Rotary electrical machine

Abstract

Provided is a rotary electrical machine which can enhance cooling performance and thus can be operated for a long time. An electrical motor 2 is provided with a stator, a flywheel 10, and a fan 18. The flywheel 10 is provided with: a bottom wall 12; a circumferential wall 13 extending from the circumferential edge of the bottom wall 12 along a first rotation axis A1; and protrusions 85, 86, 87 arranged in flywheel ventilation ports 16. The fan 18 is provided on the outer surface of the bottom wall 12. The fan 18 has a plurality of fan blades 20 arranged side by side in the circumferential direction. The protrusions 85, 86, 87 are arranged at the ends of the fan blades 20 on the bottom wall 12 side.

Description

rotating electrical machines

[0001] The present invention relates to a rotating electric machine.

[0002] In recent years, for example, motorcycles and the like have been developed that are powered by rotating electric machines (electric motors) instead of internal combustion engines such as internal combustion engines. This type of rotating electric machine includes a stator wound with an excitation coil and a rotor rotatable relative to the stator. The rotor includes a flywheel (rotor yoke) formed in a cylindrical shape with a bottom so as to cover the stator from the outside, and a shaft that supports the flywheel.

[0003] A magnet is provided on the inner peripheral surface of the flywheel. The shaft is connected to, for example, a rear wheel via a transmission mechanism that transmits power. This type of rotating electric machine is also provided with a cover that covers the flywheel from the outside to protect the rotating electric machine. With this configuration, the rotating electric machine generates a magnetic field by supplying power to the excitation coil, causing the rotor to rotate. The rotation of the rotor is transmitted to, for example, the rear wheel via the transmission mechanism, causing the motorcycle or the like to move.

[0004] Japanese Patent Application Laid-Open No. 2022-75885

[0005] However, if the flywheel is covered as in the above-mentioned conventional technology, the exciting coil may generate heat under high load, which may cause the inside of the rotating electrical machine to become too hot. In such a case, there is a problem that it becomes difficult to operate the rotating electrical machine for a long time.

[0006] Therefore, the present invention provides a rotating electrical machine that can be operated for a long period of time by improving the cooling performance.

[0007] In order to solve the above problems, in a first aspect of the present invention, a rotating electric machine includes a stator around which an excitation coil is wound and which generates a magnetic field, a flywheel rotatably mounted relative to the stator, and a fan mounted on the flywheel and rotating integrally with the flywheel, the flywheel being arranged to face the stator in the direction of the rotation axis of the flywheel and including a flywheel bottom wall having an opening, a flywheel peripheral wall extending from the periphery of the flywheel bottom wall along the rotation axis, radially facing the outer peripheral surface of the stator and having a magnet mounted thereon, and a protrusion disposed within the opening, the fan being mounted on the outer surface of the flywheel bottom wall opposite the stator, and the fan having a plurality of fan blades arranged circumferentially, the protrusion being disposed at the end of the fan blade on the flywheel bottom wall side.

[0008] This configuration allows the cooling air generated by the fan rotating integrally with the flywheel to pass efficiently through the openings formed in the flywheel. It also increases the flow rate of the cooling air passing through the openings. This improves the cooling performance of the rotating electric machine, enabling it to operate for extended periods of time.

[0009] In a second aspect of the present invention, in the rotating electric machine of the first aspect, the convex portion may be formed to protrude from the fan blade.

[0010] This configuration makes it easier to manufacture the flywheel because no protrusions are formed on the flywheel. The protrusions and the fan blades are smoothly connected, allowing cooling air to flow smoothly from the protrusions to the fan blades.

[0011] In a third aspect of the present invention, in the rotating electric machine of the first or second aspect, the protrusion may protrude from an inner surface of the flywheel bottom wall on the stator side.

[0012] This configuration allows the cooling air to pass through the openings more efficiently, and also ensures that the flow speed of the cooling air passing through the openings is increased.

[0013] In a fourth aspect of the present invention, in a rotating electric machine according to any one of the first to third aspects, the opening may be formed in an arc shape that is long in the circumferential direction, and each of the convex portions of the plurality of fan blades may be inserted into one of the openings.

[0014] This configuration allows the cooling air to pass through the openings more efficiently, and also ensures that the flow speed of the cooling air passing through the openings is increased.

[0015] In a fifth aspect of the present invention, in the rotating electric machine of the fourth aspect, the plurality of protrusions inserted into one opening may be arranged so as to divide the opening evenly in the circumferential direction.

[0016] This configuration allows the cooling air to pass through the entire opening evenly, which allows the cooling air to pass through the opening more efficiently.

[0017] In a sixth aspect of the present invention, in a rotating electric machine according to any one of the first to fifth aspects, the fan has a boss portion having a cylindrical portion arranged on the rotation axis of the bottom wall of the flywheel, the plurality of fan blades protrude radially outward from the outer peripheral surface of the cylindrical portion, and the inclination angle θ of each fan blade with respect to the rotation axis may satisfy the relationship 25°≦θ≦45°.

[0018] This configuration prevents the opening from being blocked by the fan blades, allowing the fan to efficiently generate cooling air. Furthermore, the cooling air drawn in from inside the flywheel through the opening can be discharged outside the flywheel in a diagonal radial direction relative to the rotation axis. Therefore, even if a cover is provided to cover the outside of the flywheel, the cooling air can be prevented from being blown forcefully against the cover. As a result, the cooling air can pass smoothly through the opening.

[0019] According to a seventh aspect of the present invention, in the rotating electric machine of the sixth aspect, the protrusion may extend along the rotation axis.

[0020] This configuration prevents the flow of cooling air passing through the opening from being obstructed by the protrusions, allowing the cooling air to pass through the opening more efficiently and reliably increasing the flow speed of the cooling air passing through the opening.

[0021] In an eighth aspect of the present invention, in a rotating electric machine according to any one of the first to seventh aspects, the opening is formed in an arc shape that is long in the circumferential direction, and of the two circumferential ends of the opening, the rear side in the direction of rotation of the flywheel may be formed flat along the radial direction.

[0022] This configuration can prevent positive pressure from being generated behind the opening in the direction of flywheel rotation, allowing the cooling air to pass through the opening more efficiently and reliably increasing the flow rate of the cooling air passing through the opening.

[0023] In a ninth aspect of the present invention, in a rotating electric machine of any one of the first to eighth aspects, a cover is provided that covers the flywheel from the outside, and the cover comprises a cover bottom wall arranged to face the fan in the direction of the rotation axis, and a cover peripheral wall extending from the periphery of the cover bottom wall along the rotation axis and facing radially to the outer circumferential surface of the flywheel peripheral wall, and the gap between the cover peripheral wall and the flywheel peripheral wall may be larger than the gap between the cover bottom wall and the fan.

[0024] With this configuration, when cooling air is drawn in from inside the flywheel through the opening and discharged to the outside of the flywheel, a portion of the discharged cooling air passes between the cover peripheral wall and the wheel peripheral wall and is returned to the inside of the flywheel. This increases the flow rate of cooling air inside the flywheel. This improves the cooling performance of the rotating electric machine and enables the rotating electric machine to operate for a long period of time.

[0025] According to the present invention, the cooling performance of the rotating electrical machine can be improved, and the rotating electrical machine can be operated for a long period of time.

[0026] FIG. 1 is a perspective view of an electric motorcycle according to an embodiment of the present invention. FIG. 2 is a perspective view of a motorcycle drive device according to an embodiment of the present invention. FIG. 3 is an exploded perspective view of a motorcycle drive device according to an embodiment of the present invention. FIG. 4 is a perspective view of a flywheel and a fan according to an embodiment of the present invention. FIG. 5 is a perspective view of a flywheel and a fan according to an embodiment of the present invention. FIG. 6 is a plan view of the flywheel and the fan according to an embodiment of the present invention, viewed from the stator side. FIG. 7 is an explanatory diagram showing a schematic cross-section of a part of the fan according to an embodiment of the present invention. FIG. 8 is a side view of an electric motor according to an embodiment of the present invention, viewed from the radial direction, with the upper half of the motor cover cut away about a first axis of rotation. FIG. 9 is a graph showing temperature changes in an excitation coil according to an embodiment of the present invention. FIG. 10 is a graph showing changes in flow velocity of cooling air inside an electric motor according to an embodiment of the present invention. FIG. 11 is a perspective view of a flywheel and a fan according to a modified embodiment of the present invention. FIG. 12 is a cross-sectional view of a protrusion according to a modified embodiment of the present invention.

[0027] Next, an embodiment of the present invention will be described with reference to the drawings.

[0028] <Electric Motorcycle> Fig. 1 is a perspective view of an electric motorcycle 100 equipped with a motorcycle drive device 1 having an electric motor 2 as a rotating electric machine according to an embodiment of the present invention. Fig. 1 shows the rear portion of the electric motorcycle 100.

[0029] As shown in Figure 1, the electric motor 2 is used in, for example, a motorcycle drive device 1. The motorcycle drive device 1 is mounted on an electric motorcycle 100 and drives a rear wheel 101 of the electric motorcycle 100. The motorcycle drive device 1 is disposed below a seat 103 for a rider provided on a vehicle body 102 and further forward in the direction of travel than the rear wheel 101. A small-diameter pulley 52 (described later) of the motorcycle drive device 1 is connected to an axle 101a of the rear wheel 101 via a belt 104. As a result, power from the motorcycle drive device 1 is transmitted to the rear wheel 101 via the belt 104, causing the electric motorcycle 100 to travel.

[0030] <Two-wheel vehicle drive device> Figure 2 is a perspective view of the two-wheel vehicle drive device 1. Figure 3 is an exploded perspective view of the two-wheel vehicle drive device 1. As shown in Figures 2 and 3, the two-wheel vehicle drive device 1 includes an electric motor 2 and a transmission unit 3 connected to the electric motor 2 and transmitting the rotation of the electric motor 2 to the rear wheel 101.

[0031] <Transmission Unit> The transmission unit 3 includes a frame 40 and a transmission mechanism 70 supported by the frame 40. The frame 40 includes two arms 41, 42 (first arm 41, second arm 42) formed to be long in one direction, and a connecting support part 43 that connects one end of each of the two arms 41, 42 in the longitudinal direction. A mounting base 46 that protrudes on the opposite side of the arms 41, 42 is integrally formed with the connecting support part 43. The mounting base 46 is formed with an insertion hole 45a through which a bolt (not shown) is inserted.

[0032] The two arms 41, 42 are formed in a plate shape. The two arms 41, 42 are arranged opposite each other in the plate thickness direction via a connecting support portion 43. In the following description of the transmission unit 3, the direction perpendicular to the longitudinal direction and plate thickness direction of each arm 41, 42 is referred to as the short direction. A first mounting base 44 formed in a bifurcated shape is integrally molded on the tip of the first arm 41, of the two arms 41, 42, opposite the connecting support portion 43. An insertion hole 44a is formed in the first mounting base 44, through which a bolt (not shown) is inserted.

[0033] An annular first bearing housing 55 is integrally formed with the first arm 41 on the side of the connecting support portion 43. The first bearing housing 55 is provided with a bearing (not shown) for rotatably supporting a rotor shaft 9 (described later) of the electric motor 2. A plurality of stator support pillars 56 (e.g., three in this embodiment) protrude from one end surface of the first bearing housing 55 opposite the second arm 42 of the two arms 41, 42. A female thread portion 56a is formed on the tip surface of each stator support pillar 56. A stator 4 (described later) of the electric motor 2 is fixed to the stator support pillars 56.

[0034] A cover base 57 is attached to one end surface of the first bearing housing 55 so as to avoid the stator support pillar 56. The cover base 57 includes a base main body 58 formed in an annular shape so as to surround the periphery of the stator support pillar 56, and a plurality of (for example, four in this embodiment) base arms 59. The base main body 58 is fixed to one end surface of the first bearing housing 55. The base arms 59 are arranged at equal intervals around the circumferential direction of the base main body 58. The base arms 59 extend in the radial direction of the base main body 58. An insertion hole 59a through which a bolt 30 (see FIG. 2) is inserted is formed at the tip of each base arm 59. A motor cover 22, which will be described later, is fixed to the cover base 57.

[0035] Two second mounting bases 45 are integrally formed with the second arm 42, slightly away from the center in the longitudinal direction and toward the opposite side from the connecting support part 43. The two second mounting bases 45 are disposed on both sides of the second arm 42 in the short direction. The second mounting bases 45 have insertion holes 45a through which bolts (not shown) are inserted. Bolts (not shown) are inserted into the insertion holes 44a, 45a, 46a of the mounting bases 44, 45, 46, respectively, to fasten and fix the two-wheel vehicle drive unit 1 to the vehicle body 102.

[0036] An annular second bearing housing 61 is integrally molded on the second arm 42 on the side of the connecting support portion 43. The second bearing housing 61 is provided with a bearing (not shown) for rotatably supporting the rotor shaft 9. In this manner, the rotor shaft 9 is rotatably supported by the bearing housings 55, 61 of the two arms 41, 42 via bearings (not shown). One axial end 9a of the rotor shaft 9 protrudes through the first arm 41 in the thickness direction of the first arm 41. A first sprocket 47 is fitted and fixed to the rotor shaft 9 at a location that becomes the two arms 41, 42. The first sprocket 47 rotates integrally with the rotor shaft 9.

[0037] A second sprocket 48 is rotatably supported on the tip end sides of the two arms 41, 42. A second rotation axis A2 of the second sprocket 48 is parallel to the first rotation axis A1 of the rotor shaft 9 (first sprocket 47). In the following description, the directions of these rotation axes A1, A2 will not be distinguished and will simply be referred to as the axial direction.

[0038] The second sprocket 48 is formed by integrally molding a large-diameter sprocket 51 and a small-diameter pulley 52 that is arranged axially alongside the large-diameter sprocket 51. The large-diameter sprocket 51 is arranged on the same plane as the first sprocket 47. The first sprocket 47 and the large-diameter sprocket 51 are connected via an inner chain 53. The rotation of the first sprocket 47 is transmitted to the large-diameter sprocket 51 via the inner chain 53.

[0039] The small diameter pulley 52 is formed with a smaller diameter than the large diameter sprocket 51. This small diameter pulley 52 and the axle 101a of the rear wheel 101 are connected via a belt 104. As a result, when the rotor shaft 9 of the electric motor 2 rotates, the first sprocket 47 rotates integrally with the rotor shaft 9. The rotation of the first sprocket 47 is then transmitted to the second sprocket 48 (large diameter sprocket 51, small diameter pulley 52) via the inner chain 53. Furthermore, the rotation of the second sprocket 48 is transmitted to the axle 101a of the rear wheel 101 via the belt 104.

[0040] <Electric Motor> The electric motor 2 is a so-called outer rotor brushless motor. The electric motor 2 includes a stator 4 arranged on the tip surface of a stator support column 56, a rotor 5 rotatably mounted relative to the stator 4, a fan 18 mounted on the rotor 5, and a motor cover 22 that houses the stator 4, the rotor 5, and the fan 18. In the following description, the rotational direction of the rotor 5 will be simply referred to as the circumferential direction. The radial direction of the rotor 5, which is perpendicular to the axial and circumferential directions, will be simply referred to as the radial direction.

[0041] <Stator> The stator 4 includes a cylindrical stator core 6, a plurality of teeth 7 protruding radially outward from the outer peripheral surface of the stator core 6, and excitation coils 8 wound around each of the teeth 7. The teeth 7 are arranged radially when viewed in the axial direction. The stator core 6 is formed with bolt insertion holes 6a that are coaxial with the female threaded portions 56a of the stator support columns 56. Bolts (not shown) are inserted into these bolt insertion holes 6a from the side opposite the transmission unit 3, and the bolts are screwed into the female threaded portions 56a, thereby fastening and fixing the stator 4 to the stator support columns 56.

[0042] <Rotor> The rotor 5 includes a rotor shaft 9, a cylindrical flywheel 10 with a bottom that covers the stator 4 from the side opposite the transmission unit 3, and a plurality of magnets 11 provided on the flywheel 10. One end 9a of the rotor shaft 9 passes through the radial inside of the stator 4 and protrudes to the side of the stator 4 opposite the transmission unit 3. A male thread portion 9b is formed on one end 9a of the rotor shaft 9. The flywheel 10 is fastened and fixed to the male thread portion 9b.

[0043] <Flywheel> Figure 4 is a perspective view of the flywheel 10 and the fan 18. Figure 5 is a perspective view of the flywheel 10 and the fan 18, as seen from the axially opposite side to that of Figure 4. As shown in Figures 3 to 5, the flywheel 10 is formed of a magnetic material in a cylindrical shape with a bottom. That is, the flywheel 10 is provided with a disk-shaped bottom wall 12 that faces the stator 4 in the axial direction on the side opposite the transmission unit 3 of the stator 4 and has a radial center on the first rotation axis A1, and a cylindrical peripheral wall 13 that protrudes inward in the vehicle width direction from the outer circumferential edge of the bottom wall 12.

[0044] The peripheral wall 13 is disposed so as to surround the periphery of the stator core 6. That is, the inner peripheral surface of the peripheral wall 13 faces radially the outer end surfaces of the teeth 7 in the radial direction. A plurality of magnets 11 are disposed on the inner peripheral surface of the peripheral wall 13. A cylindrical, non-magnetic magnet cover 11a is provided on the inner surface of the magnet 11. The magnet 11 is covered by the magnet cover 11a.

[0045] At the radial center of the bottom wall 12, an annular fitting protrusion 71 is formed on the outer surface 12a opposite the stator 4. The fitting protrusion 71 is used to attach the fan 18. At the radial center of the bottom wall 12, a cylindrical fitting portion 14 that protrudes toward the stator 4 is integrally formed on the inner surface 12b that faces the stator 4. The outer diameter of the cylindrical fitting portion 14 is the same as the inner diameter of the fitting protrusion 71. Therefore, the fitting protrusion 71 and the cylindrical fitting portion 14 are integrated, just as if the cylindrical fitting portion 14 were fitted into the fitting protrusion 71.

[0046] The mating protrusion 71 and the cylindrical mating portion 14 are in communication. The end face of the cylindrical mating portion 14 opposite the stator 4 is recessed from the end face of the mating protrusion 71 opposite the stator 4. One end 9 a of the rotor shaft 9 protrudes into the recess 72 formed by this, via the cylindrical mating portion 14. The flywheel 10 is fastened and fixed to the rotor shaft 9 by tightening a nut (not shown) onto a male thread portion 9 b formed on one end 9 a of the rotor shaft 9.

[0047] The bottom wall 12 has a plurality of (e.g., three in this embodiment) female threaded portions 12c formed around the fitting protrusion 71. The female threaded portions 12c are arranged at equal intervals in the circumferential direction. The female threaded portions 12c are used to fasten and fix the fan 18 to the flywheel 10. The bottom wall 12 has a plurality of (e.g., three in this embodiment) flywheel ventilation holes 16 and a plurality of (e.g., twelve in this embodiment) confirmation windows 17 formed therein. The confirmation windows 17 are arranged at equal intervals in the circumferential direction along the outer periphery of the bottom wall 12. The confirmation windows 17 are formed in an arc shape centered on the first rotation axis A1 when viewed in the axial direction. The confirmation windows 17 are used to visually check the position of the magnet 11 covered by the magnet cover 11a.

[0048] The flywheel ventilation openings 16 are arranged radially inward of the confirmation window 17. The flywheel ventilation openings 16 are arranged circumferentially at equal intervals between adjacent female thread portions 12c. When viewed from the axial direction, the flywheel ventilation openings 16 are formed in an arc shape centered on the first rotation axis A1. The opening area of ​​the flywheel ventilation openings 16 is larger than the opening area of ​​the confirmation window 17. Both circumferential ends of the flywheel ventilation openings 16 form semicircular arc portions 16a. The flywheel ventilation openings 16 are used to pass cooling air generated by the fan 18 into the interior of the rotor 5.

[0049] The rotor 5 configured in this manner rotates in one direction about the first rotation axis A1, which will be referred to as the rotor rotation direction D (see FIG. 4) in the following description.

[0050] <Fan> FIG. 6 is a plan view of the flywheel 10 and the fan 18 as viewed from the stator 4 side. FIG. 7 is an explanatory diagram showing a schematic cross section of a portion of the fan 18. FIG. 7 corresponds to the cross section taken along line VII-VII in FIG. 4. As shown in FIGS. 3 to 7, the fan 18 is provided on the bottom wall 12 of the flywheel 10. The fan 18 is arranged concentrically with the rotor 5. The fan 18 includes a cylindrical boss 19 that fits onto the outer peripheral surface of a fitting protrusion 71 of the flywheel 10, and a plurality of fan blades 20 (e.g., 12 in this embodiment) that protrude radially outward from the outer peripheral surface of the boss 19. The fan 18 is radially positioned relative to the flywheel 10 by fitting the boss 19 into the fitting protrusion 71 of the flywheel 10.

[0051] A plurality of fixing seats 73 (for example, three in this embodiment) are integrally formed on the outer peripheral surface of the boss portion 19. The fixing seats 73 are arranged at equal intervals in the circumferential direction. Each fixing seat 73 has an insertion hole 73a that penetrates in the axial direction. The insertion hole 73a is arranged coaxially with the female thread portion 12c of the flywheel 10. A bolt (not shown) is inserted into the insertion hole 73a of each fixing seat 73 from the side opposite the stator 4 and screwed into the female thread portion 12c, thereby fastening and fixing the fan 18 to the flywheel 10.

[0052] Four fan blades 20 are arranged between adjacent fixed seats 73 in the circumferential direction. Hereinafter, the four fan blades 20 between the fixed seats 73 may be referred to as a first blade 81, a second blade 82, a third blade 83, and a fourth blade 84, in order from the downstream side in the rotor rotation direction D. Each fan blade 20 is formed in a rectangular shape that is long in the radial direction. A chamfered portion 20a is formed on the radially outer corner of each fan blade 20, facing away from the flywheel 10.

[0053] Each fan blade 20 is inclined toward the upstream side in the rotor rotation direction D. The inclination angle θ of each fan blade 20 with respect to the axial direction satisfies the following condition: 25°≦θ≦45° (1).

[0054] Of each fan blade 20, the second blade 82 and the third blade 83 are arranged above the longitudinal center of the flywheel ventilation port 16 of the flywheel 10. Of each fan blade 20, the fourth blade 84 is arranged on the arc portion 16a of the flywheel ventilation port 16 of the flywheel 10 on the upstream side in the rotor rotation direction D. Of each fan blade 20, the first blade 81 is arranged slightly further downstream than the arc portion 16a of the flywheel ventilation port 16 of the flywheel 10 on the downstream side in the rotor rotation direction D. In other words, only the first blade 81 is not arranged above the flywheel ventilation port 16.

[0055] The three blades, the second blade 82, the third blade 83, and the fourth blade 84, arranged above the flywheel ventilation opening 16, each have a protrusion 85, 86, or 87 formed at the end facing the flywheel 10. The protrusions 85, 86, or 87 are inserted into the flywheel ventilation opening 16. The three protrusions 85, 86, or 87 extend along the axial direction. Of the three protrusions 85, 86, or 87, the protrusion 85 of the second blade 82 and the protrusion 86 of the third blade 83 are formed in a rectangular shape that is long in the radial direction and spans the entire flywheel ventilation opening 16 in the radial direction. Of the three protrusions 85, 86, or 87, the protrusion 87 of the fourth blade 84 is formed in a semicircular shape that fills the arc portion 16a. The protrusion 87 of the fourth blade 84 flattens the upstream end of the flywheel ventilation opening 16 in the rotor rotation direction D along the radial direction.

[0056] Each of the protrusions 85, 86, and 87 protrudes from the inner surface 12b of the bottom wall 12 of the flywheel 10. The protrusion length H of each of the protrusions 85, 86, and 87 from the inner surface 12b is, for example, approximately 2 mm. The three second blades 82, the third blade 83, and the fourth blade 84 are arranged so that the opening area of ​​the flywheel ventilation port 16 is divided into three equal parts by the protrusions 85, 86, and 87. In other words, the fan blades 20 are not equally spaced circumferentially as a whole. Furthermore, the fourth blade 84 has a notch 84a formed on its radially inner side to avoid interference with the head of a bolt (not shown) inserted into the fixing seat 73. The notch 84a is curved.

[0057] <Motor Cover> Figure 8 is a side view of the electric motor 2 as viewed from the radial direction. Figure 8 shows the upper half of the motor cover 22 cut away about the first rotational axis A1. As shown in Figures 2, 3, and 8, the motor cover 22 is made of resin and formed into a cylindrical shape with a bottom so as to cover the stator 4, rotor 5, and fan 18 from the axial side opposite the transmission unit 3. The motor cover 22 includes a bottom wall 23 that faces the fan 18 in the axial direction and has its radial center coincident with the rotational axis A1, and a cylindrical peripheral wall 24 that protrudes from the outer periphery of the bottom wall 23 toward the electric motor 2.

[0058] An inclined portion 23a is formed on the outer periphery of the bottom wall 23, gradually extending radially outward toward the opening 22a of the motor cover 22. A plurality of first case ventilation holes 26 are formed on the entire bottom wall 23, excluding the inclined portion 23a. The bottom wall 23 has, for example, six regions R equally divided in the circumferential direction. A plurality of first case ventilation holes 26 are formed in each region R. Each first case ventilation hole 26 is formed in an arc shape centered on the rotation axis A1 when viewed in the axial direction. The plurality of first case ventilation holes 26 formed in each region R are arranged side by side in the radial direction. The first case ventilation holes 26 arranged radially outward have a longer circumferential length.

[0059] Furthermore, a plurality of second case ventilation holes 27 are formed in the motor cover 22 so as to straddle the inclined portion 23a of the bottom wall 23 and the peripheral wall 24. The second case ventilation holes 27 extend in the radial and axial directions. The plurality of second case ventilation holes 27 are arranged at equal intervals in the circumferential direction. A plurality of third case ventilation holes 28 are formed on the opening 22a side of the peripheral wall 24. The third case ventilation holes 28 are formed along the axial direction. The end of the third case ventilation holes 28 on the opening 22a side is open. The third case ventilation holes 28 are arranged at equal intervals in the circumferential direction.

[0060] A plurality of (for example, four in this embodiment) bolt seats 29 are formed on the outer peripheral surface of the peripheral wall 24 at the end on the opening 22a side. The bolt seats 29 are arranged at equal intervals in the circumferential direction. The bolt seats 29 are placed on the tip of the base arm 59. An insertion hole 29a is formed in the bolt seat 29 coaxially with the insertion hole 59a of the base arm 59. A bolt 30 is inserted through the insertion hole 29a of the bolt seat 29 and the insertion hole 59a of the base arm 59, and a nut 31 is screwed onto the tip of the bolt 30, thereby fastening and fixing the motor cover 22 to the cover base 57.

[0061] As shown in detail in FIG. 8 , when the motor cover 22 is fastened to the cover base 57, a first gap G1 is formed between the bottom wall 23 and the fan blades 20 in the axial direction. The chamfered flat portions 20a of the fan blades 20 face the inclined portions 23a of the motor cover 22 in the axial direction, thereby preventing interference between the fan blades 20 and the inclined portions 23a. A second gap G2 is formed between the inclined portions 23a and the chamfered flat portions 20a in the axial direction. The second gap G2 becomes larger toward the radially outward direction. A third gap G3 is also formed between the peripheral wall 24 of the motor cover 22 and the peripheral wall 13 of the flywheel 10 in the radial direction. The size of the third gap G3 is larger than the size of the first gap G1.

[0062] <Operation of Motorcycle Drive Device> Next, the operation of the motorcycle drive device 1 will be described. When the electric motor 2 is driven, a predetermined current is supplied to the excitation coil 8, which generates a predetermined magnetic flux linkage in the teeth 7. Magnetic attractive and repulsive forces are generated between this magnetic flux linkage and the magnets 11 of the rotor 5, causing the rotor 5 to continuously rotate (see arrow D in FIGS. 4 to 6 ). When the rotor 5 rotates, the rear wheel 101 is rotated via the transmission unit 3, causing the electric motorcycle 100 to travel.

[0063] When the rotor 5 of the electric motor 2 rotates, the fan 18 rotates integrally with the rotor 5. This generates negative pressure by the fan blades 20 of the fan 18, and outside air is drawn into the motor cover 22 through the opening 22a (third case ventilation opening 28) of the motor cover 22 and the bottom wall 23 (first case ventilation opening 26) of the motor cover 22 (see arrow Y1 in FIG. 8). The outside air drawn in through the opening 22a of the motor cover 22 passes through the stator 4 and the flywheel 10 in the axial direction as cooling air (see arrow Y2 in FIG. 8). This cools the stator 4 and the flywheel 10.

[0064] The cooling air that passes through the motor cover 22 in the axial direction further passes through the flywheel ventilation opening 16 of the flywheel 10, where it flows diagonally radially outward relative to the axial direction. The cooling air is then discharged through the second case ventilation opening 27 (see arrow Y3 in FIG. 8 ). In other words, the fan 18 functions as both an axial fan and a centrifugal fan. The fan blades 20 are formed with protrusions 85, 86, and 87 that are inserted into the flywheel ventilation opening 16. This allows the negative pressure generated by the fan blades 20 to be maintained through the flywheel ventilation opening 16 all the way to the inner surface 12b of the bottom wall 12. As a result, the cooling air efficiently passes through the flywheel ventilation opening 16.

[0065] Moreover, because the three protrusions 85, 86, and 87 extend along the axial direction, the protrusions 85, 86, and 87 do not obstruct the flow of cooling air passing through the flywheel ventilation opening 16. Furthermore, because the inclination angle θ of each fan blade 20 with respect to the axial direction satisfies the above-mentioned formula (1), the flywheel ventilation opening 16 is not covered by each fan blade 20, and negative pressure can be generated appropriately by each fan blade 20. The three second blades 82, third blade 83, and fourth blade 84 are arranged so that the opening area of ​​the flywheel ventilation opening 16 is divided into three equal parts by each of the protrusions 85, 86, and 87. This allows cooling air to pass evenly throughout the entire flywheel ventilation opening 16.

[0066] Of the two circumferential ends of the flywheel ventilation port 16, the arc portion 16a located upstream in the rotor rotation direction D (hereinafter simply referred to as the upstream end of the flywheel ventilation port 16) is prone to generating positive pressure due to wind cutting. If positive pressure were to be generated at the flywheel ventilation port 16, the flow of cooling air passing through the flywheel ventilation port 16 would be obstructed. Therefore, in this embodiment, the convex portion 87 of the fourth blade 84 flattens the upstream end of the flywheel ventilation port 16 along the radial direction. This makes it possible to prevent positive pressure from being generated at the upstream end of the flywheel ventilation port 16.

[0067] Here, the third gap G3 between the peripheral wall 24 of the motor cover 22 and the peripheral wall 13 of the flywheel 10 is larger than the first gap G1 between the bottom wall 23 and the fan blades 20. Therefore, not all of the cooling air passing through the flywheel ventilation opening 16 is discharged through the second case ventilation opening 27, but a portion is returned to the opening 22a of the motor cover 22 (inside the flywheel 10) through the third gap G3 (see arrow Y4 in FIG. 8 ). This returned cooling air, together with the outside air, passes through the stator 4 and the flywheel 10 again in the axial direction (see arrow Y2 in FIG. 8 ). This promotes cooling of the electric motor 2.

[0068] As described above, in the electric motor 2, the fan 18 is provided on the bottom wall 12 of the flywheel 10. The bottom wall 12 of the flywheel 10 is formed with a flywheel ventilation port 16. Of the fan blades 20 of the fan 18, three blades, namely a second blade 82, a third blade 83, and a fourth blade 84, are formed with protrusions 85, 86, and 87 that are positioned in the flywheel ventilation port 16, respectively. This allows the cooling air generated by the fan 18 to pass through the flywheel ventilation port 16 efficiently. Furthermore, the flow rate of the cooling air passing through the flywheel ventilation port 16 can be increased. This improves the cooling performance of the electric motor 2, enabling the electric motor 2 to operate for a long period of time.

[0069] 9 is a graph showing temperature changes of the excitation coil 8, with the vertical axis representing the temperature of the excitation coil 8 and the horizontal axis representing the phase current density supplied to the excitation coil 8. As shown in FIG. 9, it can be seen that the temperature of the excitation coil 8 is lower when the protrusions 85, 86, 87 are formed on the fan blade 20 compared to when the protrusions 85, 86, 87 are not formed on the fan blade 20.

[0070] Each of the protrusions 85, 86, and 87 protrudes from the inner surface 12b of the bottom wall 12 of the flywheel 10. This ensures that the negative pressure generated by the fan blades 20 is maintained through the flywheel ventilation opening 16 all the way to the inner surface 12b of the bottom wall 12. As a result, cooling air can be efficiently passed through the flywheel ventilation opening 16. The flow rate of the cooling air passing through the flywheel ventilation opening 16 can be reliably increased.

[0071] The protrusions 85, 86, 87 formed on each of the fan blades 82, 83, 84 allow the cooling air to flow smoothly from the protrusions 85, 86, 87 to the fan blades 82, 83, 84. This prevents unnecessary vortexes from being generated. Furthermore, since the protrusions 85, 86, 87 only need to be formed along with the fan blades 82, 83, 84, these protrusions 85, 86, 87 can be easily formed.

[0072] Flywheel ventilation port 16 is formed in an arc shape centered on first rotation axis A1 when viewed in the axial direction. Flywheel ventilation port 16 is provided with a plurality of protrusions 85, 86, 87. This allows cooling air to pass through flywheel ventilation port 16 more efficiently. In addition, the flow rate of the cooling air passing through flywheel ventilation port 16 can be reliably increased.

[0073] The three second blades 82, third blade 83, and fourth blade 84 are arranged so that the opening area of ​​the flywheel ventilation port 16 is divided into three equal parts by the respective convex portions 85, 86, and 87. This allows the cooling air to pass evenly throughout the entire flywheel ventilation port 16. This allows the cooling air to pass through the flywheel ventilation port 16 more efficiently.

[0074] The fan 18 includes a cylindrical boss 19 and a plurality of fan blades 20 protruding radially outward from the outer peripheral surface of the boss 19. The inclination angle θ of each fan blade 20 relative to the axial direction satisfies the above-described formula (1). Therefore, the fan 18 can efficiently generate cooling air while preventing the fan blades 20 from blocking the flywheel ventilation opening 16. By preventing the fan blades 20 from blocking the flywheel ventilation opening 16, the flow velocity of the cooling air within the electric motor 2 can be maintained at a predetermined value or higher. Furthermore, the cooling air that passes through the motor cover 22 in the axial direction (the cooling air drawn in from inside the flywheel 10 through the flywheel ventilation opening 16) can be discharged obliquely radially outward from the axial direction outside the flywheel 10. Therefore, even when the motor cover 22 is provided, the cooling air can be prevented from being blown forcefully against the motor cover 22. As a result, the cooling air can be smoothly passed through the flywheel ventilation opening 16.

[0075] Figure 10 is a graph showing changes in the flow velocity of the cooling air inside the electric motor 2, with the vertical axis representing the flow velocity of the cooling air and the horizontal axis representing the inclination angle θ of the fan blades 20 with respect to the axial direction. In Figure 10, the flow velocity of the cooling air inside the electric motor 2 was measured at four locations. Specifically, the flow velocity of the cooling air was measured at four locations equally spaced circumferentially around the axial center of the stator core 6. As shown in Figure 10, when the inclination angle θ of each fan blade 20 with respect to the axial direction satisfies the above formula (1), it can be confirmed that the flow velocity of the cooling air inside the electric motor 2 is maintained at a predetermined value or higher.

[0076] The three protrusions 85, 86, and 87 extend along the axial direction. This prevents the protrusions 85, 86, and 87 from interfering with the flow of cooling air passing through the flywheel ventilation opening 16. This allows the cooling air to pass through the flywheel ventilation opening 16 more efficiently. Furthermore, the flow speed of the cooling air passing through the flywheel ventilation opening 16 can be reliably increased.

[0077] The flywheel ventilation port 16 is formed in a circular arc shape that is long in the circumferential direction. Both circumferential ends of the flywheel ventilation port 16 are formed flat along the radial direction. This prevents positive pressure from being generated at the upstream end of the flywheel ventilation port 16. This allows the cooling air to pass through the flywheel ventilation port 16 more efficiently. Furthermore, the flow rate of the cooling air passing through the flywheel ventilation port 16 can be reliably increased.

[0078] The third gap G3 between the peripheral wall 24 of the motor cover 22 and the peripheral wall 13 of the flywheel 10 is larger than the first gap G1 between the bottom wall 23 and the fan blades 20. This allows a portion of the cooling air that has passed through the flywheel ventilation opening 16 to return to the opening 22a of the motor cover 22 (inside the flywheel 10) via the third gap G3. This increases the flow rate of the cooling air inside the flywheel 10. This improves the cooling performance of the electric motor 2, enabling the electric motor 2 to operate for a longer period of time.

[0079] This will improve the cooling performance of the electric motor 2 and enable it to operate for longer periods of time, making it possible to contribute to Goal 7 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Ensure access to affordable, reliable, sustainable and modern energy for all."

[0080] [Modification] Next, a modification of the above-described embodiment will be described with reference to Figures 11 and 12. Figure 11 is a perspective view of the flywheel 10 and the fan 18. Figure 11 corresponds to the above-described Figure 5. Figure 12 is an explanatory diagram showing a cross section of the protrusions 95, 96, and 97 inserted into the flywheel ventilation opening 16. Figure 12 corresponds to the above-described Figure 7.

[0081] In the above embodiment, the three fan blades 20 of the fan 18, the second blade 82, the third blade 83, and the fourth blade 84, are respectively formed with protrusions 85, 86, and 87 that are positioned at the flywheel ventilation opening 16. However, this is not limited to this, and as shown in Figures 11 and 12, protrusions 95, 96, and 97 may be formed on the flywheel 10 instead of the protrusions 85, 86, and 87. In this case, the second blade 82, the third blade 83, and the fourth blade 84 do not have the protrusions 85, 86, and 87.

[0082] More specifically, pillar portions 91, 92, 93 that span the entire radial direction of the flywheel ventilation port 16 are formed on the bottom wall 12 of the flywheel 10 at positions corresponding to the flywheel 10-side ends 82a, 83a, 84b of the second blade 82, the third blade 83, and the fourth blade 84. Of these pillar portions 91, 92, 93, the pillar portion 93 that is located most upstream in the rotor rotation direction D fills the arc portion 16a on the upstream side of the flywheel ventilation port 16 in the rotor rotation direction D. The ends 82a, 83a, 84b of the corresponding second blade 82, third blade 83, and fourth blade 84 abut against the outer surfaces 91a, 92a, 93a of the pillar portions 91, 92, 93.

[0083] The downstream side of each of the pillars 91, 92, 93 is folded back toward the inner surface 12b of the bottom wall 12 to form convex portions 95, 96, 97. The shapes of each of the convex portions 95, 96, 97 are similar to the shapes of the convex portions 85 of the second blade 82 and the convex portions 86 of the third blade 83 in the above-described embodiment. That is, each of the convex portions 95, 96, 97 is formed in a rectangular shape that is long in the radial direction so as to span the entire flywheel ventilation port 16 in the radial direction.

[0084] The opening area of ​​the flywheel ventilation port 16 is divided into three equal parts by the protrusions 95, 96, and 97. Each of the protrusions 95, 96, and 97 protrudes from the inner surface 12b of the bottom wall 12 of the flywheel 10. The protrusion length H of each of the protrusions 95, 96, and 97 from the inner surface 12b is, for example, about 2 mm.

[0085] The downstream side surfaces 95a, 96a, 97a of the convex portions 95, 96, 97 in the rotor rotation direction D are smoothly connected to the downstream side surfaces 82b, 83b, 84c of the corresponding second blade 82, third blade 83, and fourth blade 84 in the rotor rotation direction D. In other words, the downstream side surfaces 95a, 96a, 97a of the convex portions 95, 96, 97 in the rotor rotation direction D are connected without any steps to the downstream side surfaces 82b, 83b, 84c of the corresponding second blade 82, third blade 83, and fourth blade 84 in the rotor rotation direction D.

[0086] The upstream end of the flywheel ventilation port 16 is not limited to being formed flat along the radial direction by the convex portion 87 of the fourth blade 84, as in this modification. That is, as in this modification, the upstream end of the flywheel ventilation port 16 itself in the rotor rotation direction D (the pillar portion 93 and the convex portion 97) may form this upstream end flat along the radial direction. In this way, forming the upstream end of the flywheel ventilation port 16 flat along the radial direction may be formed by using the convex portion 87, or may be formed by the shape of the flywheel ventilation port 16 itself.

[0087] The above modified example can also achieve the same effects as the above embodiment.

[0088] Furthermore, the present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention. For example, in the above-described embodiment, the electric motor 2 is described as being used in a two-wheeled vehicle drive device 1. However, the present invention is not limited to this, and the configuration of the electric motor 2 can be adopted in various devices.

[0089] In the above embodiment, the electric motor 2 is used as the rotating electric machine of the two-wheeled vehicle drive device 1. However, this is not limited to this, and the electric motor 2 may also be configured to be used as a generator. In the above embodiment, the two-wheeled vehicle drive device 1 is described as including one electric motor 2. However, this is not limited to this, and multiple electric motors 2 may be provided. For example, an electric motor 2 may be disposed on each side of the rotor shaft 9 in the axial direction. The configuration of the transmission unit 3 is also not limited to the above configuration, and it is sufficient if it can transmit the rotation of the electric motor 2 to the rear wheel 101.

[0090] In the above-described embodiment and modified examples, three protrusions 85, 86, 87, 95, 96, and 97 are arranged in one flywheel ventilation opening 16. However, this is not limited to this, and it is sufficient that at least one protrusion is arranged in at least one of the flywheel ventilation openings 16.

[0091] In the above-described embodiment and modified examples, the protrusions 85, 86, and 87 formed on the fan blade 20 and the protrusions 95, 96, and 97 formed on the flywheel 10 protrude from the inner surface 12b of the bottom wall 12 of the flywheel 10. However, this is not limiting, and the protrusions 85, 86, 87, 95, 96, and 97 do not have to protrude from the inner surface 12b of the bottom wall 12. It is sufficient that the protrusions 85, 86, 87, 95, 96, and 97 are disposed in the flywheel ventilation openings 16.

[0092] In the above embodiment, the protrusions 85, 86, 87, 95, 96, and 97 are formed on the fan blades 20 and the flywheel 10, respectively. However, this is not limiting, and the protrusions 85, 86, 87, 95, 96, and 97 may be located on the ends of the fan blades 20 (second blade 82, third blade 83, and fourth blade 84) facing the flywheel 10. They may be separate from the fan blades 20 and the flywheel 10. The protrusions 85, 86, 87, 95, 96, and 97 may be supported by members separate from the fan blades 20 and the flywheel 10.

[0093] In the above embodiment, the flywheel ventilation opening 16 is described as being formed in an arc shape centered on the first rotation axis A1 when viewed in the axial direction. However, this is not limited to this, and the shape of the flywheel ventilation opening 16 may be any shape. For example, the shape of the flywheel ventilation opening 16 may be circular. It is preferable that the shape of the flywheel ventilation opening 16 is arc-shaped when viewed in the axial direction.

[0094] In the above-described embodiment and modified examples, the protrusion length H of each of the protrusions 85, 86, 87, 95, 96, and 97 from the inner surface 12b is, for example, about 2 mm. However, this is not limited to this, and the protrusion length H can be determined arbitrarily. The protrusions 85, 86, 87, 95, 96, and 97 may be protruded so as not to interfere with the stator 4.

[0095] In the above-described embodiment and modified examples, the protrusions 85 of the second blade 82, the protrusions 86 of the third blade 83, and the protrusions 95, 96, and 97 formed on the respective pillars 91, 92, and 93 are formed in a rectangular shape that is long in the radial direction so as to span the entire flywheel ventilation port 16 in the radial direction. However, this is not limited to this, and the protrusions do not have to be formed so as to span the entire flywheel ventilation port 16 in the radial direction. It is preferable that the protrusions are formed so as to partition the flywheel ventilation port 16 to some extent.

[0096] In the above-described embodiment and modified examples, the protrusions 85, 86, 87, 95, 96, and 97 are arranged so that the opening area of ​​the flywheel ventilation port 16 is divided into three equal parts. However, this is not limited to this, and the opening area of ​​the flywheel ventilation port 16 does not have to be divided into equal parts by the protrusions 85, 86, and 87. For example, the fan blades 20 may be arranged at equal intervals in the circumferential direction as a whole.

[0097] 1...two-wheeled vehicle drive device, 2...electric motor (rotating electric machine), 3...transmission unit, 4...stator, 5...rotor, 6...stator core, 6a...bolt insertion hole, 7...teeth, 8...excitation coil, 9...rotor shaft, 9a...one end, 9b...male thread portion, 10...flywheel, 11...magnet, 11a...magnet cover, 12...bottom wall (flywheel bottom wall), 12a...outer surface, 12b...inner surface, 12c...female thread portion, 13...circumferential wall (flywheel peripheral wall), 14...cylindrical fitting portion, 16...flywheel ventilation hole (opening), 16a...arc portion, 17...inspection window, 18...fan , 19... boss portion (cylindrical portion), 20... fan blade, 20a... chamfered portion, 22... motor cover (cover), 22a... opening, 23... bottom wall (cover bottom wall), 23a... inclined portion, 24... peripheral wall (cover peripheral wall), 26... first case ventilation hole, 27... second case ventilation hole, 28... third case ventilation hole, 29... bolt seat, 29a... insertion hole, 30... bolt, 31... nut, 40... frame, 41... first arm, 42... second arm, 43... connecting support portion, 44... first mounting base, 44a... insertion hole, 45... second mounting base, 45a... insertion hole, 46... mounting base, 46a... insertion hole hole, 47...first sprocket, 48...second sprocket, 51...large diameter sprocket, 52...small diameter pulley, 53...inner chain, 55...first bearing housing, 56...stator support column, 56a...female thread portion, 57...cover base, 58...base body, 59...base arm, 59a...through hole, 61...second bearing housing, 70...transmission mechanism, 71...fitting convex portion, 72...recess, 73...fixing seat, 73a...through hole, 81...first blade, 82...second blade, 82a...end, 82b...side surface, 83...third blade, 83a...end, 83b...side surface, 84...fourth blade do, 84a...notch portion, 84b...end portion, 84c...side surface, 85...protrusion portion, 86...protrusion portion, 87...protrusion portion, 91...pillar portion, 91a...outer surface, 92...pillar portion, 92a...outer surface, 93...pillar portion, 93a...outer surface, 95...protrusion portion, 95a...side surface, 96...protrusion portion, 96a...side surface, 97...protrusion portion, 97a...side surface, 100...electric motorcycle, 101...rear wheel, 101a...axle, 102...vehicle body, 103...seat, 104...belt, A1...first rotation axis, A2...second rotation axis, D...rotor rotation direction, G1...first gap, G2...second gap, G3...third gap, H...projection length, R...area, θ...tilt angle

Claims

1. A rotating electric machine comprising: a stator around which an excitation coil is wound to generate a magnetic field; a flywheel rotatably mounted relative to the stator; and a fan mounted on the flywheel and rotating integrally with the flywheel, wherein the flywheel comprises: a flywheel bottom wall arranged to face the stator in the direction of the rotation axis of the flywheel and having an opening; a flywheel peripheral wall extending from the periphery of the flywheel bottom wall along the rotation axis, radially facing the outer circumferential surface of the stator and having a magnet mounted thereon; and a protrusion arranged within the opening, wherein the fan is mounted on an outer surface of the flywheel bottom wall opposite the stator, and the fan has a plurality of fan blades arranged side by side in the circumferential direction, and the protrusion is arranged at the end of the fan blade on the flywheel bottom wall side.

2. A rotating electric machine according to claim 1, characterized in that the convex portion is formed to protrude from the fan blade.

3. A rotating electric machine according to claim 1 or 2, characterized in that the convex portion protrudes onto an inner surface of the bottom wall of the flywheel on the stator side.

4. A rotating electric machine according to claim 1 or 2, characterized in that the openings are formed in an arc shape that is long in the circumferential direction, and a plurality of the protrusions are inserted into one of the openings.

5. A rotating electric machine according to claim 4, characterized in that the multiple protrusions inserted into one of the openings are arranged so as to evenly divide the opening in the circumferential direction.

6. A rotating electric machine as described in claim 1 or claim 2, characterized in that the fan has a boss portion with a cylindrical portion arranged on the rotation axis of the bottom wall of the flywheel, the multiple fan blades protrude radially outward from the outer circumferential surface of the cylindrical portion, and the inclination angle θ of each fan blade with respect to the rotation axis satisfies 25°≦θ≦45°.

7. A rotating electric machine according to claim 6, characterized in that the protrusion extends along the axis of rotation.

8. A rotating electric machine according to claim 1 or 2, characterized in that the opening is formed in a long arc shape in the circumferential direction, and of both circumferential ends of the opening, the rear side in the direction of rotation of the flywheel is formed flat so as to extend radially.

9. A rotating electric machine as described in claim 1 or claim 2, characterized in that it comprises a cover covering the flywheel from the outside, the cover comprising: a cover bottom wall arranged to face the fan in the direction of the rotation axis; and a cover peripheral wall extending from the periphery of the cover bottom wall along the rotation axis and radially facing an outer circumferential surface of the flywheel peripheral wall, wherein a gap between the cover peripheral wall and the flywheel peripheral wall is larger than the gap between the cover bottom wall and the fan.

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