JP2005325929A - Rolling bearing and use method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller bearing of machinery operated at a low speed, avoiding the operational lag and operational disability of the machinery, avoiding a decrease in thickness of an oil film with a temperature rise of a bearing part, and avoiding an increase in price of the machinery due to adoption of a motor having a large output. <P>SOLUTION: In the vacuum machinery operated at a low speed of at most 25000 in DmN, which is the product of pitch circle diameter Dm (mm) of the bearing by rotating speed N (min<SP>-1</SP>), the rolling bearing 11 is filled with lubricating fluorine grease having characteristic of forming an insulating film to increase insulating time ratio between the inner ring and the outer ring of the bearing in addition to an oil film formed by base oil. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a vacuum mechanical device that is operated at a low speed of 25,000 or less (Dm × N) of a bearing pitch circle diameter (Dm (mm)) and a rotational speed (N (min ⁻¹ )). The present invention relates to a rolling bearing and a method for using the same.

A rolling bearing that uses grease as a lubricant and can impart sufficient lubricity and rust prevention to the surface of a rolling element or the like is known (see, for example, Patent Document 1 or 2).
In addition, a method using oil film parameters is known as a representative example of a method for determining the quality of a lubrication state in a rolling bearing (see Non-Patent Document 1).
JP 2003-13974 A JP 2000-65075 A “NSK Technical Report”, NSK Ltd., CAT. No. 728d, 1998C-5, p. 42-49

Therefore, based on Non-Patent Document 1, the oil film parameter will be described first.
The oil film parameter (symbol: Λ) can be calculated by using the oil film thickness (symbol: h) calculated based on the elastohydrodynamic lubrication theory and the combined surface roughness (symbol: σ) of the components of the rolling bearing. It is represented by 1.

Λ = h / σ (Formula 1)

The greater the oil film parameter (Λ), the less likely the metal contact between the parts of the rolling bearing will occur, and the better the lubrication of the rolling bearing. Therefore, the oil film parameter (Λ) is generally classified as follows from the viewpoint of bearing life and surface damage.
(1) 3 ≦ Λ: Long-life region,
(2) 0.9 ≦ Λ <3: Region where transition from long life to short life is performed Among these, 0.9 ≦ Λ <1.5: Surface damage occurs when slip is large. (3) Λ <0.9: Short-life area (because of surface damage)
Therefore, in order to improve the lubrication state of the rolling bearing and avoid the surface damage of the rolling bearing, it is desirable that the oil film parameter is Λ> 1.5 as a guide.
Here, from Equation 1, in order to increase the oil film parameter (Λ),
(1) a method of increasing the oil film thickness (h);
(2) A method of reducing the synthetic surface roughness (σ) is conceivable.
However, it is not easy to reduce the composite surface roughness (σ) for technical or economic reasons related to the machining of the bearing, and in order to increase the oil film parameter (Λ) for an already completed bearing. The oil film thickness (h) can only be increased.

Next, the equation for calculating the oil film thickness (h) is conceptually expressed as Equation 2 using the kinematic viscosity (υ), rotation speed (N), and load (P) of the base oil. The first α is a constant including the influence of the bearing specifications, and the indices a, b and c are also constants.

h = α · υ ^a · N ^b · P ^−c (Formula 2)

When designing around the bearings of a mechanical device, among the three variables, the rotational speed (N) and load (P) are values that are determined from the required specifications, and in order to increase the oil film thickness (h) It is necessary to increase the kinematic viscosity (υ) of the base oil. Particularly, in the case of a bearing that rotates at a low speed, the effect of N ^b which definitive in Equation 2 is reduced, it is necessary to increase the kinematic viscosity of the base oil (upsilon) more than enough.
In addition, when used at a temperature higher than normal temperature, it is necessary to select a higher base oil kinematic viscosity (υ) in consideration of a decrease in base oil kinematic viscosity (υ) as the temperature rises. It becomes.
For this reason, in the conventional lubrication of rolling bearings of mechanical devices that are operated at a low speed, a lubricating method in which lubricating oil or grease having extremely high kinematic viscosity of the base oil is enclosed in the rolling bearing has been adopted.

In conventional rolling bearings for vacuum machinery operating at low speed, lubricating oil and grease with extremely high kinematic viscosity of the base oil are sealed in the rolling bearing. There is a problem that the resistance becomes large, causing a delay in the operation of the mechanical device, or in the worst case, becoming inoperable.
In addition, since the viscosity resistance is large, the temperature of the bearing portion is likely to rise, so the temperature rise of the bearing portion causes a decrease in the base oil kinematic viscosity of the lubricating oil or grease, and as a result, the required oil film thickness is reduced. There was a problem that it could not be secured.
Furthermore, when a motor with a large output is employed to eliminate malfunctions (operation delays or inoperability) of the mechanical device, there is a problem that the mechanical device becomes large in size and its price increases.
The present invention has been made in view of such problems, and eliminates the need to enclose lubricating oil or grease having a very high kinematic viscosity of the base oil in a rolling bearing of a mechanical device operated at a low speed. Rolling bearings that can prevent delays and inoperability of machinery, reduce oil film thickness due to bearing temperature rise, and avoid increased machinery costs due to the use of a motor with a large output. And its use.

In order to solve the above problem, the invention according to claim 1 relates to a rolling bearing, wherein a product of a pitch circle diameter (Dm (mm)) and a rotational speed (N (min ⁻¹ )) of the bearing: DmN is 25,000. Rolling bearings for vacuum mechanical devices that are operated at the following low speeds have characteristics that an insulating film is formed in addition to the oil film formed by the base oil and the insulation time ratio between the inner ring and the outer ring of the bearing increases. It is characterized by sealing fluorine grease for lubrication.
According to a second aspect of the present invention, in the rolling bearing according to the first aspect of the present invention, a grease mixed with linear perfluoropolyether oil and PTFE (polytetrafluoroethylene resin) is sealed as the lubricating fluorine grease. Features.
The invention described in claim 3 is characterized in that the bearing is operated at a bearing temperature of 50 ° C. or higher when the rolling bearing according to claim 1 or 2 is used.

According to the first aspect of the present invention, the insulating film is formed in addition to the oil film formed from the grease base oil, and the insulating time ratio is increased between the inner ring and the outer ring of the bearing. As a result, the frequency of metal contact between the bearing parts decreases, and a good lubrication state can be ensured.
According to the invention of claim 2, the formation of the insulating film is accelerated by using a grease in which a linear perfluoropolyether oil and PTFE are mixed, and a good lubricating state can be secured.
Further, according to the invention described in claim 3, since the thickness of the insulating film is increased by raising the bearing temperature to 50 ° C. or higher, it is possible to ensure a good lubrication state even if grease having a lower kinematic viscosity is used. .

  Hereinafter, specific examples of the method of the present invention will be described with reference to the drawings.

表１において、
（１）実施例１はＫＤＬグリース（販売元：光洋精工（株））を、
（２）実施例２はデムナムＬ２００（販売元：ダイキン工業（株））を、
（３）実施例３はデムナムＬ６５（販売元：ダイキン工業（株））を、
それぞれ内輪２と外輪３との間に封入したものである。
一方、比較例については、
（１）比較例１はブレイコート６０２ＥＦ（販売元：ＢＰジャパン（株））を、
（２）比較例２はフォンブリンＧＲＭ６０（販売元：ソルベイ・セレクシス（株））を、
そして、（３）比較例３はクライトックスＬＶＰ（販売元：デュポン（株））を、
それぞれ内輪２と外輪３との間に封入したものである。
なお、ＫＤＬグリース、デムナムＬ２００、デムナムＬ６５は、潤滑用フッ素グリースとして、直鎖状パーフルオロポリエーテル油とＰＴＦＥ（ポリテトラフルオロエチレン樹脂）を混合したものとなっている。 Before describing an embodiment of the present invention, a configuration of a deep groove ball bearing as an example of a rolling bearing will be described with reference to FIG. FIG. 1 is a partial sectional view of a deep groove ball bearing. The deep groove ball bearing 1 includes an inner ring 2, an outer ring 3 provided on the outer periphery of the inner ring 2, a plurality of spherical rolling elements 4 that are rotatably incorporated between the outer ring 3 and the inner ring 2, The spherical rolling element 4 is provided with a cage 5 that holds the inner ring 2 and the outer ring 3 in the circumferential direction at equal intervals.
Grease is enclosed in a space between the inner ring 2 and the outer ring 3 while adhering to the spherical rolling element 4 and the cage 5. If necessary, a shield plate may be attached.
Examples of the present invention based on such a configuration are shown in Table 1 together with comparative examples.

In Table 1,
(1) In Example 1, KDL grease (distributor: Koyo Seiko Co., Ltd.)
(2) In Example 2, demnum L200 (distributor: Daikin Industries, Ltd.)
(3) In Example 3, demnum L65 (distributor: Daikin Industries, Ltd.)
Each is enclosed between the inner ring 2 and the outer ring 3.
On the other hand, for the comparative example,
(1) In Comparative Example 1, Braycoat 602EF (distributor: BP Japan Co., Ltd.)
(2) Comparative Example 2 is Fomblin GRM60 (Distributor: Solvay Selexis Co., Ltd.)
And (3) Comparative Example 3 is Krytox LVP (Distributor: DuPont),
Each is enclosed between the inner ring 2 and the outer ring 3.
Note that KDL grease, demnum L200, and demnum L65 are a mixture of linear perfluoropolyether oil and PTFE (polytetrafluoroethylene resin) as lubricating fluorine grease.

Next, FIG. 2 shows a schematic structure of the lubrication characteristic tester used in this test.
In FIG. 2, 11 is a test bearing, 12 is a coil spring, 13 is a heater, 14 is an insulating flange, 15 is a vacuum chamber, 16 is a vacuum pump, 17 is a motor, 18 is a torque meter, 19 is a magnetic fluid seal, and 20 is A current introduction terminal, 21 is a thermocouple, 22 is a voltage measurement lead, and 23 is a voltage measurement brush.
The test bearing 11 receives an axial load from the coil spring 12 and is heated by the heater 13. The temperature of the test bearing 11 is adjusted by a thermocouple 21.
The rotational torque of the motor 17 is transmitted to the test bearing 11 disposed in the vacuum chamber 15 through the magnetic fluid seal 19 and measured by the torque meter 18. The electric circuit from the current introduction terminal 20 to the voltage measuring brush 23 via the voltage measuring lead wire 22 measures the voltage between the inner ring and the outer ring of the test bearing 11.
Since it is difficult to actually measure the oil film parameter (Λ), which is an index of the lubrication state in the rolling bearing, the inner ring 2 is used as a substitute characteristic by using the following method from the voltage value between the inner ring 2 and the outer ring 3 of the test bearing 11. The insulation time ratio between the outer ring 3 and the outer ring 3 was measured.

A schematic diagram of the measurement circuit of the insulation time ratio is shown in FIG.
In FIG. 3, 2 is an inner ring, 3 is an outer ring, 31 is a power source, 32 is a series resistor, 33 is an amplifier, 34 is an integrating circuit, and 35 is a voltmeter.
The voltage (E0) between the inner ring 2 and the outer ring 3 is
(1) If there is an instantaneous metal contact between the inner ring 2 and the outer ring 3, E0 = 0 (V),
(2) If there is no metal contact, E0 = EAB (V).
Here, EAB is a potential difference when the inner ring 2 and the outer ring 3 are opened.
The AC signal of 0 to EAB (V) is amplified by the amplifier 33 and then smoothed by the integrating circuit 34. A display of the obtained signal at 0 to 100% is called an insulation time ratio.

Next, a specific test method will be described with reference to FIGS.
The test bearing 11 is a deep groove ball bearing having a nominal number 6906. The material of the inner ring 2, the outer ring 3 and the spherical rolling element 4 is SUS440C. The standard for the radial internal gap is C3, and no shield plate is attached. Two test bearings 11 were used, and after ultrasonic cleaning with acetone, grease was sealed in a mass range of 1.4 to 1.6 g. An axial load of 98 N was applied by the coil spring 12 and incorporated in the lubrication characteristic tester 10. The vacuum pump 16 was started and the inside of the vacuum chamber 15 was evacuated to about 5 × 10 −4 Pa, and then a break-in operation was performed for 50 hours or more at a rotation speed of 200 min−1. At this time, the heater 13 is in an OFF state.
After the motor 17 was temporarily stopped, the measurement of the insulation time ratio was started. After starting driving 5 minutes motor at a rotation speed 20min ^-1, it was accelerated to 300 min ^-1 by increasing the rotational speed by 20min ^-1. The operation was continued for 5 minutes at each speed. At this time as well, the heater 13 was in an OFF state, and the average value of the bearing temperature was approximately in the range of 30 to 40 ° C. Thereafter, by operating the heater, it was heated and 50,70,90,110 ° C., was tested stepwise acceleration Likewise from 20min ^-1 to 300 min ^-1 at each temperature.
The obtained test results were arranged with the calculated value of the oil film parameter on the horizontal axis and the insulation time ratio on the vertical axis. Here, the calculated value of the oil film parameter is the calculated value of the oil film thickness obtained from the Dowson-Higginson formula (Non-Patent Document 1, p. 44), and the measured value of the combined surface roughness of the components of the rolling bearing ( It was calculated by dividing by 0.05 μm).
First, the relationship between the calculated value of the oil film thickness and the insulation time ratio in the case of Comparative Example 1 is shown in FIG. The bearing temperature is different from 30, 50, 70, 90, and 110 ° C, but all the data exists on the same line, and the measured value of the insulation time ratio can be used as the substitute characteristic value of the oil film parameter that is the calculated value. .
Here, as described above, the relationship between the oil film parameter (Λ) and the lubrication state of the rolling bearing is approximately that the surface damage of the rolling bearing is likely to occur when Λ <1.5. If the insulation time ratio is 1% or less, the surface damage of the rolling bearing is likely to occur.

From FIG. 4, when the rotation speed of the bearing when the insulation time ratio corresponding to the oil film parameter = 1.5 = 1% is read,
50 min ^-1 when the bearing temperature is 30 ° C
90 min ^-1 at 50 ° C,
160 min ⁻¹ at 70 ° C.,
240 min ⁻¹ at 90 ° C.,
It becomes 360 min ⁻¹ (estimated value) at 110 ° C.
In the case of Comparative Example 1, the relationship between the bearing temperature and the kinematic viscosity of the grease base oil is
30 ° C. is 167.5 mm ² / s,
50 ° C. is 112.1 mm ² / s,
70 ° C. is 74.3 mm ² / s,
90 ° C. is 52.0 mm ² / s,
110 ° C. is 38.1 mm ² / s.
In Comparative Example 1, the relationship between the kinematic viscosity of the base oil and the rotational speed of the bearing when the insulation time ratio = 1% is shown in FIG.
In FIG. 5, in the area below the line connecting the plots, the rolling bearing is poorly lubricated. Accordingly, when the kinematic viscosity of the base oil necessary for maintaining the lubrication state of the rolling bearing at 40 ° C., at which the kinematic viscosity of the base oil of the grease is almost publicized, is expressed numerically, in the comparative example, the rolling bearing The kinematic viscosity of the base oil necessary to keep the lubricating state of
(1) When the rotation speed is 100 min ⁻¹ , 100 mm ² / s or more,
(2) 340 mm ² / s or more when the rotational speed is 20 min ⁻¹ ,
(3) When the rotational speed is 10 min ⁻¹ , it is as high as 580 mm ² / s or higher.
Furthermore, when the bearing temperature is higher than 40 ° C., it is necessary to select a grease having a higher kinematic viscosity of the base oil at 40 ° C. in consideration of a decrease in kinematic viscosity with temperature.
In the case of the conventional example 1, when the bearing temperatures are 40 ° C. and 110 ° C., the rotation speeds required to obtain the insulation time ratio = 1% are shown in Table 1, which are 65 min ⁻¹ and 368 min ⁻¹ . Become. That is, the lubrication state in the case of Conventional Example 1 is
(1) When the bearing temperature is 40 ° C., it becomes worse when the rotational speed is 65 min ⁻¹ or less,
(2) When the bearing temperature is 110 ° C., it becomes worse when the rotational speed is 368 min ⁻¹ or less.
Then, Comparative Example 2 is Fomblin GRM60 (distributor: Solvay Celexis Co., Ltd.), and Comparative Example 3 is Krytox LVP (distributor: DuPont Co., Ltd.) between the inner ring 2 and the outer ring 3. Although it was sealed, as shown in Table 1, as in the case of Example 1, an increase in the insulation time ratio was not recognized.
In the case of Conventional Example 2, due to the high kinematic viscosity of the base oil, when the bearing temperature is 40 ° C., a good lubrication state can be obtained when the rotational speed is 23 min ⁻¹ or more, but the bearing torque is large. There is. When the bearing temperature rises to 110 ° C., a good lubrication state cannot be obtained unless the rotational speed is 156 min ⁻¹ or higher.
In the case of Conventional Example 3, the kinematic viscosity of the base oil is higher, so that when the bearing temperature is 40 ° C., a good lubrication state can be obtained until the rotational speed is 8 min ⁻¹ , but the bearing torque is extremely large. There's a problem. Since the kinematic viscosity of the base oil tends to change greatly as the temperature rises, when the bearing temperature rises to 110 ° C., a good lubricating state cannot be obtained unless the rotational speed is 330 min ⁻¹ or higher.

Next, the relationship between the calculated value of the oil film thickness and the insulation time ratio in the case of Example 1 is shown in FIG.
At all temperatures (33, 50, 70, 90, 110 ° C.), even at a rotational speed of 20 min ⁻¹ , the insulation time ratio is greater than 1, indicating that the lubrication state inside the rolling bearing is good. .
When the bearing temperature is 40 ° C. and the rotational speed is 20 min ⁻¹ , the kinematic viscosity of the base oil necessary to ensure a good lubrication state was 340 mm ² / s or more in the grease of Comparative Example 1. in example 1, at a kinematic viscosity of smaller base oil and 25.0 mm ² / s in 200mm ² / s, 110 ℃ at 40 ° C., it can be seen that to ensure a good lubrication.
From FIG. 6 (Example 1) and FIG. 4 (Comparative Example 1), the insulation time ratio when the calculated value of the oil film parameter is 1, that is, the calculated value of the oil film thickness is 0.05 μm, is read. This relationship is shown in FIG.
In FIG. 7, in the case of Comparative Example 1, the insulation time ratio does not change even when the bearing temperature increases, but in the case of Example 1, the insulation time ratio increases as the bearing temperature increases, and is about 40 at 50 ° C. %, Reached almost 100% at 70 ° C. or higher. In Example 1, especially when the bearing temperature becomes 50, the lubrication state of the bearing becomes better, and the higher the temperature, the smaller the kinematic viscosity of the base oil can be selected.
That is, in Example 1, in addition to the oil film formed from the base oil, it is presumed that the grease forms an insulating film, thereby increasing the insulation time ratio.
Note that the change in FIG. 7 is reversible with respect to the rise and fall of the bearing temperature, and does not damage the surface of the bearing member from the observation result of the bearing after the test.
In the case of Example 1, the rotational speeds required to obtain the insulation time ratio = 1% at the bearing temperatures of 40 ° C. and 110 ° C. are shown in Table 1, both of which were less than 20 min ⁻¹ . This time, since the test of 20 min ^-1 was not performed, an accurate numerical value was not grasped.
That is, in the case of Comparative Example 1, when the bearing temperature is 40 ° C., a good lubricating state is obtained at least until the rotational speed is 20 min ⁻¹ or more, and more surprisingly, the kinematic viscosity of the base oil is increased. Without increasing, even when the bearing temperature is 110 ° C., a good lubrication state is obtained at least until the rotational speed is 20 min ⁻¹ or more.
[Other Examples]

Example 2 is a demnum L200 (seller: Daikin Industries, Ltd.) and Example 3 is a demnum L65 (seller: Daikin Industries, Ltd.) sealed between the inner ring 2 and the outer ring 3. is there.
As shown in Table 1, as in the case of Example 1, an increase in the insulation time ratio was observed, and a satisfactory lubrication state was obtained until the bearing temperature was 40 ° C. and 110 ° C. and at least the rotation speed was 20 min ⁻¹ or more. Is obtained.

In this way, in the rolling bearing of a mechanical device that is operated at a low speed with the product of the pitch circle diameter (Dm (mm)) and the rotational speed (N (min ⁻¹ )) of the bearing: DmN of 25,000 or less, Lubricating grease manufactured and sold by Kogyo Co., Ltd. (trade names: Demnam L200, Demnam L100, Demnam L65, Demnam LR200, Demnam LP200, Demnum LS200), Lubricating grease sold by Koyo Seiko Co., Ltd. Grease), and if necessary, the bearing temperature is set to 50 ° C or higher, so that grease forms an insulating film without using grease with a high kinematic viscosity of the base oil. As a result, the insulating time ratio increases, so that a good lubricating state can be ensured in the rolling bearing of the vacuum mechanical device.

In this embodiment, the application is not limited to a rotary type rolling bearing, and may be applied to a direct acting type rolling bearing. Further, the use environment of the mechanical device is not limited to a vacuum, but can be applied to a mechanical device for an atmospheric environment.
In addition, the following two were searched as a prior application (the name is not written in the claim) in which the name of demnum grease of Daikin Chemical Industries, Ltd. was written, but it is not applicable as this prior art I think.
(1) “JP 2003-13974 (rolling device)” demnum L65, 3000 min-1, (bearing type unknown), (DmN unknown), test temperature: 100 ° C., atmospheric pressure: 10 −4 Pa.
In order to impart lubricity and rust prevention, rust prevention oil is applied to a special bearing member.
(2) “JP 2000-65075 (rolling bearing)” demnum L200, 1000 min ⁻¹ , bearing model number 608, DmN = 15,000 mm · min ⁻¹ , test temperature: normal temperature, atmospheric pressure: atmospheric pressure.
In order to improve dust generation, a magnetic fluid seal is formed on the shield plate of the bearing.

It is sectional drawing which shows a part of deep groove ball bearing. FIG. 3 is a schematic structural diagram of a lubrication characteristic tester used for examining a lubrication state of a rolling bearing. It is the schematic of the electric circuit which measured the insulation time ratio of the rolling bearing. It is a correlation diagram of the oil film parameter and insulation time ratio in the first conventional example. It is a correlation diagram of the kinematic viscosity of the base oil and the insulation time ratio in the first conventional example. It is a correlation diagram of the oil film parameter and the insulation time ratio in the first embodiment. It is a correlation diagram of the bearing temperature and the insulation time ratio in the first embodiment and the first conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing 2 Inner ring 3 Outer ring 4 Spherical rolling element 5 Cage 10 Lubrication characteristic tester 11 Test bearing 12 Coil spring 13 Heater 14 Insulating flange 15 Vacuum chamber 16 Vacuum pump 17 Motor 18 Torque meter 19 Magnetic fluid seal 20 Current introduction terminal 21 Thermocouple 22 Voltage Measurement Lead Wire 23 Voltage Measurement Brush 31 Power Supply 32 Series Resistance 33 Amplifier 34 Integration Circuit 35 Voltmeter

Claims (3)

Product of bearing pitch circle diameter (Dm (mm)) and rotational speed (N (min ^-1 )): In a rolling bearing of a vacuum machine operated at a low speed of DmN of 25,000 or less, the base oil is A rolling bearing characterized in that, in addition to an oil film to be formed, an insulating film is formed and a lubricating fluorine grease having a characteristic of increasing an insulation time ratio between an inner ring and an outer ring of the bearing is enclosed.   2. The rolling bearing according to claim 1, wherein a grease mixed with linear perfluoropolyether oil and PTFE (polytetrafluoroethylene resin) is enclosed as the lubricating fluorine grease.   A method for using a rolling bearing, wherein the rolling bearing is operated at a bearing temperature of 50 ° C or higher when the rolling bearing according to claim 1 or 2 is used.

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