Rotor, rotary electric machine and electric drive system

Abstract

To provide a rotor which can equalize magnet temperature to reduce the maximum magnet temperature.SOLUTION: A rotor 11 comprises: a rotor core 110 in which a plurality of split magnets M1 to M3 are arranged in a circumferential direction; a rotor shaft which supports the rotor core 110; and a coolant passage for cooling the split magnets M1 to M3. The coolant passage comprises: a plurality of axial passages 301a, 301b formed in the vicinity of the split magnets M1 to M3, and on both sides of a magnetic pole center shaft J1 of each magnetic pole of the rotor core 110, and extending in an axial direction of the rotor shaft; a radial passage 400 extending in a radial direction from a rotor shaft side; and a plurality of branch passages 401a, 401b branching from the radial passage 400 to be connected with the plurality of axial passages 301a, 301b.SELECTED DRAWING: Figure 7A

Description

Technical Field

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

Background Art

[0002] In a rotating electrical machine having a permanent magnet in a rotor, the magnet temperature rises due to magnet loss. When the temperature of the permanent magnet becomes high, the permanent magnet may undergo irreversible demagnetization, which may reduce the performance of the motor. Therefore, a configuration is adopted in which a refrigerant passage is provided in the rotor for cooling (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since the magnet loss during rotor rotation varies depending on the circumferential position of the permanent magnet, the magnet temperature tends to be non-uniform in the circumferential direction. Since the continuous rated output of the rotating electrical machine is limited by the maximum magnet temperature, the temperature non-uniformity causes a decrease in the continuous rated output.

Means for Solving the Problems

[0005] A rotor according to an aspect of the present invention is a rotor of a rotating electrical machine including 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 magnet, wherein the refrigerant flow path is formed near the permanent magnet and on both sides of the magnetic pole center axis of each magnetic pole of the rotor core, and includes 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 path and connected to the plurality of axial flow paths.

Effects of the Invention

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

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

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

[0009] Figure 1 is a diagram showing a schematic configuration of an electric vehicle to which the rotating electrical machine of the present embodiment is applied. An electric drive system 3 for driving the wheels 2 is mounted on the electric vehicle 1. The electric drive system 3 is a vehicle drive unit including devices such as a rotating electrical machine and an inverter.

[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. Note that in the present 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 exchange is performed 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 in the cooling system 5 is finally released from the chiller 6 to the outside of the vehicle.

[0011] Figure 2 is a cross-sectional view showing a main part of the electric drive system 3. The electric drive system 3 includes a rotating electrical machine 10 and a speed reducer 20 that transmits the driving force of the rotating electrical machine 10. Note that the electric drive system 3 may be configured to include an inverter in addition to the above configuration. In Figure 2, as shown by the arrow, the side where 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". Also, the upward direction in the drawing is defined as the "upper part" or "upper side", and the downward direction in the drawing is defined as the "lower part" or "lower side". The direction along the rotor shaft 112 of the rotating electrical machine 10 is defined as the "axial direction", the circumferential direction around the rotor shaft 112 is defined as the "circumferential direction", and the radial direction (radius direction) when centered on the axis of the rotor shaft 112 is defined as the "radial direction".

[0012] The rotating electrical 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 discharge ports 130a and 130b are formed at 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. Note that 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 so as to contact the axial end faces of the rotor core 110.

[0014] The speed reducer 20 includes a driving gear 21 and a driven gear 22. The driving gear 21 provided on the load side of the rotor shaft 112 meshes with the driven gear 22 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 driving gear 21 and the driven gear 22.

[0015] Figure 3 is a diagram for explaining the path of the cooling oil in the rotating electrical machine 10. In Figure 3, the dashed arrows indicate the path of the cooling oil. A refrigerant flow path 112a extending in the shaft axial direction is formed at the axial center of the rotor shaft 112. Although details will be described later, grooves for forming a refrigerant flow path are formed on the rotor core facing surfaces of the end plates 111A and 111B. By arranging the end plates 111A and 111B so as to contact the end faces of the rotor core 110, a refrigerant flow path is formed between the end face of the rotor core and the end plates 111A and 111B. Further, a hole penetrating from one end face to the other end face of the rotor core 110 is formed as a refrigerant flow path (hereinafter referred to as an axial flow path) in the rotor core 110.

[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 flows into the refrigerant flow path (axial flow path) of the rotor core 110. The cooling oil flowing into the axial flow path of the rotor core 110 flows in the direction of the opposite rotor core end face, and then flows through the refrigerant flow path formed between the opposite end face and the end plate 111B, and is discharged toward the coil end on the anti-load side (right side in the figure) of the stator coil 122. The cooling oil flowing into the refrigerant flow path formed between the rotor core 110 and the end plate 111B from the refrigerant flow path 112a also flows as shown by the dashed arrow, and is discharged toward the coil end on the load side (left side in the figure) of the stator coil 122.

[0017] The cooling oil accumulated in the housing 13 is discharged out of the housing from the cooling oil discharge ports 130a, 130b, and falls into the oil pan 70 disposed below the rotating electric 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 path formed in the rotor 11 will be described. FIG. 4 is a view showing the axial end face of the rotor core 110. FIG. 4 shows the end face on the load side of the rotor core 110 and the rotor shaft 112, and a cross section of the rotor shaft 112 at the rotor core end face position is shown. The permanent magnet 113 shown in FIG. 2 is composed of three split magnets M1, M2, and M3 as shown in FIG. 4. One magnetic pole is formed by a set of split magnets M1, M2, and M3. In FIG. 4, eight sets of split magnets M1, M2, and M3 are provided, and four N poles and four S poles are alternately arranged in the circumferential direction. Therefore, the circumferential interval of 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 split magnet M2 is disposed on the magnetic pole center axis J1, and the split magnets M1 and M3 are symmetrically disposed with respect to the magnetic pole center axis J1.

[0019] At positions with a radius r near the split magnets M1 and M3, axial channels 301a and 301b that penetrate the rotor core 110 in the axial direction are formed. In the example shown in FIG. 4, the axial channels 301a and 301b are symmetrically arranged with respect to the magnetic pole center axis J1 and are arranged at a position at an angle θ3 from the magnetic pole center axis J1. Further, on the rotor shaft 112, a plurality of refrigerant channels 112b that penetrate from the inner peripheral surface of the axial refrigerant channel 112a to the outer peripheral surface of the shaft are radially formed. Each refrigerant channel 112b is formed along the magnetic pole center axis J1.

[0020] FIG. 5 is a view showing the surfaces of the end plates 111A and 111B on the rotor core side. Note that the end plates 111A and 111B have the same shape. When the end plates 111A and 111B are arranged on the end faces of the rotor core 110, they are arranged with a circumferential phase shift of 180 degrees from each other. Hereinafter, the end plate 111A will be described.

[0021] In the end plate 111A, grooves that constitute refrigerant channels are respectively formed corresponding to the eight magnetic poles of the rotor core 110. When the end plate 111A is arranged on the end face of the rotor core 110, a channel surrounded by the grooves of the end plate 111A and the end face of the rotor core 110 is formed. Hereinafter, the grooves of the end plate 111A will be referred to as channels.

[0022] In the 180-degree range on the upper side in the drawing of the end plate 111A, four sets of channel groups (400, 401a, 401b) are formed at intervals of an angle θ1 (= 45 degrees). On the other hand, in the 180-degree range on the lower side in the drawing, four sets of channel groups (402a, 402b) are formed at intervals of the 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 branched in a Y shape from the outer peripheral side end of the radial flow path 400. The inner peripheral side end of the radial flow path 400 communicates with a refrigerant flow path 112b (see FIG. 4) formed in the rotor shaft 112. The branch flow path 401a extends to a position with a 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. That is, the branch flow path 401a communicates with the axial flow path 301a, and the branch flow path 401b communicates with the axial flow path 301b.

[0024] On the other hand, the flow path group (402a, 402b) formed in the 180-degree range on the lower side in the figure is composed of two radial flow paths 402a, 402b extending from the position with a radius r to the outer periphery. Each of the radial flow paths 402a, 402b is arranged at a position symmetric 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 side end region of the radial flow path 402a faces the axial flow path 301a (see FIG. 4) of the rotor core 110. Similarly, the inner peripheral side end region of the radial flow path 402b faces the axial flow path 301b (see FIG. 4) of the rotor core 110. That is, the radial flow path 402a communicates with the axial flow path 301a, and the radial flow path 402b communicates with the axial flow path 301b.

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

[0026] FIG. 6 is a diagram for qualitatively explaining the non-uniformity of the magnet temperature due to the imbalance of the magnet loss. In FIG. 6, an SPM (Surface Permanent Magnet) motor is taken as an example for explanation, but it can be similarly applied to the IPM (Interior Permanent Magnet) motor in the embodiment. The case where the rotor 91 rotates counterclockwise (in the direction of the thick arrow) with respect to the stator 90 is shown. The solid line 92 with an arrow indicates the magnetic flux of the permanent magnet provided on the rotor 91, and the broken line 93 with an arrow indicates the magnetic flux due to the q-axis current.

[0027] The magnetic flux density of the magnetic flux obtained by synthesizing the magnetic flux 92 of the permanent magnet and the magnetic flux 93 due to the q-axis current is such that in the tooth A close to the rotation advance side of the magnetic pole (N pole), the directions of both magnetic fluxes are the same and they reinforce each other. Therefore, the magnetic flux density becomes large in the tooth A and approaches the saturation state, and the magnetic permeability in the tooth A seems to become small. On the other hand, in the tooth B close to the rotation lag side of the magnetic pole (N pole), the directions of both magnetic fluxes are opposite and they weaken each other. Therefore, the magnetic flux density becomes small in the tooth B and there is a margin with respect to the saturation state, and the magnetic permeability in the tooth B remains large.

[0028] As a result, the eddy current generated by the change in magnetic flux density is larger on the rotation lag side, and the temperature rise becomes larger. In this way, the magnet loss varies depending on the circumferential position of the permanent magnet, and the magnet temperature also becomes non-uniform. Since the continuous rated output of the electric drive system 3 is limited by the maximum magnet temperature, the non-uniformity of the temperature causes a decrease in the continuous rated output. Therefore, in the present embodiment, as shown in FIG. 5, flow paths 400, 401a, and 401b through which the refrigerant flows are provided to cool more the regions where the temperature of the permanent magnets (divided magnets M1, M2, M3) is high, suppress the temperature non-uniformity between the divided magnets M1, M2, and M3, and aim to lower the temperature.

[0029] FIGS. 7A and 7B are diagrams for explaining the flow direction of the refrigerant according to the rotor rotation direction. FIG. 7A shows the case where the rotor rotation direction is counterclockwise (left rotation R1), and FIG. 7B shows the case where the rotor rotation direction is clockwise (right rotation R2). In FIGS. 7A and 7B, the end face on the load side of the rotor core 110 and the flow paths 400, 401a, and 401b are shown, and the flow paths 400, 401a, and 401b formed by the end face on the load side of the rotor 110 and the grooves of the end plate 111A are shown by two-dot chain lines.

[0030] The flow direction of the refrigerant flowing through the flow paths 400, 401a, and 401b in the rotating rotor core 110 will be described. Hereinafter, it is considered in a coordinate system (rotating coordinate system) fixed to the rotating rotor core 110. When the angular velocity vector of the 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 forces generated by the rotor rotation are the Coriolis force in the second term on the right side of Equation (1) and the centrifugal force in the fourth term on the right side. FIG. 7A shows the case where the rotor core 110 rotates counterclockwise (in the direction of arrow R1), and the refrigerant flows toward the outer circumferential direction as indicated by the dashed arrow in the radial flow path 400. Since the centrifugal force is a radial force, it becomes a force in the same direction as the velocity vector v of the refrigerant flowing in the outer circumferential direction in the radial flow path 400. On the other hand, the Coriolis force Fc in the second term on the right side is a force directed in the direction opposite to the rotation direction.

[0032] That is, the refrigerant flowing through the radial flow path 400 tends to flow so as to bend toward the circumferential rotation lag side (clockwise direction) by the Coriolis force Fc that depends on the velocity vector (flow velocity) v. The same applies to the case of FIG. 7B where the rotation direction is clockwise (in the direction of arrow R2), and the refrigerant flowing through the radial flow path 400 tends to flow so as to bend toward the circumferential rotation lag side (counterclockwise direction).

[0033] In the present embodiment, as shown in FIGS. 7A and 7B, the radial flow path 400 formed along the magnetic pole center axis J1 branches into two branch flow paths 401a and 401b at its tip. In the case of FIG. 7A, the branch flow path 401a branches toward the circumferential rotation advance side with respect to the magnetic pole center axis J1 and communicates with the axial flow path 301a arranged on the rotation advance side. The branch flow path 401b branches toward the circumferential rotation lag side with respect to the magnetic pole center axis J1 and communicates with the axial flow path 301b arranged on the rotation lag side.

[0034] In the case of FIG. 7A, since the Coriolis force Fc in the direction of the rotation lag side acts on the refrigerant flowing in the outer peripheral direction in the radial flow path 400, the refrigerant is more likely to flow into the branch flow path 401b than into the branch flow path 401a. As a result, the refrigerant flow rates Q1 and Q2 in the branch flow paths 401a and 401b are biased such that Q2 > Q1. Naturally, the refrigerant flow rate (= Q2) in the axial flow path 301b is larger than the refrigerant flow rate (= Q1) in the axial flow path 301a (Q2 > Q1). As described above, the split magnets M1, M2, and M3 have a larger temperature rise as they are closer to the rotation lag side, but the cooling capacity by the refrigerant is larger as they are closer to the rotation lag side (Q2 > Q1). Therefore, the temperature rise of the split magnets M1, M2, and M3 is efficiently suppressed, the temperature is equalized, and the maximum magnet temperature can be reduced.

[0035] Similarly, in the case of FIG. 7B where the rotor rotation direction is clockwise R2, the Coriolis force Fc acting in the direction of the rotation lag side is in the opposite direction to that in the case of FIG. 7A with respect to the refrigerant flowing in the outer peripheral direction in the radial flow path 400. Therefore, the refrigerant is more likely to flow into the branch flow path 401a on the rotation lag side. As a result, the magnitudes of the refrigerant flow rates Q1 and Q2 in the axial flow paths 301a and 301b are such that Q1 > Q2. That is, the split magnets M1, M2, and M3 have a larger temperature rise as they are closer to the rotation lag side, but the cooling capacity by the refrigerant is larger as they are closer to the rotation lag side (Q1 > Q2). Therefore, the temperature rise of the split magnets M1, M2, and M3 is efficiently suppressed, the temperature is equalized, and the maximum magnet temperature can be reduced.

[0036] As described above, in the present embodiment, regardless of the forward rotation and reverse rotation of the rotor 11, the temperature rise of the split magnets M1, M2, and M3 is efficiently suppressed, the temperature is equalized, and the maximum magnet temperature can be reduced. Note that since the refrigerant flow rates in the branch flow paths 401a and 401b are biased by the rotor rotation as described above, it is preferable to set the flow path cross-sectional areas S2 (see FIG. 7A) of the branch flow paths 401a and 401b to be 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 way, the refrigerant can flow smoothly from the radial flow path 400 into the branch flow paths 401a and 401b without any delay.

[0037] (Modification Example 1) FIG. 8 is a diagram showing Modification Example 1 of the above-described embodiment. FIG. 8 shows the q-axis and the q-axis adjacent to each other on the end face of the load side of the rotor core 110, and the corresponding flow paths 400, 401a, and 401b. The flow paths 400, 401a, and 401b are shown by two-dot chain lines in the same manner as in FIGS. 7A and 7B.

[0038] In Modification Example 1, six divided magnets M1 to M6 are provided at each magnetic pole. Note that FIG. 8 shows one magnetic pole, and the other magnetic poles have the same configuration. The six divided magnets M1 to M6 are composed of the divided magnets M1 to M3 on the outer peripheral side and the divided magnets M4 to M6 on the inner peripheral side, and are arranged in two inner and outer layers. In this case, the axial flow paths 301a and 301b formed in the rotor core 110 are arranged between the divided magnets M1 to M3 on the outer peripheral side and the divided magnets M4 to M6 on the inner peripheral side. By arranging in this way, the cooling performance on the rotation delay side can be increased for the divided magnets M4 to M6 on the inner peripheral side as well as for the divided magnets M1 to M3 on the outer peripheral side, and the uniformity of the magnetic pole temperature distribution in the circumferential direction can be achieved for both the divided magnets M1 to M3 on the outer peripheral side and the divided magnets M4 to M6 on the inner peripheral side.

[0039] (Modification Example 2) FIGS. 9 and 10 are diagrams for explaining Modification Example 2 of the above-described embodiment. FIG. 9 is a diagram showing the end face of the load side of the rotor core 110. Note that the end face on the non-load side has the same shape as the load side. In Modification Example 2, in addition to the axial flow paths 301a and 301b, the rotor core 110 is also formed with a radial flow path 303 and branch flow paths 304a and 304b.

[0040] The radial flow path 303 communicates with the refrigerant flow path 112b of the rotor shaft 112 on the inner peripheral side of the rotor core. The branch flow paths 304a and 304b branch off in a Y shape from the outer peripheral end of the radial flow path 303. The tip region of the branch flow path 304a communicates with the axial flow path 301a. The tip region of the branch flow path 304b communicates with the axial flow path 301b.

[0041] Note that the shapes of the radial flow path 303 and the branch flow paths 304a and 304b are set to be the same as those of the radial flow path 400 and the branch flow paths 401a and 401b of the embodiment. Also, the radial flow path 303 and the branch flow paths 304a and 304b are formed at the same axial position of the rotor core 110. When considering the balance of the flow rates of the refrigerant flowing through the axial flow paths 301a and 301b on the load side and the counter-load side, it is preferable to arrange the radial flow path 303 and the branch flow paths 304a and 304b at the central position in the axial direction.

[0042] FIG. 10 is a view showing the rotor core facing surface of the end plate 111A. The end plate 111B arranged on the counter-load side also has the same shape as the end plate 111A shown in FIG. 10. In the end plates 111A and 111B in the second modification, the radial flow paths 402a and 402b are arranged over the entire 360-degree range. That is, corresponding to the eight sets of axial flow paths 301a and 301b formed in the rotor core 110 shown in FIG. 9, eight sets of radial flow paths 402a and 402b are formed.

[0043] The refrigerant flowing into the axial flow paths 301a and 301b of the rotor core 110 in FIG. 9 partly flows to the load side and the rest flows to the counter-load side. As a result, the split magnets M1 to M3 are indirectly cooled by the refrigerant. The refrigerant flowing through each of the axial flow paths 301a and 301b to the load side flows into the corresponding radial flow paths 402a and 402b of the end plate 111A. On the other hand, the refrigerant flowing through each of the axial flow paths 301a and 301b to the counter-load side flows into the corresponding radial flow paths 402a and 402b of the end plate 111B. The refrigerant flowing into the radial flow paths 402a and 402b of each of the end plates 111A and 111B flows in the outer circumferential direction within the radial flow paths 402a and 402b and flows out toward the coil ends of the stator coil 122 provided in the stator core 121 as shown in FIG. 3. As a result, the coil ends of the stator coil 122 are cooled by the refrigerant.

[0044] In Modification 2, although the radial flow path 303 and the branch flow paths 304a and 304b are formed inside the rotor core 110, the same effects as those of the above-described embodiment are achieved. That is, regardless of whether the rotation direction of the rotor core 110 is forward rotation or reverse rotation, the refrigerant flow rate is higher in the branch flow path on the rotation lag side than on the rotation advance side. Note that when the flow paths 303, 304a, and 304b are formed inside the rotor core 110, the magnetic resistance increases due to the flow paths, and there is a possibility that the motor electrical performance is affected. Therefore, it is preferable to form the grooves in the end plates 111A and 111B to form the flow paths 400, 401a, and 401b as in the embodiment.

[0045] (Modification 3) FIG. 11 is a diagram showing Modification 3 of the above-described embodiment. The divided magnets M1 to M3 are arranged in the magnet holes formed in the rotor core 110. The permanent magnet provided in the rotor core 110 is magnetized such that the outer peripheral side of the core is the N pole or the S pole and the inner peripheral side of the core is the opposite pole. In this magnet arrangement, a short circuit of the magnet magnetic flux is likely to occur at the circumferential end of the magnet. Therefore, an air gap called a flux barrier for preventing the short circuit of the magnet magnetic flux is formed in the magnet hole.

[0046] Generally, the flux barriers are formed at both circumferential ends of the permanent magnet. In FIG. 11, a flux barrier 501a is formed on the q-axis side of the divided magnet M1, and a flux barrier 501b is formed on the q-axis side of the divided magnet M3. The flux barrier 501a communicates with the magnet hole in which the divided magnet M1 is housed, and the flux barrier 501b communicates with the magnet hole in which the divided magnet M3 is housed.

[0047] The flux barriers 501a and 501b are holes that penetrate the rotor core 110 in the axial direction. In Modification 3, these flux barriers 501a and 501b are used instead of the axial flow paths 301a and 301b described above. As shown in FIG. 11, in the end plate 111A, the branch flow path 401a branched from the radial flow path 400 is formed such that the tip region faces the flux barrier 501a. On the other hand, the tip region of the branch flow path 401b is formed to face the flux barrier 501b. That is, 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 Modification 3, by also using the conventionally provided flux barriers 501a and 501b as the refrigerant flow paths, it is not necessary to additionally form the axial flow paths 301a and 301b. Therefore, cost reduction can be achieved. In addition, since it is not necessary to separately provide the axial flow paths 301a and 301b that are factors increasing the magnetic resistance, it is possible to prevent a decrease in the motor electrical performance due to an increase in the magnetic resistance.

[0049] According to the embodiments and modifications of the present invention described above, the following operational effects are achieved.

[0050] (C1) As shown in FIGS. 4, 5, 7A, 7B, etc., 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 a refrigerant flow path (301a, 301b, 400, 401a, 401b) for cooling the segmented magnets M1 to M3. The refrigerant flow path (301a, 301b, 400, 401a, 401b) is formed in the vicinity of the segmented 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 includes a plurality of axial flow paths 301a and 301b that extend in the axial direction of the rotor shaft 112, a radial flow path 400 that extends radially from the rotating shaft side, and a plurality of branch flow paths 401a and 401b that branch from the radial flow path 400 and are connected to the plurality of axial flow paths 301a and 301b.

[0051] When the rotor core 110 rotates, the magnetic loss is greater on the rotation lag side of the split magnets M1, M2, and M3, and the temperature rise is greater on the rotation lag side. However, as described above, a plurality of axial flow paths 301a and 301b are formed on both sides of the magnetic pole center axis J1, and the branch flow paths 401a and 401b branched from the radial flow path 400 are connected to the axial flow paths 301a and 301b. As a result, a large amount of refrigerant flows through the branch flow paths and axial flow paths arranged on the rotation lag side. As a result, in both the normal rotation and reverse rotation states, the temperature rise due to magnetic loss is suppressed more on the rotation lag side, and the circumferential magnetic temperature distribution can be made uniform and the maximum magnet temperature can be reduced.

[0052] (C2) In (C1) above, as shown in FIGS. 4, 5, etc., the rotor 11 includes end plates 111A and 111B disposed on the axial end faces of the rotor core 110. The end plate 111A has a radial groove (400) extending in the radial direction and a plurality of branch grooves (401a, 401b) branching from the radial groove (400) on the surface facing the axial end face of the rotor core 110. The radial groove, 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 and 401b.

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

[0054] (C3) In (C1) above, as shown in FIG. 7A, the flow path cross-sectional areas S2 of the branch flow paths 401a and 401b are set to be larger than the flow path cross-sectional area S1 of the radial flow path 400. Therefore, even when there is a bias in the refrigerant flow rate flowing into the branch flow paths 401a and 401b due to rotor rotation, the refrigerant can flow smoothly from the radial flow path 400 into the branch flow paths 401a and 401b without delay.

[0055] (C4) In (C1) above, as shown in FIGS. 4 and 5, the circumferential position of the radial flow path 400 is set to be included in the circumferential range (angle 2·θ3) where the plurality of axial flow paths 301a and 301b are arranged. By setting it in this way, one of the branch flow paths 401a and 401b extends from the radial flow path 400 toward the rotation forward side, and the other extends from the radial flow path 400 toward the rotation retardation side. Therefore, the difference in the bias of the refrigerant flow rate toward the rotation retardation side during normal rotation and reverse rotation is suppressed, and the magnetization temperature can be made uniform regardless of the rotor rotation direction.

[0056] Of course, even when the circumferential position of the radial flow path with respect to the rotor is outside the angular range 2·θ3 in FIG. 5, a bias in the refrigerant flow rate can be expected. However, there is a possibility that the deviation between the flow rate bias during normal rotation and the flow rate bias during reverse rotation may increase.

[0057] (C5) In (C1) above, as shown in FIGS. 4, 5, etc., the positions of the plurality of axial flow paths 301a and 301b are set to be symmetric with respect to the magnetic pole center axis J1, and the radial flow path 400 is formed along the magnetic pole center axis J1. By providing the plurality of axial flow paths 301a and 301b at positions symmetric with respect to the magnetic pole center axis J1 in this way, and forming the radial flow path 400 along the magnetic pole center axis J1, the flow rate bias during normal rotation and reverse rotation can be made equal, and the effect of reducing the maximum temperature of the magnet during normal rotation and reverse rotation can be made consistent.

[0058] In the example shown in FIGS. 4 and 5, the radial flow path 400 is formed along the magnetic pole center axis J1 so that the flow rate bias during normal rotation and reverse rotation coincides, and the axial flow paths 301a and 301b are arranged symmetrically with respect to the magnetic pole center axis J1. However, if the discrepancy in the flow rate bias between normal rotation and reverse rotation is within the allowable range, it is not necessarily required to form the radial flow path 400 along the magnetic pole center axis J1, and it may be formed offset toward the rotation forward side or the rotation retardation side from the magnetic pole center axis J1.

[0059] (C6) In the above (C1), as shown in FIG. 4 etc., the circumferential positions of the axial flow paths 301a and 301b are between the q-axis of the rotor 11 and the magnetic pole center axis J1, and are set at a position closer to the magnetic pole center axis J1. By setting the circumferential positions of the axial flow paths 301a and 301b in this way, it is possible to preferentially cool the split magnets (M1 or M3) on the rotation lag side where the magnet loss is large. For example, when the axial flow paths 301a and 301b are close to the q-axis, it may affect the cooling of the split magnets M1 to M3 of the adjacent magnetic poles and may prevent the uniformization of the magnet temperature.

[0060] (C7) In the above (C1), as shown in FIG. 11, a plurality of axial flow paths are used as the flux barriers provided in the rotor core 110. By also using the flux barriers 501a and 501b as refrigerant flow paths, it is not necessary to additionally form the axial flow paths 301a and 301b, and cost reduction can be achieved. Also, since an axial flow path that causes an increase in magnetic resistance is not separately required, a decrease in the motor electrical performance due to an increase in magnetic resistance can be prevented.

[0061] (C8) In the above (C1), as shown in FIG. 8, a magnet arrangement layer in which a plurality of split magnets M1 to M3 are arranged in the circumferential direction and a magnet arrangement layer in which a plurality of split magnets M4 to M6 are arranged in the circumferential direction are formed in a plurality of layers in the radial direction of the rotor core 110. And the plurality of axial flow paths 301a and 301b are arranged between a pair of magnet arrangement layers adjacent in the radial direction. By arranging in this way, the cooling performance on the rotation lag side can be increased for the split magnets M4 to M6 on the inner peripheral side as well as in the case of the split magnets M1 to M3 on the outer peripheral side, and the circumferential magnetic temperature distribution can be made uniform for the split 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 contents as long as the features of the invention are not impaired. Also, other aspects conceivable within the scope of the technical idea of the present invention are included in the scope of the present invention.

Explanation of Reference Numerals

[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 - 14c... Bearing, 20... Reducer, 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 - M6... Divided magnet

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 branched 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 branched 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 where 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 between the q-axis of the rotor and the magnetic pole center axis and is set to be closer to the magnetic pole center axis.

7. The rotor according to claim 1, wherein a 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 magnet arrangement layers adjacent 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 including the rotating electrical machine according to claim 9 as driving power.

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