JPH11299195A - Induction motor, and sensing method of abrasion of its bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor by an electric sensing means easily and surely the abrasion advancing state of a slide bearing of such an induction motor as a canned motor having the mechanism for supporting its rotor by the slide bearing. SOLUTION: In an induction motor, providing notch portions in some portions of the end surface of its stator core 1, magnetoelectric conversion elements S1 , S2 , S3 , S4 for sensing a magnetic flux ΦS between its stator core 1 and its rotor 2 are disposed in the notch portions. In this case, in order that the magnetoelectric conversion elements S1 , S2 , S3 , S4 are not affected by a magnetic flux ΦR caused by the load current of the induction motor which is generated from its rotor, there is provided in it a shield structure 11s for shielding the elements S1 , S2 , S3 S4 from the magnetic flux ΦR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor such as a canned motor for supporting a rotor by a slide bearing, and more particularly to detecting and outputting a movement of a rotor core caused by advancing wear of the slide bearing. The present invention relates to a bearing wear detection method which enables bearing wear detection using this output.

[0002]

2. Description of the Related Art Conventionally, in an induction motor such as a canned motor pump or the like, which uses a sliding bearing for a bearing portion for supporting a rotor, the use of the induction motor for a long period of time, the inclusion of foreign matter, the biting, etc. There was a problem of wear of the sliding bearing caused by the cause. Due to the progress of wear, the rotor portion abnormally whirls inside the stator or moves in the axial or radial direction. If such a situation progresses, the rotor and the stator may come into contact with each other. For example, fatal damage may occur to the induction motor itself.

In particular, a canned motor pump has a structure in which metal walls are provided on a rotor and a stator, respectively, and a pump handling liquid is supplied to a gap therebetween to suppress heat generation of an induction motor main body, thereby forming an integral pressure vessel as a whole. Has taken. In such a pump, abnormal whirling of the rotor occurs due to wear of the sliding bearing, and when the rotor and the stator come into contact with each other, the metal partition walls of the rotor and the stator may be damaged. In such a case, the pump handling liquid will infiltrate into the stator, and this infiltration will cause deterioration of the insulation of the stator windings and cause a catastrophic failure of the induction motor body. Is also conceivable.

Further, since the canned motor pump has an integral pressure vessel structure without a seal between the pump and the induction motor, it is impossible to visually check the bearing sliding surface from outside the main body. Even if the bearing is worn out for some reason, such as long-term use or foreign matter contamination, the change cannot be confirmed from the outside.Conventionally, the bearing must be replaced regularly for inspection and maintenance. This has been done according to the rules of thumb of workers.

[0005] Among the means for detecting the state of wear of a bearing that has been proposed or implemented so far, an example of a mechanism for detecting wear of a bearing using a mechanical detection method is to provide a fixed gap between the rotor of the motor and the end of the rotor. There is a mechanical contact portion that is kept, and a detection mechanism that has a function of discharging the gas sealed inside by the contact wear between the contact portion and the rotating body. In the case of such a detection mechanism, once the detection mechanism operates, the gas sealed inside the detection mechanism is released,
It is necessary to replace the detection mechanism itself together with the worn bearing, and there is a problem that maintenance parts must be increased.

Examples of the electrical detection mechanism include a method in which a search coil is wound in a stator winding slot, and a method of detecting a wear state of a slide bearing using an induction motor having a special winding structure. is there. However, in the case of these detection mechanisms, the structure of the induction motor itself becomes complicated and special, which hinders the provision of inexpensive products. In addition, in the case of a detection mechanism in which a magnetic detection element is provided on the end face of the induction motor stator core, there is a problem that the influence of load fluctuation and power supply fluctuation of the induction motor is large, and the wear state is not accurately displayed and reliability is reduced. Was.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in an induction motor having a mechanism in which a rotor is supported by a slide bearing such as a canned motor, the wear of the slide bearing progresses. It is an object of the present invention to provide an induction motor having a detection mechanism capable of easily and reliably monitoring the situation by using an electrical detection method, and a method of detecting wear of the bearing.

[0008]

According to a first aspect of the present invention, a notch is provided at a part of an end face of a stator core of an induction motor to detect a magnetic flux between the stator core and a rotor core. In the induction motor in which the magneto-electric conversion element for performing the above is disposed in the cutout portion, the magneto-electric conversion element shields the magnetic flux so as not to be affected by the magnetic flux due to the induction motor load current generated from the rotor. It is characterized by having a shielding structure.

According to the present invention, a part of the stator of the induction motor is cut out, and a plurality of sets of magneto-electric conversion elements are provided in the cut-out portions on both end surfaces of the stator.
When the induction motor rotor moves in the radial direction and / or axial direction, the output of the magneto-electric conversion element closer to the rotor increases, and the output of the magneto-electric conversion element closer to the rotor decreases. Therefore, by performing an appropriate calculation on the outputs of these magneto-electric transducers, the amount of wear in the radial / axial direction of the bearing can be obtained.

Further, in the present invention, the magneto-electric conversion element is provided with a magnetic shielding structure so as to prevent the influence of the magnetic flux fluctuation component of the load current from the induction motor rotor. Thus, since the magneto-electric conversion element shields the load fluctuation signal component of the magnetic flux, the wear amount of the bearing can be directly detected regardless of the operation state of the induction motor.

According to a second aspect of the present invention, the magneto-electric transducer includes an iron core and a detection coil wound around the iron core, and a detection surface of the iron core is substantially equal to an inner peripheral surface of the stator. The shield structure is arranged on the same surface, the shield structure extends from the other end of the detection surface of the iron core to the outer peripheral surface of the stator, and is bent in a U-shape to magnetically couple the detection surface of the magneto-electric conversion element. Characterized in that it is a structure that shields the light.

As a result, the iron core extends toward the outer peripheral surface of the stator and bends in a U-shape to shield the detection portion of the magneto-electric transducer, so that the magnetic flux due to the load fluctuation component from the rotor of the induction motor is reduced. It will not enter the detection part. That is, the magnetic flux component due to the load current of the rotor mainly occurs near the end ring of the rotor. By shielding this magnetic flux component from the detection part of the magneto-electric transducer by the above-mentioned shielding structure, the detection of the original magnetic flux between the stator and the rotor can be performed without being affected by the load current of the rotor. This makes it possible to stably detect the wear of the bearing.

According to a third aspect of the present invention, the magneto-electric transducer comprises an iron core and a detection coil wound on the iron core, and a detection surface of the iron core is substantially equal to an inner peripheral surface of the stator. Arranged on the same surface, the shielding structure is bent in a direction away from the stator end surface from the other end side of the detection surface of the iron core and extends toward the outer periphery of the stator, and further bent in the opposite direction to form the outer periphery of the stator. It is connected to an iron core portion, and has a structure in which a magnetic flux due to a load current of the induction motor is absorbed by the bent portion to magnetically shield a detection surface of the iron core.

Since the core of the magneto-electric transducer projects in a direction away from the end face of the stator, the bent portion absorbs the magnetic flux due to the load current mainly flowing near the end ring of the rotor of the induction motor. Can be. For this reason, the magnetic flux due to the load current of the induction motor does not affect the detection portion of the magneto-electric conversion element arranged in the cutout portion of the stator end face.
It is possible to stably detect the original magnetic flux between the rotors.

According to a fourth aspect of the present invention, there is provided a magneto-electric conversion element for providing a notch in a part of an end face of a stator core of an induction motor to detect a magnetic flux between the stator core and a rotor core. Are arranged in the notch on the end face of the stator core of the induction motor, and a plurality of the magneto-electric conversion elements are arranged in the circumferential direction and the axial direction so as to face each other with the rotor axis as a center, and are guided from the rotor. The magnetoelectric conversion element is shielded from the magnetic flux so as not to be affected by the magnetic flux due to the motor load current, and detects a change in magnetic flux between the stator and the rotor to detect wear of the bearing of the induction motor. This is a method for detecting bearing wear of an induction motor.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a canned motor pump including an induction motor according to one embodiment of the present invention. In FIG. 1, slide bearings 3 and 4 for supporting a rotor shaft 10 support the axial load of the rotor shaft on the thrust plates 7 and 9 and the contact surfaces thereof, and support the radial load on the shaft sleeves 6 and 8. And the contact surface.

Reference numerals S _{1 to} S _{4 in} FIG. 1 denote magneto-electric transducers installed opposite to the cutouts on both end faces of the stator core of the induction motor. As shown in FIG. In this case, two sets are opposed to each other. In this case, the two sets are arranged at an interval of about 60 °. Of course, this interval may be arranged orthogonally at 90 °.

Normally, when the induction motor is operated in a normal state without any abnormality in the bearings or the like, the magneto-electric conversion elements S ₁ to S ₁ are installed opposite to both end faces of the stator core 1 of the induction motor. The spatial distances in both axial and radial directions at both ends of S ₄ and the rotor core 2 are equal.
The output signal of the magneto-electric conversion element due to the magnetic flux from the respective elements S _{1 to} S ₄ also has the same value.

Here, in this canned motor pump, wear occurs between the bearing thrust plates 7, 9 and the bearing member for some reason, and the rotor shaft 10 moves in the axial direction (indicated by an arrow A in FIG. 1). Direction). In this case, the magneto-electric conversion output signal of the element closer to the rotor core 2 with respect to each magneto-electric conversion element increases in proportion to the distance that the rotor core 2 approaches, and the element closer to the rotor core 2 moves away. Is reduced in proportion to the distance that the rotor core 2 moves away. At this time, when the outputs of the magneto-electric transducers are compared, the following equation is established. (S ₁ , S ₃ ) ≦ (S ₂ , S ₄ ) (1) where S ₁ = S ₃ , S ₂ = S ₄

Next, wear occurs between the shaft sleeves 6, 8 and the bearing member for some reason as described above, and the rotor shaft 10 moves in the radial direction (the direction indicated by the arrow B in FIG. 1). In this case, the conversion output signal of the element closer to the rotor core 2 with respect to each magneto-electric conversion element increases in proportion to the distance that the rotor core approaches, and the conversion output signal of the element closer to the rotor core 2 moves away. Decreases in proportion to the distance that the rotor core 2 moves away. At this time, as in the case described above, when the outputs of the magneto-electric transducers are compared, the following equation is established. (S ₁ , S ₂ ) ≦ (S ₃ , S ₄ ) (2) where S ₁ = S ₂ , S ₃ = S ₄

However, the output of each magneto-electric conversion element simply installed on both end faces of the stator core includes a load fluctuation component that fluctuates depending on the load of the induction motor in addition to the rotor movement component. Since the load fluctuation component exists, the output of the magneto-electric conversion element changes depending on the operating point of the induction motor, and an error is included in the wear detection. Since this load fluctuation component is considered to be mainly generated from the end ring of the rotor, a structure in which a magnetic shield is integrated with the magneto-electric transducer as shown in FIGS. 3 and 4 is employed.

FIG. 3 shows a structure of a magneto-electric transducer integrated with a magnetic shield according to a first embodiment of the present invention. 3 includes an iron core 11 and a detection coil 12 wound around the iron core. The detection surface 11a of the iron core around which the coil 12 is wound is disposed on substantially the same surface as the inner peripheral surface 1a of the stator. And the magneto-electric conversion element 13 is arrange | positioned at the notch part 1b of a stator end surface. The iron core 11 around which the detection coil 12 is wound extends radially toward the outer periphery of the stator, and is bent in a U-shape.
Again facing the inner circumferential side of the stator (11s), it is arranged so as to shield the portion of the iron core 11 around which the detection coil 12 is wound.

Therefore, mainly the end ring 2 of the rotor
The magnetic flux Φ _R formed by the load current a is absorbed by the shield portion 11s of the iron core, and thereby hardly enters the detection surface near the winding of the detection coil 12. On the other hand, the component Φ _SL of the end of the magnetic flux Φ _S of the air gap between the stator and the rotor formed by the stator winding is formed so as to pass through the detection surface 11 a of the magneto-electric transducer 13. The amount can be detected by the detection coil 12. Therefore, the magneto-electric transducer 13 is hardly affected by the magnetic flux Φ _R formed by the rotor current.

FIG. 4 shows a structure of a magneto-electric conversion element integrated with a magnetic shield according to a second embodiment of the present invention. Also in this embodiment, the notch 1b of the end face of the stator 1
A detection portion of a magneto-electric conversion element 13b including an iron core 11 and a detection coil 12 wound therearound is arranged. The iron core 11 extends radially outward from the portion around which the detection coil 12 is wound, where it is bent away from the stator end face and extends toward the stator outer peripheral side (11).
c), further bent in the opposite direction, and an iron core portion 1e on the outer periphery of the stator.
It is connected to the.

[0025] With such a structure, and thus to absorb the magnetic flux [Phi _R formed by the load current in the vicinity of the largely end ring 2a of the induction motor at the bent portion 11c. Therefore, the magnetic flux Φ formed by the load current of the induction motor
_R is the detection surface 1 of the iron core 11 around which the detection coil 12 is wound.
It hardly enters into 1a, and the bent portion 11c of the iron core 11 provides a so-called magnetic flux Φ _R shielding effect.

FIG. 5 shows an example of a detection output by the above-mentioned magnetic shield integrated type magneto-electric transducer. (A) shows a case without a magnetic shielding structure, and (b) shows a case with a magnetic shielding structure. When the magnetic shielding structure shown in (a) is not provided, there is a large difference in the operation output between the light load operation and the heavy load operation in both the radial wear amount and the thrust wear amount. On the other hand, when the magnetic shield structure shown in (b) is provided, there is almost no difference in the operation output between the light load operation and the heavy load operation in both the radial wear amount and the thrust wear amount. Thus, the magneto-electric transducers 13a, 13a provided with the magnetic shielding structure
3b, the component Φ _R of the magnetic flux accompanying the load fluctuation mainly generated near the end ring of the rotor is shielded by the magnetic shield structures 11s and 11c, and the magneto-electric conversion element 13
The detection portions a and 13b are hardly affected. For this reason, the detection coil 1 of the magneto-electric conversion elements 13a and 13b
2, only the magnetic flux component Φ _SL at the end of the rotor 2 is output. Therefore, regardless of the magnitude of the load current,
The wear of the bearing can always be detected according to the equations (1) and (2).

FIG. 6 shows an example of a circuit for processing a signal output from the magneto-electric transducer. The configuration of this signal processing circuit includes input units 31 to 34 receiving respective signals of the magneto-electric conversion elements S ₁ , S ₂ , S ₃ , S _4, etc., differential amplifier units 35 to 38 for comparison, , An offset adjustment section 39 to 42 for performing the offset adjustment, a determination circuit section 43 for calculating the rotor position from each signal processing result, and a display circuit section 44 for displaying the determined result. Therefore, the output of each element S ₁ , S ₂ , S ₃ , S ₄ is input to a comparison circuit for determining each output signal, and the position of the rotor shaft 10 is determined by the output of each magneto-electric conversion element. Detect
The wear state of the bearing is determined from the change in the position.

Therefore, by monitoring the differential output in the same manner as when the axial wear occurs, it is possible to detect the radial movement of the rotor core 2 caused by the wear of the bearing and the like. It is possible to individually detect that the wear has progressed in each of the axial direction and the radial direction.

Although the above-described embodiment is directed to an example of a canned motor pump using a sliding bearing, the gist of the present invention is not limited to this embodiment, and a wide variety of sliding bearings can be used. Of course, it can be used for detection. Further, in the present embodiment, two sets of the magneto-electric transducers are arranged as a pair of the target on the rotor shaft, the radial wear amount in the xy directions is detected, and the positions separated along the rotor shaft are detected. And two sets of magneto-electric transducers are similarly arranged. Thus, the wear amount of the radial and thrust bearings can be detected. However, a larger number of magneto-electric conversion elements may be arranged, or the number of magneto-electric conversion elements may be reduced. By increasing the number of magneto-electric transducers, finer detection of bearing wear is possible, but by reducing the number of magneto-electric transducers, a more economical device can be obtained. .

[0030]

As described above, by using an induction motor using a sliding bearing, in particular, a magneto-electric conversion element having a magnetic shield integrated structure, it is not affected by the magnetic flux formed by the load current of the rotor. Thus, it is possible to always detect the state of bearing wear stably even under a heavy load or a light load.

[Brief description of the drawings]

FIG. 1 is a sectional view of a canned motor pump according to an embodiment of the present invention.

FIG. 2 is a view in which an attachment portion of a magneto-electric conversion element of the induction motor in FIG. 1 is viewed in an axial direction.

FIG. 3 is an explanatory diagram illustrating a structure of the magneto-electric transducer according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating a structure of a magneto-electric transducer according to a second embodiment of the present invention.

5A and 5B are diagrams showing output characteristics of a magneto-electric transducer when a bearing is worn in a radial direction and an axial direction, and FIG. 5A shows a case without a shield structure,
(B) shows a case having a shield structure.

FIG. 6 is a circuit diagram showing an example of an output signal processing circuit of the magneto-electric transducer.

[Explanation of symbols]

1 stator core 2 rotor core 3 and 4 slide bearing 6,8 shaft sleeve 7 and 9 the bearing thrust plate 10 rotor axis _{S 1, S 2, S 3} , S 4 magnetoelectric conversion element A axial movement direction B radial movement Direction 11 Iron core 12 Detection coil 11c, 11s Shielding part Φ _R Magnetic flux due to rotor load current Φ _S Magnetic flux at stator / rotor gap Φ _SL Magnetic flux at stator / rotor gap entering _SL detection surface

Continued on the front page (72) Inventor Tomotoshi Hirata 11-1 Haneda Asahimachi, Ota-ku, Tokyo Ebara Corporation (72) Inventor Tomoyuki Yamazaki 4-1-1 Motofujisawa, Fujisawa-shi, Kanagawa Ebara Corporation (72) Inventor Daimasa 4-1-1, Motofujisawa, Fujisawa-shi, Kanagawa Prefecture Ebara Densan Co., Ltd. (72) Koichi Otake 4-1-1, Motofujisawa, Fujisawa-shi, Kanagawa Share (72) The inventor Takayuki Kuronuma 4-1-1, Motofujisawa, Fujisawa-shi, Kanagawa

Claims (4)

[Claims] 1. A notch portion is provided at a part of an end face of a stator core of an induction motor, and a magneto-electric conversion element for detecting a magnetic flux between the stator core and a rotor core is arranged in the notch portion. In the induction motor described above, the magneto-electric conversion element is:
An induction motor, comprising: a shielding structure that shields the magnetic flux so as not to be affected by the magnetic flux due to the induction motor load current generated from the rotor. 2. The magneto-electric transducer comprises an iron core and a detection coil wound on the iron core, and a detection surface of the iron core is disposed on substantially the same plane as an inner peripheral surface of the stator. The structure extends from the other end of the detection surface of the iron core to the outer peripheral surface of the stator and bends in a U-shape to magnetically shield the detection surface of the magneto-electric transducer. The induction motor according to claim 1, wherein: 3. The magneto-electric transducer comprises an iron core and a detection coil wound on the iron core, and a detection surface of the iron core is disposed on substantially the same plane as an inner peripheral surface of the stator. The structure is bent in a direction away from the stator end face from the other end side of the detection surface of the iron core and extends toward the outer periphery of the stator, and further bent in the opposite direction to be connected to an iron core portion on the outer circumference of the stator. 2. The induction motor according to claim 1, wherein a portion of the induction motor is configured to magnetically shield a detection surface of the iron core by absorbing a magnetic flux due to a load current of the induction motor. 3. 4. A notch is provided at a part of an end face of a stator core of an induction motor, and a magneto-electric conversion element for detecting a magnetic flux between the stator core and a rotor core is provided at the end face of the stator core of the induction motor. A plurality of the magneto-electric transducers are arranged in a circumferential direction and an axial direction so as to face each other with the rotor axis as a center, and the influence of magnetic flux due to an induction motor load current from the rotor is reduced. An induction motor that detects wear of a bearing of the induction motor by detecting a change in magnetic flux between the stator and the rotor while the magneto-electric conversion element is shielded from the magnetic flux so as not to receive the magnetic flux; Method of detecting bearing wear.