Outer rotor motor

Abstract

The application relates to an outer rotor motor, which comprises a stator assembly, a rotor assembly, a motor shaft and a fan, the stator assembly comprises a plurality of stacked core punching sheets and windings arranged on the core punching sheets, the rotor assembly comprises a rotor base shell connected to the motor shaft and a plurality of air holes arranged on the rotor base shell, and the fan comprises a base plate and a plurality of fan blades mounted on the base plate; the inner diameter R2 of the core punching sheet, the outermost radius R3 of the winding in the radial direction, the innermost radius R4 of the winding in the radial direction, the inner diameter R6 of the circle where the fan blade is located, the inner diameter R7 of the circle where the fan blade is located, the outermost distance R8 of the air hole in the radial direction and the innermost distance R9 of the air hole in the radial direction satisfy the following relationships: R2+(R3-R4) / 4<=R8<= (R3+R4) / 2, 0.25R2<=R9<=0.5R2, R9<=R7<= (R8+R9) / 2<=R6<=R8. The outer rotor motor has lower winding temperature, better motor heat dissipation performance and higher efficiency under the condition of consuming smaller fan power.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to an external rotor motor. Background Technology

[0002] DC motors, as small and highly efficient motors, are increasingly widely used in various fields and are favored by major industries. With the continuous development of motor technology, DC motors on the market can currently be mainly divided into external rotor motors and internal rotor motors. In the power tool industry, internal rotor motors are the most commonly used. However, to achieve higher motor efficiency, speed, and torque in power tools using internal rotor motors, the motor size needs to be increased. This results in a larger motor design, hindering the miniaturization, high-speed, and high-torque development of power tools. Therefore, compact and high-performance external rotor motors have found wider application in the power tool industry.

[0003] External rotor motors generate heat during operation, causing the motor temperature to rise. The rotation of the fan produces airflow to cool the motor. However, the fan is also a load on the motor. On the one hand, the fan's rotational power has a significant impact on the motor's efficiency. On the other hand, the amount of airflow generated by the fan and the airflow path inside the motor directly affect the temperature rise of the motor windings, and indirectly affect the motor's output power, efficiency, and overload capacity.

[0004] External rotor motor fans are generally of two types: centrifugal and axial. Centrifugal fans can generate high air pressure, which can easily overcome the internal flow resistance of the machine and also facilitate the design of the overall heat dissipation airflow path. When a centrifugal fan rotates at high speed, there is a concept of positive and negative pressure (high and low pressure) zones. The airflow must be drawn in from the negative pressure (low pressure) zone and thrown out by centrifugal force in the positive pressure (high pressure) zone.

[0005] Furthermore, the special structure of the external rotor motor requires pre-drilled ventilation holes for heat dissipation on the iron shell that holds the magnets. A centrifugal fan that rotates with the magnets and the iron shell is then installed outside the holes, thus forming a complete heat dissipation system to cool the motor coils. Therefore, the ventilation holes must be well-designed to ensure smooth airflow while maintaining the strength of the iron shell during high-speed rotation; it is a trade-off.

[0006] Furthermore, enameled wire, wound on an iron core with a specific diameter and number of turns, forms the stator of the external rotor motor. The airflow channel between the stator coils has an inverted "△" shape in cross-section, resulting in different cooling airflow velocities at the bottom and top of a single winding in the radial direction. When using a centrifugal fan for cooling, the airflow enters the motor from the end facing away from the fan. Under the negative pressure generated by the fan's centrifugal force, it flows axially through the inverted triangular area between the two coils, then through the rotor housing ventilation holes before being ejected by the fan. Consequently, the area and shape of the airflow channels along the airflow path differ significantly, and the coils have a windward and leeward side relative to the airflow direction in the axial direction.

[0007] Existing external rotor motors, with their metal casing ventilation holes and fans not designed specifically for the inverted triangle area, may meet the cooling requirements of the windings, but they also cause problems such as uneven cooling of the winding body, low fan efficiency under similar conditions, and high power consumption.

[0008] Therefore, it is indeed necessary to provide an improved external rotor motor to overcome the shortcomings of the existing technology. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide an external rotor motor with good heat dissipation and high efficiency.

[0010] The present invention solves the problems of the prior art by adopting the following technical solution: an external rotor motor, comprising a stator assembly, a rotor assembly sleeved on the outside of the stator assembly, a motor shaft fixed to the rotor assembly, and a fan mounted on the motor shaft. The stator assembly comprises a plurality of stacked iron core laminations and windings wound around the iron core laminations. The rotor assembly comprises a rotor base shell connected to the motor shaft and a plurality of air holes formed in the rotor base shell. The fan comprises a base plate and a plurality of fan blades mounted on the base plate. The inner diameter R2 of the core lamination, the outermost radial radius R3 of the winding, the innermost radial radius R4 of the winding, the inner diameter R6 of the circle containing the fan blade, the inner diameter R7 of the circle containing the fan blade, the outermost radial distance R8 of the air hole, and the innermost radial distance R9 of the air hole satisfy the following relationships: R2+(R3-R4) / 4≤R8≤(R3+R4) / 2, 0.25R2≤R9≤0.5R2, R9≤R7≤(R8+R9) / 2≤R6≤R8.

[0011] A further improvement is that the fan blade is provided with a guide portion on the inner side of the substrate, so that the inner diameter R6 of the circle where the fan blade is located is not equal to the inner diameter R7 of the circle where the fan blade is located.

[0012] A further improvement is that the span angle α of each of the air holes in the circumferential direction satisfies the following relationship: 60°≤α≤120°.

[0013] A further improvement is that each of the air vents exposes at least three of the windings.

[0014] A further improvement is to ensure that the air vent exposes at least an integer number of fan blades corresponding to the value of 360° / α, with any number less than one counted as one.

[0015] A further improvement is as follows: the number of slots Z1 of the iron core lamination, the number of fan blades Z2, and the number of air holes Z3 satisfy the following relationship: Z1≤Z2≤Z1+Z3.

[0016] A further improvement is as follows: the rotor assembly includes a mounting hole that penetrates the middle of the rotor base shell, and a plurality of air holes are spaced apart on the outer periphery of the mounting hole.

[0017] A further improvement is as follows: the air vent includes a first section close to the mounting hole and a second section away from the mounting hole, and the first section and the second section are arranged in an arc shape.

[0018] A further improvement is that all the guide sections are located between the first segment and the second segment.

[0019] A further improvement is as follows: the outer diameter R1 of the core lamination satisfies the following relationship: R3-R4≤R1-R2.

[0020] Compared with the prior art, the present invention has the following advantages: the winding temperature is lower while consuming less fan power, and the motor has better heat dissipation performance and higher efficiency. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the external rotor motor of the present invention; Figure 2 yes Figure 1 A cross-sectional view of the external rotor motor shown. Figure 3 This is a schematic diagram of the stator assembly in the external rotor motor of the present invention; Figure 4 This is a schematic diagram of the rotor assembly in the external rotor motor of the present invention; Figure 5 yes Figure 4 A schematic diagram of the rotor assembly from another angle is shown; Figure 6 This is a schematic diagram of the fan structure in the external rotor motor of the present invention; Figure 7 This is a schematic diagram of the engagement of the stator assembly and the rotor assembly in the external rotor motor of the present invention; Figure 8 This is a schematic diagram of the cooperation between the rotor assembly and the fan in the external rotor motor of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0023] The terminology used in this invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. For example, terms such as "upper," "lower," "front," "rear," "left," and "right" that indicate orientation or positional relationship are based solely on the orientation or positional relationship shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device / element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0024] Please see Figure 1 and Figure 2 As shown, an embodiment of the present invention relates to an external rotor motor 100, which includes a stator assembly 1, a rotor assembly 2 sleeved on the outside of the stator assembly 1, a motor shaft 3 fixed to the rotor assembly 2, and a fan 4 mounted on the motor shaft 3. The motor shaft 3 extends through the stator assembly 1, the rotor assembly 2, and the fan 4. The fan 4 is mounted on the end of the motor shaft 3 near the rotor assembly 2. When the motor shaft 3 rotates, it drives the fan 4 to rotate and form an airflow. The airflow flows through the stator assembly 1 and the rotor assembly 2 to cool and dissipate heat from the stator assembly 1 and the rotor assembly 2.

[0025] Please see Figure 3 As shown, the stator assembly 1 includes a plurality of stacked core laminations 11 and windings 12 wound around the core laminations 11. The core laminations 11 include a sleeve 111 and a plurality of stator teeth 112 protruding radially outward from the outer periphery of the sleeve 111. The plurality of stator teeth 112 are arranged at intervals along the circumference of the sleeve 111. The windings 12 also have a plurality of windings and are wound around the plurality of stator teeth 112 respectively.

[0026] In this embodiment, a slot 13 is formed between two adjacent windings 12, and the slot 13 is in the shape of an inverted triangle, through which the airflow generated by the fan 4 flows.

[0027] Please see Figure 4 and Figure 5 As shown, the rotor assembly 2 includes a rotor base shell 21 connected to the motor shaft 3, a mounting hole 22 penetrating the middle of the rotor base shell 21, a plurality of air holes 23 opened in the rotor base shell 21, a magnet frame 24 connected to the rotor base shell 21, and magnets 25 installed on the magnet frame 24. The magnet frame 24 is located between the rotor base shell 21 and the stator assembly 1. The magnets 25 are fixedly installed on the magnet frame 24 by glue, and the magnet frame 24 and the magnets 25 are attached to the inner wall of the rotor base shell 21.

[0028] In this embodiment, multiple air holes 23 are spaced apart on the outer periphery of the mounting hole 22.

[0029] In this embodiment, the air vent 23 is provided between the stator assembly 1 and the fan 4 so that the airflow generated by the rotation of the fan 4 flows through the interior of the rotor assembly 2 and effectively cools the area where the stator assembly 1 is located.

[0030] Furthermore, the airflow generated by the rotation of the aforementioned fan 4 cools the winding 12.

[0031] In this embodiment, the motor shaft 3 passes through the mounting hole 22, and the rotor assembly 2 is fixed to the motor shaft 3 via the mounting hole 22.

[0032] Please see Figure 6 As shown, the fan 4 includes a circular base plate 41 and a plurality of fan blades 42 mounted on the base plate 41. The plurality of fan blades 42 extend approximately along the radial direction of the base plate 41 and are distributed at intervals along the circumference of the base plate 41.

[0033] In this embodiment, the fan blade 42 is provided with a guide portion 421 on the inner side of the substrate 41. The guide portion 421 is rounded or beveled so that airflows of different speeds can enter the fan 4 with lower impact loss, thereby improving working efficiency.

[0034] In this embodiment, the fan 4 is a centrifugal fan.

[0035] In this embodiment, the fan 4 is a backward-curved centrifugal fan, a radial centrifugal fan, or a forward-curved centrifugal fan.

[0036] Please see Figure 3 As shown, stator assembly 1 is defined as follows: R1: Outer diameter of iron core lamination 11; R2: Inner diameter of core lamination 11; R3: The outermost radial radius of winding 12; R4: The innermost radial radius of winding 12; H: Maximum radial height of winding 12 (H=R3-R4). Z1: The number of slots 13 (the outer rotor of power tools is generally 12 slots).

[0037] Please see Figure 6 As shown, fan 4 is defined as follows: R5: Outer diameter of the circle containing blade 42; R6: Inner diameter of the circle containing blade 42; R7: Inner diameter of the circle containing blade 42; Z2: Number of blades 42.

[0038] Please see Figure 5As shown, rotor assembly 2 is defined as follows: R8: Radial outermost distance (usually an arc) of the air vent 23; R9: The radial innermost distance (usually an arc) of the air vent 23; α: The span angle of a single air vent 23 in the circumferential direction; S1: Area of ​​a single air vent 23; Z3: Number of air vents 23.

[0039] Please combine Figure 7 As shown, in order to ensure that the airflow in the inverted triangular groove 13 can smoothly cool the winding 12 on the leeward side, instead of flowing out directly from the outermost side of the air hole 23, and at the same time ensure that the air hole 23 has sufficient ventilation area, R1, R2, R3, R4, R8, R9, α and S1 have the following constraint relationship: ①R3-R4≤R1-R2; ②R2+(R3-R4) / 4≤R8≤(R3+R4) / 2; ③0.25R²≤R⁹≤0.5R².

[0040] Furthermore, 60°≤α≤120° (this range corresponds to the number of air holes 23, 3≤Z3≤6), preferably the larger α is, that is, each air hole 23 exposes at least three windings 12 on the leeward side, and the corresponding S1 is also large, which is more conducive to the airflow out of the interior of the outer rotor motor 100.

[0041] Please combine Figure 8 As shown, to ensure that the main dimensions of the air vent 23 do not disrupt the high and low pressure zones generated by the fan 4 during high-speed rotation, and that the airflow cooling the winding 12 can be smoothly ejected from the air vent 23 by the fan, R5, R6, R7, R8, and R9 have the following constraint relationships: ①R9≤R7≤(R8+R9) / 2; ② (R8+R9) / 2≤R6≤R8.

[0042] Preferably, R6≠R7, that is, the fan blade 42 has a guide portion 421 on the inner side of the substrate 41.

[0043] Please see Figures 3 to 6 As shown, Z1, Z2, and Z3 have the following constraint relationships: ①Z1≤Z2≤Z1+Z3.

[0044] Preferably, the above-mentioned air vent 23 exposes at least an integer number of air blades 42 corresponding to the value of 360° / α, and if less than one, it is counted as one.

[0045] In this embodiment, the above-mentioned air hole 23 includes a first segment 231 close to the mounting hole 22 and a second segment 232 away from the mounting hole 22, and the first segment 231 and the second segment 232 are arranged in an arc shape.

[0046] Please see Figure 8 As shown, furthermore, all of the aforementioned guide sections 421 are located between the first section 231 and the second section 232 to achieve better cooling efficiency.

[0047] Compared to conventional industry designs, the three-hole scheme of this invention, although with a smaller ventilation area, allows for better airflow cooling of the leeward winding 12 by controlling the relationships between R1-R9 and Z1-Z3, preventing direct exhaust from the outside of the vent 23. Furthermore, the matching design of the vent 23, fan 4, and motor body achieves a fan power consumption reduction of over 10% and a winding temperature rise reduction of over 5K. This significantly improves motor efficiency and heat dissipation economy, while also reducing the no-load current of power tools using external rotor motors, thereby increasing the overall machine's runtime.

[0048] The three-hole scheme described above as an example of dimensional illustration is for ease of description. Any design changes based on this scheme are considered as other embodiments of the present invention. The present invention focuses on illustrating the mathematical relationship between R1-R9 and Z1-Z3.

[0049] This invention redesigns the parameters of relevant components in the external rotor motor 100, resulting in lower winding temperature, better motor heat dissipation, and higher efficiency while consuming less fan power. Compared to conventional designs in the industry, the external rotor motor 100 designed using this invention significantly reduces fan power consumption by more than 10% and reduces winding temperature rise by more than 5K.

[0050] This invention is not limited to the specific embodiments described above. Those skilled in the art will readily understand that many other alternatives to the external rotor motor of this invention can be found without departing from the principles and scope of the invention. The scope of protection of this invention is defined by the claims.

Claims

1. An external rotor motor (100) comprising a stator assembly (1), a rotor assembly (2) sleeved on the outside of the stator assembly (1), a motor shaft (3) fixed to the rotor assembly (2), and a fan (4) mounted on the motor shaft (3), wherein the stator assembly (1) comprises a plurality of stacked iron core laminations (11) and windings (12) wound around the iron core laminations (11), the rotor assembly (2) comprises a rotor base shell (21) connected to the motor shaft (3) and a plurality of air holes (23) opened in the rotor base shell (21), and the fan (4) comprises a base plate (41) and a plurality of fan blades (42) mounted on the base plate (41); characterized in that: The inner diameter R2 of the core lamination (11), the outermost radial radius R3 of the winding (12), the innermost radial radius R4 of the winding (12), the inner diameter R6 of the circle where the fan blade (42) is located, the inner diameter R7 of the circle where the fan blade (42) is located, the outermost radial distance R8 of the wind hole (23), and the innermost radial distance R9 of the wind hole (23) satisfy the following relationship: R2+(R3-R4) / 4≤R8≤(R3+R4) / 2, 0.25R2≤R9≤0.5R2, R9≤R7≤(R8+R9) / 2≤R6≤R8.

2. The external rotor motor (100) according to claim 1, characterized in that: The fan blade (42) has a guide portion (421) on the inner side of the substrate (41), such that the inner diameter R6 of the circle where the fan blade (42) is located is not equal to the inner diameter R7 of the circle where the fan blade (42) is located.

3. The external rotor motor (100) according to claim 1, characterized in that: The span angle α of each of the vents (23) in the circumferential direction satisfies the following relationship: 60°≤α≤120°.

4. The external rotor motor (100) according to claim 3, characterized in that: Each of the vents (23) exposes at least three of the windings (12).

5. The external rotor motor (100) according to claim 3, characterized in that: The air vent (23) exposes at least an integer number of air blades (42) corresponding to the value of 360° / α, and if less than one, it is counted as one.

6. The external rotor motor (100) according to claim 1, characterized in that: The number of slots Z1 of the core lamination (11), the number of fan blades (42) Z2, and the number of air holes (23) Z3 satisfy the following relationship: Z1≤Z2≤Z1+Z3.

7. The external rotor motor (100) according to claim 2, characterized in that: The rotor assembly (2) includes a mounting hole (22) penetrating the middle of the rotor base shell (21), and a plurality of air holes (23) are spaced apart on the outer periphery of the mounting hole (22).

8. The external rotor motor (100) according to claim 7, characterized in that: The air vent (23) includes a first segment (231) near the mounting hole (22) and a second segment (232) away from the mounting hole (22), and the first segment (231) and the second segment (232) are arranged in an arc shape.

9. The external rotor motor (100) according to claim 8, characterized in that: The guide section (421) is located entirely between the first segment (231) and the second segment (232).

10. The external rotor motor (100) according to claim 1, characterized in that: The outer diameter R1 of the core lamination (11) satisfies the following relationship: R3-R4≤R1-R2.

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