JP6334745B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a rolling bearing.

An inverter refers to a device or a part of a device that converts DC power into AC voltage. Battery power AC converters, DC electric railway inverters, etc. In Japan, on the other hand, in order to obtain alternating currents with different numbers of phases, voltages, and frequencies, single-phase alternating currents and three alternating currents of commercial power are temporarily converted to direct current with a rectifier and then converted into alternating current (converters). ) And an inverter, and the entire power conversion device housed in the same package is often called an inverter. Elevators, pumps, fans, rail cars, electric cars, air conditioners, refrigerators, factories and other equipment used, backup power supplies such as servers and personal computers, automotive inverters that use household 100V equipment with automotive 12V power supplies, solar It is possible to control the output of various electrical devices from home appliances to large equipment such as power conditioners in photovoltaic power generation.
Conventionally, a metal of bearing steel (SUJ2 or the like) has been used for a bearing (bearing) member close to the inverter, particularly a bearing ball.

On the other hand, since the inverter controls the inverter control circuit using a high-frequency current, an EDM current (a current that destroys the metal surface due to a discharge phenomenon) and a high-frequency circulating current are easily generated. In particular, a metal such as bearing steel causes a phenomenon called electrolytic corrosion, which reduces the bearing life and cannot provide a reliable rotational drive.
In order to solve such problems, attempts have been made in recent years to ground the motor shaft or to attach a metal that shields electromagnetic noise to the outer periphery of the motor. For example, in Japanese Patent Application Laid-Open No. 2006-328273 (Patent Document 1), a conductive grease is filled in a bearing to obtain a grounding effect. However, the conductive grease has problems such as aging and liquid leakage.

JP 2006-328273 A

However, both had to attach some accessories to the bearing or motor. The attachment of the accessories increases the work process, making the manufacturing process complicated.
The present invention has been made to solve the above-described problems, and is used in the vicinity of an inverter that suppresses the occurrence of an electrolytic corrosion phenomenon by generating an EMD current or a high-frequency circulating current in an inverter driven at 50 Hz or higher. A bearing is provided. Moreover, since generation | occurrence | production of the electrolytic corrosion phenomenon is suppressed, the reliability of an inverter and the electric equipment using the same can also be improved.

One embodiment of the present invention is a rolling bearing that is used at a position within 1 m from a control circuit that controls the drive frequency of an inverter motor to 50 Hz or more and 4000 Hz or less, and has an electrical resistance value of 10 ¹⁰ Ω · cm or more. The number of the rolling elements including the rolling element is P (number), the maximum number of rotations in the usage environment of the rolling bearing is M (rpm), and the drive frequency of the inverter motor is F ( Hz), it is a rolling bearing that satisfies P × M ≧ 60F. The electrical equipment provided with the rolling bearing is preferably any one of equipment used in factories, servers, personal computers, elevators, pumps, fans, home appliances, electric vehicles, and railway vehicles.

According to the present invention, in the bearing used in the vicinity of the inverter, since a plurality of rolling elements having an electric resistance value of 10 ⁷ Ω · cm or more are used, generation of EMD current and high-frequency circulating current can be suppressed. . Therefore, even if the inverter control circuit is driven by a current having a drive frequency of 50 Hz or more, there is no need to attach a member for obtaining the ground effect. As a result, the assembly process of the bearing and the motor can be simplified, and the reliability of the motor can be improved.

The figure which shows an example of the bearing of this invention.

The rolling bearing used in the vicinity of the inverter of the present invention is an inverter that operates at a frequency of 50 Hz or more. The rolling bearing has a plurality of rolling elements, and at least one rolling element has an electrical resistance by insulating ceramics or insulating coating. The value is 10 ⁷ Ω · cm or more.
The inverter has an inverter control circuit that converts direct current into alternating current. In alternating current, plus and minus change periodically, and this periodic change becomes the frequency. The inverter is a method for controlling the rotation speed in accordance with a change in frequency. Compared with the method of controlling the rotation speed by combining a plurality of gears, it is possible to reduce the weight because a complicated component such as a gear change is not required.

The greater the frequency of the inverter, the faster the plus / minus change speed. When this plus / minus change occurs, electromagnetic induction occurs around the inverter control circuit. This electromagnetic induction is transmitted to the inside of the bearing through conductors such as metal parts. The transmitted electromagnetic induction becomes EMD current or / and high frequency circulating current. When an EMD current or / and a high-frequency circulating current are generated, they are also transmitted to the rotating shaft and rolling elements (bearing balls) used in the bearing. At this time, if the rotating shaft and the rolling element are conductive members such as bearing steel (SUJ2), an electrolytic corrosion phenomenon occurs due to the EMD current or / and the high-frequency circulating current. Due to the galvanic phenomenon, the rotating shaft or the rolling element is corroded, and uniform rotating motion cannot be maintained. In particular, the electrolytic corrosion phenomenon was likely to occur in the bearing used in the vicinity of the inverter having an operating frequency of 50 Hz or more.
In contrast, in the present invention, among a plurality of rolling elements used in a bearing used in the vicinity of the inverter, at least one of the rolling elements has an electrical resistance value of 10 ⁷ Ω · cm or more by insulating ceramics or insulating coating. Something is used.
Further, the number of electrical resistance 10 ⁷ Ω · cm or more rolling elements may the more, it is preferable that all the rolling elements is electrical resistance 10 ⁷ Ω · cm or more. The electrical resistance value is preferably 10 ¹⁰ Ω · cm or more. In addition, the electrical resistance value is measured with an electrical resistance measuring device by a two-terminal method.

By using an insulating rolling element having an electric resistance value of 10 ⁷ Ω · cm or more, it is possible to prevent the EMD current or / and the high-frequency circulating current from being transmitted to the rotating shaft and the rolling element.
Examples of such rolling elements having insulating properties include those containing at least one selected from aluminum oxide, zirconium oxide, silicon nitride, silicon oxide, fluorine resin, and engineering resin as a main component.
Examples of the ceramic mainly composed of at least one of aluminum oxide, zirconium oxide, silicon nitride, and silicon oxide include a sintered ceramic body obtained by adding a sintering aid as necessary. Moreover, the ceramic sintered bodies of aluminum oxide, zirconium oxide, silicon nitride, and silicon oxide are all insulators (insulating ceramic sintered bodies) having an electric resistance value of 10 ⁷ Ω · cm or more. A sintering aid is selected so as not to lower the insulation. Of the ceramic sintered bodies, a silicon nitride sintered body using yttrium oxide as a sintering aid is preferable because of its excellent sliding characteristics.

Further, as the rolling element having an electric resistance value of 10 ⁷ Ω · cm or more, at least one sprayed film selected from zirconium oxide, silicon nitride, silicon oxide, chromium oxide, fluorine resin, and engineering resin is formed on the surface of the metal member. The thing which gave is also mentioned.
In the metal member, the electrolytic corrosion phenomenon occurs as described above, but by providing an insulating sprayed film, it is possible to maintain the same insulating property as the insulating ceramic sintered body. The thickness of the sprayed film is preferably in the range of 2 to 300 μm. If the film thickness of the sprayed film is less than 2 μm, film sag may occur, and if it exceeds 300 μm, no further effect can be obtained. Moreover, since these sprayed films are well compatible with the bearing steel (SUJ2), excellent bonding strength can be obtained.

When the insulating ceramic sintered body and the insulating sprayed film are compared, the manufacturing process is complicated because the sprayed film requires a film forming process. Further, uniform control of the film thickness is necessary. Accordingly, a rolling element made of an insulating ceramic sintered body is preferred.
FIG. 1 shows an example of a bearing. In the figure, 1 is a bearing, 2 is a rolling element (bearing ball), 3 is an inner ring, and 4 is an outer ring. The inner ring is fixed to the rotating shaft and functions as a bearing. Further, the outer ring, the inner ring, and the rotating shaft are made of bearing steel (SUJ2).
Usually, 8 to 20 rolling elements are used in the bearing. If at least one rolling element having insulating properties as described above is used, electrolytic corrosion can be suppressed in a bearing used in the vicinity of the inverter operating at 50 Hz or higher.
In addition, regarding the number of rolling elements to be insulated, the number of rolling elements having an electric resistance value of 10 ⁷ Ω · cm or more is P (number), and the rotation speed of the bearing is M (rpm It is preferable that P × M ≧ 60F is satisfied when the drive frequency of the inverter is F (Hz). In addition, the rotation speed M (rpm) of a bearing is the maximum rotation speed in a use environment.

In the present invention, it is preferable to use all of the rolling elements having an insulating property with an electric resistance value of 10 ⁷ Ω · cm or more. However, the insulating rolling elements are more expensive than those made of bearing steel (SUJ2). Therefore, replacing some of the plurality of rolling elements with bearing steel rolling elements is effective in reducing costs. At this time, electrolytic corrosion can be effectively suppressed as long as P × M ≧ 60F.
For example, when the rotational speed M of the bearing is 5000 rpm and the drive frequency F of the inverter is 200 Hz, P × 5000 ≧ 60 × 200, P ≧ 2.4, so that three or more have an electric resistance value of 10 ⁷ Ω · cm or more. In this way, electric corrosion can be effectively prevented.

The number of rolling elements (bearing balls) mounted on the bearing is arbitrary, but is usually in the range of 8-20. For example, when the drive frequency is 3000 Hz and the rotational speed is 5000 rpm, P × M ≧ 60F → P × 5000 ≧ 60 × 3000 → P ≧ 36. When the P value is equal to or greater than the number of rolling elements, all the rolling elements are electrically An insulating rolling element having a resistance value of 10 ⁷ Ω · cm or more is used.

In addition, when electrolytic corrosion occurs, a portion in contact with the rolling element such as the inner ring or the rotating shaft, or the rolling element itself is scraped off. As a result, stable rotational motion cannot be provided. In addition, a method of measuring sound during rotation is effective for determining whether or not the rotational motion is stable. For example, if the sliding sound at a constant rotational speed is eroded, the sliding sound increases.
Moreover, it is preferable that the drive frequency of an inverter is 4000 Hz or less. It is possible to effectively prevent electrolytic corrosion by using an insulating rolling element, but if the frequency becomes too high, the insulating effect of the rolling element alone may cause insufficient electrolytic corrosion suppression effect. . Therefore, when using an insulating rolling element, it is suitable for a bearing used in the vicinity of an inverter having a drive frequency of 50 to 4000 Hz. More preferably, it is 50-1000 Hz.

  The inverter is configured by combining such a bearing and a control circuit. Examples of the control circuit include an AC / DC converter, an inverter control circuit, a thyristor as a switching element, and an IGBT element. As the inverter control circuit, PWN (pulse width modulation) driving is generally used. Since the inverter bearing of the present invention suppresses the occurrence of electrolytic corrosion, even if the inverter control circuit and the bearing are installed in the vicinity of, for example, 1 m or less, they are hardly affected by electrolytic corrosion. Therefore, there is no restriction due to the arrangement of the control circuit and the bearing. Therefore, it can be applied in the vicinity of inverters of various electric appliances such as electric appliances and railway vehicles from home appliances such as air conditioners and washing machines. In other words, a highly reliable electric appliance that is not affected by electric corrosion can be provided. The vicinity within 1 m includes both the bearing of the inverter motor and the bearing arranged near the inverter motor.

Hereinafter, embodiments of the present invention will be described with reference to examples.
(Examples 1-4, Comparative Example 1)
An inverter bearing in which eight rolling elements (bearing balls) having a diameter of 1 cm were incorporated in the inner ring (inner diameter 5 cm) and the outer ring (outer diameter 8 cm) was manufactured. The inner ring and the outer ring were made of bearing steel (SUJ2).
As rolling elements, SUJ2 spheres (electrical resistance value 10 ⁴ Ω · cm) and silicon nitride sintered spheres (electrical resistance value 10 ¹² Ω · cm or more) were prepared and used at the ratios shown in Table 1. .
Such inverter bearings were incorporated into an inverter motor to produce an inverter motor for electrical equipment. The electric corrosion test of each inverter motor was conducted. The bearing was built into the inverter motor (the inverter and the bearing were placed within 1m).
In the measurement of electric corrosion of the inverter motor, the sound intensity is measured with a microphone (pickup sensor) when operated continuously for 400 hours at a rotation speed of 7000 rpm on the outer ring side at a frequency of 100 Hz, and the sensor output exceeds 30 dB. The vibration was “present”, the vibration was more than 25 dB and 30 dB or less was vibration “somewhat”, and the vibration was “less” when less than 25 dB. Note that the sliding noise after 1 hour of motor operation was less than 25 dB. The measurement results are shown in Table 1.

  As can be seen from Table 1, when the rolling bearing of this example was used, it was confirmed that vibration was suppressed to a low level and no electrolytic corrosion occurred. In the bearing according to the embodiment, P × M ≧ 60F, and P × 7000 ≧ 60 × 100 to P ≧ 0.9. Therefore, electrolytic corrosion was prevented in any case where one or more insulating rolling elements were used.

(Examples 5 to 8, Comparative Example 2)
An inverter motor bearing in which 12 rolling elements (bearing balls) having a diameter of 1 cm were incorporated in the inner ring (inner diameter: 8 cm) and the outer ring (outer diameter: 10 cm) was manufactured. The inner ring and the outer ring were made of bearing steel (SUJ2).
As the rolling elements, SUJ2 spheres (electric resistance value 10 ⁴ Ω · cm) and silicon nitride sintered spheres (electric resistance value 10 ¹² Ω · cm or more) were prepared and used at the ratios shown in Table 2. .
Next, an inverter motor similar to that of Example 1 was manufactured except that the drive frequency of the inverter motor was changed to 800 Hz and the rotation speed was changed to 8000 rpm. Similarly, the presence or absence of electrolytic corrosion was confirmed by the presence or absence of an increase in vibration. The bearing was built into the inverter motor (the inverter and the bearing were placed within 1 m). The results are shown in Table 2.

  As can be seen from the table, P × M ≧ 60F, P × 8000 ≧ 60 × 8000, and P ≧ 6. Although electric corrosion was not confirmed in Examples 6 to 8 satisfying this condition, it was slightly present in Example 5 that did not satisfy this condition.

(Examples 9 to 12)
In Example 1, the same measurement was performed using an insulating rolling element having an electric resistance value of 10 ¹⁰ Ω · cm or more in which an aluminum oxide sprayed film (film thickness: 3 μm) was provided on SUJ2. In addition, the inverter motor and the bearing were arrange | positioned within 1 m. The results are shown in Table 3.

Even an insulating rolling element having an electric resistance value of 10 ¹⁰ Ω · cm could be effectively utilized.

(Examples 13 to 15)
A silicon nitride sintered body (electric resistance value of 10 ¹² Ω · cm or more) was applied in Example 13, an engineering resin (electric resistance value of 10 ¹³ Ω · cm) was applied in Example 14, and a chromium oxide sprayed film (film thickness: 100 μm) was applied. An inverter bearing was constructed under the conditions shown in Table 4 using SUJ2 spheres (electric resistance value of 10 ⁸ Ω · cm or more) as Example 15, and the presence or absence of electrolytic corrosion was measured in the same manner as in Example 1. The diameter of the rolling elements was unified to 1 cm, and the total number of rolling elements used was 16 pieces. In addition, the inverter motor and the bearing were arrange | positioned within 1 m. The results are shown in Table 4.

  From P × M ≧ 60F, Example 13 is P ≧ 36, Example 14 is P ≧ 20, and Example 15 is P ≧ 40. All of them had to be insulating rolling elements because the P value was larger than the total number of rolling elements.

1 ... Bearing 2 ... Rolling element (bearing ball)
3 ... Inner ring 4 ... Outer ring

Claims (10)

A rolling bearing used at a position within 1 m from a control circuit that controls the drive frequency of the inverter motor to 50 Hz or more and 4000 Hz or less,
A plurality of rolling elements including an insulating rolling element having an electric resistance value of 10 ¹⁰ Ω · cm or more;
When the number of the insulating rolling elements is P (pieces), the maximum rotation speed in the usage environment of the rolling bearing is M (rpm), and the drive frequency of the inverter motor is F (Hz), P × M ≧ Rolling bearing that satisfies 60F. 2. The rolling bearing according to claim 1 , wherein the insulating rolling element includes at least one selected from aluminum oxide, zirconium oxide, silicon nitride, silicon oxide, a fluororesin, and an engineering resin as a main component. 2. The rolling bearing according to claim 1 , wherein the insulating rolling element is a ceramic sintered body containing as a main component at least one selected from aluminum oxide, zirconium oxide, silicon nitride, and silicon oxide. The rolling bearing according to claim 1 , wherein the insulating rolling element is a silicon nitride sintered body containing a rare earth oxide. The insulating rolling element has a metal member and a sprayed coating provided on the surface of the metal member,
2. The rolling bearing according to claim 1 , wherein the sprayed film contains at least one selected from zirconium oxide, silicon nitride, silicon oxide, chromium oxide, fluororesin, and engineering resin as a main component. The rolling bearing according to claim 5 , wherein the sprayed film has a thickness of 2 μm or more and 300 μm or less. The rolling bearing according to any one of claims 1 to 6 , wherein an electric resistance value of the insulating rolling element is 10 ¹² Ω · cm or more. The rolling bearing according to any one of claims 1 to 7 , wherein the number of the insulating rolling elements is less than the number of the plurality of rolling elements. The rolling bearing according to any one of claims 1 to 8 , wherein the rolling bearing is used at a position within 1 m from a control circuit that controls a drive frequency of the inverter motor to 50 Hz or more and 1000 Hz or less. The rolling bearing factory equipment, servers, personal computers, elevators, pumps, fans, household appliances, is provided on at least one of the electric vehicles and rail vehicles, any of claims 1 to 9 A rolling bearing according to claim 1.

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