A brushless direct current motor with an anti-electric corrosion structure

Abstract

This utility model discloses a brushless DC motor with an anti-electro-corrosion structure, comprising a stator unit, a rotor, a motor shaft connected in the middle of the rotor, bearings at both ends, a metal front cover at the front end of the stator unit, a metal rear cover at the rear end of the stator unit, conductive plates, and an insulating fixing plate. The bearings are connected to the motor shaft. A stator assembly is disposed within the stator unit. The bearings at both ends are respectively located inside the metal front cover and the metal rear cover, and are in contact with both the bearings. The insulating fixing plate is fixed to the end of the stator assembly near the metal rear cover. The front end of the conductive plate is fixedly connected to the metal front cover and is conductive. The rear end of the conductive plate is fixed to the insulating fixing plate and partially exposed on the surface of the stator unit. When the metal rear cover is closed on the stator unit, the metal rear cover contacts the exposed portion of the conductive plate and is conductive. This utility model effectively prevents bearing electro-corrosion and is low in cost.

Description

Technical Field

[0001] This utility model belongs to the technical field of brushless DC motors, specifically relating to a brushless DC motor with an anti-electro-corrosion structure. Background Technology

[0002] During motor operation, due to factors such as stator slotting, core lamination process, uneven magnetization of magnets, and asymmetrical winding distribution, magnetic field asymmetry is unavoidable (the asymmetry is more pronounced in fractional-slot motors). This asymmetry induces an alternating magnetic flux around the motor shaft during rotation. This alternating circular magnetic flux induces a voltage along the motor shaft direction, i.e., shaft voltage. (The more complex the pole and slot configuration, the richer the magnetic field harmonics, the greater the possibility of magnetic circuit imbalance, and the higher the amplitude of the induced shaft voltage usually is.)

[0003] On the other hand, when the motor rotates at high speed, friction between the rotor and the air or cooling medium, as well as the shearing of the lubricating oil film inside the bearings, can generate static charge. If the charge cannot be effectively discharged, it will accumulate on the motor shaft, forming shaft voltage.

[0004] When the shaft voltage accumulates to a level exceeding the insulation strength of the oil film formed by the grease or lubricating oil inside the bearing, the oil film will break down. The breakdown instant generates a tiny electric arc discharge, and current flows from the motor shaft through the balls / rollers to the outer ring of the bearing. Continuous shaft current causes bearing electro-corrosion, leading to surface roughening, increased noise, and intensified vibration, ultimately affecting the lifespan of the motor bearing. Utility Model Content

[0005] The purpose of this invention is to provide a low-cost brushless DC motor that can effectively prevent bearing electro-corrosion.

[0006] The objective of this utility model is achieved through the following technical solution:

[0007] A brushless DC motor with an anti-electro-corrosion structure includes a stator unit, a rotor, a motor shaft connected in the middle of the rotor, and bearings at both ends. The bearings are connected to the motor shaft. A stator assembly is arranged inside the stator unit. The brushless DC motor further includes a metal front cover at the front end of the stator unit, a metal rear cover covering the rear end of the stator unit, a conductive plate, and an insulating fixing plate. The bearings at both ends are respectively located inside the metal front cover and the metal rear cover, and the bearings are in contact with the metal front cover and the metal rear cover. The insulating fixing plate is fixed to one end of the stator assembly near the metal rear cover. The front end of the conductive plate is fixedly connected to the metal front cover and can conduct electricity. The rear end of the conductive plate is fixed to the insulating fixing plate and partially exposed on the surface of the stator unit. When the metal rear cover is closed on the stator unit, the metal rear cover is in contact with the exposed part of the conductive plate and can conduct electricity.

[0008] A further technical solution of this utility model is as follows: an extension strip is provided on the insulating fixing plate, extending towards the metal rear end cover, and a barb is formed at the rear end of the conductive piece. The barb is engaged with the extension strip, and the part of the barb is exposed on the surface of the stator unit.

[0009] A further technical solution of this utility model is: a protrusion is provided on the inner side of the metal rear end cover, and when the metal rear end cover is closed on the stator unit, the protrusion contacts the exposed part of the conductive plate.

[0010] A further technical solution of this utility model is: the insulating fixing plate is provided with a support strip that crosses over from the outside of the stator assembly, and the conductive pieces are arranged along the top of the support strip.

[0011] A further technical solution of this utility model is: a slot is provided on the support bar, and part of the conductive piece is stuck in the slot.

[0012] A further technical solution of this utility model is as follows: a limiting block and a slot are provided at one end of the stator assembly near the metal rear end cover, and a limiting groove and an insert block are provided on the insulating fixing plate. The insert block is inserted into the slot, and the limiting block is embedded in the limiting groove.

[0013] A further technical solution of this utility model is: the inner side of both the metal front end cover and the metal rear end cover is provided with a bearing receiving groove, and the bearing is assembled in the bearing receiving groove.

[0014] A further technical solution of this utility model is that the front end of the conductive piece is fixedly connected to the metal front end cover by rivets.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] This invention incorporates a conductive plate within the stator unit, which connects the metal front and rear end covers, thereby connecting the bearings at both ends. This creates a continuous, equipotential conductor, providing a low-impedance capacitive coupling discharge path for induced shaft voltage, effectively preventing bearing electro-corrosion. This invention eliminates the need for discharge through a highly impeded bearing oil film, effectively preventing bearing electro-corrosion. Furthermore, the connection and conduction method of the front and rear end covers is simple, reliable, and low-cost. Attached Figure Description

[0017] Figure 1 This is a three-dimensional schematic diagram of a brushless DC motor according to an embodiment of the present utility model;

[0018] Figure 2 This is a three-dimensional schematic diagram of the brushless DC motor with the metal rear end cover disassembled according to an embodiment of the present invention;

[0019] Figure 3This is a cross-sectional schematic diagram of a brushless DC motor according to an embodiment of the present utility model;

[0020] Figure 4 This is a schematic diagram of the assembly structure of the conductive piece and the insulating fixing plate according to an embodiment of the present utility model;

[0021] Figure 5 This is a structural schematic diagram of the hidden portion of the brushless DC motor according to an embodiment of the present invention;

[0022] Figure 6 This is a perspective view of the metal rear end cover according to an embodiment of the present utility model;

[0023] Figure 7 This is a schematic diagram of the stator assembly and rotor portion according to an embodiment of the present utility model;

[0024] Figure 8 This is a three-dimensional schematic diagram of the insulating fixing plate according to an embodiment of the present utility model.

[0025] Meaning of the labels in the attached diagram:

[0026] 1-Stator unit; 2-Motor shaft; 3-Metal rear end cover; 3.1-Protrusion; 4-Rotor; 5-Bearing; 6-Conductor plate; 6.1-Exposed portion of conductor plate; 6.2-Barb; 6.3-Front end of conductor plate; 7-Insulating fixing plate; 7.1-Extension strip; 7.2-Support strip; 7.3-Slot; 7.4-Limiting groove; 7.5-Insertion block; 8-Metal front end cover; 9-Stator assembly; 9.1-Limiting block; 9.2-Slot; 10-Bearing receiving groove. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments.

[0028] Example:

[0029] like Figures 1 to 8 The brushless DC motor with anti-electro-corrosion structure shown in this embodiment includes a stator unit 1, a rotor 4, a motor shaft 2 connected in the middle of the rotor 4, bearings 5 ​​at both ends, a metal front end cover 8 at the front end of the stator unit 1, a metal rear end cover 3 covering the rear end of the stator unit 1, a conductive plate 6, and an insulating fixing plate 7. The metal front end cover 8, the metal rear end cover 3, and the conductive plate 6 are all made of metal and are conductive, while the insulating fixing plate 7 is made of insulating material.

[0030] The stator unit 1 is integrally injection molded using BMC. A stator assembly 9 is installed inside the stator unit 1, and the stator assembly 9 is encased in BMC material after injection molding. The edge of the metal front cover 8 is injection molded together with the front end of the stator unit 1. The conductive piece 6 and the insulating fixing plate 7 are injection molded into the stator unit 1, but the barb 6.2 at the rear end of the conductive piece 6 is exposed on the surface of the stator unit 1. The rotor 4 is fitted into the middle of the stator unit 1. The rear end of the motor shaft 2 extends to the inside of the metal rear cover 3, and the front end of the motor shaft 2 passes through the central hole of the metal front cover 8 to the outside. Bearing receiving grooves 10 are provided inside both the metal front cover 8 and the metal rear cover 3. The bearings 5 ​​at both ends are connected to the motor shaft 2 in a conventional manner and assembled in the bearing receiving grooves 10. The bearings 5 ​​at both ends contact the metal front cover 8 and the metal rear cover 3 respectively, allowing electrical conductivity between the front bearing 5 and the metal front cover 8, and between the rear bearing 5 and the metal rear cover 3.

[0031] The insulating fixing plate 7 is fixed to one end of the stator assembly 9 near the metal rear end cover 3. The specific fixing structure is as follows: Figure 7 and Figure 8 As shown, limiting grooves 7.4 are provided on the inner sides of both ends and the middle sides of the insulating fixing plate 7. Insertion blocks 7.5 are also provided on the insulating fixing plate 7. A limiting block 9.1 and a slot 9.2 are provided on the end of the stator assembly 9 near the metal rear end cover 3. Insertion blocks 7.5 are inserted into slot 9.2, and limiting blocks 9.1 are embedded in limiting grooves 7.4.

[0032] The front end 6.3 of the conductive piece is fixedly connected to the metal front end cover 8 by rivets and conducts electricity. The rivet connection ensures the reliability of the fixed connection.

[0033] like Figure 4 and Figure 5 As shown, the insulating fixing plate 7 has an extension strip 7.1 extending towards the metal rear end cover and a support strip 7.2 crossing over the outside of the stator assembly 9. A slot 7.3 is provided on the support strip 7.2. The conductive piece 6 is arranged along the upper part of the support strip 7.2 and partially engaged in the slot 7.3. The support strip 7.2 ensures that the conductive piece 6 does not contact the stator core. A barb 6.2 is formed by bending at the rear end of the conductive piece 6, and the barb 6.2 engages with the extension strip 7.1. After the stator unit 1 is injection molded, the portion of the barb 6.2 will be exposed on the surface of the stator unit 1.

[0034] In this embodiment, a protrusion 3.1 is provided on the inner side of the metal rear end cover 3. The protrusion 3.1 is a raised point or rib on the inner side of the metal rear end cover 3. When the metal rear end cover 3 is closed on the stator unit 1, the protrusion 3.1 contacts the exposed portion 6.1 of the conductive piece, thereby enabling electrical conductivity between the metal rear end cover 3 and the conductive piece 6. The structure of the metal rear end cover 3 closing on the rear end of the stator unit 1 adopts a conventional closing structure.

[0035] like Figure 3 As shown, when the metal rear end cover 3 is closed on the rear end of the stator unit 1 and the assembly is completed, the conductive piece 6 connects the metal front end cover 8 and the metal rear end cover 3, thereby connecting the bearings 5 ​​at both ends, so that the bearings 5 ​​at both ends are connected into a continuous, equipotential conductor, providing a low-impedance capacitive coupling discharge path for the induced shaft voltage, thereby effectively preventing the bearings 5 ​​from electro-corrosion.

[0036] The above embodiments of this utility model are not intended to limit the scope of protection of this utility model. The implementation of this utility model is not limited thereto. All other modifications, substitutions or alterations made to the above structure of this utility model based on the above content of this utility model and in accordance with the common technical knowledge and conventional means in the field, without departing from the basic technical idea of ​​this utility model, shall fall within the scope of protection of this utility model.

Claims

1. A brushless DC motor with an anti-electro-corrosion structure, comprising a stator unit, a rotor, a motor shaft connected in the middle of the rotor, and bearings at both ends, wherein the bearings are connected to the motor shaft, and a stator assembly is disposed within the stator unit, characterized in that: The brushless DC motor also includes a metal front cover at the front end of the stator unit, a metal rear cover at the rear end of the stator unit, a conductive plate, and an insulating fixing plate. The bearings at both ends are respectively located inside the metal front cover and the metal rear cover, and the bearings are in contact with the metal front cover and the metal rear cover. The insulating fixing plate is fixed at one end of the stator assembly near the metal rear cover. The front end of the conductive plate is fixedly connected to the metal front cover and can conduct electricity. The rear end of the conductive plate is fixed to the insulating fixing plate and partially exposed on the surface of the stator unit. When the metal rear cover is closed on the stator unit, the metal rear cover is in contact with the exposed part of the conductive plate and can conduct electricity.

2. The brushless DC motor with an anti-electro-corrosion structure according to claim 1, characterized in that: The insulating fixing plate is provided with an extension strip extending toward the metal rear end cover. The rear end of the conductive piece is formed with a barb, which is engaged with the extension strip. The barb is exposed on the surface of the stator unit.

3. The brushless DC motor with an anti-electro-corrosion structure according to claim 2, characterized in that: The inner side of the metal rear end cover is provided with a protrusion. When the metal rear end cover is closed on the stator unit, the protrusion contacts the exposed part of the conductive plate.

4. The brushless DC motor with an anti-electro-corrosion structure according to claim 1, characterized in that: The insulating fixing plate is provided with a support strip that crosses over the outside of the stator assembly, and the conductive piece is arranged along the top of the support strip.

5. The brushless DC motor with an anti-electro-corrosion structure according to claim 4, characterized in that: The support bar has a slot, and part of the conductive piece is locked in the slot.

6. The brushless DC motor with an anti-electro-corrosion structure according to claim 1, characterized in that: The stator assembly has a limiting block and a slot at one end near the metal rear end cover. The insulating fixing plate has a limiting groove and an insert block. The insert block is inserted into the slot, and the limiting block is embedded in the limiting groove.

7. The brushless DC motor with an anti-electro-corrosion structure according to claim 1, characterized in that: Both the metal front end cover and the metal rear end cover have bearing receiving grooves on their inner sides, and the bearings are assembled in the bearing receiving grooves.

8. The brushless DC motor with an anti-electro-corrosion structure according to claim 1, characterized in that: The front end of the conductive piece is fixedly connected to the metal front end cover by rivets.

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