JP4026276B2 - Rolling bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has a d _m n value (average dimension d _{m of} bearing inner diameter and outer diameter ≒ product of pitch circle diameter D _p (mm) of rolling element and rotation speed n (rpm)) of 1.3 million or more. The present invention relates to a grease suitable for a rolling bearing used under high-speed rotation.
[0002]
[Prior art]
Conventionally, angular contact ball bearings and cylindrical roller bearings are used alone or in combination as bearings for machine tool spindles. The machine tool spindle is desired to rotate at a high speed in order to improve machining accuracy and productivity. However, when a rolling bearing is used under high speed rotation, there is a risk of seizure or damage due to abnormal heat generation or increased load. Further, when the entire machine tool is thermally deformed due to heat generated in the bearing, the machining accuracy of the machine tool may be lowered.
[0003]
In order to prevent such abnormal heat generation of the bearing, conventionally, a cooling effect such as an oil-air lubrication method, a nozzle jet lubrication method, an under-race lubrication method, etc. is used as a lubrication method for a bearing for a machine tool main spindle that rotates at high speed. Oil lubrication has been adopted. However, these methods require a large-scale device for supplying the lubricating oil, and thus there is a problem that not only the space is taken up but also the device cost is high.
[0004]
Since there is no such problem in the grease lubrication method, it is desired to employ the grease lubrication method as a lubrication method for rolling bearings used under high-speed rotation. Conventional greases used for lubricating machine tool spindle bearings include barium soap grease containing barium soap thickener made of barium soap and barium composite soap, and lithium soap and lithium composite soap. There is a lithium soap grease containing a lithium soap thickener.
[0005]
Since barium soap grease generally has a high content of thickener, it has a feature that when used in a bearing (when the bearing is rotated), the grease hardly leaks from the bearing. In addition, there is a feature that the oil separation property of the grease in the bearing is small. Therefore, when the bearing is used at a rotational speed that is not so high, oil is supplied little by little from the grease to the raceway surface of the bearing. The rise is kept low. That is, when the bearing is used at a rotational speed that is not so high, a long-term stable lubricating effect can be obtained by the barium soap-based grease.
[0006]
Lithium soap grease generally has a low content of thickener and has an appropriate oil releasing property. Therefore, when the bearing is used at a rotational speed that is not so high, a long-term stable lubricating effect can be obtained even if lithium soap grease is used.
[0007]
[Problems to be solved by the invention]
However, if barium soap-based grease is used for lubrication of bearings used under high-speed rotation with a d _m n value of 1.3 million or more, the amount of oil supplied to the raceway surface is low because the grease is less oil-releasable in the bearings. Is insufficient, and there is a problem that seizure is likely to occur in the bearing at an early stage.
[0008]
In the case of lithium soap grease, for initial release oil is high, even under high speed rotation d _m n value is more than 1.3 million, although certain period of the setup has good lubricity, long term It is difficult to ensure stable lubricity. That is, if the lubrication method using lithium soap grease is continued for a long time under high speed rotation as described above, a large amount of grease may leak from the bearing. Further, since the oil separation property of the grease in the bearing is high, the supply of oil to the raceway surface becomes excessive, the shear heat generation amount increases, and the bearing may become very hot.
[0009]
Thus, the conventional grease lubrication method was not an appropriate method as a lubrication method for rolling bearings used under high-speed rotation with a d _m n value of 1.3 million or more.
The present invention has been made in view of the problems of the prior art, even rolling bearing d _m n values are used under high-speed rotation is more than 1.3 million, the grease lubrication method An object is to ensure long-term stable lubricity.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention , the thickener contained in the present invention is a barium soap thickener comprising barium soap and / or barium composite soap, and lithium soap comprising lithium soap and / or lithium composite soap. a system thickener as an essential component, the content of barium soap thickener to the total amount of barium soap thickeners, lithium soap thickener is a 6 0 wt% or more and 9 0 wt% or less Use grease characterized by this.
[0011]
According to this grease, even when the d _m n value was used rolling bearing is used under high speed rotation is more than 1.3 million, the temperature rise of the bearing kept low with the oil to the raceway surface is moderately supplied Therefore, stable lubricity can be ensured in the long term.
Even if the grease contains a thickener comprising a barium soap thickener and a lithium soap thickener, if the content is less than 20% by weight, the content of the lithium soap thickener is It becomes excessive and oil release properties become too high. Therefore, when used in a rolling bearing used under high-speed rotation with a d _m n value of 1.3 million or more, the oil stirring resistance increases, the shear heating value increases, and the bearing becomes very hot. There is a fear. Moreover, since grease is likely to be scattered, the amount of oil on the raceway surface may be insufficient.
[0012]
Even if the grease contains a thickener composed of a barium soap thickener and a lithium soap thickener, if the content exceeds 90% by weight, the content of the lithium soap thickener is insufficient. As a result, the oil release property becomes too small. Therefore, when it is used for a rolling bearing used under high-speed rotation with a d _m n value of 1.3 million or more, the temperature rise of the bearing can be suppressed low, but the amount of oil supplied to the raceway surface is small. Run short.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
A test to check the endurance life and temperature rise by rotating an angular contact ball bearing (65BN10) for machine tool spindles in a state where the thickener is lubricated with grease comprising a barium soap thickener and / or a lithium soap thickener. Went. The angular ball bearing used has an inner diameter of 65 mm, an outer diameter of 100 mm, a width of 18 mm, and the balls are made of ceramics.
[0014]
As the barium soap grease, a commercial product was prepared in which the thickener was a barium composite soap, the base oil was an ester, the content of the thickener was 33.3% by weight, and the blending degree was 280. . As a lithium soap grease, a commercially available product in which the thickener is composed of lithium composite soap, the base oil is a synthetic hydrocarbon, the content of the thickener is 13.6% by weight, and the blending degree is 280. Prepared.
[0015]
By mixing these two greases in each mixing ratio, the thickener contained is a mixture of a barium soap-type thickener and a lithium soap-type thickener, and the barium composite soap in the total thickener is mixed. Each grease having a content of 10 to 90% by weight was prepared. The rotation test was performed using two greases (the barium composite soap content is 0 and 100% by weight) that are not mixed with these mixed greases. The amount of grease charged was 2.3 g corresponding to 15% of the volume of the bearing space.
[0016]
It should be noted that the content of the thickener in each grease varies depending on the mixing of the two greases, and is as follows. When the content of barium composite soap in the total thickener is 10% by weight, it becomes 15.6% by weight. When this content is 20% by weight, it becomes 17.5% by weight, and 30% by weight. Is 19.5% by weight, 40% by weight is 21.5% by weight, 50% by weight is 23.5% by weight, and 60% by weight 25.4% by weight, 27.4% by weight for 70% by weight, 29.4% by weight for 80% by weight, and 31.3% by weight for 90% by weight. It becomes.
[0017]
The test apparatus of FIG. 1 was used for this rotation test. In this test apparatus, four bearings J are attached between the shaft 1 and the housing 2, and an intermediate member 3 that forms a grease supply space 31 is installed between the adjacent bearings J. Yes. A grease cup 4 is attached in the vicinity of each bearing J. The tip of each grease cup 4 passes through the housing 2 and the outer peripheral member 32 of the intermediate member 3 and reaches the grease supply space 31.
[0018]
A grease discharge space 21 is formed at a position facing the grease cup 4 across the shaft 1 of the housing 2. The intermediate member 3 is formed with a discharge hole 33 that allows the grease discharge space 21 and the grease supply space 31 to communicate with each other. Mounting flanges 5 are fixed to both ends of the housing 2 in the axial direction. The mounting flange 5 is formed with grease discharge holes 51 communicating with the grease discharge space 21 of the housing 2.
[0019]
A labyrinth seal 7 is formed between the shaft-side member 6 fixed to the shaft 1 and the mounting flange 5 fixed to the housing 2. The space between the shaft 1 and the housing 2 is sealed by the labyrinth seal 7. ing.
Therefore, when grease is injected into the grease cup 4, the grease is supplied from the nozzle provided at the tip of each grease cup 4 toward the inner ring and the outer ring of each bearing J. Excess grease is guided from the grease supply space 31 of the intermediate member 3 through the discharge hole 33 into the grease discharge space 21 of the housing 2 and discharged from the grease discharge hole 51 of the mounting flange 5 to the outside.
[0020]
Using this test device, over a pre-load 20kg each bearing J, while enclosing the same grease the bearings J, by rotating the shaft 1 at a rotation speed d _m n value is 1.3 million. And the time when G value showing the vibration of a testing machine became 20 or more was measured as a durable life. Also, before the start of the test, the temperature of the bearing was measured when the bearing temperature becomes constant after the d _m n value reaches 1.3 million was calculated temperature rise value of before and after the rotation test bearings. These results are shown graphically in FIG.
[0021]
As can be seen from this graph, when the barium composite soap content in the total thickener contained in the grease used is less than 20% by weight, the temperature rise of the bearing increases to 37 ° C. or more, and the durable life of the bearing. Becomes extremely short. Further, if the barium composite soap content exceeds 97% by weight, the durability life of the bearing is extremely shortened. Therefore, by using the grease containing a thickener wherein the barium complex soap content is 20 weight% or more 97 wt% or less, even under high-speed rotation of the d _m n value 1.3 million, the temperature rise of the bearing It can be seen that the durable life of the bearing can be made sufficiently long while suppressing the above.
[0022]
Moreover, the use of grease the barium complex soap content (content of barium soap thickeners) contains a thickening agent is 97 wt% to 30 wt% or more, high-speed rotation of the d _m n value 1.3 million However, it is preferable because the durability life of the bearing becomes as long as 7000 hours or more and the temperature rise of the bearing can be suppressed to 35 ° C. or less. Further, from this graph, the more preferable barium composite soap content is 50 wt% or more and 97 wt% or less, and the more preferable barium composite soap content is 60 wt% or more and 97 wt% or less, and the more preferable It can be seen that the barium composite soap content is 60% by weight or more and 90% by weight or less.
[0023]
In this embodiment, the barium soap-based thickener is made of barium composite soap, and the lithium soap-based thickener is made of lithium composite soap, but is used for the grease of the present invention. The combination of the barium soap thickener and the lithium soap thickener used is not limited to this. For example, a combination of barium composite soap and lithium soap, a combination of barium soap and lithium composite soap, a combination of barium soap and lithium soap, a combination of barium composite soap and barium soap with lithium soap and lithium composite soap, etc. May be.
[0024]
Further, the base oil of the grease of the present invention is not particularly limited, and may be a mixture of an ester and a synthetic hydrocarbon as in this embodiment, or any of esters, ethers, and synthetic hydrocarbons, or these It may be a mixture. The blending degree of the grease of the present invention is not particularly limited. However, if the blending degree is too small, lubrication is likely to be poor, and if it is too large, grease is likely to scatter and also cause poor lubrication. It is preferable.
[0025]
【The invention's effect】
As described above, according to the rolling bearing of the present invention, because used under high speed rotation d _m n values are lubricated with a particular grease is more than 1.3 million, the oil is properly supplied to the raceway surface In addition, the temperature rise of the bearing is kept low, and stable lubricity can be ensured for a long time.
[0026]
As a result, has been a problem in the oil lubrication method had been adopted traditional, location of the problem and the cost of the apparatus of the problem can be solved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a test apparatus used in a rotation test performed in an embodiment.
FIG. 2 is a graph showing the results of tests conducted in the embodiment in relation to the bearing endurance life and temperature rise value and the content of barium composite soap in the total amount of thickener used in the grease.
[Explanation of symbols]
1 Shaft 2 Housing 3 Intermediate member 4 Grease cup 5 Mounting flange 6 Shaft side member 7 Labyrinth seal J Bearing

Claims (1)

The thickener contained in the barium soap is a barium soap-based thickener composed of barium soap and / or barium composite soap and a lithium soap-based thickener composed of lithium soap and / or lithium composite soap. wherein the content of barium soap thickeners are lubricated with 6 0 wt% to 9 0 grease or less% by weight relative to the total amount of the thickener and the lithium soap thickener, d _m n value (average dimension of bearing inner diameter and outer diameter d _m ≒ product of pitch circle diameter D _p (mm) of rolling element and rotation speed n (rpm)) used under high speed rotation of 1.3 million or more Rolling bearing.

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