JP2009029891A - Lubricating oil composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating oil composition capable of improving the durable service life of rolling bearings assembled in speed reducers and/or hydraulic equipment without increasing their load capacity, and to provide such a rolling bearing using the lubricating oil composition. <P>SOLUTION: The lubricating oil composition is such as to be obtained by compounding a synthetic oil such as a polyalkylene glycol with 0.1-10 wt.%, on the whole composition basis, of a molybdenum compound such as MoDTC as an additive. The rolling bearing, which is to be used in speed reducers and/or hydraulic equipment for industrial machinery, is a conical roller bearing 18 composed of an outer ring 3, a ribbed inner ring 4, and a conical roller 5 interposed between the track surfaces of these two rings. This rolling bearing is to be lubricated with the above composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lubricating oil composition for a rolling bearing that is incorporated in a reduction gear for an industrial machine or a hydraulic device and is oil-lubricated, and a rolling bearing, and particularly to a large construction machine such as a hydraulic excavator or a dump truck, and an industrial industry. The present invention relates to a reduction gear for a robot and a rolling bearing for hydraulic equipment.

In general, a planetary gear type speed reducer capable of obtaining a large reduction ratio is employed in a power transmission system of a large construction machine such as a hydraulic excavator, a dump truck, or a wheel loader.
FIG. 3 shows a planetary gear type reduction gear of a hydraulic excavator. In this reduction gear, the first planetary gear 13 is meshed with each of the drive gear 11 provided on the input shaft 10 and the fixed internal gear 12, and the rotation of the drive gear 11 is transmitted to the first planetary gear 13 to revolve. Then, the revolution is transmitted from the intermediate gear 14 provided coaxially with the input shaft 10 to the second planetary gear 15 meshing with the intermediate gear 14 and the internal gear 12, and the second planetary gear revolving while rotating. The drive sprocket 16 is rotated by the revolution of 15 and transmitted to the crawler belt 17 meshing with the drive sprocket 16.

In the planetary gear type speed reducer, the first planetary gear 13 and the second planetary gear 15 are supported by the tapered roller bearings 18 and 19 and the angular bearings 20 and 21, and these bearing portions are oil-lubricated to prevent seizure. is doing.
Mineral oils and synthetic oils are used as the lubricating oils for these oil lubrications, and lubricating oils to which antiwear additives and the like are added are used. Moreover, polyalkylene glycol etc. are used in synthetic oil.
For the improvement in the structural surface of the angular bearing used in the reduction gear shown in FIG. 3, the rolling element, a cage for holding the rolling element, inner and outer raceway surfaces of the rolling element, and An angular ball bearing is known that includes inner and outer rings in which a rolling element and inner and outer raceway surfaces are in contact with each other with a predetermined contact angle in the radial direction (see Patent Document 1). In the bearing, the relationship between the outer ring outer diameter with respect to the inner ring inner diameter of 100 mm or more, the clearance between the rolling elements with respect to the rolling element diameter, the groove curvature of the inner and outer rings, and the ratio of the shoulder height of the inner and outer rings are controlled within a predetermined range. Therefore, the required rigidity is maintained, the rated load is improved, the contact surface pressure is reduced, the inner and outer ring raceway surfaces, the rolling elements are prevented from being peeled off early, and the surface is prevented from being rough.

Unlike the normal rolling surface or surface peeling caused by metal fatigue, this early peeling, which causes the rolling bearings to have an early life, shows a peculiar failure phenomenon that occurs suddenly from the part that penetrates deeply into the raceway groove surface. ing.
Conventionally, in order to eliminate the above-described specific peeling phenomenon, the bearing life is improved by changing the bearing size and improving the load capacity by structural improvement as in Patent Document 1, for example. However, such an increase in the size of the bearing leads to an increase in the size of the speed reducer itself, which increases the cost.

In addition, the present inventors have found that a peculiar fracture phenomenon of a rolling bearing occurs in a portion that penetrates into the inside considerably from the rolling surface. It was thought that this was due to the occurrence of cracks due to changes in the structure.
In general machine parts, it is well known that when hydrogen penetrates the inside of a metal, particularly steel, it causes hydrogen embrittlement and breaks early. In general bearings, the stress generated at the contact surface between the rolling element and the rolling surface is a fluctuating stress, and because it is not a static constant stress like delayed fracture, which is a problem in hydrogen embrittlement, fracture due to hydrogen embrittlement is a problem. Never became. In particular, in oil lubricated bearings used in severe conditions, it is considered that the rolling surface of the rolling element is contaminated at the initial stage of use, and the catalytic action on the metal surface disappears.

However, since rolling bearings such as tapered roller bearings, angular contact ball bearings, needle bearings, etc. incorporated in the reduction gears and hydraulic equipment for industrial machines described above are subjected to heavy loads and high vibrations at low speed rotation, rolling elements Many cases have been reported in which flaking occurs on the rolling contact surface where rolling occurs and these bearings reach the end of their service life early. Since this flaking is subjected to heavy load and high vibration in a low-speed rotation state, it is difficult to generate an oil film on the surface of the rolling element, and due to the movement of the rolling element, the rolling surface locally becomes high temperature and high pressure, The rolling surface is specularly abraded, and the formation of a new surface due to this becomes a catalytic action, and it is predicted that the lubricating oil decomposes and is caused by hydrogen generated at that time. These problems also occur with rolling bearings for industrial robots used under similar conditions.
JP-A-9-264321

  The present invention has been made to cope with such problems, and in rolling bearings incorporated in reduction gears and hydraulic equipment for industrial machines, particularly in reduction gears and hydraulic equipment such as large construction machines and industrial robots, It is an object of the present invention to provide a lubricating oil composition capable of improving the durability life without improving the load capacity and a rolling bearing using the lubricating oil composition.

  The lubricating oil composition of the present invention is a lubricating oil composition for a rolling bearing used by being incorporated in a reduction gear or a hydraulic device, and the lubricating oil composition contains a synthetic compound and a molybdenum compound as an additive. The molybdenum compound is blended in an amount of 0.1 to 10% by weight based on the entire lubricating oil composition.

The synthetic oil is a polyalkylene glycol. In particular, the polyalkylene glycol has a viscosity of 100 to 250 mm ² / s at 40 ° C.
The molybdenum compound is molybdenum dithiocarbamate (hereinafter referred to as MoDTC).

The rolling bearing of the present invention is used by being incorporated in a speed reducer or a hydraulic device, and is oil-lubricated with the above lubricating oil composition.
Further, the rolling bearing is used under a condition where a radial load of 6500 N or more is applied.

  The lubricating oil composition of the present invention comprises 0.1 to 10% by weight of a molybdenum compound as an additive in a synthetic oil such as polyalkylene glycol, based on the total lubricating oil composition. By using it for a rolling bearing incorporated in a reduction gear or a hydraulic device to be used, it is possible to prevent specific peeling due to hydrogen embrittlement on the bearing sliding surface and to improve the bearing life.

  Since the rolling bearing of the present invention is oil-lubricated with the above lubricating oil composition, it is used when incorporated in a reduction gear for an industrial machine or hydraulic equipment that is subjected to heavy load or high vibration at low speed rotation. Further, specific peeling due to hydrogen embrittlement on the sliding surface of the bearing can be prevented, and the durability life can be improved without increasing the load capacity.

  In rolling bearings incorporated in reduction gears and hydraulic equipment for industrial machines, the inventors have intensively studied a lubricating oil composition that can improve the durability life without improving the load capacity. As described above, in rolling bearings used for reducers for industrial machines and hydraulic equipment, the rolling surface is specularly worn due to conditions such as low-speed rotation, heavy load, and high vibration, resulting in catalysis of the new surface. Lubricating oil decomposes and flaking is expected to occur due to the hydrogen generated. On the other hand, in the present invention, a lubricating oil in which 0.1 to 10% by weight of a molybdenum compound such as MoDTC is added as an additive to a synthetic oil such as polyalkylene glycol for oil lubrication of this rolling bearing. It has been found that the use of the composition significantly improves the life of the rolling bearing. This is because the molybdenum compound film formed on the bearing rolling surface by blending the molybdenum compound suppresses the generation of hydrogen due to the decomposition of the lubricating oil by the catalytic action of the metal surface, and prevents the unique peeling due to hydrogen embrittlement. It is considered possible. The present invention has been completed based on such findings.

Synthetic oils that can be used in the lubricating oil composition of the present invention include hydrocarbon-based synthetic oils such as polybutene, poly-α-olefin, alkylnaphthalene, and alicyclic compounds, polyol ester oils, phosphate ester oils, Non-hydrocarbon synthesis such as polymer ester oil, aromatic ester oil, carbonate ester oil, diester oil, polyglycol oil such as polyalkylene glycol, silicone oil, polyphenyl ether oil, alkyldiphenyl ether oil, alkylbenzene oil, fluorinated oil, etc. Examples include oil.
Of these, polyalkylene glycol is preferably used because it has a high viscosity index. Moreover, these can be used individually or in combination of 2 or more types.

The viscosity of the polyalkylene glycol used in the present invention is preferably 100 to 250 mm ² / s at 40 ° C. If it is less than 100 mm ² / s, wear increases, and if it exceeds 250 mm ² / s, the rotational torque increases, causing inconvenience.

Examples of the molybdenum compound that can be used in the present invention include organic molybdenum compounds such as MoDTC and molybdenum dithiophosphate, and inorganic molybdenum compounds such as sodium molybdate, potassium molybdate, lithium molybdate, magnesium molybdate, and calcium molybdate.
Among these, it is preferable to use MoDTC because of its excellent wear resistance.

  In the lubricating oil composition of the present invention, it is essential that the blending ratio of the molybdenum compound is 0.1 to 10% by weight with respect to the entire lubricating oil composition. In this blending ratio, it is preferably 0.3 to 5% by weight. If the blending amount is less than 0.1% by weight, it becomes difficult to prevent specific peeling due to hydrogen embrittlement on the bearing sliding surface. If the blending amount exceeds 10% by weight, the delamination-suppressing effect reaches its peak and the cost increases.

  In the lubricating oil composition of the present invention, an antioxidant, a rust inhibitor, an oiliness agent, a viscosity index improver, a pour point depressant, an antifoaming agent, etc., as necessary, as long as the effects of the present invention are not impaired. A well-known compounding agent can be mix | blended.

A rolling bearing according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a tapered roller bearing showing an embodiment of the present invention. The tapered roller bearing 18 shown in FIG. 1 is a tapered roller bearing that supports the first planetary gear 13 of the reduction gear shown in FIG.
The tapered roller bearing 18 is composed of a pair of bearing units 1 and 1 in combination on the back surface, and a spacer 2 is incorporated between the opposed surfaces. The receiving unit 1 includes an outer ring 3, a flanged inner ring 4, and a tapered roller 5. In the tapered roller bearing 18 having the above-described configuration, the above-described lubricating oil composition is oil-lubricated by an oil bath or circulating oil supply in a state where the tapered roller bearing 18 is incorporated in a reduction gear shown in FIG.

FIG. 2 is a cross-sectional view of an angular ball bearing showing another embodiment of the present invention. An angular ball bearing 20 shown in FIG. 2 is an angular ball bearing 20 that rotatably supports the sprocket 16 on the axle of the reduction gear shown in FIG.
This angular ball bearing 20 is an angular ball bearing in which a rolling element 8 is held by a cage 9 between an outer ring 6 and an inner ring 7. A straight line connecting the rolling elements 8 and the contact points of the outer ring 6 and the inner ring 7 has a contact angle α with respect to the radial direction, so that a radial load and an axial load in one direction can be applied. In the state where the angular ball bearing 20 is incorporated in the speed reducer shown in FIG. 3, the above-described lubricating oil composition is oil-lubricated by an oil bath or circulating oil supply.

  Since each of the bearings is used for a planetary gear type reduction gear of a hydraulic excavator, a heavy load is applied during low-speed rotation. Specifically, a radial load of 6500 N or more is applied as a heavy load.

  In the above embodiment, the case where the present invention is applied to a tapered roller bearing and an angular ball bearing as the rolling bearing has been described. However, the present invention can also be applied to rolling bearings such as deep groove ball bearings, needle roller bearings, and self-aligning roller bearings. Can be applied.

Examples 1 to 6
A lubricating oil composition was obtained by blending MoDTC with a polyalkylene glycol oil having a viscosity of 100 to 250 mm ² / s at 40 ° C. at a blending ratio shown in Table 1. Using this lubricating oil composition, the following bearing durability test was carried out, and the time until the raceway surface of the bearing peeled is also shown in Table 1.

Comparative Example 1
Using a polyalkylene glycol oil having a viscosity of 100 to 250 mm ² / s at 40 ° C., the bearing durability test shown below was performed, and the time until the bearing raceway surface peeled is also shown in Table 1.

<Bearing endurance test>
A deep groove ball bearing (manufactured by NTN: nominal number 6206) was used, and it was operated under oil lubrication at a rotational speed of 3000 rpm and a radial load of 6860 N. The time until the bearing raceway surface peeled off and abnormal vibration was detected was measured.

表１に示すように、ポリアルキレングリコール油にＭｏＤＴＣを所定量配合した各実施例は、ポリアルキレングリコール油単独である比較例１と比較して、軸受寿命が大幅に向上したことが分かる。

As shown in Table 1, it can be seen that each example in which a predetermined amount of MoDTC was blended with polyalkylene glycol oil significantly improved the bearing life as compared with Comparative Example 1 in which the polyalkylene glycol oil was used alone.

  The lubricating oil composition of the present invention can prevent specific peeling due to hydrogen embrittlement on the sliding surface of the bearing using the lubricating oil composition, thereby improving the bearing life. For this reason, it can be suitably used as a rolling bearing incorporated in a reduction gear or hydraulic equipment of a large construction machine or industrial robot.

It is sectional drawing of the tapered roller bearing which shows one Embodiment of this invention. It is sectional drawing of the angular ball bearing which shows other embodiment of this invention. It is a partially cutaway sectional view showing a planetary gear type speed reducer of a hydraulic excavator.

Explanation of symbols

1 Bearing unit 2 Spacer 3 Outer ring,
4 Inner ring with flange 5 Tapered roller 6 Outer ring 7 Inner ring 8 Rolling element 9 Cage 10 Input shaft 11 Drive gear 12 Internal gear 13 First planetary gear 14 Intermediate gear 15 Second planetary gear 16 Drive sprocket 17 Crawler belt 18, 19 Tapered roller Bearing 20, 21 Angular contact ball bearing

Claims (6)

A lubricating oil composition for a rolling bearing used in a reduction gear or a hydraulic device,
The lubricating oil composition comprises a synthetic oil and a molybdenum compound as an additive, and the blending ratio of the molybdenum compound is 0.1 to 10% by weight based on the entire lubricating oil composition. Oil composition.   The lubricating oil composition according to claim 1, wherein the synthetic oil is a polyalkylene glycol. Wherein the poly viscosity alkylene glycol, lubricating oil composition of claim 2, wherein it is 100 to 250 mm ² / s at 40 ° C..   The lubricating oil composition according to claim 1, 2 or 3, wherein the molybdenum compound is molybdenum dithiocarbamate. A rolling bearing used by being incorporated into a reduction gear or a hydraulic device and lubricated with a lubricating oil composition,
The rolling bearing according to claim 1, wherein the lubricating oil composition is the lubricating oil composition according to claim 1. The rolling bearing according to claim 5, wherein the rolling bearing is used under a condition where a radial load of 6500 N or more is applied.

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