KR101262902B1 - Rotator for electric-motor - Google Patents

Abstract

PURPOSE: A rotator for an electric motor is provided to reduce process time and production costs by manufacturing and assembling the rotator without a high technical cutting process. CONSTITUTION: A shaft(110) has a pillar shape in a specific direction. A fixing groove is formed in the side(111c) of the shaft. A core body(130) is formed between spacers(170) and is inserted into the shaft. The core body includes a core ring formed in a shaft hole, and a core piece having a core piece protrusion. An end plate(180) is combined with one end of the shaft.

Description

Rotorator for electric motor

The present invention relates to a rotor for an electric motor, and more particularly, to provide a rotor of an electric motor that can be easily assembled to be aligned according to a skew angle preset by a user.

A switched reluctance motor (SRM) is driven by a method of applying a square wave pulse instantaneously with a direct current voltage to a stator field structure. Such switched reluctance motors are attracting attention as motors that can replace existing motors due to their simple structure, easy to manufacture, high efficiency in a wide range of speed and torque, and easy control, reverse operation and regenerative braking.

The rotor structure of such a switched reluctance motor is disclosed in Korean Patent Publication No. 10-2004-0042036 (Application No. 10-2002-0070157).

1 is an exemplary view showing a rotor of a conventional switched reluctance motor.

Referring to FIG. 1, an electric motor generally consists of a stator and a rotor, and generates power by rotating the rotor by electromagnetic fields generated by the stator and the rotor. For example, FIG. 1 illustrates a rotor structure of a switched reluctance motor.

The rotor of the switched reluctance motor is configured by coupling the core body 11 to the rotating shaft 21 or shaft as shown. The core body 11 is formed by stacking a plurality of core pieces 12 having a plurality of shaft holes 14 formed in the center thereof and having a plurality of protrusions 16 radially formed so as to be coupled to the rotation shaft 21.

Such a switched reluctance motor is used in various fields because the rotor is simple in configuration, high in efficiency, and easy to control. Moreover, in the case of a switched reluctance motor, the structure is simple but the driving characteristics and the control characteristics of the motor are excellent, so that a plurality of cores are formed on one rotation shaft 21 to increase the starting characteristics and the power characteristics.

The switched reluctance motor couples the core body 11 to the rotating shaft 21 using end plates, lock nuts, spacers, and keys to prevent the core body 11 from being separated and the core piece 12 from being separated. do. In addition, the rotor forms a key groove by cutting the surface of the rotation shaft 21 to fix the core body 11 to the rotation shaft 21, and to fix the core body 11 using the key groove and the key.

When manufacturing a rotor having a plurality of core bodies 11 in the conventional motor, there is a problem that it is not easy to adjust the angle formed by the protrusions 16 of the core bodies 11, that is, the skew angle.

In order to achieve the above object, an object of the present invention is to provide a rotor of an electric motor that can be easily assembled to be aligned according to a skew angle preset by a user.

In order to achieve the above object, the rotor of the electric motor according to the present invention has a columnar shaft having a long length in one direction; And a plate-shaped core ring in which a shaft hole is formed in the center, one or more core collision poles protruding from an outer circumference of the core ring, a core piece in which one or more key holes are formed, and a plurality of core pieces are stacked and And a plurality of core bodies in which the key holes of the core pieces overlap each other to form a core hole.

The key hole and the core collision pole are disposed on different normals among normals connecting the center of the shaft hole and the outer circumference of the coring.

When viewed from the direction perpendicular to the surface of the coring, the core collision pole, the core hole and the key hole are formed so as not to be parallel.

The plurality of core pieces constituting each of the plurality of core bodies are formed in the same shape.

When the said core piece turns over another core piece of the same shape, and the said protrusion and the said coring overlap so that the said keyhole of the overlapping core piece may be inconsistent.

The key hole is formed to be biased in one of a clockwise direction and a counterclockwise direction with respect to a reference line connecting the core collision pole and the shaft hole.

The key hole is formed to be symmetrical with respect to the center of the shaft hole.

The pin further penetrates the core holes and couples different core bodies to each other.

The key hole is a key groove formed in communication with the shaft hole on the inner circumference of the coring, the core hole is a core groove formed by overlapping the key groove.

The side of the shaft is formed in parallel with the one direction fixing grooves, protruding more than the side of the shaft, further comprising a keystick inserted between the core groove and the fixing groove of the core body coupled to the shaft; It is composed.

At least one of the plurality of core bodies is inverted and coupled to the shaft so that the other core bodies of the plurality of core bodies and the biased direction of the core grooves are different.

Spacer is fitted to the shaft, the spacer is disposed between the neighboring core body of the plurality of core body; further comprises.

It is further configured to include a sensor board that is coupled to the shaft and coupled to the plurality of core bodies or end plates coupled to the ends of the shaft.

The rotor of the electric motor according to the present invention can be easily assembled to be aligned according to the skew angle preset by the user.

1 is an exemplary view showing a rotor of a conventional switched reluctance motor.
Figure 2 is a perspective view showing a rotor of the electric motor according to the first embodiment of the present invention.
3 is an exploded perspective view of Fig.
4 is an exemplary view showing a core body according to the first embodiment.
5 is an exemplary view showing a core piece constituting the core body;
Figure 6 is an exemplary view for explaining the formation position of the key groove according to the first embodiment.
7 is an exemplary view for explaining the alignment of the core protrusion according to the formation position of the key groove.
8 is an exemplary view showing a core piece according to a second embodiment of the present invention.
9 is an exemplary view showing a core body according to a second embodiment.
10 is an exemplary view showing a core piece constituting the core body.
11 is an exemplary view for explaining a position where a keyhole is formed according to the second embodiment.
12 is an exemplary view for explaining the alignment of the core protrusion according to the position where the keyhole is formed.

2 is a perspective view showing a rotor of the electric motor according to the first embodiment of the present invention, Figure 3 is an exploded perspective view of FIG.

2 and 3, the rotor of the electric motor according to the first embodiment of the present invention includes a shaft 110, a core body 130, a spacer 170, and an end plate 180.

The shaft 110 serves as a rotating shaft for the rotation of the core body 130 (130a, 130b), and serves to fix the core body 130, the spacer 170 and the end plate 180. The shaft 110 serves to provide a rotational force generated through the rotor to the outside when the motor is configured using the rotor of the present embodiment. Here, an electric motor having a stator and a rotor as well as a 'switched reluctance motor' will be referred to as a 'motor'.

The shaft 110 is formed in a columnar shape having a long length in one direction. Here, one direction may be defined as the core body insertion direction. In addition, one direction may be defined as a side 111c connecting the upper surface 111a and the rear surface 111b of the shaft to be longer than the upper surface 111a and the rear surface 111b.

In addition, in the detailed description of the present invention, although the shaft 110 is formed in a cylindrical shape, it may be formed in a polygonal column like a triangular prism, a square pillar, and the present invention is not limited to the present disclosure.

In addition, the side groove 111c of the shaft 110 is formed with a fixing groove that is formed long in one direction. The key stick 120 is inserted into the fixing groove 112, and the core body 130 by the key stick 120 inserted between the core groove 136 of the core body 130 and the fixing groove 112. To be fixed at a predetermined position of the shaft 110. In addition, the fixing groove 112 is formed in parallel with the 'one direction (A)' or the shaft 110 described above. The fixing groove 112 may be formed spirally along the side surface 111c of the shaft 110, but in this case, the cost for the processing of the fixing groove 112 is expensive, the core body 130 and the keystick The manufacturing of the 120 becomes difficult, and the alignment of the core body 130 becomes difficult. Therefore, in the present invention, it will be described on the assumption that the fixing groove 112 is formed long in the 'one direction (A)' parallel to the shaft (110). On the other hand, the cross-sectional shape of the core groove 136 is generally rectangular, but may be formed in a semi-circular, polygonal shape, thereby not limiting the present invention.

The core body 130 is fitted to the shaft 110 with two or more spacers 170 therebetween, and generates a rotational force by the electromagnetic field formed between the stator and the transfer to the shaft 110 when the motor is configured do. The core body 130 has a plurality of core protrusions 137, the shaft hole 138 is formed in the center. The core body 138 is composed of a plurality of core pieces, which will be described in more detail below.

The spacer 170 is disposed between the core body 130 and the core body 130 to maintain a gap between the core body 130 when the rotor is configured. The spacer 170 is also fitted to the shaft 110, and is formed in the shape of a disc, polygonal plate having a thickness determined by the producer in one direction (A) as shown. In addition, the spacer 170 is manufactured using a synthetic resin having excellent mechanical strength and little influence on the rotor field.

The end plate 180 is coupled to at least one end of the shaft 110 to prevent the core body 130 from being separated in the 'one direction A' from the shaft 110. The end plate 180 may be used alone or in combination with a lock nut (not shown). As shown in FIG. 2, the end plate 180 is formed in a circular or polygonal plate shape and is coupled to both ends or at least one end of the shaft 110.

4 is an exemplary view showing a core body according to the first embodiment, and FIG. 5 is an exemplary view showing a core piece constituting the core body.

4 and 5, the core body 130 has one or more core salient poles 137 and a shaft hole 138 is formed in the center thereof. In addition, a core groove 136 is formed at one side of the shaft hole 138.

The core body 130 is configured by stacking a plurality of core pieces 131. In particular, the core pieces 131 are stacked to coincide with the core deviation electrode 133 and the coring ring 132 to form the core protrusion electrode 137, the shaft hole 138, and the core groove 136.

Specifically, the core piece 131 constituting the core body 130 is formed to extend horizontally with the coring surface 132a which is a surface of the coring ring 132 and the coring ring 132 formed of an ellipse or a polygonal thin plate. One or more core collision poles 133 are integrally formed. In the detailed description of the present invention, the core ring 132 is illustrated as being formed in a donut-shaped ring shape, thereby not limiting the present invention.

A shaft hole 138 corresponding to the cross-sectional shape of the shaft 110 is formed at the center of the coring surface 132a of the coring 132. The key groove 134 is formed at one side of the shaft hole 138. The key groove 134 forms the core groove 136 when the core body 130 is formed through the stacking of the core pieces 131. To this end, the key groove 134 is formed in a cross-sectional shape and in phase of the portion where the key stick 120 protrudes outside the fixing groove 112.

In particular, the key groove 134 has a defined position for alignment of the core protrusion 137. This will be described in more detail with reference to FIGS. 6 and 7.

6 is an exemplary view for explaining a formation position of the key groove according to the first embodiment. 7 is an exemplary view for explaining the alignment of the core protrusion according to the position of the key groove.

6 and 7, the key groove 134 of the core piece 131 has a defined position for forming a bias of the core protrusion 137.

Specifically, the first core body 130a and the second core body 130b of the rotor of FIG. 2 are slightly displaced from each other without the core protrusions 137 in a straight line, and this is confirmed by the legal plane T. It is possible. This is because the core body 130 is coupled to the shaft 110 by a predetermined skew angle θ.

The reason for setting the skew angle θ to the plurality of cores coupled to the rotor is to reduce the magnitude of the starting power required for the initial start of the motor, that is, the starting current, and to improve the initial operating characteristics. The core protrusion 137 is coupled to the shaft 110 by a shift of θ).

In the related art, a plurality of fixing grooves 112 are formed in the shaft 110 to adjust the skew angle θ of the core protrusion 137, and thus, each core body 130 is fixed in a different fixing groove 112. Used. However, when the plurality of fixing grooves 112 are configured as described above, it is difficult to accurately set the skew angle θ, and the process of cutting the fixing grooves 112 is difficult, thereby increasing the production cost of the motor and the rotor. there was.

Therefore, in the present invention, the core groove 136 of the core body 130 is formed to be deflected, and thus the skew angle θ of the core body 130 can be easily adjusted. In more detail, in the first embodiment of the present invention, the key groove 134 is formed to be deflected so that the core groove 136 is deflected. Then, the core body 130 is deflected when the core body 130 and the shaft 110 are coupled to the shaft 110 so that the deflection direction of the key groove 134 is on the same side (right or left), or the deflection direction. The core body 130 can be coupled so that the skew angle θ is 0 degrees or the angle preset by the user by coupling the shaft 110 to face the other side.

Specifically, referring to FIG. 6, the key groove 134 is formed to be deflected to one side based on the virtual reference line CC connecting the center CP of the salient pole at the center C1 of the shaft 110. That is, the center CKP of the key groove 134 is formed to deviate from the line of the reference line CC. At this time, the center of the key groove 134 center CKP and the core deviation pole 133, that is, the angle formed by the reference line CC and the key groove alignment line CK dl is half of the skew angle θ, that is, θ / 2. Here, the center (CP or CKP) is for explaining the formation position of the key groove 134, the position may vary depending on the shape of the core collision pole 133, the shape of the key groove 134.

When the key groove 134 is formed as described above, the plurality of core bodies 131 are manufactured and stacked to form the plurality of core bodies 130. In addition, the skew angle θ may be adjusted to 0 degrees or a predetermined angle by changing the coupling direction of the core bodies 130.

Specifically, FIG. 7 shows an example in which a pair of core bodies 130a and 130b are aligned according to the skew angle θ. In FIG. 7, only the coupling directions of the pair of core bodies 130 which are identically formed are different. That is, the first core body 130a and the second core body 130b are manufactured by stacking a plurality of core pieces 131 of the same shape in the same shape. In addition, the first core body 130a and the second core body 130b are coupled to the shaft 110 by making the positions of the core grooves 136 opposite to each other when the shaft 110 is coupled to the shaft 110. For example, in the case where the core pieces 131 are stacked on opposite surfaces, the key grooves 134 are displaced when the core deviation electrodes 133 are aligned.

That is, the first core body 130a and the second core body 130b are manufactured by stacking a plurality of core pieces 131 having the key grooves 134 formed on the right side with respect to the reference line CC. Then, only one of the first core body 130a and the second core body 130b is inverted to be coupled to the shaft 110. At this time, since only one fixing groove 112 and the keystick 120 coupled thereto are formed in the shaft 110, through which the fixing groove 112 overlaps and is aligned, the core is due to the alignment of the fixing groove 112. The protrusion 136 is shifted by the skew angle θ.

Meanwhile, the rotor of the first embodiment of the present invention has a skew angle θ of 0 degrees, that is, in order to align the core protrusions 136, the coupling direction of the first core body 130a and the second core body 130b is adjusted. Instead of changing, the key groove 134 may be matched with the biased direction.

Here, the center CP 133 or the center CKP of the key groove 134 may mean a center of symmetry. However, when the shape of the core collision pole 133 and the shape of the key groove 134 are asymmetric, when the core body 130 is aligned by the key groove 134, the core protrusion 136 of the core body 130 according to the coupling direction is provided. The center is determined by whether or not) forms a skew angle?.

8 is an exemplary view showing a core piece according to a second embodiment of the present invention.

Referring to FIG. 8, the rotor according to the second embodiment of the present invention includes a shaft 210, a core body 230, a spacer 270, and an end plate 280. In the following, the second embodiment of the present invention will be described mainly for differences from the above-described first embodiment, and detailed descriptions of the features that can be reflected through the same or the first embodiment will be omitted.

The shaft 210 is formed in a columnar shape having a long length in one direction. Here, 'one direction' may be defined as the core body insertion direction or the side surface 211c connecting the upper surface 211a and the rear surface 211b of the shaft 210 is formed long. In addition, it is generally the same as the drive shaft used for the motor, if there is no separate change in the coupling and fixing of the core body 230 is applicable to the prior art.

Unlike the above-described embodiment, the shaft 210 is not formed with a fixing groove. The rotor according to the second embodiment of the present invention is fixed to the core body 230 not separated from the shaft 210 by the end plate 280, the lock nut as in the first embodiment.

The core body 230 is fitted to the shaft 210 with two or more spacers 170 therebetween, and generates a rotational force by the electromagnetic field formed between the stator and the transfer to the shaft 210 when the motor is configured do. The core body 230 of the second embodiment also has a plurality of core protrusions 237 and a shaft hole 238 is formed in the center thereof. In addition, the core body 230 is composed of a plurality of core pieces. The core body 230 of the second embodiment of the present invention is also provided with means for setting the skew angle θ. Specifically, the core body 230 of the second embodiment has a fixing hole 236 and a fixing hole 236 formed by the key hole, unlike the key groove 134 formed by protruding the shaft hole 238 from the first embodiment. The skew angle θ between the core bodies 230 is set by the pins 239 inserted into the couplings 239. This will be described in more detail below.

The spacer 270 is disposed between the core body 230 and the core body 230 to maintain a constant gap between the core body 230 when the rotor is configured. The spacer 270 is also fitted to the shaft 210, and in particular, one or more spacer holes (not shown) for penetrating the pin 239 are formed. The pin 239 is connected to the neighboring core body 230 through the spacer hole.

The end plate 280 is coupled to at least one end of the shaft 210 to prevent the core body 230 from being separated in the 'one direction A' from the shaft 210. This endplate 280 may be used alone or in combination with a locknut (not shown). In addition, the end plate 280 may be coupled to the sensor board (not shown) for detecting the position and rotation of the rotor, thereby not limiting the present invention.

 9 is an exemplary view showing a core body according to a second embodiment, and FIG. 10 is an exemplary view showing a core piece constituting the core body.

9 and 10, the core body 230 covers one or more core salient poles 237, and a shaft hole 238 is formed in the center thereof. The core hole 236 is formed between the shaft hole 238 and the core salient pole 237.

A pin 239 is inserted into the core hole 236, and the pin 239 is coupled through one or more core bodies 230 requiring alignment and skew angle θ of the core protrusion 237. This core hole 236 is formed on the same principle as the first embodiment described above.

The core body 230 is configured by stacking a plurality of core pieces 231. In particular, the core pieces 231 are stacked such that the core pieces 231 and the core ring 232 coincide to form the core pieces 231, the shaft holes 238, and the core holes 236.

The shaft hole 238 corresponding to the cross-sectional shape of the shaft 210 is formed at the center of the coring surface 232a of the coring 232. In addition, one or more key holes 234 are formed in the coring surface 232a. The key hole 234 forms the core hole 236 when the core pieces 231 are stacked to form the core body 230. The keyhole 234 has the same shape as the cross-sectional shape of the pin 239, and can be formed in various shapes according to the shape of the pin 239. In addition, the key hole 234 can be formed anywhere on the coring surface 232a. However, when the key hole 234 is formed on the core colliding electrode 233, disturbance of the electromagnetic field may occur. Do. However, the present invention is not limited thereto.

The key hole 234 has a defined position for aligning the core protrusion 237 as with the key groove 134 of the first embodiment.

11 is an exemplary view for explaining a position of forming a keyhole according to the second embodiment. 12 is an exemplary view for explaining the alignment of the core protrusions according to the position where the keyhole is formed.

11 and 12, the key hole 234 of the core piece 231 is formed at a position to form a bias of the core protrusion 237.

Specifically, the rotor is composed of a first core body 230a and a second core body 230b, and the core protrusions 237 of the first core body 230a and the second core body 230b are aligned in a straight line according to the coupling method. It is possible to align them or shift them to form a predetermined skew angle θ. In FIG. 8, an example in which the first core body 230a and the second core body 230b are shifted from each other by the skew angle θ by the legal plane T is illustrated.

In this second embodiment, the shaft 210 is configured such that the first core body 230a and the second core body 230b are shifted by the skew angle θ or the skew angle θ is 0 degrees for the same reason as the first embodiment. ) Is combined. It is possible to easily set the skew angle θ between the cores 230a and 230b according to the coupling method even when the number of the core bodies 230 increases.

In the second embodiment, unlike the first embodiment, one or more keyholes 234 are formed on the coring 232. The key hole 234 is formed to be deflected, and the skew angle θ between the core bodies 230 can be adjusted by the pin 239 inserted into the key hole 234.

In more detail, in the second embodiment of the present invention, the key hole 234 is deflected so that the core hole 236 is deflected. The core hole 236 between the core bodies 230 is connected by the pins 239 to maintain the deflected state, thereby setting and maintaining the skew angle θ between the core bodies 230. Specifically, the core body 230 deflected when the core body 230 and the shaft 210 are coupled to the shaft 210 so that the deflection direction of the key hole 234 is the same (either right or left). The skew angle θ can be set to 0 degrees, or can be shifted by a predetermined skew angle θ such that the skew angle θ is different from each other.

As shown in FIG. 11, the keyhole 234 is clocked based on a virtual reference line CC connecting the center O of the shaft 210 or the center CP of the protrusion at the center O of the shaft hole 238. It is formed to be deflected in the direction (right) or counterclockwise (left). That is, the center O2 of the key hole 234 is formed to be out of the line of the reference line CC. In this case, the angle formed by the center O2 of the key hole 234 and the center CP of the core collision pole 233, that is, the reference line CC and the key groove alignment line CK, is half of the skew angle θ, θ / Becomes two. Here, the centers (O, O2) are for explaining the position of the key hole 234, the position may vary depending on the shape of the core collision pole 233, the shape of the key hole 234.

The key hole 234 is formed as described above, and a plurality of core bodies 130 are formed by manufacturing and stacking the plurality of core pieces 231 having the same shape. The skew angle θ may be adjusted to 0 degrees or the angle set by the keyhole 234 by changing the coupling direction of the core bodies 130.

Meanwhile, the key holes 234 may be formed at positions symmetrical with respect to the center O, or a plurality of key holes 234 may be formed at equal intervals.

12 is an explanatory view for explaining the position where the keyhole 234 is formed. In FIG. 12, unlike the case of FIG. 7, two core pieces 231 are overlapped, one sheet is turned upside down, and the core collision pole 233 and the coring 232 coincide with each other.

As described above, the rotor of the present invention forms the key hole 234 to one side with respect to the reference line CC, thereby forming the core body 230. When the core body 230 and the shaft 210 are coupled, the coupling direction of the core body 230 is adjusted to make the skew angle θ to 0 degrees or to be aligned according to a predetermined skew angle θ.

 That is, if one of the two pieces of the core piece 231 manufactured in the same manner as shown in FIG. 12 is turned upside down, the core ring 232 and the core deviation electrode 233 overlap with each other, and as shown in FIG. It can be seen that 234a and 234b are symmetrical with reference line CC interposed therebetween.

At this time, it can be seen that the angle formed by the line connecting the centers O2 and O2 'of the keyholes 234a and 234b and the center O of the shaft hole 238 is the skew angle θ. In other words, it can be seen that when the key holes 234a and 234b overlap in this state, the core deviation poles 233 are shifted by the skew angle θ.

And the holding of the skew angle θ is to be maintained by the pin 239 coupled across the core body 230, so that the rotor according to the second embodiment of the present invention is set and skew angle of the skew angle (θ) The fixing according to (θ) is free and easy to assemble and produce. In particular, since it is possible to boil and produce the rotor without using a high-cost, high-latency cutting process, it is possible to shorten the production period and to reduce the production cost.

11 core body 12 core
14: axon 16: the pole
21: shaft 110: shaft
112: fixing groove 120: key stick
130: core body 131: core
132: Coring 133: Core deviation pole
134: key groove 136: core groove
137: core protrusion 138: shaft hole
170: spacer 180: end plate

Claims (13)

A columnar shaft having a long length in one direction; And
A core having a plate-shaped core ring in which a shaft hole is formed in the center, one or more core collision poles protruding from an outer circumference of the core ring, a core piece having one or more key holes formed therein, and a plurality of core pieces being stacked And a plurality of core bodies each of the keyholes overlapping each other to form a core hole. The method of claim 1,
And the key hole and the core collision pole are disposed on different normals among normals connecting the center of the shaft hole and the outer circumference of the coring. The method of claim 1,
When viewed from the direction perpendicular to the surface of the coring
And the core collision pole, the core hole and the key hole are not parallel to each other. The method of claim 1,
The plurality of core pieces constituting each of the plurality of core bodies are formed in the same shape. The method of claim 4, wherein
And the core piece inverts the other core pieces of the same shape so that the keyholes of the overlapping core pieces are inconsistent when the protrusions and the coring overlap with each other. The method of claim 1,
And the key hole is formed to be biased in one of a clockwise direction and a counterclockwise direction with respect to a reference line connecting the core collision pole and the shaft hole. 7. The method according to any one of claims 2 to 6,
And the keyhole is formed to be symmetrical with respect to the center of the shaft hole. The method of claim 7, wherein
And a pin penetrating the core holes to mutually couple different core bodies to each other. 7. The method according to any one of claims 2 to 6,
And the key hole is a key groove formed in communication with the shaft hole at an inner circumference of the coring ring, and the core hole is a core groove formed by overlapping the key groove. The method of claim 9,
The side of the shaft is formed with a fixing groove parallel to the one direction,
A rotor protruding from a side of the shaft, the rotor further comprises a keystick inserted between the core groove and the fixing groove of the core body coupled to the shaft. The method of claim 9,
At least one of the plurality of core bodies
The rotor of the plurality of core body is inverted so that the biased direction of the core groove and other core body is changed to be coupled to the shaft. The method of claim 1,
And a spacer coupled to the shaft and disposed between neighboring core bodies of the plurality of core bodies. The method of claim 1,
And a sensor board fitted to the shaft and coupled to the plurality of core bodies or end plates coupled to the ends of the shaft.

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