JP6841946B2 - How to use electrical equipment - Google Patents

Description

The present invention relates to rolling bearings.

An inverter is a device that converts DC power into AC voltage, or a part of the device is called an inverter. Battery-powered AC converters, DC electric railway inverters, etc. On the other hand, in Japan, in order to obtain alternating current with different numbers of phases, voltage, and frequency, a rectifier (converter) for converting single-phase alternating current and three alternating current of a commercial power supply to direct current with a rectifier and then converting it to alternating current again. ) And an inverter are combined and the entire power converter housed in the same package is often called an inverter. Elevators, pumps, fans, railroad vehicles, electric vehicles, air conditioners, equipment used such as refrigerators and factories, backup power supplies such as servers and personal computers, in-vehicle inverters that use household 100V equipment with 12V power supply for automobiles, solar power It is possible to control the output of various electric devices from home appliances such as power conditioners in photovoltaic power generation to large equipment.
Conventionally, a metal of bearing steel (SUJ2 or the like) has been used for a bearing member close to an inverter, particularly for 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 likely to be generated. In particular, in metals such as bearing steel, a phenomenon called electrolytic corrosion occurs and the bearing life is shortened, making it impossible to provide a reliable rotary drive.
In recent years, in order to solve such a problem, attempts have been made to ground the shaft of the motor or to attach a metal that shields electromagnetic noise to the outer circumference 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.

Japanese Unexamined Patent Publication No. 2006-328273

However, both required some accessories to be attached to the bearings or motors. Since the installation of accessories increases the work process, the manufacturing process is complicated.
The present invention has been made to solve the above-mentioned problems, and is used in the vicinity of an inverter driven at 50 Hz or higher, in which the occurrence of electrolytic corrosion phenomenon is suppressed by the generation of EMD current or high-frequency circulating current. It provides a bearing. Further, since the occurrence of the electrolytic corrosion phenomenon is suppressed, the reliability of the inverter and the electric device using the inverter can be improved.

One aspect of the present invention is a method of using an electric device including an inverter motor, in which the electric device is installed with a control circuit for controlling the drive frequency of the inverter motor to 50 Hz or more and 2000 Hz or less, and within 1 m from the control circuit. The rolling bearing includes an inner ring made of SUJ2 material, an outer ring made of SUJ2 material, and an insulating bearing ball containing insulating ceramics and having an electric resistance value of 10 ¹⁰ Ω · cm or more. including, comprising: a plurality of bearing balls, the number of P (number) of an insulating bearing balls, the maximum rotational speed M (rpm), the driving frequency of the inverter motor F (Hz at rolling bearings use environment ), The occurrence of electrolytic corrosion is suppressed by satisfying P × M ≧ 60F and P being an integer of 6 or more. The electrical equipment is preferably any one of equipment used in factories, servers, personal computers, elevators, pumps, fans, home appliances, electric vehicles, and railroad vehicles.

According to the present invention, in the bearing used in the inverter vicinity, because of the use of more than the electrical resistance of 10 ⁷ Ω · cm in a plurality of rolling elements, it is possible to suppress the occurrence of the EMD current and high-frequency circulating current .. Therefore, even if the inverter control circuit is driven by a current having a drive frequency of 50 Hz or higher, it is not necessary 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 also 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 operating at a frequency of 50 Hz or higher. The rolling bearing has a plurality of rolling elements, and at least one rolling element has electrical resistance due to insulating ceramics or an insulating coating. is characterized in that the value is obtained by a 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 of controlling the rotation speed according to a change in frequency. Compared to the method of controlling the number of revolutions by combining a plurality of gears, the weight can be reduced because complicated components such as gear changes are not required.

The higher the frequency of the inverter, the faster the speed of change of plus or minus. At the time of this plus or minus change, electromagnetic induction occurs around the inverter control circuit. This electromagnetic induction is transmitted to the inside of the bearing through a conductor such as a metal part. The transmitted electromagnetic induction becomes an EMD current and / and a high frequency circulating current. When EMD current and / or high-frequency circulating current is generated, it is also transmitted to the rotating shaft and rolling element (bearing ball) 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 and / or the high frequency circulating current. Due to the electrolytic corrosion phenomenon, the rotating shaft or rolling element is corroded, and it becomes impossible to maintain a uniform rotational motion. In particular, bearings used in the vicinity of an inverter with an operating frequency of 50 Hz or higher are prone to electrolytic corrosion.
In contrast, among the plurality of rolling elements used in a bearing for use in an inverter near the present invention, the at least one rolling element and the electric resistance of an insulating ceramic or insulative coating 10 ⁷ Ω · cm or more I am using something.
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. Further, the electric resistance value is ^{preferably 10 10} Ω · cm or more. Further, the electric resistance value shall be measured by an electric resistance measuring device by the two-terminal method.

The use of electrical resistance 10 ⁷ Ω · cm or more insulating rolling elements, EMD current or / and high frequency circulating current can be prevented from being transmitted to the rotating shaft and the rolling elements.
Examples of the rolling elements having such insulating properties include those containing at least one selected from aluminum oxide, zirconium oxide, silicon nitride, silicon oxide, fluororesin, and engineering resin as a main component.
Examples of ceramics containing at least one of aluminum oxide, zirconium oxide, silicon nitride, and silicon oxide as main components include ceramics sintered bodies obtained by adding a sintering aid and sintering the mixture, if necessary. Also, aluminum oxide, zirconium oxide, silicon nitride, ceramics sintered body of silicon oxide are both electric resistance 10 ⁷ Ω · cm or more insulators (insulating ceramic sintered body). The sintering aid shall be selected so as not to reduce this insulating property. Among the ceramic sintered bodies, the silicon nitride sintered body using yttrium oxide as a sintering aid is preferable because it has excellent sliding characteristics.

As the electrical resistance 10 ⁷ Ω · cm or more rolling elements, on the surface of the metal member, zirconium oxide, silicon nitride, silicon oxide, chromium oxide, fluororesin, at least one or more of the sprayed coating selected from engineering resins There is also one that has been given.
As described above, the electrolytic corrosion phenomenon occurs in the metal member, but by providing the insulating sprayed film, the same insulating property as that of the insulating ceramic sintered body can be maintained. The film 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 peeling may occur, and if it exceeds 300 μm, no further effect can be obtained. Further, since these sprayed films have a good affinity with the bearing steel (SUJ2), excellent bonding strength can be obtained.

Comparing the insulating ceramics sintered body and the insulating sprayed film, the sprayed film requires a film forming process, so that the manufacturing process is complicated. In addition, uniform control of the film thickness is required. Therefore, a rolling element made of an insulating ceramic sintered body is preferable.
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. The outer ring, inner ring, and rotating shaft are made of bearing steel (SUJ2).
Usually, 8 to 20 rolling elements are used for bearings. If at least one rolling element having the above-mentioned insulating property is used, electrolytic corrosion can be suppressed in the bearing used in the vicinity of the inverter operating at 50 Hz or higher.
Further, among the plurality of rolling elements, for what to many pieces of insulation, the number of P (number) of the electrical resistance 10 ⁷ Ω · cm or more rolling elements, the rotational speed of the bearing M (rpm ), When the drive frequency of the inverter is F (Hz), it is preferable that P × M ≧ 60F. The rotation speed M (rpm) of the bearing is the maximum rotation speed in the usage environment.

In the present invention, all of the rolling element electrical resistance it is preferred to use those having a more insulating 10 ⁷ Ω · cm. However, the insulating rolling elements are more expensive than those made of bearing steel (SUJ2). Therefore, it is effective to reduce the cost by replacing a part of the plurality of rolling elements with a rolling element made of bearing steel. At this time, if the relationship satisfies P × M ≧ 60F, electrolytic corrosion can be effectively suppressed.
For example, the rotation speed M of the bearing 5000 rpm, when the driving frequency F of the inverter is 200Hz, P × 5000 ≧ 60 × 200, P ≧ 2.4, therefore three or more more than the electrical resistance of 10 ⁷ Ω · cm This can effectively prevent electrolytic corrosion.

The number of rolling elements (bearing balls) mounted on the bearing is arbitrary, but is usually in the range of 8 to 20. For example, when the drive frequency is 3000 Hz and the rotation speed is 5000 rpm, P × M ≧ 60 F → P × 5000 ≧ 60 × 3000 → P ≧ 36, and when the P value is equal to or more than the number of rolling elements, all the rolling elements are electric. shall use the least resistance 10 ⁷ Ω · cm insulating rolling elements.

In addition, when electrolytic corrosion occurs, the part in contact with the rolling element such as the inner ring or the rotating shaft, or the rolling element itself is scraped. As a result, stable rotational motion cannot be provided. In addition, a method of measuring the sound during rotation is effective for determining whether or not the motion is stable. For example, when the sliding sound at a constant rotation speed is electrolytically corroded, the sliding sound becomes louder.
Further, it is preferable that the drive frequency of the inverter is 4000 Hz or less. It is possible to effectively prevent electrolytic corrosion by using a rolling element having insulating properties, but if the frequency becomes too high, the electrolytic corrosion suppressing effect may be insufficient only with the insulating properties of the rolling elements. .. Therefore, when an insulating rolling element is used, 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 to 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, an IGBT element, and the like. The inverter control circuit, PW M (pulse width modulation) drive 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 not easily affected by electrolytic corrosion. Therefore, it is not restricted by the arrangement of the control circuit and the bearing. Therefore, it can be applied from home appliances such as air conditioners and washing machines to the vicinity of inverters of various electric appliances such as electric vehicles and railroad vehicles. In other words, it is possible to provide highly reliable electrical equipment that is not affected by electrolytic corrosion. The vicinity of 1 m or less 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 to 4, Comparative Example 1)
An inverter bearing was manufactured by incorporating eight rolling elements (bearing balls) having a diameter of 1 cm into an inner ring (inner diameter of 5 cm) and an outer ring (outer diameter of 8 cm). The inner ring and 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. ..
Inverter motors for electrical equipment were manufactured by incorporating such inverter bearings into inverter motors. An electrolytic corrosion test of each inverter motor was performed. The bearing was installed in the inverter motor (the inverter and bearing are placed within 1 m).
The electrolytic corrosion of the inverter motor is measured by measuring the sound intensity with a microphone (pickup sensor) when the inverter motor is operated continuously for 400 hours at a frequency of 100 Hz and a rotation speed of 7000 rpm on the outer ring side, and the sensor output exceeds 30 dB. The case was defined as "presence", the case exceeding 25 dB and 30 dB or less was defined as "slightly present", and the case of less than 25 dB was defined as "absent". 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 the vibration was suppressed to a low level and no electrolytic corrosion was generated in any case. This means that the bearing according to the embodiment has P × M ≧ 60F, and P × 7000 ≧ 60 × 100 to P ≧ 0.9. Therefore, electrolytic corrosion was prevented in all of those using one or more insulating rolling elements.

(Examples 5 to 8, Comparative Example 2)
A bearing for an inverter motor was manufactured by incorporating 12 rolling elements (bearing balls) having a diameter of 1 cm into an inner ring (inner diameter of 8 cm) and an outer ring (outer diameter of 10 cm). The inner ring and 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 2. ..
Next, an inverter motor similar to that of the first embodiment 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 increased vibration. The bearing was incorporated into the inverter motor (the inverter and bearing are placed within 1 m). The results are shown in Table 2.

As can be seen from the table, P × M ≧ 60F, P × 8000 ≧ 60 × 800 , and P ≧ 6. No electrolytic corrosion was confirmed in Examples 6 to 8 satisfying this condition, but it was slightly present in Example 5 which did not satisfy this condition.

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

Even if the insulating rolling element had an electrical resistance of 10 ¹⁰ Ω · cm, it could be effectively used.

(Examples 13 to 15)
Example 13 was a silicon nitride sintered body (electrical resistance value 10 ¹² Ω · cm or more), Example 14 was an engineering resin (electrical resistance value 10 ¹³ Ω · cm), and a chromium oxide spray film (thickness 100 μm) was applied. constitute an inverter bearing SUJ2 balls (electric resistance 10 ⁸ Ω · cm or higher) as in example 15 under the conditions shown in Table 4 was measured the presence of at electroerosion same manner as in example 1. The diameter of the rolling elements was unified to 1 cm, and the bearings used were 16 rolling elements in total. The inverter motor and bearing were arranged within 1 m. The results are shown in Table 4.

From P × M ≧ 60F, P ≧ 36 in Example 13, P ≧ 20 in Example 14, and P ≧ 40 in Example 15. In each case, the P value was larger than the total number of rolling elements, so all of them had to be insulating rolling elements.

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

Claims (5)

It is a method of using an electric device equipped with an inverter motor.
The electrical equipment
A control circuit for controlling the driving frequency of the inverter motor below 2000Hz over 50 Hz,
It is equipped with a rolling bearing installed within 1 m from the control circuit.
The rolling bearing
Inner ring made of SUJ2 material and
An outer ring made of SUJ2 material and
Containing an insulating ball-bearing electric resistance is ¹⁰ 10 Ω · cm or more with containing an insulating ceramic, comprising: a plurality of bearing balls, and
When the number of insulating bearing balls is P (pieces), the maximum rotation speed of the rolling bearing in the usage environment is M (rpm), and the drive frequency of the inverter motor is F (Hz), P × M ≧ A method of using an electric device that suppresses the occurrence of electrolytic corrosion by satisfying 60F and the P being an integer of 6 or more. The method of use according to claim 1, wherein the electrolytic corrosion is corrosion of at least one member selected from the group consisting of the inner ring, the outer ring, the bearing ball, and a rotating shaft to which the inner ring is fixed. The method of use according to claim 1 or 2, wherein the control circuit controls the drive frequency of the inverter motor to 50 Hz or more and 1000 Hz or less. The insulating ceramic is a sintered body containing at least one selected from the group consisting of aluminum oxide, zirconium oxide, silicon nitride, and silicon oxide, according to any one of claims 1 to 3. how to use. The method of use according to claim 4, wherein the sintered body is silicon nitride containing a rare earth oxide.

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