Rotor and rotary electric machine

Abstract

The present invention pertains a rotor (30) in which a plurality of magnetic poles, which are each constituted by a pair of permanent magnets (32) and a pair of magnet insertion holes (41) provided in an annular rotor core (31), are disposed in a circumferential direction, wherein: the pairs of magnet insertion holes are provided so as to sandwich the d-axis; the interval on the inner diameter side of the pair of magnet insertion holes is narrower than the interval on the outer diameter side; each of the magnet insertion holes has an inner diameter-side flux barrier (43) and an outer diameter-side flux barrier (44); a first through-hole (42) crossing the d-axis is formed between the pair of magnet insertion holes; and the rotor core has an inner diameter-side bridge (35) formed between the inner diameter-side flux barrier and the first through-hole, and at least one central bridge (37) dividing the first through-hole in the circumferential direction.

Description

Rotor and Rotating Electric Machine

[0001] The present disclosure relates to a rotor and a rotating electric machine.

[0002] As a conventional permanent magnet type rotating electric machine having a permanent magnet in a rotor, a rotating electric machine having a rotor in which a magnetic resistance is increased by providing an opening between V-shaped permanent magnets to improve torque is disclosed. In this rotor, in order to ensure the strength against the centrifugal force during rotation, an inner diameter side bridge arranged symmetrically with respect to the d-axis is arranged in the opening (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2011-259688

[0004] However, in a conventional rotating electric machine, by widening the width of the inner diameter side bridge, the bending stress generated in the outer peripheral side bridge can be reduced, but the magnetic flux leaking to the inner diameter side increases and the torque decreases. When the width of the inner diameter side bridge is narrowed, a large bending stress is generated in the inner diameter bridge due to the centrifugal force. Thus, in a conventional rotating electric machine, there is a problem that it is difficult to achieve both improvement in mechanical strength and improvement in magnetic performance.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a rotating electric machine capable of achieving both improvement in mechanical strength and improvement in magnetic performance.

[0006] The rotor of the present disclosure is a rotor in which a plurality of magnetic poles composed of a pair of magnet insertion holes provided in an annular rotor core and a pair of permanent magnets respectively inserted into the pair of magnet insertion holes are arranged in the circumferential direction, the pair of magnet insertion holes are provided with the d-axis interposed therebetween, the interval on the inner diameter side of the pair of magnet insertion holes is narrower than the interval on the outer diameter side, each magnet insertion hole has an inner diameter side flux barrier and an outer diameter side flux barrier on both sides in the longitudinal direction of the permanent magnet, a first through hole crossing the d-axis is formed between the pair of magnet insertion holes, and the rotor core has an inner diameter side bridge formed between the inner diameter side flux barrier and the first through hole, and at least one central bridge dividing the first through hole in the circumferential direction.

[0007] In the rotor of this disclosure, a first through-hole is formed between a pair of magnet insertion holes, traversing the d-axis. The rotor core has an inner diameter side bridge formed between the inner diameter side flux barrier and the first through-hole, and at least one central bridge that divides the first through-hole in the circumferential direction. This makes it possible to achieve both improved mechanical strength and improved magnetic performance.

[0008] This is a cross-sectional view of a rotating electric machine according to Embodiment 1. This is a cross-sectional view of a rotor according to Embodiment 1. This is an enlarged cross-sectional view of a rotor according to Embodiment 1. This is an enlarged cross-sectional view of a rotor of a comparative example according to Embodiment 1. This is a diagram for explaining the characteristics of a rotor according to Embodiment 1. This is a cross-sectional view of a rotor according to Embodiment 2. This is an enlarged cross-sectional view of a rotor according to Embodiment 2. This is a diagram for explaining the characteristics of a rotor according to Embodiment 2. This is an enlarged cross-sectional view of a rotor of a comparative example according to Embodiment 2. This is a diagram for explaining the characteristics of a rotor according to Embodiment 2. This is an enlarged cross-sectional view of a rotor a cross-sectional view of a rotor according to Embodiment 3. This is an enlarged cross-sectional view of a rotor according to Embodiment 3. This is an enlarged cross-sectional view of a rotor according to Embodiment 4. This is an enlarged cross-sectional view of a rotor according to Embodiment 5.

[0009] Hereinafter, a rotor and a rotating electric machine relating to embodiments for implementing this disclosure will be described in detail with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts.

[0010] Embodiment 1. Figure 1 is a cross-sectional view of a rotating electric machine according to Embodiment 1. Figure 1 is a cross-sectional view in a direction parallel to the rotation axis, which will be described later. The rotating electric machine 1 according to this embodiment has a cylindrical housing 10, and a stator 20 is fixed inside it. The stator 20 has an annular stator core 21 and a coil 22. A rotor 30 is provided on the inner diameter side of the stator 20, with a gap between it and the stator core 21. The rotor 30 has an annular rotor core 31, a permanent magnet 32 ​​embedded in the rotor core 31, a cylindrical rotation shaft 33 fastened to the center of the rotor core 31, and an end plate 34 for preventing the permanent magnet 32 ​​from scattering. The rotation shaft 33 is rotatably held in the housing 10 via a bearing 11. The stator 20 and the rotor 30 are arranged coaxially with respect to a rotation center 12. The rotor 30 rotates relative to the stator 20 with respect to the rotation center 12.

[0011] The direction parallel to the rotation axis 33 is called the axial direction, the direction perpendicular to the rotation axis 33 is called the radial direction, and the direction of rotation around the rotation axis 33 is called the circumferential direction. The inner diameter side is the direction approaching the rotation axis 33 in the radial direction, and the outer diameter side is the direction moving away from the rotation axis 33 in the radial direction. The stator core 21 and rotor core 31 are constructed, for example, by stacking multiple annular-shaped electromagnetic steel sheets in the axial direction. The permanent magnet 32 ​​is divided into multiple parts and arranged in the axial direction.

[0012] Figure 2 is a cross-sectional view of the rotor according to this embodiment, taken in a direction perpendicular to the rotation axis. Note that the rotation axis is omitted in Figure 2. The magnetic pole center extending from the rotation center 12 toward the outer diameter side of the rotor core 31 is defined as the d-axis, and the direction electrically and magnetically perpendicular to the d-axis is defined as the q-axis. A pair of magnet insertion holes 41 are formed in the rotor core 31 with the d-axis in between. The pair of magnet insertion holes 41 are configured such that the distance between them on the outer diameter side is greater than the distance between them on the inner diameter side. In other words, the pair of magnet insertion holes 41 are configured to open in a V-shape toward the outer diameter side. Permanent magnets 32 are inserted into each of the pair of magnet insertion holes 41. A first through hole 42 is formed between the inner diameter sides of the pair of magnet insertion holes 41. The first through hole 42 is formed across the d-axis. One magnetic pole is formed by the pair of magnet insertion holes 41, the permanent magnets 32 inserted into each of the pair of magnet insertion holes 41, and the first through hole 42. Each magnetic pole is arranged in a circumferential direction. In the rotor of this embodiment shown in Figure 2, there are eight magnetic poles.

[0013] Figure 3 is an enlarged cross-sectional view showing one magnetic pole of the rotor according to this embodiment. A permanent magnet 32 ​​is inserted in the center of the magnet insertion hole 41, and both ends of the permanent magnet 32 ​​in the magnet insertion hole 41 are hollow. These hollows are provided to prevent magnetic flux leakage from the permanent magnet 32. The hollow on the inner diameter side of the magnet insertion hole 41 is called the inner diameter side flux barrier 43, and the hollow on the outer diameter side is called the outer diameter side flux barrier 44. The portion sandwiched between the inner diameter side flux barrier 43 and the first through hole 42 is called the inner diameter side bridge 35, and the portion sandwiched between the outer diameter side flux barrier 44 and the outer circumferential surface of the rotor core 31 is called the outer diameter side bridge 36. Furthermore, the first through hole 42 is divided into two in the circumferential direction, and the portion that divides the first through hole 42 into two is called the central bridge 37. The central bridge 37 is formed on the d axis. In the rotor of this embodiment, the first through-hole 42, the inner diameter side flux barrier 43, and the outer diameter side flux barrier 44 are composed of through-holes that penetrate the rotor core 31 in the axial direction. In addition, the inner diameter side bridge 35, the outer diameter side bridge 36, and the central bridge 37 are part of the rotor core 31.

[0014] As shown in Figure 3, the first through-hole 42, which is divided by the central bridge 37, is rectangular in shape with its longitudinal direction along the radial direction. The first through-hole 42 reduces the mass of the rotor core 31 and relieves the bending stress acting on the inner diameter bridge 35, the outer diameter bridge 36, and the central bridge 37. Here, "rectangular" means that it is composed of two pairs of sides having opposite straight sections, and in particular, the two opposing sides in the longitudinal direction do not have to be parallel to each other. For example, if the two opposing sides in the longitudinal direction are provided along the radial direction, the first through-hole 42 may be a rectangular shape that is close to a trapezoid or triangle. Also, the corners of the first through-hole 42 do not necessarily have to be right angles, and may be arc-shaped, curved, etc., in order to prevent stress concentration.

[0015] The radial width of the outer diameter bridge 36 is preferably as small as possible to improve torque. In the rotor of this embodiment, the inner diameter surface of the first through hole 42 and the inner diameter surface of the inner diameter flux barrier 43 are located at approximately the same distance from the center of rotation. Therefore, the difference in stress generated when the rotating shaft 33 is pressed into the rotor core 31 attached to the first through hole 42 and the inner diameter flux barrier 43, respectively, and the centrifugal force generated when the rotor rotates are reduced. The sum of the circumferential widths of the two divided first through holes 42 is set to be greater than the sum of the circumferential width of the central bridge 37 and the circumferential widths of the two inner diameter bridges 35. By setting the circumferential width of the first through hole 42 to be larger, magnetic flux leakage can be suppressed and torque can be improved. Although reducing the circumferential width of the inner diameter bridge 35 increases the stress generated in the inner diameter bridge 35, the increase in stress generated in the inner diameter bridge 35 can be suppressed by providing the central bridge 37.

[0016] As shown in Figure 3, the portion of the rotor core 31 on the outer diameter side of the first through hole 42 is referred to as the rotor core outer diameter portion 31a, and the portion on the inner diameter side is referred to as the rotor core inner diameter portion 31b. The central bridge 37 connects the rotor core outer diameter portion 31a and the rotor core inner diameter portion 31b. Therefore, the central bridge 37 has the effect of improving rigidity against radial tensile stress due to centrifugal force. In the rotor of this embodiment, there is a difference between the rigidity against radial tensile stress along the q-axis and the rigidity against radial tensile stress along the d-axis. Therefore, when centrifugal force is applied, the spreading of the outer surface of the rotor core 31 becomes uneven. As a result, bending stress acts on the outer diameter side bridge 36. Furthermore, as the rotor core outer diameter portion 31a deforms outward due to centrifugal force, bending stress also acts on the inner diameter side bridge 35. In the rotor of this embodiment, since the central bridge 37 is provided on the d-axis, the rigidity against tensile stress on the d-axis is improved. Therefore, deformation of the rotor core outer diameter portion 31a can be suppressed. As a result, the bending stress acting on the outer diameter bridge 36 and the inner diameter bridge 35 can be reduced.

[0017] In the rotating electric machine of this embodiment, torque is generated by the interaction between permanent magnets provided on the rotor and the stator. The magnitude of the torque is determined by the sum of the magnitude of the magnet torque and the magnitude of the reluctance torque. The magnitude of the magnet torque is proportional to the magnitude of the magnetic flux of the permanent magnet. The magnitude of the reluctance torque is proportional to the difference between the d-axis inductance and the q-axis inductance generated by the interaction between the magnetic salient poles of the rotor and the rotor. In the rotor of this embodiment, by increasing the radial size of the first through-hole 42, the magnetic resistance of the inner diameter bridge 35 and the central bridge 37 increases, and the magnetic flux of the permanent magnet toward the outer diameter side of the rotor core 31 increases, thus increasing the magnet torque. Furthermore, since it is possible to reduce the d-axis inductance without reducing the q-axis inductance, the reluctance torque can be increased. In this way, the rotor of this embodiment can achieve both improved mechanical strength and improved magnetic performance.

[0018] The effects of the rotor of this embodiment will be explained in more detail with reference to a comparative example. Figure 4 is an enlarged cross-sectional view showing one magnetic pole of the rotor of the comparative example according to this embodiment. As shown in Figure 4, the rotor of the comparative example has a similar configuration to the rotor of this embodiment, but differs in that the first through-hole 42 is not divided into two in the circumferential direction. That is, the rotor of the comparative example does not have a central bridge. For comparison, the sum of the circumferential width of the central bridge 37 and the circumferential widths of the two inner diameter side bridges 35 in the rotor of this embodiment shown in Figure 3 is the same as the sum of the circumferential widths of the two inner diameter side bridges 35 in the rotor of the comparative example shown in Figure 4. Also, the radial length of the first through-hole 42 in the rotor of this embodiment shown in Figure 3 is the same as the radial length of the first through-hole 42 in the rotor of the comparative example shown in Figure 4.

[0019] Figure 5 is a diagram illustrating the characteristics of the rotor according to this embodiment. Figure 5 shows the stress generated by centrifugal force in the outer diameter bridge 36, the inner diameter corner 35a of the inner diameter bridge, and the outer diameter corner 35b of the inner diameter bridge in the rotor of this embodiment shown in Figure 3 and the rotor of the comparative example shown in Figure 4. Here, the inner diameter corner 35a of the inner diameter bridge refers to the corner located on the inner diameter side and circumferentially outward of the inner diameter bridge 35. The outer diameter corner 35b of the inner diameter bridge refers to the corner located on the outer diameter side and circumferentially inward of the inner diameter bridge 35. As can be seen from Figure 5, since the rotor of this embodiment is equipped with a central bridge, the stress generated in the outer diameter bridge and the inner diameter bridge can be reduced compared to the rotor of the comparative example which is not equipped with a central bridge.

[0020] Permanent magnets on a rotor undergo thermal demagnetization when their temperature rises during rotational drive. This thermal demagnetization reduces the magnetic flux of the permanent magnets, which in turn reduces the magnet torque. In the rotor of this embodiment, a coolant can be flowed through the first through-hole 42 to suppress the temperature rise of the permanent magnets. For example, oil can be used as the coolant. In the rotor of this embodiment, a central bridge 37 is provided in the first through-hole 42, which increases the contact area between the coolant and the rotor core 31, thus improving the cooling effect compared to the rotor of the comparative example.

[0021] In the rotor of this embodiment, the first through-hole 42 is divided into two by the central bridge 37. Therefore, when the first through-hole 42 is used as a coolant flow path, one of the first through-holes 42 can be used as the forward path for the coolant, and the other first through-hole 42 can be used as the return path for the coolant. Alternatively, both first through-holes 42 can be used as a flow path in which the coolant flows in the same direction. When both first through-holes 42 are used as a flow path in which the coolant flows in the same direction, the flow path length is shorter and the structure of the end plate is simpler compared to when the first through-holes 42 are used as a reciprocating flow path, so that frictional loss and pressure loss of the coolant within the flow path are reduced.

[0022] When the two divided first through-holes 42 are used as a reciprocating flow path, the flow can be divided into two paths: one through-hole 42 that flows from one end plate to the first through-hole 42 which is the forward path, and another through-hole 42 that flows from the other end plate to the other first through-hole 42 which is the return path, and a third through-hole 42 that sprays coolant onto the stator. Furthermore, the coolant that has returned to one end plate can also be sprayed onto the stator.

[0023] In this embodiment of the rotor, the inner diameter flux barrier and the outer diameter flux barrier are composed of through holes that penetrate the rotor core in the axial direction. Since these flux barriers are provided to prevent magnetic flux leakage from the permanent magnets, it is sufficient that the permeability of the inner diameter flux barrier and the outer diameter flux barrier is smaller than the permeability of the rotor core. Therefore, the inner diameter flux barrier and the outer diameter flux barrier do not necessarily have to be composed of through holes, and these flux barriers may be filled with a material such as resin having a permeability smaller than the permeability of the rotor core. When the inner diameter flux barrier and the outer diameter flux barrier are filled with a material such as resin, deformation of the inner diameter flux barrier and the outer diameter flux barrier due to centrifugal force can be suppressed. As a result, the stress acting on the inner diameter bridge and the outer diameter bridge can be further reduced.

[0024] Embodiment 2. Figure 6 is a cross-sectional view of the rotor according to Embodiment 2. Figure 6 is a cross-sectional view in a direction perpendicular to the axis of rotation. In Figure 6, the axis of rotation is omitted. The rotating electric machine according to this embodiment has the same configuration as the rotating electric machine shown in Figure 1 of Embodiment 1. The rotating electric machine of this embodiment differs from the rotor structure of Embodiment 1 in that the rotor structure is different.

[0025] As shown in Figure 6, the rotor of this embodiment is composed of magnet insertion holes in which one magnetic pole is arranged in two layers, and permanent magnets inserted into each magnet insertion hole. The outer diameter side is referred to as the first layer, and the inner diameter side as the second layer. The rotor core 31 has a pair of first-layer magnet insertion holes 51 with the d-axis in between. The pair of first-layer magnet insertion holes 51 are configured such that the distance between them on the outer diameter side is greater than the distance between them on the inner diameter side. In other words, the pair of first-layer magnet insertion holes 51 are configured to open in a V-shape toward the outer diameter side. First-layer permanent magnets 62 are inserted into each of the pair of first-layer magnet insertion holes 51.

[0026] A pair of second-layer magnet insertion holes 71 are formed in the rotor core 31 on the inner diameter side of the first-layer magnet insertion hole 51, with the d-axis in between. The pair of second-layer magnet insertion holes 71 are configured such that the distance between them on the outer diameter side is greater than the distance between them on the inner diameter side. In other words, the pair of second-layer magnet insertion holes 71 are configured to open in a V-shape toward the outer diameter side. A second-layer permanent magnet 82 is inserted into each of the pair of second-layer magnet insertion holes 71. A first through-hole 72 is formed between the inner diameter sides of the pair of second-layer magnet insertion holes 71. The first through-hole 72 is formed across the d-axis. One magnetic pole is formed by the pair of first-layer magnet insertion holes 51, the first-layer permanent magnets 62 inserted into each of the pair of first-layer magnet insertion holes 51, the pair of second-layer magnet insertion holes 71, the second-layer permanent magnets 82 inserted into each of the pair of second-layer magnet insertion holes 71, and the first through-hole 72. Each magnetic pole is arranged in a circumferential direction. In the rotor of this embodiment shown in Figure 6, there are eight magnetic poles.

[0027] Figure 7 is an enlarged cross-sectional view showing one magnetic pole of the rotor according to this embodiment. A first-layer permanent magnet 62 is inserted in the center of the first-layer magnet insertion hole 51, and both ends of the first-layer permanent magnet 62 in the first-layer magnet insertion hole 51 are hollow. These hollows are provided to prevent magnetic flux leakage from the first-layer permanent magnet 62. The hollow on the inner diameter side of the first-layer magnet insertion hole 51 is referred to as the first-layer inner diameter side flux barrier 53, and the hollow on the outer diameter side is referred to as the first-layer outer diameter side flux barrier 54. The portion sandwiched between the first-layer inner diameter side flux barriers 53 is referred to as the first-layer central bridge 63, and the portion sandwiched between the first-layer outer diameter side flux barrier 54 and the outer circumferential surface of the rotor core 31 is referred to as the first-layer outer diameter side bridge 66.

[0028] A second-layer permanent magnet 82 is inserted in the center of the second-layer magnet insertion hole 71, and both ends of the second-layer permanent magnet 82 in the second-layer magnet insertion hole 71 are hollow. The hollow on the inner diameter side of the second-layer magnet insertion hole 71 is called the second-layer inner diameter side flux barrier 73, and the hollow on the outer diameter side is called the second-layer outer diameter side flux barrier 74. The portion sandwiched between the second-layer inner diameter side flux barrier 73 and the first through hole 72 is called the second-layer inner diameter side bridge 75, and the portion sandwiched between the second-layer outer diameter side flux barrier 74 and the outer circumferential surface of the rotor core 31 is called the second-layer outer diameter side bridge 76. Furthermore, the first through hole 72 is divided into two in the circumferential direction, and the portion that divides the first through hole 72 into two is called the second-layer central bridge 77. The second-layer central bridge 77 is formed on the d-axis. Here, let Lc be the circumferential width of the second layer central bridge 77, and let Ld be the circumferential width of the second layer inner diameter side bridge 75.

[0029] As shown in Figure 7, the first through-hole 72, which is divided by the second layer central bridge 77, is rectangular in shape with a longitudinal direction along the radial direction. The first through-hole 72 reduces the mass of the rotor core 31 and relieves the bending stress acting on the second layer inner diameter bridge 75, the second layer outer diameter bridge 76, and the second layer central bridge 77. The sum of the circumferential widths of the two divided first through-holes 72 is set to be greater than the sum of the circumferential width of the second layer central bridge 77 and the circumferential widths of the two second layer inner diameter bridges 75.

[0030] The radial widths of the first outer diameter bridge 66 and the second outer diameter bridge 76 are preferably as small as possible to improve torque. In the rotor of this embodiment, as shown in Figure 6, the second central bridge 77 is formed in a position that coincides with the d-axis, but the second central bridge may also be configured with multiple bridges arranged symmetrically around the d-axis, and in this case, the multiple bridges do not have to be parallel to the d-axis.

[0031] As shown in Figure 7, the portion of the rotor core 31 on the outer diameter side of the first layer magnet insertion hole 51 is called the rotor core outer diameter portion 31a, the portion on the inner diameter side of the first through hole 72 is called the rotor core inner diameter portion 31b, and the portion between the first layer magnet insertion hole 51 and the first through hole 72 is called the rotor core intermediate portion 31c. Furthermore, the shortest distance between the first layer permanent magnet 62 and the second layer permanent magnet 82 is defined as La, and the shortest distance between the first layer inner diameter side flux barrier 53 and the first through hole 72 is defined as Lb. Increasing the radial length of the first through hole 72 on the outer diameter side reduces Lb, thereby reducing the mass of the rotor core intermediate portion 31c. Therefore, by reducing Lb, the stress generated in the second layer inner diameter side bridge 75, the second layer outer diameter side bridge 76, and the second layer central bridge 77 due to centrifugal force can be reduced. However, reducing Lb decreases the rigidity of the rotor core intermediate portion 31c, which increases the deformation of the rotor core outer diameter portion 31a. As a result, the bending stress generated in the first layer outer diameter bridge 66 increases. By adjusting Lb, it is possible to reduce the stress generated in the second layer inner diameter bridge 75 and the second layer central bridge 77 while setting the stress generated in the first layer outer diameter bridge 66 and the stress generated in the second layer outer diameter bridge 76 to be roughly the same.

[0032] Figure 8 is a diagram illustrating the relationship between the radial length of the first through-hole and the stress generated in the first outer diameter bridge 66 and the second outer diameter bridge 76. In a rotor having a two-layer magnetic pole structure, such as the rotor of this embodiment, the stress generated in the first outer diameter bridge 66 is predominantly due to the radial stiffness along the d-axis. Therefore, in order to reduce the stress generated in the first outer diameter bridge 66, it is preferable to make the first through-hole smaller. On the other hand, the stress generated in the second outer diameter bridge 76 is predominantly due to the mass of the rotor core intermediate portion 31c. Therefore, in order to reduce the stress generated in the second outer diameter bridge 76, it is preferable to make the first through-hole larger. In order to make the stress generated in the first outer diameter bridge 66 and the stress generated in the second outer diameter bridge 76 approximately the same, it is necessary to adjust Lb so that the two characteristic curves shown in Figure 8 intersect.

[0033] The effects of the rotor of this embodiment will be explained in more detail with reference to a comparative example. Figure 9 is an enlarged cross-sectional view showing one magnetic pole of the rotor of the comparative example according to this embodiment. As shown in Figure 9, the rotor of the comparative example has a similar configuration to the rotor of this embodiment, but differs in that the first through-hole 72 is not divided into two in the circumferential direction. That is, the rotor of the comparative example does not have a second-layer central bridge. For comparison, the sum of the circumferential width of the second-layer central bridge 77 and the circumferential widths of the two second-layer inner diameter side bridges 75 in the rotor of this embodiment shown in Figure 7 is the same as the sum of the circumferential widths of the two second-layer inner diameter side bridges 75 in the rotor of the comparative example shown in Figure 9. Also, the radial length of the first through-hole 72 in the rotor of this embodiment shown in Figure 7 is the same as the radial length of the first through-hole 72 in the rotor of the comparative example shown in Figure 9.

[0034] Figure 10 is a diagram illustrating the characteristics of the rotor according to this embodiment. Figure 10 shows the stress generated by centrifugal force at the inner diameter corners 75a and 75b of the first layer outer diameter bridge 66, the second layer outer diameter bridge 76, and the second layer inner diameter bridge 75, respectively, in the rotor of this embodiment shown in Figure 7 and the rotor of the comparative example shown in Figure 9. Here, the inner diameter corner 75a of the second layer inner diameter bridge 75 refers to the corner located on the inner diameter side and circumferentially outward of the second layer inner diameter bridge 75. Also, the outer diameter corner 75b of the second layer inner diameter bridge 75 refers to the corner located on the outer diameter side and circumferentially inward of the second layer inner diameter bridge 75. As can be seen from Figure 10, since the rotor of this embodiment is equipped with a second layer central bridge, the stress generated at the first layer outer diameter bridge 66 and the second layer inner diameter bridge 75 can be reduced compared to the rotor of the comparative example which is not equipped with a second layer central bridge. In this embodiment, the stress generated in the second layer outer diameter bridge 76 is greater than in the comparative example rotor. This is because the circumferential width of the second layer inner diameter bridge in this embodiment is smaller than that of the comparative example rotor. In this embodiment, increasing the circumferential width of the second layer inner diameter bridge slightly increases the mass of the rotor core, but it is possible to reduce the stress generated in the second layer outer diameter bridge 76.

[0035] Figures 11 and 12 are enlarged cross-sectional views showing one magnetic pole of the rotor according to this embodiment. The rotors shown in Figures 11 and 12 are obtained by changing Lc and Ld in the rotor shown in Figure 7. In the rotors shown in Figures 7, 11, and 12, Lc + 2Ld is constant. In the rotor shown in Figure 7, Lc < 2Ld, in the rotor shown in Figure 11, Lc = 2Ld, and in the rotor shown in Figure 12, Lc > 2Ld. Increasing Lc reduces the stress generated in the first layer outer diameter side bridge 66, but the amount of reduction is small. The presence or absence of the second layer central bridge has a greater influence on the stress generated in the first layer outer diameter side bridge 66 than the size of Lc. Furthermore, increasing Lc reduces Ld, which reduces the effect of suppressing deformation of the rotor core outer diameter portion 31a and the rotor core intermediate portion 31c, resulting in large stresses being generated in the inner diameter corner portion 75a and the outer diameter corner portion 75b of the second layer inner diameter side bridge 75.

[0036] Let Y be the average value of the stress generated at the inner diameter corners 75a of the first layer outer diameter bridge 66, the second layer outer diameter bridge 76, the second layer inner diameter bridge 75, and the outer diameter corners 75b of the second layer inner diameter bridge 75, and let Z be its standard deviation. Let X be the sum of Y and Z. The smaller X is, the smaller the stress generated at the stress concentration points of the rotor core, and the smaller the stress imbalance. In addition, in the comparative example rotor without a second layer central bridge shown in Figure 9, let Y be the average value of the stress generated at the inner diameter corners 75a of the two first layer outer diameter bridges 66, the second layer inner diameter bridge 75, and the outer diameter corners 75b of the second layer inner diameter bridge 75, and let Z be its standard deviation. Let W be the sum of Y and Z.

[0037] Figure 13 is a diagram illustrating the characteristics of the rotor according to this embodiment. Figure 13 shows the characteristics of the rotor according to this embodiment when Lc + 2Ld is kept constant and Lc is varied. In Figure 13, the horizontal axis is Lc / (Lc + 2Ld), and the vertical axis is (X - W) / W. In the rotor according to this embodiment, Lc / (Lc + 2Ld) is approximately 0.57 when (X - W) / W = 0. Therefore, by setting Lc in the range where Lc / (Lc + 2Ld) ≤ 0.57, the stress imbalance can be improved compared to the rotor of the comparative example. To further improve the stress imbalance, it is preferable to set Lc / (Lc + 2Ld) as small as possible. Generally, when the rotor core is made of laminated electromagnetic steel sheets, the electromagnetic steel sheets are processed into the shape of the rotor core by punching. In the case of punching, in order to prevent deformation of the punched electromagnetic steel sheets, it is preferable to set the set values ​​of Lc and Ld to values ​​greater than the thickness of the electromagnetic steel sheets.

[0038] Embodiment 3. Figure 14 is a cross-sectional view of the rotor according to Embodiment 3. Figure 14 is a cross-sectional view in a direction perpendicular to the axis of rotation. In Figure 14, the axis of rotation is omitted. The rotating electric machine according to this embodiment has the same configuration as the rotating electric machine shown in Figure 1 of Embodiment 1. The rotating electric machine of this embodiment differs from the rotor structure of Embodiment 1 in that the rotor structure is different.

[0039] As shown in Figure 14, the rotor of this embodiment has a second through-hole 45 added to the structure of the rotor shown in Figure 2 of Embodiment 1. The second through-hole 45 is located on the q-axis and has a structure that is symmetrical with respect to the q-axis. The second through-hole 45 has sides in the radial direction that are parallel to the longitudinal direction of the permanent magnet 32, and the outer diameter side and inner diameter side are connected by smooth, arc-shaped sides.

[0040] Figure 15 is an enlarged cross-sectional view of the rotor of this embodiment, centered on the q-axis. In the rotor of this embodiment, the inner diameter surface of the first through hole 42, the inner diameter surface of the inner diameter flux barrier 43, and the inner diameter surface of the second through hole 45 are arranged at approximately the same distance from the center of rotation. Therefore, the differences in stress generated when the rotating shaft 33 is press-fitted into the rotor core 31 added to the first through hole 42, the inner diameter flux barrier 43, and the second through hole 45, respectively, and the centrifugal force generated when the rotor rotates are reduced.

[0041] In the rotor of this embodiment, the magnitude of the stress generated in the inner diameter bridge 35 and the outer diameter bridge 36 when the second through hole 45 is provided is almost the same as when the second through hole 45 is not provided. Therefore, the rotor of this embodiment, like the rotor of Embodiment 1, can reduce the stress generated in the outer diameter bridge and the inner diameter bridge, and can also be made lighter.

[0042] In the rotor of this embodiment shown in Figure 15, if Ra is the radius of curvature of the inner diameter side of the second through hole 45 and Rb is the radius of curvature of the outer diameter side, it is preferable that Ra < Rb. By setting Ra < Rb, the mass of the rotor core portion on the outer diameter side of the second through hole 45 can be reduced, and the stress generated on the inner diameter side of the second through hole 45 can be reduced.

[0043] Furthermore, in the rotor of this embodiment shown in Figure 15, if Le is the shortest distance between the permanent magnets 32 arranged opposite each other across the q-axis, and Lf is the shortest distance between the permanent magnets 32 and the second through-hole 45, then it is preferable that Le is 2 times or less of Lf. If Le is greater than 2 times Lf, magnetic saturation may occur in the rotor core portion between the permanent magnets 32 and the second through-hole 45, potentially reducing the reluctance torque. The second through-hole 45 can also be used as a flow path for the coolant.

[0044] Embodiment 4. FIG. 16 is an enlarged cross-sectional view of the rotor according to Embodiment 4. FIG. 16 is a cross-sectional view in a direction orthogonal to the rotation axis and is an enlarged cross-sectional view showing one magnetic pole. In the rotor of the present embodiment, the first through-hole 42 is divided into three in the circumferential direction. The central bridge 37 that divides the first through-hole 42 into three in the circumferential direction is formed in two positions that are line-symmetric about the d-axis rather than on the d-axis.

[0045] In the rotor of the present embodiment, the center-of-gravity positions of the outer-diameter portion 31a of the rotor core and the permanent magnet 32 for a half-pole are set as point G. The central bridge 37 formed at a position included in the half-pole is arranged on a straight line connecting point G and the rotation center. By arranging the central bridge 37 at such a position, it becomes possible to suppress deformation of the outer peripheral surface of the rotor core due to centrifugal force, and to reduce the bending stress generated in the outer-diameter-side bridge 36.

[0046] Embodiment 5. FIG. 17 is an enlarged cross-sectional view of the rotor according to Embodiment 5. FIG. 17 is a cross-sectional view in a direction orthogonal to the rotation axis and is an enlarged cross-sectional view showing one magnetic pole. In the rotor of the present embodiment, the interval between the two inner-diameter-side flux barriers 43 is formed to become narrower toward the inner diameter side. Accordingly, the first through-hole 42 is also formed in a shape that becomes narrower toward the inner diameter side. The first through-hole 42 is divided into two in the circumferential direction by a central bridge 37 formed on the d-axis. The first through-hole 42 divided into two has a substantially triangular shape.

[0047] In the rotor configured as described above, the interval between the two inner-diameter-side bridges 35 becomes narrower toward the inner diameter side. Therefore, the centrifugal force generated in the outer-diameter portion 31a of the rotor core is difficult to be transmitted to the inner-diameter portion 31b of the rotor core, and the spread of the inner-diameter portion 31b of the rotor core becomes small, so that a decrease in the pressure generated on the fitting surface between the rotor core and the rotation axis can be suppressed. Therefore, it becomes possible to design the interference between the rotor core and the rotation axis to be small. As a result, the stress generated when the rotation axis is press-fitted into the rotor core can be reduced.

[0048] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable to embodiments alone or in various combinations. Therefore, numerous variations not illustrated are envisioned within the scope of the technology disclosed in this specification. For example, it shall be included when at least one component is modified, added, or omitted, and further, when at least one component is extracted and combined with components of other embodiments.

[0049] 1 Rotating electric machine, 10 Housing, 11 Bearing, 12 Rotation center, 20 Stator, 21 Stator core, 22 Coil, 30 Rotor, 31 Rotor core, 31a Rotor core outer diameter portion, 31b Rotor core inner diameter portion, 31c Rotor core intermediate portion, 32 Permanent magnet, 33 Rotation shaft, 34 End plate, 35 Inner diameter side bridge, 36 Outer diameter side bridge, 37 Central bridge, 41 Magnet insertion hole, 42 First through hole, 43 Inner diameter side flux barrier, 44 Outer diameter side flux barrier, 45 Second through hole, 51 First layer magnet insertion hole, 53 First layer inner diameter side flux barrier, 54 First layer outer diameter side flux barrier, 62 First layer permanent magnet, 63 First layer central bridge, 66 First layer outer diameter side bridge, 71 Second layer magnet insertion hole, 72 First through hole, 73 Second layer inner diameter side flux barrier, 74 Second layer outer diameter side flux barrier, 75 Second layer inner diameter side bridge, 76 Second layer outer diameter side bridge, 77 Second layer central bridge, 82 Second layer permanent magnet.

Claims

1. A rotor having a plurality of magnetic poles arranged circumferentially, each pole being composed of a pair of magnet insertion holes provided in an annular rotor core and a pair of permanent magnets inserted into each of the pair of magnet insertion holes, wherein the pair of magnet insertion holes are provided with a d-axis in between, the distance between the pair of magnet insertion holes on the inner diameter side is narrower than the distance between them on the outer diameter side, each of the magnet insertion holes has an inner diameter side flux barrier and an outer diameter side flux barrier on both sides in the longitudinal direction of the permanent magnet, a first through hole is formed between the pair of magnet insertion holes crossing the d-axis, and the rotor core has an inner diameter side bridge formed between the inner diameter side flux barrier and the first through hole, and at least one central bridge that divides the first through hole in the circumferential direction.

2. The rotor according to claim 1, characterized in that the first through hole divided by the central bridge is rectangular in shape with a longitudinal direction in the radial direction.

3. The rotor according to claim 1 or 2, wherein a second through-hole is formed between adjacent magnetic poles in the circumferential direction, and the second through-hole is composed of a straight edge parallel to the longitudinal direction of the permanent magnet and a curved edge smoothly connecting the straight edge on the inner diameter side.

4. The rotor according to claim 3, characterized in that the shortest distance between the permanent magnet of the magnetic pole and the permanent magnet of another magnetic pole adjacent in the circumferential direction is no more than twice the shortest distance between the permanent magnet and the second through hole.

5. The rotor according to any one of claims 1 to 4, characterized in that when the circumferential width of the central bridge is Lc and the circumferential width of the inner diameter side flux barrier is Ld, Lc / (Lc + 2Ld) ≤ 0.

57.

6. The rotor according to claim 5, characterized in that the sum of the circumferential widths of the first through holes divided in the circumferential direction is greater than Lc + 2Ld.

7. The rotor core is constructed by laminating electrical steel sheets, and the radial width of the outer diameter bridge formed between the outer diameter flux barrier and the outer peripheral surface of the rotor core is greater than the thickness of the electrical steel sheet and smaller than the circumferential width of the inner diameter bridge, as described in any one of claims 1 to 6.

8. The rotor according to any one of claims 1 to 7, characterized in that the pair of magnet insertion holes are formed in two layers in the radial direction, with the outer diameter layer being the first layer and the inner diameter layer being the second layer, and the first through hole is formed only between the inner diameter side flux barriers of the pair of magnet insertion holes in the second layer.

9. The rotor according to claim 8, characterized in that, at one magnetic pole, the shortest distance between the first layer permanent magnet and the second layer permanent magnet is greater than the shortest distance between the inner diameter side flux barrier of the first layer and the first through hole.

10. The rotor according to any one of claims 1 to 9, characterized in that at least one of the inner diameter side flux barrier and the outer diameter side flux barrier is filled with resin.

11. A rotating electric machine comprising a stator having an annular stator core and coils wound around the stator core, and a rotor according to any one of claims 1 to 10, which is arranged coaxially with the stator core via a gap.

12. The rotating electric machine according to claim 11, characterized in that the first through-hole is used as a flow path for a cooling liquid.

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