WO2023040241A1

WO2023040241A1 - Shaft current protection structure of variable frequency motor

Info

Publication number: WO2023040241A1
Application number: PCT/CN2022/085247
Authority: WO
Inventors: 于冰; 尤磊; 王光晨; 董小艳; 张帅; 王丁
Original assignee: 浙江中车尚驰电气有限公司
Priority date: 2021-09-15
Filing date: 2022-04-06
Publication date: 2023-03-23
Also published as: CN113949222B; CN113949222A

Abstract

Disclosed in the present invention is a shaft current protection structure of a variable frequency motor, comprising a rotating shaft and an end cover, and further comprising an inner hole provided in the rotating shaft and formed by axially extending the end portion of the rotating shaft inward; and a conductive device comprising a conductor and conductive brushes, the conductor comprising a head part and a tail part, the head part extending into the inner hole, the tail part being located on the outside, the conductive brushes being fixed with the head part, the conductive brushes being in contact with the inner wall of the inner hole, and the tail part being connected to the end cover. The rotating shaft and the end cover are connected by means of the conductive device to form a loop. According to the present invention, a conductive bypass is formed by a motor end cover, a cover plate, a conductive device, and a rotating shaft to effectively protect a bearing; meanwhile, the structure does not occupy the space of the motor, and is convenient to mount and maintain; and a hole is reserved in the rotating shaft, thereby facilitating modification of addition of the shaft current protection structure in a later stage of an existing motor.

Description

A Shaft Current Protection Structure of Variable Frequency Motor

technical field

The invention belongs to the technical field of frequency conversion motors, and more specifically relates to a shaft current protection structure of frequency conversion motors.

Background technique

Electric corrosion caused by shaft current is a common bearing failure of variable frequency motors. Due to factors such as variable frequency power supply and motor manufacturing, common mode currents and differential mode currents will be formed on the bearings when the motor is running. The method of reducing and suppressing the shaft current, in addition to adding filtering on the variable frequency power supply side to reduce the common mode voltage, the solution on the motor side is mainly from the two aspects of "blocking" and "draining". The "blocking" methods are: Insulated end caps, insulating bearings, etc. are used. The "sparse" method is to short-circuit the housing and the rotating shaft by adding grounding carbon brushes, conductive rings, auxiliary bearings, and conductive shrapnel near the bearings to form a conductive bypass with lower impedance. As a result, the shaft current is mainly released through the conductive bypass, so as to avoid electric corrosion caused by the shaft current flowing through the bearing.

In the field of new energy vehicle motor applications, due to factors such as product structure and cost, insulating end caps and insulating bearings are rarely used. The use of grounding carbon brushes or conductive rings requires additional consideration of the installation space of the motor, and it is very difficult for the motor that has already been installed. Difficult to make corrections.

At present, in the field of new energy vehicle motors, the shaft current problem is mostly treated with a conductive ring. The conductive ring conducts electricity through the conductive fiber fixed in the ring and the shaft. Compared with the ground carbon brush, the conductive fiber has good conductivity and wear resistance. , maintenance-free and other advantages, due to the large conductive ring, it will need to increase the installation space and cost inside the motor, and it is very inconvenient for the rectification of the existing motor.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a conductive bypass formed by the motor end cover, the cover plate and the conductive device and the rotating shaft to effectively protect the bearing. At the same time, this structure does not occupy the space of the motor, and is convenient for installation and maintenance. A hole is reserved on the rotating shaft, which is very convenient for the later modification of the existing motor to increase the shaft current protection structure.

In order to achieve the above object, the present invention provides the following technical solution: a shaft current protection structure of a variable frequency motor, including a rotating shaft and an end cover, and also includes:

The inner hole is arranged on the rotating shaft and is formed by extending the end of the rotating shaft axially inward;

Conductive device, which includes a conductor and a conductive brush, the conductor includes a head and a tail, the head extends into the inner hole, the tail is located outside, the conductive brush is fixed to the head, and the conductive brush contacts the inner wall of the inner hole , the tail is connected to the end cap;

The rotating shaft and the end cover are connected and conducted through the conductive device to form a loop.

Further, the end cap is provided with a conductive cover plate, and the tail is fixed on the cover plate.

Further, the cover plate is provided with a mounting boss, and the mounting boss is provided with a mounting hole for the conductor to pass through, and the tail of the conductor is provided with a mounting platform, and the plane of the mounting boss and the tail of the The mounting platform is bonded to form a conductive surface.

Further, the installation platform of the electrical conductor is connected with the installation boss of the cover plate through bolts.

Further, the electrical conductor is screwed into the mounting hole of the mounting boss.

Further, the head is rod-shaped, the conductive brush is covered on the head, and the end of the head is provided with a locking structure.

Further, there are several conductive brushes, and the several conductive brushes are sequentially sleeved on the head along the axial direction.

Further, the conductive brush includes a copper ring and a conductive fiber, one end of the conductive fiber is fixed in the copper ring, and the other end extends out of the copper ring, and the copper ring is sleeved on the head.

Further, the tail of the conductor is provided with a threaded blind hole.

Compared with the prior art, the beneficial effect of the present invention is: the motor end cover, the cover plate and the conductive device form a conductive bypass with the rotating shaft to effectively protect the bearing, and at the same time, the structure does not occupy the internal space of the motor, which is convenient for installation and maintenance , by reserving a hole on the shaft, it is very convenient to increase the shaft current protection structure transformation of the existing motor in the later stage; the conductive device specially designed by using conductive fiber can not only be adjusted according to the size of the motor, but also the conductive fiber can be adjusted according to the power of the motor. The number of conductive brushes can adjust the conductive contact area, which is very conducive to platformization and serialization.

Description of drawings

Fig. 1 is a structural schematic diagram of the shaft current protection structure of the variable frequency motor;

Figure 2 is a partial side view of the cover;

Figure 3 is a partial sectional view of the cover plate;

Figure 4 is a cross-sectional view of the conductive device;

Figure 5 is a side view of the tail of the conductor;

Fig. 6 is the sectional view of electric conductor;

Fig. 7 is the first structure side view of conductive brush;

Fig. 8 is a three-dimensional structure diagram of a copper ring;

Fig. 9 is a schematic diagram of an embodiment of the locking structure of the conductor;

Fig. 10 is a schematic diagram of another embodiment of the locking structure of the conductor;

Fig. 11 is a schematic diagram of an embodiment in which the conductor is connected and fixed to the cover plate;

Fig. 12 is the second structural cross-sectional view of the conductive brush;

Fig. 13 is a second structural side view of the conductive brush;

Fig. 14 is the three-dimensional structure diagram of the third structure of the conductive brush;

Fig. 15 is the three-dimensional structural diagram of the copper sheet in the third structure of the conductive brush;

Fig. 16 is a sectional view of the fourth structure of the conductive brush;

Fig. 17 is a three-dimensional structure diagram of the fixing seat in the fourth structure of the conductive brush;

Fig. 18 is the three-dimensional structure diagram of the pressure plate in the fourth structure of the conductive brush;

Fig. 19 is a cross-sectional view of a fifth structure of a conductive brush;

Fig. 20 is a three-dimensional structure diagram of the fixing seat in the fifth structure of the conductive brush.

Reference signs: 1, rotating shaft; 11, inner hole; 2, conductive device; 21, conductor; 211, installation platform; 212, through hole; 213, tail; 214, ring groove; 215, head; 216, thread Section; 217, threaded blind hole; 22, sealing ring; 23, conductive brush; 231, copper ring; 232, conductive fiber; 2321, external contour; 233, copper sheet; 234, locking screw; 235, groove; 2361 , pressure column; 2362, star-shaped groove; 2363, front end of pressure column; 2364, fixed plate; 2365, star-shaped column; 237, pressure plate; 3. Cover plate; 31. Mounting boss; 32. Mounting hole; 33. Threaded hole; 4. End cover.

Detailed ways

The embodiment of the present invention will be further described with reference to FIG. 1 to FIG. 20 .

In the description of the present invention, it should be noted that for orientation words, such as the terms "center", "horizontal (X)", "longitudinal (Y)", "vertical (Z)", "length", " Width", "Thickness", "Top", "Bottom", "Front", "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner ", "outside", "clockwise", "counterclockwise" and other indication orientations and positional relationships are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the Means that a device or element must have a specific orientation, be constructed and operated in a specific orientation should not be construed as limiting the specific protection scope of the present invention.

In addition, terms such as "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of technical features. Therefore, the definition of "first" and "second" features may explicitly or implicitly include one or more of these features. In the description of the present invention, the meanings of "several" and "several" are two or two above, unless otherwise expressly and specifically defined.

A shaft current protection structure for a variable frequency motor, including a rotating shaft 1 and an end cover 4, and also includes: an inner hole 11, which is arranged on the rotating shaft 1 and is formed by extending the end of the rotating shaft 1 axially inward;

Conductive device 2, it comprises conductor 21 and conductive brush 23, and described conductor 21 comprises head 215 and tail 213, and head 215 stretches in the inner hole 11, and tail 213 is positioned at outside, and described conductive brush 23 and head The part 215 is fixed, the conductive brush 23 contacts the inner wall of the inner hole 11, and the tail part 213 is connected with the end cap 4;

The rotating shaft 1 and the end cover 4 are connected and conducted through the conductive device 2 to form a circuit.

Generally, the opening of the end cover 4 is relatively large. In this embodiment, a conductive cover plate 3 can be fixed on the end cover 4, and the tail portion 213 of the conductive device 2 is fixed with the cover plate 3, that is, the rotating shaft 1 and the end cover 4 pass through. The conductive device 2 and the cover plate 3 are connected to form a loop. The impedance of this loop is much smaller than that of the bearing oil film. When there is shaft voltage on both sides of the bearing oil film, the shaft current is released through this loop, thereby protecting the bearing from shaft current. corrosion.

Usually, the length of the head 215 of the conductive device 2 protruding into the inner hole 11 is smaller than the depth of the inner hole 11 .

As shown in Figure 3, the preferred cover plate 3 in this embodiment is provided with a mounting boss 31, and the mounting boss 31 is provided with a mounting hole 32 for the conductor 21 to pass through, and the tail of the conductor 21 213 is provided with a mounting platform 211 , and the plane of the mounting boss 31 is attached to the mounting platform 211 of the tail 213 to form a conductive surface, and the conductive surface is used to conduct the conductor 21 and the cover plate 3 .

Usually, the mounting hole 32 is a circular inner hole 11, and the tail portion 213 of the conductor 21 corresponds to a cylindrical shape. Of course, the mounting hole 32 and the conductor 21 can also be of other shapes, as long as the two are the same and can be bonded together. , in the following embodiments, the installation hole 32 is a circle, and the conductor 21 is a cylinder as an example. At the joint between the installation hole 32 and the conductor 21, a small gap is used to fit and install between the two.

In one embodiment, the installation platform 211 of the electrical conductor 21 is connected to the installation boss 31 of the cover plate 3 through bolts, as shown in FIG. 2 and FIG. One or more threaded holes 33, which can be through holes 212 or blind holes, and open through holes 212 at the installation platform 211 of the conductor 21, pass through the installation platform 211 of the conductor 21 and the cover plate 3 in turn by bolts The threaded hole 33 fixes the conductor 21 on the cover plate 3; and in this embodiment, a sealing ring 22 is provided between the cylindrical surface of the conductor 21 and the mounting hole 32, specifically on the cylindrical surface of the conductor 21 An annular groove 214 is provided, and the sealing ring 22 is placed in the annular groove 214 .

In another embodiment, the electrical conductor 21 is threadedly connected to the mounting hole 32 of the mounting boss 31, specifically as shown in FIG. There is an external thread on the top, and the two are fixedly connected by threads. Preferably, the installation platform 211 of the conductor 21 is polygonal at this time, so as to facilitate the use of tools to screw the conductor 21; A sealing ring 22 is provided between the installation platform 211 of 21 and the installation boss 31 of the cover plate 3 .

In this embodiment, the head 215 is specifically in the shape of a rod, the conductive brush 23 is sleeved on the head 215 , and the end of the head 215 is provided with a locking structure.

In the present invention, the head 215 can be cylindrical or polygonal, and the shape of the conductive brush 23 matches it so that the conductive brush 23 can be placed on the head 215 and be stable. In the following embodiments, the head 215 is used as the Cylindrical, that is, a cylindrical segment is formed here, and the middle of the conductive brush 23 is a round hole as an example.

Described conductive brush 23 is provided with several, and several conductive brushes 23 are sleeved on the head 215 successively along the axial direction, and the size of conductive device 2 can be selected according to the size of the motor, and at the same time, according to the different power of the motor, the power of the conductor 21 can be adjusted. The length of the head 215 and the number of conductive brushes 23 increase the contact area between the conductive brushes 23 and the inner wall of the inner hole 11 of the rotating shaft 1. In the present invention, the conductor 21 is made of aluminum or tinned copper.

In one of the embodiments, the locking structure is shown in Figure 4 and Figure 6, there is a threaded section 216 at the end of the head 215 of the conductor 21, and a hexagonal flange nut 24 for locking is provided on the threaded section 216, Now the thickness of all conductive brushes 23 is slightly greater than the length of the head 215 cylindrical section of the conductor 21, and the total thickness of the conductive brush 23 is usually 0.2-1mm longer than the head 215 cylindrical section of the conductor 21. It should be noted that The length of the threaded section 216 of the head 215 of the conductor 21 is not included in the length of its cylindrical section. When assembling, all the conductive brushes 23 are placed on the cylindrical section in turn, and then the hexagonal flange nut 24 and the conductor 21 are connected. The threaded section 216 is tightened and fixed.

In another embodiment, the locking structure is as shown in FIG. 9, at this time, the head 215 of the conductor 21 has no threaded section 216, but has a hollow hole at its end, and when all the conductive brushes 23 are fixed, pass In the way of interference riveting, the end of the head 215 of the conductor 21 is turned outward to fix the conductive brush 23, that is, the change process from A1 to A2 in FIG. 9 .

In another embodiment, the locking structure is as shown in FIG. 10. At this time, the head 215 of the conductor 21 has no threaded section 216, but uses a section rivet at its end to fix all the conductive brushes 23, that is, The change process from B1 to B2 in Figure 10.

As shown in Fig. 7 and Fig. 8, what it shows is the first structure of conductive brush 23 in the present invention, described conductive brush 23 comprises copper ring 231 and conductive fiber 232 in this structure, and one end of described conductive fiber 232 It is fixed in the copper ring 231 , and the other end protrudes out of the copper ring 231 , and the copper ring 231 is sleeved on the head 215 .

The specific copper ring 231 is in a cylindrical shape. Figure 8 shows the initial structural state of the copper ring 231. The conductive fiber 232 is filled inside it, and the protruding lengths of both ends are controlled to be approximately the same. The ring 231 is preformed flat and compressed, so that all the conductive fibers 232 are compressed and fixed in the copper ring 231, and then the hole 2311 of the copper ring 231 is processed, the hole of the copper ring 231 and the cylindrical section of the head 215 of the conductor 21 For small transitional fit, trim the outer contour of the conductive fiber 232 with tooling, so that the outer contour arc diameter 2312 of the conductive fiber 232 is 1-3 mm larger than the inner hole 11 of the rotating shaft 1, and complete the production of the conductive brush 23; after the preferred crimping is formed The maximum arc diameter of the copper ring 231 is 2-4 mm smaller than the inner hole 11 of the rotating shaft 1 .

As shown in Figure 12 and Figure 13, what it shows is the second structure of the conductive brush 23 in the present invention, in this structure, the conductive brush 23 includes two copper sheets 233 and conductive fibers 232 in this embodiment, The conductive fiber 232 is located between the two copper sheets 233, and a locking screw 234 is arranged between the two copper sheets 233, that is, the two copper sheets 233 are fixed by the locking screw 234, and the conductive fiber 232 is clamped and fixed between the two copper sheets 233. Between copper sheets 233.

Wherein the locking screw 234 is preferably a hollow rivet, and its end does not protrude to the outside of the copper sheet 233 .

As shown in Figure 14 and Figure 15, what it shows is the third structure of the conductive brush 23 in the present invention, in this structure, the conductive brush 23 includes two copper sheets 233 and conductive fibers 232, and the copper sheet 233 is provided with There are radially arranged grooves 235, conductive fibers 232 are located in the grooves 235, locking screws 234 are arranged between the two copper sheets 233, and the two copper sheets 233 are locked by the locking screws 234, and the conductive fibers 232 is fixed in the groove 235, and preferably there are four grooves 235, and they are evenly distributed along the circumference. At this time, the locking screw 234 can be a solid rivet, and its end does not protrude from the groove 235.

As shown in Fig. 16, Fig. 17 and Fig. 18, what it shows is the fourth structure of conductive brush 23 in the present invention, in this structure, conductive brush 23 comprises fixed seat, pressing plate 237 and conductive fiber 232, fixed seat It includes a fixed plate 2364, a star-shaped column 2365 and a pressure column 2361, one side of the star-shaped column 2365 and the pressure column 2361 are fixed to the fixed plate 2364, and the pressure column 2361 is located in the star-shaped groove 2362 of the star-shaped column 2365, There is an installation space between the pressure column 2361 and the star-shaped groove 2362, the length of the pressure column 2361 is greater than the length of the star-shaped column 2365, the middle of the conductive fiber 232 is located in the star-shaped groove 2362, and the two ends of the conductive fiber 232 are formed by star-shaped The slot 2362 protrudes, and the pressing plate 237 is provided with a shaped hole 2371 for the pressing column 2361 to pass through.

The pressing plate 237 has the same outer diameter as the fixing plate 2364 .

Preferably, a counterbore 2373 is provided on the pressing plate 237 corresponding to the shaped hole 2371 , and the counterbore 2373 is used to accommodate the riveted end of the pressing post 2361 .

Preferably, the star-shaped groove 2362 is V-shaped or U-shaped corresponding to the groove formed between the pressing post 2361 and the star-shaped post 2365 .

Preferably, the cross section of the pressure column 2361 is triangular, and the shaped hole 2371 is a triangular hole.

Preferably, the pressure column 2361 has anti-slip ribs extending radially towards the inner side of the star-shaped groove 2362 .

As shown in Fig. 19 and Fig. 20, what it shows is the fifth structure of the conductive brush 23 in the present invention, which is improved from the fourth structure of the conductive brush 23, and the pressing plate 237 it adopts is the same as that in Fig. In this structure, the outer surfaces of the star-shaped column 2365 and the pressure column 2361 are flush with the largest outer surface of the fixed plate 2364, and a step is provided at the front end 2363 of the pressure column, that is, the end of the pressure column 2361 facing the pressure plate 237, so as to The outer surface of the front end 2363 of the pressing column is not flush with the largest outer circular surface of the fixing plate 2364 so that it can smoothly penetrate into the shaped hole 2371 of the pressing plate 237 .

In this way, after the conductive fiber 232 is fixed, when it is in contact with the inner hole 11 of the rotating shaft 1, the conductive fiber 232 rebounds more easily, and the conductive effect will not be affected by the rebound due to too long length.

The fourth and fifth structural installation methods of the conductive brush 23 in the present invention are as follows, the conductive fibers 232 are put into all the star-shaped grooves 2362 in turn, and both ends thereof protrude out of the star-shaped grooves 2362, Then utilize pressing plate 237 to fix again, make the front end 2363 of all pressing columns pass through the shaping hole 2371 of pressing plate 237, pressing plate 237 squeezes and compresses the conductive fiber 232 in the star-shaped groove 2362, makes the front end of pressing column by press or other tools 2363 is riveted on the pressing plate 237, and the front end 2363 of the riveted pressing column fills up the counterbore 2373.

In the present invention, the tail portion 213 of the conductor 21 is provided with a threaded blind hole 217, and the threaded blind hole 217 is formed by extending the end of the tail portion 213 of the conductor 21 to the inside, so that the conductive device 2 can be pulled out when it is disassembled. To disassemble the conductive device 2, a tool with a screw can be screwed into the threaded blind hole 217 to pull out the entire conductive device 2. At the same time, the threaded blind hole 217 is used to install the grounding wire, which is more conducive to the release of the shaft current and protects the bearing. .

The above descriptions are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims

A shaft current protection structure of a variable frequency motor, including a rotating shaft and an end cover, is characterized in that it also includes:

The inner hole is arranged on the rotating shaft and is formed by extending the end of the rotating shaft inward in the axial direction; the conductive device includes a conductor and a conductive brush, the conductor includes a head and a tail, and the head extends into the inside In the hole, the tail is located on the outside, the conductive brush is fixed to the head, the conductive brush contacts the inner wall of the inner hole, and the tail is connected to the end cover;

The rotating shaft and the end cover are connected and conducted through the conductive device to form a loop.
The shaft current protection structure of the variable frequency motor according to claim 1, characterized in that: the end cover is provided with a conductive cover plate, and the tail is fixed on the cover plate.
The shaft current protection structure of variable frequency motor according to claim 2, characterized in that: the cover plate is provided with a mounting boss, and the mounting boss is provided with a mounting hole for the conductor to pass through, and the tail of the conductor A mounting platform is provided at the position, and the plane of the mounting boss fits with the mounting platform at the tail to form a conductive surface.
The shaft current protection structure of the variable frequency motor according to claim 3, characterized in that: the mounting platform of the electrical conductor is connected to the mounting boss of the cover plate through bolts.
The shaft current protection structure of the variable frequency motor according to claim 3, characterized in that: the conductor is screwed to the mounting hole of the mounting boss.
The shaft current protection structure of the variable frequency motor according to claim 4 or 5, characterized in that: the head is rod-shaped, the conductive brush is covered on the head, and the end of the head is provided with a locking structure.
The shaft current protection structure of the variable frequency motor according to claim 6, characterized in that: there are several conductive brushes, and the several conductive brushes are sequentially sleeved on the head along the axial direction.
The shaft current protection structure of variable frequency motor according to claim 7, characterized in that: the conductive brush includes a copper ring and a conductive fiber, one end of the conductive fiber is fixed in the copper ring, and the other end extends out of the copper ring, so The copper ring is set on the head.
The shaft current protection structure of the variable frequency motor according to claim 8, characterized in that: a threaded blind hole is arranged on the tail of the conductor.