Fluid machine

Abstract

A fluid machine according to the present disclosure comprises a stator having a central axis, and a housing including an inner peripheral surface that contacts an outer peripheral surface of the stator. A groove extending in a direction including an axial component of the central axis is formed on either the outer peripheral surface or the inner peripheral surface. The groove includes a bottom surface and a pair of side surfaces extending from the bottom surface to the peripheral surface so as to separate from each other in the circumferential direction as the side surfaces approach the peripheral surface. In a cross section of the groove perpendicular to the central axis, each side surface of the pair of side surfaces is represented as a linear part including at least one straight line or curved line, which joins a start point connected to the bottom surface and an end point connected to the peripheral surface. When a tangent line having any point of the linear part as a contact point is split into a circumferential direction component extending from the contact point in the circumferential direction and a radial direction component extending in the radial direction from the contact point, a tangent line of each contact point from the start point to the end point includes at least the circumferential direction component of the circumferential direction component and the radial direction component.

Description

fluid machinery

[0001] The present disclosure relates to a fluid machine.

[0002] For example, in fluid machines such as blowers or compressors, a motor may be used as a drive source for an impeller. In this case, it is necessary to cool the motor, which generates heat during operation of the fluid machine. Known technologies for cooling motors include those described in Patent Documents 1 to 3. For example, in the fluid machine described in Patent Document 1, a cooling fan is provided on the rotating shaft of the impeller, and this cooling fan causes cooling air to flow inside the housing. This cooling air cools the stator, which is the main heat source. Furthermore, in this fluid machine, a cooling groove is formed between the housing and the stator, and the cooling air flowing inside the housing also flows into the cooling groove. The cooling air flowing into the cooling groove directly cools the stator.

[0003] International Publication No. 2019 / 049202 Japanese Patent Application Laid-Open No. 2012-90411 Japanese Patent Application Laid-Open No. 8-130856

[0004] In the above-described fluid machine, the housing and the stator are fixed to each other by an interference fit, such as shrink fitting, cooling fitting, or press fitting. As a result, stress is generated between the housing and the stator. This stress tends to concentrate around the cooling grooves formed between the housing and the stator. To withstand this stress concentration, it is conceivable to increase the thickness of the surrounding area of ​​the grooves, for example. However, this approach makes it difficult to reduce the weight of the fluid machine.

[0005] The present disclosure describes a fluid machine that can achieve weight reduction.

[0006] A fluid machine according to one embodiment of the present disclosure includes a stator having a central axis and a housing including an inner peripheral surface in contact with the outer peripheral surface of the stator. A groove extending in a direction including an axial component of the central axis and through which a coolant capable of cooling the stator passes is formed in one of the outer peripheral surface and the inner peripheral surface. The groove includes a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis, and a pair of side surfaces disposed opposite each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to move away from each other in the circumferential direction as they approach the peripheral surface. In a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a starting point connected to the bottom surface and an ending point connected to the peripheral surface. When a tangent line connecting any point on the linear portion is decomposed into a circumferential component extending circumferentially from the tangent point and a radial component extending radially from the tangent point, the tangent line at each tangent point from the starting point to the ending point includes at least the circumferential component of the circumferential component and the radial component.

[0007] According to some aspects of the present disclosure, a fluid machine capable of achieving weight reduction is provided.

[0008] FIG. 1 is a cross-sectional view of a fluid machine according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the fluid machine taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view of an enlarged portion A1 of FIG. 2. FIG. 4 is a cross-sectional view of an enlarged portion A2 of FIG. 3. FIG. 5 is a cross-sectional view for explaining the effect achieved by the fluid machine of FIG. 1. FIG. 6(a) is a cross-sectional view of an enlarged portion of a fluid machine according to Modification 1. FIG. 6(b) is a cross-sectional view of an enlarged portion of a fluid machine according to Modification 2. FIG. 7 is a cross-sectional view of a fluid machine according to a comparative example. FIG. 8(a) is a cross-sectional view of an enlarged portion of the fluid machine of FIG. 7. FIG. 8(b) is a cross-sectional view of a state in which rounding has been applied to the corners of the groove of FIG. 8(a).

[0009] A fluid machine according to one embodiment of the present disclosure includes a stator having a central axis and a housing including an inner peripheral surface in contact with the outer peripheral surface of the stator. A groove extending in a direction including an axial component of the central axis and through which a coolant capable of cooling the stator passes is formed in one of the outer peripheral surface and the inner peripheral surface. The groove includes a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis, and a pair of side surfaces disposed opposite each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to move away from each other in the circumferential direction as they approach the peripheral surface. In a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a starting point connected to the bottom surface and an ending point connected to the peripheral surface. When a tangent line connecting any point on the linear portion is decomposed into a circumferential component extending circumferentially from the tangent point and a radial component extending radially from the tangent point, the tangent line at each tangent point from the starting point to the ending point includes at least the circumferential component of the circumferential component and the radial component.

[0010] In the above-described fluid machine, when the housing and the stator are fixed to each other by an interference fit, large circumferential stress acts on the housing and the stator. Such circumferential stress tends to concentrate in areas where the cross-sectional area changes abruptly at each circumferential position when the housing or the stator is cut along a plane along the circumferential direction. For example, when a rectangular groove is formed in the housing or the stator, abrupt changes in cross-sectional area tend to occur in peripheral areas such as corners of the groove. In contrast, in the above-described fluid machine, a pair of side surfaces of the groove formed on one of the inner circumferential surface of the housing and the outer circumferential surface of the stator extend from the bottom surface to the circumferential surface so as to become more distant from each other in the circumferential direction as they approach the circumferential surface. Furthermore, each side surface is represented as a linear portion including at least one straight line or curve connecting a starting point connected to the bottom surface and an end point connected to the circumferential surface. Taking any point on the linear portion as a tangent point, the tangent line at each tangent point from the starting point to the end point includes at least a circumferential component among the circumferential and radial components. In other words, the linear portion does not include a portion extending only radially from the arbitrary point. Such a portion extending only in the radial direction can cause a sudden change in the cross-sectional area at each position when the peripheral portion of the groove is cut along a plane along the circumferential direction. Therefore, if the linear portion constituting the side surface of the groove does not include a portion extending only in the radial direction, the sudden change in the cross-sectional area of ​​the peripheral portion of the groove can be suppressed. In other words, the change in the cross-sectional area of ​​the peripheral portion of the groove can be made gentler. This suppresses the occurrence of large stress concentrations in the peripheral portion of the groove. As a result, the housing or stator does not need to be excessively thick to withstand stress concentrations in the peripheral portion of the groove, thereby enabling the weight of the fluid machine to be reduced.

[0011] The peripheral surface may be the inner peripheral surface of the housing. When the housing and the stator are fixed to each other by an interference fit, tensile stress acting on the housing is particularly likely to be large. Therefore, when a groove is formed on the inner peripheral surface of the housing, large stress concentrations are likely to occur in the areas surrounding the groove. In contrast, with the above configuration, as described above, it is possible to effectively suppress the occurrence of large stress concentrations in the areas surrounding the groove, thereby effectively achieving the above-mentioned effects.

[0012] The thermal expansion coefficient of the housing may be greater than that of the stator. In this case, when the housing and the stator are fixed together by an interference fit, such as shrink fitting or cold fitting, a large tensile stress is likely to act on the housing due to the difference between the thermal expansion coefficients of the housing and the stator. As a result, a large stress concentration is likely to occur around the grooves formed on the inner circumferential surface of the housing. In contrast, with the above configuration, as described above, the occurrence of a large stress concentration around the grooves can be more effectively suppressed, thereby more effectively achieving the above-mentioned effects.

[0013] In the cross section of the groove, the distance between the end points of a pair of side surfaces along the circumferential direction may be greater than the distance between the start points of the pair of side surfaces along the circumferential direction. Because the outer peripheral surface of the stator is exposed between the end points of the pair of side surfaces of the groove, the cooling medium passing through the groove contacts the outer peripheral surface of the stator. Therefore, by ensuring a large distance between the end points of the pair of side surfaces, as in the above configuration, the contact area of ​​the outer peripheral surface of the stator with the cooling medium, i.e., the heat transfer area, can be ensured. This increases the cooling efficiency of the stator by the cooling medium.

[0014] In the cross section of the groove, the linear portion represented as the side surface may include a straight line extending linearly along a direction including a circumferential component, which makes it easier to form the side surface of the groove compared to when the linear portion is composed only of complex curves.

[0015] The length of the circumferential component of the tangent of each contact point from the start point to the end point may be longer than the length of the radial component of the tangent. In this case, in the cross section of the groove, the linear portion as the side surface extends in the circumferential direction rather than the radial direction, so that the change in cross-sectional area of ​​the peripheral portion of the groove at each position along the circumferential direction can be made more gradual. This makes it possible to more effectively suppress the occurrence of large stress concentrations in the peripheral portion of the groove.

[0016] In a cross section of the groove, when a straight line connecting the center between the start points of a pair of side surfaces along the circumferential direction and the central axis is taken as a center line, the pair of side surfaces may be formed to be symmetrical with respect to the center line. In this case, stress in the peripheral portion of the groove can be evenly distributed, thereby more effectively suppressing large stress concentrations in the peripheral portion of the groove.

[0017] A fluid machine according to another aspect of the present disclosure includes a stator having a central axis and a housing including an inner peripheral surface in contact with the outer peripheral surface of the stator. A groove extending in a direction including an axial component of the central axis and through which a coolant capable of cooling the stator passes is formed in one of the outer peripheral surface and the inner peripheral surface. The groove includes a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis, and a pair of side surfaces disposed opposite each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to move away from each other in the circumferential direction as they approach the peripheral surface. In a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a start point connected to the bottom surface and an end point connected to the peripheral surface. When an imaginary line connecting the start point and the end point is decomposed into a circumferential component extending circumferentially from the start point and a radial component extending radially from the start point, the length of the circumferential component of the imaginary line is longer than the length of the radial component of the imaginary line.

[0018] The above-described fluid machine also achieves the same effects as those described above. That is, the above-described fluid machine can suppress the occurrence of large stress concentrations in the peripheral portions of the grooves. As a result, the housing or stator does not need to be excessively thick to withstand the stress concentrations in the peripheral portions of the grooves, thereby enabling the weight of the fluid machine to be reduced. Furthermore, in the above-described fluid machine, the length of the circumferential component of the imaginary line connecting the start point and the end point is longer than the length of the radial component of the imaginary line. In this case, the side surface of the groove can be configured to extend in the circumferential direction rather than the radial direction, thereby making it possible to more gently change the cross-sectional area of ​​the peripheral portions of the grooves at each position along the circumferential direction. This more effectively suppresses the occurrence of large stress concentrations in the peripheral portions of the grooves.

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated description will be omitted.

[0020] The fluid machine 1 shown in Fig. 1 is, for example, a centrifugal blower. The fluid machine 1 may also be, for example, an air-cooled electric blower that draws in air and sends it out at a predetermined pressure. The fluid machine 1 has an air intake port at its tip end. The fluid machine 1 includes an impeller housing 3 that houses an impeller 2, and a motor housing 6 (housing) that houses a motor 10 that serves as a rotary drive unit for rotating the impeller 2. The motor 10 includes a rotor 8a fixed to a shaft 8 and a stator 4 that surrounds the rotor 8a.

[0021] Heat dissipation fins 7 are formed on the outer peripheral surface of the motor housing 6. The motor housing 6 includes a first end 61 on the tip side in the axial direction D1 and a second end 62 on the base side. The motor housing 6 includes an insertion hole 6a extending in the axial direction D1 between the first end 61 and the second end 62. A shaft 8 made of, for example, stainless steel is inserted into the insertion hole 6a of the motor housing 6. The axial direction D1 is the direction in which the central axis X of the cylindrical stator 4 extends. The central axis X is an axis that passes through the center of the stator 4. The central axis X coincides with the rotation axis of the shaft 8.

[0022] The shaft 8 is supported by a first bearing 18 provided inside the motor housing 6 near the first end 61, and a second bearing 11 provided inside the motor housing 6 near the second end 62. The first bearing 18 and the second bearing 11 support the shaft 8 so as to be rotatable about the central axis X.

[0023] The shaft 8 includes a first end 8b that protrudes in the axial direction D1 from a first end 61 of the motor housing 6, and a second end 8c that protrudes in the axial direction D1 from a second end 62 of the motor housing 6. An impeller 2 made of aluminum, for example, is attached to the first end 8b, which is the protruding portion of the shaft 8. More specifically, a through hole is formed in the impeller 2 along the central axis X, and the first end 8b of the shaft 8 is inserted into this through hole. For example, a male thread is formed on the circumferential surface of the first end 8b. A boss portion 2a that protrudes toward the rear surface is formed in the center of the base end side of the impeller 2.

[0024] The motor housing 6 includes a first cylindrical portion 6b extending from the distal opening of the insertion hole 6a toward the proximal end, a first annular step portion 6c tapering from the first cylindrical portion 6b, a second cylindrical portion 6d extending from the first step portion 6c toward the proximal end, a second annular step portion 6e tapering from the second cylindrical portion 6d, a third cylindrical portion 6f extending from the second step portion 6e toward the proximal end, a third annular step portion 6g expanding from the third cylindrical portion 6f, and a fourth cylindrical portion 6h extending from the third step portion 6g to the proximal opening of the insertion hole 6a. The diameter of the first cylindrical portion 6b is larger than the diameter of the second cylindrical portion 6d. The diameters of the second cylindrical portion 6d and the fourth cylindrical portion 6h are both larger than the diameter of the third cylindrical portion 6f. The third cylindrical portion 6f is, for example, the portion of the insertion hole 6a of the motor housing 6 that has the smallest diameter.

[0025] A rotor 8a is fixed to the center of the shaft 8 in the axial direction D1. The outer diameter of the rotor 8a is larger than the diameter of other parts of the shaft 8. The rotor 8a includes a magnetic field generating source such as a permanent magnet. The rotor 8a is housed in the motor housing 6. That is, both ends of the rotor 8a in the axial direction D1 are located between a first end 61 and a second end 62 of the motor housing 6.

[0026] A stator 4 is provided inside the motor housing 6. The stator 4 is housed in the third cylindrical portion 6f of the motor housing 6. More specifically, the stator 4 is inserted into a through hole H6 (fitting hole) that penetrates the third cylindrical portion 6f in the axial direction, and is fitted into the through hole H6. The stator 4 is spaced apart from each of the first end 61 and the second end 62 of the motor housing 6 in the axial direction D1. In other words, the length of the stator 4 in the axial direction D1 is shorter than the length between the first end 61 and the second end 62. The length of the stator 4 in the axial direction D1 is shorter than the length of the third cylindrical portion 6f, for example.

[0027] The stator 4 may include, for example, a conductor and a stator core, which is an iron core around which the conductor is wound. The stator 4 is disposed around the rotor 8a. The stator 4 faces the rotor 8a with a gap therebetween. Electricity can be passed through the stator 4 via wiring. When electricity is passed through the stator 4, a rotating magnetic field is generated between the stator 4 and the rotor 8a, causing the rotor 8a to rotate.

[0028] A plurality of grooves 9 are formed in the motor housing 6. When the extension direction of each groove 9 is broken down into an axial component D1 and a circumferential component D3 (see FIG. 2), the extension direction of each groove 9 includes at least the axial component D1. The groove 9 is formed, for example, in the third cylindrical portion 6f and is connected to the second step portion 6e and the third step portion 6g. The bottom surface 9a (see FIG. 3) of each groove 9 is spaced apart in the radial direction D2 from the stator 4 provided in the third cylindrical portion 6f. The radial direction D2 is perpendicular to the central axis X and orthogonal to the axial direction D1. The groove 9 forms a space extending in the axial direction D1 on the outer periphery of the stator 4. The groove 9 extends along the axial direction D1 throughout the area where the stator 4 is provided. In other words, the length of the groove 9 along the axial direction D1 is longer than the length of the stator 4 along the axial direction D1. A more specific configuration of the groove 9 will be described later.

[0029] A portion of the shaft 8 located distally of the rotor 8a is supported by the first bearing portion 18. A portion of the shaft 8 located proximally of the rotor 8a is supported by the second bearing portion 11. That is, the shaft 8 is rotatably supported by the first bearing portion 18 and the second bearing portion 11. The first bearing portion 18 includes a cylindrical support portion 18b that faces the shaft 8 and supports it, and a flange portion 18a that is provided at a proximal end of the support portion 18b in the axial direction D1 and protrudes outward in the radial direction D2. The second bearing portion 11 includes a cylindrical support portion 11b that faces the shaft 8 and supports it, and a flange portion 11a that is provided at a distal end of the support portion 11b in the axial direction D1 and protrudes outward in the radial direction D2.

[0030] Each of the first bearing portion 18 and the second bearing portion 11 is, for example, a gas bearing, and in this embodiment is a hydrodynamic air bearing. During operation of the fluid machine 1, the high-speed rotation of the shaft 8 forms an air layer between the shaft 8 and the support portions 18b, 11b. Therefore, the shaft 8 is supported in a floating state above the support portions 18b, 11b. Each of the first bearing portion 18 and the second bearing portion 11 may be, for example, a hydrostatic air bearing.

[0031] A first bearing plate 19 is fitted into the second cylindrical portion 6d of the motor housing 6. The first bearing plate 19 is an annular member that is fitted into the first end 61 of the motor housing 6 and holds the first bearing portion 18. A second bearing plate 12 is fitted into the fourth cylindrical portion 6h of the motor housing 6. The second bearing plate 12 is an annular member that is fitted into the second end 62 of the motor housing 6 and holds the second bearing portion 11.

[0032] An annular flow path forming plate 23 is fitted into the first cylindrical portion 6b of the motor housing 6. The flow path forming plate 23 is spaced apart from the first bearing plate 19 in the axial direction D1. The flow path forming plate 23 is also spaced apart from the first bearing portion 18 attached to the first bearing plate 19. In other words, a space 24 extending in the radial direction D2 is formed between the flow path forming plate 23 and the first bearing plate 19. An opening 20 in the first bearing plate 19 communicates between the insertion hole 6a of the motor housing 6 and the space 24.

[0033] An exhaust port 25 is formed in the flow path forming plate 23, and is provided on the first end 61 side of the motor housing 6. The exhaust port 25 communicates with the insertion hole 6a, the opening 20, and the space 24. The shaft 8 is inserted into the exhaust port 25. In this embodiment, the exhaust port 25 is smaller than the vent port 14. The size of the exhaust port 25 may be changed as appropriate.

[0034] The motor housing 6 is made up of the second bearing plate 12, first bearing plate 19, flow path forming plate 23, etc. The motor housing 6 is formed with an internal flow path 50 that connects the vent hole 14 and the exhaust port 25. The internal flow path 50 is formed in the gap between the inner wall surface of the motor housing 6 and the stator 4, shaft 8, second bearing plate 12, second bearing portion 11, first bearing plate 19, and first bearing portion 18.

[0035] 1 , the impeller 2 attached to the first end 8b of the shaft 8 is housed in an impeller housing 3. The impeller housing 3 includes an opening 30a serving as an intake port provided at the tip end side in the axial direction D1, an intake passage 30 extending from the opening 30a toward the base end side, a diffuser 29 communicating with the intake passage 30 and formed to surround the impeller 2, a scroll 31 provided on the outer periphery of the diffuser 29 and communicating with the diffuser 29, and an air outlet provided downstream of the scroll 31. The impeller housing 3 includes, for example, an impeller housing main body 26 and a disk-shaped closure plate 27 attached to the base end side of the impeller housing main body 26.

[0036] The above-described scroll 31 is formed in the impeller housing main body 26. The impeller housing main body 26 includes a circular opening 30a of the suction passage 30 formed on the tip side, and a circular opening 39 formed on the base end side, facing the opening 30a in the axial direction D1 and communicating with the suction passage 30.

[0037] The closure plate 27 is disposed on the rear side of the impeller 2 (i.e., the rotor 8a side). The closure plate 27 is fitted into an opening 39 on the base end side of the impeller housing main body 26, for example. The closure plate 27 and the impeller housing main body 26 are fixed to each other, for example, with bolts or the like. The closure plate 27 includes a first surface 27f provided on the impeller 2 side and a second surface 27g provided on the motor housing 6 side. The first surface 27f forms a diffuser 29 together with the impeller housing 3. An O-ring 28 is disposed on the outer periphery of the opening 39 of the impeller housing main body 26. The O-ring 28 is sandwiched between the impeller housing main body 26 and the closure plate 27, thereby sealing the flow path of the main flow 32.

[0038] The second surface 27g has a recessed surface 27a recessed toward the impeller 2. That is, the recessed surface 27a is disposed between the motor housing 6 and the impeller 2. In the axial direction D1, a first end 61 of the motor housing 6 is positioned closer to the impeller 2 than the second surface 27g of the closure plate 27. The first end 61 of the motor housing 6 fits into the recess formed by the recessed surface 27a. In other words, the recessed surface 27a receives the first end 61 of the motor housing 6. The recessed surface 27a faces the motor housing 6 on the side of the first end 61 in the axial direction D1.

[0039] The first end 61 of the motor housing 6 and the recessed surface 27a are spaced apart from each other along the axial direction D1. An exhaust flow path 33 that connects the exhaust port 25 to the outside air is formed between the first end 61 of the motor housing 6 and the recessed surface 27a.

[0040] A circular through-hole 27h penetrating in the axial direction D1 is formed in the center of the closure plate 27. A boss 2a provided on the back surface of the impeller 2 is inserted into this through-hole 27h. That is, the boss 2a penetrates the closure plate 27. The axial length of the boss 2a is, for example, the same as the axial length of the through-hole 27h of the closure plate 27. In this way, a part of the back surface of the impeller 2 is located on the motor housing 6 side of the recessed surface 27a.

[0041] The recessed surface 27a of the closure plate 27 includes multiple inclined portions. The recessed surface 27a includes, from the outer periphery, a first inclined portion 27b, a second inclined portion 27c, a third inclined portion 27d, and a fourth inclined portion 27e. Annular flat portions are formed between these inclined portions. The first inclined portion 27b and the second inclined portion 27c are located on the outer periphery side of the first cylindrical portion 6b of the motor housing 6. The first inclined portion 27b extends from the tip side (i.e., the impeller 2 side) of the first end 61 of the motor housing 6 to the base side (i.e., the stator 4 side) in the axial direction D1. The step of the fourth inclined portion 27e is smaller than the step of the first inclined portion 27b, the step of the second inclined portion 27c, and the step of the third inclined portion 27d.

[0042] The recessed surface 27a, which is made up of these inclined portions and flat portions, faces the flow path forming plate 23 provided at the first end 61 of the motor housing 6. An exhaust flow path 33 extending in the radial direction D2 is formed between the recessed surface 27a and the flow path forming plate 23. The exhaust flow path 33 communicates with the exhaust port 25 at its center and with the outside air at its outer peripheral end.

[0043] The closure plate 27 has screw seats that protrude toward the base end at a predetermined angular pitch. The closure plate 27 and the motor housing 6 are fastened together with bolts or the like via the screw seats. Alternatively, the flow path forming plate 23 is sandwiched between the screw seats and the motor housing 6, and the closure plate 27 and the motor housing 6 are fastened together with bolts or the like. The impeller housing 3 and the motor housing 6 are connected to each other with the closure plate 27 interposed therebetween. An exhaust flow path 33 is formed between the flow path forming plate 23 and the closure plate 27.

[0044] A tip-side medium diameter portion 8d is formed on the shaft 8 closer to the tip than the flow path forming plate 23. A cooling fan 34, made of, for example, aluminum, is inserted into the tip-side medium diameter portion 8d. The cooling fan 34 is disposed inside the exhaust flow path 33 so as to face the exhaust port 25. The cooling fan 34 includes a boss portion 35a into which the tip-side medium diameter portion 8d of the shaft 8 is inserted. An insertion hole 34a is formed in the boss portion 35a, and the tip-side medium diameter portion 8d is inserted into this insertion hole 34a. Meanwhile, the shaft 8 is formed with an annular stepped portion 8f, which is continuous with the tip-side medium diameter portion 8d and has a larger diameter than the tip-side medium diameter portion 8d. The stepped portion 8f is located between the motor housing 6 and the impeller 2 and faces the boss portion 2a of the impeller 2.

[0045] A tip small diameter portion 8e is formed on the tip side of the tip medium diameter portion 8d. The tip small diameter portion 8e corresponds to the first end portion 8b described above. The impeller 2 is fitted into the tip small diameter portion 8e. A fastening nut is threaded onto the tip side of the impeller 2. When the fastening nut is tightened, an axial force is generated, and the impeller 2 and the cooling fan 34 are attached to the shaft 8. In other words, a pressing force is generated from the fastening nut against the boss portion 2a of the impeller 2 and the cooling fan 34. In other words, the boss portion 35a of the cooling fan 34 and the impeller 2 are sandwiched between the step portion 8f of the shaft 8 and the fastening nut.

[0046] The impeller 2 presses the boss 35a of the cooling fan 34 with a boss 2a, which is part of the back surface. A gap is formed between the hub of the impeller 2 and the cooling fan 34, and the closure plate 27 described above is located in this gap. The boss 35a of the cooling fan 34 is located more inward than the flow path forming plate 23. The diameter of the cooling fan 34 is larger than the diameter of the exhaust port 25 of the flow path forming plate 23. In other words, the exhaust port 25 is located more inward than the outer ends of the blades 36 of the cooling fan 34.

[0047] Next, the configuration of the plurality of grooves 9 formed between the motor housing 6 and the stator 4 will be described in detail with reference to FIGS.

[0048] 2 shows a cross section of the fluid machine 1 taken along a plane perpendicular to the central axis X. As shown in FIG. 2, a plurality of grooves 9 are formed on the inner circumferential surface S6 of the motor housing 6. A portion of the inner circumferential surface S6 where the plurality of grooves 9 are not formed is in contact with the outer circumferential surface S4 of the stator 4. The motor housing 6 is fixed to the stator 4 by an interference fit such as shrink fitting, cold fitting, or press fitting. The motor housing 6 is made of, for example, aluminum. The stator 4 is made of, for example, iron. In this case, the thermal expansion coefficient of the motor housing 6 is greater than that of the stator 4.

[0049] Therefore, when the motor housing 6 and the stator 4 are fixed together by an interference fit such as shrink fitting or cold fitting, mutual stress occurs between the motor housing 6 and the stator 4 due to the difference in the thermal expansion coefficient between the motor housing 6 and the stator 4. Specifically, the motor housing 6 expands in the radial direction D2 (see FIG. 1 ), so a tensile stress F1 acts on the motor housing 6 in the circumferential direction D3. On the other hand, the stator 4 contracts in the radial direction D2, so a compressive stress F2 acts on the stator 4 in the circumferential direction D3.

[0050] The grooves 9 between the motor housing 6 and the stator 4 are aligned along the circumferential direction D3 on the inner circumferential surface S6. For example, the grooves 9 are aligned at equal intervals along the circumferential direction D3 at a predetermined angular pitch on the inner circumferential surface S6. In the example shown in FIG. 2 , six grooves 9 are formed at an angular pitch of 60°, for example. For example, each groove 9 extends linearly along the axial direction D1. Alternatively, each groove 9 may extend in a direction inclined with respect to the axial direction D1.

[0051] As shown in FIG. 3 , the groove 9 includes a bottom surface 9a recessed outward from the inner circumferential surface S6 in the radial direction D2, and a pair of side surfaces 9b and 9c connecting the bottom surface 9a and the inner circumferential surface S6. The bottom surface 9a faces the outer circumferential surface S4 of the stator 4 in the radial direction D2. A gap is formed between the bottom surface 9a and the outer circumferential surface S4. The side surfaces 9b and 9c are disposed on both sides of the bottom surface 9a in the circumferential direction D3 and face each other in the circumferential direction D3. The side surfaces 9b and 9c extend from the bottom surface 9a to the inner circumferential surface S6 so as to move away from each other as they move from the bottom surface 9a toward the inner circumferential surface S6. Therefore, the distance between the side surfaces 9b and 9c in the circumferential direction D3 increases as the groove approaches the inner circumferential surface S6 from the bottom surface 9a. In the cross section of FIG. 3, if a straight line connecting the center of the bottom surface 9a extending along the circumferential direction D3 and the central axis X is defined as a center line CL, the side surface 9b and the side surface 9c are formed, for example, to be symmetrical with respect to the center line CL.

[0052] In the cross section of Fig. 3, the groove 9 has a trapezoidal shape whose width in the circumferential direction D3 increases from the bottom surface 9a toward the inner circumferential surface S6. As shown in Fig. 3, if the connection point between the side surface 9b and the bottom surface 9a is defined as a start point P11, the connection point between the side surface 9b and the inner circumferential surface S6 is defined as an end point P12, the connection point between the side surface 9c and the bottom surface 9a is defined as a start point P21, and the connection point between the side surface 9c and the inner circumferential surface S6 is defined as an end point P22, the distance d1 in the circumferential direction D3 between the end point P12 of the side surface 9b and the end point P22 of the side surface 9c is greater than the distance d2 in the circumferential direction D3 between the start point P11 of the side surface 9b and the start point P21 of the side surface 9c. The distance d1 may be, for example, two or three times or more the distance d2.

[0053] 3 , when a radial line L11 (described later) is drawn from a start point P11 to the central axis X, the side surface 9b is inclined with respect to the radial line L11 so as to be positioned on the opposite side of the center line CL with respect to the radial line L11 as it moves from the start point P11 to an end point P12. Similarly, when a radial line L21 (described later) is drawn from the start point P21 to the central axis X, the side surface 9c is inclined with respect to the radial line L21 so as to be positioned on the opposite side of the center line CL with respect to the radial line L21 as it moves from the start point P21 to an end point P22. The phrase "the side surfaces 9b, 9c extend from the bottom surface 9a to the inner peripheral surface S6 so as to move away from each other as they move from the bottom surface 9a to the inner peripheral surface S6" means that the side surfaces 9b, 9c are inclined with respect to the radial lines L11, L21 so as to be positioned on the opposite side of the center line CL with respect to the radial lines L11, L21 as they move from the bottom surface 9a to the inner peripheral surface S6. Therefore, "the side surfaces 9b, 9c extend from the bottom surface 9a to the inner surface S6 so as to move away from each other as they move from the bottom surface 9a to the inner surface S6" does not include the side surfaces 9b, 9c being inclined so as to be positioned closer to the center line CL with respect to the radial lines L11, L21 as they move from the bottom surface 9a to the inner surface S6, nor does it include the side surfaces 9b, 9c extending along the radial lines L11, L21, respectively.

[0054] The internal region of the groove 9, surrounded by the bottom surface 9a, the side surfaces 9b, 9c, and the inner circumferential surface S6, constitutes a refrigerant flow path F through which cooling air 38 (cooling medium) passes. As shown in FIG. 1 , the refrigerant flow path F is connected to the inner-housing flow path 50. Therefore, when the cooling air 38 flows through the inner-housing flow path 50, the cooling air 38 also flows through the refrigerant flow path F of the groove 9. At this time, the cooling air 38 cools the stator 4 by directly removing heat from the stator 4. The larger the cross-sectional area of ​​the refrigerant flow path F, the more efficiently the cooling air 38 cools the stator 4. On the other hand, the larger the cross-sectional area of ​​the refrigerant flow path F, the smaller the contact area between the inner circumferential surface S6 of the motor housing 6 and the outer circumferential surface S4 of the stator 4, which reduces the resistance to stress acting on these surfaces (i.e., the inner circumferential surface S6 and the outer circumferential surface S4). Therefore, the flow path cross-sectional area of ​​the refrigerant flow path F is determined by adjusting the depth of the groove 9 and the contact area between the motor housing 6 and the stator 4, taking into account the balance between the cooling efficiency of the stator 4 and the strength of the motor housing 6.

[0055] The configuration of the side surfaces 9b and 9c of the groove 9 will be described in more detail with reference to FIG. 4. As described above, the side surfaces 9b and 9c are symmetrical with respect to the center line CL and therefore have corresponding shapes. Therefore, the configuration of the side surface 9b will be described in detail below as a representative of the side surfaces 9b and 9c.

[0056] In the cross section of FIG. 4 , the side surface 9b is represented as a linear portion L9 including at least one straight line or curve connecting a starting point P11 connected to the bottom surface 9a and an ending point P12 connected to the inner circumferential surface S6. In this embodiment, the linear portion L9 as the side surface 9b is represented by only one straight line connecting the starting point P11 and the ending point P12. As shown in FIG. 4 , when a tangent T9, which is a tangent line T9 with an arbitrary point on the linear portion L9 as a contact point P9, is decomposed into a radial component T91 extending from the contact point P9 in the radial direction D2 and a circumferential component T92 extending from the contact point P9 in the circumferential direction D3, the tangent T9 of each contact point P9 from the starting point P11 to the ending point P12 includes at least the circumferential component T92 of the circumferential component T92 and the radial component T91. In the example shown in FIG. 4 , the length of the circumferential component T92 of the tangent T9 is longer than the radial component T91 of the tangent T9. For example, the length of the circumferential component T92 of the tangent T9 may be two or more times or three or more times the length of the radial component T91 of the tangent T9.

[0057] The fact that the tangent line T9 of each tangent point P9 of the linear portion L9 includes at least a circumferential component T92 means that the linear portion L9 does not include a straight line or a curve extending only in the radial direction D2 from each tangent point P9. When the linear portion L9 is composed of only one straight line, as in the present embodiment, the linear portion L9 extends from the starting point P11 to the ending point P12 in a direction inclined at least with respect to the radial direction D2. More specifically, if the radial line L11 is a straight line that passes through the starting point P11 and extends along the radial direction D2, and the circumferential line L12 is a straight line that passes through the starting point P11 and extends along the circumferential direction D3, the linear portion L9 extends from the starting point P11 in a direction inclined with respect to both the radial line L11 and the circumferential line L12.

[0058] In this embodiment, the linear portion L9 extends from the starting point P11 in a direction inclined closer to the circumferential line L12 than the radial line L11. That is, the angle θ1 of the linear portion L9 with respect to the circumferential line L12 is smaller than the angle θ2 of the linear portion L9 with respect to the radial line L11. The fact that the length of the circumferential component T92 of the tangent line T9 is longer than the radial component T91 of the tangent line T9 means that the linear portion L9 extends in a direction inclined closer to the circumferential line L12 than the radial line L11. As described above, the side surface 9c has a symmetrical shape to the side surface 9b. Therefore, the side surface 9c extends from the starting point P21 in a direction inclined closer to the circumferential line L22 than the radial line L21, corresponding to the side surface 9b (see FIG. 3).

[0059] Considering the case where the linear portion L9 has a complex configuration including multiple straight lines or curves, the relationship between the start point P11 and the end point P12 can be explained as follows. When an imaginary line connecting the start point P11 and the end point P12 is drawn, the imaginary line is decomposed into a radial component T93 extending from the start point P11 in the radial direction D2 and a circumferential component T94 extending from the start point P11 in the circumferential direction D3. However, in FIG. 4 , the imaginary line connecting the start point P11 and the end point P12 can be considered as the linear portion L9. In this case, the length of the circumferential component T94 is longer than the length of the radial component T93. This makes it easier to configure the linear portion L9 connecting the start point P11 and the end point P12 to extend in a direction inclined closer to the circumferential line L12 than the radial line L11. The same relationship as the relationship between the start point P11 and the end point P12 also applies to the relationship between the start point P21 and the end point P22.

[0060] The configuration of the side surfaces 9b and 9c of the groove 9 can also be explained from another perspective as follows.

[0061] In the cross section of Figure 3, the bottom surface 9a, side surface 9b, side surface 9c, and outer peripheral surface S4 can be seen as multiple boundary lines forming the groove 9. The outer peripheral surface S4 (first boundary line) is represented as a curve connecting the contact portion P1 (first contact portion) and the contact portion P2 (second contact portion). The contact portions P1 and P2 are contact portions of the outer peripheral surface S4 with the inner peripheral surface S6, and are portions located on both sides of the groove 9 in the circumferential direction D3. The side surface 9b (second boundary line) is represented as a straight line extending from the contact portion P1 to one side of the circumferential direction D3 as it moves outward in the radial direction D2. The side surface 9c (third boundary line) is represented as a straight line extending from the contact portion P2 to the other side of the circumferential direction D3 as it moves outward in the radial direction D2.

[0062] In this case, if the radius of curvature of side surface 9b is represented by r, the position of side surface 9b is represented by angle θ, and the average slope is represented by (dr / rdθ), the average slope of side surface 9b is less than 1. If side surface 9b includes a circular chamfered portion at the connection portion with bottom surface 9a, the average slope of the chamfered portion corresponds to 1. The average radius of curvature of side surface 9b is greater than the difference between the average inner and outer diameters of side surface 9b. If the same is true for side surface 9c, the average slope of side surface 9c is less than 1. The average radius of curvature of side surface 9c is greater than the difference between the average inner and outer diameters of side surface 9c. This means that side surface 9b and side surface 9c are connected by a line with a gentler slope than a simple circle.

[0063] Next, the operation of the fluid machine 1 will be described. The fluid machine 1 can be used, for example, for blowing or suctioning air. When the fluid machine 1 is used for blowing air, an object to be blown is provided beyond (i.e., downstream side of) the outlet of the main flow 32. When the fluid machine 1 is used for suction, an object to be suctioned is provided before (i.e., upstream side of) the suction port (opening 30a) of the main flow 32.

[0064] When power is supplied to the stator 4, a rotating magnetic field is generated between the stator 4 and the rotor 8a of the shaft 8, causing the shaft 8 to rotate. The rotation of the shaft 8 causes the impeller 2 to rotate, and the rotation of the impeller 2 causes a main flow 32 to be drawn into the impeller housing 3. When the fluid machine 1 is used for suction, air is drawn from a predetermined object to be suctioned. When the fluid machine 1 is used for blowing air, the main flow 32 drawn into the impeller housing 3 passes through the diffuser 29 and the scroll 31 and is blown to the predetermined object to be blown.

[0065] During operation of the fluid machine 1, the cooling fan 34 rotates together with the impeller 2. As the cooling fan 34 rotates, the inside of the motor housing 6 is sucked through the exhaust port 25. Because the inside of the motor housing 6 becomes negative pressure, outside air is sucked into the inside of the motor housing 6 through the vent 14 as cooling air 38.

[0066] The cooling air 38 drawn in through the vent 14 flows through an internal housing flow path 50 formed in the motor housing 6 and between the stator 4 and the rotor 8a. When the cooling air 38 flows through the internal housing flow path 50, the cooling air 38 can also flow through grooves 9 formed in the inner circumferential surface S6 of the motor housing 6.

[0067] The cooling air 38 that has circulated inside the motor housing 6 passes through the opening 20 and reaches the space 24. The cooling air 38 that has reached the space 24 is deflected toward the center by the flow path forming plate 23. The cooling air 38 that has been deflected toward the center is exhausted to the outside of the motor housing 6 through the exhaust port 25.

[0068] The cooling air 38 exhausted from the exhaust port 25 and sucked into the cooling fan 34 is exhausted outward in the radial direction D2, flows through the exhaust flow path 33, and is guided by the recessed surface 27a including multiple inclined portions and exhausted to the outside of the fluid machine 1.

[0069] During operation of the fluid machine 1, heat sources such as the stator 4 generate heat. The stator 4, which is a heat source, is cooled by the cooling air 38 circulating inside the motor housing 6. The stator 4 is further cooled by the heat dissipation fins 7, which exchange heat with the outside air. The stator 4 is further cooled directly by the cooling air 38 flowing through the grooves 9. Examples of heat sources other than the stator 4 include the rotor 8a including a permanent magnet, the first bearing portion 18, the second bearing portion 11, and an air gap. The air gap is an air flow that can occur between the rotor 8a and the stator 4 in the rotational direction of the rotor 8a. The air gap causes windage loss. In this embodiment, all of the above heat sources are cooled directly or indirectly.

[0070] The effects of the fluid machine 1 of the present embodiment described above will be described together with the problems of the comparative example.

[0071] FIG. 7 shows a fluid machine 100 according to a comparative example. The fluid machine 100 differs from the fluid machine 1 according to the present embodiment in the shape of the groove 109 between the motor housing 106 and the stator 104. In the fluid machine 100, the cross-sectional shape of the groove 109 formed in the motor housing 106 is rectangular. When the motor housing 106 and the stator 104 are fixed to each other by an interference fit, a tensile stress F1 acts on the motor housing 106 in the circumferential direction D3, and a compressive stress F2 acts on the stator 104 in the circumferential direction D3. When the motor housing 106 has the groove 109 formed therein, as in the fluid machine 100, the tensile stress F1 acting on the motor housing 106 tends to concentrate in the vicinity of the groove 109. This is because the tensile stress F1 tends to concentrate in portions of the motor housing 106 where the cross-sectional area changes abruptly at each position when the motor housing 106 is cut along a plane perpendicular to the circumferential direction D3 at each position along the circumferential direction D3.

[0072] The change in the cross-sectional area of ​​the motor housing 106 at each position along the circumferential direction D3 can be represented as the change in the length of the arrow A106 at each position along the circumferential direction D3 in the cross section of Figure 8(a). The change in the length of the arrow A106 at each position along the circumferential direction D3 can also be said to indicate the thickness of the motor housing 106 at each position along the radial direction D2. When a rectangular groove 109 is formed in the motor housing 106, as in the fluid machine 100, the side surface 109b of the groove 109 is formed perpendicular to the bottom surface 109a of the groove 109 and extends linearly only along the radial direction D2 perpendicular to the circumferential direction D3.

[0073] In the cross section of Figure 8(a), when the side surface 109b extending linearly only along the radial direction D2 is present, the side surface 109b creates a portion where the length of the arrow A106 changes abruptly. In other words, the side surface 109b creates a portion where the change in the cross-sectional area of ​​the motor housing 106 at each position along the circumferential direction D3 changes abruptly. In this case, a large stress concentration occurs in the peripheral portion of the groove 109, such as the corner P109 between the side surface 109b and the bottom surface 109a. In order to withstand this stress concentration in the peripheral portion of the groove 109, it is conceivable to increase the thickness of the motor housing 106, as shown in Figure 8(a).

[0074] However, increasing the thickness of the motor housing 106 in this manner increases the size and weight of the fluid machine 100. In particular, in a low-temperature environment such as −30°C, the interference of the interference fit tends to increase due to the difference in thermal expansion coefficients between the motor housing 106 and the stator 104. Alternatively, it is possible to increase the interference to transmit greater torque. As the interference increases, the tensile stress F1 acting on the motor housing 106 increases, and the stress concentration around the groove 109 also increases. If the thickness of the motor housing 106 were to be further increased to withstand such stress concentration, the weight of the fluid machine 100 would further increase. Therefore, it is difficult to reduce the weight of the fluid machine 100.

[0075] Figure 8(b) shows a case where a corner P109 of the groove 109 in Figure 8(a) has been subjected to R (rounding) processing. That is, in the fluid machine 200 in Figure 8(b), an R-chamfered portion P209 is formed in the groove 209 of the motor housing 206. As a method for alleviating stress concentration, it is considered to perform rounding processing on the corners of the groove 209 in this manner. In the cross section of Figure 8(b), the R-chamfered portion P209 is represented as a curve that curves between a side surface 209b and a bottom surface 209a of the groove 209 and extends to connect the side surface 209b and the bottom surface 209a.

[0076] The fluid machine 200 of Figure 8(b) can reduce stress concentration in the peripheral portion of the groove 209 compared to the fluid machine 100 of Figure 8(a). However, the fluid machine 200 still has a side surface 209b extending only in the radial direction D2, and the side surface 209b creates a portion where the length of the arrow A206 changes abruptly. In other words, the side surface 209b creates a portion where the cross-sectional area of ​​the motor housing 206 changes abruptly at each position along the circumferential direction D3. Therefore, it is difficult to suppress stress concentration in the peripheral portion of the groove 209 in the fluid machine 200 as well.

[0077] In contrast, in the fluid machine 1 according to this embodiment, as described above, the linear portion L9, represented as the side surface 9b of the groove 9, does not include a portion extending only in the radial direction D2. Therefore, when the motor housing 6 is cut along a plane perpendicular to the circumferential direction D3 at each position along the circumferential direction D3, abrupt changes in the cross-sectional area of ​​the motor housing 6 can be suppressed. In other words, the cross-sectional area of ​​the peripheral portion of the groove 9 can be gradually changed. As shown in FIG. 5 , the length of the arrow A6 at each position along the circumferential direction D3 at the peripheral portion of the groove 9 changes gradually, rather than abruptly. Therefore, in the fluid machine 1, it is possible to suppress the occurrence of large stress concentrations in the peripheral portion of the groove 9. As a result, the motor housing 6 does not need to be excessively thick to withstand stress concentrations in the peripheral portion of the groove 9. This prevents the fluid machine 1 from becoming too large and thus reduces its weight. As a result, a lightweight fluid machine 1 with a motor housing 6 as thin as possible can be used even in low-temperature environments, such as -30°C. Furthermore, by using such a fluid machine 1, it is possible to realize large torque transmission.

[0078] In this embodiment, a groove 9 is formed in the inner circumferential surface S6 of the motor housing 6. When the motor housing 6 and the stator 4 are fixed to each other by an interference fit, the tensile stress F1 acting on the motor housing 6 is particularly likely to be large. Therefore, when the groove 9 is formed in the inner circumferential surface S6 of the motor housing 6, stress is likely to concentrate in the area surrounding the groove 9. In contrast, according to the configuration of this embodiment, as described above, it is possible to effectively prevent large stress concentrations in the area surrounding the groove 9, thereby effectively achieving the above-mentioned effects.

[0079] The thermal expansion coefficient of the motor housing 6 may be greater than that of the stator 4. In this case, when the motor housing 6 and the stator 4 are fixed together by an interference fit such as shrink fitting or cold fitting, a large tensile stress F1 is likely to act on the motor housing 6 due to the difference between the thermal expansion coefficients of the motor housing 6 and the stator 4, and stress is likely to concentrate in the peripheral areas of the grooves 9 formed in the inner circumferential surface S6 of the motor housing 6. In contrast, with the above-described configuration, as described above, it is possible to effectively prevent large stress concentrations in the peripheral areas of the grooves 9, thereby effectively achieving the above-described effects.

[0080] In this embodiment, in the cross section of the groove 9, the distance d1 between the end point P12 of the side surface 9b and the end point P22 of the side surface 9c along the circumferential direction D3 is greater than the distance d2 between the start point P11 of the side surface 9b and the start point P21 of the side surface 9c along the circumferential direction D3. The outer peripheral surface S4 of the stator 4 is exposed between the end point P12 of the side surface 9b and the end point P22 of the side surface 9c, and the cooling air 38 passing through the groove 9 contacts the outer peripheral surface S4 of the stator 4. Therefore, by increasing the distance d1 between the end point P12 of the side surface 9b and the end point P22 of the side surface 9c as in the above configuration, the contact area of ​​the outer peripheral surface S4 of the stator 4 with the cooling air 38, i.e., the heat transfer area, can be increased. This increases the cooling efficiency of the stator 4 by the cooling air 38.

[0081] In this embodiment, the linear portions L9 represented as the side surfaces 9b in the cross section of the groove 9 extend linearly along a direction including a circumferential component T92. In this case, it is easier to form the side surfaces 9b of the groove 9 than when the linear portions L9 are formed only by complex curves.

[0082] In this embodiment, the length of the circumferential component T92 of the tangent T9 of each tangent point P9 from the start point P11 to the end point P12 is longer than the length of the radial component T91 of the tangent T9. In this case, in the cross section of the groove 9, the linear portion L9 serving as the side surface 9b extends in the circumferential direction D3 rather than the radial direction D2, so that the change in the peripheral portion of the groove 9 at each position along the circumferential direction D3 can be made more gradual. This makes it possible to more effectively suppress the occurrence of large stress concentrations in the peripheral portion of the groove 9.

[0083] In this embodiment, the side surfaces 9b and 9c of the groove 9 are formed to be symmetrical with respect to the center line CL. In this case, stress in the peripheral portion of the groove 9 can be evenly dispersed, and therefore, large stress concentrations in the peripheral portion of the groove 9 can be more effectively suppressed.

[0084] The present disclosure can be implemented in various forms, including the above-described embodiment, with various modifications and improvements made based on the knowledge of those skilled in the art. Furthermore, it is also possible to configure modified versions of the embodiment by utilizing the technical matters described in the above-described embodiment.

[0085] Fig. 6(a) shows an enlarged cross section of a peripheral portion of a groove 9A formed in a motor housing 6A of a fluid machine 1A according to Modification 1. In the cross section of Fig. 6(a), a linear portion L9A represented as a side surface 9d of the groove 9A includes only a straight line L91 extending in a direction inclined with respect to both the radial line L11 and the circumferential line L12, a first curved line L92 connecting a starting point P11 and the straight line L91, and a second curved line L93 connecting the straight line L91 and an end point P12. Fig. 6(a) also shows a first connection point P10 where the first curved line L92 and the straight line L91 are connected, and a second connection point P20 where the straight line L91 and the second curved line L93 are connected.

[0086] The first curved line L92 extends in an arc shape from the starting point P11 to the first connection point P10, curving toward the outer peripheral surface S4 of the stator 4. The second curved line L93 extends in an arc shape from the second connection point P20 to the end point P12, curving toward the opposite side from the outer peripheral surface S4. A tangent T9A to each contact point P9A of the linear portion L9A includes at least the circumferential component T92A of the radial component T91A and the circumferential component T92A. Therefore, the linear portion L9A does not include a portion extending only in the radial direction D2 from each contact point P9A.

[0087] FIG. 6B shows an enlarged cross section of a groove 9B formed in a motor housing 6B of a fluid machine 1B according to Modification 2. In the cross section of FIG. 6B, a linear portion L9B, shown as a side surface 9e of the groove 9B, includes only a first curve L94 and a second curve L95. Therefore, the linear portion L9B does not include any straight lines. FIG. 6B also shows a connection point P30 where the first curve L94 and the second curve L95 are connected. The first curve L94 extends in an arc shape from the starting point P11 to the connection point P30, curving toward the outer peripheral surface S4 of the stator 4. The second curve L95 extends in an arc shape from the connection point P30 to the end point P12, curving toward the opposite side of the outer peripheral surface S4. A tangent T9B to each tangent point P9B of the linear portion L9B includes at least a circumferential component T92B of a radial component T91B and a circumferential component T92B. Therefore, the linear portion L9B does not include a portion that extends only in the radial direction D2 from each contact point P9B.

[0088] 6A and 6B, similarly to the above-described embodiment, abrupt changes in the cross-sectional area of ​​the motor housings 6A, 6B can be suppressed, thereby suppressing stress concentration in the peripheral portions of the grooves 9A, 9B. As a result, it is not necessary to make the motor housings 6A, 6B excessively thick in order to withstand stress concentration in the peripheral portions of the grooves 9A, 9B, and therefore it is possible to suppress an increase in the size of the fluid machines 1A, 1B and thereby achieve a reduction in the weight of the fluid machines 1A, 1B.

[0089] In the above-described embodiment, the groove 9 through which the cooling air 38 passes is formed on the inner circumferential surface S6 of the motor housing 6. However, the groove 9 may be formed on the outer circumferential surface S4 of the stator 4. In this case, the pair of side surfaces 9b, 9c of the groove 9 may be inclined so as to move away from each other in the circumferential direction D3 as they approach the outer circumferential surface S4 from the bottom surface 9a. In the above-described embodiment, the cooling air 38 is exemplified as the cooling medium. However, the cooling medium may be something other than the cooling air 38. The cooling medium may be, for example, a liquid such as cooling water. In the above-described embodiment, the cooling fan 34 attached to the shaft 8 is exemplified. However, as long as the external cooling medium passes through the groove 9, the cooling fan 34 does not necessarily have to be provided. In the above-described embodiment, the fluid machine of the present disclosure is a centrifugal blower. However, the fluid machine of the present disclosure may be a centrifugal compressor or an axial-flow type blower or compressor.

[0090] <Additional Notes> The present disclosure provides a housing comprising: [1] a stator having a central axis; and a housing including an inner peripheral surface in contact with an outer peripheral surface of the stator, wherein a groove is formed in one of the outer peripheral surface and the inner peripheral surface, the groove extending in a direction including an axial component of the central axis and through which a cooling medium capable of cooling the stator passes, the groove including: a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis; and a pair of side surfaces disposed at positions facing each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to become more separated from each other in the circumferential direction as they approach the peripheral surface, in a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a start point connected to the bottom surface and an end point connected to the peripheral surface, "A fluid machine in which, when a tangent having a contact point at any point on the linear portion is decomposed into a circumferential component extending from the contact point in the circumferential direction and a radial component extending from the contact point in the radial direction, the tangent to each of the contact points from the start point to the end point includes at least the circumferential component of the circumferential component and the radial component."

[0091] The present disclosure is [2] "A fluid machine according to the above [1], wherein the circumferential surface is the inner circumferential surface of the housing."

[0092] The present disclosure is [3] "A fluid machine according to the above [2], wherein the thermal expansion coefficient of the housing is greater than the thermal expansion coefficient of the stator."

[0093] The present disclosure is [4] "A fluid machine as described in [2] or [3] above, wherein, in the cross section of the groove, the distance between the end points of the pair of side surfaces along the circumferential direction is greater than the distance between the start points of the pair of side surfaces along the circumferential direction."

[0094] The present disclosure is [5] "A fluid machine described in any one of [1] to [4] above, wherein in the cross section of the groove, the linear portion represented as the side surface includes a straight line extending linearly along a direction including the circumferential component."

[0095] The present disclosure is [6] "A fluid machine described in any of [1] to [5] above, wherein the length of the circumferential component of the tangent of each of the contact points from the starting point to the end point is longer than the length of the radial component of the tangent."

[0096] The present disclosure is [7] "A fluid machine described in any one of [1] to [6] above, wherein, in the cross section of the groove, when a straight line connecting the center between the starting points of the pair of side surfaces along the circumferential direction and the central axis is taken as a center line, the pair of side surfaces are formed so as to be symmetrical with respect to the center line."

[0097] The present disclosure is [8] "a housing comprising: a stator having a central axis; and an inner peripheral surface in contact with an outer peripheral surface of the stator; wherein a groove extending in a direction including an axial component of the central axis and through which a cooling medium capable of cooling the stator passes is formed on one of the outer peripheral surface and the inner peripheral surface; the groove including: a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis; and a pair of side surfaces disposed at positions facing each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to move away from each other in the circumferential direction as they approach the peripheral surface; and in a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a start point connected to the bottom surface and an end point connected to the peripheral surface, 2. The fluid machine according to claim 1, wherein when an imaginary straight line connecting the start point and the end point is decomposed into a circumferential component extending from the start point in the circumferential direction and a radial component extending from the start point in the radial direction, the length of the circumferential component of the imaginary straight line is longer than the length of the radial component of the imaginary straight line.

[0098] DESCRIPTION OF SYMBOLS 1, 1A, 1B Fluid machine 4 Stator 6, 6A, 6B Motor housing (housing) 8 Shaft 8a Rotor 9, 9A, 9B Groove 9a Bottom surface 9b, 9d, 9e Side surface (second boundary line) 9c Side surface (third boundary line) 10 Motor 38 Cooling air (cooling medium) CL Center line D1 Axial direction D2 Radial direction D3 Circumferential direction d1, d2 Distance F Coolant flow path L9, L9A, L9B Linear portion L91 Straight line P1 Contact portion (first contact portion) P2 Contact portion (second contact portion) P9, P9A, P9B Contact point P11, P21 Starting point P12, P22 Ending point S4 Outer circumferential surface (first boundary line) S6 Inner circumferential surface T9, T9A, T9B Tangent line T91, T91A, T91B Radial component T92, T92A, T92B Circumferential component T93 Radial component T94 Circumferential component

Claims

1. A housing comprising: a stator having a central axis; and an inner peripheral surface in contact with an outer peripheral surface of the stator, wherein a groove is formed on one of the outer peripheral surface and the inner peripheral surface, the groove extending in a direction including an axial component of the central axis and through which a cooling medium capable of cooling the stator passes, the groove comprising: a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis; and a pair of side surfaces disposed at positions facing each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to move away from each other in the circumferential direction as they approach the peripheral surface, wherein in a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a start point connected to the bottom surface and an end point connected to the peripheral surface, A fluid machine, wherein when a tangent having a contact point at any point on the linear portion is decomposed into a circumferential component extending from the contact point in the circumferential direction and a radial component extending from the contact point in the radial direction, the tangent to each of the contact points from the start point to the end point includes at least the circumferential component of the circumferential component and the radial component.

2. The fluid machinery according to claim 1, wherein the peripheral surface is the inner peripheral surface of the housing.

3. The fluid machine according to claim 2, wherein the thermal expansion coefficient of the housing is greater than the thermal expansion coefficient of the stator.

4. A fluid machine as described in claim 2, wherein, in the cross section of the groove, the distance between the end points of the pair of side surfaces along the circumferential direction is greater than the distance between the starting points of the pair of side surfaces along the circumferential direction.

5. A fluid machinery according to any one of claims 1 to 4, wherein in the cross section of the groove, the linear portion represented as the side surface includes a straight line extending linearly along a direction including the circumferential component.

6. A fluid machine according to any one of claims 1 to 4, wherein the length of the circumferential component of the tangent of each of the contact points from the starting point to the end point is longer than the length of the radial component of the tangent.

7. A fluid machinery described in any one of claims 1 to 4, wherein, in the cross section of the groove, when a straight line connecting the center between the starting points of the pair of side surfaces along the circumferential direction and the central axis is taken as a center line, the pair of side surfaces are formed so as to be symmetrical with respect to the center line.

8. A housing comprising: a stator having a central axis; and an inner peripheral surface in contact with an outer peripheral surface of the stator, wherein a groove is formed on one of the outer peripheral surface and the inner peripheral surface, the groove extending in a direction including an axial component of the central axis and through which a cooling medium capable of cooling the stator passes, the groove comprising: a bottom surface recessed from the peripheral surface in a radial direction perpendicular to the central axis; and a pair of side surfaces disposed at positions facing each other along a circumferential direction centered on the central axis and extending from the bottom surface to the peripheral surface so as to move away from each other in the circumferential direction as they approach the peripheral surface, wherein in a cross section of the groove perpendicular to the central axis, each of the pair of side surfaces is represented as a linear portion including at least one straight line or curve connecting a starting point connected to the bottom surface and an end point connected to the peripheral surface, 2. The fluid machine of claim 1, wherein when a virtual straight line connecting the starting point and the end point is decomposed into a circumferential component extending in the circumferential direction from the starting point and a radial component extending in the radial direction from the starting point, the length of the circumferential component of the virtual straight line is longer than the length of the radial component of the virtual straight line.

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