Structure for reducing shaft voltage of variable frequency motor

Abstract

The invention provides a structure for reducing the shaft voltage of a variable frequency motor, and relates to the field of external rotor motors, the structure comprises a motor base, a bearing is arranged in the motor base, the bearing is connected with a motor shaft, the motor base is in interference fit connection with a conductive brush base, and the conductive brush base is in interference fit connection with a conductive brush; the conductive brush comprises an aluminum alloy frame and a plurality of conductive fibers located on the aluminum alloy frame. And the small shaft is connected to the motor shaft, corresponds to the conductive brush in position and is matched with the conductive brush for use. The external rotor motor has the beneficial effects that the external rotor motor is suitable for all three-phase winding variable-frequency speed regulation or chopping speed regulation external rotor motors, stator and rotor conduction current is effectively guided through the conductive brush by structural optimization, and the current flows away from the conductive brush instead of a bearing, so that the bearing is effectively protected; and the labyrinth groove is designed between the conductive brush seat and the small shaft, so that the voltage of the motor shaft is effectively reduced, conductive brush powder is prevented from entering the bearing to pollute grease, the bearing is protected, and the service life of the bearing is prolonged.

Description

Technical Field

[0001] The invention relates to the field of outer rotor motors, in particular to a structure for reducing shaft voltage of a variable frequency motor. Background Art

[0002] The variable frequency motor is an AC speed regulation method that uses a special variable frequency induction motor plus a frequency converter. The motor speed and torque are controlled by adjusting the motor power supply frequency, thereby improving the degree of mechanical automation and production efficiency. The basic principle of the variable frequency motor is to decouple the frequency and voltage of the AC power supply so that the motor can maintain a good operating state under different working conditions. Its key component is the frequency converter, which usually consists of three parts: a rectifier, a filter, and an inverter. The rectifier converts the AC power supply into DC power, the filter smoothes the pulsating DC power generated after rectification into a stable DC power, and the inverter converts the stable DC power into AC power with adjustable frequency and voltage again. The frequency regulation is achieved by controlling the switch tube (such as IGBT), thereby realizing the regulation of the motor speed.

[0003] Shaft voltage is commonly found in variable frequency motors. The main reasons for its generation are: ① The motor with variable frequency control (PWM) will inevitably generate shaft voltage due to the existence of common mode voltage. ② The motor harmonic magnetic field induces electric potential. ③ The mechanical asymmetry caused by manufacturing leads to asymmetric magnetic circuit and magnetic resistance, which generates electric potential. In addition, the damage of shaft voltage to the bearing, when the shaft voltage reaches a certain value, it will break through the bearing oil film to generate partial discharge, thereby causing electrical corrosion to the bearing raceway and ball, which will cause noise during the operation of the bearing, affecting the bearing life, and in severe cases, causing the bearing to lock and fail.

[0004] Therefore, in order to solve the above problems, the conductive brush is added to effectively guide the stator and rotor current, so that the current flows through the conductive brush instead of the bearing, thereby effectively protecting the bearing. However, the friction between the conductive brush and the shaft will also produce powder, which will enter the bearing and contaminate the grease, affecting the service life of the bearing. Summary of the invention

[0005] The present invention overcomes the shortcomings of the prior art and provides a structure for reducing the shaft voltage of a variable frequency motor, which effectively reduces the shaft voltage of the motor while preventing conductive brush powder from entering the bearing to contaminate the grease, thereby protecting the bearing and increasing the service life of the bearing.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] A structure for reducing the shaft voltage of a variable frequency motor comprises a motor base, a bearing is arranged in the motor base, a motor shaft is connected to the bearing, a conductive brush base is connected to the motor base through interference fit, and a conductive brush is connected to the conductive brush base through interference fit; the bearing and the conductive brush are respectively arranged on the upper and lower sides of the conductive brush base; the conductive brush comprises an aluminum alloy frame and a plurality of conductive fibers arranged on the aluminum alloy frame; and further comprises a small shaft connected to the motor shaft, the small shaft and the conductive brush correspond in position and are used in matching manner; when the motor shaft rotates, the stator and rotor of the motor are connected through contact friction between the conductive fibers and the small shaft, thereby eliminating the potential difference between the surfaces of the stator and rotor; a labyrinth passage is formed between the small shaft and the conductive brush base to prevent powder generated by friction between the conductive fibers and the small shaft from falling into the bearing.

[0008] Furthermore, the labyrinth channel includes a first labyrinth groove on the small shaft and a second labyrinth groove on the conductive brush holder; the small shaft is arranged in a T shape, the first labyrinth groove is opened at the lower part of both sides, and an outer edge is formed on the outer side of the first labyrinth groove; an inner edge is formed on the inner side of the second labyrinth groove in the conductive brush holder; in the assembled state, the inner edge is embedded in the first labyrinth groove and maintains a distance, and the outer edge is embedded in the second labyrinth groove and maintains a distance.

[0009] Furthermore, the small shaft includes a hollow cylindrical tube for connecting with the conductive fiber, and the center of the hollow cylindrical tube is connected with a fixing hole; the top of the small shaft is also provided with an upper recessed position for assembling the motor shaft, and the upper recessed position is connected with the fixing hole.

[0010] Furthermore, a disassembly screw hole is longitudinally arranged on the conductive brush holder; and a rounded corner is formed on the end surface edge of the conductive brush holder to prevent the motor holder from being scratched during assembly.

[0011] Furthermore, a lower recessed position for installing the conductive brush is provided below the conductive brush holder, and a through hole is connected above the lower recessed position so that the hollow cylindrical tube of the small shaft can pass through the through hole for assembly.

[0012] Furthermore, the aluminum alloy frame is in a ring shape with an inner wall surface; a plurality of conductive fibers are distributed on the inner wall surface around the center of the aluminum alloy frame; and a plurality of conductive fibers are located on the same plane and extend toward the direction of the small axis to connect with each other.

[0013] Furthermore, the aluminum alloy frame is provided with riveting positions for fixing the conductive fibers.

[0014] Furthermore, the aperture of the hollow cylindrical tube is larger than the aperture of the fixing hole.

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

[0016] The present invention is applicable to all three-phase winding variable frequency speed regulation or chopper speed regulation outer rotor motors. Through structural optimization, the stator and rotor conduction current is effectively guided by the conductive brushes, and the current flows through the conductive brushes instead of the bearings, thereby effectively protecting the bearings. In addition, a labyrinth groove is designed between the conductive brush seat and the small shaft, which effectively reduces the motor shaft voltage while preventing conductive brush powder from entering the bearing to contaminate the grease, thereby protecting the bearings and increasing the service life of the bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present invention and are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 It is a general diagram of the structure for reducing the shaft voltage of the variable frequency motor according to the present invention;

[0019] Figure 2 yes Figure 1 Enlarged view of circle A in the middle;

[0020] Figure 3 It is a structural schematic diagram of the conductive brush holder and the small shaft in combination;

[0021] Figure 4 It is a structural schematic diagram of the conductive brush holder and the small shaft being separated;

[0022] Figure 5 It is a schematic diagram of the structure of a conductive brush.

[0023] In the figure:

[0024] 1. Motor seat; 2. Bearing; 3. Motor shaft; 4. Conductive brush seat; 401. Second labyrinth groove; 402. Inner edge; 403. Disassembly screw hole; 404. Rounded corner; 405. Lower recessed position; 406. Through hole; 5. Conductive brush; 501. Aluminum alloy frame; 5011. Riveting position; 502. Conductive fiber; 6. Small shaft; 601. First labyrinth groove; 602. Outer edge; 603. Hollow cylindrical tube; 604. Fixing hole; 605. Upper recessed position. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0026] like Figures 1 to 5As shown, the present invention discloses a structure for reducing the shaft voltage of a variable frequency motor, comprising a motor base 1, a bearing 2 is arranged in the motor base 1, and a motor shaft 3 is connected to the bearing 2, so that the motor shaft 3 can rotate relative to the motor base 1; during assembly, the conductive brush 5 is firstly press-fitted on the conductive brush base 4 by interference fit, and then the whole is press-fitted into the motor base 1 by interference fit, and the conductive brush 5 comprises an aluminum alloy frame 501 and a plurality of conductive fibers 502 located on the aluminum alloy frame 501; in this embodiment, the aluminum alloy frame 501 is annular with an inner wall surface; the plurality of conductive fibers 502 are distributed on the inner wall surface around the center of the aluminum alloy frame 501, and a rivet pressing position 5011 for fixing the conductive fibers 502 is arranged on the aluminum alloy frame 501, and after the conductive fibers 502 are correspondingly inserted into the installation position of the aluminum alloy frame 501 during processing, a rivet pressing head is used to press into the rivet pressing position 5011, so that the conductive fibers 502 can be fixed in the aluminum alloy frame 501.

[0027] It also includes a small shaft 6 connected to the motor shaft 3, which is fixed to the motor shaft 3 by bolt connection. The small shaft 6 corresponds to the conductive brush 5 and is used in a matching manner. A plurality of conductive fibers 502 are located on the same plane, extend toward the small shaft 6, and are connected to the small shaft 6. The structure is compact. Therefore, when the motor shaft 3 rotates during operation, the contact friction between the conductive fibers 502 and the small shaft 6 connects the stator and rotor of the motor, thereby eliminating the potential difference between the surfaces of the stator and rotor.

[0028] Since the friction between the conductive fiber 502 in the conductive brush 5 and the small shaft 6 will produce powder, in this structure, the bearing 2 and the conductive brush 5 are respectively arranged on the upper and lower sides of the conductive brush holder 4, which first serves as a position isolation. In addition, a maze passage is formed between the small shaft 6 and the conductive brush holder 4 to prevent the powder generated by the friction between the conductive fiber 502 and the small shaft 6 from falling into the bearing 2.

[0029] Specifically, from Figure 3 as well as Figure 4It can be seen that the labyrinth channel is composed of a first labyrinth groove 601 on the small shaft 6 and a second labyrinth groove 401 on the conductive brush holder 4; the small shaft 6 is set to a T shape, the first labyrinth groove 601 is opened at the lower part of both sides, and the outer side of the first labyrinth groove 601 is formed with an outer edge 602; the inner side of the second labyrinth groove 401 in the conductive brush holder 4 is formed with an inner edge 402; in the assembled state, the inner edge 402 is embedded in the first labyrinth groove 601 and maintains a distance, and the outer edge 602 is embedded in the second labyrinth groove 401 and maintains a distance, and the channel formed by the above distance is the labyrinth channel; the purpose of using the labyrinth channel is that since the small shaft 6 rotates relative to the conductive brush holder 4, the connection between the two adopts this non-direct contact method without wear. In addition, the communication path between the conductive fiber 502 and the small shaft 6 is tortuous and the powder is not easily transported to the bearing 2, which protects the bearing 2 and extends the service life of the bearing 2.

[0030] The small shaft 6 includes a hollow cylindrical barrel 603 for connecting with the conductive fiber 502, and the center of the hollow cylindrical barrel 603 is connected with a fixing hole 604; the top of the small shaft 6 is also provided with an upper recessed position 605 for assembling the motor shaft 3, and the upper recessed position 605 is connected with the fixing hole 604; during assembly, the recessed position 605 is embedded corresponding to the end of the motor shaft 3, and a bolt is used to penetrate the hollow cylindrical barrel 603 and the fixing hole 604 to connect and fix to the motor shaft 3. Since the head diameter of the bolt is larger than the body diameter, in this embodiment, the aperture of the hollow cylindrical barrel 603 is designed to be larger than the aperture of the fixing hole 604 to match the use of the bolt. The hollow cylindrical barrel 603 adopts a hollow design, which is helpful for screwing in the bolt and also has a wrapping effect on the bolt, without affecting the connection with the conductive fiber 502.

[0031] A disassembly screw hole 403 is longitudinally arranged on the conductive brush holder 4 to facilitate screwing in bolts to fix it to the motor holder 1; and a chamfer 404 is formed on the end surface edge of the conductive brush holder 4 to prevent scratching the motor holder 1 during assembly.

[0032] A lower recessed position 405 for installing the conductive brush 5 is provided at the bottom of the conductive brush holder 4. The conductive brush 5 is embedded and installed in the lower recessed position 405 and is firmly fixed. A through hole 406 is connected to the top of the lower recessed position 405 for the hollow cylindrical tube 603 of the small shaft 6 to pass through the through hole 406 for assembly, and the structure is compact.

[0033] In the present invention, the conductive brush 5 is used to effectively conduct the current between the stator and the rotor, and the current flows through the conductive brush 5 instead of the bearing 2, thereby effectively protecting the bearing 2; and a labyrinth groove is designed between the conductive brush holder 4 and the small shaft 6, which effectively reduces the motor shaft voltage while preventing the powder of the conductive brush 5 from entering the inside of the bearing 2 and contaminating the grease, thereby protecting the bearing 2 and increasing the service life of the bearing 2.

[0034] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A structure for reducing the shaft voltage of a variable frequency motor, comprising a motor base (1), a bearing (2) being arranged in the motor base (1), a motor shaft (3) being connected to the bearing (2), and characterized in that: The motor seat (1) is connected to a conductive brush seat (4) by interference fit, and the conductive brush seat (4) is connected to a conductive brush (5) by interference fit; the bearing (2) and the conductive brush (5) are respectively arranged on the upper and lower sides of the conductive brush seat (4); the conductive brush (5) comprises an aluminum alloy frame (501) and a plurality of conductive fibers (502) located on the aluminum alloy frame (501); and further comprises a small shaft (6) connected to the motor shaft (3), the small shaft (6) and the conductive brush (5) having corresponding positions and being used in matching manner; when the motor shaft (3) rotates, the contact friction between the conductive fibers (502) and the small shaft (6) causes the stator and rotor of the motor to be connected, thereby eliminating the potential difference between the surfaces of the stator and rotor; a labyrinth passage is formed between the small shaft (6) and the conductive brush seat (4) to prevent powder generated by the friction between the conductive fibers (502) and the small shaft (6) from falling into the bearing (2).

2. The structure for reducing the shaft voltage of a variable frequency motor according to claim 1, characterized in that: The labyrinth channel comprises a first labyrinth groove (601) on a small shaft (6) and a second labyrinth groove (401) on a conductive brush holder (4) assembled together; the small shaft (6) is arranged in a T shape, the first labyrinth groove (601) is opened at the lower part of both sides, and an outer edge (602) is formed on the outer side of the first labyrinth groove (601); an inner edge (402) is formed on the inner side of the second labyrinth groove (401) in the conductive brush holder (4); in an assembled state, the inner edge (402) is embedded in the first labyrinth groove (601) and a distance is maintained, and the outer edge (602) is embedded in the second labyrinth groove (401) and a distance is maintained.

3. The structure for reducing the shaft voltage of a variable frequency motor according to claim 2, characterized in that: The small shaft (6) comprises a hollow cylindrical tube (603) for connecting with the conductive fiber (502), and the center of the hollow cylindrical tube (603) is connected with a fixing hole (604); the top of the small shaft (6) is also provided with an upper recessed position (605) for assembling the motor shaft (3), and the upper recessed position (605) is connected with the fixing hole (604).

4. The structure for reducing the shaft voltage of a variable frequency motor according to claim 1, characterized in that: The conductive brush holder (4) is longitudinally provided with a disassembly screw hole (403); the end surface edge of the conductive brush holder (4) is formed with a rounded corner (404) to prevent the motor holder (1) from being scratched during assembly.

5. The structure for reducing the shaft voltage of a variable frequency motor according to claim 1, characterized in that: A lower recessed position (405) for mounting a conductive brush (5) is provided below the conductive brush holder (4), and a through hole (406) is connected above the lower recessed position (405) for the hollow cylindrical tube (603) of the small shaft (6) to pass through the through hole (406) for assembly.

6. The structure for reducing the shaft voltage of a variable frequency motor according to claim 1, characterized in that: The aluminum alloy frame (501) is in the shape of a ring with an inner wall surface; a plurality of conductive fibers (502) are distributed on the inner wall surface around the center of the aluminum alloy frame (501); and the plurality of conductive fibers (502) are located on the same plane and extend toward the direction of the small axis (6) to connect with each other.

7. The structure for reducing the shaft voltage of a variable frequency motor according to claim 2, characterized in that: The aluminum alloy frame (501) is provided with a riveting position (5011) for fixing the conductive fiber (502).

8. The structure for reducing the shaft voltage of a variable frequency motor according to claim 3, characterized in that: The aperture of the hollow cylindrical tube (603) is larger than the aperture of the fixing hole (604).

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