JP2013165611A - Permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet motor capable of effectively suppressing torque ripples.SOLUTION: A permanent magnet motor 1 comprises: a permanent magnet 23 buried in a rotor 20 so as to be close to an outer peripheral surface of the rotor 20 at two end parts corresponding to respective sides of a square whose center is a shaft center of the rotor 20; and a plurality of slits 26 arranged between the outer peripheral surface of the rotor 20 and the permanent magnet 23, and whose cross sectional shape making a right angle with a rotor shaft line direction is longitudinal shape extending from the permanent magnet side toward the rotor outer peripheral surface side, and arranged along the permanent magnet 23 at an interval. With respect to a plurality of slits 26a and 26b in the vicinity of the end part, including one arranged so as to correspond to the end part of the permanent magnet 23, straight lines La and Lb connecting between longitudinal-direction substantial both ends of the respective cross sections are substantially parallel to each other, and a shape of the cross section of the slit 26b is in a substantial circular arc shape curved to the straight line Lb connecting the longitudinal-direction substantial both ends.

Description

  The present invention relates to a permanent magnet motor having a rotor in which permanent magnets are embedded.

  A conventional rotor of a permanent magnet motor is disclosed in Patent Document 1. The rotor of this conventional permanent magnet motor is a rotor with a permanent magnet embedded in an iron core (rotor core). A motor having a rotor with this configuration can use both the magnet torque generated by the attraction and repulsion of the permanent magnet and the reluctance torque generated by the coil attracting the rotor iron core, so that high efficiency can be achieved. . Nowadays, such a permanent magnet motor has a wide range of application to home appliances such as an air conditioner, a washing machine, and a refrigerator.

  On the other hand, there is a concern that a motor having a rotor in which a permanent magnet is embedded may have a large torque ripple that is a torque fluctuation generated when the rotor rotates. When the torque ripple at the time of rotor rotation becomes large, there has been a problem that the vibration and noise of the permanent magnet motor and the device equipped with the motor become large.

  In order to solve this problem, the rotor of the permanent magnet motor described in Patent Document 1 includes a plurality of slits on the radially outer side of the permanent magnet insertion port (permanent magnet punching hole). The plurality of slits are arranged at substantially equal intervals along the adjacent permanent magnets, and are formed such that the intervals between the permanent magnets and the rotor outer peripheral surface are all the same. As a result, this conventional rotor tries to provide a motor with reduced vibration and noise by reducing the torque ripple generated when the rotor rotates.

JP-A-11-187597

  However, since the rotor of the conventional permanent magnet motor is formed so that the intervals between the plurality of slits and the outer peripheral surface of the rotor are all the same, the end of the permanent magnet close to the outer peripheral surface of the rotor is formed. No suitable consideration has been made to suppress torque ripple with respect to magnetic flux generated near the portion. As a result, there is a problem in that torque ripple generated during rotor rotation may not be sufficiently suppressed.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a permanent magnet motor capable of effectively suppressing torque ripple generated when the rotor rotates.

  In order to solve the above-described problems, the permanent magnet motor of the present invention is a portion corresponding to each side of a substantially polygon centered on the axis of the rotor and close to the outer peripheral surface of the rotor at two end portions. The permanent magnet embedded in the rotor along the rotor axial direction and the cross-sectional shape perpendicular to the rotor axial direction disposed between the outer peripheral surface of the rotor and the permanent magnet are permanent. A slit extending in a longitudinal direction extending from the magnet side toward the rotor outer peripheral surface side and extending along the rotor axial direction, and a plurality of slits arranged at intervals along the permanent magnet. With respect to the plurality of slits in the vicinity of the end portion including those arranged corresponding to the end portion, a straight line connecting substantially both ends in the longitudinal direction of each cross-section is substantially parallel and at least one of each Previous Shape of the cross section is characterized by being curved with respect to the straight line connecting the substantially longitudinal ends.

  According to this configuration, there is a difference in the shape and interval of the rotor cross section between each slit and the rotor outer peripheral surface with respect to the plurality of slits near the end of the permanent magnet. Thereby, the amount of magnetic flux generated near the end of the permanent magnet close to the rotor outer peripheral surface is adjusted. Therefore, this permanent magnet motor has a small fluctuation range of torque generated when the rotor rotates.

  Note that the “longitudinal direction” described here refers to a long side of a rectangular or belt-like shape in a so-called “longitudinal” shape such as a rectangular or belt-like shape, an oval shape (oval or oval), an arc shape, or the like. Direction, major axis direction of oval shape, and circumferential direction of arc shape.

  Further, in the permanent magnet motor having the above-described configuration, regarding the plurality of slits in the vicinity of the end portion including those arranged corresponding to the end portion of the permanent magnet, the cross-section of the slit corresponding to the end portion The shape has a side parallel to the straight line connecting substantially both ends in the longitudinal direction, and the shape of the cross section of the slit inside the slit arrangement direction from the slit corresponding to the end portion connects substantially both ends in the longitudinal direction. The shape is curved with respect to the straight line.

  According to this configuration, the shape of the cross section of the slit arranged corresponding to the end of the permanent magnet is different from the shape of the cross section of the slit inside the slit arrangement direction. Thereby, a difference arises in the shape and space | interval of a rotor cross section between each of these slits and a rotor outer peripheral surface. Therefore, the amount of magnetic flux generated near the end of the permanent magnet close to the rotor outer peripheral surface is adjusted.

  Further, in the permanent magnet motor having the above-described configuration, regarding the plurality of slits in the vicinity of the end portion including those arranged corresponding to the end portion of the permanent magnet, the cross-section of the slit corresponding to the end portion The shape is curved with respect to the straight line connecting substantially both ends in the longitudinal direction, and the shape of the cross section of the slit inside the slit arrangement direction from the slit corresponding to the end is the straight line connecting substantially both ends in the longitudinal direction. It is characterized by having a shape having parallel sides.

  According to this configuration, the shape of the cross section of the slit arranged corresponding to the end of the permanent magnet is different from the shape of the cross section of the slit inside the slit arrangement direction. Thereby, a difference arises in the shape and space | interval of a rotor cross section between each of these slits and a rotor outer peripheral surface. Therefore, the amount of magnetic flux generated near the end of the permanent magnet close to the rotor outer peripheral surface is adjusted.

  According to the configuration of the present invention, the amount of magnetic flux generated in the vicinity of the end portion of the permanent magnet close to the outer peripheral surface of the rotor is adjusted in the permanent magnet motor, and the fluctuation range of torque generated when the rotor rotates can be reduced. Therefore, it is possible to provide a permanent magnet motor capable of effectively suppressing torque ripple generated when the rotor rotates.

1 is a cross-sectional view of a permanent magnet motor according to a first embodiment of the present invention. It is sectional drawing of the rotor of the permanent magnet motor which concerns on the 1st Embodiment of this invention. It is the elements on larger scale of the location of the permanent magnet and slit of the rotor cross section of the permanent magnet motor which concern on the 1st Embodiment of this invention. It is a graph which shows the relationship between the rotor rotation angle and torque of the permanent magnet motor which concerns on the 1st Embodiment of this invention. It is sectional drawing of the rotor of the permanent magnet motor of a comparative example. It is the elements on larger scale of the location of the permanent magnet and slit of the rotor cross section of the permanent magnet motor of a comparative example. It is a graph which shows the relationship between the rotor rotation angle and torque of the permanent magnet motor of a comparative example. It is the elements on larger scale of the location of the permanent magnet and slit of the rotor cross section of the permanent magnet motor which concern on the 2nd Embodiment of this invention. It is the elements on larger scale of the location of the permanent magnet and slit of the rotor cross section of the permanent magnet motor which concern on the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, the outline of the structure of the permanent magnet motor according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a permanent magnet motor.

  As shown in FIG. 1, the permanent magnet motor 1 includes a stator 10 that is a stator and a rotor 20 that is a rotor.

  The stator 10 includes a stator core 11 made of an annular magnetic material. The stator core 11 includes an annular stator yoke 12 and a stator tooth 13 extending so as to protrude radially inward from an inner peripheral portion of the stator yoke 12. The radially inner tip of the stator teeth 13 faces the outer peripheral surface of the rotor 20 with a gap therebetween.

  For example, six stator teeth 13 are arranged side by side in the circumferential direction of the permanent magnet motor 1. That is, six slots 14 are formed in the stator 10. The stator teeth 13 are integrally formed, for example, by laminating a plurality of steel plates in the motor axis direction (direction perpendicular to the paper surface of FIG. 1).

  An insulator (not shown) constituting a bobbin made of an electrically insulating material is mounted on the outer periphery of the stator teeth 13. Further, a coil 15 around which an electric wire is wound along the motor axial direction is formed outside the insulator and at the slot 14. A current for rotating the rotor 20 is passed through the coil 15.

  The rotor 20 is made of a magnetic material having a substantially cylindrical shape, and is a rotor that is rotatably arranged inside the stator 10 as shown in FIG. The rotor 20 includes a rotating shaft 21 and a rotor core 22 fixed so as not to be displaceable with respect to the peripheral surface of the rotating shaft 21.

  For example, both ends of the rotary shaft 21 are rotatably supported by a motor case (not shown) or the like via two bearings (not shown). In another example, one end of the rotating shaft 21 is supported in a cantilever manner using a bearing or the like. The rotor axial direction is the same as the motor axial direction and extends in a direction perpendicular to the paper surface of FIG. A permanent magnet 23 is embedded in the rotor core 22.

  Next, the configuration of the rotor 20 will be described in more detail with reference to FIGS. 2 to 4 in addition to FIG. 2 is a cross-sectional view of the rotor 20 of the permanent magnet motor 1, FIG. 3 is a partially enlarged view of the permanent magnet 23 and slits in the cross section of the rotor 20, and FIG. 4 is a relationship between the rotor rotation angle and torque of the permanent magnet motor 1. It is a graph which shows.

  As shown in FIG. 2, the rotor core 22 of the rotor 20 is configured such that two magnetic poles of N pole and S pole are alternately arranged along the circumferential direction. The number of magnetic poles of the rotor core 22 is four. Each of the magnetic poles of the rotor core 22 is provided with a permanent magnet insertion slot 24, and a permanent magnet 23 is embedded in the permanent magnet insertion slot 24.

  The permanent magnet 23 has a rectangular cross-sectional shape perpendicular to the rotor axial direction, and corresponds to each side of a quadrangle centered on the axis of the rotor 20, and the outer peripheral surface of the rotor 20 at two ends. It is arranged to be close to. The permanent magnet insertion opening 24 has, for example, a trapezoidal cross section that is perpendicular to the rotor axial direction in which the permanent magnet 23 can be inserted, and is open along the rotor axial direction. The permanent magnet 23 extends along the rotor axial direction in accordance with the permanent magnet insertion opening 24 and is inserted and embedded in the permanent magnet insertion opening 24. FIG. 2 shows a cross section of the permanent magnet 23 and the permanent magnet insertion opening 24 described here.

  The permanent magnet 23 is in contact with the inner surface of the permanent magnet insertion port 24 between both longitudinal ends of the cross section. In the permanent magnet insertion opening 24, a gap portion 25 is provided adjacent to the outer ends of the longitudinal direction of the cross section of the permanent magnet 23 and close to the outer peripheral surface of the rotor 20. The gap 25 has a triangular cross section, for example, and is open along the rotor axial direction.

  A slit 26 is provided between the outer peripheral surface of the rotor 20 and the permanent magnet 23. A plurality of slits 26 are arranged at intervals along the adjacent permanent magnets 23. That is, six slits 26 are provided for each adjacent permanent magnet 23.

  As shown in FIG. 3, the slit 26 has a cross-sectional shape perpendicular to the rotor axial direction extending from the permanent magnet side toward the rotor outer peripheral surface side, that is, an elliptical shape or a substantially arc shape. Open along. In addition, among the six slits 26 adjacent to one permanent magnet 23, two slits 26a in the vicinity of the end portion including the slits 26a arranged corresponding to the two end portions of the permanent magnet 23, As for 26b, the straight lines La and Lb which connect the both ends of the longitudinal direction of each cross section are substantially parallel. In addition, the dashed-dotted line of FIG. 3 has shown the straight lines La and Lb which connect the both ends of the longitudinal direction of the cross section of the two slits 26a and 26b.

  At least one of the slits 26a and 26b, that is, the shape of the cross section of the slit 26b is curved with respect to a straight line Lb (dashed line) connecting substantially both ends in the longitudinal direction to form a substantially arc shape. The slit 26a has an oval shape in which the cross-sectional shape has sides parallel to a straight line La (dashed line) connecting substantially both ends in the longitudinal direction.

  FIG. 4 is a graph showing the relationship between the rotor rotation angle and the torque when the permanent magnet motor 1 having the configuration of the embodiment is rotated. The horizontal axis of the graph indicates the rotation angle of the rotor 20 from 0 degrees to 90 degrees, and the vertical axis of the graph indicates the torque generated corresponding to the rotation angle of the rotor 20. According to this, it can be seen that the torque fluctuates within a fluctuation range Tr1 between the minimum value and the maximum value every 30 degrees as the rotor rotation angle.

  Here, the permanent magnet motor which is a comparative example with respect to the permanent magnet motor 1 as the said embodiment is demonstrated using FIGS. FIG. 5 is a cross-sectional view of a rotor of a comparative permanent magnet motor, FIG. 6 is a partially enlarged view of a permanent magnet and a slit in the cross section of the rotor of the comparative permanent magnet motor, and FIG. 7 is a rotor of the permanent magnet motor of the comparative example. It is a graph which shows the relationship between a rotation angle and a torque. In addition, since the basic structure of this comparative example is the same as the said embodiment demonstrated using FIGS. 1-4, description shall be abbreviate | omitted about the component which is common in the said embodiment.

  The rotor 120 of the permanent magnet motor of the comparative example includes a rotating shaft 121 and a rotor core 122 as shown in FIG. Each of the magnetic poles of the rotor core 122 is provided with a permanent magnet insertion slot 124, and the permanent magnet 123 is embedded in the permanent magnet insertion slot 124.

  A slit 126 is provided between the outer peripheral surface of the rotor 120 and the permanent magnet 123. Six slits 126 are provided for each of the adjacent permanent magnets 23, and the slits 126 are arranged at intervals along the permanent magnet 123. All the slits 126 have an oval shape in which a cross-sectional shape perpendicular to the rotor axial direction extends from the permanent magnet side toward the rotor outer peripheral surface side.

  FIG. 7 is a graph showing the relationship between the rotor rotation angle and the torque when the permanent magnet motor having the configuration of the comparative example is rotated. According to this, it can be seen that the torque fluctuates within a fluctuation range Tr0 between the minimum value and the maximum value every 30 degrees as the rotor rotation angle.

  And the torque fluctuation range Tr1 when rotating the permanent magnet motor 1 of the said embodiment shown in FIG. 4, and the torque fluctuation range Tr0 when rotating the permanent magnet motor of the comparative example shown in FIG. In comparison, the torque fluctuation width Tr1 generated in the permanent magnet motor 1 of the embodiment is about 88% of the torque fluctuation width Tr0 generated in the permanent magnet motor of the comparative example, which is small.

  In this way, the permanent magnet motor 1 has substantially two ends in the longitudinal direction of each cross section with respect to the two slits 26a and 26b in the vicinity of the end including the slit 26a arranged corresponding to the end of the permanent magnet 23. The connecting straight lines La and Lb are substantially parallel, and the cross-sectional shape of the slit 26b is curved with respect to the straight line Lb connecting substantially both ends in the longitudinal direction to form a substantially arc shape. Thereby, a difference arises in the shape and space | interval of the rotor cross section between slit 26a, 26b of the edge part vicinity of the permanent magnet 23, and a rotor outer peripheral surface. Then, the amount of magnetic flux generated near the end of the permanent magnet 23 close to the rotor outer peripheral surface is adjusted. Therefore, the permanent magnet motor 1 can reduce the fluctuation range of the torque generated when the rotor rotates.

  Further, the shape of the cross section of the slit 26a arranged corresponding to each of the two end portions of the permanent magnet 23 is an oval shape having sides parallel to the straight line La connecting substantially both ends in the longitudinal direction, and the slit 26a. Further, the shape of the cross section of the slit 26b on the inner side in the slit arrangement direction is a substantially arc shape curved with respect to a straight line Lb connecting substantially both ends in the longitudinal direction. Thereby, the shape of the cross section of the slit 26a arranged corresponding to the end of the permanent magnet 23 is different from the shape of the cross section of the slit 26b on the inner side in the slit arrangement direction. And a difference can be made in the shape and space | interval of the rotor cross section between these slits 26a and 26b and a rotor outer peripheral surface. Therefore, the permanent magnet motor 1 can adjust the amount of magnetic flux generated in the vicinity of the end portion of the permanent magnet 23 close to the outer peripheral surface of the rotor.

  According to the configuration of the above-described embodiment of the present invention, the amount of magnetic flux generated in the vicinity of the end of the permanent magnet 23 close to the outer peripheral surface of the permanent magnet motor 1 is adjusted, and the fluctuation range of torque generated when the rotor rotates is reduced. It becomes possible to do. Therefore, it is possible to provide the permanent magnet motor 1 that can effectively suppress the torque ripple generated when the rotor rotates.

  Next, a permanent magnet motor according to a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a partially enlarged view of a permanent magnet and a slit in the rotor cross section of the permanent magnet motor. Since the basic configuration of this embodiment is the same as that of the first embodiment described with reference to FIGS. 1 to 7, the same reference numerals are used for the same components as those of the first embodiment. The description of the drawings and the description thereof will be omitted.

  The permanent magnet motor according to the second embodiment includes a slit 27 between the outer peripheral surface of the rotor 20 and the permanent magnet 23 as shown in FIG. Eight slits 27 are provided for each adjacent permanent magnet 23.

  Of the eight slits 27, the three slits 27a, 27b, 27c in the vicinity of the ends including the slits 27a arranged corresponding to the two end portions of the permanent magnet 23 are the longitudinal directions of the respective cross sections. Straight lines La, Lb, and Lc connecting substantially both ends are substantially parallel. In addition, the dashed-dotted line of FIG. 8 has shown the straight lines La, Lb, and Lc which connect the both ends of the longitudinal direction of the cross section of the three slits 27a, 27b, and 27c.

  Of each of the slits 27a, 27b, 27c, the cross-sectional shape of the slits 27b, 27c is curved with respect to the straight lines Lb, Lc (dashed lines) connecting substantially both ends in the longitudinal direction to form a substantially arc shape. The slit 27a has an oval shape in which the cross-sectional shape has sides parallel to a straight line La (dashed line) connecting substantially both ends in the longitudinal direction.

  As in the configuration of the second embodiment, the cross-sectional shape of the slit 27a arranged corresponding to each of the two end portions of the permanent magnet 23 is a side parallel to the straight line La connecting substantially both ends in the longitudinal direction. Even when the cross-sectional shape of the slits 27b and 27c on the inner side in the slit arrangement direction from the slit 27a is a substantially arc shape curved with respect to the straight lines Lb and Lc that connect substantially both ends in the longitudinal direction, The amount of magnetic flux generated near the end of the permanent magnet 23 close to the surface is adjusted. Therefore, the permanent magnet motor 1 can reduce the fluctuation range of the torque generated when the rotor rotates.

  Next, a permanent magnet motor according to a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a partially enlarged view of a permanent magnet and a slit in the rotor cross section of the permanent magnet motor. Since the basic configuration of this embodiment is the same as that of the first embodiment described with reference to FIGS. 1 to 7, the same reference numerals are used for the same components as those of the first embodiment. The description of the drawings and the description thereof will be omitted.

  The permanent magnet motor according to the third embodiment includes a slit 28 between the outer peripheral surface of the rotor 20 and the permanent magnet 23 as shown in FIG. Six slits 28 are provided for each of the adjacent permanent magnets 23.

  Of the six slits 28, the two slits 28a and 28b in the vicinity of the ends including the slits 28a arranged corresponding to the two end portions of the permanent magnet 23 are substantially both ends in the longitudinal direction of each cross section. Lines La and Lb connecting the two are substantially parallel. In addition, the dashed-dotted line of FIG. 9 has shown the straight lines La and Lb which connect the longitudinal direction substantially both ends of the cross section of the two slits 28a and 28b.

  Of each of the slits 28a and 28b, the sectional shape of the slit 28a is curved with respect to a straight line La (dashed line) connecting substantially both ends in the longitudinal direction to form a substantially arc shape. The slit 28b has an oval shape in which the cross-sectional shape has sides parallel to a straight line Lb (dashed line) connecting substantially both ends in the longitudinal direction.

  As in the configuration of the third embodiment, the shape of the cross section of the slit 28a arranged corresponding to each of the two end portions of the permanent magnet 23 is substantially curved with respect to a straight line La connecting substantially both ends in the longitudinal direction. Since it has an arc shape and the shape of the cross section of the slit 28b on the inner side in the slit arrangement direction from the slit 28a is an ellipse having a side parallel to the straight line Lb connecting substantially both ends in the longitudinal direction, The shape of the cross section of the slit 28a arranged correspondingly is different from the shape of the cross section of the slit 28b on the inner side in the slit arrangement direction. Thereby, a difference can be produced in the shape and interval of the rotor cross section between the slits 28a and 28b and the rotor outer peripheral surface. Therefore, the permanent magnet motor 1 can adjust the amount of magnetic flux generated in the vicinity of the end portion of the permanent magnet 23 close to the outer peripheral surface of the rotor.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, the shape and quantity of the permanent magnet 23, the permanent magnet insertion slot 24, and the slit 26 are not limited to the shape and quantity used in the above embodiment, and may be other shapes and quantities.

  Further, regarding the permanent magnets 23 arranged at the positions corresponding to the sides of the polygon centered on the axis of the rotor 20, the polygon is not limited to the quadrangle of the above-described embodiment. Other polygons such as an octagon may be used.

  Further, in the above embodiment, with respect to two or three slits in the vicinity of the end of the permanent magnet 23, straight lines connecting substantially both ends in the longitudinal direction of each cross-section are substantially parallel, and the shape of at least one cross-section of each is formed. Is curved with respect to a straight line connecting substantially both ends in the longitudinal direction, but four or more slits in the vicinity of the end of the permanent magnet 23 may be targeted. In this case, it is desirable that the number of slits arranged at intervals along the permanent magnet 23 is 10 or more.

  The present invention can be used for a permanent magnet motor having a rotor in which permanent magnets are embedded.

DESCRIPTION OF SYMBOLS 1 Permanent magnet motor 10 Stator 20 Rotor 21 Rotating shaft 22 Rotor core 23 Permanent magnet 24 Permanent magnet insertion port 25 Air gap part 26, 27, 28 Slit

Claims (3)

A portion corresponding to each side of a substantially polygonal shape centered on the axis of the rotor, and disposed at two end portions so as to be close to the outer peripheral surface of the rotor, and embedded in the rotor along the rotor axial direction. Permanent magnets,
The cross-sectional shape that is arranged between the outer peripheral surface of the rotor and the permanent magnet and is perpendicular to the rotor axial direction forms a longitudinal shape that extends from the permanent magnet side toward the rotor outer peripheral surface side along the rotor axial direction. A plurality of slits that are opened and arranged at intervals along the permanent magnet;
With
With respect to the plurality of slits in the vicinity of the end portions including those arranged corresponding to the end portions of the permanent magnets, straight lines connecting substantially both ends in the longitudinal direction of the cross sections are substantially parallel and at least of each of them. One of the cross-sectional shapes is a curved shape with respect to the straight line connecting substantially both ends in the longitudinal direction.   With respect to the plurality of slits in the vicinity of the end including those arranged corresponding to the end of the permanent magnet, the straight line that connects substantially both ends in the longitudinal direction of the slit corresponding to the end The shape of the cross section of the slit inside the slit arrangement direction from the slit corresponding to the end portion is a shape curved with respect to the straight line connecting substantially both ends in the longitudinal direction. The permanent magnet motor according to claim 1.   With respect to the plurality of slits in the vicinity of the end including those arranged corresponding to the end of the permanent magnet, the straight line that connects substantially both ends in the longitudinal direction of the slit corresponding to the end The shape of the cross section of the slit inside the slit arrangement direction from the slit corresponding to the end portion is a shape having sides parallel to the straight line connecting substantially both ends in the longitudinal direction. The permanent magnet motor according to claim 1.

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