JP2006153186A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing preventing electro-erosion even when used in a motor generating shaft voltage. <P>SOLUTION: There is provided the rolling bearing in which one of a steel inner ring 2, a steel outer ring 3 and steel balls (rolling elements) 4 is made of steel having a rate of carbon content of 0.20 mass% or less. The rolling bearing with all of the inner ring 2, the outer ring 3 and the balls (rolling elements) 4 made of SUJ2 is used for 100 hours in a state that an electric current passes in the bearing. Elementary analysis of rolling surfaces of the rolling elements is then performed in depth directions and it is found that carbide layers are formed in the surfaces of the rolling elements. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing.

The rotor shaft of the motor is rotatably supported with respect to the housing by a rolling bearing. A rolling bearing normally used for supporting a rotor shaft of a motor includes an inner ring, an outer ring, and a rolling element made of SUJ2 (high carbon chromium bearing steel type 2). The carbon content of SUJ2 is 0.95 to 1.10% by mass.
A motor used near an apparatus that generates a high-frequency current, such as an inverter control motor or high-speed switching, may generate a shaft voltage and cause a potential difference between the rotor shaft and the housing. Along with this, leakage current from the housing and the rotor shaft flows between the rolling elements of the rolling bearing and the raceway, and electrolytic corrosion (electrochemical corrosion) occurs on the raceway surface of the raceway and the rolling surface of the rolling element. May occur (see, for example, Non-Patent Document 1). When this electrolytic corrosion occurs, the accuracy of the raceway surface of the raceway and the rolling surface of the rolling element is lowered, the vibration is increased, and the life of the bearing is shortened.

In order to prevent this electrolytic corrosion, it has been proposed to coat the raceway surface of the raceway with an insulating coating (see, for example, Patent Documents 1 and 2). It has also been proposed to prevent electrolytic corrosion by circuit design (see, for example, Non-Patent Document 2).
Seiji Ogasawara, “Leakage current, surge voltage, shaft voltage and its suppression method of variable speed AC drive”, D. D, 1998, 188, 9, p. 975-980 Ogasawara et al., “Active Cancellation of Common Mode Voltage Generated by Voltage-Type PWM Inverter”, Electron Theory D, 1997, Vol. 117, No. 5, p. 565-571 JP 7-310748 A JP 2002-147468 A

However, since the shaft voltage due to the high-frequency current is an induced current, it is not possible to expect an effect by the method of providing an insulating film in the above prior art. Further, the method of preventing electrolytic corrosion by circuit design is not practical because it requires complicated circuit design and high cost.
The present invention has been made to solve such an unsolved problem of the prior art, and provides a rolling bearing capable of preventing electrolytic corrosion even when used in a motor that generates shaft voltage. Objective.

In order to solve the above-mentioned problems, the present invention provides a rolling bearing comprising a steel inner ring, outer ring, and rolling element, wherein any of the inner ring, outer ring, and rolling element has a carbon content of 0.20% by mass. Provided is a rolling bearing made of the following steel.
The rolling bearing of the present invention is suitably used for supporting the shaft of an inverter control motor.
After using a rolling bearing in which all of the inner ring, outer ring, and rolling element are made of SUJ2 for 100 hours in a state where current flows in the bearing, elemental analysis of the rolling surface of the rolling element in the depth direction was performed. The graph shown in FIG. 1 was obtained. This graph shows the relationship between Auger electron intensity and sputtering time (proportional to depth from the surface). From this result, it can be seen that a carbide layer is formed on the surface of the rolling element.

  For the analysis, a scanning Auger electron spectrometer “SAM650” manufactured by ULVAC-PHI Co., Ltd. was used. Argon ion irradiation angle: 30 degrees. The analyzer was calibrated using tantalum oxide. That is, the sputtering rate was measured by sputtering a standard piece of tantalum oxide to a depth of 25 nm. The depth of the carbide layer converted from the sputtering time using this measured value (4.00 nm / min) is about 100 nm.

That is, it can be seen that when the rolling bearing having the above configuration is used in a state where a current flows in the bearing, a carbide layer is formed on the surface by the energy when the current passes through the bearing. And by forming such a carbide | carbonized_material nonuniformly, the precision of the raceway surface of a bearing ring and the rolling surface of a rolling element falls, a vibration rises, and the lifetime of a bearing becomes short.
On the other hand, in the rolling bearing of the present invention, the current flows in the rolling bearing by setting the carbon content of the steel forming any of the inner ring, the outer ring, and the rolling element to 0.20% by mass or less. Even in this case, the carbide layer is hardly formed.

  According to the rolling bearing of the present invention, even when used in a motor that generates shaft voltage, electrolytic corrosion is prevented, and good performance can be maintained over a long period of time.

Hereinafter, embodiments of the present invention will be described.
FIG. 2 is a cross-sectional view showing a rolling bearing corresponding to an embodiment of the present invention.
This rolling bearing 1 is a single-row deep groove ball bearing having an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm, an inner ring 2, an outer ring 3, a ball (rolling element) 4, and a crown-shaped cage 5 made of polyamide resin. And a non-contact rubber seal 6 containing a cored bar.

A raceway groove 2a is formed on the outer peripheral surface of the inner ring 2, and a raceway groove 3a is formed on the inner peripheral surface of the outer ring. These raceway grooves 2a and 3a are arranged to face each other, and a ball 4 is arranged so as to be able to roll through a cage 5 therebetween. The diameter of the ball 4 is 3.969 mm.
As materials for producing the inner ring 2, the outer ring 3, and the balls 4, materials made of 12 types of steel shown in Table 1 were prepared. Table 1 shows the carbon content of each steel. After making these materials into a predetermined shape by cutting, the inner ring 2, the outer ring 3, and the balls 4 made of various steels were manufactured by performing an optimum heat treatment for each steel. These were combined to assemble No. 1 to 17 rolling bearings shown in Table 2 below.

Further, grease was sealed in each rolling bearing so that the occupied volume ratio was 15%. The grease used is a grease with a base oil of polyalphaolefin having a kinematic viscosity at 40 ° C. of 32 mm ² / s and a thickening agent of Li stearate having a consistency of No. 3 of “JIS K2220”. is there.

For the rolling bearings of Nos. 1 to 17, a rotation test using the test apparatus of FIG. 3 was performed.
This test apparatus rotates while energizing the test bearing 70, and includes a motor 71, an insulating coupling 72, a resin housing 73, a power supply screw 74, and a brush 75. . Further, before and after the rotation test, an amount (anderon value) indicating acoustic characteristics was measured using an andrometer.
<Test conditions>
Rotation speed: 1800min ^-1 (inner ring rotation)
Axial load: 20N
Current applied to the bearing: 2 mA
Atmospheric temperature: Room temperature Rotation time: 100 hours

  From the obtained results, the increase in the Anderon value after 100 hours of rotation was calculated for each sample with respect to the Anderon value before rotation (initial sound). FIG. 4 is a graph showing the relationship between the increase in the Anderon value of each rolling bearing and the “minimum carbon content”. “Minimum carbon content” means the carbon content of the steel having the smallest carbon content among the steels forming the inner ring, the outer ring, and the balls in each rolling bearing.

  In No. 1-14 and No. 16, 17, any two of the inner ring, the outer ring, and the ball are made of SUJ2, and the remaining one is made of steel other than SUJ2. No. 15 is all made of SUJ2. Therefore, the “minimum carbon content” of Nos. 1 to 14 and Nos. 16 and 17 is the carbon content of steel forming bearing parts other than SUJ2, and the “minimum carbon content” of No. 15 is This is the carbon content of SUJ2.

As can be seen from the graph of FIG. 4, any one of the inner ring, the outer ring, and the ball is made of steel having a carbon content of 0.20% by mass or less, and the other is made of SUJ2. No. 8-17 rolling with any one of inner ring, outer ring and ball made of steel with a carbon content of over 0.20% by mass and the other made of SUJ2 or made entirely of SUJ2. Compared to the bearing, the increase in the Anderon value can be significantly reduced.
Therefore, when the rolling bearings of Nos. 1 to 7 corresponding to the examples of the present invention are used in a motor in which shaft voltage is generated as compared with the rolling bearings of Nos. 8 to 17 corresponding to the comparative examples. But it can be a long life.

It is a graph showing the result of elemental analysis in the depth direction of the rolling surface of the rolling element used in the state where current flows in the bearing, and the Auger electron intensity and sputtering time (proportional to the depth from the surface) The relationship is shown. It is sectional drawing which shows the rolling bearing corresponded to one Embodiment of this invention. It is a figure which shows the electricity rotation test apparatus used in embodiment. It is a graph which shows the relationship between the increase amount of the Anderon value of each rolling bearing, and the "minimum carbon content rate" obtained by embodiment.

Explanation of symbols

1 Rolling bearing 2 Inner ring 3 Outer ring 4 Ball (rolling element)
5 Crown-shaped cage made of polyamide resin 6 Non-contact rubber seal 70 Test bearing 71 Motor 72 Insulating coupling 73 Resin housing 74 Feed screw 75 Brush

Claims (2)

  A rolling bearing comprising a steel inner ring, outer ring, and rolling element, wherein the inner ring, outer ring, or rolling element is made of steel having a carbon content of 0.20 mass% or less. .   The rolling bearing according to claim 1, which is used for supporting a shaft of an inverter control motor.

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