JP3188146B2 - Non-contact flow velocity detector - Google Patents

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, and is effective when applied to, for example, detecting the flow velocity of molten steel in a mold of a continuous casting facility.

[0002]

2. Description of the Related Art A non-contact flow velocity detector (eddy current 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 a conventional non-contact flow velocity detector will be described with reference to FIG.

[0003] As shown in FIG.
Magnetic flux Φ _oOccurs. pair
The detection coils 03 and 04 have the magnetic flux Φ in the axial direction A._oWhen
It is arranged on the exciting coil 01 in a state of being orthogonal. Inspection
The output coils 03 and 04 are differentially connected, and the detection coils
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 the table of molten steel 06
It is mounted so that it is incident perpendicular to the surface. Molten steel
06 flows in the arrow B direction.

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 diagram, FIG. 12 which shows molten steel 06 from the front side, and FIG. 13 which is a waveform diagram. .

[0005] flux [Phi _o generated by the excitation coil 01, by the molten steel 06 interlinked, eddy current i _s flows through 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.

[0006] It should be noted that in accordance with the law of Lenz, the magnetic flux Φ _s to prevent the magnetic flux Φ _o is caused 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 It shows the state as seen from.

Referring now to FIG. 14, the relationship among voltage, current, and magnetic flux generated in a conventional non-contact flow velocity detector is summarized. (A) An alternating voltage V is applied to the exciting coil 01 (FIG. 14A). (B) A current i delayed by 90 ° from the voltage V flows through the exciting coil 01 (FIG. 14B). (C) to the exciting coil 01, the current i and the phase of the magnetic flux [Phi _o occurs (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) in the molten steel 06, by the magnetic flux [Phi _o is incident,
Flowing eddy current i _s (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)). Here, 1 is the length of the conductor, that is, the size of the coil. The (g) an eddy current i _s, the magnetic flux [Phi _s interfering with the magnetic flux [Phi _o occurs (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) in the detection coil 03, 04 is a magnetic flux [Phi _s is the voltage e _s caused by interlinking (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) and (j), the differentially connected detection coils 03 and 04
A detection voltage e expressed by the following equation (1) is generated.

[0009]

(Equation 1)

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

That is, the unbalanced voltage e _o (= −ndΦ)
_o / dt), because is caused by imbalance of the detection coil 03 and 04, a voltage generated in the detection coil 03 and 04 by the magnetic flux [Phi _o eliminate this imbalance almost equal unbalance voltage e _o is The detection coils 03 and 04 are installed so as to be minimum, and the remaining 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. By utilizing the fact that the phases differ by 90 °, 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 extracted. .

[0013]

The above-mentioned prior art
Then, there were the following problems. (1) Excitation coil 01 and detection coil 0 due to thermal deformation
If the positional relationship with 3,04 shifts, large imbalance
Voltage e_oOccurs. This unbalanced voltage e_oIs the current
Pressure e_vOut of 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 So this Ann
Balance voltage e_oCan cause drifting
Was. (2) The 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 not constant.
However, the flow velocity voltage e_vOf the flow rate changes, and the flow velocity is detected.
Accuracy was bad. (3) Unbalance voltage e due to temperature drift etc._oIs large
This voltage e _oIs the range of the signal processing system.
There was a possibility that the measurement would be impossible and measurement would be impossible.

SUMMARY OF THE INVENTION In view of the above prior art, the present invention provides a non-contact molten steel flow velocity capable of reliably separating and removing an unbalanced voltage, accurately detecting a flow velocity even if there is a gap change, and measuring even if a temperature drift or the like occurs. It is an object to provide a detector.

[0015]

According to a first aspect of the present invention, there is provided an excitation coil which is excited by applying an AC voltage from an oscillator to generate a magnetic flux, and guides a magnetic flux generated by the excitation coil. A static component voltage generated by interlinking a core that is incident on a flowing conductive fluid as an object to be inspected with a magnetic flux generated in a direction that obstructs a magnetic flux incident on the conductive fluid, and a magnetic flux incident from the core And a detection coil that detects the flow velocity voltage generated by the magnetic flux generated by the relative movement of the conductive fluid and the unbalanced voltage generated by the magnetic flux generated by the exciting coil interlinked. The excitation coil, the core, and the detection coil, a positive position where one end thereof is directed to the upstream side of the conductive fluid and the other end is directed to the downstream side of the conductive fluid, and the other end is positioned upstream of the conductive fluid. A rotating mechanism that rotates alternately to the opposite position where one end faces the downstream side of the conductive fluid, and a stationary component voltage is separated by performing phase rectification on the detection voltage detected by the detection coil. The phase rectification circuit that removes and outputs the unbalanced voltage and the flow velocity voltage, and 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 direction position, And an arithmetic circuit for subtracting the unbalanced voltage obtained at the reverse position and the flow velocity voltage, and dividing the subtracted value by 2 to extract the flow velocity voltage.

The present invention also provides an excitation coil which 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; The low-frequency magnetic flux and high-frequency magnetic flux that are introduced into the conductive fluid that is the object to be inspected flow through the core, and the magnetic flux generated in the direction that interferes with the low-frequency magnetic flux that is incident on the conductive fluid is generated by interlinkage. A static component voltage, and a 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,
A detection coil for detecting an unbalance voltage generated by interlinking of low-frequency magnetic flux generated by the excitation coil and a gap signal voltage generated by interlinkage of magnetic flux generated by high-frequency magnetic flux, and an excitation coil , The core and the detection coil, one end of which is directed to the upstream side of the conductive fluid, the other end is directed to the downstream side of the conductive fluid, and the other end is directed to the upstream side of the conductive fluid, and one end is conductive. A rotation mechanism for rotating the fluid so that it alternately moves to the opposite 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. A phase rectifier circuit that separates and removes the static component voltage to output an unbalanced voltage and a flow velocity voltage, and the unbalanced voltage and the flow velocity voltage are sent from the phase rectification circuit. Then, the flow velocity voltage is obtained by subtracting the unbalanced voltage and the flow velocity voltage obtained at the reverse position from the unbalanced voltage and the flow velocity voltage obtained at the forward position, and dividing the subtracted value by 2. A gap change between the core and the conductive fluid is detected based on a calculation circuit to be extracted and a gap signal voltage value detected by a detection coil and obtained through a high-frequency filter, and a change in a flow velocity voltage accompanying the gap change is corrected. A gap change correction circuit for obtaining a flow velocity signal by correcting the flow velocity voltage taken out by the arithmetic circuit,
Is characterized by the following.

Further, according to the present invention, an excitation coil which is excited by application of 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; The low-frequency magnetic flux and high-frequency magnetic flux that are introduced into the conductive fluid that is the object to be inspected flow through the core, and the magnetic flux generated in the direction that interferes with the low-frequency magnetic flux that is incident on the conductive fluid is generated by interlinkage. A static component voltage, and a 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,
A detection coil for detecting an unbalance voltage generated by interlinking of low-frequency magnetic flux generated by the excitation coil and a gap signal voltage generated by interlinkage of magnetic flux generated by high-frequency magnetic flux, and an excitation coil , The core and the detection coil, one end of which is directed to the upstream side of the conductive fluid, the other end is directed to the downstream side of the conductive fluid, and the other end is directed to the upstream side of the conductive fluid, and one end is conductive. A rotation mechanism that rotates so as to be alternately positioned at a reverse position facing the downstream side of the fluid, a detection voltage suppression circuit that suppresses and outputs a voltage value detected by a detection coil and obtained through a low frequency filter, Phase rectification is performed on the voltage output from the detection voltage suppression circuit to output a voltage obtained by separating and removing the static component voltage, and a voltage is sent from the phase rectification circuit. An arithmetic circuit for subtracting the voltage obtained at the reverse position from the voltage obtained at the forward position and dividing the subtracted value by 2 to obtain the flow velocity voltage; and a high-frequency filter detected by the detection coil A gap change between the core and the conductive fluid is detected based on the value of the gap signal voltage obtained through the above, and the flow velocity voltage taken out by the arithmetic circuit is corrected so as to correct the flow velocity voltage change accompanying the gap change. A gap change correction circuit for obtaining a flow velocity signal
Is characterized by the following.

In the first aspect, since the core and the coil are alternately located at the forward direction position and the reverse direction position, after the detection voltage is phase-rectified, the value at the forward direction position and the value at the reverse direction position are changed. By calculating the value of the time, the flow velocity voltage can be obtained.

According to the second aspect, even if the flow velocity voltage changes due to the gap change, accurate flow velocity detection can be performed.

In the third aspect of the present invention, the flow rate can be detected even when a large temperature drift occurs by controlling the value of the unbalance 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 for detecting molten steel flow velocity. As shown in FIG.
, That is, the surface facing the molten steel 2 is closed by a non-conductive heat insulating plate 3. A C-shaped core 4 is provided 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.

At the upper end of the storage case 1, a rotary seal 7 is provided.
The pipe 8 is rotatably connected via a pipe, and a cooling medium (air or the like) is sent into the storage case 1 through the pipe 8 to perform cooling.

Further, a gear 9 is fixed to the upper part of the storage case 1, and the torque of the motor 10 is transmitted to the gear 9 via the gear 11. Therefore, by rotating the motor 10 forward and backward, the storage case 1 and thus the core 4 and the coils 5 and 6 rotate forward and backward. As a result, as shown in FIGS. 2 (a) and 2 (b) which are II-II cross sections in FIG.
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 in the forward direction (FIG. 2A) where the downstream side D is located on the downstream side of the molten steel. It may be a reverse position (FIG. 2B) in which the upstream side U is located on the molten steel upstream side and the upstream side U is located on the downstream side of the molten steel.

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

In this embodiment, the motor 10 is rotated forward and backward to change the positions of the core 4 and the coils 5 and 6 of this detector to the forward position (FIG. 2A) and the reverse position (FIG. 2B). )), The flow rate is detected while switching to replacement. At this time, the voltage, current, and magnetic flux generated in the detector are as shown in FIG. In FIG. 3, the waveforms in the (positive) column show the waveforms at the forward position, and the waveforms in the (reverse) column show the waveforms at the reverse position.

To further explain the waveform of FIG. 3, when an AC voltage V is applied to the exciting coil 5 (a), a voltage i delayed by 90 ° from the voltage V flows through 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).

The molten steel 2, eddy current i _s is caused by the magnetic flux [Phi _o is incident with (e), the current i _v flows by moving the magnetic flux [Phi _o relative molten steel 2 is moved (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 static component voltage e _s is generated due to the interlinkage of the magnetic flux Φ _s (i), and the magnetic flux Φ
_iv flow speed voltage e _v is generated by interlinking.

As can be seen from FIGS. 3 (d), (i) and (j), a detection voltage e expressed by 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 is, the static component voltage e _s is equal to the flow velocity voltage e _v
Since there is a phase difference of 90 ° with respect to
(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 rectifier 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).

[0034] That is, by changing the detector in forward and reverse directions, the flow rate signal e _v is the + direction, - (see FIG. 3 (j)) varies in the direction, the unbalance voltage e _o is not changed, the upper The relations of equations (3) and (4) occur. Note that the unbalance voltage e _o gradually increases and decreases due to thermal deformation, but is the same even when the detector is changed in the forward and reverse directions at substantially the same time, which is expressed here as “e _o does not change”. 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 arithmetic unit 15 divides the value obtained by subtracting the minimum value (ie, v ₂ ) from the maximum value (ie, v ₁ ) of the voltage output from the phase rectification circuit 14 by 2
Than it is possible to extract only the flow rate voltage e _v to remove unbalance voltage e _o. Moreover even if unbalance voltage e _o is gradually increased, decreasing the thermal deformation or the like, since the value of the voltage e _o is 1 cycle changes from a positive direction in the opposite direction is almost the same, the calculation of the equation (5) By doing
The unbalance voltage e _o can be almost completely removed.

As described above, according to the first embodiment, even if the positional relationship of the detection coil 6 becomes unbalanced due to thermal deformation or the like, the unbalanced voltage _eo is reliably removed and the flow velocity voltage e.
_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 6a is arranged at the center inside the C-shaped core 4. The configuration and operation of the other parts are the same as in the first embodiment.

<Second Embodiment> A non-contact flow velocity detector according to a second embodiment of the present invention will be described with reference to FIG. Portions that perform the same functions as in the first embodiment (FIGS. 1 and 2) are denoted by the same reference numerals, and the description of the same function units will be omitted. In the second embodiment, a correction function for a gap change is added.

In the second embodiment, a low frequency (100 to 1000 Hz) AC voltage generated by the low frequency oscillator 20L and a high frequency (10 to 100 kHz) generated by the high frequency oscillator 20H are used.
The AC voltage is added and amplified by the addition amplifier 21 and then applied to the exciting coil 5. Therefore, a low-frequency current and a high-frequency current flow through the excitation coil 5 to excite the excitation 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 coil 6 has a detection voltage e (= _eo + _es ±) due to the low-frequency magnetic flux.
e _v) and the gap signal voltage e _g by the high-frequency magnetic flux occurs. Also in the detector of the second embodiment, the core 4 and the coils 5, 6 detect the flow velocity while the forward position and the reverse position are alternately switched, as in the first embodiment.

The bandpass filter 22L passes a voltage signal in a low frequency range (100 to 1000 Hz). Therefore, the detection voltage e (= _eo + _es ± _ev ) passes through the bandpass filter 22.

The phase rectifier circuit 14 and the arithmetic circuit 15
The same function as the embodiment is performed. That is, the phase rectifier circuit 14 separates and removes the static component voltage e _s by performing phase rectification, and the arithmetic circuit 15 outputs the phase rectified 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 band-pass filter 22H passes a voltage signal in a high frequency range (10 to 100 kHz). Thus the gap signal voltage e _g is a band-pass filter 22H
Through, further comprising a DC gap signal voltage E _g by the rectifier circuit 23.

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,
Gap signal voltage e _g corresponds to a 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 increases, 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 increases.

The voltage E _g (e _g), since e _v and the gap G is in a relationship as described above, the gap change correction circuit 24,
The length of the gap G is determined from the value of the gap signal voltage E _g , and the flow velocity signal _ev is corrected according to the change in the length of the gap G to determine the flow velocity signal V. That is, even the flow rate is the same, for example, because the gap G becomes the value of the flow rate signal e _v is greatly reduced, and a correction to increase the amount corresponding flow rate signal e _v was reduced in accordance with the gap increases, the flow rate signal Find V.

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

<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 performing the same functions as those in the second embodiment (FIG. 6) are denoted by the same reference numerals, and the description of the same function units will be omitted. The description will focus on those specific to the third embodiment. The third embodiment controls (suppresses) the detection voltage e so as to be always minimized in order to prevent a malfunction due to the detection voltage e shifting due to temperature drift or the like and exceeding the range of the signal processing system. The flow velocity can always be accurately measured without exceeding the range of the signal processing system.

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

Next, the operation of the third embodiment will be described. In the third embodiment, the detection voltage e (= _eo + _es + _ev ), which is a low frequency component generated in the detection coil 6, is applied to the bandpass filter 2.
Output through 2L. When the detection voltage e is represented by a vector, it 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 as to apply a voltage corresponding to -e in order to minimize the detection voltage e.

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

The phase rectifier circuit 33 decomposes the 0 ° component voltage e (0) by phase rectifying the voltage signal output from the adder circuit 32 and sends it to the arithmetic circuit 15. FIG. 3 (a)
As can be seen from (j), since the flow rate voltage e _v in phase or reversed phase with respect to the excitation voltage V, 0 ° component voltage e
The flow velocity voltage in (0) indicates the flow velocity. Further, the phase rectifier circuit 34 separates the 90 ° component voltage e (90) by performing phase rectification on the voltage signal output from the adder circuit 32.

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

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 is divided by 2 to obtain the flow rate signal e _v removing the unbalance voltage e _o.

[0055] gap correction circuit 24 corrects the flow rate voltage e _v in accordance with the value of the gap signal voltage E _g, and outputs a flow rate signal V obtained by correcting the value shift due to variations in the gap G.

In this embodiment, the suppressed phase rectified voltage v
₁ , v ₂ (ie, 0 ° component voltage e (0))
5, the values of the phase rectified voltages v ₁ and v ₂ do not exceed the range of the arithmetic circuit 15. That Without suppression of the detection voltage, the phase rectified voltage e _o ± e _v as indicated by a dotted line in FIG. 10 but is saturated with drift, the suppression of the detection voltage as in the present embodiment, FIG. 10 without phase rectified voltage e _o ± e _v is saturated as indicated by the solid line in,
Accurate flow velocity measurement is always possible. Note that the detection voltage e is suppressed by giving a time constant that is sufficiently longer than a signal change due to the rotation of the detection coil 6 so as not to lower the measurement accuracy. That is, as shown in FIG. 10, when the suppression is performed, the signal is always suppressed to become zero, but the accuracy is prevented by lowering the time constant.

[0057]

According to the present invention, as described above in detail with the embodiment, the stationary component voltage which is a disturbance among the voltages generated in the detection coil can be separated by performing phase rectification. Further, since the core and the coil are alternately positioned at the forward position and the reverse position, the unbalance voltage which is a disturbance can be canceled by performing the subtraction and the division operation, and only the flow velocity voltage can be extracted. Moreover, subtraction
Since the division operation is performed, the imbalance voltage can be reliably canceled even if the value of the unbalance voltage gradually increases / decreases, and accurate flow velocity detection can be performed even if thermal deformation occurs.

Further, since the gap fluctuation is obtained by using the high-frequency magnetic flux and the flow velocity voltage is corrected in accordance with the gap fluctuation to obtain the flow velocity signal, accurate flow velocity detection can be performed even if the gap fluctuation occurs.

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

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram viewed from the direction of arrows II-II in FIG. 1;

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

FIG. 4 is a waveform chart showing an 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 phase rectified voltages when drift is suppressed and when drift is not suppressed.

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

FIG. 12 is an explanatory diagram showing a relationship between a magnetic flux and a current in the related art.

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Storage case 2 Molten steel 3 Heat insulation board 4 C-type core 5 Excitation coil 6, 6a Detection coil 7 Rotary seal 8 Tube 9, 11 Gear 10 Motor 12 Oscillator 13 Amplifier 14 Phase rectification circuit 15 Arithmetic circuit 20L Low frequency oscillator 20H High frequency oscillator DESCRIPTION OF SYMBOLS 21 Addition amplifier 22L, 22H Band pass filter 23 Rectifier circuit 24 Gap change correction circuit 300 0 degree component cancellation circuit 31 90 degree component cancellation circuit 32 Addition circuit 33, 34 Phase rectification circuit 35, 36 Control circuit e Detection voltage _ev Flow 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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsufumi Aoi 4-62-22 Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Yoshio Nakajima 11th Showacho, Kure-shi, Hiroshima Prefecture No. 1 Inside Nisshin Steel Co., Ltd.Technology Research Laboratory (72) Inventor Toshiaki Okimura 11-1 Showa-cho, Kure-shi, Hiroshima Prefecture Inside Nisshin Steel Co., Ltd.Technology Research Laboratory (72) Inventor Koji Akiyama Showa-cho, Kure-shi, Hiroshima Prefecture No. 11 in Nisshin Steel Co., Ltd. Technical Research Institute (56) References JP-A-8-201412 (JP, A) JP-A-2-311766 (JP, A) JP-A-5-297012 (JP, A) (Japanese) Shokai 49-73474 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01P 5/08

Claims (3)

(57) [Claims] 1. An excitation coil which is excited by applying an AC voltage from an oscillator to generate a magnetic flux, and a core which guides the magnetic flux generated by the excitation coil and makes it incident on a flowing conductive fluid as an object to be inspected. And the static component voltage generated by the interlinkage of the magnetic flux generated in the direction obstructing the magnetic flux incident on the conductive fluid, and the magnetic flux generated by the conductive fluid moving relative to the magnetic flux incident from the core The detection coil that detects the flow velocity voltage generated by interlinking the magnetic flux and the unbalanced voltage generated by the magnetic flux generated by the excitation coil interlinks the excitation coil, the core, and the detection coil. A forward position where the other end faces the upstream side of the conductive fluid and the other end faces the downstream side of the conductive fluid, and a reverse position where the other end faces the upstream side of the conductive fluid and one end faces the downstream side of the conductive fluid. A rotation mechanism that rotates so as to be positioned alternately, and a phase rectification circuit that separates and removes the static component voltage by performing phase rectification on the detection voltage detected by the detection coil to output an unbalanced voltage and a flow velocity voltage. The unbalanced voltage and the flow velocity voltage are sent from the phase rectifier circuit, and the unbalanced voltage and the flow velocity voltage obtained in the reverse direction are calculated from the unbalanced voltage and the flow velocity voltage obtained in the forward position. A non-contact flow velocity detector, comprising: an arithmetic circuit for subtracting the flow rate voltage by dividing the subtracted value by 2; 2. An excitation coil which 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, a low-frequency magnetic flux generated by the exciting coil, The core that guides the high-frequency magnetic flux and makes it enter the flowing conductive fluid that is the test object, and the static component voltage that is generated by interlinking the magnetic flux generated in the direction that blocks the low-frequency magnetic flux that enters the conductive fluid, and 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 are interlinked. A detection coil for detecting an unbalanced voltage generated and a gap signal voltage generated by a magnetic flux generated by the high-frequency magnetic flux interlinking; One end of the coil, the core, and the detection coil are in the forward direction with one end facing the upstream of the conductive fluid and the other end is facing the downstream of the conductive fluid, and the other end is facing the upstream of the conductive fluid and one end is conductive. A rotating mechanism that rotates alternately to the opposite position facing the downstream side of the ionic fluid, and a phase for the stationary component voltage, flow velocity voltage, and unbalance voltage detected by the detection coil and obtained through the low frequency filter. A phase rectifier circuit that separates and removes the quiescent component voltage by rectification to output an unbalanced voltage and a flow velocity voltage, and an unbalanced voltage and a flow velocity voltage are sent from the phase rectification circuit. An operation for extracting the flow velocity voltage by subtracting the unbalanced voltage and the flow velocity voltage obtained at the reverse position from the obtained unbalanced voltage and the flow velocity voltage and dividing the subtracted value by two. Based on the value of the gap signal voltage detected by the detection coil and obtained through the high frequency filter, a change in the gap between the core and the conductive fluid is detected, and a calculation is performed to correct the change in the flow velocity voltage accompanying the change in the gap. A gap change correction circuit for correcting a flow velocity voltage taken out by a circuit to obtain a flow velocity signal; 3. An excitation 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 by the exciting coil. The core that guides the high-frequency magnetic flux and makes it enter the flowing conductive fluid that is the test object, and the static component voltage that is generated by interlinking the magnetic flux generated in the direction that blocks the low-frequency magnetic flux that enters the conductive fluid, and 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 are interlinked. A detection coil for detecting an unbalanced voltage generated and a gap signal voltage generated by a magnetic flux generated by the high-frequency magnetic flux interlinking; One end of the coil, the core, and the detection coil are in the forward direction with one end facing the upstream of the conductive fluid and the other end is facing the downstream of the conductive fluid, and the other end is facing the upstream of the conductive fluid and one end is conductive. A rotation mechanism for alternately rotating the fluid at a reverse position facing the downstream side of the sexual fluid, a detection voltage suppression circuit for suppressing and outputting a voltage value detected by a detection coil and obtained through a low frequency filter. A phase rectification circuit that separates and removes the quiescent component voltage by performing phase rectification on the voltage output from the detection voltage suppression circuit, and a voltage that is sent from the phase rectification circuit to the positive position. An arithmetic circuit for extracting the flow velocity voltage by subtracting the voltage obtained at the reverse position from the voltage obtained at the time of the reverse direction and dividing the subtracted value by 2; A gap change between the core and the conductive fluid is detected based on the value of the gap signal voltage obtained, and the flow velocity voltage extracted by the arithmetic circuit is corrected so as to correct the flow velocity voltage change accompanying the gap change. A non-contact flow velocity detector, comprising: a gap change correction circuit for obtaining a signal;