JPH0865975A - Induction motor provided with detector for axial displacement of rotor - Google Patents

Abstract

PURPOSE: To provide an induction motor provided with a detector for the axial displacement of its rotor that will produce no error due to the influence of load current, by devising the structure of skewed slots of the induction motor. CONSTITUTION: In a detector, a pair of magnetoelectric transducers 11, 12 are placed on either side of a stator core 22 and outside the main magnetic field produced in the stator. The output of the pair of the magnetoelectric transducers is wired so that unbalanced leakage magnetic flux on either side of the stator core will be output as differential output. Thus the axial displacement of a rotor 21 is detected on the basis of the degree of unbalance of leakage magnetic flux. An induction motor is provided with such a detector. The skewed slots 25 in the rotor 21 and the stator core 22 of the induction motor are so adjusted that variations in the differential output of the pair of the magnetoelectric transducers 11, 12 will be less than those in leakage magnetic flux due to variations in the load of the induction motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor equipped with an axial displacement detecting device for detecting axial displacement of a rotor.

[0002]

2. Description of the Related Art In rotary electric machines such as induction motors, it is important from the viewpoint of safety to detect the degree of wear on the axial surface of a rotor bearing. Conventionally, as a method of detecting the axial displacement of the rotor due to abrasion of the axial surface of the rotor bearing, there is a method of mechanically detecting the wear state and an electric movement of the rotor in the axial direction. It can be considered as a method of detecting. Among them, the mechanical detection method has a problem that the structure cannot be reused because the structure is complicated, high-level processing and assembly are required, and the detection method is destructive. Further, as the electrical detection method, the techniques disclosed in Japanese Patent Publication No. 57-21942 and Japanese Patent Laid-Open No. 5-130761 are known.

4 to 6 are shown in Japanese Patent Laid-Open No. 5-130761.
2 shows an induction motor equipped with the rotor axial displacement detection device disclosed in Japanese Patent Laid-Open Publication No. 2004-242242. As shown in FIGS. 4A and 4B, a pair of magnetoelectric conversion elements 11 and 12 arranged on both sides of the stator core 22 of the induction motor and outside the main magnetic field generated in the stator core 22 are provided. It is provided. As shown in FIG. 6, the outputs of the pair of magneto-electric conversion elements are bridge-connected so as to output the imbalance of the leakage magnetic flux on both sides of the stator core as a differential output. Then, the axial displacement of the rotor 21 is detected based on the unbalance degree of the leakage magnetic flux. By providing the magnetoelectric conversion elements 11 and 12 on both sides of the stator core 22 of the induction motor in this way, the axial displacement of the rotor core 21 due to wear of the bearings 23 and 24 can be achieved with a relatively simple structure and assembly method. Can be detected. This induction motor is a general one, and the rotor core 21 is provided with a rotor core slot groove 25, and as shown in FIG. 5, the skew groove 25 is about one slot.

[0004]

However, in the above-mentioned axial displacement detecting device, a pair of magnetoelectric conversion devices installed on both sides of the induction motor stator iron core are affected by load fluctuations generated during operation of the induction motor. It has been confirmed by experiments that the differential output of the element fluctuates and the signal indicating the axial displacement of the rotor core fluctuates considerably. FIG. 7 is an example of an experimental result regarding the fluctuation of the differential output due to the load fluctuation of the conventional axial displacement detection device. As shown in the figure, it can be seen that the axial displacement of the rotor has a considerable difference in differential output between no-load operation and rated load operation. Figure 8
The output as a single body of the magnetoelectric conversion element is shown. As shown in the figure, on the load side, there is almost no change between no-load operation and rated load operation. However, on the anti-load side, it can be seen that the output of the magnetoelectric conversion element greatly varies between the no-load operation and the rated load operation.

For example, when the displacement of the rotor of the induction motor in the axial direction damages the main body of the device, the displacement detecting device described above is used for the purpose of detecting the displacement and displaying it on a meter or the like. The amount of displacement in the axial direction will apparently fluctuate due to load fluctuations. Therefore, it becomes impossible to detect the correct axial displacement, that is, the degree of wear of the rotor bearing.

Therefore, as a method of eliminating the above-mentioned problems and putting the above axial displacement detecting device into practical use, a circuit device shown in FIG. 9 is used to perform differential operation according to the magnitude of the load current as shown in FIG. It is possible to correct the output. Figure 9
The middle symbol A shows the circuit configuration of the axial displacement detecting device disclosed in Japanese Patent Laid-Open No. 5-130761, and the symbol B in the figure shows the configuration of the correction circuit. That is, the induction motor 10
The load current is detected by the motor load detection unit 18 and input to the correction output unit 16. The correction output unit 16 calculates the correction amount of the differential output according to the magnitude of the load current shown in FIG. 10 according to the load of the electric motor, and the bridge circuit of the pair of magnetoelectric conversion elements arranged at both ends of the stator core is calculated. Add a correction amount. Therefore, the differential output unit 15 in FIG. 9 outputs the axial displacement amount corrected according to the magnitude of the load current,
It is displayed on the signal display unit 17.

However, in such an axial displacement detecting device for detecting the load current and calculating the correction output, the structure of the detecting device itself becomes complicated, and it becomes difficult to manufacture it at a low manufacturing cost. Further, the amount of correction due to the load current differs depending on the size and characteristics of the electric motor, so it is necessary to calculate the necessary amount of correction for each electric motor. Therefore, the adjustment of the correction amount is troublesome, and if the adjustment is not performed sufficiently, there arises a problem that the measurement error is rather enlarged.

The present invention has been made in view of the above circumstances, and provides an induction motor equipped with a rotor axial displacement detecting device which does not cause an error due to load fluctuation and can be manufactured at a low manufacturing cost. The purpose is to provide.

[0009]

In order to solve the above-mentioned problems, the present invention provides a pair of magneto-electric conversion elements arranged on both sides of an iron core of an induction motor and outside the main magnetic field created in the stator, The outputs of the pair of magneto-electric conversion elements are connected so as to output the imbalance of the leakage magnetic flux at both ends of the stator core as a differential output, and the axial displacement of the rotor is detected from the degree of imbalance of the leakage magnetic flux. An induction motor including a device, wherein the induction motor rotor and the induction motor rotor are configured to reduce fluctuations in the differential output of the pair of magnetoelectric conversion elements with respect to changes in the leakage magnetic flux due to load fluctuations in the induction motor. It is characterized by adjusting the oblique groove of the stator core.

In particular, the induction motor rotor and the stator core are provided with oblique grooves arranged in parallel or substantially parallel to each other.

[0011]

By adjusting the oblique grooves of the stator core and the rotor core of the induction motor in parallel or substantially in parallel, the differential output of the magneto-electric conversion elements arranged at both ends of the stator core is adjusted. Stable output without being affected by load fluctuations. Therefore, it is possible to accurately detect and display the axial displacement amount of the rotor without adding a troublesome circuit such as measuring the load current of the induction motor and correcting the differential output. Therefore, for an induction motor in which the axial displacement of the rotor leads to damage of the device itself, the amount of wear of the bearing and the like can be easily and accurately displayed to prevent damage.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to.

FIG. 1 is a longitudinal sectional view (A) showing an induction motor equipped with an axial displacement detecting device for a rotor according to an embodiment of the present invention, and (B) an enlarged view of a portion where a magnetoelectric conversion element is installed. . The main shaft 20 is supported by rotor bearings 23 and 24. Further, a rotor core 21 is fitted on the main shaft 20,
The main shaft 20 is rotated by the spatially rotating magnetic field generated by the stator core 22.
Is driven and rotates. The stator winding 26 is the stator core 2
2 is supplied with an exciting current for generating a magnetic field. (B) shows an end portion of the stator core 22. The stator core 22 has a cutout portion 28, and the magnetoelectric conversion element 12 having a detection coil 29 is mounted.

Therefore, the magneto-electric conversion elements 11, 12 are
Are arranged so as to detect the leakage magnetic flux on both sides of the stator core 22. The side end surface of the rotor core 21 and the side end surface of the stator core 22 are at the same position in the axial direction. Then, one ends of the magneto-electric conversion elements 11 and 12 installed on the side end surface of the stator core 22 are magnetically connected to the stator core 22, and a detection coil 29 is wound around the leg portion, and the other end is It is located inside the notch 28 of the stator core 22 and is open, so as to interlink with the leakage magnetic flux of the rotor core 21.

The magneto-electric conversion elements 11 and 12 are connected as shown in FIG. 6 to form a bridge circuit similarly to the conventional axial displacement detecting device, and the differential output is connected to the signal display unit 1.
Detect in 7. Therefore, if the rotor is axially displaced for some reason such as axial wear of the rotor bearings 23 and 24 when the induction motor is in a constant load state, the magnetoelectric conversion element on the side closer to the end surface side of the rotor core is approached. 11 or 1
2 detects a larger amount of leakage magnetic flux, and the magnetoelectric conversion element 12 or 11 on the side away from the rotor detects a smaller amount of leakage magnetic flux. As a result, the differential outputs of the magnetoelectric conversion elements 11 and 12 installed on both sides have a magnitude substantially corresponding to the axial displacement of the rotor core, and the differential outputs are output to the display unit outside the induction motor. As a result, the bearing wear amount and the like can be displayed.

2A and 2B are a front view and a side view, respectively, of the rotor core and the stator core. Stator core 2
Slot grooves 27 are provided in the rotor core 21 and the rotor core 21, respectively. The stator winding 26 is embedded in the slot groove of the stator core 22. However,
In the case of the present embodiment, as shown in the drawing, the slot grooves of the stator core 22 and the rotor core 21 are respectively parallel or substantially parallel to the main shaft 20, and the oblique grooves of both are arranged parallel or substantially parallel. ing.

FIG. 3A shows the differential output of the induction motor having the oblique groove having the structure shown in FIG. As shown in FIG. 3 (A), the differential output of the pair of magneto-electric conversion elements is the differential output during no load operation and during rated load operation in the case of an induction motor having parallel oblique grooves. Almost match. Therefore,
It can be seen that an accurate differential output can be obtained without the need to correct the differential output due to the load change, as compared with the case where there is a skew groove in the conventional induction motor.

FIG. 3B shows the output of the magnetoelectric conversion element as a single body. As shown in the figure, it can be seen that there is a certain difference between the rated load operation and the unloaded operation. However, this difference is substantially equal on the load side and the anti-load side.
Therefore, it is considered that if the circuit shown in FIG. 6 takes a differential output, this substantially equal difference is canceled. By making the rotor core and the stator core's oblique grooves parallel or substantially parallel to each other in this way, it is possible to make the fluctuations of the leakage magnetic flux due to the load fluctuations of the induction motor substantially equal on the load side and the anti-load side. it can. Therefore, as a result, the differential output corresponding to the axial displacement can be taken out without being affected by the load fluctuation.

FIG. 11 and FIG. 12 show the experimental results of the load fluctuation of the differential output due to the adjustment of the oblique grooves of the induction motor rotor and the stator core. The slot grooves of the stator core 22 are parallel to the main shaft 20, and the oblique grooves 25 of the rotor core 21 are provided between the two sides of the rotor core 21 by 0.5 slots, 0.3 slots, and 0.1 slots. , 0.0 slot, respectively. FIG. 12 shows differential output data when a rotor having these oblique grooves is used,
(A) 0.5 slot for the oblique groove, (B) 0.3 slot for the oblique groove
Slots, (C) shows a slant groove 0.1 slot, and (D) shows a slant groove 0.0 slot. In each graph, the horizontal axis is the rotor axial displacement, and the vertical axis is the differential output. The influence of load fluctuation between no-load operation and rated load operation is greatest in the case of (A) 0.5 slot, next largest in the case of (B) 0.3 slot, and in (C). It can be seen that the case of 0.1 slot is even smaller, and the case of 0.0 slot of (D) is the smallest. From this experimental result, it is possible to reduce the influence of load fluctuation on the differential output due to the axial displacement of the rotor by adjusting the diagonal grooves of the rotor and the stator. By doing so, it can be seen that the influence of the load fluctuation is almost eliminated.

In the above embodiment, the slot groove on the side of the stator is parallel to the main shaft and the groove on the side of the rotor is an oblique groove. However, on the contrary, the slot groove on the side of the rotor is parallel to the main shaft and fixed. Needless to say, the same result can be obtained even when the child side is the oblique groove.

[0021]

According to the present invention as described above,
It is possible to stably detect the axial displacement of the rotor core without providing any correction circuit for the differential output of the magnetoelectric conversion elements provided at both ends of the stator core.
As a result, it is possible to provide an induction motor that can easily and accurately indicate wear and the like of the bearing in the axial direction at a low manufacturing cost. Further, since the correction circuit is not required, it is not necessary to adjust the differential output for each electric motor.

[Brief description of drawings]

FIG. 1 is a sectional view taken along the axial direction (A) of an induction motor equipped with a rotor axial displacement detection device according to an embodiment of the present invention;
(B) An enlarged view showing a mounting portion of the magneto-electric conversion element.

FIG. 2 is a front view (A) and a side view (B) of a rotor core and a stator core according to an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the axial displacement of the rotor and the output of the magnetoelectric conversion element, (A) differential output, (B).
Indicates single output.

FIG. 4 is a cross-sectional view taken along the axial direction (A) of an induction motor including a conventional rotor axial displacement detection device, and (B) an enlarged view showing a portion to which a magnetoelectric conversion element is attached.

FIG. 5 is a (A) front view of a conventional rotor and stator core;
(B) A side view.

FIG. 6 is a circuit diagram showing connection of magnetoelectric conversion elements.

FIG. 7 is a graph showing the relationship between the axial displacement of the rotor and the output of the magnetoelectric conversion element, showing the differential output.

FIG. 8 is a graph showing the relationship between the axial displacement of the rotor and the output of the magnetoelectric conversion element, showing a single output.

FIG. 9 is a circuit diagram showing a connection of a magnetoelectric conversion element to which a correction circuit is added.

FIG. 10 is a graph showing the relationship between the axial displacement of the rotor and the correction output.

FIG. 11 is a front view of a rotor and a stator core.

FIG. 12 is a graph showing the relationship between the axial displacement of the rotor and the differential output.
Represents a groove groove 0.3 slot, (C) represents a groove groove 0.1 slot, and (D) represents a groove groove 0.0 slot.

[Explanation of symbols]

 11, 12 Magnetoelectric conversion element 21 Rotor core 22 Stator core 23, 24 Rotor bearing 25 Rotor skew groove

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yukio Tonoyama 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside EBARA Research Institute, Inc. (72) Inventor Toshiya Akasaka 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo No. Within EBARA CORPORATION (72) Inventor Atsushi Oyama 1-3-1 Ginza, Chuo-ku, Tokyo Stock company Ebara Densan

Claims (2)

[Claims] 1. A pair of magneto-electric conversion elements are arranged on both sides of the stator core and outside the main magnetic field created in the stator, and the outputs of the pair of magneto-electric conversion elements are determined by the leakage magnetic flux on both sides of the stator core. An induction motor equipped with a detection device, which is connected so as to output an unbalance as a differential output and detects displacement in the axial direction of the rotor based on the unbalance degree of the leakage magnetic flux, the load fluctuation of the induction motor being provided. Induction characterized in that the oblique grooves of the induction motor rotor and the stator core are adjusted so as to reduce the fluctuation of the differential output of the pair of magnetoelectric conversion elements due to the change of the leakage magnetic flux due to Electric motor. 2. The induction motor equipped with the rotor axial displacement detecting device according to claim 1, wherein the oblique grooves of the induction motor rotor and the stator core are arranged in parallel or substantially in parallel.