WO2015075886A2

WO2015075886A2 - Rotary electric machine rotor

Info

Publication number: WO2015075886A2
Application number: PCT/JP2014/005617
Authority: WO
Inventors: Takeshi Ishida; Yu Hirai
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-11-20
Filing date: 2014-11-07
Publication date: 2015-05-28
Also published as: JP2015100227A; WO2015075886A3

Abstract

A rotor shaft 30 has a stopper portion 32 on a first end side, and has an outside threaded structure 44 on a second end side. A washer 70 is disposed between an end of a rotor core 20 on the second end side and an end of a nut portion 50 on the first end side. A position of a plane in which the washer 70 and the rotor core 20 are in contact with each other is located, in the rotor shaft 30, closer to the first end side in the axial direction than is the outside threaded structure 44 when the rotor core 20 is attached to the rotor shaft 30 by fastening the nut portion 50 to the outside threaded structure 44 of the rotor shaft 30.

Description

ROTARY ELECTRIC MACHINE ROTOR

The present invention relates to a rotary electric machine rotor, and, in particular, relates to a rotary electric machine rotor wherein a rotor core composed of laminated magnetic thin plates is attached to a rotor shaft.

JP 2002-095197 A describes a rotary electric machine rotor, and indicates that a method including press-fitting and attaching a rotor shaft to a rotor core formed by laminating flat rolled magnetic steel sheets may deform the flat rolled magnetic steel sheets. This patent document discloses methods including providing a clearance fit rather than a press-fit, in combination with, for example, (1) bonding with an adhesive, (2) press-fitting a bushing into the clearance, or (3) threading the shaft and pressing the core by a nut.

JP 2001-045724 A describes laminating rotor steel sheets having a hole through which a rotor shaft is inserted, and fastening the laminated steel sheets by a flanged metal core having a threaded portion, and a nut.

JP 2013-106406 A describes a method for fastening a rotor core including laminated flat rolled magnetic steel sheets and end plates disposed on both sides of the laminated flat rolled magnetic steel sheets, without using a threaded structure. The first end plate has a projection on its inner circumference. The rotor shaft has a diameter change against which the second end plate is pressed. The rotor shaft also has a groove for receiving the projection formed on the first end plate. The laminated flat rolled magnetic steel sheets are compressed by pressing the first end plate toward the second end plate, and the projection of the first end plate is fitted into the groove of the rotor shaft. Springback of the laminated flat rolled magnetic steel sheets causes the flat rolled magnetic steel sheets sandwiched between the two end plates to be attached to the rotor shaft.

JP 2002-095197 A JP 2001-045724 A JP 2013-106406 A

In a conventional method including threading a rotor shaft to form a threaded structure and attaching a rotor core to the rotor shaft by a nut, an end of the threaded structure formed in the rotor shaft matches with an end of the rotor core. This may eliminate an overlap between the rotor core and the threaded structure when an inside hole of the rotor core is brought into engagement with the outer shape of the rotor shaft, and therefore may provide a stable fit. Variations in axial thickness of the rotor core form a clearance between the end of the threaded structure and the end of the rotor core. The fastening by the nut is then insufficient, due to the absence of the threaded structure in this clearance. As such, the rotor core cannot be tightly fastened in the axial direction. In particular, when the rotor core is composed of a laminate of magnetic thin plates, clearances in the laminate may result in significant variations in axial thickness of the rotor core, which make it difficult to fasten the rotor core to the rotor shaft by a predetermined fastening force.

An object of the present invention is to provide a rotary electric machine rotor that allows a rotor core to be fastened to a rotor shaft by a predetermined fastening force regardless of variations in axial thickness of the rotor core.

According to one aspect of the present invention, there is provided a rotary electric machine rotor, comprising a rotor core composed of laminated magnetic thin plates, the rotor core having a center hole; a rotor shaft having a stopper portion on a first end side in an axial direction, the stopper portion abutting against a surface of the rotor core on the first end side in the axial direction, the rotor shaft having an outside threaded structure on a second end side in the axial direction, the rotor shaft being inserted through the center hole of the rotor core; a nut portion that is in engagement with the outside threaded structure of the rotor shaft; and a washer disposed between an end of the rotor core on the second end side in the axial direction and an end of the nut portion on the first end side in the axial direction, wherein a position of a plane in which the washer and the rotor core are in contact with each other is located, in the rotor shaft, closer to the first end side in the axial direction than is the outside threaded structure when the rotor core is attached to the rotor shaft by fastening the nut portion to the outside threaded structure of the rotor shaft.

Further, in the rotary electric machine rotor according to the present invention, it is preferred that the nut portion has a thin portion for swaging, the thin portion for swaging extending toward the second end side in the axial direction.
Further, in the rotary electric machine rotor according to the present invention, it is preferred that the thin portion for swaging comprises a plurality of thin portions for swaging that are spaced apart from each other in a circumferential direction.
Further, in the rotary electric machine rotor according to the present invention, it is preferred that the thin portions for swaging are swaged to the outside threaded structure.

Further, in the rotary electric machine rotor according to the present invention, it is preferred that the washer has a thickness that is set based on variations in axial thickness of the rotor core.

Further, in the rotary electric machine rotor according to the present invention, it is preferred that the stopper portion is a diameter change portion of the rotor shaft, the diameter change portion being formed on the first end side in the axial direction.

In a rotary electric machine rotor according to the present invention, a rotor core is abutted against a stopper portion formed on the side closer to one end (first end) of the rotor shaft. The rotor core is attached to the rotor shaft via a washer using a nut portion that is brought into engagement with an outside threaded structure formed on the side closer to another end (second end) of the rotor shaft. In this state, the position of a plane in which the washer and the rotor core are in contact with each other is located, in the rotor shaft, closer to the first end in the axial direction than is the outside threaded structure. For example, when the fastening by the nut in the area of the outside threaded structure of the rotor shaft does not provide a predetermined fastening force due to variations in axial thickness of the rotor core such that the rotor core has a smaller axial thickness, the predetermined fastening force can be obtained because the washer holds the rotor core in place of the nut. As described above, even when the rotor core varies in axial thickness, the washer can hold the rotor core outside the area of the outside threaded structure. Therefore, the rotor core can be fastened to the rotor shaft by the predetermined fastening force regardless of variations in axial thickness of the rotor core.

In a rotary electric machine rotor according to the present invention, because the nut portion is swaged and attached to the outside threaded structure of the rotor shaft using a thin portion for swaging, the rotor core can be fastened to the rotor shaft under the predetermined fastening force without being loosened.

In a rotary electric machine rotor according to the present invention, the thickness of the washer is set based on variations in axial thickness of the rotor core. As such, the washer can absorb variations in axial thickness of the rotor core. Therefore, the rotor core can be fastened to the rotor shaft by the predetermined fastening force regardless of variations in axial thickness of the rotor core.

In a rotary electric machine rotor according to the present invention, because the stopper portion is a diameter change portion formed on the side closer to the first end of the rotor shaft, the rotor core can be fastened to the rotor shaft by the predetermined fastening force, with a simple structure, regardless of variations in axial thickness of the rotor core.

Fig. 1 illustrates a structure of a rotary electric machine rotor according to some embodiments of the present invention. Fig. 2 is a partially enlarged view of Fig. 1. Fig. 3 illustrates a nut portion for use in a rotary electric machine rotor according to some embodiments of the present invention, in which the diagram denoted by (a) is a cross-sectional view; the diagram denoted by (b) is a top view; the diagram denoted by (c) illustrates a thin portion for swaging before it is swaged; and the diagram denoted by (d) illustrates the thin portion for swaging after it is swaged.

Embodiments of the present invention will be described in detail below with reference to the drawings. The following description specifies, for example, sizes, shapes, and materials by way of illustrative example, and modifications are possible as desired in accordance with, for example, requirements of a rotary electric machine rotor. In the following description, similar elements are denoted by the same reference numerals throughout all of the drawings, and descriptions are not repeated.

Fig. 1 illustrates a structure of a rotary electric machine rotor 10 for use in a rotary electric machine that is to be mounted on a vehicle. In the following description, the rotary electric machine rotor 10 is referred to as "rotor 10," unless otherwise specified. Fig. 2 is a partially enlarged view of Fig. 1.

The rotor 10 may be used in a rotary electric machine serving as a motor generator which functions as a motor while the vehicle is powered and running, and which functions as a generator while the vehicle is under braking. The rotary electric machine is a three-phase synchronous rotary electric machine. The rotary electric machine includes the rotor 10 illustrated in Fig. 1, and an annular stator around which a coil is wound. The stator is disposed on the outer perimeter side of the rotor 10 with a certain clearance between the rotor 10 and the stator. The stator is not illustrated in Fig. 1. Fig. 1 also illustrates the axial direction of the rotor 10, and one end of the double-headed arrow is referred to as "first end side" and another end is referred to as "second end side."

The rotor 10 includes a rotor core 20, a rotor shaft 30 on which the rotor core 20 is fitted, and a nut portion 50 that engages with an outside threaded structure 44 formed in the rotor shaft 30. The rotor 10 has a configuration that allows the rotor core 20 to be fastened to the rotor shaft 30 by a predetermined fastening force, even when the rotor core 20 varies in axial thickness.

The rotor core 20 includes a laminate 22 in which a predetermined number of magnetic thin plates are laminated, and a plurality of magnets 24 that are embedded in the laminate 22.

The laminate 22 in which the magnetic thin plates are laminated has a center hole through which the outer shape of the rotor shaft 30 is inserted, and a plurality of magnet holes in which the plurality of magnets 24 are inserted. The magnetic thin plates may be formed using flat rolled magnetic steel sheets. The magnetic thin plates are laminated in the axial direction of the rotor 10. The center hole and the magnet holes in the laminate 22 extend parallel to the axial direction, and pierce the laminate 22.

The rotor core 20 is composed of the laminate 22 in which the magnetic thin plates are laminated. As such, the axial thickness of the rotor core 20 corresponds to the axial thickness of the laminate 22. Because the magnetic thin plates are laminated by integrating a predetermined number of magnetic thin plates that are cut into a predetermined shape by, for example, swaging, a small amount of clearance is present between adjacent magnetic thin plates in the laminate. Variations in thickness among magnetic thin plates, variations in clearance in the laminate formed during lamination, and other factors cause variations in axial thickness of the laminate 22 and the rotor core 20. The manner in which such variations in axial thickness are absorbed when the rotor core 20 is attached to the rotor shaft 30 will be described below.

The magnets 24 are a plurality of permanent magnets disposed in a predetermined arrangement on the outer perimeter side of the rotor core 20. The permanent magnets form magnetic poles of the rotor 10. In cooperation with a rotating magnetic field that is generated by passing a predetermined amount of current through the coil wound around the stator (not shown) of the rotary electric machine, the magnets 24 generate torque to cause the rotor 10 to rotate. The magnets 24 may be neodymium magnets whose main components are neodymium, iron, and boron, samarium-cobalt magnets whose main components are samarium and cobalt, or other rare earth magnets. Also, other magnets such as ferrite magnets may be used.

The rotor shaft 30 has a stopper portion 32 on the first end side, and has an outside threaded structure 44 on the second end side. The stopper portion 32 abuts against a surface of the rotor core 20 on the first end side in the axial direction. The rotor core 20 is fitted on the rotor shaft 30 from the second end side toward the stopper portion 32. When the rotor 10 is used in a rotary electric machine, the rotor shaft 30 is rotatably supported by bearings at both ends in the axial direction, and rotates in cooperation with the stator (not shown). As described above, in a rotary electric machine, the rotor shaft 30 serves as an output shaft for outputting torque. The rotor shaft 30 may be a steel product processed into a predetermined shape.

The stopper portion 32 is a diameter change portion formed on the first end side of the rotor shaft 30. The surface of the diameter change portion on the second end side is perpendicular to the axial direction. The size of the diameter change portion is set to a level at which the stopper area is sufficient for receiving a fastening force when a first end surface of the rotor core 20 abuts against the diameter change portion and the rotor core 20 is fastened by a predetermined fastening force by means of the nut portion 50.

The outside threaded structure 44 is an external screw extending from the second end side toward the first end side in the rotor shaft 30. The outer diameter of the external screw serving as the outside threaded structure 44 is set to be slightly smaller than the diameter of the center hole of the rotor core 20. This difference in size corresponds to an amount of clearance that allows insertion of the rotor shaft 30 through the center hole of the rotor core 20. Figs. 1 and 2 illustrate a position 33 representing an end of the outside threaded structure on the second end side, and a position 34 representing an end of the outside threaded structure on the first end side. The outside threaded structure 44 is formed in an area between the position 33 and the position 34.

The position 34 of the outside threaded structure 44 on the first end side is set to be located at a position 28 at which a second end surface of the rotor core 20 is located when the rotor core 20 whose axial thickness is of a standard value is assembled to the rotor shaft 30 with the surface of the rotor core 20 on the first end side in the axial direction being abutted against the stopper portion 32. In other words, when the rotor core 20 has a standard thickness, the outside threaded structure 44 and the rotor core 20 do not overlap each other. This configuration is employed in order to avoid unstable fit occurring due to a clearance that may be created in the radial direction between the rotor shaft 30 and the rotor core 20 if the outside threaded structure 44 and the rotor core 20 overlap each other, because the outer diameter of the external screw serving as the outside threaded structure 44 is smaller than the diameter of the center hole of the rotor core 20.

The nut portion 50 has an internal thread 54 for engagement with the outside threaded structure 44 of the rotor shaft 30. While the rotor core 20 is fitted on the rotor shaft 30 with the surface of the rotor core 20 on the first end side being abutted against the stopper portion 32 of the rotor shaft 30, the nut portion 50 applies pressure and fastens the rotor core 20 to the rotor shaft 30.

As described above, the outside threaded structure 44 of the rotor shaft 30 is formed in accordance with the standard axial thickness that does not take into consideration variations in axial thickness of the rotor core 20. As such, if the axial thickness of the rotor core 20 varies, a mismatch may occur between the position 34 of the outside threaded structure 44 on the first end side and the position 28 at which the second end surface of the rotor core 20 is located. When the axial thickness of the rotor core 20 is shorter than the standard value, a clearance may be created between the second end surface of the rotor core 20 and the end of the outside threaded structure 44. Then, the fastening achieved using the outside threaded structure 44 and the nut portion 50 is unable to provide a sufficient fastening force for fastening the rotor core 20 to the rotor shaft 30, because such fastening may be performed only in the area in which the outside threaded structure 44 is formed. To address this situation, a washer 70 is used to provide a sufficient fastening force even when the rotor core 20 varies in axial thickness.

The washer 70 is an annular component having a thickness t that is set based on the extent of variations in axial thickness of the rotor core 20 resulting from, for example, an amount of variation created during lamination in the laminate 22 of the rotor core 20 and/or an amount of deformation created during fastening. The outer diameter of the washer 70 is larger than the outer diameter of a flange portion 56 of the nut portion 50. The inner diameter of the washer 70 is slightly larger than the outer diameter of the rotor shaft 30. The washer 70 is fitted on the outer shape of the rotor shaft 30, and is disposed between the end of the rotor core 20 on the second end side and the end of the nut portion 50 on the first end side. The thickness t of the washer 70 is set to be larger than a value that is expected with reference to the extent of variations in axial thickness of the rotor core 20. The washer 70 may be an appropriate material shaped into a predetermined shape. The material may be a metal material. In some embodiments, a plastic material having an appropriate strength and heat resistance may be used.

The nut portion 50 presses the rotor core 20 fitted on the rotor shaft 30 toward the first end side via the washer 70, and fastens the rotor core 20 to the rotor shaft 30.

The pressure is applied in the manner described below. First, the rotor core 20 is fitted on the rotor shaft 30 from the second end side, and then, the washer 70 is slipped on the rotor shaft 30 from the second end side. The internal thread 54 of the nut portion 50 is engaged with the outside threaded structure 44, and is rotated about the axis. By doing so, the surface of the nut portion 50 on the first end side is abutted against the surface of the washer 70 on the second end side, and the surface of the washer 70 on the first end side is abutted against the surface of the rotor core 20 on the second end side. The nut portion 50 is further rotated about the axis to press the rotor core 20 while the rotor core 20 is being abutted against the stopper portion 32 of the rotor shaft 30. The rotation is stopped at a point when the fastening force reaches a predetermined magnitude. Figs. 1 and 2 illustrate a state in which the rotor core 20 is attached to the rotor shaft 30 by fastening the nut portion 50 to the outside threaded structure 44 of the rotor shaft 30 as described above. In this state, the position 28 of a plane in which the washer 70 and the rotor core 20 are in contact with each other is located, in the axial direction of the rotor shaft 30, closer to the first end side in the axial direction than is the position 34 representing an end of the outside threaded structure 44 on the first end side.

After the application of pressure determines the position of the nut portion 50, the nut portion 50 is fastened to the rotor shaft 30 at that position. The fastening is performed by swaging a thin portion for swaging in the nut portion 50 toward the outside threaded structure 44 of the rotor shaft 30. In Figs. 1 and 2, reference numeral 59 denotes the thin portion for swaging that has been swaged.

Fig. 3 illustrates the nut portion 50 in detail. The diagrams denoted by (a) to (c) illustrate a state in which the nut portion 50 has yet to be swaged. The diagram denoted by (a) is a cross-sectional view, the diagram denoted by (b) is a top view, and the diagram denoted by (c) is an enlarged view of the portion B in the diagram denoted by (a). The diagram denoted by (d) is an enlarged view of the portion B in which swaging has been performed. The nut portion 50 has an internal thread 54 on the radially inner side. The nut portion 50 includes a body portion 52 having a hexagonal outer shape, a circular flange portion 56 having the shape of an envelope of the hexagonal shape of the body portion 52, and a thin portion 58 for swaging extending from the body portion 52 toward the second end side in the axial direction. The nut portion 50 may be formed using a metal material having an appropriate strength, and having been processed. The metal material may be, for example, a steel product.

The thin portion 58 for swaging is a projection having a thickness small enough to be swaged. The projection is deformable by swaging, and has a predetermined swage strength. The swage strength should be of a level at which no rupture occurs in the swaged nut portion 50 when a predetermined torque is applied in the loosening direction. To satisfy these conditions, for example, the thickness and the axial length of the thin portion 58 for swaging, the swage width as measured in the circumferential direction, and the number of swage locations are determined based on the strength of the material of the nut portion 50.

The thin portion 58 for swaging may be of, for example, varying size, swage length, and swage count depending on, for example, the shape of threads of the outside threaded structure 44 of the rotor shaft 30 and the required swage strength. For example, the thin portion 58 for swaging may have a thickness of about 1 mm to about 2 mm, and an axial length of about 2 mm to about 5 mm. Referring to the example in the diagram denoted by (b) in Fig. 3, there are two swages in the circumferential direction. The swage width may be about 2 mm to about 5 mm in the circumferential direction.

Referring to the structures in Figs. 1 to 3, the nut portion 50 is engaged with the outside threaded structure 44 of the rotor shaft 30, and the rotor core 20 is abutted and pressed against the stopper portion 32 via the washer 70. The rotor core 20 is fastened and attached to the rotor shaft 30 in this manner. Because the thickness t of the washer 70 is set based on variations in axial thickness of the rotor core 20, the rotor core 20 can be fastened to the rotor shaft 30 by a predetermined fastening force even when the axial thickness of the rotor core 20 varies and is shorter than the standard value.

Further, because the rotor core 20 and the outside threaded structure 44 do not overlap each other, no clearance is formed in the radial direction between the rotor core 20 and the rotor shaft 30. As such, by employing, for example, a shrink fit structure, the force of attachment between the rotor core 20 and the rotor shaft 30 can be further improved.

Further, by disposing the washer 70 between the nut portion 50 and the rotor core 20, the washer 70 can relieve the stress of pressure exerted on the rotor core 20 by the nut portion 50 during fastening.

A plurality of washers 70 having different thicknesses t may be provided. By selecting a washer 70 having an appropriate thickness t in accordance with the extent of variations in axial thickness of the rotor core 20, the rotor core 20 can be fastened to the rotor shaft 30 by a predetermined fastening force through a screw fastening method over a wide range of variations in axial thickness of the rotor core 20.

Although, in the foregoing description, a diameter change portion of the rotor shaft 30 is described as the stopper portion 32 against which the first end surface of the rotor core 20 is abutted, the above-described screw fastening structure including an outside threaded structure portion and a nut portion may also be provided on the first end side of the rotor shaft 30. The first end surface of the rotor core 20 may be abutted against a surface of the nut portion on the second end side.

10 ROTOR (FOR ROTARY ELECTRIC MACHINE)
20 ROTOR CORE
22 LAMINATE
24 MAGNET
28 POSITION (OF SECOND END SURFACE OF ROTOR CORE)
30 ROTOR SHAFT
32 STOPPER PORTION
33 POSITION (OF END OF OUTSIDE THREADED STRUCTURE ON SECOND END SIDE)
34 POSITION (OF END OF OUTSIDE THREADED STRUCTURE ON FIRST END SIDE)
44 OUTSIDE THREADED STRUCTURE
50 NUT PORTION
52 BODY PORTION
54 INTERNAL THREAD
56 FLANGE PORTION
58, 59 THIN PORTION FOR SWAGING
70 WASHER

Claims

A rotary electric machine rotor, comprising:
a rotor core composed of laminated magnetic thin plates, the rotor core having a center hole;
a rotor shaft having a stopper portion on a first end side in an axial direction, the stopper portion abutting against a surface of the rotor core on the first end side in the axial direction, the rotor shaft having an outside threaded structure on a second end side in the axial direction, the rotor shaft being inserted through the center hole of the rotor core;
a nut portion that is in engagement with the outside threaded structure of the rotor shaft; and
a washer disposed between an end of the rotor core on the second end side in the axial direction and an end of the nut portion on the first end side in the axial direction, wherein
a position of a plane in which the washer and the rotor core are in contact with each other is located, in the rotor shaft, closer to the first end side in the axial direction than is the outside threaded structure when the rotor core is attached to the rotor shaft by fastening the nut portion to the outside threaded structure of the rotor shaft.
The rotary electric machine rotor according to claim 1, wherein the nut portion has a thin portion for swaging, the thin portion for swaging extending toward the second end side in the axial direction.
The rotary electric machine rotor according to claim 2, wherein the thin portion for swaging comprises a plurality of thin portions for swaging that are spaced apart from each other in a circumferential direction.
The rotary electric machine rotor according to claim 3, wherein the thin portions for swaging are swaged to the outside threaded structure.
The rotary electric machine rotor according to claim 1, wherein the washer has a thickness that is set based on variations in axial thickness of the rotor core.
The rotary electric machine rotor according to claim 1, wherein the stopper portion is a diameter change portion of the rotor shaft, the diameter change portion being formed on the first end side in the axial direction.