Stator shaft and outer rotor permanent magnet synchronous motor with good torque transmission and heat dissipation effect

Abstract

This invention relates to a stator shaft that provides both load-bearing and torsion-transmitting properties and excellent heat dissipation. The stator shaft comprises side plates, web plates, and reinforcing ribs. The side plates include a left side plate and a right side plate. The web plates include an upper web plate and a lower web plate. The two web plates are interconnected with the middle portions of the side plates to form a U-shaped structure. The upper portions of both side plates extend above the upper web plate, with their tops located on the outer circumferential surface of the stator shaft. The lower portions of both side plates extend below the lower web plate, with their bottoms located on the outer circumferential surface of the stator shaft. The inner end of the reinforcing rib is integrated with the U-shaped structure, and its outer end is located on the outer circumferential surface of the stator shaft. This invention also relates to an external rotor permanent magnet synchronous motor, whose stator shaft utilizes the aforementioned load-bearing and torsion-transmitting stator shaft with excellent heat dissipation. This invention can further reduce the weight of the stator shaft, improve its bending and torsional resistance, and enhance its heat dissipation capacity.

Description

Technical Field

[0001] This invention relates to a permanent magnet synchronous motor with a stator shaft and external rotor that provides good load-bearing torque transmission and heat dissipation, particularly a low-speed, high-torque motor, belonging to the field of motor technology. Background Technology

[0002] Cranes have long used internal rotor wound-rotor asynchronous motors as drive motors. Since 2014, external rotor permanent magnet synchronous motors have been widely used in the lifting equipment and conveying machinery industries. They are characterized by small size, light weight, and good energy-saving effect, and are loved by many users. However, external rotor permanent magnet synchronous motors are limited by the price of permanent magnet materials and the development of permanent magnet material performance, resulting in a high initial purchase cost. They are also heavy in some working conditions. At the same time, the conventional shaft output torque is changed to the motor frame output torque, and the frame also needs to bear vertical load. This is a huge change from the conventional motor shaft only transmits torque.

[0003] The stator shafts of most existing external rotor motors are solid cylindrical shafts. To meet heat dissipation requirements, some stator shafts are hollow cylindrical shafts, with ventilation and heat dissipation achieved through axial through-holes. However, although hollow shafts offer better heat dissipation and are lighter than solid shafts, especially for high-power motors, it is still necessary to further reduce the overall weight and improve heat dissipation capacity while maintaining strength. Summary of the Invention

[0004] The purpose of this invention is to further reduce the weight of the stator shaft and improve its heat dissipation capacity.

[0005] The technical solution of the present invention is as follows: a stator shaft that bears torsion and has good heat dissipation is provided with side plates, web plates and reinforcing ribs. The side plates include a left side plate and a right side plate. The web plates include an upper web plate and a lower web plate. The middle parts of the two web plates (upper web plate and lower web plate) and the two side plates (left side plate and right side plate) are connected to each other to form a U-shaped structure. The upper part of the two side plates extends above the upper web plate, and its top end is located on the outer circular surface of the stator shaft. The lower part of the two side plates extends below the lower web plate, and its bottom end is located on the outer circular surface of the stator shaft. The inner end of the reinforcing rib is integrated with the U-shaped structure, and the outer end is located on the outer circular surface of the stator shaft.

[0006] Both web plates can be horizontal flat plates, and both side plates can be vertical flat plates.

[0007] The flat plate used as the web can be a flat plate of uniform thickness or a flat plate of unequal thickness.

[0008] The flat plate used as the side plate can be a flat plate of uniform thickness or a flat plate of unequal thickness.

[0009] The width of the web is preferably no greater than the width of the middle part of the side plate, so that the cross-section of the resulting U-shaped structure is rectangular with four sides of equal length or the top and bottom sides being shorter.

[0010] The thickness of the upper web is preferably greater than that of the lower web.

[0011] The thickness of both side plates is preferably the same.

[0012] The reinforcing ribs can be one or more sets.

[0013] The number of stiffeners in the same group is two, preferably distributed in a 180° rotational symmetry, with the axis of rotational symmetry being the axis of the stator.

[0014] The reinforcing rib may include a first reinforcing rib, which extends radially.

[0015] The number of the first reinforcing ribs is preferably two.

[0016] The two first reinforcing ribs are preferably set on one side of the upper part of one side plate and the lower part of the other side plate, respectively, forming a stable small triangular structure (a columnar structure with a cross-section that is or approximately triangular) with the upper or lower part of the adjacent side plate and the stator core at the corresponding location.

[0017] For example, one of the two first reinforcing ribs is preferably located on the rear side of the upper part of the side plate, forming a stable small triangle structure with the upper part of the side plate and the stator core in the corresponding part. The other of the two first reinforcing ribs is preferably located on the rear side of the lower part of the side plate, forming a stable small triangle with the lower part of the side plate and the stator core in the corresponding part.

[0018] A second reinforcing rib may or may not be provided.

[0019] The inner end of the second reinforcing rib can be connected to the U-shaped structure, and the outer end is located on the outer circular surface of the stator shaft. The extension direction of the second reinforcing rib forms an angle with the radial direction of the stator shaft.

[0020] The outer end of the second reinforcing rib is preferably inclined to the rear.

[0021] External rotor permanent magnet synchronous motors, especially low-speed, high-torque motors, are equipped with stator shafts, wherein the stator shaft is any stator shaft disclosed in this invention that can bear torque transmission and has good heat dissipation.

[0022] The beneficial effects of this invention are as follows: Because the main body of the stator shaft is a small-section hollow rectangle, the outer circular surface of the stator shaft is formed by the outwardly extending side plates and the outer ends of the reinforcing ribs, which are used to install and support the stator core. This not only creates an internal cavity and a side cavity, but also, through reasonable design, greatly increases the cross-sectional area of ​​the cavity and its area ratio on the stator shaft cross-section. This not only helps to reduce the self-weight of the stator shaft, reduce the load caused by its self-weight, and reduce material consumption, but also expands the flow area of ​​the heat dissipation channel and increases the area between the cavity and the stator shaft solid. The increased interface area, or heat exchange area, between the stator and stator core significantly improves heat dissipation capacity. These cavities can be used as forced cooling channels according to actual needs, employing forced air cooling, oil cooling, water cooling, or other suitable methods to meet higher heat dissipation / cooling requirements. Simultaneously, this structure also possesses excellent torsional resistance, significantly improving torsional stiffness. Because the side plates adopt a flange design, extending to the outer surface of the stator shaft at both ends, the distance between the two side plates is significantly smaller than the inner diameter of the stator core, enabling the side plates to maintain vertical stability under appropriate conditions. Maximizing the dimensions of the web significantly improves the ability to bear vertical loads (gravity) and significantly improves bending stiffness. It also helps reduce the width of the web, significantly reducing web weight and material consumption without substantially affecting bending stiffness. Due to the radial (stator radial) extension of the first stiffener, located on one side (front or rear in the circumferential direction) of the adjacent side plate extension (upper or lower part of the side plate), it connects with the side plate extension and the corresponding part (stator iron connecting the stiffener and the side plate extension). The stator core (core) forms a stable small triangular structure, which improves the integrity and torsional stiffness of the stator shaft. Moreover, under the action of torque or tangential (stator tangential) force, the stress on any cross section perpendicular to the radial direction of the stiffener includes not only shear stress but also normal stress. The normal stress in the circumferential front side (front side in the direction of the tangential force involved in the power torque) is compressive stress, which produces a compression effect, resulting in a smaller lattice constant and increased atomic coupling in the region. At the same time, the normal stress in the rear side is tensile stress, which significantly enhances the ability to resist torsional deformation.

[0023] The outer cylindrical surface of the stator shaft (the cylindrical surface at the upper and lower ends of the side plate and the outer end of the reinforcing rib, which is equivalent to the circumscribed cylindrical surface) is the assembly position of the stator core, and the axial extension of the middle rectangle is the bearing assembly position. This can reduce the bending moment deformation and torsional deformation of the stator shaft. Furthermore, the large-area channel design on the stator shaft not only reduces the self-weight of the mechanism and improves heat dissipation efficiency, but also reduces the overall cost. Attached Figure Description

[0024] Figure 1 This is a three-dimensional structural diagram involving the stator shaft; Figure 2 This is a schematic diagram of the main structure of the stator shaft; Figure 3 This is a schematic cross-sectional view of a main part of the stator shaft; Figure 4 This is a schematic cross-sectional view of another main part involving the stator shaft; Figure 5 This is a schematic cross-sectional view of the third main body part involving the stator shaft. Detailed Implementation

[0025] See Figure 1-5 The stator shaft 10 of the present invention adopts a hollow structure, with the central part being a rectangular tube or a U-shaped structure. The upper part 13 of the left and right side plates 12 extends upward from the upper web plate (or upper web plate) 11, with the top end located on the outer circular surface of the stator shaft. The lower part 14 extends downward from the lower web plate (or lower web plate) 11, with the bottom end located on the outer circular surface of the stator shaft. The middle parts of the left and right side plates and the upper and lower web plates are fixedly connected end to end in sequence to form a U-shaped structure. The stator core 20 is fixedly installed on the outer circular surface of the stator shaft.

[0026] Several reinforcing ribs can be added according to actual needs.

[0027] The reinforcing rib includes a first reinforcing rib 15, which extends radially, with its inner end connected to the U-shaped structure and its outer end located on the outer circular surface of the stator shaft.

[0028] Typically, the first reinforcing rib can be placed on the rear side (the rear side in the direction of the tangential force involved in the power torque) of the adjacent side plate extension (the part extending upward or downward from the U-shaped structure, that is, the upper or lower part of the side plate). It forms a stable small triangle with the side plate extension and the stator core of the corresponding part (the stator core between the reinforcing rib and the side plate extension). The reinforcing rib has a certain thickness (equivalent to the tangential dimension). Under the action of the power torque of the motor, it generates shear stress, compressive stress in the front area and tensile stress in the rear area. This stress helps to improve torsional rigidity.

[0029] The reinforcing rib may further include a second reinforcing rib 16, the inner end of which is connected to the U-shaped structure, and the outer end which is located on the outer circumferential surface of the stator shaft. The extension direction of the second reinforcing rib forms an angle with the radial direction of the stator shaft, preferably with the outer end inclined to the rear. In this case, the angle between its extension direction and the radial direction of the stator shaft can be 10-30° (based on the radial direction passing through its inner end). Since the outer end is inclined to the rear, the area with compressive stress will be significantly larger than the area with compressive stress in the first reinforcing rib when the motor is working, which helps to increase the torsional resistance or torsional stiffness.

[0030] The second reinforcing rib may or may not be installed depending on actual needs.

[0031] A torsion-resistant reinforcing plate 17 can be provided within the U-shaped structure or within the shaft cavity. The torsion-resistant reinforcing plate can be a single plate or multiple small plates spaced apart along the axial direction. The two ends of the torsion-resistant reinforcing plate are respectively connected (e.g., welded) to two opposite corners of the U-shaped structure. By providing the torsion-resistant reinforcing plate, the torsion resistance can be significantly improved, especially for thicker stator shafts.

[0032] The rectangular cavity in the middle of the stator shaft (inner cavity) 1 and the side cavity between the stator shaft and the stator core (side cavity) 2 can both be used as cooling channels. Forced air cooling is preferred for the cooling channels, but forced oil cooling or water cooling can also be used. The appropriate cooling method can be selected according to actual needs, and various cooling pipes can be laid in the cooling channels.

[0033] The thickness of the upper web is greater than that of the lower web, which helps to reduce metal fatigue and improve torsional resistance with the same amount of material.

[0034] The number of reinforcing ribs can be 2-8, usually an even number, with two ribs forming a group.

[0035] In the cross-sectional area of ​​the stator shaft (the area located within the outer circular surface of the stator shaft), the area of ​​the cooling channel can account for 50%-75%.

[0036] The external rotor permanent magnet synchronous motor adopts the above-mentioned stator shaft. The two ends of the stator shaft are shaft extensions 19, which are extensions of the loop structure. The extensions can be the same diameter as the loop structure of the main body of the stator shaft, or smaller than the loop structure of the main body of the stator shaft. The stator shaft can be fixedly installed on the housing (on the end cover of the housing) through these extensions. Other parts of the motor can adopt existing technology.

[0037] Based on the applicant's experiments, using the same steel and similar amount of steel as the existing circular hollow stator shaft, this stator shaft can significantly improve bending resistance and strength. For external rotor permanent magnet synchronous motors used in crane direct mechanisms, the shaft bending moment deformation of this stator shaft is no more than 0.2 mm, the maximum torsional deformation is no more than 1 mm, and the thermal equilibrium temperature of the mechanism at 100% operation does not exceed 160℃.

[0038] Unless otherwise specified or further limited to one preferred or optional technical means being another, the preferred and optional technical means disclosed in this invention can be arbitrarily combined to form several different technical solutions.

Claims

1. A low-speed, high-torque motor stator shaft with good load-bearing capacity, torque transmission, and heat dissipation, characterized by its hollow structure. The central section is a small-section rectangular tube with side plates, webs, and reinforcing ribs. The side plates include a left side plate and a right side plate, and the webs include an upper web and a lower web. The upper web is thicker than the lower web. The two webs and the middle of the two side plates are connected to form a U-shaped structure, thus forming the rectangular tube. The upper and lower parts of the two side plates extend above the upper web and below the lower web, respectively. The inner ends of the reinforcing ribs are integrated with the U-shaped structure. The outer ends of the outwardly extending side plates and reinforcing ribs form the outer circular surface of the stator shaft, used for mounting and supporting the stator core. The reinforcing ribs include two radially extending first reinforcing ribs and a second reinforcing rib. The two first reinforcing ribs are respectively arranged... In the adjacent side plate extensions in the upper and lower parts, the rear side plate extension, together with the side plate extension and the corresponding part of the stator core, forms a stable small triangle. The inner end of the second reinforcing rib is connected to the loop structure, and the outer end is located on the outer circular surface of the stator shaft. The extension direction of the second reinforcing rib forms an angle with the radial direction of the stator shaft. The outer end of the second reinforcing rib is inclined to the rear. An anti-torsion reinforcing plate is provided in the loop structure. The two ends of the anti-torsion reinforcing plate are respectively connected to the two opposite corners of the loop structure. The rectangular cavity in the middle of the stator shaft and the side cavity between the stator shaft and the stator core are used as cooling channels. The area of ​​the cooling channel accounts for 50%-75% of the cross-sectional area of ​​the stator shaft.

2. The low-speed, high-torque motor stator shaft as described in claim 1, characterized in that... The width of the web is not greater than the width of the middle part of the side plate.

3. The low-speed, high-torque motor stator shaft as described in claim 1, characterized in that... The reinforcing ribs are in one or more groups, with two ribs in each group, distributed 180° rotationally symmetrically, and the axis of rotational symmetry is the axis of the stator shaft.

4. The stator shaft of a low-speed, high-torque motor as described in any one of claims 1-3, characterized in that... Both web plates are horizontal flat plates, and both side plates are vertical flat plates.

5. The low-speed, high-torque motor stator shaft as described in claim 4, characterized in that... The flat plate used as the web is either a plate of equal thickness or a plate of unequal thickness.

6. The low-speed, high-torque motor stator shaft as described in claim 4, characterized in that... The flat plate used as the side plate is either a flat plate of equal thickness or a flat plate of unequal thickness.

7. A low-speed, high-torque external rotor permanent magnet synchronous motor, equipped with a stator shaft, characterized in that... The stator shaft is the low-speed, high-torque motor stator shaft as described in any one of claims 1-6.

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