Brushless motor

Abstract

A brushless motor (10) comprising the following: a motor shaft (12); a rotor housing (26) with a circular (cylindrical) shaft bearing housing section (30) provided on the radial outside of the motor shaft (12) and an outer cylindrical section (32) formed on the radial outside of the shaft bearing housing section (30); a shaft bearing (38) which is housed in the shaft bearing housing section (30) and attached to the motor shaft (12); a stator core (40) housed inside the outer cylinder section (32), comprising an annular unit (48) provided on the radial outside of the shaft bearing housing section (30) and a plurality of teeth (50) formed in a radial pattern on the periphery of the annular unit (48); an insulator (42) comprising an annular insulating section (56) covering the annular unit (48) and a plurality of tooth insulating sections (58), each covering the plurality of teeth (50); a plurality of winding coil sections (60) wound around the teeth (50) and over the tooth insulating sections (58); a central section (18) comprising a main body section (62) which is arranged opposite an opening of the outer cylinder section (32) and which supports the motor shaft (12) and the stator core (40); a first water stop wall (82) which is formed in a ring shape along the circumferential direction of the motor shaft (12) and extends along an axial direction of the motor shaft (12) from the annular insulating section (56) in the direction of the main body section (62); and a second water stop wall (84) which is formed in a ring shape along the circumferential direction of the motor shaft (12) and extends along the axial direction of the motor shaft (12) from the main body section (62) in the direction of the annular insulating section (56) and which together with the first water stop wall (82) forms a labyrinth structure arranged on a radial inside of the plurality of winding coil sections (60).

Description

BACKGROUND Technical area

[0001] The present invention relates to a brushless motor. Related technology

[0002] A conventional brushless external rotor motor comprising a motor shaft, a rotor housing rotatably supported by a shaft bearing on the motor shaft, and a stator housed in the rotor housing is known from the Japanese patent application JP 2014 - 36 525 A.

[0003] In such brushless motors, the performance of the shaft bearing can decrease if water droplets penetrate the interior of the rotor housing. Therefore, a brushless motor with a labyrinth structure has been proposed in which the shaft bearing is not exposed to water (see, e.g., JP 2007 - 53 844 A).

[0004] Among brushed motors of this type are also motors used as vehicle blower motors (see, for example, JP H09 - 261 915 A). This vehicle blower motor is attached to the vehicle body by means of a casing. A mounting section provided on a central section of the blower is attached to a rotor housing within this blower motor, so that the blower rotates together with the rotor housing.

[0005] In the vehicle blower motor described above, gaps in an outer circumferential section of the blower motor, particularly those formed between the rotor housing, the blower mounting section, and the casing, can serve as entry points for water droplets. Consequently, a labyrinth structure formed by the rotor housing, the blower mounting section, and the casing could be provided on the outer circumferential section of the blower motor to prevent water ingress.

[0006] In such cases, the flow of cooling air, which cools a winding coil section wound around the stator teeth and is expelled towards the radial outer surface of the blower motor, can be obstructed by the labyrinth structure. Therefore, it is desirable to ensure cooling of the winding coil section while simultaneously preventing the shaft bearing from being exposed to water.

[0007] Other brushless motors are known from the US 9 006 944 B2, the JP 2014 - 108 030 A and the JP 2010 - 41 853 A. SUMMARY

[0008] The present disclosure provides a brushless motor that is capable of ensuring the cooling of the winding coil section and at the same time preventing the shaft bearing from being exposed to water.

[0009] A first aspect of the present disclosure is a brushless motor comprising: a motor shaft; a rotor housing with a circular (cylindrical) provided on the radial outside of the motor shaft

[0010] a shaft bearing housing section and an outer cylindrical section formed on the radial outside of the shaft bearing housing section; a shaft bearing housed in the shaft bearing housing section and attached to the motor shaft; a stator core housed inside the outer cylindrical section, comprising an annular unit provided on the radial outside of the shaft bearing housing section and a plurality of teeth formed in a radial pattern on the periphery of the annular unit; an insulator having an annular insulating section covering the annular unit and a plurality of tooth insulating sections, each covering the plurality of teeth; a plurality of winding coil sections wound around the teeth and over the tooth insulating sections;a central section comprising a main body section arranged opposite an opening of the outer cylinder section and supporting the motor shaft and stator core; a first water stop wall formed in an annular shape along the circumferential direction of the motor shaft and extending along the axial direction of the motor shaft from the annular insulating section towards the main body section; and a second water stop wall formed in an annular shape along the circumferential direction of the motor shaft and extending along the axial direction of the motor shaft from the main body section towards the annular insulating section, forming a labyrinth structure together with the first water stop wall on the radial inner surface of the plurality of winding coil sections.

[0011] In the first aspect of the brushless motor, a labyrinth structure consists of a first water stop wall and a second water stop wall, which are formed in annular shapes along the circumferential direction of the motor shaft. Within the labyrinth structure, the first water stop wall extends along the axial direction of the motor shaft from the annular insulating section towards the main body section, and the second water stop wall extends along the axial direction of the motor shaft from the main body section towards the annular insulating section.

[0012] Consequently, even in a case where, for example, a water droplet has penetrated through the gap between the circumferential edge section of the rotor housing and the main body section of the center section, and is approaching the shaft bearing side between the stator core and the main body section, the penetration of the water droplet by the labyrinth structure described above can be prevented. Therefore, exposure of the shaft bearing to water can be prevented.

[0013] Furthermore, the labyrinth structure is formed on the radial inner side of the multitude of winding coil sections arranged in a ring shape. Since the labyrinth structure is not located in the flow path of the cooling air that cools the winding coil sections and is expelled towards the radial outer side of the brushless motor, it cannot obstruct the flow of the cooling air.

[0014] A second aspect of the present disclosure is the brushless motor of the first aspect, wherein the first water stop wall is formed on the radial inside of the second water stop wall.

[0015] Since the first water stop wall in the second aspect of the brushless motor is located on the radial inner side of the second water stop wall, it is positioned closer to the outer peripheral side of the motor shaft (the outer peripheral side of the motor shaft along which water droplets flow), which can serve as a path for water droplets to penetrate the shaft bearing. Consequently, the first water stop wall can even more effectively prevent the shaft bearing from being exposed to water.

[0016] A third aspect of the present disclosure is the brushless motor of the second aspect, wherein an extension section is provided on the annular insulating section, which extends in the direction of the radial outside of the first water stop wall, wherein a leading end section of the second water stop wall is opposite the extension section along the axial direction of the motor shaft.

[0017] Since, in the third aspect of the brushless motor and the labyrinth structure described above, the extension section formed on the annular insulating section and the leading end section of the second water-stop wall are opposite each other along the axial direction of the motor shaft, it is possible to prevent water droplets from penetrating between the extension section and the leading end section of the second water-stop wall. This improves the water-stopping capability of the labyrinth structure.

[0018] A fourth aspect of the present disclosure is the brushless motor of the third aspect, wherein a radially outer end section of the extension section projects further towards the radial outside of the extension section than the leading end section of the second water stop wall.

[0019] In the fourth aspect of the brushless motor, a radially outer end section of the extension section projects further towards the radial outside of the extension section than the leading end section of the second water-stop wall. Since the flow of water droplets can be more effectively impeded at the section of the extension section that projects further towards the radial outside than the second water-stop wall, this can also improve the water-stopping capability of the labyrinth structure.

[0020] A fifth aspect of the present disclosure is the brushless motor according to one of aspects one to four, which further comprises: a third water stop wall formed in a ring shape along the circumferential direction of the motor shaft and extending along the axial direction of the motor shaft from the annular insulating section towards the main body section;and a fourth water stop wall, which is formed in a ring shape along the circumferential direction of the motor shaft and extends along the axial direction of the motor shaft from the main body section towards the annular insulating section, wherein the first water stop wall and the second water stop wall form an inner labyrinth structure and the third water stop wall and the fourth water stop wall form an outer labyrinth structure, which is arranged on the radial inside of the plurality of winding coil sections and on the radial outside of the inner labyrinth structure.

[0021] In the brushless motor of the fifth aspect, in addition to the inner labyrinth structure on the radial inner surface of the multitude of winding coil sections, an outer labyrinth structure is formed. This two-layer labyrinth structure allows for even more effective protection against water exposure of the shaft bearings.

[0022] Similar to the inner labyrinth structure described above, the outer labyrinth structure is also formed on the radial inner side of the multitude of winding coil sections arranged in a ring shape. Since the outer labyrinth structure is not located in the flow path of the cooling air that cools the winding coil sections and is expelled towards the radial outer side of the brushless motor, it cannot obstruct the flow of the cooling air.

[0023] A sixth aspect of the present disclosure is the brushless motor of the fifth aspect, wherein the leading end face of the first water stop wall overlaps with the leading end face of the second water stop wall along the axial direction of the motor shaft, and the leading end face of the third water stop wall overlaps with the leading end face of the fourth water stop wall along the axial direction of the motor shaft.

[0024] In the brushless motor of the sixth aspect, the leading end face of the first water stop wall overlaps with the leading end face of the second water stop wall along the axial direction of the motor shaft. The water-stopping capability of the inner labyrinth structure is thus further improved, as the flow path within the inner labyrinth structure is curved and the length of the flow path is greater.

[0025] Furthermore, the leading end face of the third water stop wall overlaps with the leading end face of the fourth water stop wall of the motor shaft. The water-stopping capability of the outer labyrinth structure can thus be further improved, since the flow path within the outer labyrinth structure is curved and the length of the flow path is greater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Exemplary manifestations of the present revelation are described in detail with reference to the following figures, wherein: Fig. 1 a vertical cross-section of a brushless motor according to an exemplary embodiment as disclosed herein; Fig. 2 a perspective view of one of the in Fig. 1 is the insulator shown; Fig. 3 a perspective view of a peripheral section of the in Fig. 1 depicted inner labyrinth structure and outer labyrinth structure; Fig. 4 a vertical cross-section of the in Fig. The inner labyrinth structure shown in section 3 is; and Fig. 5 a vertical cross-section of the in Fig. The outer labyrinth structure shown in section 4 is... DETAILED DESCRIPTION

[0027] With reference to the drawings, an exemplary embodiment of the present disclosure is described below.

[0028] As in Fig. Figure 1 shows a brushless motor 10 according to the exemplary embodiment of the present disclosure comprising a motor shaft 12, a rotor 14, a stator 16, a center piece 18, a printed circuit board 20, a connecting element 22 and a printed circuit board housing 24.

[0029] The rotor 14 comprises a rotor housing 26 and a rotor magnet 28. The rotor housing 26 comprises a circular (cylindrical)

[0030] The shaft bearing housing section 30, which is provided on the radial outside of the motor shaft 12, and a cylindrical outer cylinder section 32 with a bottom formed on the radial outside of the shaft bearing housing section 30. The rotor magnet 28 is arranged on an inner peripheral side of the outer cylinder section 32.

[0031] An opening is located on one axial side of the outer cylinder section 32, and a lower wall section 34 is formed on the other radial side of the outer cylinder section 32. The shaft bearing housing section 30 described above extends from a central section of the lower wall section 34 to the side of the central piece 18. The lower wall section 34 has a plurality of ventilation openings 36.

[0032] The shaft bearing housing section 30 houses a pair of shaft bearings 38 to which the motor shaft 12 is attached. The two axial sides of the shaft bearing housing section 30 are open, and one end of the motor shaft 12 projects from the shaft bearing housing section 30 towards the center section 18 by passing through the opening on one axial side of the shaft bearing housing section 30.

[0033] The stator 16 comprises a stator core 40, a pair of insulators 42, 44, and a plurality of windings 46. The stator core 40 includes an annular unit 48 formed on an axial outer surface of the shaft bearing housing section 30 and a plurality of teeth 50 arranged in a radial pattern around the periphery of the annular unit 48. The stator core 40 is located within the outer cylindrical section 32 between the shaft bearing housing section 30 and the rotor magnet 28 along the radial direction. A through-hole 54 is provided in the annular unit 48 along the axial direction of the motor shaft 12, into which a screw 52 is inserted.

[0034] The pair of insulators 42, 44 is divided along the axial direction of the stator core 40 and attached to the stator core 40 from both axial sides. Each pair of insulators 42, 44 has an annular insulating section 56 covering the annular unit 48, and a plurality of tooth insulating sections 58 covering the respective plurality of teeth 50 (see Fig. 2 and Fig. 3).

[0035] Of the pair of insulators 42, 44, the insulator 42 arranged on an axial side (i.e. the side of the center piece 18) of the stator core 40 is an example of an ‘insulator’ according to the present disclosure.

[0036] The multitude of windings 46 comprises a multitude of winding coil sections 60, which are wound around the teeth 50 and the tooth insulation sections 58. The winding coil sections 60 can be wound around one of the teeth 50 by means of a concentrated winding or around several teeth 50 by means of a distributed winding.

[0037] The central section 18 comprises a flat, plate-shaped main body section 62. The main body section 62 is arranged opposite the opening of the outer cylinder section 32. A concave shaft support section 64 is provided on a central portion of the main body section 62, which is open on the side of the shaft bearing housing section 30, and the motor shaft 12 is inserted into the shaft support section 64 so that it is held therein. The main body section 62 has a bulge 66 that projects further towards the radial outside in the direction of the side of the stator 16 along the axial direction of the motor shaft 12 than the shaft support section 64.

[0038] The plurality of bulges 66 are arranged at intervals along the circumferential direction of the motor shaft 12. Each of the bulges 66 has a screw opening 68 that is open on the side of the stator core 40. The screw opening 68 is located at a position corresponding to the through-hole 54 formed in the annular unit 48 of the stator core 40 described above. Once the screw 52 has been passed through the through-hole 54, it is inserted into the screw opening 68 such that the stator core 40 is fastened to the main body section 62.

[0039] The printed circuit board 20 is arranged on the side of the main body section 62 opposite the side of the stator core 40. An electronic circuit for switching the transmission to the plurality of winding coil sections 60 described above is formed on the printed circuit board 20. The connecting element 22 is arranged on one side of the main body section 62. A connecting section 70 is located on the connecting element 22, and a terminal provided on the connecting section 70 is electrically connected to the electronic circuit formed on the printed circuit board 20.

[0040] The printed circuit board housing 24 has a flattened box shape and is attached to the main body section 62 on the side opposite the stator core 40. A housing space 72, in which the printed circuit board 20 is located, is situated between the printed circuit board housing 24 and the main body section 62.

[0041] The brushless motor 10 is suitable, for example, as a vehicle blower motor, and the motor shaft 12 is attached to the vehicle body in such a way that it is arranged along a horizontal direction.

[0042] A blower 100 comprises a mounting section provided on a central section of the blower 100 and a plurality of vanes 104 arranged on the outer edge of the mounting section 102. Like the rotor housing 26, the mounting section 102 comprises an outer cylindrical section 112 and a lower wall section 114 and is attached to the rotor housing 26 so that it covers the rotor housing 26.

[0043] When the power supply to the plurality of winding coil sections 60 in the brushless motor 10 is switched by means of the electronic circuit formed on the circuit board 20, the stator 16 generates a rotating magnetic field, and the rotor 14 rotates due to the attractive and repulsive forces generated between the rotating magnetic field and the rotor magnet 28.

[0044] When the blower 100 rotates together with the rotor 14, a flow of cooling air W is generated, which cools the winding coil sections 60 through the slots formed between the plurality of teeth 50. The cooling air W is expelled through the ventilation holes 36 provided on the lower wall section 34 towards the outside of the rotor housing 26 and also towards the radial outside of the brushless motor 10 between the lower wall sections 34, 114 and between the outer cylinder sections 32, the outer cylinder section 112 of the mounting section 102 and the rotor housing 26.

[0045] The following describes the inner labyrinth structure 80 and the outer labyrinth structure 90 formed on the brushless motor 10 according to the present disclosure.

[0046] As in the Fig. 3, Fig. 4 to Fig. As shown in Figure 5, the brushless motor 10 has an inner labyrinth structure 80 and an outer labyrinth structure 90. As shown in Fig. 3 and Fig. As shown in Figure 4, the inner labyrinth structure 80 is formed by a first water stop wall 82 and a second water stop wall 84, which are arranged in a ring shape along the circumferential direction of the motor shaft 12.

[0047] The first water stop wall 82 extends along the axial direction of the motor shaft 12 from the annular insulating section 56 formed on one of the pair of insulators 42 towards the main body section 62. The second water stop wall 84, on the other hand, extends along the axial direction of the motor shaft 12 from the main body section 62 (a peripheral section of the shaft support section 64) towards the annular insulating section 56.

[0048] The first water stop wall 82 is arranged on the radial inner side of the second water stop wall 84, and the leading end side of the first water stop wall 82 and the leading end side of the second water stop wall 84 overlap along the axial direction of the motor shaft 12. It is ensured that a gap runs between the first water stop wall 82 and the second water stop wall 84 along the radial direction.

[0049] A leading end section of the first water stop wall 82 lies opposite the main body section 62 (the peripheral section of the shaft support section 64) along the axial direction of the motor shaft 12. Furthermore, an extension section 86 is formed on the annular insulating section 56, which extends towards the radial outer side of the first water stop wall 82, and the leading end section of the second water stop wall 84 lies opposite the extension section 86 along the axial direction of the motor shaft 12.

[0050] As in Fig. As shown in Figure 4, an end section 86A extends further along the radial outer side of the extension section 86 than the leading end section of the second water stop wall 84. Gaps are ensured between the leading end section of the first water stop wall 82 and the main body section 62, as well as between the leading end section of the second water stop wall 84 and the extension section 86.

[0051] As in Fig. As shown in Figure 1, the inner labyrinth structure 80 formed by the first water stop wall 82 and the second water stop wall 84 is arranged on the radial inside of the plurality of winding coil sections 60, i.e., between the shaft bearing housing section 30 and the main body section 62 (the peripheral section of the shaft support section 64) along the axial direction. The inner labyrinth structure 80 is an example of a labyrinth structure according to the present disclosure.

[0052] As in Fig. 3 and Fig. As shown in Figure 5, the outer labyrinth structure 90 – just as the inner labyrinth structure 80 described above is formed by the first water stop wall 82 and the second water stop wall 84 – is formed by a third water stop wall 92 and a fourth water stop wall 94, which are arranged in a ring shape along the circumferential direction of the motor shaft 12. The third water stop wall 92 and the fourth water stop wall 94 are located on the radial outer side of the first water stop wall 82 and the second water stop wall 84.

[0053] The third water stop wall 92 extends from the annular insulating section 56 formed on one of the pair of insulators 42 along the axial direction of the motor shaft 12 towards the main body section 62. On the other hand, the fourth water stop wall 94 extends from the main body section 62 along the axial direction of the motor shaft 12 towards the annular insulating section 56.

[0054] The third water stop wall 92 is arranged on the radial outside of the fourth water stop wall 94, and the leading end face of the third water stop wall 92 and the leading end face of the fourth water stop wall 94 overlap in the axial direction of the motor shaft 12. It is ensured that a gap runs between the third water stop wall 92 and the fourth water stop wall 94 along the radial direction.

[0055] The leading end section of the third water stop wall 92 is located opposite the main body section 62 along the axial direction of the motor shaft 12. The leading end section of the fourth water stop wall 94 is located opposite the annular insulating section 56 along the axial direction of the motor shaft 12. Gaps are ensured between the leading end section of the third water stop wall 92 and the main body section 62, as well as between the leading end section of the fourth water stop wall 94 and the annular insulating section 56.

[0056] As in Fig. As shown in Figure 1, the outer labyrinth structure 90 formed by the third water stop wall 92 and the fourth water stop wall 94 is arranged on the radial inside of the plurality of winding coil sections 60 and on the radial outside of the inner labyrinth structure 80.

[0057] The following explains the functioning of the exemplary embodiment according to the present disclosure.

[0058] As described in detail above, the inner labyrinth structure 80 of the brushless motor 10 of the exemplary embodiment according to the present disclosure is formed by the first water stop wall 82 and the second water stop wall 84, which are arranged in a ring shape along the circumferential direction of the motor shaft 12. In the inner labyrinth structure 80, the first water stop wall 82 extends along the axial direction of the motor shaft 12 from the annular insulating section 56 towards the main body section 62, and the second water stop wall 84 extends along the axial direction of the motor shaft 12 from the main body section 62 towards the annular insulating section 56.

[0059] Therefore, even in a case where, for example, a water droplet L has penetrated through the gap between a circumferential edge section of the rotor housing 26 and the main body section 62 of the center piece 18, and which approaches the shaft bearing side 28 between the stator core 40 and the main body section 62, the penetration of the water droplet by the internal labyrinth structure 80 described above can be prevented. Consequently, the shaft bearings 38 can be prevented from being exposed to water.

[0060] Furthermore, the inner labyrinth structure 80 is formed on the radial inner side of the plurality of winding coil sections 60, which are arranged in a ring shape. Since the inner labyrinth structure 80 is not located in the flow path of the cooling air W, which cools the winding coil sections 60 and is expelled towards the radial outer side of the brushless motor 10, it cannot obstruct the flow of the cooling air W.

[0061] In this way, in the brushless motor 10 according to the exemplary embodiment of the present disclosure, the cooling of the winding coil sections 60 is ensured and at the same time the shaft bearings 38 are prevented from being exposed to water.

[0062] Furthermore, because the first water stop wall 82 is arranged on the radial inner side of the second water stop wall 84, it is located closer to the outer peripheral side of the motor shaft 12 (the outer peripheral side of the motor shaft 12 along which the water droplet L flows), which can serve as a path by which the water droplet L penetrates the pair of shaft bearings 38. Consequently, the first water stop wall 82 can even more effectively prevent the shaft bearings 38 from being exposed to water.

[0063] Furthermore, since the extension section 86 formed on the annular insulating section 56 and the leading end section of the second water-stop wall 84 are opposite each other along the axial direction of the motor shaft 12 in the internal labyrinth structure 80 described above, it is possible to prevent the water droplet L from entering between the extension section 86 and the leading end section of the second water-stop wall 84. The water-stopping capability of the internal labyrinth structure 80 can thus be improved.

[0064] As in Fig. As shown in Figure 4, a radially outer end section 86A of the extension section 86 projects further towards the radial outer side of the extension section 86 than the leading end section of the second water-stop wall 84. Since the flow of the water droplet L can be more effectively impeded at the section of the extension section 86 that projects further towards the radial outer side than the second water-stop wall 84, this also improves the water-stopping capability of the inner labyrinth structure 80.

[0065] As in Fig. As shown in Figure 1, in addition to the inner labyrinth structure 80, an outer labyrinth structure 90 is provided on the radial inner side of the plurality of winding coil sections 60. This two-layer labyrinth structure allows for even more effective prevention of water exposure to the shaft bearings 38.

[0066] Like the inner labyrinth structure 80 described above, the outer labyrinth structure 90 is also formed on the radial inner side of the plurality of winding coil sections 60, which are arranged in a ring shape. Since the outer labyrinth structure 90 is not located in the flow path of the cooling air W, which cools the winding coil sections 60 and is expelled towards the radial outer side of the brushless motor 10, it cannot obstruct the flow of the cooling air W.

[0067] As in Fig. As shown in Figure 4, the leading end face of the first water stop wall 82 overlaps with the leading end face of the second water stop wall 84 along the axial direction of the motor shaft 12. The water stopping capability of the inner labyrinth structure 80 can thus be further improved, since the flow path within the inner labyrinth structure 80 is curved and the length of the flow path is greater.

[0068] Similarly, the leading end face of the third water stop wall 92 overlaps, as in Fig. Figure 5 shows the flow path along the axial direction of the motor shaft 12 with the leading end face of the fourth water stop wall 94. The water stop capability of the outer labyrinth structure 90 can thus be further improved, since the flow path within the outer labyrinth structure 90 is curved and the length of the flow path is greater.

[0069] The following is a modified example of the exemplary design of the present disclosure.

[0070] Although the brushless motor 10 of the exemplary embodiment described above in the present disclosure is preferably used as a vehicle blower motor, it can also be used for other applications.

[0071] Although the brushless motor 10 preferably includes the outer labyrinth structure 90 in addition to the inner labyrinth structure 80, the outer labyrinth structure 90 can be omitted.

[0072] Although the first water stop wall 82 is preferably formed on the radial inside of the second water stop wall 84 in the inner labyrinth structure 80, it can also be formed on the radial outside of the second water stop wall 84.

[0073] Although the third water stop wall 92 is formed on the radial outside of the fourth water stop wall 94 in the outer labyrinth structure 90, it can also be formed on the radial inside of the fourth water stop wall 94.

[0074] Although the explanation relates to the exemplary embodiment of the present disclosure described above, the present disclosure is not limited to the above description, and it is evident that various modifications can be made without this deviating from the scope of the disclosure.

Claims

[1] A brushless motor (10) comprising the following: a motor shaft (12); a rotor housing (26) with a circular (cylindrical) shaft bearing housing section (30) provided on the radial outside of the motor shaft (12) and an outer cylindrical section (32) formed on the radial outside of the shaft bearing housing section (30); a shaft bearing (38) which is housed in the shaft bearing housing section (30) and attached to the motor shaft (12); a stator core (40) housed inside the outer cylinder section (32), comprising an annular unit (48) provided on the radial outside of the shaft bearing housing section (30) and a plurality of teeth (50) formed in a radial pattern on the periphery of the annular unit (48); an insulator (42) comprising an annular insulating section (56) covering the annular unit (48) and a plurality of tooth insulating sections (58), each covering the plurality of teeth (50); a plurality of winding coil sections (60) wound around the teeth (50) and over the tooth insulating sections (58); a central section (18) comprising a main body section (62) which is arranged opposite an opening of the outer cylinder section (32) and which supports the motor shaft (12) and the stator core (40); a first water stop wall (82) which is formed in a ring shape along the circumferential direction of the motor shaft (12) and extends along an axial direction of the motor shaft (12) from the annular insulating section (56) in the direction of the main body section (62); and a second water stop wall (84) which is formed in a ring shape along the circumferential direction of the motor shaft (12) and extends along the axial direction of the motor shaft (12) from the main body section (62) in the direction of the annular insulating section (56) and which together with the first water stop wall (82) forms a labyrinth structure arranged on a radial inside of the plurality of winding coil sections (60). [2] Brushless motor (10) according to claim 1, wherein the first water stop wall (82) is arranged on a radial inside of the second water stop wall (84). [3] Brushless motor (10) according to claim 2, wherein: an extension section (86) is formed on the annular insulating section (56), which extends in the direction of a radial outer side of the first water stop wall (82); and a leading end section of the second water stop wall (84) is opposite the extension section (86) along the axial direction of the motor shaft (12). [4] Brushless motor (10) according to claim 3, wherein a radially outer end section of the extension section (86) projects further in the direction of a radial outer side of the extension section (86) than the leading end section of the second water stop wall (84). [5] Brushless motor (10) according to any one of claims 1 to 4, further comprising: a third water stop wall (92) which is formed in a ring shape along the circumferential direction of the motor shaft (12) and extends along the axial direction of the motor shaft (12) from the annular insulating section (56) towards the main body section (62); and a fourth water stop wall (94) which is formed in a ring shape along the circumferential direction of the motor shaft (12) and extends along the axial direction of the motor shaft (12) from the main body section (62) in the direction of the annular insulating section (56), wherein: the first water stop wall (82) and the second water stop wall (84) form an internal labyrinth structure (80) as a labyrinth structure and the third water stop wall (92) and the fourth water stop wall (94) form an outer labyrinth structure (90) which is arranged on the radial inside of the plurality of winding coil sections (60) and on a radial outside of the inner labyrinth structure (80). [6] Brushless motor (10) according to claim 5, wherein: the leading end face of the first water stop wall (82) overlaps with the leading end face of the second water stop wall (84) along the axial direction of the motor shaft (12); and the leading end face of the third water stop wall (82) overlaps with the leading end face of the fourth water stop wall (94) along the axial direction of the motor shaft (12).

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