A low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove

Abstract

The present invention discloses a low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove, which includes an inner stator and an outer rotor. The outer rotor is fixed on the inner surface of a rotor housing, and end covers are provided at both ends of the rotor housing. The outer rotor includes a rotor core, and permanent magnets and iron magnetic poles are alternately arranged along the circumferential direction on the inner surface of the rotor core. Oil storage hole grooves are provided on all or part of the iron magnetic poles of the rotor core; a liquid cooling medium is provided in the air gap between the inner stator and the outer rotor. By using the present invention, the problem of difficult heat dissipation of the stator of the existing low-speed outer-rotor permanent magnet motor can be solved. Without affecting the electromagnetic performance of the motor, by changing the rotor structure of the motor, the production process cost can be reduced as much as possible, and the heat dissipation performance of the motor can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and particularly relates to a low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove. Background Art

[0002] In an outer-rotor motor, the heat generated by energy loss is mainly concentrated in the stator core and coil. This heat needs to be transferred to the rotor through the air gap between the stator and rotor, and then dissipated outside the motor. Generally, there is only air in the air gap, and the thermal conductivity of air is low, making it difficult to generate effective conduction heat dissipation; in a low-speed motor, usually the air flow is poor, making it difficult to generate effective convective heat dissipation. Therefore, in a low-speed outer-rotor motor, it is difficult to dissipate the stator heat, which easily causes the stator to overheat and affects the performance and lifespan of the motor. Therefore, the cooling technology for such motors is particularly important.

[0003] Chinese patent document with publication number CN102857027A discloses a closed-loop ventilation system for an outer-rotor fan motor, where the rotor bracket rotates around the motor shaft, driving an internal circulation inside the motor, thereby generating convective heat dissipation and improving the heat dissipation effect. However, the structure of this invention is difficult to form a sufficient circulating wind speed in a low-speed motor, and thus it is difficult to improve heat dissipation; moreover, this structure requires the installation of additional mechanical devices, increasing the installation size and cost of the motor.

[0004] For a low-speed outer-rotor motor, a commonly used method to improve cooling is to fill the motor air gap with cooling oil (or other liquid cooling media, hereinafter collectively referred to as "liquid cooling media"), which can transfer the heat on the stator to the rotor through these liquid cooling media. Since the liquid cooling media will greatly increase the frictional loss and is prone to leakage through the bearing parts at the shaft ends, usually only about one-third of the space in the lower part of the air gap is filled with liquid cooling media. Therefore, only about one-third of the lower part of the stator can have better heat dissipation conditions, while the upper part of about two-thirds still has difficulty in heat dissipation, and it causes a very uneven temperature distribution of the stator.

[0005] To this end, Chinese patent document with publication number CN106972666A proposes an oil-cooled and low-loss outer-rotor permanent magnet motor. Each pole of the rotor of this invention is composed of a permanent magnet (i.e., a full permanent magnet pole structure). Inner corners are cut on both sides of the inner arc surface of the permanent magnet, and then spiral inlet channels are axially opened on the inner surface of the entire cylindrical structure composed of all permanent magnets, and inclined flow-through channels are axially opened on the outer surface of the rotor yoke. This invention improves the heat dissipation ability of the rotor through the liquid cooling media in the inlet channels and inclined flow-through channels. However, the liquid cooling media does not contact the stator and cannot effectively improve the heat dissipation of the stator. Moreover, the permanent magnet structure is complex and the processing technology is cumbersome, greatly increasing the cost. Summary of the Invention

[0006] To solve the problem of difficult stator heat dissipation in low-speed outer-rotor permanent magnet motors existing in the prior art, the present invention provides a low-speed outer-rotor permanent magnet motor with rotor oil storage hole grooves. Without affecting the electromagnetic performance of the motor, by changing the rotor structure of the motor, the production process cost is reduced as much as possible, and the heat dissipation performance of the motor is improved.

[0007] A low-speed outer-rotor permanent magnet motor with rotor oil storage hole grooves includes an inner stator and an outer rotor. The outer rotor is fixed on the inner surface of a rotor housing. End covers are provided at both ends of the rotor housing. The outer rotor includes a rotor core, and permanent magnets and iron magnetic poles are alternately arranged along the circumferential direction on the inner surface of the rotor core. Oil storage hole grooves are provided on all or part of the iron magnetic poles of the rotor core; a liquid cooling medium is provided in the air gap between the inner stator and the outer rotor.

[0008] In the present invention, the outer rotor no longer adopts the traditional all-permanent magnetic pole structure, but adopts an alternating pole structure. Half of the magnetic poles are composed of permanent magnets, and the other half of the magnetic poles are composed of iron magnetic poles (iron cores). The iron magnetic poles can be processed together with the rotor core, without additional process costs, and at the same time, the usage of expensive permanent magnets is reduced.

[0009] A liquid cooling medium is filled in about one-third of the space at the lower part of the motor air gap. Therefore, the heat in about one-third of the lower part of the stator can be transferred to the outer rotor and the machine shell through the liquid cooling medium. By providing oil storage hole grooves on all or part of the iron magnetic poles of the outer rotor, when the rotor iron magnetic poles with oil storage hole grooves rotate to about one-third of the lower space, the liquid cooling medium in the air gap fills into the oil storage hole grooves. When the iron magnetic poles are located in about two-thirds of the upper space as the rotor rotates, the liquid cooling medium gradually releases from the oil storage hole grooves, drips through the air gap onto about two-thirds of the upper stator, and flows back to about one-third of the lower air gap under the action of gravity, thereby transferring the heat in about two-thirds of the upper stator to the outer rotor and the machine shell.

[0010] Optionally, on the iron magnetic poles provided with oil storage hole grooves, the number of oil storage hole grooves in the axial direction is one or more.

[0011] When the number of oil storage hole grooves on the iron magnetic pole is one, the oil storage hole groove can be provided at the end or the middle of the iron magnetic pole; when the number of oil storage hole grooves on the iron magnetic pole is multiple, the multiple oil storage hole grooves can be evenly arranged on the iron magnetic pole along the axial direction.

[0012] Or, when the number of oil storage hole grooves on the iron magnetic pole is one, the oil storage hole groove can also penetrate the corresponding iron magnetic pole along the axial direction.

[0013] Due to the presence of the coolant, the oil storage hole grooves have less impact on the balance of the motor rotor. The more oil storage hole grooves there are, the better the heat dissipation conditions. However, if the temperature rise of the motor is not high, too many oil storage hole grooves are not needed, and too many grooves may affect the mechanical structure of the motor. Therefore, during the specific design and assembly process, the number and position of the oil storage hole grooves can be adjusted adaptively according to different motors.

[0014] The described oil storage hole grooves include two parts: an oil storage hole and a communication groove. The oil storage hole is communicated with the air gap between the inner stator and the outer rotor through the communication groove.

[0015] The cross-section of the oil storage hole can be circular, elliptical or other polygons.

[0016] In order to facilitate the injection of the liquid cooling medium, an oil injection hole for injecting the liquid cooling medium into the air gap of the motor is provided on the end cover.

[0017] The magnetization directions of all permanent magnets are the same, and the magnetic pole direction of the iron magnetic pole after being magnetized by the permanent magnet is opposite to that of the permanent magnet.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention has a structure of opening oil storage hole grooves on the rotor core of a low-speed outer rotor permanent magnet motor. Due to the adoption of an alternating magnetic pole structure, oil storage hole grooves can be opened on the iron magnetic poles of the rotor of this structure without additional process costs. When these iron magnetic poles rotate to about the lower one-third of the space, the liquid cooling medium in the air gap can be filled into the oil storage hole grooves. When these iron magnetic poles rotate to about the upper two-thirds of the space, the liquid cooling medium in the oil storage hole grooves gradually releases due to the action of gravity, drips onto the stator in the upper two-thirds through the air gap, and flows to the air gap in the lower one-third under the action of gravity, thereby transferring the heat in the stator in the upper two-thirds to the rotor. This greatly improves the heat dissipation conditions of the stator in the upper two-thirds, makes the temperature distribution of the entire stator relatively uniform, and avoids local overheating of the stator and shortening of the motor life. Description of the Drawings

[0020] Figure 1 It is a main sectional view of a low-speed outer rotor permanent magnet motor with rotor oil storage hole grooves according to the present invention;

[0021] Figure 2 is Figure 1 The sectional view taken along the direction of A-A shown;

[0022] Figure 3 It is a schematic diagram of an iron magnetic pole with oil storage hole grooves.

[0023] In the figure: 1 - stator shaft, 2 - stator core, 3 - stator coil, 4 - permanent magnet, 5 - rotor core, 6 - rotor housing, 7 - oil storage hole groove, 71 - oil storage hole, 72 - communication groove, 8 - bearing, 9 - end cover, 10 - oil injection hole, 11 - iron magnetic pole. Detailed implementation mode

[0024] The present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0025] As Figures 1 - 2 shown, a low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove includes an inner stator and an outer rotor. The inner stator includes a stator shaft 1, a stator core 2, and a stator coil 3; the outer rotor includes a rotor housing 6, a rotor core 5, permanent magnets 4 with an alternating pole structure, iron magnetic poles 11 with an alternating pole structure, a bearing 8, and an end cover 9.

[0026] The iron magnetic poles 11 and the rotor core 5 are manufactured together. For example, they are manufactured by stamping silicon steel sheets. The permanent magnets 4 are sequentially embedded in the inner surface of the rotor core 5, that is, between adjacent iron magnetic poles 11. The magnetization directions of all the permanent magnets are the same. For example, if all the permanent magnets 4 have their N poles facing the air gap, then the iron magnetic poles 11 are magnetized by the permanent magnets 4 and show their S poles facing the air gap. The permanent magnets can also all adopt the opposite magnetization direction, which has no difference in the performance of the motor.

[0027] In the present invention, the outer rotor no longer adopts the traditional all-permanent magnetic pole structure, but adopts an alternating pole structure. The alternating pole structure specifically means that half of the magnetic poles are composed of permanent magnets 4, and the magnetization directions of these permanent magnets 4 are the same. There is no need to make additional treatments such as drainage grooves in terms of shape, and there is no additional processing cost; while the other half of the magnetic poles are composed of iron cores, called iron magnetic poles 11. The iron magnetic poles 11 can be processed together with the rotor core 5, without additional process costs, and at the same time, the usage of expensive permanent magnets is reduced.

[0028] Optionally, oil storage hole grooves 7 are opened on all or part of the iron magnetic poles 11 of the rotor core 5. The number of oil storage hole grooves 7 on each iron magnetic pole 11 can be one or more. Along the axis of the shaft, the oil storage hole grooves 7 can penetrate the iron magnetic poles 11, or can be located at local positions such as the ends or the middle of the iron magnetic poles 11.

[0029] When the number of oil storage hole grooves 7 on the iron magnetic pole 11 is one, the oil storage hole groove 7 can be arranged at the end or the middle of the iron magnetic pole; when the number of oil storage hole grooves 7 on the iron magnetic pole 11 is multiple, the multiple oil storage hole grooves 7 can be evenly arranged on the iron magnetic pole 11 along the axis.

[0030] Alternatively, when the number of oil storage hole grooves on the iron magnetic pole 11 is one, the oil storage hole groove 7 can also penetrate the corresponding iron magnetic pole 11 axially.

[0031] During assembly, the rotor core 5 can be fixed on the inner surface of the rotor housing 6 by tight fit, glue or fasteners, and the rotor housing 6 and the end cover 9 can be fastened by screws or the like.

[0032] The iron magnetic pole 11 is provided with an oil storage hole groove 7. As Figure 3 shown, the oil storage hole groove includes two parts, an oil storage hole 71 and a communication groove 72, and the communication groove 72 connects the oil storage hole 71 with the air gap of the motor.

[0033] The end cover 9 is provided with an oil injection hole 10 for injecting a liquid cooling medium into the air gap inside the motor. After the motor is assembled, the liquid cooling medium is injected into the motor through the oil injection hole 10 until the space about one-third of the lower part of the motor is filled with the liquid cooling medium.

[0034] In this embodiment, the number, shape and position of the oil storage hole grooves 7 depend on the specific design. The cross-section of the oil storage hole 71 of the oil storage hole groove can be designed as a circle, an ellipse or a trapezoid, etc. Figure 2 In the figure, it is a circle and is connected to the motor air gap through the communication groove 72. The cross-section design and the number design of the oil storage hole grooves 7 on the iron magnetic pole 11 should not only meet the electromagnetic performance of the motor, that is, the oil storage hole grooves 7 do not damage the waveform of the magnetic field under the iron magnetic pole to ensure the electromagnetic performance of the motor, but also make the oil storage hole grooves 7 have a large enough volume to fill with the liquid cooling medium.

[0035] In Figure 2 the shown case, the iron magnetic poles 11 at the lower part of the rotor are immersed in the liquid cooling medium in the air gap, so the liquid cooling medium naturally fills into the oil storage hole grooves of these iron magnetic poles 11; at the same time, the liquid cooling medium in the oil storage hole grooves 7 in the iron magnetic poles 11 at the upper part of the rotor gradually releases due to the action of gravity, drips on the upper part of the stator, transfers the heat of the upper part of the stator to the lower air gap and then to the outer rotor. As the motor rotor rotates, there are constantly iron magnetic poles 11 entering the lower space, filling the liquid cooling medium into the oil storage hole grooves, then rotating to the upper space, gradually releasing the liquid cooling medium, dripping and cooling the upper part of the stator, and then rotating to the lower space, so on and so forth, improving the heat dissipation of the motor and avoiding local overheating of the motor stator.

[0036] The above-described embodiments have described the technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements and equivalent replacements made within the principle scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove, comprising an inner stator and an outer rotor. The outer rotor is fixed on the inner surface of a rotor housing, and end covers are provided at both ends of the rotor housing. It is characterized in that the outer rotor includes a rotor core, permanent magnets and iron magnetic poles alternately arranged along the circumferential direction on the inner surface of the rotor core. The magnetization directions of all the permanent magnets are the same, and the magnetic pole directions of the iron magnetic poles are opposite to those of the permanent magnets. Oil storage hole grooves are provided on all or part of the iron magnetic poles of the rotor core; a liquid cooling medium is provided in the air gap between the inner stator and the outer rotor. The oil storage hole groove includes two parts: an oil storage hole and a communication groove. The oil storage hole is communicated with the air gap between the inner stator and the outer rotor through the communication groove. An oil injection hole for injecting a liquid cooling medium into the air gap inside the motor is provided on the end cover. After the motor is assembled, a liquid cooling medium is injected into the motor through the oil injection hole until the space in the lower one-third of the motor is filled with the liquid cooling medium.

2. The low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove according to claim 1, It is characterized in that on the iron magnetic poles provided with oil storage hole grooves, the number of oil storage hole grooves in the axial direction is one or more.

3. The low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove according to claim 2, It is characterized in that when the number of oil storage hole grooves on the iron magnetic pole is one, the oil storage hole groove is arranged at the end or in the middle of the iron magnetic pole; when the number of oil storage hole grooves on the iron magnetic pole is multiple, the multiple oil storage hole grooves are evenly arranged on the iron magnetic pole along the axial direction.

4. The low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove according to claim 2, It is characterized in that when the number of oil storage hole grooves on the iron magnetic pole is one, the oil storage hole groove penetrates through the corresponding iron magnetic pole along the axial direction.

5. The low-speed outer-rotor permanent magnet motor with a rotor oil storage hole groove according to claim 1, It is characterized in that the cross section of the oil storage hole is circular, elliptical or polygonal.

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