JP2010166748A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor that is improved in cooling performance for a bearing section and is reduced in electric corrosion in the bearing section. <P>SOLUTION: In a motor, a cylindrical frame is provided on the outer diameter section of a stator and a driven side bracket and a non-driven side bracket are provided on both sides of the frame, and a driven side bearing and a non-driven side bearing are provided in a central portion of each of the brackets to support a shaft 4 provided at the center of a rotor, and in either or both of the bearings, for example, in a load side bearing 7, a bearing cover 9 fixed to the bracket is provided inside the machine, to fix the bearings in the thrust direction or to allow the bearing boxes in hermetic structure. In the motor, a carbon fiber packing 11 is provided which comes into contact with both the bearing cover 9 of either or both of the bearing boxes and the shaft 4 to achieve the hermeticity of the bearing boxes, and a heat dissipation path and a discharging path are formed to allow heat and charges generated in the rotor to be released outside via the shaft 4, carbon fiber packing 11, bearing covers 9, brackets 5, and frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric motor, and is particularly suitable for a fully enclosed external fan motor.

  There is known an electric motor having a structure in which a shaft fixed to a rotor is supported by a bearing and the rotational force of the shaft is transmitted to the outside (see Patent Document 1). Patent Document 2 discloses a configuration in which axial current is prevented by using grease mixed with conductive powder in the vicinity of the bearing in place of the ground brush. Patent Document 3 discloses an electric motor using a rolling bearing (see FIG. 2), and shows an example in which a discharge path is formed between an inner ring and an outer ring of a bearing (see FIG. 1).

JP 2008-148367 A Microfilm of actual application No. 50-95436 (No. 52-9005) Japanese Unexamined Patent Publication No. 2007-146966

  Some motors require heat dissipation because they generate heat during operation. In particular, since the rotor conductor serves as a heating element, part of the heat generated here follows a heat dissipation path that passes through the shaft and bearings to the frame. If the cooling performance is not sufficient, the lubricating grease on the bearing will deteriorate due to heat, shorten the service life, and require maintenance efforts such as grease replacement.

  There are two types of motor cooling methods: an open type that takes in cooling air from the outside and cools the inside of the motor, and a fully closed type that does not take cooling air into the motor. Generally, the fully closed type is inferior to the open type in that the cooling performance is inferior, and thus the cooling performance needs to be improved. In particular, since the lubricating grease is deteriorated by heat, it is important to improve the cooling performance of the bearing portion.

  In the conventional electric motor, a part of the heat generated in the rotor is guided to the end bracket and the frame via a shaft fixed to the rotor and a bearing supporting the shaft. The electric motor of Patent Document 1 stirs the heat in the frame by the inner fan fan and promotes heat radiation from the frame by the outer fan fan. However, the heat radiation path from the rotor as the heating element to the frame is considered. It was not.

  In addition, since electric charges generated in the rotor cause a potential difference between the shaft side and the end bracket side, electrolytic corrosion of the bearing portion is a problem.

  In Patent Document 2, a conductive powder is mixed in grease to energize the shaft side and the end bracket side. In Patent Document 3, a non-contact discharge brush made of carbon fiber or stainless fiber is provided between the bearings. This suppresses excessive charge accumulation.

  However, no consideration is given to heat dissipation, and it does not solve the shortening of life due to deterioration of grease. Therefore, the bearing grease may be deteriorated due to heat, the bearing life may be shortened, and the bearing may be damaged due to electric corrosion.

  The present invention has been made in view of the above problems, and has an object to provide an electric motor that reduces a thermal or electrical load generated in a bearing portion, reduces maintenance labor, and extends a service life. Yes.

  In order to solve the above-described problems, the present invention adopts a configuration in which heat dissipation and discharge paths that do not pass through the bearing are obtained, and the burden on the bearing is suppressed. Specific embodiments of the present invention are as follows.

  That is, a cylindrical frame, a stator provided in the center of the frame in the thrust direction, brackets covering the openings on both sides of the frame, a shaft in the center, and disposed inside the stator. A rotor, a bearing that supports the shaft and is held by the bracket, a bearing cover that is attached between the bearing and the rotor, and a carbon fiber packing that contacts both the bearing cover and the shaft. It was set as the electric motor provided with.

In the above configuration, more preferable specific embodiments are as follows.
(1) The space separated by the bearing cover and the carbon fiber packing is a sealed space, and the bearing is disposed in the sealed space.
(2) A second bearing cover is provided on the opposite side of the bearing cover across the bearing.
(3) The carbon fiber packing is disposed so as to contact both the bracket and the shaft.
(4) A bearing is disposed in a space separated by the bearing cover and the carbon fiber packing, and includes a grease inlet and a grease discharge port that open in communication with the space.
(5) An outer fan that rotates with the rotation of the shaft is provided on the opposite side of the load to the opposite side of the bearing across the rotor.

  ADVANTAGE OF THE INVENTION According to this invention, the electric or electric load which generate | occur | produces in a bearing part can be reduced, and the electric motor which aimed at reduction of a maintenance labor and lifetime improvement can be provided.

  In this embodiment, a cylindrical frame is provided on the outer diameter portion of the stator, and a drive side bracket and a counter drive side bracket are provided on both sides thereof. A shaft 4 having a rotor is provided at the center of each bracket. It is premised on an example in which a drive-side bearing and a counter-drive-side bearing are provided to support the shaft.

  Then, in order to fix the bearing in the thrust direction or to make the bearing box (described later) a sealed structure, either or both of the bearings, for example, the load side bearing 7 is fixed to the bracket inside the machine. A bearing cover 9 is provided.

  The feature is to provide a carbon fiber packing 11 in contact with both the bearing cover 9 and the shaft 4 of one or both of the bearing boxes to obtain the sealability of the bearing box and to generate in the rotor. The heat and electric charge to be discharged through the shaft 4, the carbon fiber packing 11, and the bearing cover 9 to the outside through the housing are formed as a heat dissipation path and a discharge path.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall sectional view of an electric motor according to an embodiment of the present invention. 1 and 2 show an enlarged view of the bearing portion, FIG. 3 shows a flow path of the replaceable grease, and FIG. 4 shows a secondary side heat generation, heat release and discharge path. 1, 2 and 4 show the upper half of the rotation axis. An example of the motor is a fully-enclosed fan motor that is often used as a motor for general industries.

  In FIG. 1, the stator 2 of the electric motor is arranged with a space on both sides in the longitudinal direction with respect to a cylindrical frame 1 provided on the outer diameter portion. Further, one side in the longitudinal direction of the cylindrical frame 1 is a load side and the other side is an anti-load side, and an output shaft for outputting the rotational force of the shaft 4 to the outside is provided on the load side. A load side bracket 5 having a load side bearing 7 at the center is provided on the load side, and an antiload side bracket 6 having an antiload side bearing 8 at the center is provided on the antiload side. The frame 1, the load side bracket 5 and the anti-load side bracket 6 constitute the casing of the fully-enclosed external fan motor of the present embodiment, and as shown below, the main motors such as the stator 2 are used. A configuration is disposed within the housing.

  Inside the stator 2, a rotor 3 having a shaft 4 on its inner diameter is arranged. The shaft 4 is loaded on the load side by a load-side bearing 7 and on the non-load side by an anti-load side bearing 8. It is supported. The load side bracket 5 and the anti-load side bracket 6 have an internal space on the load side in order to fix the thrust direction of the load side bearing 7 and the anti load side bearing 8 and to make a sealed structure around the bearing. An internal bearing cover 9 and an anti-load side internal bearing cover 10 are provided.

  As described above, the load side 4a of the shaft 4 serves as an output shaft, and is connected to an external load by coupling directly or by belting or the like to output rotational energy. Further, an outer fan 13 is attached to the non-load side 4b of the shaft 4 for air cooling of the motor, and the motor housing such as the frame 1 is cooled by cooling air generated by the outer fan 13. In the case of a double-shaft motor, the anti-load side 4b of the shaft 4 extends to the end of the outer fan 13 and the end cover 14, and is connected to an external load and output, like the load side 4a.

  An example in which grease for lubrication is used for the bearings 7 and 8 that support the shaft 4 is known. When a grease exchange type is used on both the load side and the non-load side of the bearing, or one of them, it is necessary to form a grease flow path.

  FIG. 2 is an enlarged view of the bearing portion. In this embodiment, in order to form a grease flow path around the load side bearing 7, a load side internal bearing cover 9 that separates the load side bearing 7 from the motor internal space is provided on the rotor 3 side of the load side bracket 5. Similarly, a load side external bearing cover 17 is provided on the outer space side of the load side bracket 5. Therefore, a closed space is formed around the load side bearing 7 by the load side bracket 5, the load side inner bearing cover 9, and the load side outer bearing cover 17. Hereinafter, in the description of the present embodiment, this closed space is referred to as a “load-side bearing box” or simply a “bearing box”. In addition, the case where either the load side bearing inner cover 9 or the load side bearing outer cover 17 is integrated with the load side bracket 5 is included.

  Next, a configuration for replacing grease for bearing lubrication will be described with reference to FIG. In this embodiment, a grease inlet 15 for supplying grease is provided. The position of the grease inlet 15 is not limited as long as it communicates with the inside of the load-side bearing box. However, it is preferable to provide the grease inlet 15 at the outer peripheral portion of the motor housing in consideration of easy supply.

  When replacing the grease, the grease that has entered from the load side grease inlet 15 passes through the load side grease passage 15a that connects the load side grease inlet 15 and the load side bearing 7, and as shown by the arrow in FIG. The bearing 7 is guided to the inside of the motor, guided by the load-side bearing inner cover 9, and passes through the load-side bearing 7. The grease that has passed through the load side bearing 7 is guided by the load side bearing outer cover 17 and discharged from the load side grease discharge port 19. The load-side grease discharge port 19 can be placed in any position as long as the grease that has passed through the load-side bearing 7 is discharged to the outside. When arranged above the bearing 7, it is desirable that the load-side grease discharge port 19 be disposed below the load-side bearing 7.

  Since the load side inner cover 9 and the shaft 4 are not in contact with each other, it is necessary to prevent the grease from leaking into the motor internal space from this gap. Therefore, a load side bearing box packing 11 is provided between the load side inner cover 9 and the shaft 4 so as to be in contact with both.

  Although the description on the non-load side is omitted, the grease replacement type has the same structure as the load side.

  In the above-described configuration, the causes of deterioration of the bearing (particularly the load-side bearing 7) can be broadly classified into those caused by heat generation of the electric motor and those caused by electric charge. Hereinafter, the structure of bearing protection will be described.

  First, the heat dissipation structure in the electric motor of the present embodiment will be described first. An electric motor generates heat during operation, and a main cause of heat generation is loss during operation. Loss when operating the motor includes copper loss, iron loss, mechanical loss, stray load loss, but copper loss is mainly the primary copper loss generated in the stator coil 2a, the rotor conductor 3b and the rotor end ring 3c. Due to secondary copper loss.

  The heat generated by the primary copper loss in the stator coil 2a is dominated by the heat radiation path that conducts heat to the frame 1, the heat radiation fin 20, and the outside air through the stator 2. Heat generated by secondary copper loss in the rotor conductor 3b and the rotor end ring 3c is conducted to the inside air of the motor internal space by the inner fan 3a provided at both ends of the rotor 3, and is conducted from the inside air to the frame 1. While there is a heat dissipation path, if the thermal conductivity of the inside air is smaller than that of the shaft 4, there is a heat dissipation path that conducts heat from the rotor 3 through the shaft 4 to the bearings 7, 8, brackets 5, 6, and the frame 1. To do.

  In this way, the temperature of the bearing rises due to heat conduction due to secondary copper loss in addition to heat generation due to mechanical loss during rotation. In particular, when the outer fan 13 is disposed on the side opposite to the load as in the present embodiment, the temperature rise of the load side bearing 7 may become significant. As the temperature of the bearing increases, the deterioration of the grease is accelerated, and not only the maintenance cost is increased by shortening the grease replacement period, but also the life of the bearing itself is shortened.

  Therefore, in this embodiment, paying attention to the heat dissipation path of the secondary copper loss via the shaft 4, heat is generated from the bearing 7 in the path from the rotor 3 as a heating element to the load side bracket 5 and the frame 1 via the shaft 4. In addition to the bearing 7, a path for transferring heat to the bracket side is formed on the side close to the body. Specifically, a carbon fiber packing is used as the bearing box packing 11 provided for sealing the bearing box as described above, thereby improving the thermal conductivity.

  FIG. 4 is a diagram showing a heat radiation path in the secondary side heat generation. As shown in FIG. 4, the heat generated by the secondary copper loss passes through the load-side bearing housing packing 11 disposed on the rotor 3 side of the load-side bearing 7 and heats to the load-side bearing cover 9, the load-side bracket 5, and the frame 1. Form a heat dissipation path to conduct. Radiation fins 20 are formed on the surface of the frame 1, thereby improving the cooling efficiency.

  With this configuration, not only the maintenance cost can be reduced by extending the grease replacement cycle, but also the life of the load side bearing 7 can be extended. In the above description, the load-side bearing 7 is taken as an example, but the same configuration can be adopted on the anti-load side.

  Second, protection of bearing deterioration due to electric charges will be described. The electric charge generated in the rotor 3 during operation of the electric motor takes a discharge path that conducts to the load side bracket 5 or the anti-load side bracket 6, the frame 1, and the ground via the shaft 4. When charge moves from the shaft 4 to the load side bracket 5 or the anti-load side bracket 6, the load side bearing 7 or the anti-load side bearing 8 arranged between the shaft 4 and the load side bracket 5 or the anti load side bracket 6 There is a possibility that electric current flows, and electric corrosion occurs on the contact surface of the bearing rolling conductor.

  When electric corrosion occurs on the bearing, there is a risk that the life of the bearing is significantly shortened due to damage to the contact surface of the bearing rolling conductor. In order to prevent the electric corrosion of the bearing, a material having higher electrical conductivity than the bearing may be present between the shaft 4 and the load side bracket 5 or the anti-load side bracket 6. Therefore, in the same manner as described above, the load side bearing box packing 11 or the anti-load side bearing box packing 12 is made of carbon fiber-based packing, so that the packing itself has electric conductivity, and the shaft to the bracket is more conductive than the bearing. By forming a high discharge path, the electric corrosion of the bearing is prevented.

  The above is summarized as follows. Conventionally, heat generated in the rotor 3 during operation passes through the load bearing 7 (and / or the anti-load bearing 8) via the shaft 4 and is radiated to the bracket, the frame 1, and the outside air. This promotes thermal degradation of the grease on the bearing, leading to a reduction in grease replacement cycle and bearing life.

  Similarly, when an electric charge is generated during operation in the rotor 3, since it passes through the load side bearing 7 and the anti-load side bearing 8 via the shaft 4 and is discharged to the bracket, frame, and ground, the bearing rolling element There is a problem that an electrical decoration is generated on the contact surface of this and the bearing life is remarkably shortened.

  As a means to solve both of these problems, the heat conductivity in the bearing box packing portion is made by using carbon fiber packing as the material of either or both of the load side bearing box packing 11 and the anti-load side bearing box packing 12. And improvement in electrical conductivity are obtained. As a result, in the process in which heat and charges generated in the rotor 3 are radiated and discharged to the outside through the shaft 4, the heat and charges are on the rotor side with respect to the bearing by taking a path as shown in FIG. Since it passes through the carbon fiber bearing box packing, the burden on the bearing can be reduced.

  That is, the electric motor of the present embodiment includes a stator 2, a cylindrical frame 1 provided on the outer diameter portion of the stator 2, and a rotor having a shaft 4 at the center and disposed inside the stator 2. 3, two brackets 5 and 6 that block the openings at both ends of the frame 1, two bearings 7 and 8 that are supported at the center of the brackets 5 and 6 by supporting the shaft 4, and the thrust direction of the bearings Bearing cover 9 fixed to a bracket arranged on the inner side of one or both bearings for securing or bearing housing to have a sealed structure, in order to obtain the sealability of the bearing housing and heat conduction In order to obtain high performance and electrical conductivity, it is equipped with a carbon fiber packing 11 provided so as to come into contact with both the bearing cover 9 and the shaft 4, and the shaft 4, the carbon fiber packing 11, the bearing cover 9, the bracket 5, The heat dissipation and discharge paths in the order of frame 1 are configured.

  In order to obtain the sealability of the bearing housing, the carbon fiber packing 11 may be provided so as to contact both the bracket 5 and the shaft 4 arranged on the inner side of the bearing 7.

  Also, in the case of an electric motor that is not a grease exchange type, the carbon fiber is in contact with both the bracket 5 or the bearing cover 9 and the shaft 4 disposed inside the bearing 7 in order to obtain the above heat dissipation and discharge paths. A system packing 11 may be provided.

  According to this configuration, the carbon fiber-based packing 11 (12) provided between the bearing cover 9 (10) provided on the inner side of the bearing 7 (8) supporting the shaft 4 and the shaft 4 so as to contact both. ), The heat and charge generated in the rotor 3 are transferred to the rotor 3, shaft 4, carbon fiber packing 11 (12), bearing cover 9 (10), bracket 5 (6), and frame 1. Since heat is dissipated and discharged without going through 7 (8), it is possible to improve the cooling performance of the bearing and prevent electrolytic corrosion.

  Therefore, it is possible to provide an electric motor that reduces a thermal or electrical load generated in the bearing portion, reduces maintenance labor, and extends the service life.

Sectional drawing of the electric motor which is an Example of this invention. The enlarged view of a bearing part. The figure which shows a grease flow path. The figure which shows a thermal radiation and a discharge path.

  DESCRIPTION OF SYMBOLS 1 ... Frame, 2 ... Stator, 2a ... Stator coil, 3 ... Rotor, 3a ... Inner fan, 3b ... Rotor conductor, 3c ... Rotor end ring, 4 ... Shaft, 4a ... Load side, 4b ... Opposite Load side, 5 ... Load side bracket, 6 ... Anti load side bracket, 7 ... Load side bearing, 8 ... Anti load side bearing, 9 ... Load side internal bearing cover, 10 ... Anti load side internal bearing cover, 11 ... Load side Bearing box packing, 12 ... Anti-load side bearing box packing, 13 ... Outer fan, 14 ... End cover, 15 ... Load-side grease inlet, 15a ... Load-side grease flow path, 16 ... Anti-load-side grease inlet, 16a ... Anti-load Side grease flow path, 17 ... load side external bearing cover, 18 ... anti-load side external bearing cover, 19 ... load side grease discharge port, 20 ... radiating fin.

Claims (6)

  A cylindrical frame, a stator provided inside the center of the frame in the thrust direction, brackets that cover openings on both sides of the frame, and a rotation that has a shaft in the center and is arranged inside the stator. A bearing that is supported on the bracket by supporting the shaft, a bearing cover that is attached between the bearing and the rotor, and a carbon fiber packing that contacts both the bearing cover and the shaft. Electric motor provided.   2. The electric motor according to claim 1, wherein the space separated by the bearing cover and the carbon fiber packing is a sealed space, and the bearing is disposed in the sealed space.   The electric motor according to claim 1, further comprising a second bearing cover on a side opposite to the bearing cover with the bearing interposed therebetween.   4. The electric motor according to claim 3, wherein the carbon fiber packing is disposed so as to contact both the bracket and the shaft.   5. The electric motor according to claim 1, wherein a bearing is disposed in a space separated by the bearing cover and the carbon fiber packing, and includes a grease inlet and a grease discharge port that open in communication with the space. Electric motor.   5. The electric motor according to claim 1, further comprising an outer fan that rotates with the rotation of the shaft on a side opposite to the bearing across the rotor.

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