Motor case

Abstract

To improve cooling performance of a motor and improve rigidity of a motor case.SOLUTION: A motor case (10) includes: an inner case (21) in which a stator (32) of the motor (31) is shrink-fitted; and an outer case (11) in which the inner case is accommodated. A plurality of cooling ribs (22) are provided on an outer circumferential surface of the inner case. A cooling flow path (51) is formed between the inner case and the outer case. At an upstream portion and a downstream portion of the cooling flow path, a plurality of reinforcing ribs (26) with a height lower than a height of the cooling ribs are provided on the outer circumferential surface of the inner case instead of the plurality of cooling ribs.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a motor case. [Background technology]

[0002] Conventionally, a motor case formed by an outer case and an inner case has been known (see, for example, Patent Document 1). The outer case houses the inner case, and the stator of the motor is fixed to the inside of the inner case by shrink fitting. Multiple protrusions protrude from the outer peripheral surface of the inner case, with the tips of the multiple protrusions abutting against the inner surface of the outer case. The multiple protrusions are aligned in the motor axial direction, and each protrusion extends in a circumferential direction perpendicular to the motor axial direction. The multiple protrusions separate the outer case and inner case, forming a cooling flow path through which cooling water flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-36351 Summary of the Invention [Problem to be solved by the invention]

[0004] In the motor case described in Patent Document 1, the stator is shrink-fitted into the inner case, which generates strong shrink-fit stress in the inner case. The presence or absence of protrusions on the inner case creates differences in the case's thickness, resulting in uneven shrink-fit stress on the inner case. Increasing the number of protrusions to improve cooling performance creates areas on the inner case where even greater stress is concentrated. Protrusions are particularly difficult to provide around the coolant inlet and outlet for the motor case, making stress more likely to concentrate there.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a motor case that can improve the cooling performance of the motor and increase its rigidity. [Means for solving the problem]

[0006] One embodiment of the motor case of the present invention comprises an inner case into which a motor stator is shrink-fitted, and an outer case in which the inner case is housed, wherein a plurality of cooling ribs are provided on the outer peripheral surface of the inner case, a cooling flow path is formed between the inner case and the outer case, and at the upstream and downstream portions of the cooling flow path, a plurality of reinforcing ribs lower than the cooling ribs are provided on the outer peripheral surface of the inner case in place of the plurality of cooling ribs, thereby solving the above-mentioned problem. [Effects of the Invention]

[0007] According to one aspect of the present invention, a motor case is provided with multiple reinforcing ribs that are lower than the multiple cooling ribs in the upstream and downstream portions of the cooling flow path, which makes it difficult for the inflow and outflow of cooling water to be obstructed. Furthermore, because ribs are provided not only in areas other than the upstream and downstream portions of the cooling flow path but also in the upstream and downstream portions of the cooling flow path, the difference in wall thickness of the inner case is reduced, thereby alleviating stress concentration in the inner case. Furthermore, the multiple cooling ribs and multiple reinforcing ribs increase the surface area of ​​the inner case that comes into contact with the cooling water, improving the cooling performance of the motor. Even if the density of the cooling ribs is increased, the difference in wall thickness of the inner case does not become too large. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a side view of the inverter-integrated motor of the present embodiment. [Figure 2] FIG. 2 is a front view of the inverter-integrated motor of the present embodiment. [Figure 3] 2 is a cross-sectional view of the inverter-integrated motor of FIG. 1 taken along line AA. [Figure 4] 3 is a cross-sectional view of the inverter-integrated motor of FIG. 2 taken along line BB. [Figure 5] 2A and 2B are a side view and a top view of the inner case of the present embodiment. [Figure 6]FIG. 2 is a perspective view of the heat sink of the present embodiment. [Figure 7] FIG. 10 is a diagram showing stress distribution in an inner case. DETAILED DESCRIPTION OF THE INVENTION

[0009] In one aspect of the present invention, a motor case includes an inner case housed in an outer case, and a motor stator is shrink-fitted into the inner case. A plurality of cooling ribs are provided on the outer peripheral surface of the inner case, and a cooling flow path is formed between the inner case and the outer case. In the upstream and downstream portions of the cooling flow path, a plurality of reinforcing ribs lower than the cooling ribs are provided on the outer peripheral surface of the inner case instead of the cooling ribs, thereby preventing the inflow and outflow of cooling water from being obstructed. Furthermore, since the ribs are provided not only in areas other than the upstream and downstream portions of the cooling flow path but also in the upstream and downstream portions of the cooling flow path, the difference in wall thickness of the inner case is reduced, thereby mitigating stress concentration in the inner case. Furthermore, the plurality of cooling ribs and the plurality of reinforcing ribs increase the surface area of ​​the inner case that comes into contact with the cooling water, improving the cooling performance of the motor. Even if the density of the cooling ribs is increased, the difference in wall thickness of the inner case does not become too large. [Example]

[0010] In a typical motor case for a vehicle motor, an inner case is housed inside an outer case, and a cooling flow path is formed by multiple cooling ribs protruding from the outer peripheral surface of the inner case. A stator is shrink-fitted inside the inner case, causing shrink-fit stress in the inner case. Typically, no ribs are provided at the upstream and downstream portions of the cooling flow path, resulting in stress concentration due to differences in the thickness of the inner case. In particular, increasing the density of the cooling ribs to improve cooling performance increases the stress concentration. Therefore, in this embodiment, the density of the cooling ribs is increased and ribs are also provided at the upstream and downstream portions of the cooling flow path to alleviate the stress concentration.

[0011] The inverter-integrated motor of this embodiment will be described below with reference to the accompanying drawings. Fig. 1 is a side view of the inverter-integrated motor of this embodiment. Fig. 2 is a front view of the inverter-integrated motor of this embodiment. Fig. 3 is a cross-sectional view of the inverter-integrated motor of Fig. 1 taken along line AA. Fig. 4 is a cross-sectional view of the inverter-integrated motor of Fig. 2 taken along line BB. In the following figures, arrow Fr indicates the front, arrow Re indicates the rear, arrow L indicates the left, and arrow R indicates the right.

[0012] As shown in Figures 1 and 2, the inverter-integrated motor 1 has a motor 31 and an inverter 39 installed inside a single motor case 10. The motor case 10 is configured by accommodating an inner case 21 inside an outer case 11. The lower side of the outer case 11 is a cylindrical portion 12 with an open front, and the upper side of the outer case 11 is a box-shaped portion 13 with an open top. The bottom of the box-shaped portion 13 has a large opening, and a heat sink 41 is installed in the opening of the box-shaped portion 13. The opening of the box-shaped portion 13 is closed by the heat sink 41, so that the inside of the box-shaped portion 13 and the inside of the cylindrical portion 12 are separated by the heat sink 41.

[0013] A cylindrical inner case 21 is installed inside the cylindrical portion 12, and a motor 31 is installed inside the inner case 21. A stator 32 of the motor 31 is shrink-fitted inside the inner case 21, and a rotor 33 is rotatably installed inside the stator 32. A motor shaft 34 is fixed to the center of the rotor 33, and the motor shaft 34 protrudes forward from the inner case 21 (motor case 10). An inverter 39 is installed inside the box-shaped portion 13, and the rotation of the motor 31 is controlled by the inverter 39. The inverter 39 is supported on the upper surface of a heat sink 41, and the heat sink 41 cools the inverter 39.

[0014] A cooling flow path 51 (see FIGS. 3 and 4) is formed between the inner case 21 and the outer case 11 so as to surround the motor 31. An inlet pipe 14 and an outlet pipe 15 are attached to one side of the cylindrical portion 12 of the outer case 11. Cooling water is supplied from the inlet pipe 14 to the inlet of the cooling flow path 51, and the cooling water is discharged from the outlet of the cooling flow path 51 to the outlet pipe 15. The cooling flow path 51 is formed around the inner case 21 and below the heat sink 41, and the motor 31 and inverter 39 are effectively cooled while the cooling water passes around the inner case 21 and the underside of the heat sink 41.

[0015] 3 and 4, a plurality of cooling ribs 22 are provided on the outer peripheral surface of the inner case 21, and the top surfaces of the plurality of cooling ribs 22 contact the inner peripheral surface of the cylindrical portion 12 of the outer case 11. A heat sink 41 is provided in the opening at the top of the cylindrical portion 12, and the underside of the heat sink 41 faces the outer peripheral surface of the inner case 21. A plurality of cooling fins 42 are provided on the underside of the heat sink 41, and the top surfaces of the plurality of cooling fins 42 protrude toward the inner case 21. The plurality of cooling ribs 22 form a cooling flow path 51 around the inner case 21, and the plurality of cooling ribs 22 and the plurality of cooling fins 42 form a common flow path 52 in part of the cooling flow path 51.

[0016] Note that most of the cooling ribs 22 extend along the circumferential direction of the inner case 21, but some of the cooling ribs 22 that face the heat sink 41 extend along the axial direction of the inner case 21. Also, most of the cooling fins 42 extend along the circumferential direction of the inner case 21, but some of the cooling fins 42 extend along the axial direction of the inner case 21. These some of the cooling ribs 22 and some of the cooling fins 42 are arranged with misalignment in the circumferential direction. Therefore, in the common flow path 52 between the inverter 39 and the motor 31, coolant flows back and forth between the inner case 21 and the heat sink 41.

[0017] In this way, a common flow path 52 that simultaneously cools the motor 31 and inverter 39 is formed between the inner case 21 and the heat sink 41. Separate flow paths are no longer necessary for the inner case 21 and the heat sink 41, and the motor 31 and inverter 39 are brought closer together, thereby reducing the size of the motor case 10. The common flow path 52 is divided into inter-rib flow paths 53 on the inner case 21 side and inter-fin flow paths 56 on the heat sink 41 side. In the common flow path 52, the cooling performance of the motor 31 and inverter 39 is adjusted by the heights of the multiple cooling ribs 22 and multiple cooling fins 42, and the height dimension of the flow path does not become larger than necessary, thereby reducing the size of the motor case 10.

[0018] A partition wall 25 that separates the cooling flow path 51 into upper and lower sections is provided on one side of the outer peripheral surface of the inner case 21. The partition wall 25 extends along the axial direction of the inner case 21, and the top surface of the partition wall 25 contacts the inner peripheral surface of the tubular portion 12. The inlet pipe 14 is located above the partition wall 25, and the side above the partition wall 25 is the upstream section of the cooling flow path 51. The outlet pipe 15 is located below the partition wall 25, and the side below the partition wall 25 is the downstream section of the cooling flow path 51. In this way, the cooling flow path 51 is formed in which the cooling water flows clockwise in a cross-sectional view (rear view).

[0019] The inner case and the heat sink will be described with reference to Figures 5 and 6. Figure 5 is a side view and a top view of the inner case of this embodiment, and Figure 6 is a perspective view of the heat sink of this embodiment.

[0020] As shown in Figures 5(A) and 5(B), a plurality of cooling ribs 22 are provided on the outer peripheral surface of the inner case 21. The plurality of cooling ribs 22 includes a plurality of vertical ribs 23 aligned in the motor axial direction and a plurality of horizontal ribs 24 aligned in a circumferential direction perpendicular to the motor axial direction. The plurality of vertical ribs 23 extend in the circumferential direction, and the plurality of horizontal ribs 24 are perpendicular to the plurality of vertical ribs 23. The plurality of vertical ribs 23 are formed around substantially the entire circumference of the inner case 21 except for the vicinity of the inlet 16 and the outlet 17 of the inner case 21, and the plurality of horizontal ribs 24 are formed only on the upper part of the inner case 21 facing the heat sink 41 (see Figure 6).

[0021] The inner case 21 is formed with a plurality of inter-rib flow paths 53, branch flow paths 54, and confluence flow paths 55 as cooling flow paths 51. The plurality of inter-rib flow paths 53 allow cooling water to circulate along the longitudinal ribs 23, and the entire circumference of the motor 31 (see FIG. 2) is cooled via the inner case 21. At the upstream portion of the cooling flow path 51, branch flow paths 54 extend in the motor axial direction, and cooling water that has entered from the inlet 16 is branched by the branch flow paths 54 into the plurality of inter-rib flow paths 53. At the downstream portion of the cooling flow path 51, a confluence flow path 55 extends in the motor axial direction, and the cooling water from the plurality of inter-rib flow paths 53 is joined by the confluence flow path 55 and discharged from the outlet 17.

[0022] The vertical ribs 23 and horizontal ribs 24 are formed at a constant height that is the same as the outermost diameter of the inner case 21. By making the vertical ribs 23 and horizontal ribs 24 constant in height, the cross-sectional area of ​​the flow path around the motor is constant, stabilizing cooling of the motor 31, which has a large amount of heat. In the upper part of the inner case 21, the vertical ribs 23 and horizontal ribs 24 are arranged in a lattice pattern, and the multiple inter-rib flow paths 53 are partially blocked by the multiple horizontal ribs 24. The upper part of the inner case 21 faces the heat sink 41, and the interrupted parts of the multiple inter-rib flow paths 53 communicate with the multiple inter-fin flow paths 56 (see FIG. 6) on the heat sink 41 side.

[0023] In the branch flow passages 54 and the merging flow passages 55, a plurality of reinforcing ribs 26 that are lower than the vertical ribs 23 are provided on the outer peripheral surface of the inner case 21 instead of the vertical ribs 23. The plurality of reinforcing ribs 26 extend circumferentially, continuing from the vertical ribs 23, and are formed to have the same width as the vertical ribs 23. Because the inner case 21 is provided with ribs around the entire periphery, the difference in thickness between the inner case 21 with and without ribs is reduced, and stress concentration due to shrink fitting of the stator 32 is alleviated. In addition, the surface area of ​​the inner case 21 is increased by the plurality of reinforcing ribs 26, improving the cooling performance of the motor 31.

[0024] By forming the multiple reinforcing ribs 26 low, a sufficient gap is secured between the multiple reinforcing ribs 26 and the cylindrical portion 12 of the outer case 11, and the flow of cooling water in the branch flow passages 54 and the merging flow passages 55 is less likely to be obstructed by the reinforcing ribs 26. The top surfaces of the multiple vertical ribs 23 and the multiple horizontal ribs 24 are formed flat in a side view so as to contact the inner circumferential surface of the outer case 11, and the top surfaces of the multiple reinforcing ribs 26 are formed rounded in a cross-sectional view so as not to obstruct the flow of cooling water. The flow passage width of the multiple inter-rib flow passages 53 is formed to be equal to or less than the width of the vertical ribs 23. Increasing the number of flow passages in the inter-rib flow passages 53 improves cooling performance, and it is easier to maintain the rigidity of the inner case 21 even when the number of flow passages is increased.

[0025] A partition wall 25 extending in the motor axial direction is provided on the outer peripheral surface of the inner case 21, and a branch flow passage 54 and a junction flow passage 55 are adjacent to each other in the circumferential direction, with the partition wall 25 sandwiched between them. Cooling water flows from the branch flow passage 54 on the upper side of the partition wall 25 through multiple inter-rib flow passages 53 to the junction flow passage 55 on the lower side of the partition wall 25, thereby cooling the entire circumference of the motor 31. An inlet 16 is formed in the cylindrical portion 12 of the outer case 11 (see FIG. 1 ) at one end in the motor axial direction, and an outlet 17 is formed at the other end in the motor axial direction. One end of the branch flow passage 54 in the motor axial direction is connected to the inlet 16, and the other end of the junction flow passage 55 in the motor axial direction is connected to the outlet 17.

[0026] The partition wall 25 is formed in a crank shape so that the flow path width of the branch flow path 54 is wider at a location corresponding to the inlet 16 and the flow path width of the confluence flow path 55 is wider at a location corresponding to the outlet 17. More specifically, the wide portion of the branch flow path 54 is adjacent to the narrow portion of the confluence flow path 55 in the circumferential direction, with the partition wall 25 in between, and the narrow portion of the branch flow path 54 is adjacent to the wide portion of the confluence flow path 55 in the circumferential direction, with the partition wall 25 in between. Because the flow path widths of the branch flow path 54 and the confluence flow path 55 are wider near the inlet 16 and the outlet 17, the inflow and outflow of coolant are less likely to be obstructed even if multiple reinforcing ribs 26 are provided in the branch flow path 54 and the confluence flow path 55.

[0027] The wide portions of the branch flow passages 54 are adjacent to the narrow portions of the merging flow passages 55, and the narrow portions of the branch flow passages 54 are adjacent to the wide portions of the merging flow passages 55, so that the total area of ​​the branch flow passages 54 and the merging flow passages 55, i.e., the area A1 where the multiple reinforcing ribs 26 are formed, is narrowed in the circumferential direction. The narrowing of the area A1 where the multiple reinforcing ribs 26 are formed reduces differences in thickness of the inner case 21. The branch flow passages 54 and the merging flow passages 55 are formed point-symmetrically with respect to the center O of the partition wall 25. The symmetrical shapes of the branch flow passages 54 and the merging flow passages 55 alleviate stress concentration. The flow deviation between the inlet 16 and the outlet 17 is reduced, so that even if the partition wall 25 is crank-shaped, the coolant flows smoothly and cooling performance is not impaired.

[0028] The flow path width of the branch flow path 54 narrows at a location spaced from the inlet 16 on the other side in the motor axial direction, and the flow path width of the confluence flow path 55 narrows at a location spaced from the outlet 17 on one side in the motor axial direction. The narrow portion of the branch flow path 54 is located directly beside the inlet 16, and the outlet 17 is located directly beside the narrow portion of the outlet 17. Cooling water flows straight from the inlet 16 to the narrow portion of the branch flow path 54, and cooling water also flows straight from the narrow portion of the confluence flow path 55 to the outlet 17. Therefore, even though the partition wall 25 is crank-shaped, the branching to the multiple inter-rib flow paths 53 and the merging from the multiple inter-rib flow paths 53 are not obstructed.

[0029] As shown in Fig. 6, a plurality of cooling fins 42 are provided on the underside of the heat sink 41. The plurality of cooling fins 42 includes a plurality of vertical fins 43 aligned in the motor axial direction and a plurality of horizontal fins 44 aligned in a direction perpendicular to the motor axial direction. The plurality of vertical fins 43 extend along the plurality of vertical ribs 23, and the plurality of horizontal fins 44 are perpendicular to the plurality of vertical fins 43. The heat sink 41 is formed with a plurality of inter-fin flow paths 56 as cooling flow paths 51. The inter-fin flow paths 56 allow cooling water to circulate along the vertical fins 43, and the entire surface of the inverter 39 (see Fig. 2) is cooled via the heat sink 41.

[0030] The multiple vertical fins 43 are formed to increase in height from the middle toward both ends in the extension direction so as to fit along the outer peripheral surface of the inner case 21 (see FIG. 5). By fitting the top surfaces of the multiple vertical fins 43 along the outer peripheral surface of the inner case 21, the heat sink 41 is brought closer to the inner case 21, thereby reducing the size of the motor case 10. The multiple vertical fins 43 and multiple horizontal fins 44 are arranged in a lattice pattern, and the multiple inter-fin flow paths 56 are partially blocked by the multiple horizontal fins 44. The interrupted portions of the multiple inter-fin flow paths 56 communicate with the multiple inter-rib flow paths 53 (see FIG. 5). The height of the multiple horizontal fins 44 is the same as the multiple vertical fins 43 at the intersections with the vertical fins 43.

[0031] The reinforcement structure of the inner case will be described with reference to Fig. 7. Fig. 7 is a diagram showing the stress distribution of the inner case. Fig. 7(A) shows the stress distribution of the inner case of the comparative example, and Fig. 7(B) shows the stress distribution of the inner case of the present example.

[0032] 7(A), in the inner case 61 of the comparative example, a plurality of inter-rib flow paths 63 are formed by a plurality of cooling ribs 62, and branch flow paths 64 and merging flow paths 65 are formed upstream and downstream of the plurality of inter-rib flow paths 63. Unlike the inner case 21 of the present embodiment, no ribs are provided in the branch flow paths 64 and the merging flow paths 65. Therefore, there is a large difference in thickness of the inner case 61 between the locations where the plurality of cooling ribs 62 are formed and the locations where the branch flow paths 64 and the merging flow paths 65 are formed. If a stator is shrink-fitted into the inner case 61, stress will concentrate in the branch flow paths 64 and the merging flow paths 65, and there is a risk that the maximum stress value will exceed the material yield point.

[0033] 7(B), in this embodiment, not only are multiple cooling ribs 22 provided on the outer peripheral surface of the inner case 21, but multiple reinforcing ribs 26 are also provided in the branch flow passages 54 and the merging flow passages 55. The multiple reinforcing ribs 26 connect the multiple cooling ribs 22 to the partition wall 25, and the difference in thickness of the inner case 21 is small at the locations where the multiple cooling ribs 22 are formed and at the locations where the branch flow passages 54 and the merging flow passages 55 are formed. When the stator 32 (see FIG. 2) is shrink-fitted into the inner case 21, stress concentration in the branch flow passages 54 and the merging flow passages 55 is alleviated. Although stress increases at both ends of the multiple reinforcing ribs 26, the maximum stress value is kept below the material yield point.

[0034] Furthermore, the reinforcing ribs 26 are formed lower than the cooling ribs 22, and the top surfaces of the reinforcing ribs 26 are rounded. This makes it difficult for the reinforcing ribs 26 to obstruct the flow of cooling water in the branch flow passages 54 and the merging flow passages 55. The reinforcing ribs 26 and the cooling ribs 22 are connected smoothly via slopes, and the reentrant corners of the reinforcing ribs 26 and the partition wall 25 are rounded. This reduces the abrupt shape changes between the reinforcing ribs 26 and the cooling ribs 22 and between the reinforcing ribs 26 and the partition wall 25, thereby mitigating stress concentration.

[0035] As described above, according to the inverter-integrated motor 1 of this embodiment, the inflow and outflow of cooling water are less likely to be obstructed by providing the multiple reinforcing ribs 26, which are shorter than the multiple cooling ribs 22, in the branch flow passages 54 and the junction flow passage 55 of the cooling flow passage 51. Furthermore, since the multiple reinforcing ribs 26 are provided in the branch flow passages 54 and the junction flow passage 55, the difference in thickness of the inner case 21 is reduced, thereby mitigating stress concentration in the inner case 21. Furthermore, the multiple cooling ribs 22 and the multiple reinforcing ribs 26 increase the surface area of ​​the inner case 21 that comes into contact with the cooling water, improving the cooling performance of the motor 31. Even if the density of the cooling ribs 22 is increased, the difference in thickness of the inner case 21 does not become too large.

[0036] In this embodiment, the outer case has a cylindrical portion and a box-shaped portion, but the outer case may be formed to be able to house the inner case.

[0037] In addition, in this embodiment, a plurality of vertical ribs and a plurality of horizontal ribs are provided on the outer peripheral surface of the inner case as a plurality of cooling ribs, but it is sufficient if a plurality of ribs are provided on the outer peripheral surface of the inner case. For example, the outer peripheral surface of the inner case may be provided with only vertical ribs or only horizontal ribs as a plurality of cooling ribs.

[0038] In addition, in this embodiment, a plurality of vertical fins and a plurality of horizontal fins are provided as the plurality of cooling fins on the underside of the heat sink, but it is sufficient that a plurality of fins are provided on the underside of the heat sink. For example, the underside of the heat sink may be provided with only vertical fins or only horizontal fins as the plurality of cooling fins.

[0039] In addition, in this embodiment, the plurality of reinforcing ribs are connected to the plurality of longitudinal ribs, but the plurality of reinforcing ribs may be separated from the plurality of longitudinal ribs.

[0040] Furthermore, in this embodiment, the partition wall is formed in a crank shape, but the partition wall may be formed in any shape as long as it separates the branch flow channel and the merging flow channel.

[0041] Furthermore, the inverter-integrated motor of this embodiment may be used in other devices as well as in vehicles.

[0042] As described above, the first aspect includes an inner case (21) to which a stator (32) of a motor (31) is shrink-fitted, and an outer case (11) in which the inner case is housed. The inner case has a plurality of cooling ribs (22) on its outer peripheral surface. A cooling flow path (51) is formed between the inner case and the outer case. In place of the cooling ribs, the inner case has a plurality of reinforcing ribs (26) lower than the cooling ribs on its outer peripheral surface at the upstream and downstream portions of the cooling flow path. With this configuration, the provision of the reinforcing ribs lower than the cooling ribs at the upstream and downstream portions of the cooling flow path reduces the obstruction of the inflow and outflow of cooling water. Furthermore, since the ribs are provided not only in the region excluding the upstream and downstream portions of the cooling flow path but also at the upstream and downstream portions of the cooling flow path, the difference in wall thickness of the inner case is reduced, thereby mitigating stress concentration in the inner case. Furthermore, the cooling ribs and reinforcing ribs increase the surface area of ​​the inner case that comes into contact with the cooling water, improving the cooling performance of the motor. Even if the density of the cooling ribs is increased, the difference in wall thickness of the inner case does not become too large.

[0043] In a second aspect, in the first aspect, multiple cooling ribs are aligned in the motor axial direction and extend circumferentially, and the cooling flow path includes multiple inter-rib flow paths (53) that circulate cooling water along the multiple cooling ribs, a branch flow path (54) that branches cooling water to the multiple inter-rib flow paths at an upstream portion of the cooling flow path, and a confluence flow path (55) that confluences cooling water from the multiple inter-rib flow paths at a downstream portion of the cooling flow path, and multiple reinforcing ribs are provided on the outer peripheral surface of the inner case in the branch flow path and the confluence flow path. With this configuration, the cooling performance of the motor is improved by circulating cooling water through the multiple inter-rib flow paths. By forming the multiple reinforcing ribs low, the flow of cooling water in the branch flow path and the confluence flow path is less likely to be obstructed by the multiple reinforcing ribs.

[0044] In the third aspect, in the second aspect, a partition wall (25) extending in the axial direction of the motor is provided on the outer peripheral surface of the inner case, and the branch flow passage and the merging flow passage are adjacent to each other in the circumferential direction with the partition wall in between. With this configuration, the motor can be cooled all around.

[0045] In a fourth aspect, in the third aspect, the outer case has an inlet (16) at one end in the motor shaft direction and an outlet (17) at the other end in the motor shaft direction, and the partition wall is formed in a crank shape so that the flow path width of the branch flow path is wide at a location corresponding to the inlet and the flow path width of the merging flow path is wide at a location corresponding to the outlet. With this configuration, the flow path widths of the branch flow path and the merging flow path are widened, so that the inflow and outflow of coolant are less likely to be obstructed even if multiple reinforcing ribs are provided in the branch flow path and the merging flow path. Because the branch flow path and the merging flow path are separated by a crank-shaped partition wall, the area where the multiple reinforcing ribs are formed can be narrowed, thereby reducing differences in wall thickness of the inner case.

[0046] In the fifth aspect, in the fourth aspect, the branch flow passage and the merging flow passage are formed symmetrically with respect to the center of the crank-shaped partition wall. With this configuration, the shapes of the branch flow passage and the merging flow passage are symmetrical, which alleviates stress concentration. This reduces the deviation of the flow at the inlet and outlet, and even though the partition wall is crank-shaped, the coolant flows smoothly, and cooling performance is not impaired.

[0047] In a sixth aspect, in the fourth or fifth aspect, the flow path width of the branch flow path narrows at a location away from the inlet on the other side in the motor axial direction, and the flow path width of the confluence flow path narrows at a location away from the outlet on one side in the motor axial direction. With this configuration, cooling water flows straight from the inlet to the narrow part of the branch flow path, and also flows straight from the narrow part of the confluence flow path to the outlet. Therefore, even if the partition wall is crank-shaped, the branching to the multiple inter-rib flow paths and the merging from the multiple inter-rib flow paths are not obstructed.

[0048] A seventh aspect is any one of the first to sixth aspects, in which the cooling ribs and the reinforcing ribs are formed with the same width. This configuration reduces the difference in thickness of the inner case. The contact area between the reinforcing ribs and the cooling water increases, improving cooling performance.

[0049] In an eighth aspect, in any one of the first to seventh aspects, the width of the inter-rib flow passages is set equal to or less than the width of the cooling ribs. This configuration allows the number of inter-rib flow passages to be increased, improving cooling performance. Even if the number of inter-rib flow passages is increased, the rigidity of the inner case can be easily maintained.

[0050] A ninth aspect is any one of the first to eighth aspects, wherein the top surfaces of the plurality of reinforcing ribs are rounded. With this configuration, even if the plurality of reinforcing ribs are provided in the branch flow path and the merging flow path, the flow of cooling water is unlikely to be obstructed.

[0051] Although the present embodiment has been described, other embodiments may be made by combining the above-described embodiments and modifications in whole or in part.

[0052] Furthermore, the technology of the present invention is not limited to the above-described embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea. [Explanation of symbols]

[0053] 10: Motor case 11: Outer case 16:Inlet 17: Outlet 21: Inner case 22: Cooling rib 25: Partition wall 26: Reinforcing rib 31: Motor 32: Stator 51: Cooling channel 53: Flow passage between ribs 54: Branch flow path 55: Confluence

Claims

1. an inner case to which a motor stator is shrink-fitted; an outer case in which the inner case is housed, A plurality of cooling ribs are provided on the outer peripheral surface of the inner case, A cooling passage is formed between the inner case and the outer case, A motor case characterized in that, in the upstream and downstream portions of the cooling flow path, a plurality of reinforcing ribs lower than the cooling ribs are provided on the outer peripheral surface of the inner case instead of the plurality of cooling ribs.

2. the plurality of cooling ribs are aligned in the motor axial direction and extend in the circumferential direction, the cooling flow path includes a plurality of inter-rib flow paths that circulate cooling water along the plurality of cooling ribs, a branch flow path that branches the cooling water to the plurality of inter-rib flow paths at an upstream portion of the cooling flow path, and a confluence flow path that confluences the cooling water from the plurality of inter-rib flow paths at a downstream portion of the cooling flow path, 2. The motor case according to claim 1, wherein the plurality of reinforcing ribs are provided on an outer peripheral surface of the inner case in the branch flow passage and the merging flow passage.

3. a partition wall extending in the motor axial direction is provided on the outer peripheral surface of the inner case; 3. The motor case according to claim 2, wherein the branch flow passage and the merging flow passage are adjacent to each other in the circumferential direction with the partition wall interposed therebetween.

4. The outer case has an inlet formed at one end in the motor shaft direction and an outlet formed at the other end in the motor shaft direction.

4. The motor case according to claim 3, wherein the partition wall is formed in a crank shape so that the flow path width of the branch flow path is wider at a location corresponding to the inlet, and the flow path width of the merged flow path is wider at a location corresponding to the outlet.

5. 5. The motor case according to claim 4, wherein the branch flow passage and the merging flow passage are formed symmetrically with respect to a center of the crank-shaped partition wall.

6. 5. The motor case according to claim 4, wherein the flow path width of the branch flow path narrows at a location spaced from the inlet on the other side of the motor shaft direction, and the flow path width of the confluence flow path narrows at a location spaced from the outlet on one side of the motor shaft direction.

7. 3. The motor case according to claim 1, wherein the plurality of cooling ribs and the plurality of reinforcing ribs are formed to have the same width.

8. 3. The motor case according to claim 1, wherein the width of the inter-rib flow passages is equal to or smaller than the width of the cooling ribs.

9. 3. The motor case according to claim 1, wherein the top surfaces of the plurality of reinforcing ribs are rounded.

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