JP2012130157A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor which suppresses electric corrosion of a bearing in both a path which passes through a stator from a coil and a path which passes through a rotator from the coil.SOLUTION: A rotator 10 rotates around a rotation shaft P. A stator 20 comprises: a stator core 21 which faces the rotator 10 on the side opposite to the rotation shaft 10 and has a connection end 80 on the side opposite to the rotator 10; a coil 22 attached to the stator core 21; and an insulative resin part 23 covering the coil 22 and the stator core 21 while exposing the connection end 80. A shaft 30 is fixed to the rotator 10. A bearing 41 has an inner ring supporting the shaft 30 and an outer ring. A bracket 51 fixes the resin part 23 to the outer ring. An attachment member 61 holds the bracket 51 while being insulated from the bracket.

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) which 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, in the technique described in Patent Document 1, the stator core and the bracket are connected by a ground terminal.

JP 2004-229429 A

  However, in the technique described in Patent Document 1, a route from the winding to the stator core, the rotor, the shaft, the bearing, and the bracket is not considered. If current flows in such a path, electrolytic corrosion occurs in the bearing.

  Then, an object of this invention is to provide the electric motor which can suppress the electrolytic corrosion of a bearing in both the path | route which does not go through a rotor from a coil | winding, and the path | route which goes through.

  A first aspect of the electric motor according to the present invention includes a rotor (10) that rotates around a rotation axis, and faces the rotor on the opposite side of the rotation axis, and a connection end ( 80), a winding core (22) attached to the stator core, and an insulating resin portion that covers the winding core and the stator core while exposing the connection end ( 23), a shaft (30) fixed to the rotor, an inner ring supporting the shaft, and bearings (41, 42) having an outer ring, the resin portion, and the Brackets (51, 52) for fixing the outer ring and mounting members (61, 62) for holding the bracket while being insulated from the bracket.

  The 2nd aspect of the electric motor concerning this invention is an electric motor concerning the 1st aspect, Comprising: The said connection end (80) is conducting wire.

  The 3rd aspect of the electric motor concerning this invention is an electric motor concerning the 1st or 2nd aspect, Comprising: The said attachment member (61, 62) has a vibration isolating rubber which contacts the said bracket.

  A fourth aspect of the electric motor according to the present invention is the electric motor according to any one of the first to third aspects, wherein the stator core (21) is a plurality of layers stacked in a direction along the rotation axis. A steel plate, and at least one of the plurality of steel plates has a protruding portion that protrudes in a radial direction as compared with the other steel plates, and the resin portion (23) exposes the protruding portion to the stator core. And the winding, and the protrusion functions as the connection end.

  According to the 1st aspect of the electric motor concerning this invention, the insulation between a coil | winding and another member is securable by the resin part. Therefore, the spatial distance required for insulation can be reduced, and this contributes to the miniaturization of the electric motor. Moreover, since the bearing and the resin portion are fixed by the bracket, the electromagnetic vibration of the stator core is not easily transmitted to the bearing.

  In addition, since the connection end of the stator core is exposed from the resin part, the harmonic current that flows through the stray capacitance between the winding and the stator core is connected from the stator core to the outside of the motor. Can be flowed through. Since there is no bearing in this path, there is no electrical corrosion of the bearing.

  On the other hand, if the case is conductive when the electric motor is provided on the case by the mounting member, the stray capacitance between the winding and the rotor (both the route through the stator core and the route not through it) The harmonic current that flows through the stray capacitance may flow from the case to the outside of the motor via the stray capacitance that exists between the rotor, the bearing, the bracket, and the case. However, the bracket is provided on the mounting member while being insulated. Therefore, when the electric motor is provided in the case by the mounting member, even if the case is conductive, compared to the case where the bracket is connected to the case, only the amount of voltage supported by the capacitance in the mounting member The voltage supported by the bearing is reduced. Therefore, electric corrosion of the bearing is suppressed.

  According to the second aspect of the electric motor of the present invention, the conducting wire can be easily bent, and the current path formed between the stator core and the case can be adjusted relatively easily. Therefore, the stator core and the case can be connected to each of the cases having a plurality of different shapes at a relatively short distance. Therefore, it is not necessary to individually design the connection ends when mounting on a plurality of products.

  According to the 3rd aspect of the electric motor concerning this invention, it can suppress that the vibration of an electric motor transmits to a case.

  According to the 4th aspect of the electric motor concerning this invention, it is easy to provide a connection end in a stator core.

It is a figure which shows an example of a notional structure of the electric motor in the cross section containing a perpendicular direction. It is a figure which shows an example of a notional structure of the electric motor in the cross section containing a perpendicular direction.

Embodiment.
In the example illustrated in FIG. 1, the electric motor 100 includes a rotor 10 and a stator 20. FIG. 1 shows a cross section including the rotation axis P of the rotor 10 along the vertical direction. The rotor 10 and the stator 20 face each other through a gap (so-called air gap) in the radial direction around the rotation axis P (hereinafter simply referred to as the radial direction). 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 around the rotation axis P in accordance with 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 that supplies a field to the stator 20. Alternatively, the rotor core may have salient poles whose radial size varies in the circumferential direction around the rotation axis P (hereinafter simply referred to as the circumferential direction). Such a rotor core forms a magnetic circuit with the stator 20.

  The stator 20 includes a stator core 21, a winding 22, a resin portion 23, and a connection end 80. The stator core 21 faces the rotor 10 in the radial direction. The stator core 21 is a magnetic body, and includes a plurality of teeth 211 radially arranged around the rotation axis P, and a yoke 212 that magnetically couples the plurality of teeth along the circumferential direction. Yes. The winding 22 is attached to the stator 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 does not indicate each one of the conductive wires constituting the winding, 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.

  In the stator core 21, magnetic flux flows according to the rotating magnetic field, but current also flows. In other words, the stator core 21 has conductivity. Note that the stator core 21 may be formed of a laminated steel plate, a dust core, or the like in order to reduce eddy current flowing through the stator core 21.

  The connection end 80 is provided on the stator core 21 on the side opposite to the rotor 10. In the illustration of FIG. 1, the connection end 80 is a conducting wire, and one end thereof is connected to the stator core 21. The connection end 80 is not limited to a conducting wire, and may be any member having electrical conductivity.

  The insulating resin portion 23 covers the stator core 21 and the winding 22 while exposing the connection end 80. For example, the resin portion 23 is a so-called resin mold, and is in close contact with and covers the stator core 21 and the winding 22. As a result, the insulation between the winding 22 and, for example, the stator core 21 or the insulation between the winding 22 and other members described later can be enhanced. Therefore, the spatial distance required for insulation can be shortened, which contributes to the miniaturization of the electric motor 100.

  In the illustration of FIG. 1, the resin portion 23 does not cover the surface of the stator core 21 that faces the rotor 10. In other words, the facing surface is exposed. According to this, since the resin portion 23 is not interposed between the rotor 10 and the stator 20 in the radial direction, the magnetic flux applied from the stator 20 to the rotor 10 is not reduced. Therefore, it can avoid that the efficiency of the electric motor 100 reduces.

  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 parallel to the axis P, and the shaft 30 is press-fitted into the shaft hole. The shaft 30 rotates as the rotor 10 rotates. The shaft 30 is made of, for example, metal and has conductivity.

  The shaft 30 is supported by bearings 41 and 42. The bearings 41 and 42 are located on opposite sides of the rotor 10 in a direction along the rotation axis P (hereinafter referred to as an axial direction). Each of the bearings 41 and 42 includes an inner ring, an outer ring, and a rolling element. The inner ring has a ring shape centered on the axis P, and the shaft 30 penetrates the inner ring in the axial direction and is fixed thereto. The outer ring has a ring shape centered on the axis P, and faces the inner ring in the radial direction. The rolling elements are so-called rollers or balls that rotate between the outer ring and the inner ring. As a result, the inner ring can rotate about the axis P with respect to the outer ring. In order to reduce friction, lubricating grease is interposed between the inner ring and the outer ring.

  The bearings 41 and 42 are fixed to the resin portion 23 by brackets 51 and 52, respectively. More specifically, the brackets 51 and 52 are respectively fixed to the outer rings of the bearings 41 and 42 and further fixed to the resin portion 23. The brackets 51 and 52 are metal. On the other hand, for example, if the brackets 51 and 52 are made of resin, the lubricating grease leaked from the bearings 41 and 42 comes into contact with the brackets 51 and 52 and the brackets 51 and 52 are eroded. Since the brackets 51 and 52 are made of metal, the erosion of the brackets 51 and 52 can be suppressed. Further, the brackets 51 and 52 are not directly fixed to the stator core 21 but are directly fixed to the resin portion 23. Therefore, the electromagnetic vibration of the stator core 21 is not directly transmitted to the brackets 51 and 52 but is transmitted to the brackets 51 and 52 through the resin portion 23. Therefore, it is difficult for electromagnetic vibration to be transmitted to the brackets 51 and 52, and consequently the bearings 41 and 42.

  In the illustration of FIG. 1, the bracket 52 has the following shape. That is, the bracket 52 includes a plate-like first ring member having a hole penetrating in the axial direction by the shaft 30, a cylindrical member extending from the outer peripheral edge of the first ring member toward the rotor 10, and the cylindrical member. And a plate-like second ring member extending in the radial direction. The bearing 42 is press-fitted into the inner peripheral surface of the cylindrical member and fixed to the bracket 52. Further, the bracket 52 is fixed to the resin portion 23 by the second ring member being embedded in the resin portion 23.

  In the illustration of FIG. 1, the bracket 51 has the following shape. That is, the bracket 51 includes a plate-like first ring member having a hole penetrating in the axial direction by the shaft 30, a cylindrical member extending from the outer peripheral edge of the first ring member toward the rotor 10, and the cylinder. A plate-like second ring member extending in the radial direction from the member, and a ring-shaped recess opening to the rotor 10 side at the outer peripheral edge of the second ring member are provided. The bearing 41 is press-fitted into the inner peripheral surface of the cylindrical member and fixed to the bracket 51. In addition, the bracket 51 is fixed to the resin portion 23 by fitting the recess with the protrusion formed on the resin portion 23 in the axial direction.

  The brackets 51 and 52 are held while being insulated by the mounting members 61 and 62. In the illustration of FIG. 1, the attachment member 61 includes an insulator 611, attachment portions 612 and 613, and attachment legs 614. The insulator 611 has, for example, a ring shape centered on the axis P and contacts the outer peripheral surface of the bracket 51. In the illustration of FIG. 1, the insulator 611 contacts the outer peripheral surface of the cylindrical member of the bracket 51, and faces the bearing 41 via the bracket 51 in the radial direction.

  The insulator 611 is fixed to the case 70 by, for example, mounting portions 612 and 613 and mounting legs 614. In the example of FIG. 1, the case 70 accommodates the electric motor 100 and loads 91 and 92 driven by the electric motor 100. Each of the attachment portions 612 and 613 is a semicircular ring member having the rotation axis P as the center. The attachment portions 612 and 613 can be fixed so as to face each other. In this state, the attachment portions 612 and 613 form a ring shape with the rotation axis P as the center. The attachment portions 612 and 613 are in contact with the outer peripheral surface of the insulator 611 in the radial direction. The attachment portions 612 and 613 are fixed to each other while being in contact with the insulator 611. With this fixing, the attachment portions 612 and 613 can tighten the insulator 611 in the radial direction, and thereby the attachment portions 612 and 613 are fixed to the insulator 611. The mounting leg 614 is fixed to the mounting portion 612. The mounting leg 614 has a plate shape, for example, and is also fixed to the case 70.

  Here, the mounting portions 612 and 613 and the mounting legs 614 are made of metal, for example, and have conductivity. However, the whole attachment member 61 may be formed of a member having insulating properties.

  Further, an anti-vibration rubber may be employed as the insulator 611. According to this, it is possible to prevent the vibration of the electric motor 100 from being transmitted to the case 70.

  In the illustration of FIG. 1, the attachment member 62 is the same as the attachment member 61, and thus repeated description is avoided.

  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 preferably supported by the two bearings 41 and 42 as described above. This is because the shaft 30 is easily bent by gravity if it is cantilevered.

  In the illustration of FIG. 1, loads 91 and 92 are attached to the shaft 30. The loads 91 and 92 are located on the opposite sides with respect to the electric motor 100 in the axial direction. However, the loads 91 and 92 may be located only on one side in the axial direction with respect to the electric motor 100, or a single load may be attached without attaching a plurality of loads. The loads 91 and 92 are fans, for example.

  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 an AC voltage includes a harmonic component, and accordingly, a current can flow via a capacitance parasitic on the electric motor 100. However, according to the electric motor 100, the connection end 80 provided on the stator core 21 is exposed from the resin portion 23. Therefore, the connection end 80 can be connected to the outside of the electric motor 100 (for example, the case 70). Alternatively, the connection end 80 may be brought close to the outside of the electric motor 100. Therefore, the harmonic current flowing through the stray capacitance parasitic between the winding 22 and the stator core 21 can flow from the stator core 21 to the outside of the electric motor 100 via the connection end 80. Since the bearings 41 and 42 are not interposed in this path, the electrolytic corrosion of the bearings 41 and 42 is not caused.

  In the example of FIG. 1, the connection end 80 is electrically connected to the case 70. Therefore, when the case 70 is conductive, the above-described current is more likely to flow from the stator core 21 to the outside of the electric motor 100. Therefore, the electric corrosion of the bearings 41 and 42 can be further suppressed. In this case, the case 70 may be grounded.

  On the other hand, when the case 70 has conductivity, it flows through a stray capacitance between the winding 22 and the rotor 10 (a stray capacitance including both a route through the stator core 21 and a route through the stator core 21). The harmonic current can flow to the case 70 via the stray capacitance existing between the rotor 10, the shaft 30, the bearings 41 and 42, the brackets 51 and 52, the mounting members 61 and 62, and the case 70. However, the brackets 51 and 52 are provided on the mounting members 61 and 62 while being insulated. Therefore, compared to the case where the brackets 51 and 52 are connected to the case 70, the voltage supported by the bearings 41 and 42 is reduced by the amount of the voltage supported by the capacitance of the mounting members 61 and 62. Therefore, even if the case 70 is conductive, the electrolytic corrosion of the bearings 41 and 42 can be suppressed.

  As described above, the harmonic current flowing from the winding 22 to the stator core 21 is allowed to flow to the outside of the electric motor 100 via the connection end 80, thereby suppressing the electrolytic corrosion of the bearings 41 and 42, In the current path flowing from the bearing 22 to the bearings 41 and 42 via the rotor 10 and the shaft 30, the voltage applied to the bearings 41 and 42 by the mounting members 61 and 62 is reduced to suppress the electrolytic corrosion of the bearings 41 and 42. . Therefore, the electrolytic corrosion of the bearings 41 and 42 can be appropriately suppressed.

  If the connection end 80 is connected to the case 70, the connection end 80 is a conductive wire, thereby inducing the effects described below. First, the longer the path of the connection end 80 between the stator core 21 and the case 70, the higher the resistance of the connection end 80. On the other hand, if the connection end 80 is formed of a conductive wire, the conductive wire can be easily bent or cut, and the current path formed between the stator core 21 and the case 70 can be adjusted relatively easily. Therefore, the stator core 21 and the case 70 can be connected to each of the cases 70 having a plurality of different shapes at a relatively short distance. Therefore, when the electric motor 100 is mounted on a plurality of products, individual design is not required.

  Next, another example of the connection end 80 will be described. In the electric motor 100 illustrated in FIG. 2, the stator core 21 is formed of a plurality of steel plates 213 as compared with the electric motor 100 in FIG. 1. The plurality of steel plates 213 are stacked along the rotation axis P. At least one of the plurality of steel plates 213 has a protruding portion 2131 that protrudes in the radial direction with respect to the other steel plate 213 at the outer peripheral edge thereof. The resin portion 23 covers the stator core 21 and the winding 22 in close contact with each other while exposing the protrusion 2131. The protrusion 2131 functions as part or all of the connection end 80.

  Each of these steel plates 213 can be formed by punching a predetermined steel plate. And the stator core 21 which has the connection end 80 can be manufactured with the conventional manufacturing method of laminating | stacking these some steel plates 213 along the rotating shaft P. FIG. Therefore, the process of fixing the connection end 80 to the stator core 21 can be omitted. In other words, it is easy to provide the connection end 80 on the stator core 21.

  Further, the resin portion 23 covers the winding 22 and the stator core 21 in close contact with each other while exposing the protrusion 2131. Therefore, the conductive wire 81 can be connected to the protrusion 2131 after the resin portion 23 is formed. Therefore, the presence or absence of the conducting wire 81 can be determined after the motor 100 is manufactured. In the illustration of FIG. 2, the conductive wire 81 connects the protrusion 2131 and the case 70. In this example, the conductive wire 81 and the protrusion 2131 can be grasped as the connection end 80.

DESCRIPTION OF SYMBOLS 10 Rotor 20 Stator 21 Stator core 22 Winding 23 Resin part 30 Shaft 41, 42 Bearing 51, 52 Bracket 61, 62 Mounting member 70 Case 80 Connection end

Claims (4)

A rotor (10) that rotates about a rotation axis;
A stator core (21) facing the rotor on the opposite side of the rotation shaft and having a connection end (80) on the opposite side of the rotor, and a winding (22) attached to the stator core; A stator (20) having an insulating resin portion (23) covering the winding and the stator core while exposing the connection end;
A shaft (30) fixed to the rotor;
A bearing (41, 42) having an inner ring supporting the shaft and an outer ring;
Brackets (51, 52) for fixing the resin portion and the outer ring;
An electric motor comprising mounting members (61, 62) that hold the bracket while being insulated from the bracket.   The electric motor according to claim 1, wherein the connection end (80) is a conducting wire.   The electric motor according to claim 1 or 2, wherein the mounting member (61, 62) has an anti-vibration rubber in contact with the bracket. The stator core (21) has a plurality of steel plates stacked in a direction along the rotation axis,
At least one of the plurality of steel plates has a protruding portion that protrudes in a radial direction than the other steel plates,
The said resin part (23) exposes the said projection part, covers the said stator core and the said coil | winding, and the said projection part functions as the said connection end. Electric motor.

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