JP6033749B2 - Axial displacement detector for canned motor - Google Patents

Description

  The present invention relates to an axial displacement detection device for a can motor that detects axial displacement of a rotor that rotates via a bearing relative to a stationary portion of the can motor.

  2. Description of the Related Art Conventionally, in order to manage bearing wear of a rotor of a canned motor, a differential transformer type axial displacement detection device that detects the axial position of the rotor has been proposed.

  In this axial direction displacement detection device, the magnetic body of the differential transformer is fixed to the rotor, and the coil portion having the primary coil and the secondary coil of the differential transformer surrounds the outer periphery of the magnetic body and the stationary portion of the canned motor. It is fixed to. Then, an AC voltage with a constant frequency and a constant voltage is applied to the primary coil, and the magnetic material moves in the axial direction together with the rotor, so that a voltage signal proportional to the axial movement distance of the rotor is output from the secondary coil. Is done. An axial bearing wear amount corresponding to the voltage signal output from the secondary coil is indicated by an indicator (see, for example, Patent Document 1).

Japanese Patent No. 3032383

  The canned motor circulates the specified liquid (such as the pump handling liquid when the canned motor is combined with the pump) between the rotor and the stator to lubricate and cool the bearing. In the case of liquid, the temperature of the canned motor including the differential transformer and the rotor changes.

  In the conventional axial displacement detection device, since the influence on the temperature change is not taken into account, there is a problem that the detection of the rotor position is deviated and the bearing wear cannot be managed accurately.

  The present invention has been made in view of these points, and an object of the present invention is to provide an axial displacement detection device for a can motor that can accurately detect the position of the rotor even if the temperature changes.

  The axial displacement detection device for a canned motor according to claim 1, wherein the canal motor axial displacement detection device detects an axial displacement of a rotor rotating via a bearing relative to a stationary portion of the canned motor. A coil portion having a primary coil and a pair of secondary coils for detection in the axial direction and a magnetic body disposed inside the coil portion, the magnetic body being fixed to the rotor, and the coil portion being A differential transformer surrounding the outer periphery of the magnetic body and fixed to the stationary part; an oscillation circuit for exciting the primary coil; a current flowing in the primary coil excited by the oscillation circuit; and a secondary coil A detection circuit for detecting the generated voltage, temperature detection means for detecting the temperature inside the canned motor, and a rate of change of the current value flowing through the primary coil with respect to the initial value is obtained. First calculation means for correcting the current value generated in the secondary coil at the rate of change, and determining the position of the rotor based on the corrected current value, and correcting the dimensional change due to the temperature of the rotor A calculation unit having a second calculation unit that calculates a constant according to the temperature detected by the temperature detection unit, and corrects the position of the rotor determined by the first calculation unit with the correction constant; And an output unit that outputs the position of the rotor obtained by the calculation unit.

  The axial displacement detection device for a canned motor according to claim 2 is the axial displacement detection device for a canned motor according to claim 1, wherein the calculation unit is a relationship between a temperature and a correction constant for a dimensional change amount of the rotor. Is stored in advance, and a correction constant is selected and determined in accordance with the temperature detected by the temperature detecting means.

  The axial displacement detection device for a canned motor according to claim 3 is the axial displacement detection device for a canned motor according to claim 1 or 2, wherein the temperature detecting means is based on a relationship between a temperature and a current flowing through the primary coil. Based on this, the temperature corresponding to the current flowing through the primary coil is detected.

  According to the axial displacement detection apparatus for a canned motor according to claim 1, the variation of the output characteristic due to the temperature of the differential transformer is corrected by the first calculating means, and the dimensional change due to the temperature of the rotor is corrected by the second calculating means. That is, by correcting fluctuations in the position of the rotor, the position of the rotor can be accurately detected even if the temperature changes.

  According to the axial displacement detection device for a canned motor according to claim 2, in addition to the effects of the axial displacement detection device for the canned motor according to claim 1, the temperature and the dimensional change of the rotor according to the model of the canned motor. By storing the relationship between the amount and the correction constant in advance, it is possible to select an appropriate correction constant according to the temperature and to accurately detect the position of the rotor.

  According to the axial displacement detection device for a canned motor according to claim 3, in addition to the effect of the axial displacement detection device for a canned motor according to claim 1 or 2, it is possible to detect a temperature according to the current flowing through the primary coil. Therefore, another temperature sensor or the like can be omitted.

It is a circuit diagram of the axial direction displacement detection apparatus of the canned motor which shows one embodiment of this invention. It is sectional drawing of the axial direction displacement detection apparatus of a canned motor same as the above. It is sectional drawing of the canned motor pump using a canned motor same as the above. It is a graph which shows the relationship between the electric current of the primary coil of the differential transformer of the same axial direction displacement detection apparatus, and the voltage of a secondary coil. It is a graph which shows the relationship between the temperature of the differential transformer of the axial direction displacement detection apparatus same as the above, and the electric current of a primary coil.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 shows a cross-sectional view of a canned motor pump using a canned motor. The canned motor pump 10 is configured by integrally connecting a canned motor 11 and a pump 12 in a liquid-tight manner.

  In the canned motor 11, a stator 15 formed by winding a stator winding 14 around a stator core 13 is inserted into a stator frame 16, and a thin cylindrical stator can 17 is attached to the inner peripheral surface of the stator 15. Insert both ends of the rotor in a liquid-tight manner on the stator frame 16, and insert the rotating shaft 21 into the rotor 20 formed by attaching the rotor conductor 19 to the rotor core 18. A thin cylindrical rotor can 22 is attached to the surface, and a rotor 20 is disposed opposite to the stator 15 via a can clearance 23 between the stator can 17 and the rotor can 22, and the rotating shaft 21 is a bearing. The bearings 26 and 27 mounted on the boxes 24 and 25 are pivotally supported via sleeves 28 and 29 and thrust collars 30 and 31.

  The pump 12 has an impeller 32 attached to the rotary shaft 21, surrounds the impeller 32, and a pump casing 33 is attached to the stator frame 16 in a liquid-tight manner.

  The canned motor pump 10 guides a part of the liquid handled on the pump discharge side 34 into the canned motor 11 through the circulation pipe 35, lubricates the rear bearing 27, and connects the stator can 17 and the rotor can 22 with each other. A configuration is adopted in which the stator 15 and the rotor 20 are cooled by flowing through the can gap 23, the front bearing 26 is lubricated, and then returned to the pump suction side 36 from the balance hole of the impeller 32 and circulated. . Further, a stationary part 37 is constituted by the stator 15, the bearing housings 24, 25, the pump casing 33, etc., and the rotating part 38 is constituted by the rotor 20, the rotating shaft 21, the sleeves 28, 29, the thrust collars 30, 31 and the impeller 32, etc. It is configured.

  Next, the axial displacement detection device 40 applied to the canned motor 11 will be described with reference to FIG. A differential transformer 46 is constituted by a coil portion 44 including a primary coil 41 for excitation, a pair of secondary coils 42 and 43 for detection in the axial direction, and a magnetic body 45 disposed inside the coil portion 44. ing.

  The coil portion 44 is mounted in the differential transformer case 47, and the lead wire 50 is drawn out from the wiring lead-in port 48 of the differential transformer case 47 through the seal member 49, and the detection body can 51 made of non-corrosion resistant steel is formed. The detection unit 52 is configured by being inserted into the inner peripheral surface of the coil unit 44 and having both end edges thereof liquid-tightly welded to the differential transformer case 47. The detection unit 52 is fastened and fixed in a liquid-tight manner by a bolt 54 via a seal member 53 to a rear bearing box 25 formed in a hollow shape, and a circulation pipe 35 is connected between the detection unit 52 and the pump discharge side 34. Has been.

  The magnetic body 45 is integrally welded to an auxiliary shaft 55 made of nonmagnetic corrosion-resistant steel having a male threaded portion 55a, and a detection object can 56 made of nonmagnetic corrosion-resistant steel is welded to the outer periphery of the magnetic body 45 in a liquid-tight manner. Thus, the detected object 57 is configured. The detected object 57 is screwed and fixed to the rear end portion of the rotary shaft 21 and is disposed inside the detection portion 52 corresponding to the coil portion 44.

  The lead wire 50 of the detection unit 52 is connected to the indicator 58.

  As shown in FIG. 1, the indicator 58 is excited by an oscillation circuit 61 as an excitation circuit that excites the primary coil 41 of the differential transformer 46 with an AC power source having a constant frequency and a constant voltage. A detection circuit 62 that detects a current flowing through the primary coil 41 and a voltage generated in the pair of secondary coils 42 and 43, and calculates the position of the rotor 20, that is, the amount of axial bearing wear, based on the output of the detection circuit 62 A calculation unit 63 and an output unit 64 that outputs an instruction value corresponding to the axial bearing wear amount obtained by the calculation unit 63 are provided.

  When the primary coil 41 is excited by the oscillating circuit 61, an alternating magnetic flux having the magnetic body 45 as the center of the magnetic circuit is generated, so that an alternating induction voltage is generated in the pair of secondary coils 42 and 43, respectively. One of these two AC induced voltages increases when the magnetic body 45 moves up and down in FIG. 1, and the other decreases. In the detection circuit 62, the AC voltages from the pair of secondary coils 42 and 43 are half-wave rectified, respectively, and a detection signal corresponding to the difference between the two voltages after rectification is output to the arithmetic unit 63. The computing unit 63 computes the position of the rotor 20, that is, the axial bearing wear amount based on the detection signal, and outputs an instruction value corresponding to the axial bearing wear amount to the output unit 64.

  The calculation unit 63 is a first calculation unit (first correction unit) that calculates the position of the rotor 20 by correcting fluctuations in the output characteristics due to the temperature of the differential transformer 46, and the dimensions according to the temperature of the rotor 20. The second calculation means (second correction means) for calculating the position of the rotor 20 by correcting the change, i.e., the fluctuation of the position of the rotor 20, and the temperature inside the canned motor 11, the specified liquid (pump 12 The function of the temperature detection means which detects the temperature of the (handling liquid).

  Here, the 1st calculating means of the calculating part 63 is demonstrated. The output of the differential transformer 46 is constant when the position of the magnetic body 45 is unchanged at a constant temperature. However, when the temperature of the differential transformer 46 changes due to the temperature of the specification liquid flowing inside the canned motor 11, the resistance value of the primary coil 41 changes, so that the current flowing through the primary coil 41 increases or decreases. This leads to fluctuations in the voltage generated in the secondary coils 42 and 43.

  Due to the structure of the differential transformer 46, when the current flowing through the primary coil 41 becomes k times, the voltage generated in the secondary coils 42 and 43 also becomes k times. That is, as shown in FIG. 4, since the rate of change of the current flowing in the primary coil 41 and the rate of change of the voltage generated in the secondary coils 42 and 43 are substantially equal, the rate of change of the current flowing in the primary coil 41 is based on the rate of change. It is possible to obtain a correction value for the voltage generated in the secondary coils 42 and 43.

  Therefore, when the current flowing through the primary coil 41 becomes k times the initial value due to the temperature change, the voltage generated in the secondary coils 42 and 43 is also k times, so that the current generated in the secondary coils 42 and 43 is generated. Correction can be made by multiplying the detected voltage value by k.

  Therefore, the first calculation means of the calculation unit 63 obtains the rate of change of the current value flowing through the primary coil 41 with respect to the initial value, and corrects the current value generated in the secondary coils 42 and 43 by using this rate of change. The position of the rotor 20 is obtained based on the current value.

  Further, the second calculation means of the calculation unit 63 will be described. When the temperature of the specification liquid flowing inside the canned motor 11 changes, the rotor 20 expands and contracts due to thermal expansion. Therefore, the moving range in the axial direction of the magnetic body 45 with respect to the differential transformer 46 changes relatively, and the rotor 20 Deviation occurs in the calculation result of the position.

  Therefore, in the second calculation means of the calculation unit 63, a correction constant for the dimensional change due to the temperature of the rotor 20 is obtained according to the temperature detected by the temperature detection means, and this correction constant is obtained by the first calculation means. The position of the rotor 20 is corrected.

  For example, for each model of the canned motor 11, a correction constant for the dimensional variation of the rotor 20 at each temperature is calculated from the relationship between the temperature and the dimensional variation of the rotor 20, and the temperature for each model of the canned motor 11 is calculated. And the correction constant are stored in advance in a table of the storage unit included in the calculation unit 63. Then, referring to the table, the correction constant can be selected and determined according to the temperature detected by the temperature detecting means.

  Further, as shown in FIG. 5, the temperature detection means of the calculation unit 63 has a linear relationship between the temperature of the differential transformer 46 and the current of the primary coil 41. Therefore, the current of the differential transformer 46 is determined from the current flowing through the primary coil 41. The temperature, that is, the temperature of the specification liquid can be detected by calculation. The temperature detecting means is not limited to detecting the temperature from the current flowing through the primary coil 41, and may be detected using a temperature sensor or the like.

  Next, a specific example of processing by the calculation unit 63 will be described.

First, before the operation of the canned motor pump 10, each parameter in the initial state of the canned motor pump 10 (the canned motor pump 10 is stopped, the bearing is not worn, and the specification liquid temperature is normal temperature) is measured by the indicator 58. Each measured value is, for example,
Specification liquid temperature: 5 ℃
Current flowing through the primary coil 41: I ₀ = 6.471 mA
Voltage generated in secondary coils 42 and 43 (per front): V _F0 = 7.3 mV
Voltage generated in secondary coils 42 and 43 (per rear): V _R0 = 137.3 mV
Suppose that The front hit means a state in which the rotor 20 hits the front bearing 26, and the rear hit means a state in which the rotor 20 hits the rear bearing 27. Further, it is assumed that the axial play value d of the rotor 20 is 2.61 mm.

Based on these values, the position X of the rotor 20 is
Per front: X _F0 = 0.00mm
Per rear: X _R0 = 2.61mm
Is set.

  Therefore, if the position of the rotor 20 at a certain point during the operation of the canned motor pump 10 is 0.00 mm or less, or 2.61 mm or more, it can be determined that the bearings 26 and 27 are worn. it can.

Here, when the voltage generated in the secondary coils 42 and 43 is Vm, the position X of the rotor 20 is
X = {(V _m −V _F0 ) / (V _R0 −V _F0 )} d
It is calculated by the following formula.

Next, the canned motor pump 10 is operated, and the current flowing in the primary coil 41 of the differential transformer 46 and the voltage generated in the secondary coils 42 and 43 when the temperature of the specification liquid is stabilized at 200 ° C.
Current flowing through the primary coil 41: I _m = 5.560 mA
Voltage generated in the secondary coils 42 and 43: V _m = 100.4 mV
Suppose that During operation of the canned motor pump 10, the rotor 20 is in a front contact state.

If the position of the rotor 20 is calculated by the above formula X without correction,
X = 0.68mm
It becomes. Since the position of the rotor 20 during operation is a front contact, there is a deviation of 0.68 mm in the rear direction. In this case, even if wear occurs on the front side, if the wear amount is 0.68 mm or less, it is determined that there is no wear, and accurate wear management cannot be performed.

  Therefore, the calculation unit 63 performs two-stage correction by the first calculation means and the second calculation means to obtain the accurate position of the rotor 20.

  First, the first calculation means of the calculation unit 63 corrects the fluctuation of the output characteristics due to the temperature of the differential transformer 46, and obtains the position of the rotor 20.

The rate of change k relative to the initial value of the current value flowing through the primary coil 41 is:
k = I ₀ / I _m = 6.471 / 5.560 = 1.164
When the value of k is multiplied by the voltage of the secondary coils 42 and 43 to obtain the correction value V _ml ,
V _ml = V _m · k = 100.4 · 1.164 = 116.85 mV
It becomes.

Using this correction value V _ml , the position of the rotor 20 is calculated by the above formula X.
X = 1.543mm
Is required.

  Subsequently, a dimensional change due to the temperature of the rotor 20, that is, a change in the position of the rotor 20 is corrected by the second calculating means of the calculating unit 63.

  Based on the test result of the canned motor 11, the temperature change ΔT [deg] from the initial state of the specification liquid is obtained by the following equation. Note that “208” and “1361” in the equation are eigenvalues of the axial displacement detection device 40, and when the specification of the axial displacement detection device 40 changes, the eigenvalue also changes to a corresponding eigenvalue.

T _m = −208 · I _m +1361
The temperature change ΔT from the initial state is
ΔT = 208 · | I _m −I ₀ | = 208 · | 5.560-6.471 | = 190 deg
It becomes. The actual temperature is 200-5 = 195 deg.

The correction constant A is obtained by the following equation.
A = α ・ L ・ ΔT
α is a linear expansion coefficient of the material of the rotating shaft 21 of the rotor 20, and L is a length from the rear end surface to the front end surface of the rotor 20.

If the material of the rotating shaft 21 of the rotor 20 is SUS304, α is 17.3 [10 ⁻⁶ / k], and L is 491 mm, the correction constant is
A = 17.3 · 10 ⁻⁶ · 491 · 190 = 1.610
It becomes.

  Such a correction constant may be obtained by calculation every time the temperature changes, but the relationship between the temperature and the correction constant for each model of the canned motor 11 is stored in advance in the table of the storage unit of the calculation unit 63. Thus, it can be easily obtained by selecting a correction constant according to the temperature.

And the corrected position X _c of the rotor 20 is
_Xc = X-A
= 1.543-1.610
= -0.07mm
It becomes.

  Thus, the calculated value of the position of the rotor 20 is changed from 0.68 mm to −0.07 mm by the first calculation means and the second calculation means of the calculation unit 63, and the correct position of the rotor 20 is 0. The value could be corrected to a value close to 00 mm.

A calculation formula for the position _Xc of the rotor 20 in consideration of temperature correction is shown below.

Ｉ_mは任意の時間の一次コイル41の電流、Ｖ_mは任意の時間の二次コイル42，43の電圧、Ｉ₀は初期状態の一次コイル41の電流、Ｖ_F0は初期状態のフロント当たりの二次コイル42，43の電圧、Ｖ_R0は初期状態のリア当たりの二次コイル42，43の電圧、ｄは回転子20の軸方向の遊び値、αは回転子20の回転軸21の材質の線熱膨張率、Ｌは回転子20のリア側の端面からフロント側の端面までの長さである。

I _m is the current of the primary coil 41 at any time, V _m is the voltage of the secondary coils 42 and 43 at any time, I ₀ is the current of the primary coil 41 in the initial state, and V _F0 is the current per front in the initial state. The voltage of the secondary coils 42 and 43, V _R0 is the voltage of the secondary coils 42 and 43 per rear in the initial state, d is the play value in the axial direction of the rotor 20, and α is the material of the rotating shaft 21 of the rotor 20. The linear thermal expansion coefficient L is the length from the rear end face of the rotor 20 to the front end face.

  As described above, according to the axial direction displacement detection device 40, the fluctuation of the output characteristic due to the temperature of the differential transformer 46 is corrected by the first calculation means of the calculation unit 63, and the rotor 20 is corrected by the second calculation means. By correcting dimensional changes due to temperature, that is, fluctuations in the position of the rotor 20, the position of the rotor 20 can be accurately detected even if the temperature changes.

  Further, by storing in advance the relationship between the temperature and the dimensional change amount correction constant of the rotor 20 according to the model of the canned motor 11, an appropriate correction constant is selected according to the temperature, and the rotor 20 The position can be detected accurately.

  Further, since the temperature detection means can detect the temperature based on the current flowing through the primary coil 41, another temperature sensor or the like can be omitted.

  In addition to the canned motor pump 10, the canned motor 11 can be applied to a canned motor agitator, a canned motor blower, a canned motor compressor, and the like.

11 Canned motor
20 rotor
26, 27 Bearing
37 Stationary part
40 Axial displacement detector
41 Primary coil
42, 43 Secondary coil
44 Coil section
45 Magnetic material
46 differential transformer
61 Oscillator circuit
62 Detection circuit
63 Calculation unit
64 Output section

Claims (3)

In the axial displacement detection device for a canned motor that detects the axial displacement of a rotor that rotates via a bearing relative to a stationary part of the canned motor,
A coil portion having a primary coil for excitation and a pair of secondary coils for detection in the axial direction, and a magnetic body disposed inside the coil portion, the magnetic body being fixed to the rotor, and the coil A differential transformer whose part surrounds the outer periphery of the magnetic body and is fixed to the stationary part;
An oscillation circuit for exciting the primary coil;
A detection circuit for detecting a current flowing in the primary coil excited by the oscillation circuit and a voltage generated in the secondary coil;
Temperature detecting means for detecting the temperature inside the canned motor;
A change rate with respect to an initial value of a current value flowing through the primary coil is obtained, a current value generated in the secondary coil is corrected based on the change rate, and a position of the rotor is obtained based on the corrected current value. A calculation unit and a correction constant for the amount of dimensional change due to the temperature of the rotor are determined according to the temperature detected by the temperature detection unit, and the correction constant of the rotor determined by the first calculation unit is obtained with this correction constant. A computing unit having second computing means for correcting the position;
And an output unit that outputs the position of the rotor obtained by the calculation unit. An apparatus for detecting an axial displacement of a canned motor. The calculation unit stores in advance a relationship between a temperature and a correction constant of the dimensional change amount of the rotor, and selects and determines a correction constant according to the temperature detected by the temperature detection unit. The apparatus for detecting an axial displacement of a canned motor according to claim 1. 3. The axial direction of the canned motor according to claim 1, wherein the temperature detecting unit detects a temperature corresponding to a current flowing through the primary coil based on a relationship between a temperature and a current flowing through the primary coil. Displacement detector.

Images