JP2008121749A - Grease-prelubricated bearing for inverter driving motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease-prelubricated bearing for an inverter driving motor which is inexpensive and can effectively suppress damage caused by electric corrosion. <P>SOLUTION: The grease-prelubricated bearing 1 for the inverter driving motor comprises an inner ring 2, an outer ring 3 and a plurality of rollers 4 interposed between the inner and outer rings, and is also constituted by arranging seal members 6 for sealing grease 7 around the rollers 4 at axial both-end openings 8a, 8b. The grease 7 is produced by composing an additive containing at least a phosphate compound to base grease composed of base oil and a promoting agent, and a composition rate of the phosphate compound is 0.05 to 10 pts.wt. with respect to the base grease 100 pts.wt. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a grease-filled bearing for an inverter drive motor, and more particularly to a grease-filled bearing used for an inverter drive motor for industrial machinery or automotive electrical equipment.

  Electrical components and accessories in automobiles, motors in industrial machines, and the like are required to be downsized, high performance, and high output year by year, and usage conditions are becoming stricter. For these, sealed deep groove ball bearings are generally used, and are often used in inverter-controlled motors. The ratio of inverter motors is increasing due to convenience of inverter control (simplification of maintenance and inspection, speeding up, variable handling, etc.), and this increase is expected to continue. Inverter control adjusts voltage and frequency. Rolling bearings built into inverter-driven motors cause damage called "electric corrosion" that occurs when high-frequency current flows from the inverter circuit on the rolling surface. I may receive it.

In order to prevent such a problem from occurring, conventionally, it has been proposed to avoid damage due to electrolytic corrosion by forming and insulating the rolling elements constituting the bearing from ceramics (Patent Document 1 and Patent Document). 2).
However, ceramic bearings are very expensive and are not a general measure.
Japanese Patent No. 2991834 Japanese Patent No. 2934697

  The present invention has been made to cope with such problems, and an object of the present invention is to provide a grease-filled bearing for an inverter drive motor that is inexpensive and can effectively suppress damage due to electrolytic corrosion.

  A grease sealed bearing for an inverter drive motor of the present invention is a grease sealed bearing for an inverter drive motor that supports a rotor of an inverter drive motor driven by inverter control, and the grease sealed bearing includes an inner ring, an outer ring, A plurality of rolling elements interposed between the inner and outer rings, and seal members for sealing the grease sealed around the rolling elements are provided at both axial opening ends of the inner ring and the outer ring. Grease is composed of a base grease consisting of a base oil and a thickener and an additive containing at least a phosphate compound. The blending ratio of the phosphate compound is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. It is characterized by being.

  The phosphate compound is at least one phosphate ester selected from tricresyl phosphate, octyl phosphate, and triphenyl phosphate.

The thickener is a urea or lithium soap thickener.
The base oil is at least one oil selected from ester oils and poly-α-olefin oils.

  The grease-filled bearing for an inverter drive motor of the present invention is formed by sealing a base grease composed of a base oil and a thickener with a grease compounded with a phosphate compound such as a predetermined phosphate ester or metal phosphate. In addition, damage (electric corrosion) on the rolling surface caused by high-frequency current flowing from the inverter circuit is suppressed, and long-term use becomes possible. Further, since it is not necessary to use ceramics or the like as the bearing material, it can be obtained at a low cost.

An embodiment of the present invention will be described with reference to the drawings. An example of a grease-filled bearing for an inverter drive motor that supports a rotor of the motor is shown in FIG. 1A. FIG. 1A is a schematic cross-sectional view of a motor in which the motor bearing is used as an output motor bearing. FIG.1 (b) is the A section enlarged view of Fig.1 (a).
As shown in FIGS. 1A and 1B, the motor 10 rotates a load by attaching a belt 18 to a pulley 17 interlocked with the main shaft 11. The motor 10 has a rotor 13 attached to a main shaft 11, a pulley 17 attached to one end thereof, and a belt 18 that rotates an air conditioning fan or the like. The main shaft 11 is rotatably supported on the flange 14 by a first radial ball bearing 15 and a second radial ball bearing 16 (motor bearing) attached to both ends of the rotor 13. A stator 12 is fixed to the flange 14 so as to face the rotor 13. Further, a wave spring washer 19 is located between the flange 14 and the second radial ball bearing 16 to apply a preload.

In FIG. 1 (b), a preloading method using a spring is adopted, and a spring, a wave spring washer 19 and the like are positioned between the flange 14 and the second radial ball bearing 16 to apply preload. Is shown. The first radial ball bearing 15 and the second radial ball bearing 16 described above include an inner ring 2 as an inner member, an outer ring 3 as an outer member, and a plurality of balls 4 as rolling elements shown in FIG. , And a cage 5 that holds a plurality of balls 4. Note that the wave spring washer 19 is positioned between the flange 14 and the second radial ball bearing 16 to apply preload as described above. In addition, the center line passing through the center of the ball 4 is subjected to a radial load on the main shaft 11 by the belt 18, and the strain reaches the inner ring 2 of the bearing so that the load sharing of the ball 4 is inclined more than the vertical contact surface. It is in a state.
In the present embodiment, deep groove ball bearings are used as the first radial ball bearing 15 and the second radial ball bearing 16. In addition to the deep groove ball bearing, for example, an angular ball bearing or a cylindrical roller bearing can be used.

  FIG. 2 shows a cross-sectional view of the deep groove ball bearing. In the deep groove ball bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a. A plurality of rolling elements 4 are arranged between the two. Sealers 6 that are fixed to the cage 5, the outer ring 3, and the like that hold the plurality of rolling elements 4 are provided in the axially opposite end openings 8a, 8b of the inner ring 2 and the outer ring 3, respectively. A grease 7 containing a phosphoric acid compound described later as an additive is enclosed at least around the rolling element 4.

Examples of the phosphoric acid compound that can be used in the present invention include phosphoric acid esters and phosphoric acid metal salts. Specific examples of the phosphate ester include tricresyl phosphate (TCP), trioctyl phosphate (TOP), triphenyl phosphate (TPP), tributyl phosphate (TBP), phosphite, acidic phosphate, and the like. It is done. Specific examples of the metal phosphate include lithium phosphate and calcium phosphate. These phosphate compounds may be added to the grease alone or in combination of two or more.
Among these, it is preferable to use a phosphate ester because it has a high adsorptive power to the metal surface and can easily form a coating that can reduce wear due to electrolytic corrosion. Particularly preferred are tricresyl phosphate, trioctyl phosphate, and triphenyl phosphate because of excellent thermal stability.

  In the grease used in the present invention, a coating such as iron phosphate or iron phosphide is formed on the bearing rolling surface by blending the above phosphate compound as an additive. These coatings produced on the bearing rolling surface have the effect of reducing wear during energization and can prevent electrolytic corrosion.

  The blending ratio of the phosphoric acid compound is preferably 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease described later. More preferably, it is 0.1 to 5 parts by weight. When the blending ratio of the phosphoric acid compound is less than 0.05 parts by weight, wear due to electrolytic corrosion on the rolling surface cannot be sufficiently reduced. If the amount exceeds 10 parts by weight, abnormal wear occurs.

Base oils that can be used in the present invention include mineral oils such as spindle oil, refrigerator oil, turbine oil, machine oil, dynamo oil, highly refined mineral oil, liquid paraffin oil, polybutene oil, GTL oil synthesized by Fischer-Tropsch process, -Hydrocarbon synthetic oils such as α-olefin oil, alkylnaphthalene, and alicyclic compounds, or natural oils, polyol ester oils, phosphate ester oils, polymer ester oils, aromatic ester oils, carbonate ester oils, diester oils And non-hydrocarbon synthetic oils such as polyglycol oil, silicone oil, polyphenyl ether oil, alkyldiphenyl ether oil, alkylbenzene oil, and fluorinated oil. These base oils can be used alone or in combination of two or more.
Among these, it is preferable to use ester oils and poly-α-olefin oils excellent in heat resistance, lubricity and low noise.

Thickeners that can be used in the present invention include benton, silica gel, fluorine compounds, lithium soap, lithium complex soap, strong lucium soap, calcium complex soap, aluminum soap, aluminum complex soap, and other soaps, diurea compounds, polyurea compounds, etc. These urea compounds are mentioned.
Among these, considering low noise properties, heat resistance, cost, etc., a urea-based or lithium soap compound is desirable, and a urea-based compound is more desirable.

  A urea compound is obtained by reacting an isocyanate compound and an amine compound. In order not to leave a reactive free radical, the isocyanate group of the isocyanate compound and the amino group of the amine compound are preferably blended so as to be approximately equivalent.

  A diurea compound is obtained by reaction of a diisocyanate and a monoamine, for example. Examples of the diisocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc., and monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, Examples include oleylamine, aniline, p-toluidine, cyclohexylamine and the like. The polyurea compound can be obtained, for example, by reacting diisocyanate with a monoamine or diamine. Examples of the diisocyanate and monoamine include those similar to those used for the production of the diurea compound. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, And diaminodiphenylmethane.

By adding a thickener such as a urea compound to the base oil, a base grease for blending the phosphoric acid compound can be obtained. A base grease using a urea compound as a thickener is prepared by reacting an isocyanate compound and an amine compound in a base oil.
The blending ratio of the thickener in 100 parts by weight of the base grease is 1 part by weight to 40 parts by weight, preferably 3 parts by weight to 25 parts by weight. If the content of the thickener is less than 1 part by weight, the thickening effect will be reduced, making it difficult to make grease, and if it exceeds 40 parts by weight, the resulting base grease will be too hard and the desired effect will not be obtained. Become.

  In the present invention, a known grease additive may be contained together with the phosphoric acid compound, if necessary. Examples of the additives include antioxidants such as organic zinc compounds, amines, and phenolic compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, molybdenum disulfide, and graphite. Examples thereof include solid lubricants, metal sulfonates, antirust agents such as polyhydric alcohol esters, friction reducing agents such as organic molybdenum, and oily agents such as esters and alcohols. These can be added alone or in combination of two or more.

  Since the grease used in the present invention can suppress wear due to electrolytic corrosion, the life of the grease-sealed bearing for the inverter drive motor can be improved. For this reason, ball bearings, cylindrical roller bearings, tapered roller bearings, spherical roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust spherical roller bearings, etc. Can be used as grease.

Examples 1 to 6 and Comparative Examples 1 to 3
In half of the base oil shown in Table 1, 4,4-diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MT, hereinafter referred to as MDI) is dissolved in the ratio shown in Table 1 and dissolved in the remaining half of the base oil A monoamine that was twice the equivalent of MDI was dissolved. The respective blending ratios and types are shown in Table 1.
A solution in which monoamine was dissolved was added while stirring the solution in which MDI was dissolved, and then the reaction was continued for 30 minutes at 100 ° C. to 120 ° C. to produce a diurea compound in the base oil.
Phosphoric acid ester and antioxidant were added to this at the blending ratio shown in Table 1, and the mixture was further stirred at 100 to 120 ° C. for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease.

  The obtained grease was subjected to a rapid acceleration / deceleration test. Test methods and test conditions are shown below. The results are shown in Table 1.

<Acoustic measurement>
Rolling ball bearings (bearing dimensions: φ8 x φ22 x 7 (mm)) filled with 0.1 g of the grease shown in Table 1 are prepared. An axial load of 7.8 N is applied to this bearing, and it is run at 1800 rpm for 30 seconds. The value G (RMS value) was measured. Three-stage evaluation was performed as follows.
◎: Vibration value is less than 25 mG ○: Vibration value is less than 50 mG ×: Vibration value is 50 mG or more

<Electrical wear test>
1 g of the grease obtained in each example was sealed in a rolling bearing (51106) and rotated at 2600 rpm at room temperature under an axial load of 1450 N with a current of 2 A applied between the outer and inner rings. 24 hours later, the amount of wear of the inner and outer rings due to electrolytic corrosion was measured by the weight loss. Three-stage evaluation was performed as follows.
◎: Wear amount is less than 1 mg ○: Wear amount is less than 2 mg ×: Wear amount is 2 mg or more

  As shown in Table 1, each example was able to effectively prevent electrolytic corrosion generated on the rolling surface of the rolling bearing.

  The grease-sealed bearing for the inverter drive motor of the present invention encloses a grease containing a phosphoric acid compound as an additive in a base grease composed of a base oil and a thickener, so that a high-frequency current flows from the inverter circuit. The damage (electric corrosion) caused by this can be suppressed, and it can be used for a long time. For this reason, it can utilize suitably as a bearing used for a motor of inverter control.

(A) It is a schematic sectional drawing of the motor which used the bearing for motors for the bearing for output motors. (B) It is the A section enlarged view of (a). It is sectional drawing of a deep groove ball bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Grease-sealed bearing for inverter drive motors 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease 8a Opening 8b Opening 10 Motor 11 Motor spindle 12 Stator 13 Rotor (rotor)
14 Flange 15 First ball bearing 16 Second ball bearing 17 Pulley 18 Belt 19 Wave spring washer

Claims (4)

A grease sealed bearing for an inverter drive motor that supports a rotor of an inverter drive motor driven by inverter control, wherein the grease sealed bearing includes an inner ring, an outer ring, and a plurality of rolling elements interposed between the inner and outer rings. Provided with seal members for sealing grease around the rolling elements at both ends in the axial direction of the inner ring and the outer ring,
The grease comprises a base grease composed of a base oil and a thickener and an additive containing at least a phosphoric acid compound. The phosphoric acid compound is mixed in an amount of 0.05 to 10% by weight with respect to 100 parts by weight of the base grease. A grease-filled bearing for an inverter drive motor characterized by being a part.   The grease-filled bearing for an inverter drive motor according to claim 1, wherein the phosphate compound is at least one phosphate ester selected from tricresyl phosphate, trioctyl phosphate, and triphenyl phosphate.   The grease-enclosed bearing for an inverter drive motor according to claim 1, wherein the thickener is a urea-based or lithium soap-based thickener.   4. The grease-sealed bearing for an inverter drive motor according to claim 1, wherein the base oil is at least one oil selected from ester oil and poly-α-olefin oil.

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