KR20210026884A - Electric motor and compressor having the same - Google Patents

Abstract

The present invention relates to an electric motor and a compressor having the same. The electric motor of the present invention comprises: a stator; and a rotor rotatably disposed with respect to the stator, wherein the rotor includes: a rotating shaft; a first core having a rotation shaft hole into which the rotation shaft is inserted; and a second core provided on one side of the first core along an axial direction, having the rotation shaft is disposed therein, and having a first cut-out space unit cut to have an inner diameter surface extending in a radial direction from an outer surface of the rotation shaft and a first inner balance weight formed on an opposite side of the first cut-out space. Accordingly, the length of the balance weight protruding in the axial direction can be reduced.

Description

Electric motor and compressor equipped with it {ELECTRIC MOTOR AND COMPRESSOR HAVING THE SAME}

The present invention relates to an electric motor and a compressor having the same.

As is well known, the compressor includes a compression unit that compresses a refrigerant and an electric motor that provides a driving force to the compression unit.

The electric motor includes a stator and a rotor disposed rotatably with respect to the stator.

The rotor includes a rotation shaft and a rotor core rotated about the rotation shaft.

The rotation shaft is provided with an eccentric portion coupled to the compression portion to move eccentrically.

The rotor core is provided with a balance weight for generating an unbalanced force in the opposite direction corresponding to the unbalanced force generated in one direction generated by the eccentric portion.

However, in the motor of such a conventional compressor, balance weights are provided at both ends of the rotor, and thus there is a problem that the axial length of the motor increases.

In addition, since the balance weight is formed of a relatively expensive aluminum member, it causes an increase in manufacturing cost.

In addition, there is a problem that the overhang design of the rotor of the electric motor becomes difficult due to the installation of the balance weight.

KR 1020090077591 A KR 1020060031294 A

Accordingly, an object of the present invention is to provide an electric motor capable of shortening the axial length of a rotor and a compressor having the same.

In addition, an object of the present invention is to provide an electric motor capable of reducing the length of a balance weight protruding in the axial direction, and a compressor having the same.

Another object of the present invention is to provide an electric motor in which the rotor protrudes in the axial direction from the end of the stator, and a compressor having the same.

In addition, another object of the present invention is to provide an electric motor capable of reducing the manufacturing cost of a balance weight and a compressor having the same.

The electric motor according to the present invention for solving the above-described problems is technically characterized in that an unbalance force is generated during rotation by cutting an inner region of the rotor core along the radial direction of the rotor.

Specifically, a rotation shaft is inserted in the center of the rotor core, and an area is cut along the radial direction around the rotation shaft to form a cutout space, thereby generating an unbalanced force on the opposite side of the cutout space. ) Is formed, it is possible to eliminate the use of a balance weight protruding in the axial direction at the end of the rotor core or to significantly reduce the protruding length of the balance weight.

The electric motor includes a stator; And a rotor disposed rotatably with respect to the stator, wherein the rotor comprises: a rotation shaft; And a rotor core coupled to the rotation shaft, wherein the rotor core includes: a first core having a rotation shaft hole into which the rotation shaft is inserted; And a first cut-out space portion provided on one side of the first core along an axial direction, the rotation shaft disposed therein, and cut to have an inner diameter surface extending in a radial direction from an outer surface of the rotation shaft. And a second core having a first inner balance weight formed on the opposite side of the first cut-out space.

The electric motor includes a second cut-out space portion having the rotation shaft disposed therein and an inner diameter surface extending in a radial direction from an outer surface of the rotation shaft, and a second inner formed on the opposite side of the second cut-out space portion. It is configured to further include; a third core having a balance weight.

The first and second cutout spaces, and the first inner balance weight and the second balance weight are each formed in rotational symmetry.

Accordingly, the second core and the third core can be easily manufactured by using the same mold.

The second core and the third core are coupled to both ends of the first core so that the first inner balance weight and the second inner balance weight face each other around the rotation axis.

The first core, the second core, and the third core are configured to have different stacking heights, respectively.

The stacking height of the first core is composed of 28 to 36% of the height of the rotor core (the sum of the heights (axial length) of the first core, the second core, and the third core).

The stacking height of the second core is composed of 40 to 52% of the height of the rotor core.

The stacking height of the third core is composed of 20 to 24% of the height of the rotor core.

The stator includes a stator core and a stator coil wound around the stator core.

The second core includes an overhang section protruding from the stator core along the axial direction.

Accordingly, the efficiency of the electric motor may be improved by reducing copper loss through an increase in the counter electromotive force of the electric motor.

Moreover, when the electric motor is provided in the compressor, the efficiency fluctuation is reduced due to the increase in the inertia of the rotor due to the overhang section, which is advantageous in terms of the performance of the compressor.

The overhang section of the second core is formed to a height of 23 to 29% of the sum of the heights of the first core, the second core, and the third core before the overhang section is applied.

The overhang section of the second core is formed to be 8 to 10 mm when the sum of the heights of the first core, the second core, and the third core is 35 mm before the overhang section is applied.

The third core includes an overhang section protruding compared to the stator core along the axial direction.

As a result, the back electromotive force of the electric motor is further increased, so that the efficiency of the electric motor can be further improved.

In particular, when the electric motor is provided in the compressor, since the inertia of the rotor due to the overhang section is further increased, the efficiency fluctuation can be further reduced, thereby ensuring a more stable compressor performance.

The height of the overhang section of the third core is formed to a height of 14 to 26% of the sum of the heights of the first core, the second core, and the third core before the application of the overhang section of the second core and the third core.

The height of the overhang section of the third core is that of the third core when the sum of the heights of the first core, the second core, and the third core before application of the overhang section of the second core and the third core is 35 mm. The overhang section is formed from 5 to 9 mm.

The rotation shaft has an eccentric portion, and in the second core, the first inner balance weight is disposed on an opposite side of the eccentric portion.

The eccentric portion includes a crank arm protruding along a radial direction of the rotation shaft and spaced apart in an axial direction, a crank pin connecting the crank arm, and a counter weight disposed on an opposite side of the crank arm.

Here, the second core is coupled such that the first inner balance weight is disposed on the opposite side of the crankpin.

The third core is coupled such that a second inner balance weight is disposed on the crankpin side.

The electric motor is configured to further include an outer balance weight coupled to the end of the rotor core so as to protrude in the axial direction.

The outer balance weight is provided at an end of the second core.

The outer balance weight is configured to generate an unbalance force cooperatively with the first inner balance weight.

And an outer balance weight protrudingly coupled to an end portion of the second core to protrude along an axial direction corresponding to the first inner balance weight.

The outer balance weight is formed of a non-magnetic material.

The outer balance weight is formed of an aluminum (Al) member.

The outer balance weight is formed with an outer diameter surface corresponding to the outer diameter of the second core and an inner diameter surface corresponding to the inner diameter surface of the first cut-out space part.

The outer balance weight is configured to have a thickness of 2.8 to 8.6% of the sum of the axial lengths of the first core, the second core, and the third core.

On the other hand, according to another field of the present invention, the case; A compression unit provided inside the case; And the electric motor of claim 1 which is provided inside the case and provides a driving force to the compression unit.

Here, the compression unit, the cylinder; A piston reciprocally disposed inside the cylinder; And a connecting rod having one end connected to the piston and the other end connected to the rotating shaft of the electric motor.

As described above, according to an embodiment of the present invention, a first core to which a rotation shaft is coupled, and a rotation shaft therein, and a cut-out space portion cut to have an inner diameter surface extending in a radial direction from an outer surface of the rotation shaft. And a second core provided on one side of the first core with an inner balance weight formed on the opposite side of the cut-out space part, thereby suppressing the use of a balance weight protruding in the axial direction from the end of the rotor. have.

Thereby, an electric motor capable of shortening the axial length is provided.

Further, by suppressing the use of a relatively expensive balance weight, it is possible to reduce the manufacturing cost of the electric motor.

In addition, the use of the balance weight protruding from the end of the rotor in the axial direction is suppressed, and the rotor is configured to include an overhang section protruding in the axial direction from the end of the stator core, thereby reducing the copper loss caused by the rise of the back EMF Efficiency can be improved.

In addition, when the motor configured including an overhang section is provided in the compressor, the efficiency fluctuation is reduced due to an increase in inertia of the rotor due to the overhang section, thereby providing a compressor advantageous in terms of performance.

In addition, by further including a third core having a second cut-out space portion and a second inner balance weight therein, it is possible to more easily adjust the magnitude of the unbalance force generated when the rotor is rotated.

In addition, by further providing an outer balance weight protruding in the axial direction at the end of the second core, it is possible to more easily adjust the magnitude of the unbalance force generated when the rotor is rotated.

1 is a cross-sectional view of a compressor equipped with an electric motor according to an embodiment of the present invention,
2 is a perspective view of the eccentric region of FIG. 1;
Figure 3 is an enlarged view of the main part of Figure 1,
Figure 4 is an exploded perspective view of the rotor of Figure 1,
5 is a plan view of the first core of FIG. 4;
6 is a plan view of the second core of FIG. 4;
7 is a plan view of the third core of FIG. 4;
FIG. 8 is a view showing a state in which the rotation shaft of the rotor of FIG. 1 is coupled;
9 is a view for explaining the unbalanced force of the electric motor of FIG. 1;
10 is a cross-sectional view of a compressor equipped with an electric motor according to another embodiment of the present invention;
11 is an enlarged view of the main parts of the electric motor of FIG. 10;
12 is a view for explaining a coupled state of the rotation shaft of the rotor of FIG. 10;
13 is a view for explaining the unbalanced force of the electric motor of FIG. 10;
14 is a cross-sectional view of a compressor equipped with an electric motor according to another embodiment of the present invention;
15 is an enlarged view of the main parts of the electric motor of FIG. 14;
16 is a perspective view showing a state of use of the outer balance weight of the electric motor of FIG. 14;
17 is a perspective view of the outer balance weight of FIG. 16;
18 is a plan view of the outer balance weight of FIG. 17;
19 is a view for explaining a coupled state of the rotation shaft of the rotor of FIG. 14;
20 is a diagram for explaining an unbalanced force of the electric motor of FIG. 14.

Hereinafter, exemplary embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings. In the present specification, the same/similar reference numerals are assigned to the same/similar configurations even in different embodiments, and the description is replaced with the first description. Singular expressions used in the present specification include plural expressions unless the context clearly indicates otherwise. In addition, in describing the embodiments disclosed in the present specification, when it is determined that a detailed description of related known technologies may obscure the subject matter of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. In addition, it should be noted that the accompanying drawings are for easy understanding of the embodiments disclosed in the present specification, and the technical spirit disclosed in the present specification is not to be construed as being limited by the accompanying drawings.

1 is a cross-sectional view of a compressor equipped with an electric motor according to an embodiment of the present invention.

As shown in FIG. 1, the compressor of this embodiment includes a case 110, a compression unit 200, and an electric motor 300.

A sealed accommodation space is formed inside the case 110. A suction pipe 115 through which refrigerant is sucked is provided at one side of the case 110.

A compression unit 200 for compressing a refrigerant is provided inside the case 110. The compression part 200 is installed in the upper inner region of the case 110. The compression unit 200 includes a cylinder 210 and a piston 220 provided inside the cylinder 210. The piston 220 is provided with a connecting rod 230 for power transmission. A discharge valve 213 is provided on one side of the cylinder 210. A discharge cover 214 is provided outside the discharge valve 213. A suction muffler 215 is provided on the refrigerant suction side through which the refrigerant is sucked into the cylinder 210. The suction muffler 215 is connected to the suction pipe 115. A discharge muffler 217 is provided on a refrigerant discharge side connected to the discharge cover 214. Although not specifically shown in the drawing, a discharge pipe extending to the outside of the case 110 is connected to the discharge muffler 217.

A liquid refrigerant and oil (O) are stored in a lower area inside the case 110 to maintain a preset height. The electric motor 300 is provided below the compression unit 200.

The electric motor 300 includes a stator 310 and a rotor 360 rotatably disposed with a predetermined air gap G with respect to the stator 310.

The rotor 360 includes a rotation shaft 340, a rotor core 370 rotated about the rotation shaft 340, and a permanent magnet 410 coupled to the rotor core 370. The rotation shaft 340 has a vertical length, one side region is coupled to the electric motor 300 and the other side region extends upward and is disposed on the compression unit 200.

An oil passage 342 is formed in the rotary shaft 340 to supply the oil O of the bottom to the upper side. An oil guide 344 is provided at the lower end of the rotation shaft 340 to guide the oil O of the bottom portion upwardly during rotation. The oil O guided upward by the oil guide 344 is moved to the upper region of the rotation shaft 340 along the oil passage 342. The oil (O) moved to the upper region of the rotation shaft 340 moves downward (falling) to promote cooling of the contact portion and cooling and lubrication of the moving portion.

An eccentric portion 350 is provided at an upper end of the rotation shaft 340. The eccentric part 350 is disposed in the compression part 200. The eccentric part 350 is coupled to the other end of the connecting rod 230 having one end connected to the piston 220. Accordingly, when the rotation shaft 340 rotates, the piston 220 reciprocates within the cylinder 210 by the eccentric portion 350 and the connecting rod 230.

FIG. 2 is a perspective view of an eccentric portion 350 of FIG. 1, and FIG. 3 is an enlarged view of a main part of FIG. As shown in Figure 2, the frame 120 is provided on the lower side of the cylinder 210. An eccentric portion 350 of the rotation shaft 340 is disposed above the frame 120. The upper region of the rotation shaft 340 is rotatably supported by a bearing 125 provided in the frame 120. The bearing 125 extends downward in the axial direction from the bottom of the frame 120. The rotor 360 is disposed under the bearing 125. A region of the upper end of the rotation shaft 340 is inserted into the bearing 125 and is rotatably supported.

The eccentric portion 350 includes a crank arm 351 and a crank pin 352 disposed in parallel with a rotation shaft 340 on the crank arm 351. One end of the connecting rod 230 is coupled to the crank pin 352 to enable a relative motion. The crank arm 351 is formed to protrude from the rotation shaft 340 in a radial direction. The crank pin 352 is disposed in parallel with the rotation shaft 340 at the free end of the crank arm 351. One end of the connecting rod 230 is connected to the crank pin 352 to enable relative movement, so that the crank pin 352 moves eccentrically with respect to the center of the rotation shaft 340 when the rotation shaft 340 is rotated. As a result, one end of the connecting rod 230 rotates around the rotation shaft 340, and the piston 220 connected to the other end of the connecting rod 230 reciprocates the inside of the cylinder 210. You will exercise. The refrigerant is sucked into the cylinder 210 by a piston 220 reciprocating inside the cylinder 210 and compressed, and the compressed refrigerant is discharged to the outside of the cylinder 210.

The eccentric portion 350 is configured with a counter weight 353 formed to generate an unbalanced force on the opposite side of the crank pin 352. As is well known, the counter weight 353 is disposed so that its center of gravity faces in a direction opposite to the center of gravity of the crank pin 352, the connecting rod 230, and the piston 220. Accordingly, an unbalance force in a direction opposite to that generated by the crank pin 352, the connecting rod 230, and the piston 220 is generated.

The stator 310 includes, for example, a stator core 320 and a stator coil 330 wound around the stator core 320. The stator core 320 is formed by insulatingly stacking a plurality of electrical steel sheets 322, for example. A rotor receiving hole 323 through which the rotor 360 is rotatably accommodated is formed inside the stator core 320. The stator core 320 has a plurality of slots 324 and teeth 325 formed alternately along the circumferential direction of the rotor receiving hole 323. Each of the stator coils 330 is wound in a preset pattern via the slots 324. The upper side of the stator 310 is supported by the frame 120. A plurality of support portions 130 are provided below the stator 310. The plurality of support parts 130 are each provided with a plurality of spring members 135 that can expand and contract in the vertical direction and a leg part 140 coupled to a lower end of the spring member 135, respectively. The spring member 135 is implemented as a compression coil spring. As a result, vibrations of the compression unit 200 and the electric motor 300 may be alleviated.

The rotor 360 includes a rotation shaft 340 and a rotor core 370 that rotates around the rotation shaft 340. The rotor core 370 is formed by insulatingly stacking a plurality of electrical steel sheets 372, for example.

The rotor 360 includes, for example, a plurality of permanent magnets 410 coupled to the rotor core 370. The plurality of permanent magnets 410 are formed such that different magnetic poles are alternately disposed along the circumferential direction of the rotor core 370. The rotor core 370 is provided with a plurality of permanent magnet insertion portions 384 through which the plurality of permanent magnets 410 can be inserted in the axial direction. The plurality of permanent magnets 410 are each implemented in, for example, an arc shape. The permanent magnet 410 is coupled such that, for example, a central convex surface faces the center side (inside) of the rotor core 370. The permanent magnet 410 is disposed with a concave surface facing the outside of the rotor core 370. Both ends of the permanent magnet 410 are disposed close to the outer circumference of the rotor core 370, respectively. The rotor 360 includes end plates 420 respectively coupled to both ends of the rotor core 370. Each of the end plates 420 has a circular plate shape, and is formed to block the plurality of permanent magnet insertion portions 384. Thereby, the plurality of permanent magnets 410 may be prevented from being separated in the axial direction. A rotation shaft hole 424 is formed through the center of each end plate 420 so that the rotation shaft 340 can be inserted. Each of the end plates 420 has a fastening member insertion portion 426 through which each of the plurality of fastening members 425 coupled in the axial direction to the rotor core 370 are respectively inserted and coupled.

In this embodiment, the motor 300 is described as an example in which the rotor 360 includes a plurality of permanent magnets 410 and is configured as a synchronous motor 300, but the motor 300 has a rotor It may be composed of an induction motor having a plurality of conductor bars and a short-circuit ring. In addition, the electric motor 300 may be configured as a synchronous reluctance motor in which the rotor includes a plurality of flux barrier groups along the circumferential direction and a plurality of magnetic poles are formed by a difference in magnetoresistive resistance.

The rotor core 370 of this embodiment is configured with a first core 380 and a second core 390 coupled along the axial direction.

The first core 380 is configured with a rotation shaft hole 381 penetrating through the center so that the rotation shaft 340 can be inserted.

The second core 390 includes a first cut-out space portion 393 having the rotation shaft 340 disposed therein, and having an inner diameter surface extending from an outer surface of the rotation shaft 340 in a radial direction, and It is configured with a first inner balance weight 395 formed to have a mass difference on the opposite side of the first cut-out space portion 393. Accordingly, when the rotor 360 rotates, an unbalance force is generated in the second core 390 due to a mass difference between the first cutout space 393 and the first inner balance weight 395. The unbalanced force of the second core 390 acts in the direction of the center of gravity of the first inner balance weight 395.

The second core 390 is coupled to one side (upper side in the drawing) of the first core 380 along the axial direction.

The rotor core 370 of this embodiment includes a first core 380, a second core 390, and a third core 400 coupled along the axial direction.

The third core 400 includes a second cut-out space portion 403 having the rotation shaft 340 disposed therein, and having an inner diameter surface extending from an outer surface of the rotation shaft 340 in a radial direction, and It is configured with a second inner balance weight 405 formed on the opposite side of the second cut-out space part 403. Accordingly, when the rotor 360 rotates, the third core 400 generates an unbalance force due to a mass difference between the second cut-out space 103 and the second inner balance weight 405. The unbalanced force of the third core 400 acts in the direction of the center of gravity of the second inner balance weight 405.

The third core 400 is coupled to the other side (the lower side in the drawing) of the first core 380 along the axial direction.

4 is an exploded perspective view of the rotor 360 of FIG. 1, FIG. 5 is a plan view of the first core 380 of FIG. 4, and FIG. 6 is a plan view of the second core 390 of FIG. 4, and FIG. 7 is A plan view of the third core 400 of FIG. 4. 4, in this embodiment, the first core 380, the second core 390, and the third core 400 are configured to have different stacking heights (or axial lengths). I can. More specifically, for example, the first core 380 is the height of the rotor core 370 (the height of the first core 380, the height of the second core 390, and the third core 400) It may be configured to have a height (axial length) of 28 to 36% of the sum of the heights of. The second core 390 may be configured to have a height of 40 to 52% of the height of the rotor core 370. The third core 400 may be configured to have a height of 20 to 24% of the height of the rotor core 370. However, this is only an example, and the height of the first core 380, the height of the second core 390, and the height of the third core 400 may be appropriately adjusted.

The first core 380 is configured with a rotation shaft hole 381 in the center into which the rotation shaft 340 is inserted, as shown in FIG. 5. The first core 380 is provided with a plurality of permanent magnet insertion portions 384 penetrating in the axial direction so that both ends of the plurality of permanent magnets 410 are disposed close to the circumference, respectively. A plurality of fastening member insertion portions 386 are respectively formed through the first core 380 so that the fastening members 425 can be respectively inserted therethrough.

The second core 390 has an inner diameter extending radially from an outer surface of the rotation shaft 340 on one side (right side in the drawing) with the rotation shaft 340 disposed in the center, as shown in FIG. 6 A first cut-out space portion 393 cut to have a surface is formed. A first inner balance weight 395 is formed on the opposite side (left side in the drawing) of the first cut-out space portion 393.

The first cutout space 393 and the first inner balance weight 395 are each configured to have a substantially semicircular shape. Both ends of the first cutout space 393 and both ends of the first inner balance weight 395 may be disposed on an extension line extending through the center of the rotation shaft 340, respectively. Accordingly, the side on which the first inner balance weight 395 is formed with respect to the vertical center line of the rotation shaft 340 has a larger mass than the side on which the first cut-out space portion 393 is formed. During rotation, a large unbalance force may act on the second core 390 toward the first inner balance weight 395. The second core 390 includes a plurality of permanent magnet insertion portions 384 having both ends formed close to the outer periphery. The second core 390 includes a plurality of fastening member insertion portions 386 penetrating in the axial direction so that the fastening member 425 can be inserted.

The first inner balance weight 395 is provided with a rotation shaft contact portion 391 having an arc shape so as to contact the outer surface of the rotation shaft 340. The rotation shaft contact portion 391 has a concave arc shape having a semicircle size. The first inner balance weight 395 includes both side wall portions 392 extending outwardly along a radial direction at both ends of the rotation shaft contact portion 391, respectively.

The first cut-out space portion 393 extends along a circumferential direction to have an inner diameter of a preset size from both side wall portions 392 and the both side wall portions 392 of the first inner balance weight 395 It has a semicircular inner diameter surface 393a.

As shown in FIG. 7, the third core 400 has an inner diameter extending radially from the outer surface of the rotation shaft 340 on one side (left side in the drawing) and the rotation shaft 340 disposed in the center. A second cut-out space portion 403 is cut to have a surface 403a. A second inner balance weight 405 is formed on the opposite side (right side of the drawing) of the second take-up space part. As a result, the side where the second inner balance weight 405 is formed with respect to the vertical center line of the rotation shaft 340 has a larger mass than the side where the second cut-out space portion 403 is formed. During rotation, an unbalance force may act on the third core 400 toward the second inner balance weight 405. The third core 400 includes a plurality of permanent magnet insertion portions 384 having both ends formed close to the outer circumference. The third core 400 includes a plurality of fastening member insertion portions 386 penetrating in the axial direction so that the fastening member 425 can be inserted.

The second inner balance weight 405 is provided with a rotation shaft contact portion 401 having an arc shape so as to contact the outer surface of the rotation shaft 340. The rotation shaft contact portion 401 has a concave arc shape having a semicircle size. The second inner balance weight 405 is provided with both side wall portions 402 extending outwardly along a radial direction at both ends of the rotation shaft contact portion 401.

The second cut-out space part 403 extends along the circumferential direction to have an inner diameter of a preset size from both side wall parts 402 and the both side wall parts 402 of the second inner balance weight 405. It has an inner diameter surface 403a of a semicircle size.

Here, the permanent magnet insertion portions 384 of the first core 380, the second core 390, and the third core 400 are respectively formed to communicate with each other in the axial direction. In addition, each of the fastening member insertion portions 386 of the first core 380, the second core 390, and the third core 400 are formed to communicate with each other in the axial direction.

The second core 390 and the third core 400 are formed to be rotationally symmetric about the rotation shaft 340.

The first inner balance weight 395 and the second inner balance weight 405 are formed to be rotationally symmetric with respect to the rotation shaft 340.

The first cutting space 393 and the second cutting space 403 are formed to be rotationally symmetrical with respect to the rotation shaft 340.

According to this configuration, the second core 390 and the third core 400 may be made of the same mold. The mold for manufacturing the rotor core 370 according to the present embodiment may include a mold for the first core 380 and a mold for the second core 390 and the third core 400. Accordingly, manufacturing of the rotor core 370 (the second core 390 and the third core 400) may be facilitated.

FIG. 8 is a view showing a coupled state of the rotation shaft 340 of the rotor 360 of FIG. 1, and FIG. 9 is a view for explaining the unbalanced force of the electric motor 300 of FIG. 1. 8, the second core 390 is coupled to the upper side of the first core 380 along the axial direction, and the third core 400 is attached to the lower side of the second core 390 Can be combined. The rotation shaft 340 is coupled to the inside of the rotor core 370 to which the first core 380, the second core 390, and the third core 400 are combined. One end of the connecting rod 230 is coupled to the crank pin 352 of the eccentric portion 350 of the upper end of the rotation shaft 340. A piston 220 is coupled to the other end of the connecting rod 230.

More specifically, when the crank pin 352 is disposed to the right in the drawing of the vertical center line of the rotation shaft 340, the counter weight 353 of the eccentric portion 350 is the opposite side of the crank pin 352 It is placed as (left on the drawing).

The first inner balance weight 395 of the second core 390 is disposed on the opposite side of the crank pin 352 (left side in the drawing), that is, toward the counter weight 353.

The first cutout space 393 of the second core 390 is disposed toward the crankpin 352 (right side in the drawing).

The second inner balance weight 405 of the third core 400 is disposed toward the crank pin 352 (right side in the drawing).

The second cut-out space part 403 of the third core 400 is disposed on the opposite side (left side in the drawing) of the crank pin 352.

With this configuration, when the rotor 360 rotates, the rotation shaft 340 has a first unbalance force F1 generated by the crank pin 352 and the piston 220, and the counter weight 353 The second unbalanced force F2 generated by this, the third unbalanced force generated by the first inner balance weight 395 and the fourth unbalanced force generated by the second inner balance weight 405 are respectively generated. .

The first inner balance weight 395 and the second inner balance weight 405 are the sum of the first unbalanced force, the second unbalanced force, the third unbalanced force, and the fourth unbalanced force (ΣF=F1-F2- F3+F4) are each formed so that it can be minimized.

As shown in FIG. 9, when the first inner balance weight 395 of the second core 390 and the second inner balance weight 405 of the third core 400 are not applied, the unbalance force is relatively It is shown as a first curve C1 of a large and wide ellipse shape.

The unbalance force in this embodiment to which the first inner balance weight 395 of the second core 390 and the second inner balance weight 405 of the third core 400 are applied is an ellipse as in the second curve C2. It is shown by the second curve C2 of the shape. Here, the second curve C2 has a long length in the y-axis direction.

The balancing effect of this embodiment to which the first inner balance weight 395 of the second core 390 and the second inner balance weight 405 of the third core 400 are applied is almost as shown in the third curve C3. It is shown as a circle. The third curve C3 has a relatively small diameter.

With this configuration, the second core 390 is disposed at the upper end of the first core 380 and the third core 400 is disposed at the lower end of the first core 380. The permanent magnets 410 are inserted into the respective permanent magnet insertion portions 384 of the first core 380, the second core 390, and the third core 400 communicated with each other. When the coupling of the permanent magnets 410 is completed, the end plates 420 are respectively coupled to both ends of the rotor core 370 so that the axial separation of the permanent magnets 410 can be suppressed.

The other end of the connecting rod 230 having one end coupled to the piston 220 is coupled to the eccentric portion 350 of the rotation shaft 340.

When the operation is started and power is applied to the stator 310, the rotor 360 is rotated by the interaction between the magnetic field formed by the stator coil 330 and the magnetic force of the permanent magnet 410. It is rotated around.

When the rotor 360 rotates, a first unbalance force formed in a first direction by the piston 220 and the crank pin 352, formed in a second direction opposite to the counter weight 353 A second unbalanced force formed in the second direction by the first inner balance weight 395, and a fourth unbalanced force formed in the first direction by the second inner balance weight 405 As the force is canceled and reduced, vibration and noise generation of the rotor 360 may be suppressed.

In this embodiment, a case where the second core 390 is provided at the upper end of the first core 380 and the third core 400 is provided at the lower end of the first core 380 will be described as an example. However, the rotor core 370 is provided with a second core 390 on the upper end of the first core 380, and the height of the first core 380 and the height of the second core 390 are adjusted. It can also be configured.

Hereinafter, another embodiment of the present invention will be described with reference to FIGS. 10 to 20. 10 is a cross-sectional view of a compressor equipped with an electric motor according to another embodiment of the present invention. As shown in FIG. 10, the compressor of this embodiment includes a case 110, a compression unit 200, and an electric motor 300a.

The compression unit 200 includes a cylinder 210, a piston 220 reciprocating within the cylinder 210, and one end is connected to the cylinder 210 and the other end is connected to the electric motor 300a. It is provided with a connecting rod (230).

The electric motor 300a of the present embodiment includes a stator 310 and a rotor 360a that is rotatably disposed with a predetermined air gap G with respect to the stator 310.

The rotor 360a may include a rotation shaft 340; A rotor core 370a having a first core 380a, a second core 390a, and a third core 400a, and a plurality of permanent magnets 410 coupled to the rotor core 370a. .

The first core 380a, the second core 390a, and the third core 400a are coupled to be in contact with each other in the axial direction. More specifically, the second core 390a is coupled to one side (upper side in the drawing) of the first core 380a, and the third core 400a is the other side of the first core 380a ( It is connected to the lower side of the drawing).

The rotation shaft 340 has a long length, and one end (top portion in the drawing) extends upward and is disposed on the compression unit 200. The rotation shaft 340 includes an eccentric portion 350 that moves eccentrically during rotation. One end of the connecting rod 230 is connected to the eccentric part 350 so as to be able to move relative to each other.

The first core 380a has a rotation shaft hole 381 formed through the center so that the rotation shaft 340 may be coupled. The first core 380a includes a plurality of permanent magnet insertion portions 384 through which a plurality of permanent magnets 410 can be inserted in the axial direction. The first core 380a includes a plurality of fastening member insertion portions 386 penetrating in the axial direction so that the plurality of fastening members 425 can be inserted.

The second core 390a includes a first cut-out space 393 having the rotation shaft 340 disposed therein and an inner diameter surface 393a extending radially from the outer surface of the rotation shaft 340. ) And a first inner balance weight 395 formed on an opposite side of the first cut-out space 393. The second core 390a inserts a plurality of permanent magnet insertion portions 384 and a plurality of fastening members so as to communicate with the permanent magnet insertion portion 384 and the fastening member insertion portion 386 of the first core 380a, respectively. A portion 386 is provided.

The third core 400a has the rotation shaft 340 disposed therein, and a second cut-out space portion cut to have an inner diameter surface 403a extending in a radial direction from an outer surface of the rotation shaft 340 ( 403) and a second inner balance weight 405 formed on the opposite side of the second cut-out space part 403. The third core 400a inserts a plurality of permanent magnet insertion portions 384 and a plurality of fastening members so as to communicate with the permanent magnet insertion portion 384 and the fastening member insertion portion 386 of the first core 380a, respectively. A portion 386 is provided.

Meanwhile, as shown in FIG. 11, the second core 390a includes an overhang section 397 protruding from the end of the stator core 320 along the axial direction. The overhang section 397 of the second core 390a is configured to protrude upward from the upper end of the stator 310.

Accordingly, the efficiency of the electric motor 300a of the present exemplary embodiment may be improved due to a decrease in copper loss due to an increase in the back electromotive force.

The overhang section 397 of the second core 390a is, for example, within 23 to 29% of the height of the rotor core (the height of the rotor core before (or excluding) the overhang section). I can. More specifically, when the height of the rotor core before (excluding) the overhang section 397 is applied is 35 mm, the overhang section 397 of the second core 390a is approximately 8 to 10 mm. Can be formed. It may be preferable that the overhang section 397 of the second core 390a is formed of, for example, 9 mm.

Referring to FIG. 11, the third core 400a includes an overhang section 407 formed to protrude from the end of the stator core 320 along the axial direction. The overhang section 407 of the third core 400a is configured to protrude downward from the lower end of the stator 310.

Accordingly, the efficiency of the electric motor 300a of the present embodiment may be further improved due to a decrease in copper loss due to an increase in the back electromotive force.

The overhang section 407 of the third core 400a is, for example, within 14 to 26% of the height of the rotor core (the height of the rotor core before (or excluding) the overhang section). I can. More specifically, for example, when the height of the rotor core (the height of the rotor core before (or excluding the overhang section) is 35 mm), the overhang section 407 of the second core 390a is approximately 5 to The overhang section 407 of the third core 400a may be formed of, for example, 7 mm.

Here, in the first core 380a of the present embodiment, the second core 390a and the third core 400a are in contact with the rotation shaft 340 in consideration of the configuration including the overhang sections 397 and 407, respectively. The area (stacking height, stacking length) is increased.

More specifically, for example, the stacking height (stacking length) of the first core 380a is when the second core 390a and the third core 400a do not include the overhang sections 397 and 407 For example, in the case of 10 mm, when the overhang section 397 of the second core 390a is 9 mm and the overhang section 407 of the third core 400a is 7 mm, 45% (10 *(35+9+7)/35=4.5mm) can be increased to 14.5mm.

FIG. 12 is a view for explaining the coupling state of the rotation shaft 340 of the rotor of FIG. 10, and FIG. 13 is a view for explaining the unbalance force of the electric motor 300a of FIG. 10. 12, a second core 390a having the overhang section 397 is disposed at the upper end of the first core 380a along the axial direction, and at the lower end of the first core 380a. A third core 400a having the overhang section 407 is disposed. At this time, the first core 380a, the second core 390a, and the third core 400a are disposed so that the plurality of permanent magnet insertion portions 384 and the fastening member insertion portions 386 communicate with each other. . Permanent magnets 410 are respectively coupled to the inside of the plurality of permanent magnet insertion portions 384 of the rotor core 370a, and end plates 420 are respectively coupled to both ends of the rotor core 370a. The lower region of the rotary shaft 340 is coupled to the rotary shaft hole 381 of the rotor core 370a, and one end is connected to the piston 220 in the eccentric portion 350 of the upper portion of the rotary shaft 340 The other end of the connecting rod 230 is coupled.

With this configuration, when operation is started and power is applied to the stator 310, the rotor 360a is rotated around the rotation shaft 340.

When the rotation shaft 340 is rotated, a first unbalance force is generated in the first direction by the piston 220 and the crank pin 352, and a second unbalance force is generated in the second direction opposite by the counter weight 353. An imbalance is generated. A third unbalance force is generated in the second direction by the second core 390a including the overhang section 397, and the first direction by the third core 400a including the overhang section 407 The fourth unbalance force of is generated.

A third core comprising a second core 390a constituting the first inner balance weight 395 and the overhang section 397 and the second inner balance weight 405 and the overhang section 407 of the present embodiment ( By 400a), the unbalanced force shown by the second curve C2 of an elliptical shape in which the width in the x-axis direction perpendicular to the y-axis is relatively narrow is obtained.

When the electric motor 300a of the present embodiment rotates, the second core 390a and the third core 400a each provided with the overhang sections 397 and 407 have a relatively large diameter as shown in FIG. 13. A relatively increased balancing effect can be confirmed from the third curve C3 of the circular shape of. Accordingly, generation of vibration and noise may be more effectively suppressed when the rotor 360a rotates.

In addition, in the compressor of this embodiment, since the rotor 360a includes a second core 390a and a third core 400a each having the overhang sections 397 and 407, the inertia of the rotor 360a is As a result, the efficiency fluctuation is suppressed when the load fluctuation of the compressor of this embodiment is increased, thereby providing a more advantageous compressor in terms of performance.

In this embodiment, a case where the second core 390a is provided at the upper end of the first core 380a and the third core 400a is provided at the lower end of the first core 380a will be described as an example. However, the rotor core is provided with a second core 390a on an upper end of the first core 380a, and is configured to adjust the height of the first core 380a and the height of the second core 390a. May be.

14 is a cross-sectional view of a compressor equipped with an electric motor according to another embodiment of the present invention, and FIG. 15 is an enlarged view of essential parts of the electric motor of FIG. 14. As shown in Fig. 14, the compressor of this embodiment includes a case 110, a compression unit 200, and an electric motor 300b. The compressor includes a cylinder 210, a piston 220, and a connecting rod 230.

The electric motor 300b of the present embodiment includes a stator 310 and a rotor 360b that is rotatably disposed with respect to the stator 310.

The rotor 360b may include a rotation shaft 340; A rotor core 370 having a first core 380, a second core 390 and a third core 400; A permanent magnet 410 coupled to the rotor core 370; And an outer balance weight 430 coupled to the rotor core 370.

The first core 380, the second core 390, and the third core 400 are coupled to be in contact with each other along the axial direction. More specifically, the first core 380 is disposed between the second core 390 and the third core 400. The second core 390 is disposed at the upper end of the first core 380 and the third core 400 is disposed at the lower end of the first core 380.

The first core 380 has a rotation shaft hole 381 penetrating in the axial direction so that the rotation shaft 340 can be inserted.

The second core 390 has a first cut-out space portion 393 having the rotation shaft 340 disposed therein, and having an inner diameter surface 393a extending radially from the outer surface of the rotation shaft 340 ) And a first inner balance weight 395 formed to generate a mass difference on the opposite side of the first cut-out space 393.

The third core 400 includes a second cut-out space portion 403 having the rotation shaft 340 disposed therein, and having an inner diameter surface extending from an outer surface of the rotation shaft 340 in a radial direction, and A second inner balance weight 405 is provided on the opposite side of the second cut-out space part 403 to generate a mass difference.

The first core 380, the second core 390, and the third core 400 each include a plurality of permanent magnet insertion portions 384 penetrating in the axial direction so as to communicate with each other. The first core 380, the second core 390, and the third core 400 are each provided with a plurality of fastening member insertion portions 386 penetrated in the axial direction so as to communicate with each other. Here, the second core 390 and the third core 400 are formed to be rotationally symmetric with respect to the rotation shaft 340. The second core 390 and the third core 400 may be manufactured by the same mold.

On the other hand, as shown in Figure 15, the electric motor (300b) of this embodiment, a rotor having a stator 310 and an outer balance weight 430 coupled to protrude in the axial direction to the end of the rotor core 370 It is comprised with (360b).

The outer balance weight 430 is provided, for example, at an end of the second core 390.

The outer balance weight 430 is configured to generate an unbalance force cooperatively with the first inner balance weight 395.

The outer balance weight 430 is disposed to correspond to the first inner balance weight 395 of the second core 390.

The outer balance weight 430 may be formed of, for example, a non-magnetic material. The outer balance weight 430 is formed of, for example, an aluminum member.

In this embodiment, the upper end of the second core 390 is configured to have substantially the same height as the upper end of the stator 310.

The outer balance weight 430 is disposed to protrude in the axial direction from the upper end of the stator core 320.

16 is a perspective view showing a state of use of the outer balance weight 430 of the electric motor 300b of FIG. 14, FIG. 17 is a perspective view of the outer balance weight 430 of FIG. 16, and FIG. 18 is an outer balance of FIG. It is a plan view of the weight 430. 16 and 17, the outer balance weight 430 includes a semicircular body 432. The outer balance weight 430 includes an inner diameter surface 434 and an outer diameter surface 435 in an arc shape.

The outer diameter surface 435 of the outer balance weight 430 is configured to have the same outer diameter as the outer diameter of the rotor core 370. The inner diameter surface 434 of the outer balance weight 430 has the same diameter (inner diameter) as the inner diameter surface 434 of the first cut-out space portion 393. In this embodiment, since the outer balance weight 430 is configured to generate an unbalance force cooperatively with the first inner balance weight 395, the conventional balance coupled to the upper or lower end of the rotor core 370 It is constructed to have a significantly smaller mass compared to the weight.

The outer balance weight 430 may be formed to have a significantly thinner thickness compared to the conventional balance weight. Accordingly, the length of the rotor 360b in the axial direction can be remarkably shortened. In addition, since the outer balance weight 430 of the present embodiment has a significantly reduced thickness compared to the conventional balance weight, material cost can be significantly reduced.

The outer balance weight 430 is configured to have a thickness of 2.8 to 8.6% of the sum of the axial lengths of the first core 380, the second core 390, and the third core 400.

More specifically, the outer diameter of the outer balance weight 430 is, for example, 50 mm, and the inner diameter of the outer balance weight 430 is, for example, 28 mm, and the outer balance weight 430 The width may be formed to 11 mm. The thickness of the outer balance weight 430 may be, for example, 2 mm. In this embodiment, a case in which the outer balance weight 430 is formed to a thickness of 2 mm is illustrated, but this is only an example, and the outer balance weight 430 is formed to have a thickness of, for example, 1 to 3 mm. Can be.

The outer balance weight 430 is coupled to the ends of the second core 390 so that both ends thereof are respectively disposed on extension lines of both ends of the first inner balance weight 395. A plurality of fastening member insertion portions 437 are formed in the outer balance weight 430 to correspond to the second core 390. Here, the outer balance weight 430 is formed with three fastening member insertion portions 437 to communicate with the fastening member insertion portion 386 of the semicircular second core 390. The inner diameter of the fastening member insertion portion 437 may be, for example, 4 mm.

As shown in FIG. 18, the fastening member insertion portions 437 of the outer balance weight 430 have a shape opened to the inner side of the rotor core 370, respectively. The fastening member insertion part 437 is configured to have an inner diameter R having a size into which the fastening member 425 can be inserted. The fastening member insertion portion 437 is configured to have a spacing distance D whose center O1 is smaller than a radius from the inner diameter surface 434 of the outer balance weight 430. According to this configuration, the width of the opening portion 438 of the fastening member insertion portion 437 is smaller than the outer diameter of the fastening member 425. More specifically, the fastening member insertion portion 437 may be configured such that the center O1 is provided with a separation distance D of, for example, 1mm from the inner diameter surface 434 of the outer balance weight 430. have. Thereby, when the outer balance weight 430 is coupled with the fastening member 425, the sidewall of the fastening member insertion part 437 comes into contact with the fastening member 425 in the transverse direction of the outer balance weight 430. The play can be prevented.

FIG. 19 is a view for explaining the coupling state of the rotation shaft 340 of the rotor of FIG. 14, and FIG. 20 is a view for explaining the unbalance force of the electric motor 300b of FIG. 14. 19, the second core 390 is disposed at the upper end of the first core 380 along the axial direction, and the third core 400 is disposed at the lower end of the first core 380 Are placed respectively. At this time, the first core 380, the second core 390, and the third core 400 are arranged such that the plurality of permanent magnet insertion portions 384 and the fastening member insertion portions 386 are respectively in communication with each other. . Permanent magnets 410 are respectively coupled to the inside of the plurality of permanent magnet insertion portions 384 of the rotor core 370, and end plates 420 are respectively coupled to both ends of the rotor core 370. The outer balance weight 430 is coupled to an upper end of the second core 390.

The lower region of the rotation shaft 340 is coupled to the rotation shaft hole 381 of the rotor core 370 (first core 380), and the connection to the eccentric portion 350 of the upper portion of the rotation shaft 340 The rod 230 is coupled. The piston 220 is connected to the other end of the connecting rod 230.

With this configuration, when operation is started and power is applied to the stator 310, the rotor 360b is rotated around the rotation shaft 340.

When the rotation shaft 340 is rotated, a first unbalance force is generated in a first direction by the piston 220 and the crank pin 352, and a second unbalance force is generated in a second direction opposite to the counter weight. Occurs.

Meanwhile, a third unbalance force is generated in the second direction by the outer balance weight 430 and the first inner balance weight 395 of the second core 390, 2 A fourth unbalance force is generated in the first direction by the inner balance weight 405. These first unbalanced forces, second unbalanced forces, third unbalanced forces and fourth unbalanced forces cancel each other and decrease.

More specifically, as shown in FIG. 20, the outer balance weight 430 of the present embodiment, the first inner balance weight 395 of the second core 390, and the second inner balance weight of the third core 400 ( By 405), the width in the x-axis direction is further narrowed, so that the unbalanced force shown by the second curve C2 of an elliptical shape almost linear is obtained.

Accordingly, a relatively increased balancing effect can be confirmed from the third curve C3 shown in a circular shape with a relatively large diameter. As a result, vibration and noise generation when the rotor 360b is rotated can be more effectively suppressed.

In addition, in the compressor of this embodiment, the rotor is configured with the first inner balance weight 395, the second inner balance weight 405 and the outer balance weight 430, so that the inertia of the rotor 360b is increased. The efficiency fluctuation is suppressed when the load fluctuates in, thereby providing a more advantageous compressor in terms of performance.

In this embodiment, a case where the second core 390 is provided at the upper end of the first core 380 and the third core 400 is provided at the lower end of the first core 380 will be described as an example. However, the rotor core 370 is provided with a second core 390 on the upper end of the first core 380, and the height of the first core 380 and the height of the second core 390 are adjusted. It can also be configured.

In the above, it has been shown and described with respect to specific embodiments of the present invention. However, since the present invention may be implemented in various forms within a range not departing from its spirit or essential features, the embodiments described above should not be limited by the content of the detailed description.

In addition, even if the embodiments are not listed in detail in the above-described detailed description, they should be broadly interpreted within the scope of the technical idea defined in the appended claims. In addition, all changes and modifications included within the technical scope of the claims and their equivalents should be covered by the appended claims.

110: case
115: suction pipe
120: frame
125: bearing
130: support
200: compression unit
210: cylinder
220: piston
230: connecting rod
300: electric motor
310: stator
320: stator core
330: stator coil
340: axis of rotation
350: eccentric
360: rotor
370: rotor core
380: primary core
381: rotary shaft ball
384: Permanent magnet insertion part
386: fastening member insertion part
390: second core
393: first cut-out space
395: 1st inner balance weight
400: third core
403: second cut-out space
405: second inner balance weight
410: permanent magnet
420: end plate

Claims (20)

Stator; And
Including; a rotor disposed rotatably with respect to the stator,
The rotor, a rotating shaft; And
It has a; rotor core coupled to the rotation shaft,
The rotor core,
A first core having a rotation shaft hole into which the rotation shaft is inserted; And
A first cut-out space portion provided on one side of the first core along the axial direction, the rotation shaft disposed therein, and cut to have an inner diameter surface extending in a radial direction from an outer surface of the rotation shaft, and the first An electric motor having a; a second core having a first inner balance weight formed on the opposite side of the cut-out space portion. The method of claim 1,
The rotation shaft is disposed therein, and a second cut-out space portion cut to have an inner diameter surface extending in a radial direction from an outer surface of the rotation shaft, and a second inner balance weight formed on the opposite side of the second cut-out space part. An electric motor further comprising a third core. The method of claim 2,
The first and second cutout spaces, and the first inner balance weight and the second inner balance weight are each formed in rotational symmetry. The method of claim 2,
The second core and the third core are electric motors respectively coupled to both ends of the first core so that the first and second inner balance weights face each other around the rotation axis. The method of claim 4,
The stator includes a stator core and a stator coil wound around the stator core,
The second core is an electric motor including an overhang section protruding from the stator core in an axial direction. The method of claim 5,
The overhang section of the second core is formed to a height of 23 to 29% of the sum of the heights of the first core, the second core, and the third core before the overhang section is applied. The method of claim 6,
The third core is an electric motor including an overhang section protruding from the stator core in an axial direction. The method of claim 7,
The height of the overhang section of the third core is formed to be 14 to 26% of the height of the rotor core before application of the overhang section of the second core and the third core. The method of claim 2,
The rotating shaft has an eccentric portion, and the second core is an electric motor in which the first inner balance weight is disposed on an opposite side of the eccentric portion. The method of claim 9,
The eccentric portion includes a crank arm protruding along a radial direction of the rotation shaft and spaced apart in an axial direction, a crank pin connecting the crank arm, and a counter weight disposed on an opposite side of the crank arm,
The second core is an electric motor coupled such that a first inner balance weight is disposed on an opposite side of the crank pin. The method of claim 10,
The third core is an electric motor coupled such that a second inner balance weight is disposed on the crank pin side. The method of claim 2,
An electric motor further comprising an outer balance weight protrudingly coupled to an end portion of the rotor core in an axial direction. The method of claim 12,
The outer balance weight is an electric motor provided at an end of the second core. The method of claim 13,
The outer balance weight is an electric motor that generates an unbalance force cooperatively with the first inner balance weight. The method of claim 12,
The outer balance weight is an electric motor formed of a non-magnetic material. The method of claim 12,
The outer balance weight is an electric motor formed of an aluminum (Al) member. The method of claim 12,
The outer balance weight is formed by having an outer diameter surface corresponding to the outer diameter of the second core and an inner diameter surface corresponding to the inner diameter surface of the first cut-out space part. The method of claim 12,
The outer balance weight is an electric motor having a thickness of 2.8 to 8.6% of the sum of the axial lengths of the first core, the second core, and the third core. case;
A compression unit provided inside the case; And
Compressor comprising; the electric motor of any one of claims 1 to 18 provided inside the case to provide a driving force to the compression unit. The method of claim 19,
The compression unit,
cylinder;
A piston reciprocally disposed inside the cylinder; And
Compressor comprising a; one end is connected to the piston and the other end is a connecting rod connected to the rotating shaft of the electric motor.

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