Brushless Outer Rotor Motor

Abstract

A brushless outer rotor motor comprises an inner stator and an outer rotor, wherein the inner stator comprises a stator core, and the outer rotor comprises an axially extending rotating shaft and a housing fixed on the rotating shaft. The housing comprises an outer circular side wall and an end wall located at one end of the outer circular side wall, wherein the outer circular side wall and the end wall are provided with a receiving cavity, wherein the stator core is radially located between the rotating shaft and the outer circular side wall, and the outer rotor comprises a retaining frame integrally formed and fixed on the housing, wherein the retaining frame is received in the receiving cavity and is provided with a plurality of fan blades protruding into the receiving cavity. The fan blades are evenly distributed along the circumference to form a fan, and the fan is adjacent to the stator core, so that the heat dissipation effect of the brushless outer rotor motor is good and the motor performance can be more fully exerted; meanwhile, the retaining frame has a magnetic pole slot for accommodating magnetic poles to fix and support the magnetic poles, thereby improving the fixing accuracy of the magnetic poles.

Description

[Technical field]

[0001] The invention relates to a brushless outer rotor motor, in particular to a brushless outer rotor motor with good heat dissipation effect. [Background Technology]

[0002] Brushless outer rotor motors are widely used in various fields due to their high power density and small size. For example, electric chain saws, hair dryers, and lawn mowers are also among the devices currently using brushless outer rotor motors. The brushless outer rotor motors in electric chain saws, hair dryers, and lawn mowers include an inner stator and an outer rotor. The inner stator is installed in the housing and has a stator winding. The main body of the outer rotor surrounds the outer periphery of the inner stator and has magnetic poles. However, the heat dissipation of the brushless outer rotor motor is usually achieved by designing a fan structure on the cast aluminum structure, which makes the overall size of the motor large, the process complex, and the cost high.

[0003] China Utility Model Patent Publication No. CN209217852U discloses a direct-drive motor, which includes a stator and a rotor, and the rotor has an integrally formed casing, and the casing has a bottom wall and a peripheral wall connected to the bottom wall. Ventilation holes are provided on the bottom wall of the casing to form a fan, and the fan structure solves the problem of large overall size and high cost of the motor to a certain extent. However, the fan is stamped from the bottom wall of the casing, so that the blades of the fan cannot be made into a complex structure due to the limitation of the bottom wall, and the height and number of the blades cannot be effectively designed; and when the size of the motor increases to a certain size, the thickness of the casing will also increase to a certain value. At this time, it will be more difficult to stamp the fan on the bottom wall of the casing, so the use of the fan structure has great limitations and does not have wide applicability.

[0004] In view of this, it is indeed necessary to provide an improved brushless outer rotor motor to overcome the defects of the prior art. [Summary of the invention]

[0005] In view of the deficiencies in the prior art, an object of the present invention is to provide a brushless outer rotor motor with good heat dissipation effect, which reduces its cost while ensuring its performance.

[0006] The technical solution adopted by the present invention to solve the existing technical problems is: a brushless outer rotor motor, including an inner stator and an outer rotor, the inner stator including a stator core, the outer rotor including an axially extending rotating shaft and a housing fixed on the rotating shaft. The housing includes an outer circular side wall and an end wall located at one end of the outer circular side wall, the outer circular side wall and the end wall are surrounded by a receiving cavity, the stator core is located between the rotating shaft and the outer circular side wall in the radial direction, the outer rotor includes a retaining frame integrally formed and fixed on the housing, the retaining frame is received in the receiving cavity, and is provided with a plurality of fan blades protruding into the receiving cavity.

[0007] A further improved solution is: the retaining frame is provided with an outer ring fixed to the inner wall surface of the outer circular side wall, and a plurality of the fan blades extend inwardly from the inner wall surface of the outer ring.

[0008] A further improved solution is: the fan blades are evenly distributed along the circumferential direction to form a fan, the fan is adjacent to the stator core, and the distance from the fan to the inner stator is 2.5 to 5 mm.

[0009] A further improved solution is that the fan blade is located between the stator core and the end wall in the axial direction, and one axial end of the fan blade is adjacent to the stator core, while the other axial end extends to the inner wall surface of the end wall.

[0010] A further improvement is that the retaining frame is not connected to the rotating shaft, and the distance between the fan blade and the rotating shaft is not less than 0.5 mm.

[0011] A further improvement is as follows: the outer rotor includes a plurality of magnetic poles which are attached to the inner wall surface of the outer circular side wall and are evenly distributed along the circumferential direction; the retaining frame is axially located between the magnetic pole and the end wall; and the retaining frame is provided with a magnetic pole slot which is recessed from one end of the outer ring adjacent to the magnetic pole; the magnetic pole slot is arranged corresponding to the magnetic pole and at least partially accommodates the magnetic pole to fix the magnetic pole.

[0012] A further improved solution is: the housing is provided with an inner edge portion protruding from the end of the end wall toward the inner stator, and the retaining frame is arranged between the inner edge portion and the outer circular side wall.

[0013] A further improved solution is: the retaining frame is provided with an inner ring, the fan blades are connected to the inner ring, and the inner ring is located between the inner edge portion and the outer circular side wall.

[0014] A further improvement is as follows: the housing includes an axial hole located in the center of the end wall, the inner edge portion extends axially from the inner side of the axial hole, the rotating shaft passes through the axial hole and cooperates with the inner edge portion to fix the housing to the rotating shaft.

[0015] A further improvement is that the outer rotor further comprises a balancing ring fixed on the rotating shaft, the balancing ring abuts against the outer wall surface of the end wall of the housing, and the balancing ring and the retaining frame are respectively located at two axial ends of the end wall.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the housing includes an outer circular side wall and an end wall located at one end of the outer circular side wall, the outer circular side wall and the end wall are surrounded by a receiving cavity, the outer rotor includes a retaining frame integrally formed and fixed on the housing, the retaining frame is received in the receiving cavity and is provided with a plurality of fan blades protruding into the receiving cavity. The fan blades are evenly distributed along the circumference to form a fan, and the fan is adjacent to the stator core, so that the heat dissipation effect of the brushless outer rotor motor is good and the motor performance can be more fully exerted; the retaining frame has a magnetic pole slot for accommodating the magnetic pole to fix and support the magnetic pole, thereby improving the fixing accuracy of the magnetic pole. At the same time, the retaining frame is an injection molded part, and the shape, number and height of its blades can be designed in a variety of ways to meet the needs of product diversification; further, the balance ring is arranged on the outside of the housing to facilitate the correction of the motor balance. [Drawings]

[0017] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings:

[0018] Figure 1 1 is a three-dimensional schematic diagram of a brushless outer rotor motor according to a preferred embodiment of the present invention;

[0019] Figure 2 yes Figure 1 A partially exploded view of a brushless outrunner motor is shown;

[0020] Figure 3 yes Figure 1 A cross-sectional view of the brushless outer rotor motor shown along the axial direction;

[0021] Figure 4 yes Figure 2 An exploded schematic diagram of an outer rotor in a brushless outer rotor motor is shown;

[0022] Figure 5 yes Figure 4 A three-dimensional schematic diagram of the retainer in the outer rotor shown;

[0023] Figure 6 yes Figure 5 A front view of the cage shown;

[0024] Figure 7 FIG. 1 is a perspective schematic diagram of a second embodiment of a retaining frame of the present invention.

[0025] Meaning of the reference numerals in the figures:

[0026] 100, brushless outer rotor motor 10, outer rotor 11, shaft 12, housing 120, shaft hole 121, outer circular side wall 122, end wall 123, through hole 124, inner edge 125, receiving cavity 13, retainer 131, outer ring 132, inner ring 133, blade 134, magnetic pole slot 135, channel 14, magnetic pole 15, balance ring 16, retainer 161, outer ring 163, blade 164, magnetic pole slot 20, inner stator [Specific implementation method]

[0027] See also Figures 1 to 6 The brushless outer rotor motor 100 of the present invention is shown, which is applied to an electric tool and has the characteristics of high efficiency and long life. The brushless outer rotor motor 100 includes an outer rotor 10 and an inner stator 20, wherein the outer rotor 10 is covered on the outer side of the inner stator 20 and rotates relative to the inner stator 20.

[0028] See also Figure 2 As shown, the inner stator 20 includes a stator core, that is, a stator punching sheet; preferably, the outer diameter of the stator core is 50 to 95 mm. In this embodiment, the stator core has 12 stator slots, each of which is used to wind a stator coil, and a three-phase winding is formed by winding on the stator slots. Stator teeth exist between the slots of the stator slots to provide magnetic flux density, thereby generating electromagnetic torque. A stator yoke is formed between the stator slots and the inner hole of the stator punching sheet to provide yoke magnetic flux density.

[0029] See also Figure 3 and Figure 4 As shown, the outer rotor 10 includes an axially extending rotating shaft 11, a housing 12 fixed on the rotating shaft 11, and a retaining frame 13 and a plurality of magnetic poles 14 fixed in the housing 12. The housing 12 is an integrally formed metal part and includes an outer circular side wall 121 and a circular end wall 122 located at one end of the outer circular side wall 121. The outer circular side wall 121 and the end wall 122 are surrounded by a receiving cavity 125. The stator core is located between the rotating shaft 11 and the outer circular side wall 121 in the radial direction. The housing 12 includes an axial hole 120 located at the center of the end wall 122 and an inner edge portion 124 extending axially from the inner side of the axial hole 120. The inner edge portion 124 is formed by protruding from the end of the end wall 122 toward the inner stator 20. The rotating shaft 11 passes through the shaft hole 120 and cooperates with the inner edge portion 124 to fix the housing 12 to the rotating shaft 11 . At this time, the rotating shaft 11 drives the housing 12 to rotate together.

[0030] Combination Figure 5As shown, the retainer 13 is an integrally formed injection molded part and is received in the receiving cavity 125. The retainer 13 includes an outer ring 131 fixed to the inner wall surface of the outer circular side wall 121, an inner ring 132 located between the inner edge portion 124 and the outer circular side wall 121, and a plurality of blades 133 located between the outer ring 131 and the inner ring 132. The blades 133 extend inwardly from the inner wall surface of the outer ring 131, and the blades 133 are connected and fixed to the inner ring 132 on the side away from the outer ring 131. The retainer 13 is disposed between the inner edge portion 124 and the outer circular side wall 121, and the retainer 13 is not connected to the rotating shaft 11. The spacing between the blades 133 and the rotating shaft 11 is not less than 0.5 mm, so as to avoid interference between the blades 133 and the rotating shaft 11. At the same time, the fan blades 133 protrude into the receiving cavity 125 and are evenly distributed along the circumference to form a fan, and the fan is adjacent to the stator core of the inner stator 20, so that the heat dissipation effect of the brushless outer rotor motor 100 is good and the motor performance can be more fully exerted.

[0031] Since the retainer 13 is an injection molded part with a density of about 1.0 to 1.4 g / cm^3, it is light in weight compared to the die-cast aluminum parts in the traditional design. The outer rotor 10 will reduce the starting current due to its small moment of inertia when working, thereby improving the response speed of the switch. At the same time, for working conditions with braking requirements, the braking current in the circuit can be reduced, thereby improving the braking life of the brushless outer rotor motor 100; and the heat resistance selection of the motor's insulation material and the temperature resistance level of the enameled wire can be appropriately reduced.

[0032] The number of the fan blades 133 of the retaining frame 13 can be flexibly selected according to different product requirements and the spatial structure inside the outer rotor. In this embodiment, the number of the fan blades is 15; the shape of the fan blades 133 can also be designed in a variety of ways to meet the needs of the product, for example: the fan blades 133 can extend toward the axis of the rotating shaft 11 and be set obliquely to form an axial flow fan, and the deflection angle of the fan blades is 10 degrees to further increase the air volume of the brushless outer rotor motor 100. Compared with the molded fan structure on the casing in the traditional design, the fan design of the retaining frame 13 of the present invention has a wide range of applicability; especially when the outer diameter of the brushless outer rotor motor 100 is 60 to 110 mm and it is a low-speed brushless outer rotor motor, there is a significant improvement.

[0033] In this embodiment, the fan blade 133 is located between the stator core and the end wall 122 in the axial direction, and one axial end of the fan blade 133 is adjacent to the stator core, while the other axial end extends to the inner wall surface of the end wall 122. The end wall 122 is provided with a number of through holes 123 evenly distributed along the circumferential direction, and a channel 135 is formed between the fan blades 133 of the retaining frame 13. The through holes 123 are connected with the channel 133 to form an air duct. When the outer rotor 10 is working, it is ensured that the airflow formed by the fan flows through the outer rotor 10 to blow toward the stator core of the inner stator 20. At the same time, the distance from the fan to the inner stator 20 is 2.5 to 5 mm, and at this time, the brushless outer rotor motor 100 achieves the best heat dissipation effect. In practical applications, the end wall 122 of the housing 12 can be stamped into through holes 123 of different shapes and numbers according to needs. In this embodiment, the number of through holes 123 is 4.

[0034] Combination Figure 6 As shown, the magnetic pole 14 is attached to the inner wall surface of the outer circular side wall 122 of the housing 12 and is evenly distributed along the circumferential direction. In this embodiment, the number of the magnetic poles 14 is 8, and the magnetic poles 14 are made of aluminum iron boron material. The retaining frame 13 is located between the magnetic pole 14 and the end wall 122 in the axial direction, and the retaining frame 13 is provided with a magnetic pole slot 134 formed by a depression at one end of the outer ring 131 adjacent to the magnetic pole 14. The magnetic pole slot 134 is arranged corresponding to the magnetic pole 14 and at least partially accommodates the magnetic pole 14 to fix and support the magnetic pole 14, thereby ensuring the fixing accuracy of the magnetic pole 14. Therefore, the retaining frame 13 has the function of fixing and supporting the magnetic pole 14 and also has the function of fan heat dissipation.

[0035] The holder 13 of the present invention can be designed with corresponding magnetic pole slots 134 according to the number and shape of the magnetic poles 14, and the magnetic poles 14 can be firmly set on the inner wall surface of the housing 12 through relevant tolerance matching; and because the holder 13 is injection molded, it has high size and position accuracy, so that the magnetic poles 14 can be evenly distributed on the outer cylindrical side wall 121 of the housing 12 as needed, which helps the magnetic poles 14 to provide a uniform magnetic field in a cycle, so that the performance of the motor is guaranteed. At the same time, this can accurately provide the magnetic pole position for a brushless motor using an inductive sensor (such as a Hall sensor), so that the driving energy of the controller can be most effectively output and utilized, thereby improving the speed accuracy of the brushless outer rotor motor 100 and reducing load torque fluctuations.

[0036] At the same time, the brushless outer rotor motor 100 will provide corresponding torque output to drive related components to work during operation. Due to the interaction of forces, the magnetic pole 14 will generate corresponding tangential force along the inner wall surface of the outer circular side wall 121 in the housing 12 of the outer rotor 10. The two sides of the magnetic pole slot 134 of the retaining frame 13 will circumferentially fix the magnetic pole 14 and provide support, which can greatly reduce the requirements on the quality characteristics of the glue for fixing the magnetic pole 14, and the application range of the glue selection is wider; and the height of the two sides of the magnetic pole slot 134 can be designed according to the output power of the motor and the height of the magnetic pole 14.

[0037] The outer rotor 10 further includes a balancing ring 15 fixed on the rotating shaft 11, the balancing ring 15 is close to the outer wall surface of the end wall 122 of the housing 12, and the balancing ring 15 and the retaining frame 13 are respectively located at the axial ends of the end wall 122. The balancing ring 15 is arranged on the outer side of the housing 12 to facilitate the correction of the balance of the motor; at the same time, the balancing ring 15 replaces the design of correcting the balance of the fan of the existing cast aluminum structure by milling, thereby avoiding the disadvantage of reducing the air volume caused by milling the fan.

[0038] In the present invention, the housing 12 includes an outer circular side wall 121 and an end wall 122 located at one end of the outer circular side wall 121, and the outer circular side wall 121 and the end wall 122 are surrounded by a receiving cavity 125. The outer rotor 10 includes a holder 13 integrally formed and fixed on the housing 12, and the holder 13 is received in the receiving cavity 125 and is provided with a plurality of fan blades 133 protruding into the receiving cavity 125. The fan blades 133 are evenly distributed along the circumference to form a fan, and the fan is adjacent to the stator core, so that the heat dissipation effect of the brushless outer rotor motor 100 is good and the motor performance can be more fully exerted; the holder 13 has a magnetic pole slot 134 for accommodating the magnetic pole 14 to fix and support the magnetic pole 14, thereby improving the fixing accuracy of the magnetic pole 14. Meanwhile, the retaining frame 13 is an injection molded part, and the shape, quantity and height of its blades can be designed in a variety of ways to meet the diverse needs of products; further, the balance ring 15 is arranged on the outside of the housing 12 to facilitate the correction of the motor balance.

[0039] See also Figure 7As shown, the second embodiment is different from the first embodiment in that the retaining frame 16 is an integrally formed injection molded part and includes an outer ring 161 fixed to the inner wall surface of the outer circular side wall 121, a fan blade 163 extending inward from the inner wall surface of the outer ring 161, and a magnetic pole slot 164 for accommodating the magnetic pole 14, but does not have the above-mentioned inner ring. The fan blades 163 are evenly distributed along the circumference to form a fan, and the fan is adjacent to the stator core of the inner stator 20, so that the heat dissipation effect of the brushless outer rotor motor 100 is good and the motor performance can be more fully exerted. In this embodiment, the fan blade 163 has sufficient strength so that its free end does not need to be fixed by an inner ring. At the same time, the fan blade 163 does not need to extend toward the axis of the rotating shaft 11 when extending inward, and it is only necessary to generate sufficient airflow to blow toward the inner stator 20 when the outer rotor 10 is working.

[0040] The present invention is not limited to the above specific embodiments. A person skilled in the art can easily understand that there are many alternatives to the brushless outer rotor motor of the present invention without departing from the principle and scope of the present invention. The protection scope of the present invention shall be subject to the content of the claims.

Claims

1. A brushless outer rotor motor, comprising an inner stator and an outer rotor, wherein the inner stator comprises a stator core, and the outer rotor comprises an axially extending rotating shaft and a housing fixed on the rotating shaft; characterized in that: The casing includes an outer circular side wall and an end wall located at one end of the outer circular side wall, the outer circular side wall and the end wall are surrounded by a receiving cavity, the stator core is located between the rotating shaft and the outer circular side wall in the radial direction, the outer rotor includes a retaining frame integrally formed and fixed on the casing and a plurality of magnetic poles fixed in the casing, the retaining frame at least partially accommodates the magnetic poles, the retaining frame is received in the receiving cavity, and is provided with a plurality of fan blades protruding into the receiving cavity.

2. The brushless outer rotor motor according to claim 1, characterized in that: The retaining frame is provided with an outer ring fixed to the inner wall surface of the outer circular side wall, and a plurality of the fan blades extend inwardly from the inner wall surface of the outer ring.

3. The brushless outer rotor motor according to claim 2, characterized in that: The fan blades are evenly distributed along the circumference to form a fan, the fan is adjacent to the stator core, and the distance between the fan and the inner stator is 2.5-5 mm.

4. The brushless outer rotor motor according to claim 3, characterized in that: The fan blade is located between the stator core and the end wall in the axial direction, and one axial end of the fan blade is adjacent to the stator core, while the other axial end extends to the inner wall surface of the end wall.

5. The brushless outer rotor motor according to claim 2, characterized in that: The retaining frame is not connected to the rotating shaft, and the distance between the fan blade and the rotating shaft is not less than 0.5 mm.

6. The brushless outer rotor motor according to claim 2, characterized in that: The outer rotor includes a plurality of magnetic poles that are attached to the inner wall surface of the outer circular side wall and are evenly distributed along the circumferential direction. The retaining frame is axially located between the magnetic pole and the end wall, and the retaining frame is provided with a magnetic pole slot formed by a recess from one end of the outer ring adjacent to the magnetic pole. The magnetic pole slot is arranged corresponding to the magnetic pole and at least partially accommodates the magnetic pole to fix the magnetic pole.

7. The brushless outer rotor motor according to claim 1, characterized in that: The housing is provided with an inner edge portion protruding from the end of the end wall toward the inner stator, and the retaining frame is arranged between the inner edge portion and the outer circular side wall.

8. The brushless outer rotor motor according to claim 7, characterized in that: The retaining frame is provided with an inner ring, the fan blade is connected to the inner ring, and the inner ring is located between the inner edge portion and the outer circular side wall.

9. The brushless outer rotor motor according to claim 7, characterized in that: The housing includes an axial hole located in the center of the end wall, the inner edge portion extends axially from the inner side of the axial hole, and the rotating shaft passes through the axial hole and cooperates with the inner edge portion to fix the housing to the rotating shaft.

10. The brushless outer rotor motor according to claim 1, characterized in that: The outer rotor further comprises a balancing ring fixed on the rotating shaft, the balancing ring is close to the outer wall surface of the end wall of the housing, and the balancing ring and the retaining frame are respectively located at two axial ends of the end wall.

Images