JPH0933554A - Non-contact flow-velocity detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the flow velocity of melted steel by easily and positively eliminating disturbance signals. SOLUTION: By applying an AC voltage of an oscillator 12 to an excitation coil 5, a magnetic flux is generated and is applied to a melted steel 2 which flows through a core 4, thus generating a flow-velocity voltage eV representing a flow velocity, a still component voltage eS which is a disturbance, and an unbalance voltage eO. The core 4 and the coils 6, 6 are alternately located in forward and backward directions by the drive of a motor 10. The still component voltage eS can be separated by performing phase rectification by a phase rectification circuit 14 and a flow-velocity voltage eV can be taken out by performing the subtraction and division of a voltage eO+eV at the position in forward direction and a voltage eO-eV at the position in backward direction by an operation circuit 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact flow velocity detector, which is effective when applied to, for example, detecting the flow velocity of molten steel in a mold of continuous casting equipment.

[0002]

2. Description of the Related Art A non-contact flow velocity detector (eddy current type velocity meter) is used to measure the flow velocity of molten steel in a mold in a continuous casting facility. Here, a typical example of the conventional non-contact flow velocity detector will be described with reference to FIG.

As shown in FIG. 11, the exciting coil 01 is connected to
The magnetic flux Φ is excited by the current source 02. _oTo occur. pair
The detection coils 03, 04 of the_oWhen
It is arranged in the exciting coil 01 in a rectangular shape. Inspection
The output coils 03 and 04 are differentially connected, and the detection coil
The difference voltage generated at 03 and 04 is amplified by the amplifier 05 and output.
Is forced. This flow velocity detector has a magnetic flux Φ_oIs a table for molten steel 06
It is attached so that it is incident perpendicularly to the surface. Molten steel
06 flows in the direction of arrow B.

The operation of the conventional non-contact flow velocity detector having the above structure will be described with reference to FIG. 11 which is a structural view, FIG. 12 which is a view of the molten steel 06 from the surface side and FIG. 13 which is a waveform diagram. .

The magnetic flux Φ _o generated in the exciting coil 01 interlinks with the molten steel 06, so that an eddy current i _s flows in the molten steel 06. Since the molten steel 06 to the magnetic flux [Phi _o is incident moves, the magnetic flux [Phi _o and the molten steel 06 is relatively moved, a current -i _v, i _v flows in the molten steel 06. This current -i _v, i _v flux [Phi _iv, - [Phi] _iv is caused by, the magnetic flux [Phi _iv, - [Phi] _iv detection coil 0 interlinked in the detection coil 03, 04 of the differential
A voltage (described later in detail) is generated at 3,04. This voltage is amplified by the amplifier 05 and output as a speed signal.

In accordance with Lenz's law, a magnetic flux Φ _s that disturbs the magnetic flux Φ _o is generated by the eddy current i _s . FIG. 13 (a) shows a state seen the distribution of eddy current i _s for the magnetic flux [Phi _s from the side, FIG. 13 (b) side the distribution of current -i _v, i _v with respect to the magnetic flux [Phi _iv, - [Phi] _iv The state seen from.

Here, referring to FIG. 14, the relationship among the voltage, the current and the magnetic flux generated in the conventional non-contact flow velocity detector is shown together. (A) An alternating voltage V is applied to the exciting coil 01 (FIG. 14A). (B) In the exciting coil 01, a current i delayed by 90 ° with respect to the voltage V flows (FIG. 14 (b)). (C) A magnetic flux Φ _{o in} phase with the current i is generated from the exciting coil 01 (FIG. 14 (c)). (D) in the detection coil 03, 04 is the magnetic flux [Phi _o be interlinked, the voltage e ₀ delayed 90 ° to the magnetic flux [Phi _o occurs (FIG. 14 (d)). (E) Since the magnetic flux Φ _o is incident on the molten steel 06,
The eddy current i _s flows (FIG. 14 (e)). The (f) the molten steel 06, since the molten steel 06 moves relative to the magnetic flux [Phi _o, current _{i v (-i v, i v} ) flows (FIG. 14 (f)). Note that 1 is the length of the conductor, that is, the size of the coil. (G) The eddy current i _s causes a magnetic flux Φ _s that interferes with the magnetic flux Φ _o (FIG. 14 (g)). (H) current _{i v (-i v, i v} ) by a magnetic flux Φ
_iv (Φ _iv , −Φ _iv ) occurs (FIG. 14 (h)). (I) A voltage e _s is generated in the detection coils 03 and 04 due to the magnetic flux Φ _s interlinking with each other (FIG. 14 (i)). The (j) detecting coils 03 and 04, a magnetic flux [Phi _iv is the voltage e _v caused by interlinking (FIG 14 (j)).

After all, as can be seen from the above (d) (i) (j), between the differentially connected detection coils 03, 04,
The detection voltage e shown by the following equation (1) is generated.

[0009]

[Equation 1]

In the above equation (1), the voltages e _o and e _s are
It does not indicate the flow velocity of the molten steel 06 but is a disturbance signal.
Therefore, in order to remove the disturbance signals e _o and e _s , the following means are applied.

That is, the unbalanced voltage e _o (= -ndΦ
_o / dt) is generated due to the imbalance of the detection coils 03, 04, so that this imbalance is eliminated and the voltages generated in the detection coils 03, 04 by the magnetic flux Φ _o are made substantially equal to each other, and the unbalance voltage e _o The detection coils 03 and 04 are installed so as to be the minimum, and the residual voltage is electrically canceled.

[0012] stationary component voltage e _s is the voltage caused even when no molten steel flow, the phase with respect to the flow rate voltage e _v is 90
° Different. Utilizing the fact that the phases are different by 90 ° in this way, the voltage _es component is separated (removed) by the phase rectification circuit, and only the flow velocity voltage _ev component indicating the flow velocity of the molten steel 06 is taken out. .

[0013]

By the way, the above-mentioned prior art
Then there were the following problems. (1) Excitation coil 01 and detection coil 0 due to thermal deformation
A large imbalance if the positional relationship with 3, 04 is misaligned
Voltage e_oOccurs. This unbalanced voltage e_oIs the flow rate
Pressure e_vAnd the opposite phase (180 ° phase shift)
Therefore, even if a phase rectifier circuit is used, the unbalanced voltage e_oTo
Flow velocity voltage e_vCannot be excluded from. Therefore this Anne
Balance voltage e_oMay cause drift
Was. (2) Distance between the non-contact molten steel flow velocity detector and the molten steel 06
When the gap G changes, the flow velocity of the molten steel 06 is constant.
However, the flow velocity voltage e_vValue changes and the flow velocity is detected
The accuracy was poor. (3) Unbalanced voltage e due to temperature drift_oIs large
This voltage e _oValue of the signal processing range
There is a risk that it will exceed the limit and measurement will become impossible.

In view of the above-mentioned prior art, the present invention is a non-contact molten steel flow velocity that reliably removes unbalanced voltage, can accurately detect flow velocity even when there is a gap change, and can measure even when temperature drift occurs. The purpose is to provide a detector.

[0015]

The structure of the present invention which achieves the above object is achieved by introducing an exciting coil which is excited by an alternating voltage applied by an oscillator to generate a magnetic flux, and a magnetic flux generated by the exciting coil. , The static component voltage generated by the interlinking of the magnetic flux generated in the direction that interferes with the magnetic flux incident on the conductive fluid, and the magnetic flux incident from the core A detection coil for detecting an unbalanced voltage generated by the magnetic flux generated by the exciting coil and the magnetic flux generated by the magnetic flux generated by the relative movement of the conductive fluid. , The exciting coil, the core, and the detection coil, one end of which is in the forward direction of the conductive fluid and the other end is in the forward direction of the conductive fluid, and the other end is in the upstream side of the conductive fluid. A rotating mechanism that rotates so that the first end of the conductive fluid is located in the opposite direction to the downstream side of the conductive fluid, and a stationary component voltage is separated by phase rectifying the detected voltage detected by the detection coil. The phase rectification circuit that removes and outputs the unbalanced voltage and the flow velocity voltage, the unbalanced voltage and the flow velocity voltage are sent from the phase rectification circuit, and from the unbalanced voltage and the flow velocity voltage obtained at the forward position, An arithmetic circuit that subtracts the unbalanced voltage and the flow velocity voltage obtained at the reverse position and divides the subtracted value by 2 to obtain the flow velocity voltage.

Further, according to the structure of the present invention, an exciting coil which is excited by applying a low-frequency AC voltage by a low-frequency oscillator and a high-frequency voltage by a high-frequency oscillator to generate a low-frequency magnetic flux and a high-frequency magnetic flux, and an exciting coil Generated by interlinking the low-frequency magnetic flux and high-frequency magnetic flux, which are injected into the flowing conductive fluid that is the object to be inspected, with the magnetic flux generated in the direction that interferes with the low-frequency magnetic flux that enters the conductive fluid. Static component voltage, and the flow velocity voltage generated by the interlinkage of the magnetic flux generated by the relative movement of the conductive fluid with respect to the low-frequency magnetic flux incident from the core,
A detection coil for detecting an unbalanced voltage generated by interlinking low-frequency magnetic flux generated in the exciting coil and a gap signal voltage generated by interlinking magnetic flux generated by the high-frequency magnetic flux, and an exciting coil , The core and the detection coil, one end of which is directed toward the upstream side of the conductive fluid and the other end of which is directed toward the downstream side of the conductive fluid, and the other end is directed toward the upstream side of the conductive fluid. Rotation mechanism that rotates so as to be alternately positioned in the reverse position facing the downstream side of the fluid, and phase rectification for the static component voltage, flow velocity voltage and unbalance voltage detected by the detection coil and obtained through the low frequency filter. The phase rectifier circuit that separates and removes the quiescent component voltage to output the unbalanced voltage and the flow velocity voltage by Therefore, the flow velocity voltage is obtained by subtracting the unbalance voltage and flow velocity voltage obtained at the reverse position from the unbalance voltage and flow velocity voltage obtained at the forward position and dividing the subtracted value by two. Based on the value of the gap signal voltage detected by the calculation circuit and the detection coil and obtained through the high frequency filter, the gap change between the core and the conductive fluid is detected, and the change in the flow velocity voltage due to the gap change is corrected. In this way, the gap change correction circuit that corrects the flow velocity voltage extracted by the arithmetic circuit to obtain the flow velocity signal,
It is characterized in that

Further, according to the structure of the present invention, an exciting coil that is excited by applying a low-frequency alternating voltage from the low-frequency oscillator and a high-frequency voltage from the high-frequency oscillator to generate the low-frequency magnetic flux and the high-frequency magnetic flux, and the exciting coil Generated by interlinking the low-frequency magnetic flux and high-frequency magnetic flux, which are injected into the flowing conductive fluid that is the object to be inspected, with the magnetic flux generated in the direction that interferes with the low-frequency magnetic flux that enters the conductive fluid. Static component voltage, and the flow velocity voltage generated by the interlinkage of the magnetic flux generated by the relative movement of the conductive fluid with respect to the low-frequency magnetic flux incident from the core,
A detection coil for detecting an unbalanced voltage generated by interlinking low-frequency magnetic flux generated in the exciting coil and a gap signal voltage generated by interlinking magnetic flux generated by the high-frequency magnetic flux, and an exciting coil , The core and the detection coil, one end of which is directed toward the upstream side of the conductive fluid and the other end of which is directed toward the downstream side of the conductive fluid, and the other end is directed toward the upstream side of the conductive fluid. In a reverse position facing the downstream side of the fluid, a rotating mechanism that rotates so as to be alternately positioned, a detection voltage suppression circuit that suppresses and outputs the value of the voltage detected by the detection coil and obtained through the low frequency filter, The voltage is sent from the phase rectifier circuit that outputs the voltage that separates and removes the static component voltage by performing phase rectification on the voltage output from the detection voltage suppression circuit. The voltage obtained at the forward position is subtracted from the voltage obtained at the backward position, and the subtraction value is divided by 2 to extract the flow velocity voltage, and the high-frequency filter detected by the detection coil. The gap change between the core and the conductive fluid is detected based on the value of the gap signal voltage obtained through, and the flow velocity voltage extracted by the arithmetic circuit is corrected to correct the change in the flow velocity voltage due to the gap change. Gap change correction circuit that obtains the flow velocity signal by
It is characterized in that

According to the first aspect of the invention, since the core and the coil are alternately positioned at the forward direction position and the backward direction position, the detected voltage is phase rectified and then the value at the forward direction position and the backward direction position are detected. By calculating the value at this time, the flow velocity voltage can be obtained.

In the second aspect of the invention, the flow velocity can be accurately detected even if the flow velocity voltage changes due to the change in the gap.

In the third aspect of the invention, the flow velocity can be detected even if a large temperature drift occurs by controlling the value of the unbalanced voltage.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<First Embodiment> FIG. 1 shows a non-contact flow velocity detector according to a first embodiment of the present invention, which is used to detect the flow velocity of molten steel. As shown in the figure, the storage case 1
The lower surface of the, i.e., the surface facing the molten steel 2 is closed by the non-conductive heat insulating plate 3. A C-shaped core 4 is installed in a space surrounded by the storage case 1 and the heat insulating plate 3, and the C-shaped core 4 is provided with an exciting coil 5. A detection coil 6 is provided so as to surround the C-shaped core 4. The molten steel 2 is B
Flowing in the direction. G is a gap.

A rotary seal 7 is provided on the upper end of the storage case 1.
The pipe body 8 is rotatably connected via the pipe 8, and a cooling medium (air or the like) is sent to the inside of the storage case 1 via the pipe body 8 for cooling.

Further, a gear 9 is fixed to the upper part of the storage case 1, and the rotational force of the motor 10 is transmitted to the gear 9 via the gear 11. Therefore, by rotating the motor 10 in the normal and reverse directions, the storage case 1, and thus the core 4 and the coils 5 and 6 rotate in the normal and reverse directions. As a result, as shown in FIGS. 2A and 2B, which is a II-II cross section of FIG. 1, by rotating the motor 10 in the forward and reverse directions, with respect to the flow direction B of the molten steel 2,
The upstream side U of the C-shaped coil 4 may be located on the upstream side of the molten steel and the downstream side D may be located on the downstream side of the molten steel in the forward direction position (FIG. 2A). It is also possible to set the upstream side U on the molten steel upstream side and the upstream side U on the molten steel downstream side in the reverse direction position (FIG. 2 (b)).

On the other hand, to the exciting coil 5, an alternating voltage V oscillated by the oscillator 12 and amplified by the amplifier 13 is applied. The voltage detected by the detection coil 6 is sent to the phase rectification circuit 14. The phase rectifier circuit 14 includes an oscillator 12
And the calculator 15.

In this embodiment, the motor 10 is rotated in the forward and reverse directions to set the positions of the core 4 and the coils 5 and 6 of this detector in the forward direction position (FIG. 2A) and the reverse direction position (FIG. 2B). )) Is changed to exchange and the flow velocity is detected. The voltage, current and magnetic flux generated in the detector at this time are as shown in FIG. In FIG. 3, the waveform in the (positive) column shows the waveform at the forward position, and the waveform in the (reverse) column shows the waveform at the reverse position.

Explaining the waveform of FIG. 3 further, when an alternating voltage V is applied to the exciting coil 5 (a), a voltage i delayed by 90 ° with respect to the voltage V flows in the exciting coil 5 (b), and the current A magnetic flux Φ _{o in} phase with i is generated from the C-shaped core 4 (c). The detection coil 6, the magnetic flux [Phi _o is by interlinked magnetic flux [Phi _o to 90 ° delayed unbalance voltage e _o is generated (d).

An eddy current i _s is generated in the molten steel 2 when the magnetic flux Φ _o is incident (e), and a current _iv flows when the molten steel 2 moves and moves relative to the magnetic flux Φ _o (f). . Flux [Phi _s interfering with the magnetic flux [Phi _o by eddy current i _s is generated (g), the magnetic flux [Phi _iv occurs by a current i _v (h).

Further, in the detection coil 6, a magnetic flux Φ _s interlinks to generate a static component voltage es (i), and the magnetic flux Φ _s is generated.
_iv flow speed voltage e _v is generated by interlinking.

As can be seen from FIGS. 3 (d) (i) (j), the detection voltage e shown in the following equation (2) is generated in the detection coil 6.

[0031] _{e = e o + e s ±} e v ... (2) where e _o: unbalanced voltage occurring deviation (deviation including deformation) of C-shaped core 4 and the detection coil 6 e _s: electromagnetic the molten steel 2 stationary component voltage generated by induction (voltage occurs if no molten steel flow) e _v: when the flow rate voltage generated according to the flow rate of the molten steel 2 (positive direction position + e _v, and -e _v when the reverse position Become)

The phase rectifier circuit 14, the detection voltage e is input, by the phase commutation from the oscillator 12 receiving the oscillating voltage, the stationary component voltage e _s separated and removed from the detected voltage e. That still component voltage e _s, the flow rate voltage e _v
Since there is a 90 ° phase difference with respect to (Fig. 3 (i)
(J)), by performing phase rectification, the static component voltage e
_s is the a can be separated and removed from the flow rate voltage e _v.

The voltage waveform output from the phase rectification circuit 14 is as shown in FIG. That is, the (1) detector forward position phase rectified voltage v ₁ at which have become (position state in FIG. 2 _{(a)), v 1 = e o + e} v ... (3). (2) phase rectified voltage v ₂ at the time that is a (position state in FIG. 2 (b)) detector reverse _{position, v 2 = e o -e v} ... a (4).

That is, by changing the detector in the forward and reverse directions, the flow velocity signal e _v changes in the + direction and the − direction (see FIG. 3 (j)), but the unbalance voltage e _o does not change. The relationships of the expressions (3) and (4) occur. The unbalance voltage e _o gradually increases / decreases due to thermal deformation, but the fact that it is the same even if the detector is changed in the forward and reverse directions at approximately the same time is expressed as “e _o does not change” here. ing.

The calculator 15 obtains the flow velocity voltage e _v by the calculation of the following equation (5). _{e v = (v 1 -v 2} ) ÷ 2 = {(e o + e v) - (e o -e v)} ÷ 2 = 2e v ÷ 2 ... (5)

That is, the calculator 15 divides the value obtained by subtracting the minimum value (that is, v ₂ ) from the maximum value (that is, v ₁ ) of the voltage output from the phase rectification circuit 14 by 2,
The unbalanced voltage e _o can be removed and only the flow velocity voltage e _v can be taken out. Moreover, even if the unbalanced voltage e _o is gradually increased / decreased due to thermal deformation or the like, the value of the voltage e _o is almost the same during one cycle period in which it changes from the positive direction to the reverse direction. By doing
The unbalanced voltage e _o can be removed almost completely.

As described above, according to the first embodiment, even if the positional relationship of the detecting coil 6 becomes unbalanced due to thermal deformation or the like, the unbalanced voltage e _o is surely removed and the flow velocity voltage e is removed.
_v is required. And this flow rate voltage e _v is output as velocity signal indicating the flow rate of the molten steel 2.

FIG. 5 shows a modification of the first embodiment. In this modified example, the detection coil 6 a is arranged in the center of the inside of the C-shaped core 4. The structure and operation of the other parts are the same as in the first embodiment.

<Second Embodiment> Next, a non-contact flow velocity detector according to a second embodiment of the present invention will be described with reference to FIG. The parts having the same functions as those of the first embodiment (FIGS. 1 and 2) are designated by the same reference numerals, and the description of the same function parts will be omitted. In the second embodiment, a correction function for gap change is added.

In the second embodiment, the low frequency (100 to 1000 Hz) AC voltage generated by the low frequency oscillator 20L and the high frequency (10 to 100 kHz) generated by the high frequency oscillator 20H are used.
) Is applied to the exciting coil 5 after being added and amplified by the adding amplifier 21. Therefore, a low-frequency current and a high-frequency current flow in the exciting coil 5 to excite the exciting coil 5, and a low-frequency magnetic flux and a high-frequency magnetic flux are generated from the C-shaped core 4.

The low frequency magnetic flux and the high frequency magnetic flux generated from the C-shaped core 4 act on the molten steel 2 to generate an eddy current in the molten steel 2. Further, the magnetic flux due to the eddy current generated in the molten steel 2 and the magnetic flux due to the C-shaped core 4 act on the detection coil 6, and the detection voltage e (= e _o + _es ±
e _v) and the gap signal voltage e _g by the high-frequency magnetic flux occurs. In the detector of the second embodiment, the core 4 and the coils 5 and 6 also detect the flow velocity while alternately switching the forward position and the backward position, as in the first embodiment.

The band-pass filter 22L passes a voltage signal in the low frequency range (100 to 1000 Hz). Therefore, the detection voltage e (= e _o + e _s ± e _v ) passes through the bandpass filter 22.

The phase rectifier circuit 14 and the arithmetic circuit 15 have a first
It has the same function as the embodiment. That is, the phase rectification circuit 14 separates and removes the static component voltage e _s by performing phase rectification, and the arithmetic circuit 15 outputs the phase rectification voltage v ₁ (= e _o + e
_v) and the value of the difference between the phase rectified voltage _{v 2 (= e o -e v} ), by dividing by 2 to obtain the flow rate signal e _v removing the unbalance voltage e _o.

The bandpass filter 22H passes a voltage signal in the high frequency range (10 to 100 kHz). Therefore, the gap signal voltage e _g is the bandpass filter 22H.
After that, the rectifier circuit 23 produces a DC gap signal voltage E _g .

As shown in FIG. 7, the gap signal voltage E _g
(E _g) is as the gap G increases, its value increases. On the other hand, the flow rate voltage e _v, even the flow rate of the molten steel 2 is the same, the value becomes smaller as the gap G increases. Here, the flow rate of voltage e _v and gap signal voltage E _g (e _g), a description will be given of the relationship between the gap G. Flow rate voltage e _v, in order to correspond to the magnetic flux and velocity interlinked with the molten steel 2, it reduces the magnetic flux interlinked with the molten steel 2 the gap G is increased, the value (e _v) decreases. on the other hand,
The gap signal voltage e _g corresponds to the high frequency magnetic flux passing through the C-shaped core 4. The path of the magnetic path of this high-frequency magnetic flux is C-type core → parallel magnetic path of air and molten steel 2 → C-type core. At this time, when the gap G becomes large, the magnetic flux passing through the molten steel decreases, the magnetic resistance of the parallel magnetic path (air and molten steel) decreases, and eventually the high-frequency magnetic flux passing through the C-shaped core 4 increases and the gap signal voltage increases. The value of e _g becomes large.

Since the voltages E _g (e _g ), e _v and the gap G have the above-described relationship, the gap change correction circuit 24
The length of the gap G is obtained from the value of the gap signal voltage E _g , and the flow velocity signal e _v is corrected according to the change in the length of the gap G to obtain the flow velocity signal V. That is, even if the flow velocity is the same, the value of the flow velocity signal e _v decreases when the gap G increases, so that the flow velocity signal e _v is increased by the amount that decreases as the gap increases. Find V.

As described above, in the second embodiment, the flow velocity of the molten steel 2 can be accurately detected even if the length of the gap G changes.

<Third Embodiment> Next, a non-contact flow velocity detector according to a third embodiment of the present invention will be described with reference to FIG. The parts having the same functions as those in the second embodiment (FIG. 6) are designated by the same reference numerals, and the description of the same function parts will be omitted. In the third embodiment, the detection voltage e is controlled (suppressed) so that it is always minimized in order to prevent a malfunction caused by the detection voltage e shifting due to temperature drift or the like and exceeding the range of the signal processing system. This is to enable accurate flow velocity measurement without exceeding the range of the signal processing system.

In FIG. 8, reference numeral 30 is a 0 ° component canceling circuit composed of a multiplier 30a and subtractor 30b, 31 is a 90 ° component canceling circuit composed of a multiplier 31a and subtractor 31b, 32 is an adding circuit, and 33 is 0 °. A phase rectification circuit for components, 34 is a phase rectification circuit for 90 ° components, 35 is a control circuit for 0 ° components, and 36 is a control circuit for 0 ° components.
Of these circuits, the circuits 30, 31, 32, 35 and 36 constitute a detection voltage suppression circuit. The structure of other parts is the second
Same as the embodiment.

Next, the operation of the third embodiment will be described. In the third embodiment, the detection voltage e (= e _o + e _s + e _v ) which is a low frequency component generated in the detection coil 6 is applied to the bandpass filter 2
It is output through 2L. When the vector display is performed, the detected voltage e becomes a 0 ° component voltage e (0) and a 90 ° component voltage e (90) as shown in FIG. In the present embodiment, the following operation is performed so that a voltage corresponding to −e is applied in order to minimize the detection voltage e.

The 0 ° component canceling circuit 30 suppresses the value of the 0 ° component voltage e _o (0) of the detected voltage e and turns it to 90 °.
The component canceling circuit 31 suppresses the value of the 90 ° component voltage e (90) of the detection voltage e. The adder circuit 32 adds the voltages output from the cancel circuits 30 and 31.

The phase rectifier circuit 33 phase rectifies the voltage signal output from the adder circuit 32 to decompose the 0 ° component voltage e (0) and sends it to the arithmetic circuit 15. FIG. 3 (a)
As can be seen from (j), since the flow velocity voltage e _v has the same phase or a reverse phase with respect to the excitation voltage V, the 0 ° component voltage e _v
The flow velocity voltage in (0) indicates the flow velocity. The phase rectifier circuit 34 phase rectifies the voltage signal output from the adder circuit 32 to separate the 90 ° component voltage e (90).

The control circuit 35 detects the output value of the phase rectification circuit 33, and sets the output value to the set value (zero).
The amount of suppression in the 0 ° component cancel circuit 30 is controlled. The control circuit 36 detects the output value of the phase rectification circuit 34, and controls the suppression amount in the 90 ° component cancel circuit 31 so that the output value becomes the set value (zero). That is, the 0 ° component voltage e output from the phase rectifier circuit 33
(0) obtains the predetermined multiple (K ₁ times) the value in the control circuit 35, a multiplier 30 to K ₁ times the 0 ° component voltage K ₁ e (0)
-e (0) by multiplying the reference signal of 0 ° at a
Is obtained, and the 0 ° component voltage can be suppressed by adding this to the detected voltage e by the adder 30b. Similarly, the 90 ° component voltage e (90) output from the phase rectification circuit 34
Then, the control circuit 36 obtains a value multiplied by a predetermined value (K ₂ times),
_The doubled 90 ° component voltage K ₂ e (90) is multiplied by the multiplier 31a.
By multiplying the 90 ° reference signal at −e (9
0) is obtained, and the 90 ° component voltage can be suppressed by adding this to the detected voltage e by the adder 31b.

The arithmetic circuit 15, the difference between the suppression phase rectified voltage (0 ° component voltage _{e (0)) v 1 (} = e o + e v) and phase rectified voltage _{v 2 (= e o -e v} ) The value of is divided by 2 to obtain the flow velocity signal e _{v from} which the unbalance voltage e _o has been removed.

The gap correction circuit 24 corrects the flow velocity voltage e _v according to the value of the gap signal voltage E _g , and outputs the flow velocity signal V in which the value deviation due to the variation of the gap G is corrected.

In this embodiment, the suppressed phase rectified voltage v
₁ , v ₂ (that is, 0 ° component voltage e (0)) is calculated by the arithmetic circuit 1
5, the values of the phase rectified voltages v ₁ and v ₂ do not exceed the range of the arithmetic circuit 15. That is, if the detection voltage is not suppressed, the phase rectified voltages e _o ± _ev will drift and become saturated as shown by the dotted line in FIG. 10. However, if the detection voltage is suppressed as in the present embodiment, FIG. without phase rectified voltage e _o ± e _v is saturated as indicated by the solid line in,
Always accurate flow velocity measurement. The suppression of the detection voltage e is made to have a time constant sufficiently longer than the signal change accompanying the rotation of the detection coil 6 so that the measurement accuracy is not deteriorated. That is, as shown in FIG. 10, if the signal is suppressed, the signal is always suppressed to zero, but the accuracy is prevented from decreasing by lengthening the time constant.

[0057]

According to the present invention as specifically described in connection with the above embodiments, the static component voltage, which is a disturbance, of the voltage generated in the detection coil can be separated by phase rectification. Further, since the core and the coil are alternately positioned in the forward direction position and the reverse direction position, it is possible to cancel the unbalance voltage, which is a disturbance, and extract only the flow velocity voltage by performing subtraction and division operations. And subtraction
Since the division operation is performed, the unbalance voltage can be reliably canceled even if the value of the unbalance voltage is gradually increased / decreased, and accurate flow velocity detection can be performed even if thermal deformation occurs.

Further, since the gap variation is obtained by utilizing the high frequency magnetic flux and the flow velocity voltage is corrected according to the gap variation to obtain the flow velocity signal, accurate flow velocity detection can be performed even if the gap variation occurs.

Further, by suppressing the detection voltage, the flow velocity can be accurately detected even if a large temperature drift occurs.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram as viewed in the direction of arrows II-II in FIG.

FIG. 3 is a waveform diagram showing the states of voltage, current and magnetic flux in the first embodiment.

FIG. 4 is a waveform diagram showing the output of the phase rectifier circuit of the first embodiment.

FIG. 5 is a configuration diagram showing a modification of the first embodiment.

FIG. 6 is a configuration diagram showing a second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a relationship between a gap and a signal in the second embodiment.

FIG. 8 is a configuration diagram showing a third embodiment of the present invention.

FIG. 9 is a vector diagram showing an unbalanced voltage.

FIG. 10 is a waveform diagram showing a phase rectified voltage with and without drift suppression.

FIG. 11 is a configuration diagram showing a conventional technique.

FIG. 12 is an explanatory diagram showing the relationship between magnetic flux and current in the conventional technique.

FIG. 13 is a characteristic diagram showing the relationship between magnetic flux and current in the prior art.

FIG. 14 is a waveform diagram showing the relationship between voltage, current, and magnetic flux in the related art.

[Explanation of Codes] 1 Storage case 2 Molten steel 3 Heat insulating plate 4 C-type core 5 Excitation coil 6, 6a Detection coil 7 Rotating seal 8 Tubular body 9, 11 Gear 10 Motor 12 Oscillator 13 Amplifier 14 Phase rectification circuit 15 Arithmetic circuit 20L Low Frequency oscillator 20H High frequency oscillator 21 Summing amplifier 22L, 22H Bandpass filter 23 Rectifier circuit 24 Gap change correction circuit 30 0 ° component cancel circuit 31 90 ° component cancel circuit 32 Adder circuit 33, 34 Phase rectifier circuit 35, 36 Control circuit e Detection voltage e _v velocity voltage e _o unbalance voltage e _s still component voltage v _1, v ₂ phase rectified voltage U upstream side D downstream side e _g, E _g the gap signal voltage V flow rate signal

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tatsufumi Aoi 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Yoshio Nakajima 11 Showa-cho, Kure City, Hiroshima Prefecture No. 1 Inside Technical Research Institute of Nisshin Steel Co., Ltd. (72) Inventor Toshiaki Okimura 11-11 Showa-cho, Kure City, Hiroshima Prefecture No. 1 Inside Technical Research Institute of Nisshin Steel Co., Ltd. (72) Koji Akiyama 11-Showa Town, Kure City, Hiroshima Prefecture No. 1 Nisshin Steel Co., Ltd. Technical Research Institute

Claims (3)

[Claims] 1. An exciting coil that is excited by an AC voltage applied by an oscillator to generate a magnetic flux, and a core that guides the magnetic flux generated by the exciting coil and makes it enter a flowing conductive fluid that is an object to be inspected. And the static component voltage generated by the interlinkage of the magnetic flux generated in the direction that interferes with the magnetic flux incident on the conductive fluid, and the magnetic flux generated by the relative movement of the conductive fluid with respect to the magnetic flux incident from the core. Of the flow velocity voltage generated by the interlinkage of the magnetic field and the detection coil that detects the unbalanced voltage generated by the interlinkage of the magnetic flux generated by the excitation coil, the excitation coil, the core and the detection coil. Of the conductive fluid toward the upstream side and the other end toward the downstream side of the conductive fluid in the forward direction position, and the other end toward the upstream side of the conductive fluid and one end direction toward the downstream side of the conductive fluid. , A rotation mechanism that rotates so that they are alternately positioned, and a phase rectifier circuit that separates and removes the static component voltage by performing phase rectification on the detection voltage detected by the detection coil, and outputs the unbalanced voltage and the flow velocity voltage. , The unbalanced voltage and the flow velocity voltage are sent from the phase rectifier circuit.The unbalanced voltage and the flow velocity voltage obtained at the forward position are used to calculate the unbalanced voltage and the flow velocity voltage obtained at the reverse position. A non-contact flow velocity detector comprising: an arithmetic circuit that subtracts and divides the subtracted value by 2 to obtain a flow velocity voltage. 2. An exciting coil that is excited by applying a low-frequency AC voltage from a low-frequency oscillator and a high-frequency voltage from a high-frequency oscillator to generate a low-frequency magnetic flux and a high-frequency magnetic flux, and a low-frequency magnetic flux generated from the exciting coil. A static component voltage that is generated by interlinking the core that guides the high-frequency magnetic flux and makes it enter the flowing conductive fluid that is the object to be inspected, and the magnetic flux generated in the direction that interferes with the low-frequency magnetic flux that enters the conductive fluid. , The flow velocity voltage generated by the magnetic flux generated by the relative movement of the conductive fluid relative to the low frequency magnetic flux incident from the core and the low frequency magnetic flux generated by the exciting coil A detection coil that detects the unbalanced voltage that is generated and the gap signal voltage that is generated when the magnetic flux generated due to the high-frequency magnetic flux is interlinked. The coil, core, and detection coil are positioned in the forward direction in which one end faces the upstream side of the conductive fluid and the other end faces the downstream side of the conductive fluid, and the other end faces the upstream side of the conductive fluid, and one end is conductive. Rotating mechanism that rotates so as to be alternately positioned at the opposite position facing the downstream side of the oxidative fluid, and the phase with respect to the static component voltage, flow velocity voltage and unbalance voltage detected by the detection coil and obtained through the low frequency filter. The rectifier separates and removes the static component voltage to output the unbalanced voltage and the flow velocity voltage, and the phase rectifier circuit sends the unbalanced voltage and the flow velocity voltage. From the obtained unbalanced voltage and flow velocity voltage, subtract the unbalanced voltage and flow velocity voltage obtained at the reverse position, and divide the subtracted value by 2 to obtain the flow velocity voltage. Based on the value of the gap signal voltage detected by the detection coil and obtained through the high frequency filter, the change in the gap between the core and the conductive fluid is detected, and calculation is performed to correct the change in the flow velocity voltage due to the change in the gap. A non-contact flow velocity detector, comprising: a gap change correction circuit that obtains a flow velocity signal by correcting the flow velocity voltage extracted by the circuit. 3. An exciting coil that is excited by applying a low-frequency AC voltage from a low-frequency oscillator and a high-frequency voltage from a high-frequency oscillator to generate a low-frequency magnetic flux and a high-frequency magnetic flux, and a low-frequency magnetic flux generated from the exciting coil. A static component voltage that is generated by interlinking the core that guides the high-frequency magnetic flux and makes it enter the flowing conductive fluid that is the object to be inspected, and the magnetic flux generated in the direction that interferes with the low-frequency magnetic flux that enters the conductive fluid. , The flow velocity voltage generated by the magnetic flux generated by the relative movement of the conductive fluid relative to the low frequency magnetic flux incident from the core and the low frequency magnetic flux generated by the exciting coil A detection coil that detects the unbalanced voltage that is generated and the gap signal voltage that is generated when the magnetic flux generated due to the high-frequency magnetic flux is interlinked. The coil, core, and detection coil are positioned in the forward direction in which one end faces the upstream side of the conductive fluid and the other end faces the downstream side of the conductive fluid, and the other end faces the upstream side of the conductive fluid, and one end is conductive. Rotating mechanism that rotates so that they are alternately positioned in the reverse position facing the downstream side of the sexual fluid, and a detection voltage suppression circuit that suppresses and outputs the voltage value detected by the detection coil and obtained through the low frequency filter. , A phase rectifier circuit that outputs a voltage that separates and removes the quiescent component voltage by performing phase rectification on the voltage output from the detection voltage suppression circuit, and the voltage is sent from the phase rectifier circuit to the positive direction position. The voltage obtained at the reverse position is subtracted from the voltage obtained at the time of, and the subtraction value is divided by 2 to obtain the flow velocity voltage. Based on the value of the gap signal voltage obtained, the change in the gap between the core and the conductive fluid is detected, and the flow velocity voltage taken out by the arithmetic circuit is corrected so that the change in the flow velocity voltage due to the gap change is corrected. A non-contact flow velocity detector comprising: a gap change correction circuit that obtains a signal;