is detected at different positions in the direction of movement of the object to be measured and at positions where the magnetic field is symmetric, the excitation current is supplied to the magnetic field generating means by the measuring means, and the magnetic field is detected at the position where the magnetic field is symmetric by the detecting means The flow velocity of the object to be measured is calculated based on the obtained differential signals of the magnetic fields of at least two places, so that the measurement can be performed at a position distant from the object to be measured, and the flow velocity is very sensitive. Has the effect of being able to measure Also,
The magnetic field generating means has at least three magnetic poles,
The step is at least between the center pole and the poles at both ends.
The flow rate can be measured with high sensitivity.
It works. According to the sixth aspect, an AC exciting current is supplied to the magnetic field generating means to generate an AC magnetic field, and among the detected magnetic field difference signals, only a component having a specific phase at the same frequency as the exciting magnetic field is used. Since the flow rate of the object to be measured is calculated based on the detected signal, the effect of the disturbance magnetic field can be reduced and the flow rate can be measured accurately. According to the seventh invention, the temperature distribution of the magnetic field generating means and the device is measured, and the temperature distribution correcting means for calculating the flow velocity signal detected from the distribution is provided. This has the effect that the flow velocity can be measured stably. According to the eighth aspect, since the magnetic field generating means and the detecting means are arranged in the cooling means having at least a bottom surface made of a non-magnetic nonconductor, the flow velocity of the high-temperature measurement object can be stably measured. It has the effect of.

According to the ninth aspect , the detecting means is fixed to at least both ends of the magnetic poles of the magnetic field generating means having at least three magnetic poles. This has the effect that the influence can be suppressed and the flow velocity can be measured stably. Tenth
According to the invention, since the magnetic field generating means and the detecting means are magnetically shielded, the flow velocity can be accurately measured even in a place where there are various disturbances such as the approach of a magnetic substance or a conductor or the presence of a disturbance magnetic field. According to the eleventh aspect , a conductive and non-magnetic shield plate is inserted between the magnetic field generating means and the detecting means and the object to be measured, and the exciting current having two frequencies is further supplied to the magnetic field generating means by the measuring means. And the magnetic field component detected by the detecting means is divided for each of the two frequency components, and the flow velocity of the object to be measured is calculated based on the magnetic field component divided for each of the two frequency components. This has the effect that the change in the magnetic field component due to the temperature change can be corrected, and the flow velocity can be measured stably.

According to the twelfth aspect , the distance between the detecting means and the object to be measured is detected by the distance detecting means, and further based on the distance detected by the distance detecting means. Since the magnetic field component is corrected, the flow velocity can be measured accurately even if the distance between the detection means and the object to be measured changes. No.
According to the thirteenth aspect, the magnetic field generating means having at least two magnetic poles arranged in parallel to the object to be measured generates a magnetic field perpendicular to the object to be measured and opposite to the object to be measured by the exciting current. Because of this, the spread of the magnetic field can be suppressed, and the flow velocity of the object to be measured can be measured with high sensitivity.

[Brief description of the drawings]

FIG. 1 is a front view showing the appearance of a sensor head of a speed measuring device according to an embodiment (Embodiment 1) of the present invention.

FIG. 2 is an explanatory diagram for explaining the principle of the speed measuring device of the present invention.

FIG. 3 is an explanatory diagram for explaining the principle of the speed measuring device of the present invention.

FIG. 4 is a diagram showing a distortion of an exciting magnetic field when a magnetic body approaches a magnetic field generator and an exciting magnetic field when a magnetic shield is provided.

FIG. 5 is a perspective view of the magnetic shield box of the present invention.

FIG. 6 is a perspective view of another example of the magnetic shield box of the present invention.

FIG. 7 is a perspective view of still another example of the magnetic shield box of the present invention.

FIG. 8 is a diagram showing a state of thermal expansion or thermal contraction of the sensor head.

FIG. 9 is a perspective view showing a configuration of a cooling unit of the present invention.

FIG. 10 is a diagram showing an example of the arrangement of sensor heads in a cooling unit.

FIG. 11 is a diagram illustrating an example of a flow path of cooling air in a cooling unit.

FIG. 12 is a block diagram illustrating an example of a measurement circuit of the flow velocity measurement device according to the first embodiment.

FIG. 13 is a diagram showing the temperature specification of each part of the magnetic field generator (sensor head) of the embodiment of FIG. 1;

FIG. 14 is an explanatory diagram for describing a method of correcting lift-off fluctuation.

FIG. 15 is an explanatory diagram for describing a method of correcting lift-off fluctuation.

FIG. 16 is a perspective view showing the appearance of a sensor head to which the eddy current range meter according to the first embodiment is attached.

FIG. 17 is a view showing an output example in which the velocity of the low melting point alloy metal is measured by the velocity measuring apparatus of the first embodiment.

FIG. 18 is a diagram showing a comparison of a temperature change of the sensor head due to a difference in the structure of the air-cooled chassis.

FIG. 19 is a diagram showing output signals of the flow velocity measuring device when the temperature of the cooling air changes.

FIG. 20 is a diagram illustrating an example in which the flow velocity of high-speed molten steel is measured by the flow velocity measurement device according to the first embodiment.

FIG. 21 is a diagram illustrating a measurement example when the temperature setting of cold air or air is set to 60 ° C.

FIG. 22 is a diagram illustrating an example of a measurement result when the distance to the target surface changes in the first embodiment.

FIG. 23 is a diagram showing an example in which the speed measuring device of Example 1 is applied to a continuous casting line.

FIG. 24 is a diagram showing another application example of the present invention.

FIG. 25 is a diagram showing another application example of the present invention.

FIG. 26 is a diagram showing another application example of the present invention.

FIG. 27 is a diagram showing still another application example of the present invention.

FIG. 28 is a front view showing the appearance of a sensor head of a speed measuring device according to another embodiment (Example 2) of the present invention.

FIG. 29 is an explanatory diagram for describing a temperature drift correction method.

FIG. 30 is an explanatory diagram for explaining a temperature drift correction method.

FIG. 31 is a block diagram illustrating a configuration of a measurement circuit of the speed measurement device according to the second embodiment.

FIG. 32 is a view showing a measurement result obtained by measuring a flow velocity of a high-temperature molten steel by the velocity measuring device of the second embodiment.

FIG. 33 is a front view showing an appearance of a sensor head of a speed measuring device according to another embodiment (Embodiment 3) of the present invention.

FIG. 34 is a block diagram illustrating a configuration of a measurement circuit of the speed measurement device according to the third embodiment.

FIG. 35 is a diagram showing an example of a measurement result of Example 3.

FIG. 36 is a front view showing an appearance of a sensor head of a speed measuring device according to another embodiment (Embodiment 4) of the present invention.

FIG. 37 is a diagram showing an example of a measurement result of Example 4.

FIG. 38 is a front view showing an appearance of a sensor head of a speed measuring device according to another embodiment (Embodiment 5) of the present invention.

FIG. 39 is a block diagram illustrating a configuration of a measurement circuit of the speed measurement device according to the fourth embodiment.

FIG. 40 is a diagram showing a state where a magnetic plate is arranged near a magnetic field generator.

FIG. 41 is a diagram illustrating an influence of a disturbance on a signal in the state of FIG. 40;

FIG. 42 is a diagram showing a state in which a magnetic field generator is excited by two coils.

FIG. 43 is a diagram showing output characteristics in a state where a magnetic field is applied as in FIG. 42;

FIG. 44 is an explanatory diagram for describing continuous casting.

FIG. 45 is an explanatory diagram for explaining a conventional method of measuring the flow velocity of a high-temperature liquid metal by a contact method.

FIG. 46 is an explanatory diagram for explaining a speed effect of a magnetic field.

FIG. 47 is an explanatory diagram for explaining a conventional method of measuring the flow velocity of a non-contact high-temperature liquid metal by magnetism.

FIG. 48 is an explanatory diagram for explaining a conventional method for measuring a flow rate of a non-contact high-temperature liquid metal by magnetism.

FIG. 49 is an explanatory diagram for explaining a conventional method for measuring a flow rate of a non-contact high-temperature liquid metal by magnetism.

[Explanation of symbols]

 25 Iron core 25a, 25b, 25c Magnetic pole 26a, 26b Magnetic sensor 27a, 27b, 27c Winding 28, 110 Magnetic field generator 29 Conductivity measuring object 30 Shield plate 56 Eddy current distance meter 77, 78 Oscillator 79 Adder 80 Constant current Amplifiers 81, 82 Magnetic sensor detectors 83, 84 Synchronous detectors or phase detectors 85 Eddy current range meter drive / detection circuits 86 Exponential characteristic amplifiers 87 Adders 88 Linear amplifiers 94 Excitation circuits 95 Temperature drift correction circuits 96 Detection circuits 97 Lift-off corrections Circuit 112 Ceramic bobbin 113a, 113b, 113c Winding 114a, 114b, 114c Magnetic pole 115a, 115b Ceramic bobbin 116a, 116b Winding 117 Conductivity measuring object 123, 124 Oscillator 125 Adder 126 Constant current amplifier 131, 132 Synchronous detector or phase detector 133 Frequency correction amplifier 138 Linear amplifier 135 Eddy current distance meter drive / detection circuit 136 Exponential characteristic amplifier 118 Excitation circuit 119 Temperature drift correction circuit 120 Detection circuit 121 Lift-off correction circuit 129, 130 Band pass Filter 137 Multiplier 200 Sensor head

──────────────────────────────────────────────────続 き Continuing on the front page (72) Shinichi Nishioka, Inventor 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Hiroharu Kato 1-2-1, Marunouchi, Chiyoda-ku, Tokyo (56) References JP-A-5-297012 (JP, A) JP-A-4-89573 (JP, A) JP-B-53-9111 (JP, B1) JP-B-63-14907 ( JP, B1) JP-B-59-16543 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 5/08 B22D 11/16

Claims (15)

(57) [Claims] 1. Magnetic field generation with at least three magnetic poles
By means, a magnetic field is generated perpendicular to the moving conductive object to be measured, and at least the center of the magnetic poles
The two probes installed between the magnetic poles of the
At least two perpendicular to the object to be measured
Two magnetic field components are detected at different positions in the moving direction of the object to be measured, and at a position where the magnetic field is a target, and a difference between at least two magnetic fields detected at a position where the magnetic field is symmetric. A flow velocity measuring method, wherein a flow velocity of the object to be measured is calculated based on a signal. 2. An AC magnetic field is used as an exciting magnetic field, and only a component of a specific phase is detected at the same frequency as the exciting magnetic field among differential signal of the detected magnetic field, and based on the detected signal, the measurement object is detected. The flow velocity measuring method according to claim 1, wherein the flow velocity of the object is calculated. 3. A magnetic field having two frequency components is generated perpendicularly to a moving conductive measurement target object via a conductive non-magnetic shield plate, and at least a magnetic field perpendicular to the measurement target object is generated. Two magnetic field components are detected for each of two frequency components at different positions in the moving direction of the object to be measured and at a position where the magnetic field is symmetric, and two frequency components are detected at a position where the magnetic field is symmetric. A flow velocity measurement method for calculating the flow velocity of the object to be measured based on a difference signal of at least two magnetic fields detected for each measurement. 4. The apparatus according to claim 1, wherein a distance between a detection position of the magnetic field component and the object to be measured is detected, and the detected magnetic field component is corrected based on the distance. 3. The method for measuring flow velocity according to 3. 5. A magnetic field generating means having at least three magnetic poles and generating a magnetic field perpendicular to a moving conductive object to be measured, and a magnetic pole at the center and magnetic poles at both ends of at least the magnetic poles.
Installed at a position between, the magnetic field component perpendicular to the object to be measured, at a different position in the moving direction of the object to be measured, and at least two detection means for detecting at a position where the magnetic field is symmetrical, Measuring means for supplying the exciting current to the magnetic field generating means and calculating a flow velocity of the object to be measured based on a difference signal of at least two magnetic fields detected by the detecting means. Flow velocity measuring device. 6. An AC exciting current is supplied to the magnetic field generating means to generate an AC magnetic field, and among the detected magnetic field difference signals, only a component having a specific phase at the same frequency as the exciting magnetic field is detected. The flow velocity measuring device according to claim 5, wherein the flow velocity of the object to be measured is calculated based on the detected signal. 7. A temperature distribution of said magnetic field generating means is measured,
The flow velocity measuring apparatus according to claim 5, further comprising a correction unit configured to correct a flow velocity value of the measurement target object. 8. The magnetic field generating means and the detecting means,
8. The flow velocity measuring device according to claim 5, wherein at least a bottom surface is provided in a cooling means made of a nonmagnetic nonconductor. 9. The apparatus according to claim 1, wherein said detecting means is fixed to at least both ends of said magnetic pole.
The flow velocity measuring device according to 5, 6, 7 or 8 . 10. A magnetic shield box which covers the magnetic field generating means and the detecting means except for a portion facing the object to be measured.
The flow velocity measuring device according to 6, 7, 8 or 9 . 11. A non-magnetic conductive and non-magnetic shield plate inserted between the magnetic field generating means and the detecting means and the object to be measured, and the measuring means further comprises the magnetic field generating means , An exciting current having two frequencies is supplied to the measuring object, the magnetic field component detected by the detecting means is divided into the two frequency components, and based on the magnetic field components divided into the two frequency components, 7. The method according to claim 5, wherein the flow velocity of the object is calculated.
The flow velocity measuring device according to 7, 8, 9 or 10 . 12. The apparatus according to claim 12, further comprising: a distance detecting unit configured to detect a distance between the detecting unit and the object to be measured, and further comprising: a measuring unit configured to calculate a distance based on the distance detected by the distance detecting unit. flow rate measuring apparatus according to claim 5,6,7,8,9,10 or 11, wherein the is to correct the magnetic field component. 13. The magnetic field generating means has at least two magnetic poles arranged in parallel with the object to be measured, and is perpendicular to the object to be measured by an exciting current, and is opposite to the magnetic pole adjacent to the object to be measured. A magnetic field is generated, wherein the magnetic field is generated.
Or the flow velocity measuring device according to 12 . 14. A flow rate measuring method according to any one of claims 1 to 4, or a flow rate measuring method according to any one of claims 5 to 13 , wherein: a pouring step of pouring the molten material from a tundish into a mold; A measuring step of measuring and monitoring with the flow velocity measuring device according to the description, a control step of controlling the flow velocity monitored in the measuring step to stabilize the flow, and having a casting step of performing continuous casting from the mold. Characteristic continuous casting method. A tundish 15. pouring molten steel, the molten steel is poured from a tundish, and the mold of continuous casting, in any one of claims 5 to 13, measure and monitor the flow velocity of molten steel is poured into the mold A continuous casting apparatus comprising: the flow velocity measuring device described above; and control means for controlling a flow velocity monitored by the flow velocity measuring device to stabilize the flow.