Rotor of a rotating electric machine

Abstract

The surface pressure acting on the mating surfaces during press-fitting of the shaft into the rotor core is reduced while ensuring good strength of the rotor core. [Solution] The rotor core of the rotor of a rotating electric machine includes a plurality of elongated holes formed at intervals in the circumferential direction, each extending circumferentially along the shaft hole and axially along the central axis of the shaft hole. The inner circumferential surface of the elongated holes includes a pair of first surfaces that extend circumferentially and face each other radially with respect to the rotor core, two second surfaces that form the circumferential ends of the elongated holes, and four third surfaces that have a radius of curvature larger than the radius of curvature of the curved surfaces included in the second surfaces and are continuous with the corresponding first and second surfaces.

Description

Technical Field

[0001] The present disclosure relates to a rotor of a rotating electric machine including an annular rotor core and a shaft press-fitted into a shaft hole of the rotor core.

Background Art

[0002] Conventionally, a key formed so as to project toward the central axis on the inner peripheral surface of a shaft hole into which a rotor shaft is press-fitted, and recessed portions provided on both circumferential sides of the key and recessed radially outward from an inner peripheral contact surface that contacts the press-fitted rotor shaft and is non-contact with the rotor shaft are known (see, for example, Patent Document 1). In this rotor core, a plurality of long holes are drilled so as to extend in the circumferential direction including a portion separated radially outward by a predetermined wall thickness from a contact end portion that is a switching portion between the inner peripheral contact surface and the recessed portion. Each long hole extends by a first angle toward the key side with respect to a reference line that intersects the central axis and the contact end portion, and extends by a second angle determined to be greater than or equal to the first angle on the side opposite to the key side. Thereby, in the rotor core including such long holes, the contact end portion and the adjacent inner peripheral contact surface can be escaped (deformed) radially outward when the rotor shaft is press-fitted, so that the surface pressure on the contact end portion during press-fitting of the rotor shaft can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a rotating electric machine including a rotor core having the elongated holes described above, when the rotor shaft rotates, the centrifugal force acting on the rotor core expands the elongated holes in the circumferential direction, and stress is generated around both ends of the elongated holes, pressing the inner portion of the elongated holes against the rotor shaft. Furthermore, if the curvature of the portions forming both ends of the elongated holes is small, as in the rotor core described in Patent Document 1, stress may concentrate in the portions with low curvature, and the stress generated in the rotor core may exceed the allowable stress of the rotor core. In contrast, by defining both ends of the elongated holes with concave cylindrical surfaces having a diameter close to the radial length of the elongated holes in the rotor core, it may be possible to ensure the curvature of the portions defining both ends of the elongated holes and suppress stress concentration. However, in this case, the strength of the rotor core may be insufficient due to the increase in the opening area at both ends of the elongated holes.

[0005] Therefore, the primary objective of this disclosure is to ensure good strength of the rotor core while reducing the surface pressure acting on the mating surface when the shaft is press-fitted into the rotor core. [Means for solving the problem]

[0006] The rotor of a rotating electric machine according to the present disclosure includes an annular rotor core and a shaft press-fitted into a shaft hole of the rotor core, wherein the rotor core includes a plurality of elongated holes formed at intervals in the circumferential direction, each extending circumferentially along the shaft hole and axially along the central axis of the shaft hole, and the inner circumferential surface of the elongated holes includes a pair of first surfaces each extending circumferentially and facing the radial direction of the rotor core, two second surfaces each forming the ends of the elongated holes in the circumferential direction, and four third surfaces each having a radius of curvature greater than the radius of curvature of the curved surface included in the second surface and continuous with the corresponding first and second surfaces.

[0007] The rotor core of the rotor of the rotating electric machine of this disclosure has a plurality of elongated holes formed in the rotor core at circumferential intervals such that each elongated hole extends circumferentially along the shaft hole and axially along the central axis of the shaft hole. This reduces the surface pressure acting on the mating surfaces when the shaft is pressed into the rotor core, thereby suppressing tearing on the outer surface of the shaft and damage to the inner surface of the shaft hole (rotor core). Furthermore, the inner surface of the elongated hole includes a pair of first surfaces, two second surfaces, and four third surfaces. The pair of first surfaces each extend circumferentially along the rotor core and face each other radially along the rotor core. The two second surfaces each form the ends of the elongated holes in the circumferential direction of the rotor core. The four third surfaces each have a radius of curvature larger than the radius of curvature of the curved surfaces included in the second surfaces and are continuous with the corresponding first surfaces and the second surfaces. This allows for maintaining the radius of curvature of the curved surface included in the second surface while increasing the radius of curvature of the third surface, thereby suppressing the increase in the opening area at the end of the elongated hole. This suppresses stress concentration around the end of the elongated hole and ensures rigidity. As a result, it becomes possible to reduce the surface pressure acting on the mating surface when the shaft is pressed into the rotor core while ensuring good strength of the rotor core. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the rotor of the rotating electric machine disclosed herein. [Figure 2] This is a plan view showing an elongated hole formed in the rotor core of the rotor of the rotating electric machine of the present disclosure. [Figure 3] This is a magnified view of a key part showing an elongated hole formed in the rotor core of the rotor of the rotating electric machine of the present disclosure. [Modes for carrying out the invention]

[0009] Next, with reference to the drawings, embodiments for carrying out the invention of this disclosure will be described.

[0010] Figure 1 is a schematic diagram showing the rotor 1 of the rotating electric machine of the present disclosure. The rotor 1 shown in the figure is a so-called embedded magnet type (IPM type) rotor that, together with a stator (not shown), constitutes a rotating electric machine (e.g., a three-phase AC motor). As shown in the figure, the rotor 1 includes an annular rotor core 2, a plurality of permanent magnets 3 embedded in the rotor core 2 to form a plurality of magnetic poles, and a rotor shaft 4 fixed to the rotor core 2.

[0011] The rotor core 2 is formed by stacking a plurality of core plates 20, which are formed in an annular shape from electromagnetic steel sheets, for example by press working, in the axial direction, and includes a shaft hole 21, a plurality (for example, 16 in this embodiment) of magnet holding holes 22, and a plurality (for example, 8 in this embodiment) of elongated holes 23. The shaft hole 21, each magnet holding hole 22, and each elongated hole 23 are all formed by holes (slits) formed in each of the plurality of core plates 20 stacked in the axial direction communicating in that axial direction. The rotor core 2 may also be formed by, for example, pressure molding and sintering ferromagnetic powder.

[0012] The shaft hole 21 of the rotor core 2 is a through hole with the axis of the rotor core 2 as its central axis. Furthermore, multiple magnet holding holes 22 are arranged in the rotor core 2 in pairs at predetermined intervals (for example, 45° intervals in this embodiment), penetrating the rotor core 2 in the axial direction. One permanent magnet 3 is placed (fixed) in each magnet holding hole 22. As a result, eight magnetic poles are formed in the rotor core 2 in this embodiment. In addition, multiple elongated holes 23 are all substantially arc-shaped holes (slits), extending circumferentially along the shaft hole 21 and extending axially along the central axis of the shaft hole 21, with intervals between them in the circumferential direction.

[0013] The rotor shaft 4 is made of metal, and an enlarged diameter portion (not shown) that extends radially outward from its outer circumference is press-fitted into the shaft hole 21 so as to abut one end face of the rotor core 2, thereby fixing it to the rotor core 2. The rotor shaft 4 also has a heat transfer medium passage (not shown) formed therein, into which a liquid heat transfer medium (in this embodiment, a hydraulic fluid such as ATF) is supplied from a pump (not shown). The liquid heat transfer medium supplied to the heat transfer medium passage of the rotor shaft 4 flows into a heat transfer medium passage (not shown) formed in the rotor core 2 through a radial hole formed in the rotor shaft 4, and exchanges heat with the rotor core 2 and the rotor shaft 4.

[0014] Figure 2 is a plan view showing the elongated hole 23 formed in the rotor core 2 of the rotor 1, and Figure 3 is an enlarged view of the main part showing the elongated hole 23. As shown in these drawings, the inner circumferential surface 230 of the elongated hole 23 includes a pair of first surfaces 231a, 231b, two second surfaces 232a, 232b, and four third surfaces 233a, 233b, 233c, 233d. The pair of first surfaces 231a, 231b each extend in the circumferential direction of the rotor core 2 and face each other in the radial direction of the rotor core 2. In this embodiment, the first surface 231a is a concave curved surface in the shape of a concave cylindrical surface, and the first surface 231b is a convex curved surface in the shape of a cylindrical surface.

[0015] The two second surfaces 232a and 232b each form the ends of the elongated holes 23 in the circumferential direction of the rotor core 2, and are formed symmetrically with respect to the center line of the elongated holes 23 in the circumferential direction. In this embodiment, as shown in Figure 3, the second surface 232a includes a first concave cylindrical surface 232i continuous with the first surface 231a, a second concave cylindrical surface 232j continuous with the first surface 231b, and an intermediate surface 232m continuous with both the first and second concave cylindrical surfaces 232i and 232j. The radius of curvature of the first concave cylindrical surface 232i and the radius of curvature of the second concave cylindrical surface 232j may be the same or different. In this embodiment, the intermediate surface 232m is a flat surface. However, the intermediate surface 232m may be a concave cylindrical surface having a larger radius of curvature than the first and second concave cylindrical surfaces 232i and 232j. Furthermore, the intermediate surface 232m may be omitted, and the first and second concave cylindrical surfaces 232i and 232j may be directly connected.

[0016] In this embodiment, the four third surfaces 233a, 233b, 233c, and 233d are all concave cylindrical surfaces. The third surfaces 233a and 233c are formed symmetrically with respect to the center line in the circumferential direction of the elongated hole 23, and the third surfaces 233b and 233d are formed symmetrically with respect to the center line in the circumferential direction of the elongated hole 23.

[0017] Furthermore, the third surface 233a has a larger radius of curvature than the larger of the first and second concave cylindrical surfaces 232i and 232j of the second surface 232a, and is continuous with the first surface 231a and the first concave cylindrical surface 232i of the second surface 232a. Furthermore, the third surface 233b has a larger radius of curvature than the larger of the first and second concave cylindrical surfaces 232i and 232j of the second surface 232a, and is continuous with the first surface 231b and the second concave cylindrical surface 232j of the second surface 232a. Furthermore, the third surface 233c has a larger radius of curvature than the larger of the first and second concave cylindrical surfaces (not shown) of the second surface 232b, and is continuous with the first surface 231a and the first concave cylindrical surface of the second surface 232b. Furthermore, the third surface 233d has a larger radius of curvature than the larger of the radii of curvature of the first and second concave cylindrical surfaces of the second surface 232b, and is continuous with both the first surface 231b and the second concave cylindrical surface of the second surface 232b.

[0018] In the rotor 1 configured as described above, multiple elongated holes 23 are formed in the rotor core 2 at circumferential intervals, each extending circumferentially along the shaft hole 21 and axially along the central axis of the shaft hole 21. This reduces the surface pressure acting on the mating surfaces when the rotor shaft 4 is pressed into the shaft hole 21 of the rotor core 2, thereby suppressing tearing on the outer surface of the rotor shaft 4 and the occurrence of dents or other damage on the inner surface of the shaft hole 21 (rotor core 2). Note that the number of elongated holes 23 in the rotor core 2 is not limited to eight, but can be arbitrarily determined according to the required reduction in surface pressure.

[0019] Furthermore, the inner circumferential surface 230 of the elongated hole 23 includes a pair of first surfaces 231a, 231b, two second surfaces 232a, 232b, and four third surfaces 233a, 233b, 233c, 233d. The pair of first surfaces 231a, 231b each extend in the circumferential direction of the rotor core 2 and face each other in the radial direction of the rotor core 2. The two second surfaces 232a, 232b each form the ends of the elongated hole 23 in the circumferential direction of the rotor core 2. The four third surfaces 233a, 233b, 233c, 233d each have a radius of curvature larger than the radius of curvature of the first and second concave cylindrical surfaces (curved surfaces) 232i, 232j, etc., included in the second surfaces 232a, 232b, and are continuous with the corresponding first surface 231a or 231b and second surface 232a or 232b.

[0020] This prevents the radii of curvature of the first and second concave cylindrical surfaces 232i, 232j, etc., included in the second surfaces 232a, 232b from becoming too small, while increasing the radii of curvature of the third surfaces 233a, 233b, 233c, 233d and suppressing an increase in the opening area at both ends of the elongated hole 23. In other words, compared to the case where the ends of the elongated hole 23 are defined by a concave cylindrical surface having a diameter close to the radial length of the elongated hole 23 of the rotor core 2 (see dashed line in Figure 3), in the rotor 1, as shown in Figure 3, the second surfaces 232a, 232b are formed to extend along the concave cylindrical surface shown by the dashed line in the figure, and the radii of curvature of the first and second concave cylindrical surfaces 232i, 232j can be sufficiently secured. Furthermore, by making the radii of curvature of the third surfaces 233a, 233b, 233c, and 233d larger than the radii of curvature of the first and second concave cylindrical surfaces 232i and 232j, the third surfaces 233a and 233b are brought closer to each other, and the third surfaces 233c and 233d are brought closer to each other, making it possible to add material around the elongated hole 23, i.e., in the shaded area in Figure 3. Therefore, stress concentration around both ends of the elongated hole 23 can be suppressed while ensuring rigidity. As a result, in the rotor 1, it is possible to reduce the surface pressure acting on the mating surface when the rotor shaft 4 is pressed into the rotor core 2, while ensuring good strength of the rotor core 2.

[0021] Moreover, the invention of the present disclosure is not limited to the above-described embodiments, and it is needless to say that various modifications can be made within the scope of the disclosure. Further, the above-described embodiments are merely specific forms of the invention described in the summary section of the invention, and do not limit the elements of the invention described in the summary section of the invention.

Industrial Applicability

[0022] The invention of the present disclosure can be used in the manufacturing industry of rotating electrical machines and the like.

Explanation of Signs

[0023] 1 Rotor, 2 Rotor core, 3 Permanent magnet, 4 Rotor shaft, 20 Core plate, 21 Shaft hole, 22 Magnet holding hole, 23 Long hole, 230 Inner peripheral surface, 231a, 231b First surface, 232a, 232b Second surface, 232i First concave cylindrical surface, 232j Second concave cylindrical surface, 232m Intermediate surface, 233a, 233b, 233c, 233d Third surface.

Claims

[Claim 1] In a rotor of a rotating electric machine, which includes an annular rotor core and a shaft that is press-fitted into a shaft hole of the rotor core, The rotor core includes a plurality of elongated holes, each extending circumferentially along the shaft hole and extending axially along the central axis of the shaft hole, and are formed at intervals in the circumferential direction. The rotor of a rotating electric machine, wherein the inner circumferential surface of the elongated hole includes a pair of first surfaces that extend in the circumferential direction and face the radial direction of the rotor core, two second surfaces that each form the end of the elongated hole in the circumferential direction, and four third surfaces that each have a radius of curvature larger than the radius of curvature of the curved surface included in the second surface and are continuous with the corresponding first and second surfaces.

Images