Rotor, rotating electrical machine, and electric drive system

Abstract

Provided is a rotor for a rotating electrical machine, said rotor being provided with a rotor core in which a plurality of permanent magnets are disposed in the circumferential direction, a rotation shaft which supports the rotor core, and a refrigerant flow passage which is for cooling the permanent magnets, wherein the refrigerant flow passage comprises: a plurality of axial flow passages which are formed in the vicinity of the permanent magnets and on both sides of the magnetic pole central axis of each magnetic pole of the rotor core and which extend in the axial direction of the rotation shaft; a radial flow passage which extends from the rotation shaft side in the radial direction; and a plurality of branch flow passages which branch from the radial flow passage and which are connected to the plurality of axial flow passages.

Description

Rotor, rotating electric machine and electric drive system

[0001] The present invention relates to a rotor, a rotating electric machine, and an electric drive system.

[0002] In rotating electric machines with permanent magnets in the rotor, magnet loss causes the magnet temperature to rise. Higher permanent magnet temperatures can cause irreversible demagnetization, potentially resulting in a decline in motor performance. For this reason, a cooling system using a refrigerant passage in the rotor is often used (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 2012-210120

[0004] However, because magnet loss during rotor rotation varies depending on the circumferential position of the permanent magnet, magnet temperature tends to become non-uniform in the circumferential direction. Because the continuous rated output of a rotating electric machine is limited by the maximum magnet temperature, temperature non-uniformity leads to a decrease in the continuous rated output.

[0005] A rotor according to one aspect of the present invention is a rotor for a rotating electric machine comprising a rotor core in which a plurality of permanent magnets are arranged circumferentially, a rotating shaft supporting the rotor core, and a refrigerant flow path for cooling the permanent magnets, wherein the refrigerant flow path is formed in the vicinity of the permanent magnets and on both sides of the magnetic pole center axis of each magnetic pole of the rotor core, and comprises a plurality of axial flow paths extending in the axial direction of the rotating shaft, a radial flow path extending radially from the rotating shaft side, and a plurality of branch flow paths branching from the radial flow paths and connecting to the plurality of axial flow paths.

[0006] According to the present invention, the magnet temperature can be made uniform and the maximum magnet temperature can be reduced.

[0007] 1 is a diagram showing a schematic configuration of an electric vehicle; 2 is a cross-sectional view showing a main part of an electric drive system; 3 is a diagram explaining a path of cooling oil in a rotating electric machine; 4 is a diagram showing an axial end face of a rotor core; 5 is a diagram showing the rotor core side surface of an end plate; 6 is a diagram explaining uneven magnet temperature due to imbalance in magnet loss; 7 is a diagram explaining how refrigerant flows when the rotor rotation direction is counterclockwise; 8 is a diagram explaining how refrigerant flows when the rotor rotation direction is clockwise; 9 is a diagram showing modified example 1; 10 is a diagram explaining modified example 2, showing the load side end face of the rotor core; 11 is a diagram explaining modified example 2, showing the rotor core facing surface of the end plate; and 12 is a diagram showing modified example 3.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. Furthermore, in the following description, identical or similar elements and processes are given the same reference numerals, and duplicate explanations may be omitted. Note that the content described below merely shows an example of an embodiment of the present invention, and the present invention is not limited to the following embodiment, and can be implemented in various other forms.

[0009] 1 is a diagram showing a schematic configuration of an electric vehicle to which a rotating electric machine according to this embodiment is applied. The electric vehicle 1 is equipped with an electric drive system 3 for driving wheels 2. The electric drive system 3 is a vehicle drive unit including a rotating electric machine, an inverter, and other devices.

[0010] The cooling oil, which is the refrigerant of the cooling system 7 of the electric drive system 3, is cooled by the oil cooler 4. In this embodiment, cooling oil is used as the refrigerant of the cooling system 7, but the refrigerant is not limited to cooling oil. In the oil cooler 4, heat is exchanged between the refrigerant (cooling water) of the cooling system 5 of the electric vehicle 1 and the cooling oil of the cooling system 7, and the cooling oil is cooled by the cooling water. The heat of the cooling water of the cooling system 5 is finally released to the outside of the vehicle by the chiller 6.

[0011] FIG. 2 is a cross-sectional view showing a main part of the electric drive system 3. The electric drive system 3 includes a rotating electric machine 10 and a reducer 20 that transmits the driving force of the rotating electric machine 10. The electric drive system 3 may also include an inverter in addition to the above components. In FIG. 2 , as indicated by the arrows, the side to which the electric drive system 3 transmits the driving force is defined as the "load side," and the opposite side is defined as the "anti-load side." The upward direction in the figure is defined as the "upper" or "upper side," and the downward direction in the figure is defined as the "lower" or "lower side." The direction along the rotor shaft 112 of the rotating electric machine 10 is defined as the "axial direction," the circumference of the rotor shaft 112 is defined as the "circumferential direction," and the radial direction (radial direction) about the axis of the rotor shaft 112 is defined as the "radial direction."

[0012] The rotating electric machine 10 includes a rotor 11 and a stator 12 disposed on the outer diameter side of the rotor 11. The rotor 11 and the stator 12 are housed in a housing 13. Cooling oil outlets 130a and 130b are formed in the lower part of the housing 13. The stator 12 is composed of a stator core 121 and a stator coil 122. A plurality of slots are formed in the stator core 121, and the stator coil 122 is inserted into the slots. The rotor 11 and the stator 12 may be skewed.

[0013] The rotor 11 includes a rotor core 110, end plates 111A and 111B, a rotor shaft 112, and permanent magnets 113. The rotor shaft 112 is rotatably supported by bearings 14a, 14b, and 14c. The rotor core 110 and the stator core 121 are formed by laminating electromagnetic steel sheets. The end plates 111A and 111B are arranged to contact the axial end faces of the rotor core 110.

[0014] The reducer 20 includes a drive gear 21 and a driven gear 22. The drive gear 21, which is provided on the load side of the rotor shaft 112, meshes with the driven gear 22, which is provided on a driven gear shaft 23. The driven gear shaft 23 is rotatably supported by bearings 14d and 14e. The rotational driving force of the rotor shaft 112 is transmitted to the driven gear shaft 23 via the drive gear 21 and the driven gear 22.

[0015] FIG. 3 is a diagram illustrating the cooling oil path in the rotating electric machine 10. In FIG. 3, dashed arrows indicate the cooling oil path. A refrigerant flow path 112a extending in the shaft axial direction is formed at the axial center of the rotor shaft 112. As will be described in detail later, grooves for forming the refrigerant flow path are formed on the rotor core-facing surfaces of the end plates 111A and 111B. The end plates 111A and 111B are arranged so as to contact the end faces of the rotor core 110, thereby forming a refrigerant flow path between the rotor core end face and the end plates 111A and 111B. In addition, the rotor core 110 is formed with holes that penetrate from one end face to the other end face of the rotor core 110 as refrigerant flow paths (hereinafter referred to as axial flow paths).

[0016] The cooling oil cooled by the oil cooler 4 is supplied to the refrigerant flow path 112a of the rotor shaft 112. The cooling oil in the refrigerant flow path 112a flows radially through the refrigerant flow path formed between the rotor core 110 and the end plate 111A and then flows into the refrigerant flow path (axial flow path) of the rotor core 110. The cooling oil that flows into the axial flow path of the rotor core 110 flows toward the opposite rotor core end face, then flows through the refrigerant flow path formed between the opposite end face and the end plate 111B, and is discharged toward the anti-load side (right side in the figure) coil end of the stator coil 122. The cooling oil that flows from the refrigerant flow path 112a into the refrigerant flow path formed between the rotor core 110 and the end plate 111B also flows as indicated by the dashed arrow and is discharged toward the load side (left side in the figure) coil end of the stator coil 122.

[0017] The cooling oil accumulated in the housing 13 is discharged from the housing through the cooling oil outlets 130a and 130b and falls into the oil pan 70 disposed below the rotating electrical machine 10. The cooling oil in the oil pan 70 is transferred to the oil cooler 4 by the oil pump 71 and circulates through the cooling system 7.

[0018] Next, the flow paths formed in the rotor 11 will be described. FIG. 4 is a diagram showing the axial end face of the rotor core 110. FIG. 4 shows the load-side end face of the rotor core 110 and the rotor shaft 112, with the rotor shaft 112 shown in cross section at the rotor core end face position. The permanent magnet 113 shown in FIG. 2 is composed of three divided magnets M1, M2, and M3 as shown in FIG. 4. One magnetic pole is formed by one set of divided magnets M1, M2, and M3. In FIG. 4, eight sets of divided magnets M1, M2, and M3 are provided, with four north poles and four south poles arranged alternately in the circumferential direction. Therefore, the circumferential spacing around the q axis is an angle θ1 = 45 degrees, and the angle θ2 between the magnetic pole center axis J1 and the q axis is 22.5 degrees. The divided magnet M2 is arranged on the magnetic pole center axis J1, and the divided magnets M1 and M3 are arranged symmetrically with respect to the magnetic pole center axis J1.

[0019] Axial flow passages 301a and 301b are formed at positions of radius r near the split magnets M1 and M3, penetrating the rotor core 110 in the axial direction. In the example shown in Fig. 4, the axial flow passages 301a and 301b are arranged symmetrically with respect to the magnetic pole center axis J1, and are arranged at an angle θ3 from the magnetic pole center axis J1. In addition, multiple refrigerant flow passages 112b are formed radially in the rotor shaft 112, penetrating from the inner circumferential surface of the axial refrigerant flow passage 112a to the outer circumferential surface of the shaft. Each refrigerant flow passage 112b is formed along the magnetic pole center axis J1.

[0020] 5 is a diagram showing the rotor core-side surfaces of the end plates 111A and 111B. The end plates 111A and 111B have the same shape. When the end plates 111A and 111B are arranged on the end surfaces of the rotor core 110, they are arranged with a circumferential phase difference of 180 degrees. The end plate 111A will be described below.

[0021] End plate 111A has grooves that form refrigerant flow paths corresponding to the eight magnetic poles of rotor core 110. When end plate 111A is placed on the end face of rotor core 110, a flow path is formed that is surrounded by the grooves in end plate 111A and the end face of rotor core 110. Hereinafter, the grooves in end plate 111A will be referred to as flow paths.

[0022] In the upper 180-degree range of the end plate 111A shown in the figure, four groups of flow channels (400, 401a, 401b) are formed at intervals of an angle θ1 (=45 degrees), while in the lower 180-degree range shown in the figure, four groups of flow channels (402a, 402b) are formed at intervals of an angle θ1.

[0023] Each flow path group (400, 401a, 401b) is composed of a radial flow path 400 extending in the radial direction and two branch flow paths 401a, 401b branching in a Y shape from the outer circumferential end of the radial flow path 400. The inner circumferential end of the radial flow path 400 is connected to a refrigerant flow path 112b (see FIG. 4) formed in the rotor shaft 112. The branch flow path 401a extends to a position of radius r, and its tip region faces the axial flow path 301a (see FIG. 4) of the rotor core 110. The tip region of the branch flow path 401b faces the axial flow path 301b (see FIG. 4) of the rotor core 110. In other words, the branch flow path 401a is connected to the axial flow path 301a, and the branch flow path 401b is connected to the axial flow path 301b.

[0024] On the other hand, the flow passage group (402a, 402b) formed within a 180-degree range on the lower side of the figure is composed of two radial flow passages 402a, 402b extending from the radius r to the outer periphery. Each radial flow passage 402a, 402b is disposed symmetrically with respect to the magnetic pole center axis J1 and forms an angle θ3 with respect to the magnetic pole center axis J1. The inner peripheral end region of the radial flow passage 402a faces the axial flow passage 301a (see FIG. 4) of the rotor core 110. Similarly, the inner peripheral end region of the radial flow passage 402b faces the axial flow passage 301b (see FIG. 4) of the rotor core 110. That is, the radial flow passage 402a communicates with the axial flow passage 301a, and the radial flow passage 402b communicates with the axial flow passage 301b.

[0025] In Fig. 4, the refrigerant in the refrigerant flow path 112a of the rotor shaft 112 flows through the refrigerant flow path 112b and into the radial flow paths 400 in the end plates 111A and 111B shown in Fig. 5. The refrigerant flowing in the radial flow path 400 in the outer circumferential direction flows into the branch flow paths 401a and 401b, and then flows from the branch flow path 401a into the axial flow path 301a and from the branch flow path 401b into the axial flow path 301b. The refrigerant flowing from the branch flow paths 401a and 401b in the end plate 111A into the axial flow paths 301a and 301b flows toward the anti-load side and into the radial flow paths 402a and 402b in the end plate 111B. On the other hand, the refrigerant that flows from the branch flow paths 401 a, 401 b in the end plate 111B into the axial flow paths 301 a, 301 b flows toward the load side and into the radial flow paths 402 a, 402 b in the end plate 111 A. The refrigerant that flows into the radial flow paths 402 a, 402 b in the end plates 111 A, 111 B flows in the radial flow paths 402 a, 402 b in the outer circumferential direction and is discharged from the end plates 111 A, 111 B toward the coil ends.

[0026] Fig. 6 is a diagram qualitatively illustrating non-uniform magnet temperatures due to imbalance in magnet losses. While Fig. 6 uses an SPM (Surface Permanent Magnet) motor as an example, the diagram is similarly applicable to an IPM (Interior Permanent Magnet) motor in the embodiments. The diagram illustrates a case in which a rotor 91 rotates counterclockwise (in the direction of the thick arrow) relative to a stator 90. A solid line 92 with an arrow indicates the magnetic flux of a permanent magnet provided in the rotor 91, and a dashed line 93 with an arrow indicates the magnetic flux due to the q-axis current.

[0027] The magnetic flux density of the combined magnetic flux of the magnetic flux 92 from the permanent magnet and the magnetic flux 93 from the q-axis current is such that in tooth A, which is close to the leading side of the magnetic pole (N pole), the direction of both magnetic fluxes is the same and they reinforce each other. As a result, the magnetic flux density in tooth A becomes large and approaches saturation, and the magnetic permeability in tooth A becomes small. On the other hand, in tooth B, which is close to the lagging side of the magnetic pole (N pole), the direction of both magnetic fluxes is opposite and they weaken each other. As a result, the magnetic flux density in tooth B becomes small and there is a margin for saturation, and the magnetic permeability in tooth B remains high.

[0028] As a result, eddy currents generated by changes in magnetic flux density are larger on the rotation-delayed side, resulting in a greater temperature rise. Thus, magnet loss varies depending on the circumferential position of the permanent magnet, resulting in uneven magnet temperature. Because the continuous rated output of the electric drive system 3 is limited by the maximum magnet temperature, uneven temperature results in a decrease in the continuous rated output. Therefore, in this embodiment, as shown in FIG. 5 , flow paths 400, 401a, and 401b through which refrigerant flows are provided to further cool the high-temperature regions of the permanent magnets (segment magnets M1, M2, and M3), thereby suppressing temperature unevenness among the segment magnets M1, M2, and M3 and achieving lower temperatures.

[0029] 7A and 7B are diagrams illustrating refrigerant flow depending on the rotor rotation direction. Fig. 7A shows the case where the rotor rotation direction is counterclockwise (left direction R1), and Fig. 7B shows the case where the rotor rotation direction is clockwise (right direction R2). Figs. 7A and 7B show the load-side end face of rotor core 110 and flow paths 400, 401a, and 401b, and flow paths 400, 401a, and 401b formed by the load-side end face of rotor 110 and the groove in end plate 111A are indicated by two-dot chain lines.

[0030] The flow of refrigerant through flow paths 400, 401a, and 401b in rotating rotor core 110 will be described below. In the following, a coordinate system (rotating coordinate system) fixed to rotating rotor core 110 will be considered. If the angular velocity vector of rotating rotor core 110 is ω, the equation of motion of a mass point of mass m in the rotating coordinate system is expressed by the following equation (1). In equation (1), α is the acceleration vector of the mass point, F is the external force vector acting on the mass point, v is the velocity vector of the mass point, r is the position vector of the mass point, and ρ is the radial position vector of the mass point. mα=F-2mω×v-m(dω / dt)×r+mω ２ ρ … (1)

[0031] When the angular velocity vector ω is constant, the apparent force generated by rotor rotation is the Coriolis force in the second term on the right-hand side of equation (1) and the centrifugal force in the fourth term on the right-hand side. Figure 7A shows the case where rotor core 110 rotates counterclockwise (in the direction of arrow R1), and the refrigerant flows in the radial flow passages 400 toward the outer periphery as indicated by the dashed arrows. Since centrifugal force is a radial force, it is a force in the same direction as the velocity vector v of the refrigerant flowing in the radial flow passages 400 toward the outer periphery. On the other hand, the Coriolis force Fc in the second term on the right-hand side is a force that is directed in the opposite direction to the rotation direction.

[0032] That is, the refrigerant flowing through the radial flow passages 400 tends to bend toward the circumferential rotation delay side (clockwise direction) due to the Coriolis force Fc, which depends on the velocity vector (flow velocity) v. The same is true for the case of Figure 7B, in which the rotation direction is clockwise (the direction of arrow R2), and the refrigerant flowing through the radial flow passages 400 tends to bend toward the circumferential rotation delay side (counterclockwise direction).

[0033] 7A and 7B, in this embodiment, a radial flow passage 400 formed along the magnetic pole central axis J1 branches into two branch flow passages 401a and 401b at its tip. In the case of Fig. 7A, the branch flow passage 401a branches off to the leading rotation side in the circumferential direction with respect to the magnetic pole central axis J1 and communicates with the axial flow passage 301a arranged on the leading rotation side. The branch flow passage 401b branches off to the lagging rotation side in the circumferential direction with respect to the magnetic pole central axis J1 and communicates with the axial flow passage 301b arranged on the lagging rotation side.

[0034] In the case of Figure 7A, the refrigerant flowing radially through the radial flow passage 400 is subjected to a Coriolis force Fc in the direction of the rotation delay side, which causes the refrigerant to more easily flow into the branch flow passage 401b than into the branch flow passage 401a. As a result, the refrigerant flow rates Q1 and Q2 in the branch flow passages 401a and 401b are biased, with Q2 > Q1. Naturally, the refrigerant flow rate Q2 in the axial flow passage 301b is greater than the refrigerant flow rate Q1 in the axial flow passage 301a (Q2 > Q1). As mentioned above, the temperature rise of the divided magnets M1, M2, and M3 is greater on the rotation delay side, but the cooling capacity of the refrigerant is greater on the rotation delay side (Q2 > Q1). Therefore, the temperature rise of the divided magnets M1, M2, and M3 is efficiently suppressed, resulting in uniform temperatures and a reduction in the maximum magnet temperature.

[0035] Similarly, in the case of Figure 7B where the rotor rotation direction is clockwise R2, the Coriolis force Fc acting toward the rotation-delayed side is directed in the opposite direction to that in Figure 7A relative to the refrigerant flowing radially through the radial flow passage 400 toward the outer periphery. Therefore, the refrigerant is more likely to flow into the branch flow passage 401a on the rotation-delayed side. As a result, the refrigerant flow rates Q1 and Q2 in the axial flow passages 301a and 301b are such that Q1 > Q2. In other words, the temperature rise of the divided magnets M1, M2, and M3 is greater on the rotation-delayed side, but the cooling capacity of the refrigerant is greater on the rotation-delayed side (Q1 > Q2). Therefore, the temperature rise of the divided magnets M1, M2, and M3 is efficiently suppressed, resulting in uniform temperatures and a reduction in the maximum magnet temperature.

[0036] As described above, in this embodiment, regardless of whether the rotor 11 is rotating forward or backward, the temperature rise of the divided magnets M1, M2, and M3 is efficiently suppressed, the temperatures are uniformed, and the maximum magnet temperature can be reduced. As described above, the refrigerant flow rate in the branch flow paths 401a and 401b is biased depending on the rotor rotation. Therefore, it is preferable to set the flow path cross-sectional area S2 (see FIG. 7A) of the branch flow paths 401a and 401b larger than the flow path cross-sectional area S1 (see FIG. 7A) of the radial flow path 400. By setting the flow path cross-sectional areas S1 and S2 in this manner, the refrigerant can flow smoothly from the radial flow path 400 to the branch flow paths 401a and 401b.

[0037] (Variation 1) Fig. 8 is a diagram showing Variation 1 of the above-described embodiment. Fig. 8 shows the space between adjacent q-axes on the load-side end face of rotor core 110, and corresponding flow paths 400, 401a, and 401b. Flow paths 400, 401a, and 401b are indicated by two-dot chain lines, as in Figs. 7A and 7B.

[0038] In Variation 1, six divided magnets M1 to M6 are provided in each magnetic pole. Note that FIG. 8 illustrates only one magnetic pole; the other magnetic poles have a similar configuration. The six divided magnets M1 to M6 are composed of divided magnets M1 to M3 on the outer periphery and divided magnets M4 to M6 on the inner periphery, and are arranged in two layers, one inside and one outside. In this case, axial flow passages 301a and 301b formed in the rotor core 110 are arranged between the divided magnets M1 to M3 on the outer periphery and the divided magnets M4 to M6 on the inner periphery. This arrangement improves the cooling performance on the rotation delay side for the divided magnets M4 to M6 on the inner periphery, just as with the divided magnets M1 to M3 on the outer periphery. This also allows for a more uniform circumferential magnet temperature distribution for both the divided magnets M1 to M3 on the outer periphery and the divided magnets M4 to M6 on the inner periphery.

[0039] 9 and 10 are diagrams illustrating a second modification of the above-described embodiment. Fig. 9 is a diagram showing the load-side end face of rotor core 110. The end face on the non-load side has the same shape as the load side. In the second modification, rotor core 110 is formed with radial flow paths 303 and branch flow paths 304a and 304b in addition to axial flow paths 301a and 301b.

[0040] The radial flow passage 303 is connected to the refrigerant flow passage 112b of the rotor shaft 112 on the inner circumferential side of the rotor core. The branch flow passages 304a and 304b branch off in a Y shape from the outer circumferential end of the radial flow passage 303. The tip region of the branch flow passage 304a is connected to the axial flow passage 301a. The tip region of the branch flow passage 304b is connected to the axial flow passage 301b.

[0041] The shapes of the radial flow passages 303 and the branch flow passages 304a, 304b are set to be the same as the shapes of the radial flow passages 400 and the branch flow passages 401a, 401b in the embodiment. Moreover, the radial flow passages 303 and the branch flow passages 304a, 304b are formed at the same axial position of the rotor core 110. When taking into consideration the balance of the flow rates of the refrigerant flowing on the load side and the anti-load side in the axial flow passages 301a, 301b, it is preferable to dispose the radial flow passages 303 and the branch flow passages 304a, 304b at central positions in the axial direction.

[0042] Fig. 10 is a diagram showing the rotor core-facing surface of end plate 111A. End plate 111B, which is arranged on the anti-load side, has the same shape as end plate 111A shown in Fig. 10. In end plates 111A and 111B in Modification 2, radial flow passages 402a and 402b are arranged over the entire 360-degree range. That is, eight sets of radial flow passages 402a and 402b are formed corresponding to the eight sets of axial flow passages 301a and 301b formed in rotor core 110 shown in Fig. 9.

[0043] Part of the refrigerant that flows into the axial flow passages 301a, 301b of the rotor core 110 in FIG. 9 flows toward the load side, and the rest flows toward the anti-load side. As a result, the segmented magnets M1 to M3 are indirectly cooled by the refrigerant. The refrigerant that flows toward the load side in each axial flow passage 301a, 301b flows into the corresponding radial flow passages 402a, 402b in the end plate 111A. Meanwhile, the refrigerant that flows toward the anti-load side in each axial flow passage 301a, 301b flows into the corresponding radial flow passages 402a, 402b in the end plate 111B. The refrigerant that flows into the radial flow passages 402a, 402b in each end plate 111A, 111B flows toward the outer periphery within the radial flow passages 402a, 402b and, as shown in FIG. 3, flows out toward the coil ends of the stator coil 122 provided in the stator core 121. As a result, the coil ends of the stator coil 122 are cooled by the refrigerant.

[0044] In Modification 2, radial flow passages 303 and branch flow passages 304a, 304b are formed inside rotor core 110, and the same effects as those of the above-described embodiment are achieved. That is, regardless of whether rotor core 110 rotates forward or backward, the refrigerant flow rate is greater in the branch flow passages on the rotation-lag side than in the rotation-lead side. Forming flow passages 303, 304a, 304b inside rotor core 110 may increase magnetic resistance, potentially adversely affecting the motor's electrical performance. Therefore, it is preferable to form flow passages 400, 401a, 401b by forming grooves in end plates 111A, 111B, as in the embodiment.

[0045] (Variation 3) Figure 11 shows a third variation of the above-described embodiment. Segmented magnets M1 to M3 are arranged in magnet holes formed in rotor core 110. The permanent magnets provided in rotor core 110 are magnetized so that the outer periphery of the core has a north or south pole and the inner periphery has the opposite pole. With this magnet arrangement, short-circuiting of the magnetic flux is likely to occur at the circumferential ends of the magnets. For this reason, gaps called flux barriers are formed in the magnet holes to prevent short-circuiting of the magnetic flux.

[0046] Generally, flux barriers are formed on both circumferential ends of a permanent magnet. In Figure 11, flux barrier 501a is formed on the q-axis side of divided magnet M1, and flux barrier 501b is formed on the q-axis side of divided magnet M3. Flux barrier 501a is connected to the magnet hole that houses divided magnet M1, and flux barrier 501b is connected to the magnet hole that houses divided magnet M3.

[0047] The flux barriers 501a and 501b are holes that axially penetrate the rotor core 110, and in Modification 3, these flux barriers 501a and 501b are used instead of the above-described axial flow paths 301a and 301b. As shown in Fig. 11 , in the end plate 111A, the branch flow path 401a branching from the radial flow path 400 is formed so that its tip region faces the flux barrier 501a. On the other hand, the tip region of the branch flow path 401b is formed so that it faces the flux barrier 501b. In other words, the branch flow path 401a communicates with the flux barrier 501a, and the branch flow path 401b communicates with the flux barrier 501b.

[0048] In the third modification, the flux barriers 501a and 501b that have been provided in the prior art are also used as coolant flow paths, eliminating the need to form additional axial flow paths 301a and 301b. This reduces costs. Furthermore, since there is no need to provide separate axial flow paths 301a and 301b, which would increase magnetic resistance, it is possible to prevent a decrease in the electrical performance of the motor due to increased magnetic resistance.

[0049] According to the embodiment and modified examples of the present invention described above, the following advantageous effects are achieved.

[0050] (C1) As shown in Figures 4, 5, 7A, 7B, etc., a rotor (rotor 11) of a rotating electric machine 10 includes a rotor core (rotor core 110) in which a plurality of permanent magnets (segmented magnets M1 to M3) are arranged in the circumferential direction, a rotating shaft (rotor shaft 112) that supports the rotor core 110, and refrigerant flow paths (301a, 301b, 400, 401a, 401b) for cooling the segmented magnets M1 to M3, 1b, 400, 401a, 401b) are formed near the divided magnets M1 to M3 and on both sides of the magnetic pole center axis J1 of each magnetic pole of the rotor core 110, and are provided with a plurality of axial flow paths 301a, 301b extending in the axial direction of the rotor shaft 112, a radial flow path 400 extending radially from the rotating shaft side, and a plurality of branch flow paths 401a, 401b branching from the radial flow path 400 and connecting to the plurality of axial flow paths 301a, 301b.

[0051] As rotor core 110 rotates, magnet loss increases toward the rotation-delayed side of split magnets M1, M2, and M3, resulting in a greater temperature rise toward the rotation-delayed side. However, as described above, multiple axial flow passages 301 a, 301 b are formed on both sides of magnetic pole center axis J1, and branch flow passages 401 a, 401 b branched from radial flow passage 400 are connected to axial flow passages 301 a, 301 b. This allows more refrigerant to flow through the branch flow passages and axial flow passages located on the rotation-delayed side. As a result, in both forward and reverse rotation states, the temperature rise due to magnet loss is suppressed toward the rotation-delayed side, resulting in a more uniform circumferential magnet temperature distribution and a reduced maximum magnet temperature.

[0052] (C2) In (C1) above, as shown in Figures 4, 5, etc., the rotor 11 has end plates 111A, 111B arranged on the axial end face of the rotor core 110, and the end plate 111A has, on the surface facing the axial end face of the rotor core 110, a radial groove (400) extending radially and a plurality of branch grooves (401a, 401b) branching off from the radial groove (400), and the radial groove and the plurality of branch grooves and the axial end face of the rotor core 110 form a radial flow path 400 and a plurality of branch flow paths 401a, 401b.

[0053] As described above, the flow paths 400, 401a, 401b are formed by the grooves formed in the end plate 111A and the axial end face of the rotor core 110, so the flow paths 400, 401a, 401b can be formed without interfering with the magnetic circuit of the rotor 11. As a result, it is possible to suppress a decrease in the electrical performance of the motor due to the formation of the flow paths.

[0054] (C3) In (C1) above, as shown in Fig. 7A, the flow path cross-sectional area S2 of the branch flow paths 401a, 401b is set to be larger than the flow path cross-sectional area S1 of the radial flow path 400. Therefore, even if the refrigerant flow rate into the branch flow paths 401a, 401b is uneven due to rotor rotation, the refrigerant can flow smoothly from the radial flow path 400 into the branch flow paths 401a, 401b without stagnation.

[0055] (C4) In (C1) above, as shown in Figures 4 and 5, the circumferential position of the radial flow passage 400 is set so as to be included in the circumferential range (angle 2·θ3) in which the multiple axial flow passages 301a, 301b are arranged. By setting it in this manner, one of the branch flow passages 401a, 401b extends from the radial flow passage 400 to the leading rotation side, and the other extends from the radial flow passage 400 to the lagging rotation side. This reduces the difference in the bias of the refrigerant flow rate to the lagging rotation side during forward rotation and reverse rotation, making it possible to uniformize the magnet temperature regardless of the rotor rotation direction.

[0056] Of course, even if the rotor circumferential position of the radial flow passage is outside the angle range 2 and θ3 in Fig. 5, bias in the refrigerant flow rate can be expected. However, there is a risk that the deviation between the flow rate bias during forward rotation and the flow rate bias during reverse rotation will become large.

[0057] (C5) In (C1) above, as shown in Figures 4 and 5, the positions of the multiple axial flow passages 301a, 301b are set at positions symmetrical with respect to the magnetic pole central axis J1, and the radial flow passages 400 are formed along the magnetic pole central axis J1. By providing the multiple axial flow passages 301a, 301b at positions symmetrical with respect to the magnetic pole central axis J1 in this way, and by forming the radial flow passages 400 along the magnetic pole central axis J1, it is possible to equalize the flow rate bias during forward rotation and reverse rotation, and to match the maximum magnet temperature reduction effect during forward rotation and reverse rotation.

[0058] 4 and 5, the radial flow passages 400 are formed along the magnetic pole central axis J1, and the axial flow passages 301a, 301b are arranged symmetrically with respect to the magnetic pole central axis J1 so that the flow rate bias during forward rotation and reverse rotation coincides. However, as long as the discrepancy in the flow rate bias during forward rotation and reverse rotation is within an allowable range, the radial flow passages 400 do not necessarily have to be formed along the magnetic pole central axis J1, and may be formed offset from the magnetic pole central axis J1 to the leading or lagging rotation side.

[0059] (C6) In (C1) above, as shown in FIG. 4 and other figures, the circumferential positions of the axial flow passages 301a, 301b are set between the q-axis of the rotor 11 and the magnetic pole center axis J1, closer to the magnetic pole center axis J1. By setting the circumferential positions of the axial flow passages 301a, 301b in this manner, it is possible to preferentially cool the divided magnet (M1 or M3) on the rotation-delay side, which has greater magnet loss. For example, if the axial flow passages 301a, 301b are close to the q-axis, this may affect the cooling of the divided magnets M1 to M3 of the adjacent magnetic pole, hindering uniformity of the magnet temperature.

[0060] (C7) In (C1) above, as shown in FIG. 11 , the flux barriers provided in rotor core 110 are configured as multiple axial flow paths. By using flux barriers 501a, 501b as coolant flow paths as well, there is no need to form additional axial flow paths 301a, 301b, which reduces costs. In addition, because there is no need for separate axial flow paths, which would increase magnetic resistance, it is possible to prevent a decrease in motor electrical performance due to increased magnetic resistance.

[0061] (C8) In (C1) above, as shown in FIG. 8, multiple layers are formed radially around rotor core 110, including magnet arrangement layers in which multiple divided magnets M1 to M3 are arranged circumferentially and magnet arrangement layers in which multiple divided magnets M4 to M6 are arranged circumferentially. Multiple axial flow paths 301a, 301b are arranged between pairs of radially adjacent magnet arrangement layers. This arrangement allows for increased cooling performance on the rotation delay side for divided magnets M4 to M6 on the inner circumferential side, similar to the case of divided magnets M1 to M3 on the outer circumferential side, and allows for uniform circumferential magnet temperature distribution for divided magnets M1 to M3 and M4 to M6.

[0062] The above-described embodiments and various modifications are merely examples, and the present invention is not limited to these unless the features of the invention are impaired. Furthermore, other embodiments conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0063] 1...electric vehicle, 2...wheel, 3...electric drive system, 4...oil cooler, 5, 7...cooling system, 6...chiller, 8...oil pump, 10...rotating electric machine, 11...rotor, 12...stator, 13...housing, 14a to 14c...bearings, 20...reduction gear, 110...rotor core, 111A, 111B...end plate, 112...rotor shaft, 112a, 112b...refrigerant flow path, 113...permanent magnet, 121...stator core, 122...stator coil, 301a, 301b...axial flow path, 303, 400, 402a, 402b...radial flow path, 304a, 304b, 401a, 401b...branch flow path, J1...magnetic pole center axis, M1 to M6...divided magnets

Claims

1. A rotor of a rotating electrical machine, comprising: a rotor core in which a plurality of permanent magnets are arranged in the circumferential direction; a rotating shaft that supports the rotor core; and a refrigerant flow path for cooling the permanent magnets, wherein the refrigerant flow path includes: a plurality of axial flow paths formed near the permanent magnets and on both sides of the magnetic pole center axis of each magnetic pole of the rotor core, and extending in the axial direction of the rotating shaft; a radial flow path extending radially from the rotating shaft side; and a plurality of branch flow paths branching from the radial flow path and connected to the plurality of axial flow paths.

2. The rotor according to claim 1, further comprising an end plate disposed on an axial end face of the rotor core, wherein the end plate has a radial groove extending in the radial direction and a plurality of branch grooves branching from the radial groove on a surface facing the axial end face, and the radial flow path and the plurality of branch flow paths are formed by the radial groove, the plurality of branch grooves, and the axial end face.

3. The rotor according to claim 1, wherein a flow path cross-sectional area of the branch flow path is set to be larger than a flow path cross-sectional area of the radial flow path.

4. The rotor according to claim 1, wherein a circumferential position of the radial flow path is set to be included in a circumferential range in which the plurality of axial flow paths are arranged.

5. The rotor according to claim 1, wherein positions of the plurality of axial flow paths are set to be symmetric with respect to the magnetic pole center axis, and the radial flow path is formed along the magnetic pole center axis.

6. The rotor according to claim 1, wherein a circumferential position of the axial flow path is set to be between the q-axis of the rotor and the magnetic pole center axis and closer to the magnetic pole center axis.

7. The rotor according to claim 1, wherein the flux barrier provided in the rotor core is the plurality of axial flow paths.

8. The rotor according to claim 1, wherein a plurality of magnet arrangement layers in which the plurality of permanent magnets are arranged in the circumferential direction are formed in a plurality of layers in the radial direction of the rotor core, and the plurality of axial flow paths are arranged between a pair of adjacent magnet arrangement layers in the radial direction.

9. A rotating electrical machine, comprising: the rotor according to claim 1; and a stator disposed on an outer diameter side of the rotor.

10. An electric drive system comprising the rotating electrical machine according to claim 9 as driving power.

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