Rotary electric machine and electric motor system

Abstract

The present invention comprises: at least one set of axial flow paths including a plurality of axial flow paths which are provided along an axial direction inside a rotor and through which a liquid refrigerant flows; a plurality of supply paths that are provided inside the rotor or perpendicular to the axial direction inside the rotary shaft of the rotor so as to have a cross-sectional area larger than that of the axial flow paths, the plurality of supply paths being connected to the plurality of axial flow paths, respectively, and supplying the liquid refrigerant to the plurality of axial flow paths; and a discharge path that is provided inside the rotor or perpendicular to the axial direction inside the rotary shaft of the rotor so as to have a cross-sectional area larger than that of the axial flow paths, the discharge path being connected to the axial flow paths and discharging the liquid refrigerant from the axial flow paths. The plurality of axial flow paths of the set of axial flow paths are arranged in different positions in the axial and circumferential directions of the rotor. The present invention enables the cooling performance of a rotor to be improved by using a simple method to reduce the pressure loss of a cooling flow path in the rotor and increase the flow rate of refrigerant.

Description

Rotating electric machines and electric motor systems

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

[0002] Rotating electric machines, such as motors used in industrial and mobility applications, require cooling of their stators and rotors, and are provided with cooling structures for this purpose. Meanwhile, in industrial rotating electric machines, miniaturization and higher power density are required to reduce installation space, and further improvements in cooling performance are required. Furthermore, with the recent advancement of electrification of mobility, motors for aircraft, which have strict weight restrictions, and subsequently for automobiles, are being made to have higher power densities. Therefore, further improvements in the cooling performance of rotating electric machines are also required in the mobility field.

[0003] A known prior art technique for cooling such a rotating electric machine is described, for example, in Patent Document 1. Patent Document 1 discloses a rotating electric machine including a stator core having a plurality of slots in which stator coils are fitted, and a rotatable rotor arranged on the inner periphery of a hollow portion of the stator core, in which insulating paper is fitted in the slots and around which the stator coils are wound, the length of the insulating paper in the rotational axis direction being longer than the length of the stator core in the rotational axis direction, a rotating shaft cooling oil passage that supplies coolant to the rotor end surface, and an inclined portion that is provided on the end surface of the rotor and guides coolant to a stator coil end that is located outside in the rotational axis direction of the insulating paper that protrudes from the stator core in the rotational axis direction.

[0004] Japanese Patent Application Laid-Open No. 2005-006429

[0005] Direct liquid cooling methods such as oil cooling are effective for improving the cooling performance of rotating electrical machines, but in this method of direct liquid cooling by providing axial through-holes in the rotor core and circulating a refrigerant through these through-holes, a sufficient flow rate of refrigerant must be circulated through the through-holes. For example, in the above-mentioned conventional technology, an axial cooling oil passage is provided in the rotating shaft of the rotor, and two branch oil passages are provided at the axial center of the rotating shaft, extending radially in opposite directions from the cooling oil passage. These oil passages are connected to rotor cooling oil passages provided on the inner diameter side of the rotor core, each of which runs axially in opposite directions. The cooling oil flows radially outward through the end face oil passages at the rotor end, flows out through a jet nozzle, and is thrown out by centrifugal force, colliding with the stator coil ends to cool them.

[0006] On the other hand, cooling the rotor of a rotating electric machine poses the following challenges. For example, in permanent magnet motors, the magnet is generally considered to be the most heat-sensitive part of the rotor. This is because magnets become demagnetized when they become too hot, preventing them from producing the required torque. Therefore, direct liquid cooling of the rotor desirably circulates the coolant (cooling oil) as close to the magnet as possible. However, the rotor magnets and the rotor core surrounding them form a magnetic circuit together with the stator. If the cross-sectional area of ​​the cooling channel is large, it increases the magnetic resistance of the magnetic circuit, increases the magnetic flux density, and magnetic saturation occurs, degrading the performance of the rotating electric machine. Therefore, it is difficult to provide a cooling channel with sufficient cross-sectional area in such a location within the rotor. Furthermore, the cross-sectional area of ​​the cooling channel within the rotor can only be made small, resulting in significant pressure loss when the coolant flows, preventing a sufficient amount of coolant from flowing, thereby hindering improvements in cooling performance and hindering efforts to increase the power density of rotating electric machines.

[0007] In the above-mentioned conventional technology, a flow path passes through the center of the shaft axially, and a radial flow path extends to the inner diameter of the rotor core at the axial center position, with further flow paths formed on both ends in opposite directions in the axial direction, and the refrigerant is scattered to the stator coil ends using the centrifugal force of the rotor. In addition, flow paths with a length half the rotor axial length are provided from the axial center to both ends, which is a configuration that reduces pressure loss compared to providing a single flow path from one end of the rotor to the other end.

[0008] However, in the above-mentioned conventional technology, the purpose is to cool the coil ends at both ends of the stator, and the axial flow passages in the rotor are formed along the inner diameter side of the rotor core, so the cooling effect on the permanent magnets remains questionable. Also, since the inner diameter side of the rotor core is relatively less restricted as a magnetic circuit, even if the cross-sectional area of ​​the flow passage is large, the impact on the performance of the rotating electric machine is small.

[0009] The present invention has been made in consideration of the above, and aims to provide a rotating electric machine and an electric motor system that can improve the cooling performance of the rotor by using a simple method to reduce pressure loss in the cooling flow passages within the rotor and increase the refrigerant flow rate.

[0010] The present application includes multiple means for solving the above-described problems. One example is a rotating electric machine that cools a rotor with a liquid refrigerant, comprising: at least one set of axial passage group consisting of multiple axial passages that are arranged along the axial direction inside the rotor and through which the liquid refrigerant flows; multiple supply passages that are arranged within the rotor or the rotating shaft of the rotor perpendicular to the axial direction, have a cross-sectional area larger than the axial passages, and are connected to the multiple axial passages, respectively, to supply the liquid refrigerant to the multiple axial passages; and discharge passages that are arranged within the rotor or the rotating shaft of the rotor perpendicular to the axial direction, have a cross-sectional area larger than the axial passages, and are connected to the axial passages to discharge the liquid refrigerant from the axial passages, and the multiple axial passages of the axial passage group are arranged at different axial and circumferential positions of the rotor.

[0011] According to the present invention, it is possible to form a flow path for a coolant for cooling a coil while suppressing an increase in the number of manufacturing steps.

[0012] 1 is a diagram showing a schematic view of the overall configuration of a rotating electric machine, and is a cross-sectional view in a plane including the rotation axis of the rotating electric machine. 2 is a diagram showing a schematic view of the overall configuration of a rotating electric machine, and is a cross-sectional view taken along line A-A in FIG. 1. 3 is a diagram showing a schematic view of the overall configuration of an electric motor system having a rotating electric machine and a liquid refrigerant supply / cooling mechanism. 4 is a cross-sectional view in a plane perpendicular to the rotation axis of the rotor.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0014] 1 and 2 are diagrams showing the overall configuration of a rotating electric machine according to this embodiment, with FIG. 1 being a cross-sectional view in a plane including the axis of rotation of the rotating electric machine, and FIG. 2 being a cross-sectional view taken along line AA in FIG.

[0015] 1, the rotating electric machine 100 cools the rotor 2 with a liquid refrigerant, and is an inner rotor type rotating electric machine having a stator 1 disposed on the outer diameter side and a rotor 2 disposed on the inner diameter side of the stator 1 via an air gap 3, with the stator 1 and rotor 2 being coaxially arranged. The rotating electric machine 100 is configured such that the stator 1 and rotor 2 are enclosed in a housing 12.

[0016] The rotor 2 shown in this example is a surface-attached type rotor with multiple permanent magnets 4 attached to its surface, each curved along the outer periphery. The rotor 2 has a rotation axis that is rotated by a shaft 5, and multiple permanent magnets 4 are arranged in a circumferential direction. The rotor 2 is supported by bearings 6 so as to be rotatable relative to the housing 12 (and the stator 1).

[0017] A rotor core 8 inside the rotor 2 is formed with a plurality of axial flow passages 9 along the axial direction, through which a liquid refrigerant flowing from one end of the rotating shaft (here, the upper side in FIG. 1 , i.e., the upstream side) flows to the other end (here, the lower side in FIG. 1 , i.e., the downstream side). The axial flow passages 9 can be formed, for example, by punching holes in advance at corresponding positions in electromagnetic steel sheets, and then laminating the electromagnetic steel sheets to form the rotor core 8. The plurality of axial flow passages 9 belong to at least one axial flow passage group consisting of a plurality of axial flow passages 9 arranged at different positions in the axial and circumferential directions of the rotor. For example, FIG. 1 illustrates one of a plurality of axial flow passage groups (three groups in this embodiment, as shown in FIG. 2 and other figures) that the rotor 2 has, in which the plurality of axial flow passages 9 are arranged at different positions in the axial and circumferential directions.

[0018] That is, a plurality of axial passages 9 are provided in the axial direction, and each axial passage 9 is configured to pass a liquid refrigerant that cools the upper side (upstream side) and the lower side (downstream side) of the rotor 2. A plurality of axial passages 9 are also provided in the circumferential direction, and the upper axial passage 9 and the lower axial passage 9 are arranged at positions offset from each other in the circumferential direction. Note that Figures 1 and 2 illustrate a case where two axial passages 9 that constitute one axial passage group are arranged at different positions in the axial and circumferential directions along the same plane that includes the rotation axis.

[0019] In addition, the multiple axial flow paths 9 that make up the axial flow path group configured as described above can also be said to be one axial flow path divided into multiple parts (for example, into two) in the axial direction, with each part being arranged at a different circumferential position.

[0020] One end of a supply passage 10 that supplies a liquid refrigerant is connected to an upper opening 9a provided at the upper part (upstream end) of each axial flow passage 9. The supply passage 10 is arranged to extend radially inward from the upper opening 9a of the axial flow passage 9, and its inner diameter side end is connected to a shaft center hole 20 provided along the central axis.

[0021] A plurality of first plate blades 15 are radially arranged at the upper end of the rotor 2, extending radially inward from the upper opening 9a of the axial flow passage 9. The upper and radially outer ends of the first plate blades 15 are covered by a first cover 16, and the two members, the first plate blades 15 and the first cover 16, form the outer diameter portion of the supply passage 10. The outer diameter portion of the supply passage 10 is connected to a radial flow passage that extends further radially inward inside the shaft, and forms the entire supply passage 10 together with this flow passage.

[0022] A lower opening 9b provided at the lower part (downstream end) of the upper axial flow passage 9 is connected to a flow passage (discharge passage 11) formed to extend radially within an intermediate plate 21 sandwiched between the laminated steel plates of the rotor core 7. The inner diameter end of the discharge passage 11 formed within the intermediate plate 21 is connected to the upper end of a discharge passage 11 formed downward along the axial direction on the outer surface of the shaft 5. The discharge passage 11, which is a radial flow passage formed within the intermediate plate 21, can be formed, for example, by a structure in which radial plate blades are sandwiched between thin plates from above and below, or by a method in which a radial groove is cut into a solid member.

[0023] A plurality of second plate blades 17 are radially provided at the lower end of the rotor 2, extending radially inward from the lower end of the discharge passage 11. The lower portion and radially inner end of each second plate blade 17 are covered by a second cover 18, and the outer diameter portion of the discharge passage 11 is formed by these two members, the second plate blades 17 and the second cover 18. In other words, the discharge passage 11 formed in the intermediate plate 21, the discharge passage 11 formed on the outer surface of the shaft 5, and the discharge passage 11 formed by the second plate blades 17 and the second cover 18 integrally form the entire discharge passage 11.

[0024] On the other hand, an upper opening 9a of the axial flow passage 9 arranged on the lower side of the rotor 2 is connected to a flow passage (supply passage 10) formed so as to extend radially in an intermediate plate 21 sandwiched between the laminated steel plates of the rotor core 7. Furthermore, the supply passage 10 formed in the intermediate plate 21 has an inner diameter side end connected to an outer diameter side end of the supply passage 10 formed so as to extend radially in the shaft 5 and connected to the shaft center hole 20. Furthermore, a lower opening 9b provided at the lower part (downstream end) of the lower axial flow passage 9 is connected to a discharge passage 11 formed by a plate blade or the like.

[0025] The liquid refrigerant supplied from the inlet 13 at the upper end of the shaft center hole 20 is supplied to the upper opening 9a of the axial flow path 9 via the supply path 10, flows through the axial flow path 9, and is discharged to the outside of the rotor 2 via the lower opening 9b and the discharge path 11. The liquid refrigerant discharged to the outside from the discharge path 11 of the rotor 2 is also discharged to the outside of the rotating electric machine 100 from a discharge port 14 provided in the housing 12 of the rotating electric machine 100.

[0026] The effects of the present embodiment configured as above will be described.

[0027] Generally, when a liquid refrigerant flow path is provided along the axial direction within the rotor of a rotating electric machine, there is a problem in that the cross-sectional area of ​​the flow path cannot be made large enough to satisfy the electrical performance of the rotating electric machine.

[0028] In contrast, in this embodiment, multiple axial flow paths 9, which are flow paths for the liquid refrigerant along the axial direction, are provided and arranged at different axial positions, and the multiple axial flow paths 9 are configured to share the cooling region in the axial direction, so the length of each axial flow path 9 is shortened and pressure loss is reduced. In other words, the refrigerant flow rate can be increased while suppressing an increase in the flow path area, thereby improving cooling performance.

[0029] Furthermore, the supply path 10 and discharge path 11 for the liquid refrigerant connected to the axial flow path 9 can have a large flow path cross-sectional area because they have little effect on the electrical performance of the rotating electrical machine. Therefore, by making the flow path cross-sectional areas of the supply path 10 and the discharge path 11 larger than the flow path cross-sectional area of ​​the axial flow path 9, additional pressure loss other than that of the axial flow path 9 can be reduced. When designing the flow path cross-sectional areas of the supply path 10 and the discharge path 11, the additional pressure loss can be evaluated from the shape including the flow path cross-sectional area, the physical properties of the refrigerant, the flow rate, and other conditions, and therefore it is possible to keep this within an appropriate allowable value.

[0030] Furthermore, by providing independent refrigerant supply paths 10 and discharge paths 11 in each axial flow path 9, the multiple axial flow paths 9 can be made into parallel flow paths. This reduces the pressure loss in the entire flow path of the liquid refrigerant inside the rotor 2 from the liquid refrigerant inlet 13 to the outlet 14, so the discharge pressure of the pump required to pump the refrigerant can be reduced, allowing the pump to be made smaller.

[0031] In other words, because the length of each axial flow passage in the rotor is shortened, pressure loss in the flow passage is reduced, and by making the cross-sectional area of ​​the coolant supply and discharge passages in areas that do not affect the electrical performance of the rotating electric machine larger than that of the axial flow passages in the rotor, additional pressure loss is not increased. This ensures a sufficient coolant flow rate and improves the cooling performance of the rotor. Furthermore, with this structure, because the coolant flow rate can be ensured even with a small cross-sectional area of ​​the axial flow passage, the magnets can be efficiently cooled, particularly when placed axially near magnets with low heat resistance, preventing problems such as demagnetization.

[0032] FIG. 3 is a diagram showing a schematic overall configuration of an electric motor system having a rotating electric machine and a liquid refrigerant supply / cooling mechanism.

[0033] 3, the electric motor system 200 is generally composed of a rotating electric machine 100, an oil pump 120 that supplies a liquid refrigerant to an inlet 13 of the rotating electric machine 100, and a heat exchanger 110 that cools the liquid refrigerant that has cooled the rotating electric machine 100 and been discharged from an outlet 14. The liquid refrigerant that has been pressure-fed to the rotating electric machine 100 by the oil pump 120 and then discharged after cooling the rotating electric machine 100 is cooled by dissipating heat in the heat exchanger 110, and is then pressure-fed by the oil pump 120 and returned to the rotating electric machine 100.

[0034] In an electric motor system incorporating the rotating electric machine 100 of this embodiment, the pressure loss in the refrigerant flow path that cools the inside of the rotor 2 of the rotating electric machine 100 can be reduced, which reduces the discharge pressure required for the oil pump 120 and makes it possible to reduce the size of the oil pump 120. As a result, the overall footprint of the electric motor system 200 can also be reduced.

[0035] <Modification> A modification of this embodiment will be described with reference to FIG.

[0036] This modification shows the case where the present invention is applied to a rotor of an embedded permanent magnet motor that employs a step-wise skew. In this modification, the description of the same configuration as in the other embodiments will be omitted as appropriate.

[0037] FIG. 4 is a cross-sectional view taken along a plane perpendicular to the rotation axis of the rotor.

[0038] As shown in Fig. 4, the rotor 2B has a row-to-row skew structure made up of multiple layers stacked in the axial direction. The row-to-row skew in this embodiment is two-stage, and the permanent magnets 4B1 and 4B2 embedded in the rotor cores 8B1 and 8B2 are offset in the circumferential direction between the upper half (front side of the page in Fig. 4: solid line) and the lower half (back side of the page in Fig. 4: dashed line) of the rotor 2B.

[0039] The axial passage group has axial passages 9B1, 9B2 in the same number as the number of stages of the row-to-row skew, with the upper-stage axial passage 9B1 (indicated by the solid line on the front side of the page in FIG. 4 ) and the lower-stage axial passage 9B2 (indicated by the dashed line on the back side of the page in FIG. 4 ) being arranged in each stage of the row-to-row skew. In this modification, the axial passages 9B1, 9B2 are divided into two, the same number as the number of stages of the row-to-row skew (two stages). Furthermore, the axial passages 9B1, 9B2 are arranged so that their relative positions (radial and circumferential positions) to the corresponding permanent magnets are the same in accordance with the circumferential arrangement of the permanent magnets 4B1, 4B2, and the axial passages 9B1, 9B2 of adjacent upper and lower stages are arranged at positions offset in the circumferential direction by the same amount as the skew angle of the row-to-row skew.

[0040] The other configurations are the same as those of the other embodiments.

[0041] The present modified example configured as above can also achieve the same effects as the other embodiments.

[0042] Furthermore, the cooling performance of each stage of the rotor 2B employing the stage-to-stage skew can be made uniform, thereby reducing unevenness in the temperature distribution within the rotor 2B. Furthermore, the influence of the axial flow passages 9B1, 9B2 on the electromagnetic performance is the same for each skewed stage, so adverse effects due to unintended imbalances, such as increased torque ripple, can be suppressed. The configuration of this modification can be applied to rotors employing any number of stage-to-stage skews.

[0043] <Notes> The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the gist of the present invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiments, and also includes those in which some of the configurations are omitted.

[0044] For example, in this embodiment, an example is given in which the supply passage and the discharge passage are formed by two components, the blade and the cover, but this is not limited to this, and for example, the supply passage and the discharge passage may be formed by cutting the end plate of the rotor.

[0045] Furthermore, in this embodiment, the rotor is constructed by attaching multiple curved permanent magnets along the surface of the rotor or by embedding plate-shaped permanent magnets in the stator core of the rotor, but this is not limited to this, and the present invention can also be applied to rotating electric machines with rotors that use permanent magnets of other shapes and arrangements, such as permanent magnets whose cross-sectional shape in a plane perpendicular to the rotation axis is V-shaped.

[0046] DESCRIPTION OF SYMBOLS 1... stator, 2, 2B... rotor, 3... air gap (air gap), 4, 4B1, 4B2... permanent magnet, 5... shaft, 6... bearing, 7, 8, 8B1, 8B2... rotor core, 9... axial flow passage, 9a... upper opening, 9b... lower opening, 9B1, 9B2... axial flow passage, 10... supply passage, 11... discharge passage, 12... housing, 13... inlet, 14... discharge port, 15... first plate blade, 16... first cover, 17... second plate blade, 18... second cover, 20... shaft center hole, 21... intermediate plate, 100... rotating electric machine, 110... heat exchanger, 120... oil pump, 200... electric motor system

Claims

1. A rotating electric machine that cools a rotor with a liquid refrigerant, comprising: at least one set of axial flow passage groups arranged along the axial direction inside the rotor and consisting of a plurality of axial flow passages through which the liquid refrigerant flows; a plurality of supply passages arranged perpendicular to the axial direction inside the rotor or inside the rotating shaft of the rotor, having a cross-sectional area larger than the axial flow passages, and connected to each of the plurality of axial flow passages to supply the liquid refrigerant to the plurality of axial flow passages; and discharge passages arranged perpendicular to the axial direction inside the rotor or inside the rotating shaft of the rotor, having a cross-sectional area larger than the axial flow passages, connected to the axial flow passages, and discharging the liquid refrigerant from the axial flow passages, characterized in that the multiple axial flow passages of the axial flow passage group are arranged at different positions in the axial and circumferential directions of the rotor.

2. A rotating electric machine as claimed in claim 1, wherein the rotor has a step-wise skew structure made up of a plurality of layers stacked in the axial direction, and the axial flow passage group has axial flow passages in the same number as the number of stages in the step-wise skew, and each axial flow passage of the axial flow passage group is arranged in each stage of the step-wise skew, and the axial flow passage of each stage is arranged circumferentially shifted by a skew angle from the axial flow passage arranged in the stage adjacent to the step-wise skew in the axial direction.

3. An electric motor system comprising: the rotating electric machine according to claim 1 or 2; a heat exchanger that cools the liquid refrigerant that cools the rotating electric machine; and a pump that circulates the liquid refrigerant between the rotating electric machine and the heat exchanger.

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