JP3604276B2 - Induction motor and method of detecting wear of bearing thereof - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an induction motor such as a canned motor that supports a rotor by a slide bearing, and in particular, detects and outputs the movement of a rotor core caused by the progress of wear of the slide bearing and the like, and detects the wear of the bearing by using this output. The present invention relates to a method for detecting bearing wear, which enables the following.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an induction motor using a sliding bearing in a bearing portion for supporting a rotor, such as a canned motor pump, a slip generated by using the induction motor for a long time, mixing of foreign matter, biting, or the like. There was a problem of wear of the bearing. 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.
[0003]
In particular, the canned motor pump has a structure in which metal walls are provided on the rotor and the stator, respectively, and a pump handling liquid is supplied to a gap therebetween to suppress heat generation of the induction motor main body, so that the whole becomes an integral pressure vessel. I have. In such a pump, abnormal whirling occurs in the rotor due to wear of the slide bearing, and when the rotor comes into contact with the stator, the metal partition walls of the rotor and the stator may be damaged. In such a case, the pump handling liquid will enter the inside of 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.
[0004]
Further, since the canned motor pump has an integral pressure vessel structure without a seal portion 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 bearings are worn out for any reason, such as long-term use or the entry of foreign matter, the changes cannot be confirmed from the outside. This has been done according to the rules of thumb of the workers.
[0005]
An example of a bearing wear detection mechanism using a mechanical detection method that has been proposed or implemented to detect the wear state of a bearing is an example of a machine in which a fixed gap is maintained between a rotor at an end of a motor rotor. There is a detection mechanism having a function of discharging the gas enclosed therein due to contact wear between the contact portion and the rotating body with the contact portion. In the case of such a detection mechanism, once the detection mechanism operates, the gas sealed inside the detection mechanism is released, so that the detection mechanism itself needs to be replaced together with the worn bearing, and maintenance parts are required. There is a problem that it has to be increased.
[0006]
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. 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. Also, in the case of a detection mechanism in which a magnetic detection element is provided on the end face of the stator core of the induction motor, the effect of load fluctuations and power supply fluctuations of the induction motor is large, and there is a problem that the wear state is not accurately displayed and reliability is reduced. Was.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described circumstances, and in an induction motor having a mechanism for supporting a rotor by a slide bearing such as a canned motor, using an electrical detection method of the progress of wear of the slide bearing. In addition, an object of the present invention is to provide an induction motor having a detection mechanism capable of easily and reliably monitoring, and a method of detecting bearing wear thereof.
[0008]
[Means for Solving the Problems]
In the induction motor according to the present invention, a notch is provided in an inner peripheral portion of an end face of a stator core of the induction motor, and a magneto-electric converter that detects a magnetic flux between the stator core and the rotor core. In the induction motor in which an element is arranged in the notch , the magnetoelectric conversion element includes an iron core and a detection surface on which a detection coil is wound around the iron core, and the detection surface is formed in the stator core. It is arranged on substantially the same plane as the peripheral surface and the end surface, a part of the core of the detection surface is connected to an end surface of the stator core, and another part of the core is separated from the end surface of the stator core in a direction away from the end surface of the stator core. It is characterized by comprising a shielding structure extending to a position outside the detection surface so as to magnetically shield the detection surface of the magneto-electric transducer .
[0009]
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 induction motor. When the rotor moves in the direction and / or axial direction, the output of the magneto-electric transducer on the side closer to the rotor increases, and the output of the magneto-electric transducer on the side closer to the rotor decreases. Therefore, by performing an appropriate operation on the output of these magneto-electric transducers, the radial / axial wear of the bearing can be obtained.
[0010]
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.
[0011]
Moreover, in magneto-electric conversion element of the present invention, prior SL core is connected from the detection surface side iron core portion of the stator end faces extending the stator outer periphery, barrier further bent in a U-shape 蔽構 It is characterized by having a structure.
[0012]
As a result, since 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 conversion element, the magnetic flux due to the load fluctuation component from the induction motor rotor is applied to the detection portion. Will not enter. That is, the magnetic flux component due to the load current of the rotor mainly occurs near the end ring of the rotor. With the above shielding structure, this magnetic flux component is shielded from the detection portion of the magneto-electric conversion element, so that 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. The bearing wear can be stably detected.
[0013]
Moreover, in magneto-electric conversion element of the present invention, the core extends from the detection surface on the stator outer periphery, extending the stator outer periphery is bent in a direction away from the stator end surface, further bent in the reverse direction to that comprising the 蔽構 Concrete shielding connected to the core portion of the stator end face.
[0014]
Thereby, since the iron core of the magneto-electric conversion element protrudes in a direction away from the end face of the stator, it is possible to absorb a magnetic flux due to a load current mainly flowing near the end ring of the rotor of the induction motor at the bent portion. 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, thereby detecting the original magnetic flux between the stator and the rotor. Can be performed stably.
[0015]
In addition, the method for detecting bearing wear of an induction motor according to the present invention includes providing a notch at an inner peripheral portion of an end face of a stator core of the induction motor, and detecting a magnetic flux between the stator core and the rotor core. An electric conversion element is disposed in the notch on the end face of the induction motor stator core, and a plurality of the magneto-electric conversion elements are disposed in a circumferential direction and an axial direction so as to face each other around the rotor axis. The electric conversion element includes an iron core and a detection surface on which a detection coil is wound around the iron core. The detection surface is disposed on substantially the same plane as an inner peripheral surface and an end surface of the stator core. A part of the iron core is connected to the end face of the stator core, and the other part of the iron core magnetically shields the detection surface of the magneto-electric transducer in a direction away from the end face of the stator core. A shielding structure that extends to a position outside the detection surface For example, the above magneto-electric conversion element so as not to be affected by the magnetic flux due to the induction motor load current from said rotor said induction by detecting a change in magnetic flux between being shielded from said magnetic flux, and the stator rotor it is characterized in that for detecting the wear of the bearings of the motor.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view of a canned motor pump including an induction motor according to an embodiment of the present invention. In FIG. 1, sliding 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.
[0017]
Reference numerals S _{1 to} S _{4 in} FIG. 1 denote magneto-electric transducers that are installed opposite to the cutouts on both end faces of the stator core of the induction motor, and face each other around the rotor axis as shown in FIG. As a set of two pieces, in this case, two sets are arranged at an interval of about 60 °. Of course, this interval may be arranged orthogonally at 90 °.
[0018]
Usually, 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 ₄ installed opposite to both end faces of the stator core 1 of the induction motor are used. The spatial distances in both axial and radial directions at both ends of the rotor core 2 are equal, and the output signals of the magneto-electric conversion elements due to the magnetic flux from the rotor core 2 have the same value in the respective elements S _{1 to} S _4. Become.
[0019]
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 is moved in the axial direction (the direction indicated by arrow A in FIG. 1). Let's say you moved to 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
[0020]
Next, when wear occurs between the shaft sleeves 6 and 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), 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 of the element closer to the rotor core 2 is the rotor. It decreases in proportion to the distance that the iron 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)
However, S ₁ = S ₂ , S ₃ = S ₄
[0021]
However, the output of each magneto-electric conversion element simply installed on both end faces of the stator core includes a load variation component that varies depending on the load of the induction motor in addition to the rotor movement component. Since this load fluctuation component exists, the output of the magneto-electric conversion element changes depending on the operating point of the induction motor, and the wear detection includes an error. 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.
[0022]
FIG. 3 shows a structure of a magneto-electric transducer integrated with a magnetic shield according to the first embodiment of the present invention. The magneto-electric transducer 13 shown in FIG. 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 in the radial direction toward the outer peripheral side of the stator, bends in a U-shape, and returns to the inner peripheral side of the stator (11s). Are arranged so as to shield the wound part.
[0023]
Therefore, the magnetic flux [Phi _R formed by the load current largely end ring 2a of the rotor, would be absorbed in the shielding portion 11s of the core, thereby the detection surface in the vicinity of the detection coil 12 is wound is I can hardly enter. On the other hand, the component Φ _SL of the end of the magnetic flux Φ _{S in} 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 conversion element 13 would hardly affected by the magnetic flux [Phi _R the rotor current is formed.
[0024]
FIG. 4 shows a structure of a magneto-electric transducer integrated with a magnetic shield according to a second embodiment of the present invention. Also in this embodiment, the detection portion of the magneto-electric conversion element 13b including the iron core 11 and the detection coil 12 wound around the core 1 is arranged in the cutout portion 1b on the end face of the stator 1. The iron core 11 extends radially outward from the portion where the detection coil 12 is wound, and extends therefrom in a direction away from the stator end face to extend toward the stator outer periphery (11c). It is bent and connected to the iron core portion 1e on the outer periphery of the stator.
[0025]
Such a structure becomes possible 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 [Phi _R formed by the load current of the induction motor is almost no longer enter into the detection surface 11a of the iron core 11 of the detection coil 12 is wound, the bent portion 11c of the iron core 11 is so to speak the magnetic flux [Phi _R It will provide a shielding effect.
[0026]
FIG. 5 shows an example of a detection output by the above-described 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 shielding structure shown in (b) is used, 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. As a result, the components Φ _R of the magnetic flux accompanying the load fluctuation generated mainly near the end ring of the rotor are shielded by the magnetic shield structures 11 s and 11 c by the magneto-electric conversion elements 13 a and 13 b provided with the magnetic shield structure. It hardly affects the detection parts of the electric conversion elements 13a and 13b. For this reason, only the magnetic flux component Φ _SL at the end of the rotor 2 is output to the detection coils 12 of the magneto-electric conversion elements 13a and 13b. Therefore, regardless of the magnitude of the load current, it is possible to always detect the wear of the bearing according to the equations (1) and (2).
[0027]
FIG. 6 shows an example of a processing circuit for a signal output from the magneto-electric transducer. The configuration of this signal processing circuit includes input units 31 to 34 for 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 the respective signal processing results, 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. Then, the wear state of the bearing is determined from the change in the position.
[0028]
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, and the axial direction of the rotor core 2 can be detected. , Or that the wear has progressed in each of the radial directions can be individually detected.
[0029]
Although the above-described embodiment is directed to an example of a canned motor pump using a slide bearing, the gist of the present invention is not limited to this embodiment, and is widely used for detecting wear of various types of slide bearings. What you can do is, of course. Further, in the present embodiment, two sets of the magneto-electric transducers are arranged as a pair corresponding to the rotor shaft, a radial wear amount in the xy directions is detected, and a position separated along the rotor shaft is detected. Further, two sets of magneto-electric transducers are similarly arranged. This makes it possible to detect the wear amount of the radial and thrust bearings. However, a larger number of magneto-electric conversion elements may be provided, 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]
【The invention's effect】
As described above, the induction motor using the slide bearing, in particular, the magneto-electric conversion element having a magnetic shield integrated structure eliminates the influence of the magnetic flux formed by the load current of the rotor, thereby reducing the heavy load. It is possible to always detect the state of the bearing wear stably even at the time of 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 of a mounting portion of a magneto-electric conversion element of the induction motor in FIG. 1 viewed in an axial direction.
FIG. 3 is an explanatory diagram showing 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, wherein FIG. 5A shows a case without a shield structure, and FIG. The case where it has is shown.
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 coils 11c, 11s Shielding structure part Φ _R Magnetic flux Φ _S due to rotor load current Magnetic flux Φ _SL of stator / rotor gap Magnetic flux in the air gap between the stator and rotor entering the detection surface

Claims (4)

In the induction motor, a notch is provided in the inner peripheral portion of the end face of the stator core of the induction motor, and a magneto-electric conversion element for detecting a magnetic flux between the stator core and the rotor core is arranged in the notch. The magneto-electric conversion element includes an iron core and a detection surface on which a detection coil is wound around the iron core, and the detection surface is disposed on substantially the same plane as an inner peripheral surface and an end surface of the stator core. A part of the core of the detection surface is connected to an end surface of the stator core, and another part of the core magnetically shields the detection surface of the magneto-electric conversion element in a direction away from the end surface of the stator core. An induction motor having a shielding structure extending to a position outside the detection surface as described above . Before SL core is claim, characterized in that extending from the detection surface on the stator outer periphery connected to the core portion of the stator end surface, further comprising a 蔽構 Concrete shielding bent in shape of U 1 2. The induction motor according to claim 1. The core extends from the detection surface on the stator outer periphery, extending the stator outer periphery is bent in a direction away from the stator end surface, and connected to the core portion of the stator end face and further bent in the opposite direction induction motor according to claim 1, characterized in that with a 蔽構 concrete shielding. A notch is provided in the inner peripheral portion of the end face of the stator core of the induction motor, and the magneto-electric conversion element for detecting magnetic flux between the stator core and the rotor core is provided with the notch on the end face of the stator core of the induction motor. Arranged, a plurality of the magneto-electric conversion elements are arranged in a circumferential direction and an axial direction facing each other around the rotor axis,
The magneto-electric conversion element includes an iron core and a detection surface on which a detection coil is wound around the iron core, and the detection surface is disposed on substantially the same plane as an inner peripheral surface and an end surface of the stator core. A part of the surface iron core is connected to the end face of the stator core, and another part of the iron core magnetically shields the detection surface of the magneto-electric transducer in a direction away from the end face of the stator core. A shielding structure extending to a position outside the detection surface,
The magneto-electric conversion element is shielded from the magnetic flux so as not to be affected by the magnetic flux due to the induction motor load current from the rotor, and detects a change in the magnetic flux between the stator and the rotor by detecting a change in the magnetic flux. A method for detecting bearing wear of an induction motor, comprising detecting bearing wear.

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