Rotating electrical machine

Abstract

The present invention makes it less likely for a refrigerant to enter a gap between a rotor and a stator in a rotating electrical machine for injecting a liquid refrigerant to an end face of the rotor. Cylindrical projections 36, 39 projecting outward in the axial direction are provided on the outer peripheral sides of end plates 35 arranged on both side end faces of a rotor core 31. Cooling oil 71, 72 supplied from oil supply holes 4c, 5c of end brackets 4, 5 of a rotating electrical machine 1 hits an end face of a rotor 30 as shown by arrows 71a, 72a of the rotor 30, flows to the outer peripheral side, moves from the projections 36, 39 to a position (+ Zrf,-Zrr) separated from the rotor core 31 in the axial direction as shown by arrows 71c, 72c, and is then guided to a stator core 11 side. Further, the rotating electrical machine 1 is formed such that a coordinate +Zsf of the minimum inner diameter position of a resin 24 is closer to a center position than a coordinate +Zrf, and a coordinate -Zsr of the minimum inner diameter position of a resin 26 is closer to the center position than a coordinate -Zrr.

Description

Rotating electric machines

[0001] The present invention relates to a rotating electric machine in which a liquid refrigerant is sprayed onto the end face of the rotor in the direction of the rotation axis to cool the rotor and stator, and in particular to improvements in the shape of the end face of the rotor and the shape of the coil end portion of the stator.

[0002] Against the backdrop of global warming and the depletion of fossil fuels, the electrification and energy conservation of various power sources are accelerating. Motors, as key components, are required to have specifications that maximize system performance, including the load machinery and the inverter drive circuit. In particular, increasing motor speed is a highly sought-after feature across a variety of applications. For motors used in electric vehicles (EVs) and hybrid electric vehicles (HEVs), increasing motor speed increases motor output (∝ rotational speed × torque), thereby reducing motor size (∝ torque). While increasing motor speed increases the gear reduction ratio, it also enables overall system miniaturization. For air compressor motors used as utility devices for gears, the air compressor is now directly connected to the motor shaft without a speed-increasing gear, improving system efficiency.

[0003] On the other hand, increasing motor speeds increases losses in the rotor core and permanent magnets due to increased frequency and current harmonics, necessitating enhanced rotor cooling. Various rotor cooling methods using cooling oil have already been proposed. For relatively low-speed motors, a method of using the rotor to scoop up cooling oil stored inside the rotating electrical machine is used. However, this method is difficult to apply at high rotation speeds due to increased fluid friction loss. To prevent increased fluid friction loss, one method involves creating a cooling oil flow path within the rotating shaft. Simply cooling the shaft center alone is far from the heat source and does not provide sufficient heat dissipation, so many methods extend the flow path to the outer periphery of the rotor. Some methods also inject cooling oil into the coil end area to cool the stator side. However, using the rotating shaft as a cooling oil flow path requires pressure-fed cooling oil to the end of the rotating shaft, which requires an oil seal. Creating a cooling oil flow path all the way to the rotor further complicates the structure and increases costs. Therefore, a method of injecting cooling oil onto the end face of the rotor has been devised.

[0004] Patent Document 1 discloses a technique in which cooling oil flow paths are formed through the front and rear end faces (e.g., end brackets) of a motor housing, and cooling oil is sprayed toward the end face of the rotor through these flow paths. To achieve this, a cooling oil flow path is formed in the motor's end bracket, and cooling oil pressurized by an oil pump is supplied to the flow path. The outlet (nozzle) of the flow path is positioned so that it faces the end face of the rotor, and the cooling oil is sprayed toward the end face of the rotor. This method can be implemented at low cost because it does not require oil seals in the rotating parts or the formation of complex flow paths in the rotor. Furthermore, because the cooling oil is supplied close to the heat source of the rotor, a high heat dissipation effect can be expected.

[0005] Japanese Patent Application Laid-Open No. 2006-6091

[0006] In the cooling mechanism described in Patent Document 1, cooling oil adhering to the rotor end surface is subjected to a circumferential velocity component in the rotational direction and a radial velocity component due to centrifugal force, causing it to scatter toward the stator, move toward the center of the rotor as viewed in the direction of rotation, and potentially enter the gap (air gap or gap) between the rotor and stator. When cooling oil, which has a higher viscosity than air, enters the gap between the rotor and stator, fluid friction loss increases. Because fluid friction loss is proportional to the rotational speed, it can significantly reduce the efficiency of a rotating electrical machine, especially at high speeds.

[0007] The present invention has been made in view of the above background, and has an object to provide a rotating electric machine having a cooling mechanism that sprays a liquid refrigerant onto the end face of the rotor, while maintaining the efficiency of the rotating electric machine. Another object of the present invention is to provide a rotating electric machine configured to prevent liquid refrigerant from entering the gap between the rotor and the stator.

[0008] Representative features of the invention disclosed in this application are as follows. According to one feature of the present invention, a rotating electric machine includes a rotating shaft, a rotor, and a stator. The rotor includes a rotor core fixed to the rotating shaft and a permanent magnet attached to the rotor core. The stator includes a stator core and a coil, and a coil end portion is formed outward from the end of the stator core in the rotational axis direction. A cooling mechanism is provided at the axial end face of the rotor, which directly sprays a liquid refrigerant supplied from outside the rotating electric machine. The shapes of the stator and rotor are set so that the absolute values ​​of the coordinate Zr of the rotor end as viewed in both directions in the rotational axis direction from the center position in the axial direction of the rotor and the coordinate Zs of the tip of the coil end portion on the positive or negative side as viewed in the rotational axis direction satisfy |Zs|≦|Zr|. While it is desirable for the relationship |Zs|≦|Zr| to hold true around the entire circumference of the stator, it is sufficient for this relationship to hold at least at one location in the circumferential direction. Furthermore, a circumferentially continuous protrusion is provided on the end face of the rotor in the axial direction, which is located radially outer than the end of the cooling mechanism, and the absolute value |Zr| of the coordinate of the end of this protrusion in the axial direction is made equal to or greater than |Zs|, or the stack thickness of the rotor core (length in the axial direction) is made greater than the stack thickness of the stator core (length in the axial direction).

[0009] According to another feature of the present invention, an end plate is provided on the end surface of the rotor core in the rotational axis direction, and a cylindrical protrusion protruding in the rotational axis direction is formed near the outer periphery of the end plate. The absolute value of the tip coordinate of the protrusion as viewed in the rotational axis direction is Zr, and the relationship |Zs|≦|Zr| is satisfied. The inner periphery of the protrusion may be provided with an inclined portion so that the inner diameter expands radially outward in a linear, curved, or stepped manner. Furthermore, depending on the difference in the shape of the output side and anti-output side of the coil end portion of the stator, the shapes of the protrusions on the output side and anti-output side may be the same or different. The rotor core of the rotor holds multiple permanent magnets, and the protrusions are formed so that the radius Rm of the innermost diameter of the permanent magnets and the radius Rt of the innermost diameter of the protrusions satisfy the relationship Rm<Rt.

[0010] According to yet another feature of the present invention, a rotary electric machine is provided with plate-shaped end plates on both end faces of a cylindrical rotor core in the direction of the rotation axis, and liquid refrigerant is directly sprayed onto the end plates from the outside of the housing through a dedicated refrigerant path, and a circumferentially continuous cylindrical protrusion is formed on the outer periphery of the end plate radially outward from the spray center point of the liquid refrigerant to guide the sprayed liquid refrigerant away from the end plate in the direction of the rotation axis.

[0011] According to the present invention, the liquid refrigerant splashing from the rotor to the stator is away from the gap between the rotor and the stator, and the liquid refrigerant adhering to the stator moves in the opposite direction to the gap. This prevents an increase in fluid friction loss due to the liquid refrigerant, achieving both high heat dissipation from the rotor and high efficiency of the rotating electrical machine. Other issues, configurations, and effects will become clear from the following description.

[0012] 9A is a perspective view showing the appearance of a rotating electric machine 1 according to a first embodiment of the present invention. It is a cross-sectional perspective view showing the internal structure of the rotating electric machine 1 of FIG. 1. It is a vertical cross-sectional view taken along the line A-A of the rotating electric machine 1 of FIG. 2. It is a schematic partial cross-sectional view for explaining the configuration of the rotating electric machine 1 according to the first embodiment of the present invention. It is a schematic partial cross-sectional view for explaining the configuration of a rotating electric machine 1A according to a modified example of the first embodiment of the present invention. It is a schematic partial cross-sectional view for explaining the configuration of a rotating electric machine 1B according to a second embodiment of the present invention. It is a schematic partial cross-sectional view for explaining the configuration of a rotating electric machine 1C according to a third embodiment of the present invention. It is a schematic partial cross-sectional view for explaining the configuration of a rotating electric machine 1D according to a fourth embodiment of the present invention. It is a cross-sectional view of molding dies 300, 300A and stators 10, 110 when molding a stator 10, where FIG. 9A shows the die structure in this embodiment and FIG. 9B shows the die structure in a conventional example. It is a schematic partial cross-sectional view for explaining the configuration of a rotating electric machine 101 according to a conventional example. It is a schematic partial cross-sectional view for explaining the configuration of a rotating electric machine 101A according to a conventional example.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same parts are given the same reference numerals, and repeated explanations will be omitted. Furthermore, in this specification, the front, back, left, right, and up and down directions will be described as directions shown in the drawings.

[0014] FIG. 1 is a perspective view showing the exterior of a rotating electric machine 1 according to an embodiment of the present invention. The rotating electric machine 1 is, for example, an electric motor, and is configured by housing 2, which accommodates a rotating shaft 40, a rotor 30 (see FIG. 2 ), and a stator 10 (see FIG. 2 ). The housing 2 is formed in a split shape, here consisting of a cylindrical portion 3 and disk-shaped end brackets 4 and 5 that are provided to close openings at both ends of the cylindrical portion 3. The cylindrical portion 3 is configured in two split shapes, with a cavity (denoted by reference numeral 51 in FIG. 2 , described below) formed therein for flowing cooling oil. The end brackets 4 and 5 are formed with through-holes 4a (see FIG. 2 ), 5a, through which the rotating shaft 40 passes. The rotating shaft 40 extends far forward from the front end bracket 4 and is connected to a load (not shown) directly or via a power transmission mechanism. The rear end bracket 5 may not necessarily be provided with a through-hole 5a. A plurality of connection portions for connecting pipes for supplying liquid refrigerant are formed on the cylindrical portion 3 and the end brackets 4 and 5 of the housing 2. The pipe connection portion 57 is a connection portion for a pipe that supplies cooling oil to the rear end face of the rotor 30 (described later in FIG. 2).

[0015] FIG. 2 is a cross-sectional perspective view showing the internal structure of the rotating electric machine 1 of FIG. 1 . The rotating electric machine 1 includes an annular stator 10 and a rotor 30 disposed inside the stator 10. The outer periphery of the stator 10 is fixed to the inner periphery wall of the cylindrical portion 3 of the housing 2, and the rotor 30 is fixed to a rotating shaft 40. The cylindrical portion 3 is formed by a front portion 3a and a rear portion 3b, and the space formed at the joint between these portions forms a first cooling path 51. A cylindrical bearing holder 4b extending rearward is formed on the outer periphery of the through hole 4a of the end bracket 4, and a bearing 41 is provided inside the bearing holder 4b. Similarly, a cylindrical bearing holder 5b extending forward is formed on the outer periphery of the through hole 5a of the end bracket 5, and a bearing 42 is provided inside the bearing holder 5b. The rotating shaft 40 is rotatably supported by the two bearings 41 and 42.

[0016] The stator 10 is mainly composed of a stator core 11 and coils wound in slots (described later in FIG. 3 ) of the stator core 11. Coil ends 20 protrude from the front side of the stator core 11, and coil ends 22 protrude from the rear side. Both coil ends 20, 22 are molded with resin (described in detail in FIG. 4 and subsequent figures). Lead wires (not visible in the figure) extend from the coil ends 22 and are wired in a star connection or delta connection on a connection plate 46.

[0017] The housing 2 is provided with four cooling paths through which a refrigerant flows to cool heat-generating components. A liquid refrigerant, such as cooling oil, is used. The main cooling targets of the cooling paths are the stator 10, the rotor 30, and the bearings 41 and 42. The first cooling path 51 is located on the outer periphery of the stator 10 and primarily cools the stator core 11 and coils (20, 22, etc.) by flowing cooling oil through a hollow portion (first cooling path 51) formed within the cylindrical portion 3. A cooling oil inlet and outlet (both not visible in the figure) are connected to the first cooling path 51, allowing the cooling oil to circumferentially circulate. The first cooling path 51 is used for indirect cooling, in which the cooling oil does not directly contact the cooling targets.

[0018] The cylindrical portion 3 is formed with a cooling oil supply port 52 for cooling the coil ends 20 of the stator 10 and a cooling oil supply port 53 for cooling the coil ends 22. Cooling oil supplied from an external pipe is supplied directly to the outer peripheral surfaces of the coil ends 20 from the cooling oil supply port 52. The cooling oil supplied to the outer peripheral surfaces of the coil ends 20 flows mainly in the circumferential direction along the outer peripheral surfaces of the coil ends 20 toward the bottom surface of the housing 2 and is discharged to the outside from the outlet port 6. Similarly, cooling oil is supplied directly to the outer peripheral surfaces of the coil ends 22 from the cooling oil supply port 53. The cooling oil supplied to the outer peripheral surfaces of the coil ends 22 flows mainly in the circumferential direction along the outer peripheral surfaces of the coil ends 22 toward the bottom surface of the housing 2 and is discharged to the outside from the outlet port 7. The flow paths that supply refrigerant to the front and rear sides of the stator 10 are second cooling paths 52 and 53, which are direct cooling paths.

[0019] A third cooling path 54 for flowing cooling oil from the outside is formed in the end bracket 4. The cooling path 54 extends from the radial outside of the end bracket 4 to near the center, then turns 90 degrees to extend rearward within the bearing holder 4b, and directly supplies cooling oil for lubrication and cooling to the bearing 41. Similarly, a third cooling path 55 for flowing cooling oil from the outside is formed in the end bracket 5. The cooling path 55 extends from the radial outside of the end bracket 5 to near the center, then turns 90 degrees to extend forward within the bearing holder 5b, and directly supplies cooling oil to the bearing 42. The cooling paths 54 and 55 are direct cooling paths.

[0020] A fourth cooling path is further formed in the end brackets 4, 5, through which cooling oil is supplied from the outside and supplied to the front and rear end faces of the rotor 30. The fourth cooling path is a mechanism for cooling the rotor 30, and sprays cooling oil directly onto the end plates 35, 38 located at the end faces of the rotor 30. The inlet of the cooling path that sprays cooling oil onto the end plate 38 is a pipe connection 57. Note that a pipe connection 56 (see FIG. 3 described below), which serves as the inlet of the cooling path that supplies cooling oil to the front end face (end plate 35) of the rotor 30, is separately provided on the right side surface of the cylindrical portion 3 of the housing 2. The rotor cooling mechanism includes pipes and nozzles (not shown) attached to the inner wall surface of the housing 2 that lead to the end faces of the rotor 30. Cooling oil is sprayed from the nozzles near the rotor 30 onto the end plates 35, 38 in a direction substantially parallel to the rotation axis Z. An oil pump (not shown) and oil piping for pumping cooling oil (not shown) to the first to fourth flow paths are connected to the outside of the housing 2 of the rotating electrical machine 1. The cooling oil supplied to the inside of the housing 2 by the fourth cooling path is discharged to the outside of the housing 2 from outlets 6 and 7 together with the cooling oil supplied by the second and third cooling paths.

[0021] FIG. 3 shows a vertical cross-sectional view of the rotating electric machine 1 of FIG. 1 taken along line A-A. This cross-sectional view is perpendicular to the rotation axis Z. The stator core 11 of the stator 10 is composed of amorphous metal teeth 12 and an electromagnetic steel back yoke 13. However, the stator 10 may be of any shape, and the teeth 12 and back yoke 13 may be integrally formed. The spaces between adjacent teeth 12 form slots, and multiple rectangular wire coils 14 are radially arranged within the slots via bobbins 15. Although not shown here, the rectangular wire coils 14 are divided into one side (front side) and the other side (rear side) near the center of the stator 10 in the direction of the rotation axis Z. The windings of the coils 14 form a closed circuit by fitting together at concave and convex connecting portions (terminal portions) formed at the tip of the dividing surface. The rotor 30 is based on a rotor core 31 made of a large number of thin, annular electromagnetic steel plates laminated in the direction of the rotation axis Z, and a plate-shaped neodymium sintered permanent magnet 33 is disposed in each of a large number of slots 32 for accommodating magnets formed near the outer edge of the rotor core 31. A piping connection portion 56 for a fourth cooling mechanism is formed on the right side surface of the cylindrical portion 3 of the housing 2, near the front end bracket 4 (see Figure 2). Note that the cross sections of the rotor 30 and stator 10 in Figure 3 are not hatched.

[0022] Before describing the fourth cooling mechanism of the rotating electric machine 1 of the present invention, i.e., the configuration for injecting cooling oil onto the rotor 30, the flow of cooling oil in a conventional rotating electric machine 101 will be described with reference to Figures 10 and 11. Figure 10 is a partial cross-sectional view illustrating the shapes of the rotor 130 and stator 110 in the conventional rotating electric machine 101 and the flow of cooling oils 81 and 82.

[0023] The rotor core 131 and magnets 133 of the rotor 130 in FIG. 10 have the same shapes as the rotor 30 shown in FIGS. 2 and 3 . Note that this figure is a schematic illustration for explaining the overall configuration, and the rotor core 131 and stator core 111 are not hatched. The stator core 111 is a laminated core formed by stacking multiple thin electromagnetic steel sheets in the direction of the rotation axis Z. Coils are wound around slots in the stator core 111. The coil portions exposed at the front side from the stator core 111 are coil ends 120, and coil ends 122 extending rearward from the stator core 111 are formed at the rear side. In this rotating electric machine 101, cooling oil 81 is sprayed onto the front surface of the front end plate 135 of the rotor 130 from an oil supply hole 4c provided in the front end bracket 4. Similarly, cooling oil 82 is sprayed onto the rear surface of the rear end plate 138 of the rotor 130 from an oil supply hole 5 c provided in the rear end bracket 5 .

[0024] The cooling oil 81 sprayed from the oil supply hole 4c is sprayed rearward in a direction parallel to the rotation axis Z, as indicated by arrow 81a, toward a spray center point 191. This spray may be linear or may diverge conically. Similarly, the cooling oil 82 sprayed from the oil supply hole 5c is sprayed forward in a direction parallel to the rotation axis Z, as indicated by arrow 82a, toward a spray center point 192. Although not shown here, extension pipes and nozzles may be provided at the inner openings of the oil supply holes 4c and 5c so that the cooling oil 81 and 82 are sprayed in a predetermined direction with a predetermined degree of divergence. Even when a nozzle (not shown) is provided, the spray centers 191 and 192 are set to be radially outward from the bearings 41 and 42 and inward from the outer edge of the rotor 130. The spray centers 191 and 192 are set at two locations circumferentially on the front end face and rear end face of the rotor 130, respectively.

[0025] Cooling oil 81 that hits front end plate 135 of rotating rotor 130 flows radially outward on end plate 135 as indicated by arrow 81b due to centrifugal force while rotating in the circumferential direction, leaves the outer peripheral edge of end plate 135, and arrives at the inner peripheral surface of coil end 120. Most of cooling oil 81 then flows along the inner peripheral surface and vertical plane of coil end 120 as indicated by arrows 81c and 81d, falls to the bottom surface of cylindrical portion 3, and is discharged from discharge port 6 formed in the bottom surface area as indicated by arrow 81e.

[0026] The cooling oil 82 flows in the same manner: it is sprayed as indicated by arrow 82a, and upon hitting the rear end plate 138, it is rotated circumferentially by the rear end plate 138 of the rotating rotor 130, and flows radially outward as indicated by arrow 82b due to centrifugal force, leaves the outer peripheral end of the end plate 138, flows along the inner peripheral surface and vertical surface of the coil end 122 as indicated by arrows 82c and 82d, drops to the bottom surface of the cylindrical portion 3, and is discharged as indicated by arrow 82e from a discharge port 7 formed in the bottom region. The discharged cooling oil 82 is recovered, together with cooling oil 81, by a cooling oil recovery line (not shown), cooled, and then reused.

[0027] The cooling oil 81, 82 near the arrows 81b, 82b is accelerated in the circumferential and radial directions and splashes near the bases of the coil ends 120, 122, potentially penetrating the gap 128 as indicated by arrows 81f, 82f. Furthermore, depending on the shape of the coil ends 120, 122 on the stator 110 side, the cooling oil 81, 82 splashed toward the stator 110 side may also penetrate the gap 128 due to gravity or other factors. For example, in FIG. 10 , the coil ends 120, 122 are inclined so that their inner diameters increase toward the center of the rotor 130 in the Z-axis direction (the front-to-rear direction) to prevent interference between the strands. This type of shape is often seen in distributed winding coils using round wire. This type of inclination makes it even easier for the cooling oil 81, 82 splashed near the gap 128 to penetrate the gap 128.

[0028] FIG. 11 is a cross-sectional view of a rotating electric machine 101A in which coil ends 120, 122 are molded with resin 124, 126. The front coil end portion is formed by the coil end 120 and resin 124, and the rear coil end portion is formed by the coil end 122 and resin 126. In this manner, the entire coil, including the coil ends 120, 122, may be molded in an effort to improve the coil's holding strength and heat dissipation performance through high thermal conductivity. When molding the coil ends 120, 122, as shown in FIG. 9A , draft tapers 311 a, 311 b must be provided in the mold die (hereinafter, core die 310) that forms the inner diameter side. Furthermore, when molding the entire coil from the output side to the anti-output side using a single core die 310, the inclination direction of the inner circumferential surface of the resin 126 must be the same on both the output side and the anti-output side. In this structure, the inner peripheral surface of the mold 126 on the non-output side (the side closer to the rotation axis Z) must have a tapered shape 126a such that the inner diameter decreases toward the rear end (in the -Z direction). This shape makes it easier for splashed cooling oil to enter the gap 128 as shown by arrow 84f. Furthermore, in the case of a rotating electric machine 101A in which the coil ends 120, 122 are molded with resin 124, 126, the cooling oil does not flow out from the gaps between the coils, further increasing the risk of the cooling oil entering the gap 128. In rotating electric machines with distributed winding and wave winding using rectangular wire, which are used in many automotive motors, the coil ends rise almost perpendicularly from the end faces, so the coil shape does not resemble that shown in FIG. 10 . However, when molded, issues similar to those shown in FIG. 11 become apparent.

[0029] Next, the configuration of a rotating electric machine 1 according to a first embodiment of the present invention will be described using Figure 4. Figure 4 is a schematic partial cross-sectional view showing the configuration of the rotating electric machine 1. Hereinafter, in this specification, the positions of the ends of the rotor 30 will be described based on the size in the forward direction (+Z direction) and the size in the rearward direction (-Z direction) relative to the center position of the rotor 30 as viewed in the direction of the rotation axis Z (coordinate 0).

[0030] End plates 35, 38, which are metal members separate from the rotor core 31, are provided on the end faces of the rotor core 31 in the ±Z directions of the rotation axis. The end plates 35, 38 are often provided for reasons such as adjusting the rotational balance of the rotor 30 and preventing movement of the permanent magnets 33 in the ±Z directions of the rotation axis. Cooling oil 71 flowing into the front end plate 35 from the oil supply hole 4c of the end bracket 4 is sprayed in the −Z direction toward the surface (front face) of the end plate 35, as indicated by arrow 71a. The spray of cooling oil 71 indicated by arrow 71a is sprayed linearly or diffusely toward a spray center point 91 of the end plate 35, and has, for example, a conical spread. Similarly, cooling oil 72 flowing into the rear end plate 38 from the oil supply hole 5c of the end bracket 5 is sprayed linearly or diffusely toward the surface (rear face) of the end plate 38, as indicated by arrow 72a.

[0031] The disk-shaped end plates 35, 38, each having a through hole formed in the center through which the rotating shaft 40 passes, are provided with a protrusion 36 that protrudes forward from the surface of the end plate 35 (the surface that does not contact the rotor core 31) and a protrusion 39 that protrudes rearward from the surface of the end plate 38, near the outer periphery and located radially outward (on the outer diameter side) of the injection centers 91, 92 of the cooling oil 71, 72. The protrusions 36, 39 are cylindrical members that are continuous and have a constant cross-sectional shape in the circumferential direction, but the protrusion 36 on the output side and the protrusion 39 on the anti-output side are formed in different shapes. In FIG. 4 , the end plate 35 and the protrusion 36, and the end plate 38 and the protrusion 39 are formed integrally, but the protrusions 36, 39 may be manufactured as separate parts from the end plates 35, 38 rather than as an integral part. The end plates 35, 38 and the protrusions 36, 39 are preferably made of highly thermally conductive materials to improve heat dissipation, and non-magnetic materials are preferable to reduce leakage flux from the rotor 30, so they may be made of aluminum alloy, non-magnetic stainless steel, or the like.

[0032] The front coil end 20 and the rear coil end 22 of the stator 10 are molded with resin 24, 26. Here, the front and rear coil end portions are formed including the resin 24, 26, but the coil end portions may be formed only with the coil ends 20, 22 without using the resin 24, 26. The inner circumferential surfaces of the molded resin 24, 26 are formed with tapered portions 24a, 26a on both the output side and the anti-output side, whose inner diameters increase in a direction away from the center position. The output-side tapered portion 24a has a shape in which the inner diameter simply increases from the boundary with the stator core 11. On the other hand, the anti-output-side tapered portion 26a has a tapered portion 26b in which the inner diameter initially decreases significantly from the stator core 11 toward the rear, because the lead wires 23 drawn from the coil end 22 protrude significantly radially inward. Then, the tapered portion 26a has a shape in which the inner diameter increases. The reason why the lead wire 23 protrudes largely toward the inner diameter side is that when the coil divided in the axial direction is fitted, the axial load is transmitted to the fitting portion of the lead wire as well.

[0033] The inner positions (portions close to the rotation axis Z) of the protrusions 36 are located radially outward of the inner positions (inner peripheral positions close to the rotation axis Z) of the permanent magnets 33 when viewed in the radial direction R. In other words, the permanent magnets 33 are arranged in the rotor core 31 so that the radius Rm of the innermost diameter portion of the permanent magnets 33 and the radius Rt of the innermost diameter portion of the protrusions 36 satisfy the relationship Rm<Rt. The protruding tip positions of the protrusions 36 (the +Z coordinate of the rotor 30 on the front side) are +Zrf, and their inner positions are located radially outward of the inner positions (inner peripheral positions close to the rotation axis Z) of the permanent magnets 33. The protruding tip positions of the protrusions 36 are located forward of the position +Zsf where the diameter of the coil end portion on the stator 10 side is smallest (= the position of the front end face on the front side of the stator core 11). In other words, the relationship |Zsf|≦|Zrf| is satisfied.

[0034] The inner position of the protrusion 39 is located radially outward of the inner position of the permanent magnet 33 (the inner peripheral position close to the rotation axis Z). The protrusion tip position of the protrusion 39 (the distance from the end plate 38 in the rotation axis −Z direction) is −Zrr, which is located rearward of the position of the rear end face of the stator core 11 of the stator 10. The amount of protrusion of the protrusion 36 toward the front in the rotation axis direction is not the same as the amount of protrusion of the protrusion 39 toward the rear in the rotation axis direction. This is because the amount of protrusion of the protrusions 36, 39 toward the rotation axis Z is determined in accordance with the shape of the stator 10, particularly the minimum inner diameter position of the resins 24, 26. The outer diameter of the protrusion 39 is formed slightly smaller than the outer diameter of the protrusion 36 to avoid the inward convex portion of the resin 26 (the mountain-shaped portion formed by the tapered portions 26a and 26b, which is the minimum inner diameter portion). The inner diameter of protrusion 36 is slightly larger than the inner diameter of protrusion 39. Furthermore, the rearmost position −Zrr of protrusion 39 is located rearward of the innermost peripheral portion of the coil end portion, in this case, the position +Zsr between tapered portions 26a and 26b, where the diameter of resin 26 is smallest. In other words, the absolute values ​​of these positions satisfy the relationship |Zsr|≦|Zrr|.

[0035] The positional relationship between the protrusions 36, 39 and the coil ends 20, 22 is configured so that |Zsf|≦|Zrf| is satisfied on the front side (output side), and |Zsr|≦|Zrr| is satisfied on the rear side (non-output side). In other words, excluding the final suffixes "f" and "r" indicating the front and rear, the relationship |Zs|≦|Zr| is satisfied in either direction. In the shape of the resin 24 shown in FIG. 4, the coordinate Zsf coincides with the coordinate of the end face of the rotor core 31. On the other hand, for the coil end 22 on the non-output side, the punched tapered portion 26b from molding remains on the inner peripheral side except on the outer peripheral side, so the coordinate -Zsr is located rearward of the rear end face of the stator core 11 and corresponds to the boundary between the tapered portions 26b and 26a.

[0036] Next, the operation of the rotating electric machine 1 will be described. A DC magnetic field is generated by the permanent magnets 33 on the outer diameter side of the rotor 30. Meanwhile, a not-shown inverter generates three-phase power converted to a predetermined frequency and supplies it to the coils 14 (see FIG. 3 ) of the stator 10, creating a rotating magnetic field oriented in the radial direction of the stator 10. By passing an excitation current through the coils 14 in accordance with the magnetic pole positions of the stator 10, a predetermined torque is generated in the rotor 30 due to the attraction and repulsion between the rotating magnetic field and the DC magnetic field, causing the rotating shaft 40 to rotate in a predetermined direction (rotational direction). When the rotating electric machine 1 is driven, a not-shown oil pump pumps cooling oil through the first to fourth flow paths. In this way, cooling oil flows through the direct cooling flow path and the indirect cooling flow path within the housing 2, thereby cooling the heat-generating parts of the rotating electric machine 1.

[0037] The cooling oil 71, 72 sprayed from the fourth rotor cooling mechanism may be directly supplied to the front and rear end faces of the rotor 30, and the nozzle and piping structure may be arbitrary. The cooling oil may be supplied using piping and nozzles from the end brackets 4, 5 of the housing 2, or a portion of the cooling oil supplied to the bearings 41, 42 may be branched off and sprayed from the branched flow path onto the end faces of the rotor 30. The cooling oil 71, 72 sprayed onto the front end face (end plate 35) and rear end face (end plate 38) of the rotor 30 as indicated by arrows 71a, 72a hits the end plates 35, 38 and moves radially outward as indicated by arrows 71b, 72b while rotating circumferentially on the surfaces of the end plates 35, 38 due to surface tension.

[0038] The cooling oil 71, 72 that has reached the inner circumferential surfaces of the protrusions 36, 39 is prevented from moving radially outward by the protrusions 36, 39, and therefore moves in the directions of arrows 71c, 72c that are in the direction of the rotation axis Z and away from the end plates 35, 38. The cooling oil flows radially outward along the front end face of the protrusion 36 and the rear end face of the protrusion 39, and the cooling oil that splashes from the rotor 30 toward the stator 10 splashes toward the coil ends 20, 22 at a position spaced apart from the gap 28. At this time, the cooling oil splashes toward a position spaced apart from the front opening face and the rear opening face of the gap 28 by the height (length in the direction of the rotation axis Z) of the protrusions 36, 39. This effectively limits the amount of cooling oil that enters the gap 28 due to, for example, splashing of the cooling oil 71, 72 when it adheres to the inner circumferential surfaces of the coil ends 20, 22.

[0039] Furthermore, because the resins 24, 26 at the positions where the cooling oils 71, 72 are applied are formed with tapered portions 24a, 26a whose inner diameters expand toward the end brackets 4, 5, the kinetic energy and gravity of the cooling oils 71, 72 when they enter the tapered portions 24a, 26a can prevent the cooling oils 71, 72 from flowing toward the gap 28. This can prevent an increase in fluid friction loss due to the cooling oils 71, 72 entering the gap 28. In addition, because the cooling oils 71, 72 also move in the direction of the rotation axis along the protrusions 36, 39 as indicated by arrows 71c, 72c, the contact area between the cooling oils 71, 72 and the end plates 35, 38 of the rotor 30 increases, and the amount of heat dissipated from the rotor core 31 to the cooling oils 71, 72 increases. In particular, flow paths for the cooling oils 71 and 72 are formed near the front and rear end faces of the permanent magnets 33, which are the main heat source, as indicated by arrows 71c and 72c, thereby actively cooling the permanent magnets 33. As a result, it is possible to improve the heat dissipation of the rotor 30 and increase the efficiency of the rotating electric machine 1 at the same time.

[0040] In this embodiment, in order to avoid interference between the coil ends 26 protruding toward the inner diameter side and the protrusions 39 and to splash the cooling oil 72 toward the tapered portion 26a where the inner diameter is expanding, the outer diameter of the protrusions 39 on the anti-output side is made slightly smaller than the outer diameter of the rotor core 31, and the length in the rotation axis −Z direction (the protrusion height of the protrusions 36) is increased. As a result, the shapes of the protrusions 36, 39 on the output side and the anti-output side are different and asymmetrical, but a symmetrical shape may be used as long as the relationship between the positions +Zsf, −Zsr in the rotation axis Z direction of the innermost circumferential portion of the coil end portion (here, the inner circumferential portion of the resins 24, 26) and the positions +Zrf, −Zrr of the end faces of the protrusions 36, 39 that are respectively close to the end brackets 4, 5 satisfies the conditions |Zsf|≦|Zrf| and |Zsr|≦|Zrr| in absolute coordinates. Alternatively, the shape of the coil ends may be changed to a shape different from that shown in FIG. 4 .

[0041] FIG. 5 is a schematic partial cross-sectional view illustrating the configuration of a rotating electric machine 1A according to a modified example of the first embodiment. The difference from the rotating electric machine 1 in FIG. 4 is the shape of the lead wire 23A from the rear coil end 22, and the shapes of the resin 27 and the protrusion 39A are accordingly different. The lead wire 23A is drawn linearly from the stator core 11 in a direction substantially parallel to the rotation axis Z, and the inner peripheral shape of the resin 27 (tapered portion 27a) is formed as a plane symmetrical to the resin 24 with respect to the center position. The shapes of the resins 24 and 27 can be formed by a conventional molding method shown in FIG. 9B. In FIG. 9B, molding is performed using two divided cores of core molds 310A and 310B.

[0042] In Figure 5, cylindrical projections 36, 39A are provided on the outer periphery of the end plate, radially outward of the center of injection of the liquid refrigerant onto the end plate, to guide the injected liquid refrigerant away from the end plate in the direction of the rotation axis (toward the front and rear). Furthermore, by changing the shape of resin 27, the inner and outer diameters of front projection 36 and rear projection 39A are made the same for projections 36, 39A, and their dimensions along the rotation axis Z (projection heights) are also made the same. The relationship between the absolute positions +Zsf, -Zsr of the innermost portions of the coil end sections (here, the innermost portions of resin 24, 27) along the rotation axis Z and the absolute positions +Zrf, -Zrr of the end faces of projections 36, 39A near end brackets 4, 5, respectively, satisfies the conditions |Zsf| ≤ |Zrf| and |Zsr| ≤ |Zrr|. As a result, the end plates 35, 38A, which are integrally manufactured with the protrusions 36, 39A, can be made common parts, thereby reducing the number of types of components of the rotor 30A.

[0043] Next, a rotating electric machine 1B according to a second embodiment of the present invention will be described with reference to FIG. 6 . Components that overlap with those of the first embodiment shown in FIGS. 4 and 5 are designated by the same reference numerals, and therefore will not be described again. In the rotating electric machine 1B, the inner circumferential surfaces of the protrusions 36B and 39B of the rotor 30B are formed as inclined surfaces. When viewed in a cross section including the rotation axis Z as shown in FIG. 6 , the inclined surfaces have a cross-sectional shape in which the inner diameter increases linearly with increasing distance from the end plates 35B and 38B in the direction of the rotation axis Z. However, as long as the inclination is smooth, the cross-sectional shape may be formed as a curved inclined surface rather than a linear one. In FIG. 6 , the inclined surfaces of the protrusions 36B and 39B are shaped symmetrically with respect to the center position of the rotor 30B in the direction of the rotation axis Z. In the second embodiment as well, the relationship between the absolute position |Zsf| of the innermost peripheral portion of resin 24 in the direction of rotation axis Z and the absolute position |Zrf| of the end face of protrusion 36B close to end bracket 4 satisfies the condition |Zsf|≦|Zrf|. Furthermore, the relationship between the absolute position |Zsr| of the innermost peripheral portion of resin 27 in the direction of rotation axis Z and the absolute position |Zrr| of the end face of protrusion 39B close to end bracket 5 satisfies the condition |Zsr|≦|Zrr|.

[0044] Cooling oil 75, 76 supplied from oil supply holes 4c, 5c of end brackets 4, 5 is sprayed toward injection centers 91, 92 as indicated by arrows 75a, 76a, flows as indicated by arrows 75b to 75f and 76b to 76f, and is discharged to the outside through discharge ports 6, 7. At this time, the cooling oil 75, 76 flows smoothly in the axial and radial directions as indicated by arrows 75c, 76c on the tapered inner surfaces of protrusions 36B, 39B. By forming the inner surfaces of protrusions 36B, 39B into a tapered shape in this way, the cooling oil scattering from protrusions 36B, 39B is given an axial velocity component approaching the end brackets 4, 5 in addition to velocity components in the circumferential and radial directions. As a result, the faster the rotational speed of the rotor 30B, the farther the cooling oils 75 and 76 are scattered from the gap 28 in the direction of the rotation axis A1, thereby suppressing the occurrence of fluid friction loss due to the cooling oil entering the gap 28.

[0045] A third embodiment of the present invention will be described with reference to FIG. 7 . In the rotating electrical machine 1C of the third embodiment, an end plate 35C having a protrusion 36C and an end plate 38C having a protrusion 39C are disposed on both end faces of a rotor 30C. Unlike the second embodiment shown in FIG. 6 , the inner circumferential portions of the protrusions 36C and 39C are configured in a stepped or stepped shape, in which the inner diameter changes stepwise rather than a continuous slope. When viewed in a cross section including the rotation axis Z as shown in FIG. 7 , the step increases in two steps as the inner diameter increases in the +Z direction or the −Z direction from the end plates 35C and 38C. The stepped portions of the end plates 35C and 38C are shaped symmetrically with respect to the center position of the rotor 30C in the direction of the rotation axis Z. In the third embodiment as well, the relationship between the absolute position |Zsf| in the direction of the rotation axis Z of the innermost portion of the front coil end portion (here, the innermost portion of the resin 24) and the absolute position |Zrf| of the end face of the protrusion 39C close to the end bracket 4 satisfies the condition |Zsf|≦|Zrf|. Furthermore, the relationship between the absolute position |Zsr| in the direction of the rotation axis Z of the innermost portion of the rear coil end portion (the innermost portion of the resin 27) and the absolute position |Zrr| of the end face of the protrusion 39C close to the end bracket 5 satisfies the condition |Zsr|≦|Zrr|.

[0046] Cooling oil 77, 78 supplied from oil supply holes 4c, 5c of end brackets 4, 5 is sprayed toward injection centers 91, 92 as indicated by arrows 77a, 78a, flows as indicated by arrows 77b to 77f and 78b to 78f, and is discharged to the outside through discharge ports 6, 7. At this time, the cooling oil 77, 78 flows while bending in the axial and radial directions as indicated by arrows 77c, 78c on the tapered inner surfaces of protrusions 36C, 39C. By forming the inner surfaces of protrusions 36C, 39C in a stepped shape in this way, the cooling oil scattering from protrusions 36C, 39C is given an axial velocity component toward the end brackets 4, 5 in addition to circumferential and radial velocity components, and the contact time between protrusions 36C, 39C and cooling oil 77, 78 is increased. Furthermore, the faster the rotation speed of the rotor 30C, the farther the cooling oils 77 and 78 are scattered from the gap 28, thereby suppressing the occurrence of fluid friction loss due to the cooling oils 77 and 78 entering the gap 28.

[0047] FIG. 8 is a schematic partial cross-sectional view illustrating the configuration of a rotating electric machine 1D according to a fourth embodiment of the present invention. In the first to third embodiments, the protrusions 36, 39, etc. are used to configure the rotating electric machine 1D such that the absolute positions |Zsf|, |Zsr| of the innermost circumferential portions of the coil end portions (the innermost circumferential portions of the resin 24, 26) in the direction of the rotation axis Z and the absolute positions |Zrf|, |Zrr| of the end faces of the protrusions 36, 39 closest to the end brackets 4, 5 satisfy the conditions |Zsf|≦|Zrf| and |Zsr|≦|Zrr|. These conditions can also be satisfied by extending the axial length of the rotor core 31D without forming the protrusions 36, 39. As shown in FIG. 8 , the axial length (lamination thickness) L2 of the rotor core 31D is set to be greater by Lo on both the output side and the non-output side than the axial length (lamination thickness) L1 of the stator core 11 of the stator 10. In other words, the relationship L2 = L1 + 2Lo is established. As a result, the front end face of the permanent magnet 33D is positioned forward of +Zsf and the rear end face is positioned rearward of -Zsr, allowing the permanent magnet 33D to be formed large. Furthermore, the conditions |Zsf|≦|Zrf| and |Zsr|≦|Zrr| are satisfied, and the portions of the resins 24, 27 reached by the cooling oil 79, 80 flowing radially outward from the end plates 35D, 38D as indicated by arrows 79b, 80b are located approximately in the axial center of the tapered portions 24a, 27a whose inner diameters increase toward the end brackets 4, 5, and the distance from the end face to the rotor core 31 is relatively large, effectively preventing the cooling oil 79, 80 from entering the gap 28D.

[0048] In the fourth embodiment, the length of the rotor 30D in the direction of the rotation axis Z (mainly the stack thickness of the rotor core 31D) was increased with a simple rotor structure, thereby making it possible to increase the length of the permanent magnets 33D in the direction of the axis of rotation. As a result, the amount of magnetic flux of the rotor 30D increases, enabling improved characteristics such as increased torque, output, and efficiency of the rotating electric machine 1D. Note that in this embodiment, the requirements |Zsf|≦|Zrf| and |Zsr|≦|Zrr| are met by increasing the size of the rotor core 31D, but these relationships can also be achieved by increasing the thickness of the end plates 35D, 38D.

[0049] Although the present invention has been described above based on four embodiments, the present invention is not limited to the above-described embodiments and various modifications are possible within the scope of the invention.

[0050] DESCRIPTION OF SYMBOLS 1, 1A to 1D... Rotating electric machine, 2... Housing, 3... Cylindrical portion, 4, 5... End bracket, 4a, 5a... Through hole, 4b, 5b... Bearing holder, 4c, 5c... Oil supply hole, 6, 7... Discharge port, 10... Stator, 11... Stator core, 12... Teeth, 13... Back yoke, 14... Coil, 15... Bobbin, 20... Coil end (front side), 22... Coil end (rear side), 23, 23A... Pull-out Wire, 24, 26, 27...resin, 24a, 26a, 26b, 27a...tapered portion, 28, 28D...gap, 30, 30A to 30D...rotor, 31, 31D...rotor core, 32...slot, 33, 33D...permanent magnet, 35, 35B, 35C...end plate, 36...projection portion, 38, 38A to 38C...end plate, 39, 39A to 39C...projection portion, 40...rotating shaft, 41, 42...bearing, 46...wiring board, 51 ...first cooling path, 52, 53...cooling oil supply port (second cooling path), 54, 55...third cooling path, 56, 57...piping connection portion (fourth cooling path), 71-82...cooling oil (refrigerant), 91, 92...injection center point, 101, 101A...rotating electric machine, 110...stator, 111...stator core, 120, 122...coil end, 124, 126, 126C...resin, 128...gap, 130... Rotor, 131... rotor core, 135, 138... end plates, 191, 192... injection center point, 300, 300A... molding die, 310, 310B... core die, 320... upper die, 330... outer diameter die, 340... lower die, 410... stator, 420, 422... coil end, 424, 426... resin, Z... rotation axis, Zs... Z coordinate of innermost peripheral portion of coil end portion, Zr... Z coordinate of outer surface of end plate of rotor

Claims

1. A rotating electric machine comprising: a rotating shaft, a rotor having a rotor core and fixed to the rotating shaft; a stator having a stator core and a coil, with a coil end portion formed outward from the end of the stator core in the rotating shaft direction, and disposed on the outer periphery of the rotor with a gap between it and the rotor; and a cooling mechanism which injects liquid refrigerant onto the axial end face of the rotor, wherein the lengths of the stator and the rotor in the rotating shaft direction are set so that the coordinates Zrf, Zrr of the ends of the rotor viewed in the rotating shaft direction from the axial center position of the rotor, and the coordinates Zsf, Zsr of the innermost portion of the coil end portion viewed in the rotating shaft direction satisfy |Zsf|≦|Zrf| and |Zsr|≦|Zrr| at least at one point in the circumferential direction.

2. A rotating electric machine according to claim 1, characterized in that an end plate is provided on the end face in the rotational axis direction of the rotor core, and a cylindrical protrusion protruding in the rotational axis direction is provided near the outer periphery of the end plate, and the tip coordinate of the protrusion as viewed in the rotational axis direction is Zr, thereby satisfying the relationships |Zsf|≦|Zrf| and |Zsr|≦|Zrr|.

3. A rotating electric machine as claimed in claim 2, characterized in that an inclined portion is provided on the inner circumference of the protrusion so that the inner diameter expands linearly, curvedly or in a stepped manner towards the outer diameter side.

4. A rotating electric machine as claimed in claim 2, characterized in that the shapes of the protrusions on the output side and the anti-output side are formed to be different in accordance with the difference in shape between the output side and the anti-output side of the coil end portion of the stator.

5. A rotating electric machine as claimed in any one of claims 2 to 4, characterized in that the rotor is provided with permanent magnets held in the rotor core, and the permanent magnets are arranged in the rotor core so that the radius Rm of the innermost part of the permanent magnet and the radius Rt of the innermost part of the protrusion satisfy the relationship Rm < Rt.

6. A rotating electric machine according to claim 1, characterized in that the length of the rotor core in the direction of the rotation axis is greater than the length of the stator core in the direction of the rotation axis.

7. A rotating electric machine as claimed in any one of claims 1 to 4, characterized in that the coil end portion is composed of a coil end and a resin which molds the coil end, a tapered portion is formed on the inner peripheral surface of the resin, the inner diameter of which increases from the stator core towards the tip of the coil end, and the apex of the tapered portion where the inner diameter is smallest forms the Zr.

8. A rotating electric machine according to claim 7, characterized in that the tapered portion is provided between the lead wires drawn out from the coil.

9. A rotating electric machine comprising: a rotating shaft; a rotor having a cylindrical rotor core fixed to the rotating shaft, a plurality of permanent magnets arranged within the rotor core, and end plates provided on end faces of the rotor core in the direction of the rotation axis; a stator comprising a stator core and a coil, the coil end portions being formed outward from the end portions of the stator core in the direction of the rotation axis; and a cooling mechanism for injecting liquid refrigerant onto the end plates of the rotor core, wherein a cylindrical protrusion portion that is continuous in the circumferential direction is formed on the outer periphery of the end plate, which is radially outward from the center point of injection of the liquid refrigerant onto the end plate, for guiding the injected liquid refrigerant away from the end plate to the outside in the direction of the rotation axis.

10. A rotating electric machine as described in claim 9, characterized in that the positions of the stator and the protrusion in the rotational axis direction are set so that the coordinate Zr of the end of the protrusion of the rotor when viewed from the axial center position of the rotor to the rotational axis, and the coordinate Zs in the rotational axis direction of the innermost portion of the coil end portion satisfy |Zs|≦|Zr|.

11. A rotating electric machine according to claim 10, characterized in that the inner peripheral surface of the protrusion is provided with an inclined portion so that the inner diameter expands linearly, curvedly, or in a stepped manner toward the outer diameter side.

12. A rotating electric machine as claimed in claim 10, characterized in that the shape of the protrusions on the output side and anti-output side of the end plate of the rotor is made different in accordance with the difference in shape between the output side and anti-output side of the coil end portion of the stator.

13. A rotating electric machine as claimed in any one of claims 9 to 12, characterized in that the rotor is provided with a permanent magnet held in the rotor core, and the permanent magnet is arranged in the rotor core so that the radius Rm of the innermost diameter of the permanent magnet and the radius Rt of the innermost diameter of the protrusion satisfy the relationship Rm < Rt.

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