Rotor core

Abstract

To provide a rotor core having a skew structure that suppresses damage due to rotational stress, etc. [Solution] The rotor core 1 of the present disclosure is a rotor core 1 having a skew structure, the rotor core 1 comprises a plurality of core plates CP having the same shape, and a plurality of core parts formed by stacking the plurality of core plates CP and having a plurality of magnetic poles MP, the plurality of core parts of the rotor core 1 are offset in the circumferential direction of the skew angle and arranged in the direction of the rotation axis of the rotor core 1, the core plate CP comprises a first hole H1 provided on a first circle C1 centered on a position RA corresponding to the rotation axis, and a second hole H2 provided on the first circle C1, the angle from a predetermined reference line RL to the first hole H1 at each magnetic pole MP is defined as the first angle, the angle from the reference line RL to the second hole H2 is defined as the second angle, and the difference between the second angle and the first angle corresponds to the skew angle.

Description

Technical Field

[0001] The present disclosure relates to a rotor core having a skew structure.

Background Art

[0002] In a motor, a skew technique may be used to reduce rotational ripple. Patent Document 1 discloses a rotor (rotor core) using a skew technique.

[0003] Specifically, a rotor of an electric motor having a rotatable shaft and a rotor core in which a plurality of electromagnetic steel plates are laminated and arranged with a predetermined skew angle while being fixed to the shaft, the rotor core is provided with a key protrusion protruding inward, has an inner peripheral hole through which the shaft is inserted and engages with the shaft, the shaft is provided on an outer peripheral surface that engages with the rotor core, has a width that abuts against side surfaces of the key protrusions at both ends of the rotor core, and has a positioning key groove for the rotor core that is parallel to the axial direction. A rotor of an electric motor characterized by this is disclosed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a protruding structure such as a key protrusion that engages with the shaft is a structure that is likely to be damaged when, for example, rotational stress or the like is applied.

[0006] The present disclosure has been made in view of such circumstances, and one object is to provide a rotor core having a skew structure that suppresses damage due to rotational stress or the like.

Means for Solving the Problems

[0007] The rotor core of this disclosure is a rotor core having a skew structure, The rotor core is Multiple core plates having the same shape, The assembly comprises a plurality of core portions formed by stacking the plurality of core plates and having a plurality of magnetic poles, The rotor core is arranged such that the plurality of core portions are offset in the circumferential direction of the skew angle and aligned in the direction of the rotation axis of the rotor core. The aforementioned core plate is A first hole is provided on a first circle centered on the position corresponding to the rotation axis, A second hole provided on the first circle, The angle from a predetermined reference line to the first hole at each magnetic pole is defined as the first angle. The angle from the reference line to the second hole is defined as the second angle. A rotor core in which the difference between the second angle and the first angle corresponds to the skew angle. [Effects of the Invention]

[0008] According to this disclosure, a rotor core having a skew structure that suppresses damage due to rotational stress and the like is provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating the rotor core of the first embodiment relating to this disclosure. [Figure 2] This is a front view of the core plate of the first embodiment relating to this disclosure. [Figure 3] This is a front view of the core plate of the second embodiment relating to this disclosure. [Figure 4] This is a front view of the core plate of the third embodiment relating to this disclosure. [Figure 5] This is a diagram illustrating the rotor core of the fourth embodiment relating to this disclosure. [Figure 6]Front view of the core plate according to the fourth embodiment of the present disclosure. [Figure 7] Front view of the core plate according to the fifth embodiment of the present disclosure. [Figure 8] Front view of the core plate according to the sixth embodiment of the present disclosure. [Figure 9] Front view of the core plate according to the seventh embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "embodiments") will be described in detail with reference to the accompanying drawings. Throughout the description of the embodiments, the same elements are denoted by the same numbers or reference signs.

[0011] Also, the dimensional ratios in the drawings are different from the actual dimensional ratios, and are merely drawn for easy understanding of the description, and do not guarantee that the same parts are drawn with the same dimensions between the drawings.

[0012] Furthermore, in the drawings, for the sake of clarity, some of the parts having the same attributes may be only partially labeled with reference signs.

[0013] <<First Embodiment>> The rotor core 1 having a skew structure according to the first embodiment of the present disclosure will be described with reference to FIGS. 1 and 2.

[0014] The rotor core 1 according to the first embodiment of the present disclosure is a rotor core 1 used for a rotor RT disposed inside a stator (not shown), and is a rotor core 1 used for a rotor RT of a so-called inner rotor type motor.

[0015] FIG. 1 is a diagram for explaining the rotor core 1 according to the first embodiment of the present disclosure. In Figure 1, the upper part shows a side view of the rotor RT using rotor core 1, and the lower part shows a cross-sectional view along line AA and a cross-sectional view along line BB.

[0016] Furthermore, since the cross-sectional views along lines AA and BB are cross-sectional views of the boundary between the stacked core plates CP, they also represent a view of the front of one core plate CP from one side of the rotor shaft 20 (the left side in the upper diagram).

[0017] As shown in Figure 1, the rotor RT comprises a rotor shaft 20 which serves as the axis of rotation, and a rotor core 1 which is attached to the outer circumference of the rotor shaft 20 by shrink fitting or the like.

[0018] As shown in Figure 1, the rotor core 1 comprises a first core portion 11 and a second core portion 12.

[0019] In the first embodiment, the rotor core 1 is shown to have two core parts (a first core part 11 and a second core part 12), but the rotor core 1 may have three or more core parts.

[0020] In other words, the rotor core 1 only needs to have multiple core sections (two or more core sections) so that the skew structure described later can be formed.

[0021] As will be described later, the first core section 11 and the second core section 12 are offset in the circumferential direction of the skew angle and are arranged in line with the direction of the rotation axis of the rotor core 1 (i.e., the extending direction of the rotor shaft 20). The circumferential direction refers to the direction around the rotation center of the rotor core 1, that is, the circumferential direction along the outer circumference of the rotor shaft 20, which is the axis of rotation.

[0022] The first core section 11 and the second core section 12 are formed by laminating core plates CP made of electrical steel sheets, and the core plate CP used in the first core section 11 and the core plate CP used in the second core section 12 have the same shape.

[0023] As shown in Figure 1, both the first core section 11 and the second core section 12 have multiple sets of closely spaced magnets MG arranged at equal intervals in the circumferential direction. Alternatively, a pair of adjacent magnets MG may be replaced with a single larger magnet, so that one magnet forms one magnetic pole MP.

[0024] Since a pair of adjacent magnets MG form one magnetic pole MP, the first core portion 11 and the second core portion 12 are core portions having multiple magnetic poles MP in the circumferential direction. In the cross-sectional diagrams along lines AA and BB, the boundary between adjacent magnetic poles MP is indicated by a dotted line.

[0025] As described above, the rotor core 1 comprises a plurality of core plates CP having the same shape, and a plurality of core portions (in this example, a first core portion 11 and a second core portion 12) formed by stacking the plurality of core plates CP and having a plurality of magnetic poles MP.

[0026] Next, we will explain the stacked core plates CP. Figure 2 is a front view of the core plate CP of the first embodiment according to this disclosure. Figure 2 is a front view of the core plate CP seen from one side of the rotor shaft 20 (the left side of the upper diagram in Figure 1). As explained earlier, all stacked core plates CP have the same shape (structure) as described with reference to Figure 2.

[0027] Furthermore, in Figure 2, similar to the cross-sectional views along line AA and line BB in Figure 1, the boundary between adjacent magnetic poles MP is indicated by a dotted line. More precisely, the region labeled as magnetic pole MP in Figure 2 is sometimes referred to as the magnetic pole corresponding region, as it becomes magnetic pole MP when magnets MG are placed there.

[0028] Furthermore, in Figure 2, the line passing through the position RA corresponding to the rotation axis of the core plate CP and the circumferential center position of the first hole H1 on the first circle C1 is shown as the center line L1 of the first hole H1.

[0029] Similarly, the line passing through the position RA corresponding to the axis of rotation of the core plate CP and the circumferential center position of the second hole H2 on the first circle C1 is shown as the centerline L2 of the second hole H2.

[0030] As shown in Figure 2, the core plate CP, in a front view, has an annular plate shape overall. The core plate CP includes a central hole CH located in the center, which forms a hole into which a rotor shaft 20 (not shown) is inserted, and a pair of magnet placement holes MGH located at multiple equal intervals along the outer circumference, which form holes for arranging a pair of magnets MG (not shown).

[0031] Furthermore, the core plate CP includes a first hole H1 provided on a first circle C1 centered on position RA corresponding to the rotation axis (more precisely, position RA is the central axis of the rotor shaft 20 which is the rotation axis), and a second hole H2 provided on the first circle C1.

[0032] Specifically, the first hole H1 is formed as a first angle where the angle from a predetermined reference line RL to the first hole H1 at each magnetic pole MP is half of the angle α, and the second hole H2 is formed as a second angle where the angle from the reference line RL to the second hole H2 is half of the angle α. In Figure 2, angles in the counterclockwise direction from the reference line RL are shown as negative values, and angles in the clockwise direction are shown as positive values.

[0033] More precisely, the first hole H1 is formed as a first angle where the angle from the nearest reference line RL to the first hole H1 is half of angle α, and the second hole H2 is formed as a second angle where the angle from the reference line RL adjacent to the reference line RL closest to the first hole H1 to the second hole H2 is half of angle α.

[0034] Furthermore, the reference line RL shown in Figure 2 is, more precisely, a reference line corresponding to a predetermined reference line RL at each magnetic pole MP (see Figure 1), and is therefore sometimes referred to as a corresponding reference line.

[0035] In the first embodiment, a predetermined reference line RL at each magnetic pole MP (see Figure 1) is the d-axis of a dq coordinate system with reference to the north pole direction of the magnetic pole MP.

[0036] However, it is not limited to the d-axis; it may also be the q-axis of a dq coordinate system that uses the north pole direction of the magnetic pole MP as the reference. The reference line RL is given to each magnetic pole MP, and it is sufficient if it is an axis located at the same position when the magnetic poles MP are superimposed.

[0037] In the first embodiment, the first angle is half the angle α which is the skew angle, and the first hole H1 is located on the other side in the circumferential direction (counterclockwise side in Figure 2) with respect to the nearest reference line RL.

[0038] Furthermore, in the first embodiment, the second angle is half the angle α which is the skew angle, and the second hole H2 is located on one side in the circumferential direction (clockwise in Figure 2) relative to the reference line RL adjacent to the reference line RL that is close to the first hole H1.

[0039] Therefore, the difference between the second angle and the first angle has an angle corresponding to the skew angle α [= +α / 2 - (-α / 2)]. In the above, angles in the clockwise direction from the reference line RL are represented by negative signs in Figure 2, and conversely, angles in the clockwise direction are represented by positive signs. However, the relationship between positive and negative signs can be reversed.

[0040] In this case, the difference between the second angle and the first angle is angle -α. However, since the magnitude of the angle itself cannot be negative, the difference between the second angle and the first angle can be understood as the absolute value of the difference.

[0041] Furthermore, even if the difference between the second angle and the first angle is angle + α, the absolute value remains the same, which is angle + α. Therefore, more accurately, the difference between the second angle and the first angle can always be understood as the absolute value of the difference between the second angle and the first angle.

[0042] By stacking the core plates CP as described above, a first core portion 11 and a second core portion 12 are formed.

[0043] Specifically, the first core portion 11 is formed by stacking multiple core plates CP such that the first holes H1 and second holes H2 of all the core plates CP overlap, and, similar to a rotor core generally formed by stacking electrical steel sheets, the core plates CP are integrated by applying pressure in the stacking direction while they are stacked.

[0044] The second core section 12 is formed in the same way as the first core section 11, by stacking multiple core plates CP such that the first holes H1 and second holes H2 of all the core plates CP overlap, and then integrating the core plates CP by applying pressure in the stacking direction while they are stacked.

[0045] Then, when attaching (fixing) the first core portion 11 and the second core portion 12 to the rotor shaft 20, as shown in Figure 1, the hole formed by the first hole H1 in the core plate CP of the first core portion 11 and the hole formed by the second hole H2 in the core plate CP of the second core portion 12 are made to overlap.

[0046] Furthermore, when attaching to the rotor shaft 20, instead of aligning the first core portion 11 and the second core portion 12 in the circumferential direction, they may be aligned in advance before being attached to the rotor shaft 20, and the specific procedure for attaching to the rotor shaft 20 is not particularly limited.

[0047] As shown in Figure 1, with respect to the line OL where the center line L1 of the first hole H1 and the center line L2 of the second hole H2 overlap, the reference line RL (d-axis) closest to the hole in the first core portion 11 formed by the first hole H1 of the core plate CP is located at a position shifted by half an angle α, which is the skew angle, in the clockwise direction, and the reference line RL (d-axis) closest to the hole in the second core portion 12 formed by the second hole H2 of the core plate CP is located at a position shifted by half an angle α, which is the skew angle, in the counterclockwise direction.

[0048] Therefore, the rotor core 1 is made up of multiple core parts (in this example, the first core part 11 and the second core part 12) that are offset in the circumferential direction by an angle α, which is the skew angle.

[0049] Furthermore, the rotor core 1 of the first embodiment described above does not have any protruding structures that are prone to damage due to rotational stress, etc., and therefore the rotor core 1 is designed to suppress damage due to rotational stress, etc.

[0050] In the above example, the case where the first hole H1 is located on the other side in the circumferential direction (counterclockwise in Figure 2) relative to the nearest reference line RL was shown, but the first hole H1 may also be located on the reference line RL.

[0051] In this case, the second angle should be the skew angle α, and the second hole H2 should be positioned on one side in the circumferential direction (clockwise in Figure 2) relative to the reference line RL adjacent to the reference line RL closest to the first hole H1 (i.e., the reference line RL on which the first hole H1 is located).

[0052] Furthermore, if the second angle is the skew angle α, the second hole H2 may be located on the other side of the circumferential direction (counterclockwise in Figure 2) relative to the reference line RL adjacent to the reference line RL closest to the first hole H1 (i.e., the reference line RL on which the first hole H1 is located), instead of on one side of the circumferential direction (clockwise in Figure 2).

[0053] By the way, the core plate CP described above can be manufactured by punching or other processes, but in this case, one side of the plate will be a rounded surface.

[0054] As will be explained later, when fixing the rotor core 1 to the rotor shaft 20 by shrink fitting, the hole formed by the central hole CH of the core plate CP through which the rotor shaft 20 passes is designed to have an inner diameter smaller than the outer diameter of the rotor shaft 20.

[0055] Therefore, the rotor core 1 is constantly subjected to stress in a direction that expands radially outward by the rotor shaft 20.

[0056] Therefore, it is preferable to overlap the first core portion 11 and the second core portion 12 so that their sagging sides are on the same side, thereby reducing the unevenness of the hole through which the rotor shaft 20 passes, preventing uneven stress that can cause stress degradation from being applied, and thus suppressing damage and other problems.

[0057] Furthermore, in the first embodiment, the core plate CP only needs to be stacked when forming the first core portion 11 and the second core portion 12, and there is no need to stack the front and back surfaces of the core plate CP in the first core portion 11 and the second core portion 12. Therefore, as described above, the first core portion 11 and the second core portion 12 can be stacked so that the sagging sides are on the same side, resulting in a rotor core 1 that is less prone to damage.

[0058] <<Second Embodiment>> Next, a rotor core 1 having a skew structure according to the second embodiment of this disclosure will be described with reference to Figure 3.

[0059] The rotor core 1 of the second embodiment has the same basic configuration as the rotor core 1 of the first embodiment, and the only difference between the second embodiment and the first embodiment is the number of first holes H1 and second holes H2 formed in the core plate CP.

[0060] Therefore, the following will mainly describe the differences from the first embodiment, and explanations of similar points may be omitted.

[0061] Figure 3 is a front view of the core plate CP of the second embodiment according to this disclosure, and corresponds to Figure 2.

[0062] As shown in Figure 3, the core plate CP of the second embodiment differs from that of the first embodiment in that the first hole H1 and the second hole H2 are alternately provided in the circumferential direction.

[0063] In other words, the core plate CP of the second embodiment has first holes H1 and second holes H2 evenly distributed in the circumferential direction, so the first core portion 11 and the second core portion 12 formed by stacking these core plates CP also have holes evenly distributed in the circumferential direction.

[0064] Therefore, when there is a hole in a part of the circumferential direction, the weight balance in the circumferential direction becomes uniform, making it possible to suppress the wobble of the rotor RT during rotation caused by the unevenness of the circumferential weight balance.

[0065] <<Third Embodiment>> Next, a rotor core 1 having a skew structure according to the third embodiment of this disclosure will be described with reference to Figure 4.

[0066] The rotor core 1 of the third embodiment has the same basic configuration as the rotor core 1 of the second embodiment, and the only difference between the third embodiment and the second embodiment is that, in addition to the first hole H1 and the second hole H2 formed in the core plate CP, there are further holes provided.

[0067] Therefore, the following will mainly describe the differences from the second embodiment, and explanations of similar points may be omitted.

[0068] Figure 4 is a front view of the core plate CP of the third embodiment according to this disclosure, and corresponds to Figure 3.

[0069] As shown in Figure 4, the core plate CP of the third embodiment has a plurality of intermediate holes MH on the first circle C1 provided between adjacent first holes H1 and second holes H2.

[0070] Furthermore, if we define a region consisting of two adjacent magnetic poles MP as the first region AR1, then in the third embodiment, four adjacent first regions AR1 are defined, and the first hole H1, the second hole H2, and the intermediate hole MH within each first region AR1 are line-symmetric with respect to the boundary line between adjacent first regions AR1, and point-symmetric with respect to the center of the first circle C1 (i.e., the position RA corresponding to the rotation axis of the core plate CP).

[0071] Therefore, similar to the second embodiment, since holes are uniformly formed in the circumferential direction, a rotor RT with good circumferential weight balance can be formed.

[0072] On the other hand, when shrink-fitting and fixing the rotor core 1 (first core portion 11 and second core portion 12) to the rotor shaft 20 (not shown), the rotor core 1 is heated to expand the hole through which the central rotor shaft 20 passes (the hole formed by the central hole CH of the core plate CP) by thermal expansion, and the rotor shaft 20 is inserted into the expanded hole.

[0073] As the rotor core 1 cools, the enlarged hole shrinks back to its original size, fixing it to the rotor shaft 20. However, for this to occur, the inner diameter of the hole when it shrinks must be smaller than the outer diameter of the rotor shaft 20.

[0074] Therefore, the rotor core 1 is constantly subjected to stress in a direction that expands radially outward by the rotor shaft 20.

[0075] However, as in the third embodiment, if a large number of holes (first hole H1, second hole H2, and intermediate hole MH) are densely arranged on the first circle C1, the stress applied in the radially outward direction at the holes is relieved, thereby suppressing deterioration and damage of the rotor core 1 due to stress.

[0076] <<Fourth Embodiment>> Next, a rotor core 1 having a skew structure according to the fourth embodiment of this disclosure will be described with reference to Figures 5 and 6.

[0077] In the first embodiment, a core plate CP was described that forms a rotor core 1 having a first core portion 11 and a second core portion 12 that are offset in the circumferential direction by an angle α, which is a skew angle, by using the same core plate CP. However, there are cases where it is desired to have a rotor core 1 having three or more core portions that are offset in multiple stages in the axial direction by an angle α, which is a skew angle.

[0078] Therefore, in the fourth embodiment, we will describe a case in which three core portions arranged in the axial direction are sequentially offset in the circumferential direction, which is a skew angle α, by using the same core plate CP.

[0079] Therefore, the rotor core 1 having a skew structure in the fourth embodiment differs from the rotor core 1 having a skew structure in the first embodiment in that it has three core parts, and therefore differs in that the holes formed in the core plate CP include a third hole H3 in addition to the first hole H1 and the second hole H2.

[0080] Furthermore, the fourth embodiment differs from the first embodiment in that the reference line RL is the q-axis of the dq coordinate system referenced to the north pole direction of the magnetic pole MP. However, in other respects, it is basically the same as the first embodiment. Therefore, the following will mainly describe the differences from the first embodiment, and explanations of points that are the same as the first embodiment may be omitted.

[0081] Figure 5 is a diagram illustrating the rotor core 1 of the fourth embodiment according to this disclosure, and corresponds to the side view of the rotor RT using the upper rotor core 1 in Figure 1.

[0082] As shown in Figure 5, the rotor RT comprises a rotor shaft 20 which serves as the axis of rotation, and a rotor core 1 which is attached to the outer circumference of the rotor shaft 20 by shrink fitting or the like.

[0083] As shown in Figure 5, the rotor core 1 comprises a first core portion 11, a second core portion 12, and a third core portion 13. As will be described later, the second core portion 12 is positioned circumferentially offset from the first core portion 11 by an angle α, which is a skew angle, and the third core portion 13 is positioned circumferentially offset from the second core portion 12 by an angle α, which is a skew angle.

[0084] As mentioned above, the first core portion 11, the second core portion 12, and the third core portion 13 are all formed by stacking multiple core plates CP having the same shape (same structure). Next, the core plate CP of the fourth embodiment according to this disclosure will be described with reference to Figure 6.

[0085] Figure 6 is a front view of the core plate CP of the fourth embodiment according to this disclosure, and corresponds to Figure 2. In Figure 6, the first hole H1, the second hole H2, and the third hole H3 are shown as circular holes, but they may be formed as elongated holes, as in the first embodiment.

[0086] Furthermore, in Figure 2, the boundary between adjacent magnetic poles MP was shown with a dotted line. However, the q-axis of the dq coordinate system, which is based on the north pole direction of magnetic pole MP, is located at the boundary between adjacent magnetic poles MP and coincides with the reference line RL, so the dotted line is omitted from the illustration.

[0087] As shown in Figure 6, the core plate CP of the fourth embodiment includes a third hole H3 provided on the first circle C1.

[0088] Specifically, the first hole H1 lies on the reference line RL, and the second hole H2 lies on one side in the circumferential direction (clockwise in Figure 6) of the reference line RL adjacent to the reference line RL closest to the first hole H1 (i.e., the reference line RL on which the first hole H1 is located).

[0089] Furthermore, the second hole H2 is positioned at a second angle such that the angle from the reference line RL to the second hole H2 is the skew angle α. In Figure 6, as in Figure 2, angles in the counterclockwise direction from the reference line RL are shown as negative values, and angles in the clockwise direction are shown as positive values.

[0090] Furthermore, the third hole H3 is located on the opposite side in the circumferential direction (counterclockwise in Figure 6) from the reference line RL that is closest to the second hole H2.

[0091] Furthermore, the third hole H3 is positioned at a third angle where the angle from the reference line RL to the third hole H3 is the skew angle, which is angle -α.

[0092] Therefore, it has an angle corresponding to the difference between the third angle and the first angle, or more precisely, the angle α [=|-α-0|] whose absolute value is the skew angle.

[0093] In the fourth embodiment, as in the first embodiment, the difference between the second angle and the first angle corresponds to the skew angle α[=+α-0], and more precisely, the absolute value of the difference is also α[=|+α-0|].

[0094] Then, by stacking the core plates CP as described above, the first core portion 11, the second core portion 12, and the third core portion 13 are formed.

[0095] Specifically, the first core portion 11 is formed by stacking multiple core plates CP such that the first holes H1, second holes H2, and third holes H3 of all the core plates CP overlap, and then integrating the core plates CP by applying pressure in the stacking direction, as described in the first embodiment.

[0096] Furthermore, the second core portion 12 is formed in the same way as the first core portion 11, by stacking multiple core plates CP such that the first holes H1, second holes H2, and third holes H3 of all the core plates CP overlap, and then integrating the core plates CP by applying pressure in the stacking direction while they are stacked.

[0097] Furthermore, the third core portion 13 is formed in the same way as the first core portion 11 and the second core portion 12, by stacking multiple core plates CP such that the first holes H1, second holes H2, and third holes H3 of all the core plates CP overlap, and then integrating the core plates CP by applying pressure in the stacking direction in this stacked state.

[0098] Then, when attaching (fixing) the first core portion 11, the second core portion 12, and the third core portion 13 to the rotor shaft 20, the hole formed by the second hole H2 in the core plate CP of the first core portion 11, the hole formed by the first hole H1 in the core plate CP of the second core portion 12, and the hole formed by the third hole H3 in the core plate CP of the third core portion 13 are made to overlap.

[0099] As a result, the second core portion 12 is shifted by an angle α, which is the skew angle, relative to the first core portion 11 in the other circumferential direction (counterclockwise direction in Figure 6), and the third core portion 13 is also shifted by an angle α, which is the skew angle, relative to the second core portion 12 in the other circumferential direction (counterclockwise direction in Figure 6).

[0100] In the above, we described the case in which three core sections (first core section 11, second core section 12, and third core section 13) can be formed on the same core plate CP, sequentially offset in the circumferential direction by the skew angle. However, if a fourth hole is provided on the other side in the circumferential direction (counterclockwise side in Figure 6) relative to the third hole H3, that is, a fourth hole provided on the other side in the circumferential direction of the reference line RL at a fourth angle that is twice the skew angle α from the reference line RL, then by stacking the same core plate CP, it is possible to form a fourth core section that is further offset by the skew angle.

[0101] Thus, according to the fourth embodiment, it is possible to form a large number of core parts using the same core plate CP, and as the number of core parts increases, it is possible to significantly reduce costs compared to when a core plate of a different shape is manufactured.

[0102] <<Fifth Embodiment>> Next, a rotor core 1 having a skew structure according to the fifth embodiment of this disclosure will be described with reference to Figure 7.

[0103] The rotor core 1 of the fifth embodiment also has the same basic configuration as the rotor core 1 of the fourth embodiment, and the only difference between the fifth embodiment and the fourth embodiment is the number of first holes H1, second holes H2, and third holes H3 formed in the core plate CP.

[0104] Therefore, the following will mainly describe the differences from the fourth embodiment, and explanations of similar points may be omitted.

[0105] Figure 7 is a front view of the core plate CP of the fifth embodiment according to this disclosure, and corresponds to Figure 4.

[0106] As shown in Figure 7, the core plate CP of the fifth embodiment differs from that of the fourth embodiment in that the set of second holes H2 and third holes H3 and the first hole H1 are alternately provided in the circumferential direction.

[0107] In other words, the core plate CP of the fifth embodiment has first holes H1 evenly distributed in the circumferential direction, second holes H2 evenly distributed in the circumferential direction, and third holes H3 evenly distributed in the circumferential direction. Therefore, the first core portion 11, second core portion 12, and third core portion 13 formed by stacking these core plates CP also have holes evenly distributed in the circumferential direction.

[0108] Therefore, when there is a hole in a part of the circumferential direction, the weight balance in the circumferential direction becomes uniform, making it possible to suppress the wobble of the rotor RT during rotation caused by the unevenness of the circumferential weight balance.

[0109] <<Sixth Embodiment>> Next, a rotor core 1 having a skew structure according to the sixth embodiment of this disclosure will be described with reference to Figure 8.

[0110] The rotor core 1 of the sixth embodiment has the same basic configuration as the rotor core 1 of the fifth embodiment, and the only difference between the sixth embodiment and the fifth embodiment is that, in addition to the first hole H1 and the second hole H2 formed in the core plate CP, there are further holes provided.

[0111] Therefore, the following will mainly describe the differences from the fifth embodiment, and explanations of similar points may be omitted.

[0112] Figure 8 is a front view of the core plate CP of the sixth embodiment according to this disclosure, and corresponds to Figure 7.

[0113] As shown in Figure 8, the core plate CP of the sixth embodiment includes a plurality of intermediate holes MH on the first circle C1, which are provided between the set of adjacent second holes H2 and third holes H3 and the first hole H1.

[0114] Furthermore, if we define a region consisting of two adjacent magnetic poles MP as the first region AR1, then in the sixth embodiment, four adjacent first regions AR1 are defined. The second hole H2, the third hole H3, and the intermediate hole MH within these first regions AR1 are line-symmetric with respect to the boundary line between adjacent first regions AR1 (see reference line RL), and point-symmetric with respect to the center of the first circle C1 (i.e., the position RA corresponding to the rotation axis of the core plate CP).

[0115] Therefore, similar to the fifth embodiment, since holes are formed uniformly in the circumferential direction, a rotor RT with good circumferential weight balance can be formed.

[0116] On the other hand, when shrink-fitting and fixing the rotor core 1 (first core portion 11, second core portion 12, and third core portion 13) to the rotor shaft 20 (not shown), the rotor core 1 is heated to expand the hole through which the central rotor shaft 20 passes (the hole formed by the central hole CH of the core plate CP) by thermal expansion, and the rotor shaft 20 is inserted into the expanded hole.

[0117] As the rotor core 1 cools, the enlarged hole shrinks back to its original size, fixing it to the rotor shaft 20. However, for this to occur, the inner diameter of the hole when it shrinks must be smaller than the outer diameter of the rotor shaft 20.

[0118] Therefore, the rotor core 1 is constantly subjected to stress in a direction that expands radially outward by the rotor shaft 20.

[0119] However, as in the sixth embodiment, when a large number of holes (first hole H1, second hole H2, third hole H3, and intermediate hole MH) are densely arranged on the first circle C1, the stress applied in the direction of radial outward expansion at the holes is relieved, thereby suppressing deterioration and damage of the rotor core 1 due to stress.

[0120] <<Seventh Embodiment>> Next, a rotor core 1 having a skew structure according to the seventh embodiment of this disclosure will be described with reference to Figure 9.

[0121] The rotor core 1 of the seventh embodiment has the same basic configuration as the rotor core 1 of the fourth embodiment. The seventh embodiment differs from the fourth embodiment in that it makes it easier to confirm whether the first core portion 11, the second core portion 12, and the third core portion 13 are correctly positioned with a skew angle of α in the circumferential direction.

[0122] Therefore, the only difference is that a marker MK is provided at a predetermined position in the circumferential direction on the outer circumference of the core plate CP. Thus, below, we will mainly describe the differences from the fourth embodiment, and may omit explanations of similar points.

[0123] Figure 9 is a front view of the core plate CP of the seventh embodiment according to this disclosure, and corresponds to Figure 6.

[0124] As shown in Figure 9, the core plate CP of the seventh embodiment is provided with a pair of notches MK as markers at positions corresponding to the d-axis of adjacent magnetic poles MP, which are predetermined positions in the circumferential direction on the outer circumference.

[0125] Furthermore, as described in the fourth embodiment, when the rotor shaft 20 is provided with the first core portion 11, the second core portion 12, and the third core portion 13, it is possible to visually confirm whether the mark MK is correctly installed by observing that it is shifted in the direction of the circumferential angle α, which is the skew angle.

[0126] Furthermore, the markings MK on the core plate CP are not limited to a pair as described above; one marking or three or more marksings may be provided.

[0127] Although the above has been explained based on specific embodiments, this disclosure is not limited to the embodiments described above.

[0128] For example, the marker MK described in the seventh embodiment is applicable to any of the embodiments from the first to the sixth embodiment, and such application to the first to the sixth embodiment is also included in this disclosure.

[0129] Therefore, the scope of this disclosure also includes modifications and improvements to the embodiments, which will be apparent to those skilled in the art from the claims. [Explanation of symbols]

[0130] 1...Rotor core, C1...First circle, CP...Core plate, H1...First hole, H2...Second hole, H3...Third hole, MP...Magnetic pole, RA...Position, RL...Reference line

Claims

1. A rotor core having a skewed structure, The rotor core is Multiple core plates having the same shape, The assembly comprises a plurality of core portions formed by stacking the plurality of core plates and having a plurality of magnetic poles, The rotor core is arranged such that the plurality of core portions are offset in the circumferential direction of the skew angle and aligned in the direction of the rotation axis of the rotor core. The aforementioned core plate is A first hole is provided on a first circle centered on the position corresponding to the rotation axis, A second hole provided on the first circle, The angle from a predetermined reference line to the first hole at each magnetic pole is defined as the first angle. The angle from the reference line to the second hole is defined as the second angle. A rotor core in which the difference between the second angle and the first angle corresponds to the skew angle.

2. The aforementioned first angle is half the angle of the skew angle, The first hole is located on the other side in the circumferential direction with respect to the reference line. The second hole is located on one side in the circumferential direction with respect to the reference line adjacent to the reference line near the first hole, The rotor core according to claim 1, wherein the reference line is the d-axis or q-axis of a d-q coordinate system with reference to the north pole direction of the magnetic pole.

3. The core plate is provided with a third hole located on the first circle, The angle from the reference line to the third hole is defined as the third angle. The difference between the third angle and the first angle corresponds to the skew angle. The first hole is located on the reference line, The second hole is located on one side in the circumferential direction with respect to the reference line adjacent to the reference line in which the first hole is located. The third hole is located on the other side in the circumferential direction with respect to the reference line that is close to the second hole. The rotor core according to claim 1, wherein the reference line is the d-axis or q-axis of a d-q coordinate system with reference to the north pole direction of the magnetic pole.

4. The rotor core according to any one of claims 1 to 3, wherein the core plate is provided with a mark at a predetermined position in the circumferential direction on its outer circumference.

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