JP4894493B2 - Insulation ring and rotating electric machine - Google Patents

Description

  The present invention relates to an insulating ring for preventing electric corrosion caused by a current flowing in a bearing of a rotating electrical machine driven by an inverter, and a rotating electrical machine using the insulating ring.

  In a product using a drive device composed of a so-called PWM inverter device and a rotating electrical machine driven by the PWM inverter device, such as a fan motor or a submersible pump whose rotational speed is controlled by the inverter device, the bearing of the rotating electrical machine is electrically connected. There is a phenomenon in which corrosion occurs, and the electric corrosion damages the bearing. For this reason, various improvement proposals have conventionally been made in order to reduce or prevent such damage to the bearing caused by electric corrosion.

  For example, a thermoplastic elastomer layer is formed on the outer periphery of the outer ring of a rolling bearing that fixes the rotating shaft of the induction motor, and the ball or the entire bearing is formed of ceramic (insulator), and the rotating shaft and the ground are formed. There has been proposed one that prevents damage to the bearing due to electrolytic corrosion by insulating the side (see, for example, Patent Document 1).

  As another example, the gap between the rotating part and the stationary part of the bearing is filled with conductive grease, and the motor rotor and the motor frame case are electrically connected to each other. In order to reduce the potential difference between the two, it has been proposed to prevent damage to the bearing due to electrolytic corrosion (see, for example, Patent Document 2).

  As another example, there has been proposed one that prevents damage to the bearing due to electrolytic corrosion by forming a two-layer or three-layer structure in which a ceramic layer and a metal layer are laminated on the outer periphery of the bearing outer ring (for example, And Patent Document 3).

  Furthermore, as another example, an insulating material provided with a convex portion and a bracket provided with a concave portion are fitted together, and the insulating material is interposed between the bearing and the bracket, thereby preventing damage to the bearing due to electrolytic corrosion. The thing is proposed (for example, refer patent document 4).

JP-A-10-184699 (FIG. 5, paragraph numbers 0070 to 0072) JP 2001-107887 A (FIGS. 1 to 6, paragraph numbers 0008 to 0010) JP 2002-181054 A (FIGS. 1 to 5, paragraph numbers 0010 to 0023) Japanese Unexamined Patent Publication No. 2000-156952 (FIGS. 1 to 4, paragraph numbers 0026 to 0038)

However, the following problems arise in the electric corrosion countermeasures for bearings depending on mechanical means such as Patent Document 1 and Patent Document 2 described above.
That is, in an induction motor using ceramic bearings as described in Patent Document 1, the price of ceramic bearings is several tens of times higher than that of bearings made of general-purpose metals. The amount cannot be ignored and there are few types.
In addition, in the induction motor using conductive grease as the grease to be sealed in the bearing as described in Patent Document 2, a minute amount of carbon powder exists in the grease in order to provide electrical conductivity. On the contrary, sparks are generated and carbon powder is regarded as a foreign substance, so that the effect is not sustained because it is repelled from the rolling surface.
Moreover, when an insulating material is comprised from a ceramic like patent document 3, the freedom degree of design is small and a price is high.
Furthermore, when the insulating material and the bracket are fitted with concavities and convexities as in Patent Document 4, the processing accuracy of fitting the insulating material and the bracket is required. In addition, a structure in which a load is directly applied to an insulating material lacks long-term reliability due to damage to the insulating material.

  The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to provide an insulating ring and a rotating electrical machine that can reduce the electric corrosion of a bearing stably at low cost over a long period of time. It is what.

An insulating ring according to the present invention is interposed between a metal outer ring, a metal inner ring disposed coaxially in the outer ring with a predetermined gap, and the outer ring and the inner ring. And an insulator that electrically insulates the two.
Further, the rotating electrical machine according to the present invention includes a metal outer ring, a metal inner ring disposed coaxially in the outer ring with a predetermined gap, and interposed between the outer ring and the inner ring. An insulating ring having a structure that includes an insulator that electrically insulates the two is interposed between the bracket and the bearing.

  According to the present invention, it is possible to obtain an insulating ring and a rotating electrical machine that can reduce the electrolytic corrosion of a bearing stably at low cost over a long period of time.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIGS.
FIG. 1 is a diagram showing the structure of a rotating electrical machine (electric motor) according to Embodiment 1 of the present invention.
The rotating electrical machine includes a rotor composed of a rotating shaft 1 and a rotor core 2, a metal stator 3 having a stator coil 4 disposed outside the rotor with a predetermined gap, A metal frame 5 disposed outside the stator 3, a metal bracket 6 electrically connected to both ends of the frame 5, and the rotating shaft 1 of the rotor can be freely rotated with respect to the bracket 6. The inner and outer rings and the rolling bearing 7 are made of metal, and are driven at a variable speed by supplying power from the inverter to the stator coil 5 disposed in the slot of the stator 3. The

Further, an insulating ring 8 that reduces electric corrosion of the rolling bearing 7 is inserted between the bracket 6 and the outer ring of the rolling bearing 7.
As shown in detail in FIG. 2, the insulating ring 8 includes a metal outer ring 8a, a metal inner ring 8b arranged coaxially in the outer ring 8a with a predetermined gap, and an outer ring. Insulation made of cast resin that is interposed between 8a and inner ring 8b and electrically insulates between outer ring 8a and inner ring 8b by filling the gap between outer ring 8a and inner ring 8b. It comprises a body 8c. In addition, the inner and outer diameters of the inner and outer rings 8a and 8b, the thickness of the insulator 8c, and the axial dimension of the insulating ring 8 are selected according to the capacity of the rotating electrical machine.
Further, the inner ring 8b of the insulating ring 8 has an L-shaped bent portion (abutting portion) 8ba that comes into contact with the outer side surface of the outer ring of the rolling bearing 7, and the rolling bearing 7 is formed at the bent portion 8ba. Is prevented from moving in the axial direction. Further, the insulator 8c of the insulating ring 8 is also interposed between the bent portion 8ba of the inner ring 8b and the bracket 6 so as to electrically insulate between the bent portion 8ba of the inner ring 8b. It is extended and provided.

In addition, as a material of the outer ring 8a and the inner ring 8b of the insulating ring 8, for example, steel plate, stainless steel, aluminum, copper, casting, titanium, tungsten, or the like is used from the viewpoint of workability and availability.
The insulator 8c is made of a material having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more and a difference in linear expansion coefficient between the outer ring 8a and the inner ring 8b of 60 × 10 ⁻⁶ ppm / ° C. or less. Some casting resin is used.
As a resin having a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more and a difference in linear expansion coefficient from the metal part of 60 × 10 ⁻⁶ ppm / ° C. or less, specifically, epoxy resin, silicone resin, urethane resin, heat A plastic elastomer is mentioned. If the volume resistivity is lower than 1 × 10 ¹⁰ Ω · cm, a sufficient insulating effect cannot be obtained. On the other hand, if the difference in coefficient of linear expansion is greater than 60 × 10 ⁻⁶ ppm / ° C., stress due to thermal strain increases due to the thermal cycle during operation / stop and cracks are generated.

The insulator 8c of the insulating ring 8 can be blended with inorganic powder to reduce shrinkage and improve strength and elastic modulus.
Examples of inorganic powders include fused silica, crystalline silica, olivine, wollastonite, cordierite or forsterite, alumina, hydrated alumina, aluminum hydroxide, hollow glass beads, glass fibers, and oxidation. Magnesium, titanium oxide, calcium carbonate, magnesium carbonate, dolomite, talc, potassium titanate fiber, calcium hydroxide, magnesium hydroxide, antimony trioxide, anhydrous gypsum, barium sulfate, boron nitride, silicon carbide, aluminum fluoride, fluoride Examples of the powder include calcium, magnesium fluoride, and aluminum borate. The inorganic powders can be used alone or in any combination.

The insulating ring 8 is manufactured as follows.
That is, as shown in FIG. 3, the first casting jig 9, the inner ring 8b fitted in the first casting jig 9, and the outer ring 8a arranged concentrically with the inner ring 8b are 2 is attached to the casting jig 10. At this time, the insulator 8c made of the casting resin is sealed and attached so that the insulator 8c does not leak from the attachment portion at the time of injection. Then, the insulator 8c is injected from above. After the insulator 8c is heated and cured at a predetermined temperature for a predetermined time, the second casting jig 10 and the first casting jig 9 are removed to obtain the insulating ring 8 as shown in FIG. In order to obtain the concentricity of the contact portion with the rolling bearing 7 and the contact portion with the bracket 6, the inner periphery of the inner ring 8b or the outer periphery of the outer ring 8a is machined, and the casting surface of the insulator 8c Is processed so as to be flush with the end face of the outer ring 8a, whereby the insulating ring 8 is obtained.
Thus, the insulating ring 8 does not require a large facility and can be manufactured with an extremely simple facility.

Further, since the insulating ring 8 used in the present embodiment is configured as described above, the capacitance and impedance can be easily set to values that are effective for the phenomenon considered to be the cause of electrolytic corrosion. Can be optimized.
In other words, the phenomena considered to be the cause of electrolytic corrosion are (1) bearing induced voltage due to neutral point voltage and (2) circulating current (frame → bracket → bearing → stator → bearing → bracket → frame Current due to time variation of
(1) In order to suppress the bearing induced voltage caused by the neutral point voltage, the capacitance of the insulating ring 8 is sufficiently larger than the capacitance between the stator and the rotor (between the motor stator and the rotor). 10 times more than the capacitance of
Also, (2) In order to suppress the circulating current, a large current flows instantaneously (rising frequency from several MHz to several 100 MHz), so that sufficient impedance is required to suppress the current to 1/100 or less (Z = 1 / (2 × π × f (frequency) × capacitance)).

However, as shown in Table 1, the insulating ring 8 is a thin-film insulating structure in which a large amount of circulating current flows when the capacitance increases (a circulating current of 300 mA flows at 650 pF). In this case, a sufficient electric corrosion suppression effect cannot be obtained. That is, the capacitance of the insulating ring 8 needs to be optimized to a value that is not too small and not too large.
Table 1 shows experimental data when an epoxy resin is used as the insulator 8c and the rotational speed of the rotating electrical machine is 2000 rpm.

Table 1. Insulation ring capacitance and circulating current

According to the structure of the insulating ring 8 used in the present embodiment, the capacitance is adjusted by adjusting the diameter of the inner and outer rings 8a and 8b and adjusting the gap between which the insulator 8c is inserted. -It is possible to easily obtain a structure that can suppress the circulating current to 1/100 or less than the electrostatic capacity between the rotors.
The synthetic capacitance of the insulating ring 8 is preferably 200 pF or less.

As described above, according to the structure of the insulating ring 8 of the first embodiment, it is very easy to adjust the diameter of the inner and outer rings 8a and 8b and adjust the gap into which the insulator is inserted. Capacitance and impedance can be optimized.
Further, since the insulator 8c is protected by the metal inner and outer rings 8a and 8b, a load is not directly applied to the insulator 8c, and a stable electrolytic corrosion suppressing effect can be obtained over a long period of time.
Further, a fitting tolerance (concentricity) of the rolling bearing 7 is required on the outer peripheral side of the outer ring 8a and the inner peripheral side of the inner ring 8b, but on the insulator 8c side (the inner peripheral side of the outer ring 8a and the inner ring). The outer peripheral side of 8b does not require concentricity more than that, and the insulator 8c does not require processing accuracy, so that it can be manufactured at low cost by general-purpose resin and general-purpose processing. In addition, a dedicated metal mold is not required, and the insulating ring 8 can be obtained stably and highly reliable even if there is insufficient dimensional accuracy during assembly of the jig or curing shrinkage of the resin.
Further, the inner ring 8b is provided with an L-shaped bent portion 8ba that comes into contact with the outer side surface of the outer ring of the rolling bearing 7, and the insulator 8c extends between the bent portion 8ba and the bracket 6. Therefore, the bent portion 8ba can prevent the rolling bearing 7 from moving in the axial direction, and the electrical connection between the bracket 6 and the outer ring of the rolling bearing 7 can be achieved without adding a new insulating structure. Can be electrically insulated.

  In the first embodiment, the axial movement of the rolling bearing 7 is prevented, and the bracket 6 and the outer ring of the rolling bearing 7 are electrically insulated, so that the inner ring 8b is connected to the outer side of the outer ring of the rolling bearing 7. An L-shaped bent portion 8ba that abuts on the side surface is provided, and an insulator 8c is provided between the bent portion 8ba and the bracket 6, but the rolling bearing 7 is provided by the inner ring 8b. When it is not necessary to prevent the axial movement, it is not necessary to provide the L-shaped bent portion 8ba on the inner ring 8b. However, in this case, it is necessary to consider a configuration in which the inner ring 8b and the bracket 6 are not electrically connected to each other by interposing an insulator 8c between the inner ring 8b and the bracket 6, for example. is there.

Embodiment 2
Next, Embodiment 2 will be described with reference to FIG.
The insulating ring 8 according to the second embodiment includes a plurality of recesses 8aa and 8bb extending in the axial direction at equal intervals on the inner periphery of the outer ring 8a and the outer periphery of the inner ring 8b (this embodiment In the case of 4).
As a result, when the insulating ring 8 is manufactured as shown in FIG. 3, the insulator 8c made of cast resin is also injected into the recesses 8aa and 8ba. For this reason, when this insulating ring 8 is installed in a rotating electrical machine as shown in FIG. 1, it is possible to prevent the outer ring 8a and the inner ring 8b from sliding in the circumferential direction with respect to the insulator 8c, and a highly reliable insulation. A ring 8 can be obtained.
Needless to say, a similar effect can be obtained by using a convex portion instead of the concave portions 8aa and 8bb. Further, when it is desired to prevent only the slip between the outer ring 8a and the insulator 8c, a recess 8aa or a recess may be provided only in the inner peripheral portion of the outer ring 8a, and the inner ring 8b and the insulator 8c When it is desired to prevent only slippage between the inner ring 8b, the concave portion 8ba or the concave portion may be provided only on the outer peripheral portion of the inner ring 8b.

Embodiment 3 FIG.
Next, Embodiment 3 will be described with reference to FIG.
The insulating ring 8 according to the third embodiment includes a plurality of radially recessed recesses 8ab and 8bc at equal intervals (in this embodiment) on the inner periphery of the outer ring 8a and a part of the outer periphery of the inner ring 8b. In the case of the form, four places) are provided.
As a result, when the insulating ring 8 is manufactured as shown in FIG. 3, the insulator 8c made of cast resin is also injected into the recesses 8ab and 8bc. For this reason, when this insulating ring 8 is installed in a rotating electrical machine as shown in FIG. 1, the outer ring 8a and the inner ring 8b can be prevented from sliding in the axial direction with respect to the insulator 8c, and can be slid in the circumferential direction. Therefore, the insulating ring 8 having high reliability can be obtained.
Needless to say, the same effect can be obtained by using a convex portion instead of the concave portions 8ab and 8bc. In addition, when it is desired to prevent only the slip between the outer ring 8a and the insulator 8c, a recess 8ab or a recess may be provided only in the inner peripheral portion of the outer ring 8a, and the inner ring 8b and the insulator 8c When it is desired to prevent only slippage between the inner ring 8b, it is only necessary to provide the recess 8bc or the recess only on the outer periphery of the inner ring 8b.

Embodiment 4 FIG.
Next, Embodiment 4 will be described with reference to FIG.
The insulating ring 8 according to the fourth embodiment has an L-shaped bent portion 8dd (between the outer ring side surface of the rolling bearing 7 and the bracket 6 between the outer ring 8a and the inner ring 8b. Insulators 8e and 8c made of cast resin are provided between the outer ring 8a and the intermediate ring 8d, and between the intermediate ring 8d and the inner ring 8b, respectively. It is provided.
The insulator 8e of the insulating ring 8 is provided along the bent portion 8dd of the intermediate ring 8d so as to be interposed between the bent portion 8dd of the intermediate ring 8d and the bracket 6.
According to this embodiment, by forming a plurality of insulators, the combined electrostatic capacity of the insulating ring 8 can be reduced, and the circulating current can be suppressed with a small amount of casting resin.
The configuration described in the second and third embodiments can be applied to the insulating ring 8. In addition, two or more intermediate rings 8d may be provided as necessary to have a configuration of three or more layers.

  The insulating ring according to the present invention is used by being disposed between the bracket and the outer ring of the rolling bearing.

It is a longitudinal cross-sectional view of the rotary electric machine in Embodiment 1 of this invention. The insulating ring in Embodiment 1 of this invention is shown, (a) is a front view, (b) is an AA sectional view. The manufacturing method of the insulating ring in Embodiment 1 of this invention is shown, (a) is a front view, (b) is an AA sectional view. The insulating ring in Embodiment 2 of this invention is shown, (a) is a front view, (b) is an AA sectional view. The insulating ring in Embodiment 3 of this invention is shown, (a) is a front view, (b) is an AA sectional view. The insulating ring in Embodiment 4 of this invention is shown, (a) is a front view, (b) is an AA sectional view.

Explanation of symbols

  1 Rotating shaft, 2 Rotor core, 3 Stator, 4 Stator coil, 5 Frame, 6 Bracket, 7 Rolling bearing, 8 Insulating ring, 8a Outer ring, 8b Inner ring, 8c Insulator, 8ba Bent part, 8aa Recess, 8bb recess, 8ab recess, 8bc recess

Claims (8)

In the insulating ring interposed between the bracket of the rotating electrical machine and the outer ring of the rolling bearing that rotatably supports the rotor,
A metal outer ring,
A metal inner ring disposed coaxially in the outer ring with a predetermined gap therebetween;
The outer ring and the inner ring are interposed between the outer ring and the inner ring to electrically insulate them from each other and engage with a recess or a protrusion provided in the outer ring and / or the inner ring. An insulator composed of a casting resin that prevents sliding in the circumferential direction of
An insulating ring comprising: There is at least one metal intermediate ring disposed coaxially between the outer ring and the inner ring via a predetermined gap, and the insulators are respectively interposed in the gaps between the rings. The insulating ring according to claim 1. The insulating ring according to claim 2, wherein one or a plurality of concave portions or convex portions are provided on a surface of the intermediate ring that contacts the insulator. The insulating ring according to claim 1, wherein the inner ring has an abutting portion that abuts against an outer side surface of the outer ring of the rolling bearing. The insulating ring according to claim 4, wherein the insulator is provided to extend to a side surface of the bracket of the contact portion of the inner ring. The concave or convex portion, an insulating ring according to any one of claims 1 to 5, characterized in that provided extending in the axial direction of the ring. The said recessed part or convex part is provided in a part of said ring so as to prevent the ring from sliding in the circumferential direction and the axial direction with respect to the insulator . The insulation ring described in 1. A rotor,
A metal stator arranged with a predetermined gap outside the rotor;
A metal frame arranged outside the stator,
A metal bracket electrically connected to both ends of the frame;
In a rotating electrical machine comprising a rolling bearing in which inner and outer rings and rolling elements are made of metal, which rotatably supports the rotating shaft of the rotor with respect to the bracket,
A rotating electrical machine, wherein the insulating ring according to any one of claims 1 to 7 is disposed between the bracket and an outer ring of a rolling bearing.

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