JP2014176111A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor capable of preventing electric corrosion.SOLUTION: A rotor 10 is rotated around a predetermined axis. An armature core 21 opposes the rotor 10 at a side opposite to the axis with respect to the rotor 10. A winding 22 is attached to the armature core 21. A shaft 30 is fixed to the rotor 10. A bearing 4a includes an inner ring 43 and an outer ring 41 supporting the shaft 30. A bracket 5a fixes the outer ring 41. A support member 6a includes an inner shell 61, an outer shell 62, a vine-winding spring 63a and a coating material 64. The inner shell 61 holds the bracket 5a with the outer ring 41. The vane-winding spring 63a is provided between the outer shell 62 and the inner shell 61 and conducts both the shells. The coating material 64 is provided between the inner shell 61 and the outer shell 62 and molds the vane-winding spring 63a.

Description

  The present invention relates to an electric motor, and more particularly to a technique for suppressing electric corrosion of a bearing.

  In recent years, inverter-driven motors have become widespread as high-efficiency motors. Also, the switching frequency tends to increase due to high efficiency. Therefore, a potential difference is generated by electrostatic capacitance (hereinafter also referred to as stray capacitance) that is excited by the high frequency of the inverter and parasitic between the inner ring and the outer ring of the motor bearing.

  When this potential difference is large, the oil film insulation of the lubricating grease of the bearing is broken and a discharge phenomenon occurs inside the bearing. That is, a discharge phenomenon occurs between the inner ring of the bearing and the rolling element (roller or ball) and between the rolling element and the outer ring.

  As a result, damage (so-called “electric corrosion”) due to electric discharge occurs on the rolling surfaces of the inner ring and the outer ring (surfaces in contact with the rolling elements) and the surface of the rolling elements. Noise is generated during motor operation due to distortion on the rolling surface or the surface of the rolling element.

  In order to suppress such electric corrosion, Patent Document 1 includes a contact plate and a sliding disk that elastically contacts the contact plate and rotates together with the rotating shaft, in addition to the shield bearing. The contact plate is made of a conductive material such as spring steel and has elasticity. The sliding disk is made of a conductive material such as copper or aluminum.

  In Patent Document 1, such a configuration prevents current from flowing through the rotating shaft, the contact plate, and the sliding disk, and prevents current from flowing through the shield bearing.

  Moreover, in patent document 2, when attaching a motor housing | casing to an installation frame, a pair of attachment plate which pinched | interposed the ring-shaped elastic member between both is used. The ring-shaped elastic member and the pair of mounting plates are made of a conductive material, and a conductive paint is applied to the inner surface of the ring-shaped elastic member so that the pair of mounting plates are electrically connected.

  In addition, Patent Documents 3 and 4 are listed as related to the present application.

Japanese Utility Model Publication No. 58-78769 JP 2011-120408 A JP 2008-263698 A JP 2012-191734 A

  However, in the technique described in Patent Document 1, although the contact plate and the sliding disk are in elastic contact, they do not have a function of not transmitting the vibration of the rotating shaft to the outside.

  In the technique described in Patent Document 2, the motor casing is fixed to the installation frame while conducting, and vibration noise is reduced. However, referring to the diagram of Patent Document 2, it is effective to reduce the vibration in the extending direction of the rotating shaft, but it is not effective for the vibration in the direction orthogonal to the rotating shaft. This is because the ring-shaped elastic member is interposed between the motor housing and the installation frame in the extending direction of the rotating shaft. Normally, it is considered that the vibration of the rotating shaft is mainly caused by the contact, but the structure of Patent Document 2 still has room for improvement in the effect of suppressing the vibration of the rotating shaft.

  Moreover, if it is going to conduct | electrically_connect the inner ring | wheel and outer ring | wheel of a bearing using the electrically conductive coating described in patent document 2, the new structure which provided the surface for the application | coating will be requested | required of a bearing.

  Then, an object of this invention is to provide the electric motor which suppresses transmitting the vibration of a shaft to the exterior while suppressing the electric corrosion of a bearing.

  A first aspect of an electric motor (100) according to the present invention includes a rotor (10) rotating around a predetermined axis (P), and the rotor facing the rotor on a side opposite to the axis. An armature core (21) having a winding (22) attached to the armature core, a conductive shaft (30) fixed to the rotor, and the shaft. A bearing (4a, 4b) having an inner ring (43) and an outer ring (41) to be supported, a bracket (5a, 5b) that is connected to the armature core and fixes the outer ring, and an inner that sandwiches the bracket together with the outer ring An outer shell (61), an outer shell (62), a conductive elastic body (63a, 63b) provided between the inner shell and the outer shell to connect the inner shell and the outer shell, the inner shell and the outer shell The elastic body is molded between The support member (6a, 6b) having elastic certain coating material (64) and a.

  A second aspect of the electric motor according to the present invention is the first aspect, and at least one of a helical spring (63a) and a leaf spring (63b) is employed as the elastic body.

  A third aspect of the electric motor according to the present invention is the first aspect or the second aspect, and at least one of resin and rubber is employed for the covering material (64).

  A fourth aspect of the electric motor according to the present invention is any one of the first to third aspects, and further includes a conductive member (7a, 7b) for electrically connecting the armature core and the bracket.

  A fifth aspect of the electric motor according to the present invention is any one of the first to fourth aspects, wherein the support members (6a, 6b) are electrically connected and fixed to a grounded member (70). The

  A sixth aspect of the electric motor according to the present invention is the fifth aspect, wherein the member (70) is a case for housing the electric motor (100).

  According to the electric motor of the present invention, the elastic body suppresses the transmission of the shaft vibration to the outside of the electric motor. Moreover, since this elastic body is conductive and conducts with the bracket, the electroerosion of the bearing is performed regardless of whether the armature core and / or the bracket is attached to the outside of the motor so as to have a large capacitance. Can be avoided. In addition, the elastic body is protected by the covering material.

It is sectional drawing which shows the structure of the electric motor concerning embodiment of this invention. It is sectional drawing which shows the structure of a supporting member. It is sectional drawing which shows the other structure of a supporting member.

  FIG. 1 is a cross-sectional view showing a configuration of an electric motor 100 according to an embodiment of the present invention. However, an air conditioner case 70 is also drawn. The case 70 is grounded during normal use.

  The electric motor 100 includes a rotor 10 and a stator 20. The rotor 10 has, for example, a cylindrical shape with the rotation axis P as the center. The rotor 10 and the stator 20 face each other through a gap (so-called air gap) in a radial direction (hereinafter, simply referred to as a radial direction) around the rotation axis P.

  More specifically, the stator 20 faces the rotor 10 from the opposite side with respect to the rotation axis P. The electric motor 100 is a so-called inner rotor type electric motor. The stator 20 applies a rotating magnetic field to the rotor 10, and the rotor 10 rotates according to the rotating magnetic field.

  The rotor 10 includes a rotor core. The rotor core has, for example, a cylindrical shape with the rotation axis P as the center, and the rotor core may be provided with a permanent magnet (not shown) that supplies a field to the stator 20. . Alternatively, the rotor core may have salient poles whose radial dimension varies in the circumferential direction around the rotation axis P (hereinafter simply referred to as the circumferential direction).

  The stator 20 functions as an armature and includes an armature core 21 and a winding 22. The armature core 21 faces the rotor 10 in the radial direction. The armature core 21 is a magnetic body, and includes a plurality of teeth 211 arranged radially around the rotation axis P, and a yoke 212 that magnetically connects the plurality of teeth 211 along the circumferential direction. ing.

  The winding 22 is attached to the armature core 21. More specifically, the winding 22 is wound around the tooth 211 with the radial direction as an axis. Unless otherwise specified in the present application, the winding 22 does not indicate each one of the conductive wires constituting the winding 22 but indicates an aspect in which the conductive wires are wound together. The same applies to the drawings. In addition, the drawing lines at the start and end of winding and their connection are also omitted in the drawings. When a current flows through the winding 22, the stator 20 can apply a rotating magnetic field to the rotor 10.

  While the magnetic flux flows in the armature core 21 according to the rotating magnetic field, the current also flows. In other words, the armature core 21 has conductivity. The armature core 21 may be formed of a laminated steel plate or a dust core so as to reduce eddy current flowing through the armature core 21.

  In the illustration of FIG. 1, the winding 22 and a part of the armature core 21 (for example, a portion excluding the surface facing the rotor 10) are covered with the resin portion 23. For example, the resin portion 23 is a so-called resin mold, and is in close contact with and covers the armature core 21 and the winding 22. As a result, the insulation between the winding 22 and the armature core 21 can be enhanced.

  Since the armature core 21 is not usually provided with the winding 22 on the surface facing the rotor 10, it is not necessary for the resin portion 23 to cover the facing surface. This is desirable from the viewpoint of reducing the air gap and improving the efficiency of the electric motor 100.

  A shaft 30 is attached to the rotor 10 (more specifically, the rotor core). For example, a shaft hole is formed in the rotor 10 in a direction parallel to the rotation axis P (hereinafter referred to as “axial direction”), and the shaft 30 is, for example, press-fitted and fixed to the shaft hole. The shaft 30 rotates as the rotor 10 rotates.

  The shaft 30 is supported by bearings 4a and 4b. The bearings 4 a and 4 b are located on the opposite sides of the rotor 10.

  In the example of FIG. 1, the case 70 houses the electric motor 100 and a load 91 driven by the electric motor 100. For example, a fan is employed as the load 91. Such a fan can be provided in an air conditioner, for example.

  The load 91 is attached to the shaft 30. Another load may be attached to the side opposite to the load 91 with respect to the electric motor 100 in the axial direction.

  In the illustration of FIG. 1, the shaft 30 extends in a horizontal direction substantially parallel to the ground. In such a structure, the shaft 30 is desirably supported by the two bearings 4a and 4b as described above. This is because the shaft 30 is easily bent by gravity if it is cantilevered.

  Each of the bearings 4 a and 4 b includes an inner ring 43, an outer ring 41, and a rolling element 42. The inner ring 43 has a ring shape around the rotation axis P and supports the shaft 30. Specifically, the shaft 30 passes through the inner ring 43 in the axial direction and is fixed to the bearings 4a and 4b.

  The outer ring 41 has a ring shape with the rotation axis P as the center, and faces the inner ring 43 in the radial direction. The rolling elements 42 are so-called rollers or balls that rotate between the outer ring 41 and the inner ring 43. As a result, the inner ring 43 can rotate around the rotation axis P with respect to the outer ring 41. Note that lubricating grease is interposed between the inner ring 43 and the outer ring 41 in order to reduce friction.

  The bearings 4a and 4b (more specifically, the outer ring 41) are fixed by brackets 5a and 5b, respectively. In the illustration of FIG. 1, the brackets 5 a and 5 b are fixed to the outer ring 41 of the bearings 4 a and 4 b, respectively, and are further fixed to the resin portion 23. If the motor is not provided with the resin portion 23, the brackets 5 a and 5 b are fixed to the armature core 21.

  If the brackets 5a and 5b are made of resin, the lubricating grease leaked from the bearings 4a and 4b comes into contact with the brackets 5a and 5b, and the brackets 5a and 5b are eroded. Therefore, it is desirable to form the brackets 5a and 5b from metal and suppress such erosion.

  Since the brackets 5a and 5b are made of metal, they have conductivity. FIG. 1 illustrates a mode in which the brackets 5a and 5b are electrically connected to the armature core 21 via the conductive members 7a and 7b, respectively.

  In the illustration of FIG. 1, the bracket 5b has the following shape. That is, the bracket 5b is rotated from a plate-shaped first ring member (portion extending in the vertical direction in the drawing) having a hole penetrating in the axial direction by the shaft 30 and an outer peripheral edge of the first ring member. A cylindrical member extending to the child 10 side (portion drawn extending in the left-right direction in the figure) and a plate-like second ring member extending in the radial direction from the cylindrical member (extending in the vertical direction in the figure) And a portion drawn). The bearing 4b contacts with the inner peripheral surface of the cylindrical member and is fixed to the bracket 5b. Moreover, the bracket 5 b is fixed to the resin portion 23 by embedding the outer peripheral portion of the second ring member in the resin portion 23.

  Moreover, in the illustration of FIG. 1, the bracket 5a has the following shape. That is, the bracket 5a includes a plate-shaped first ring member (a portion extending in the vertical direction in the drawing) having a hole penetrating in the axial direction by the shaft 30, and an outer peripheral edge of the first ring member. A cylindrical member extending toward the rotor 10 (a portion extending in the left-right direction in the drawing) and a plate-like second ring member extending in the radial direction from the cylindrical member (in the drawing in the vertical direction) And a ring-shaped recess that opens to the stator 20 side (right side in the drawing) at the outer peripheral edge of the second ring member. The bearing 4a contacts the inner peripheral surface of the cylindrical member and is fixed to the bracket 5a. Further, the bracket 5 a is fixed to the resin portion 23 by fitting the concave portion with the end portion (left end in the figure) of the resin portion 23 in the axial direction.

  The brackets 5a and 5b are held by support members 6a and 6b, respectively. Support members 6a and 6b sandwich brackets 5a and 5b together with bearings 4a and 4b, respectively. Each of the support members 6a and 6b has an inner shell 61, an outer shell 62, a helical spring 63a that is an elastic body, and a covering material 64.

  FIG. 2 is a cross-sectional view showing the configuration of the support member 6 employed as the support members 6a and 6b. The cross section is a plane perpendicular to the rotation axis P.

  Both the inner shell 61 and the outer shell 62 are cylindrical with the rotation axis P as the center, and have conductivity.

  The helical spring 63a is provided between the inner shell 61 and the outer shell 62, and has electrical conductivity for conducting the inner shell 61 and the outer shell 62.

  The covering material 64 is provided between the inner shell 61 and the outer shell 62, and molds the helical spring 63a. The covering material 64 has elasticity, and for example, resin or rubber is employed. Since both the helical spring 63a and the covering material 64 are elastic, vibrations of the rotor 10 or the stator 20, especially vibrations caused by the touching of the shaft 30, are external to the motor via the brackets 5a and 5b. Can be prevented from being transmitted. Moreover, the helical spring 63 a is protected by the covering material 64.

  FIG. 3 is a cross-sectional view showing another configuration of the support member 6 employed as the support members 6a and 6b. In contrast to the configuration shown in FIG. 2, the helical spring 63a is replaced with a leaf spring 63b. The leaf spring 63b is also provided between the inner shell 61 and the outer shell 62 in the same manner as the helical spring 63a. The leaf spring 63b is conductive with the inner shell 61 and the outer shell 62 and is molded with the covering material 64.

  In the illustration of FIG. 1, the support members 6a and 6b are fixed to the mounting legs 84a and 84b via the mounting portions 82a and 82b, respectively.

  For example, the attachment portion 82a has a cylindrical shape centered on the rotation axis P, and contacts and fixes the outer shell 62 of the support member 6a from the outer peripheral side. The attachment portion 82b has a cylindrical shape centered on the rotation axis P, and contacts and fixes the outer shell 62 of the support member 6b from the outer peripheral side.

  The mounting legs 84 a and 84 b have, for example, a plate shape and are fixed to the case 70. Accordingly, the attachment portions 82a and 82b are fixed to the case 70 by the attachment legs 84a and 84b, respectively.

  All of the attachment portions 82a and 82b and the attachment legs 84a and 84b have conductivity, and thereby, the support members 6a and 6b are conductively fixed to the case 70.

  As described above, the case 70 is normally grounded. Therefore, the armature core 21 is grounded via the conductive members 7a and 7b, the brackets 5a and 5b, the support members 6a and 6b, the mounting portions 82a and 82b, the mounting legs 84a and 84b, and the case 70.

  Providing a path for grounding the armature core 21 in this way is particularly suitable when the armature core 21 is covered with the resin portion 23. Moreover, the path can be provided by adding the support members 6a and 6b to the normal configuration, and the support members 6a and 6b exhibit the above-described vibration-proofing effect.

  In the electric motor 100 having such a structure, a pulsed AC voltage is applied to the winding 22 by, for example, PWM control. Such AC voltage includes harmonic components, and accordingly, current can flow from the winding 22 via the stray capacitance parasitic on the electric motor 100.

  For example, the gap between the load 91 and the case 70 is narrow, the gap between the armature core 21 and the case 70 is wide, and the gap between the winding 22 or the armature core 21 and the bracket 5a or the bracket 5b is narrow. The electric motor 100 and the load 91 may be stored. In this case, the capacitance between the load 91 and the case 70 and the capacitance between the winding 22 or the armature core 21 and the bracket 5a or the bracket 5b are large, and the space between the armature core 21 and the case 70 is large. The capacitance of is small.

  It is not desirable to reduce the radial dimension of the rotation axis P of the support members 6a and 6b in order to obtain vibration isolation. Therefore, if these are insulative, their capacitance will be small.

  In addition, as a material for the shaft 30, it is desirable to employ a metal in order to increase its strength. In this case, the shaft 30 has conductivity.

  Therefore, when the above configuration is adopted, the current based on the harmonic component of the AC voltage applied to the winding 22 is the winding 22, the armature core 21, the brackets 5a and 5b, the bearings 4a and 4b, the shaft 30, the load. 91, easily flows to the ground via the case 70. As a result, electrolytic corrosion occurs in the bearings 4a and 4b.

  However, even in the above-described configuration, when the support members 6a and 6b have conductivity as shown in the present embodiment, the current is supplied to the winding 22 (or the armature core 21). It flows through the brackets 5a and 5b, the support members 6a and 6b, the mounting portions 82a and 82b, the mounting legs 84a and 84b, and the case 70. As a result, no current flows through the bearings 4a and 4b, and no electrolytic corrosion occurs here.

  In other words, by making the supporting members 6a and 6b used to reduce the transmission of vibration to the outside conductive, the distance between the load 91 and the case 70, the distance between the armature core 21 and the case 70, the winding It is possible to avoid electrolytic corrosion in the bearings 4a and 4b regardless of whether the distance between the wire 22 and the bracket 5a or the bracket 5b is wide or not and whether or not the shaft 30 is conductive.

  For example, it is desirable to connect the armature core 21 to the brackets 5a and 5b using the conductive members 7a and 7b in the following points.

  Usually, the winding 22 is provided very close to the armature core 21, and the capacitance between them is large. In addition, since the air gap is normally set small, the capacitance between the armature core 21 and the rotor 10 is also small. Therefore, if the space between the armature core 21 and the brackets 5a and 5b is wide, the stray capacitance between the winding 22 and the armature core 21 becomes small, and the shaft 30 passes through the rotor 10 from the armature core 21. Current flows easily, and further current flows to the support members 6a and 6b via the bearings 4a and 4b.

  In such a case, it is desirable that the armature core 21 and the brackets 5a and 5b are electrically connected to each other because there is a possibility that electric corrosion occurs in the bearings 4a and 4b.

  Of course, as long as the armature core 21 and the brackets 5a and 5b are arranged in such a manner that they are conducted, there is no need to provide the conducting members 7a and 7b.

10 Rotor 20 Stator (armature)
30 shaft 4a, 4b bearing 5a, 5b bracket 6a, 6b support member 61 inner shell 62 outer shell 63a helical spring 63b leaf spring 7a, 7b conducting member 100 electric motor

Claims (6)

A rotor (10) rotating about a predetermined axis (P);
An armature (20) having an armature core (21) facing the rotor on the opposite side of the shaft to the rotor, and a winding (22) attached to the armature core;
A conductive shaft (30) fixed to the rotor;
Bearings (4a, 4b) having an inner ring (43) supporting the shaft and an outer ring (41);
Brackets (5a, 5b) that are electrically connected to the armature core and fix the outer ring;
Inner shell (61), outer shell (62) sandwiching the bracket together with the outer ring, conductive elastic bodies (63a, 63b) provided between the inner shell and the outer shell, which are provided between the inner shell and the outer shell. ), An electric motor (100) comprising a support member (6a, 6b) provided between the inner shell and the outer shell and having an elastic covering material (64) for molding the elastic body.   The electric motor according to claim 1, wherein at least one of a helical spring (63a) and a leaf spring (63b) is employed as the elastic body (63a, 63b).   The electric motor according to claim 1, wherein at least one of resin and rubber is employed for the covering material. Conductive members (7a, 7b) for conducting the armature core and the bracket.
The electric motor according to any one of claims 1 to 3, further comprising:   The electric motor according to any one of claims 1 to 4, wherein the support member (6a, 6b) is conductively fixed to a grounded member (70).   The electric motor according to claim 5, wherein the member (70) is a case for housing the electric motor (100).

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