JP2002147472A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing in which a grease with a less heat generation under a high speed rotation is filled as a lubricant. SOLUTION: The rolling bearing 1 adopts a grease lubrication. In a grease filled in the rolling bearing 1, a base oil contains carbonate of 10-100 wt.% and a kinematic viscosity of the base oil becomes 10×10-6 (m2/s) to 200×10-6 (m2/s).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a lathe, a drilling machine,
Rolling bearings suitable for main shaft bearings of machine tool devices such as boring machines, milling machines, grinding machines, honing machines, super finishing machines, lapping machines, etc. The present invention relates to a rolling bearing capable of improving the life.

[0002]

2. Description of the Related Art In general, a main shaft of a machine tool device rotates while being supported by any one of an angular ball bearing, a cylindrical roller bearing, and a combination of these rolling bearings. The spindle of the machine tool device is required to rotate at high speed in order to improve machining accuracy and productivity, but as the rolling bearing that supports the spindle is used under high speed rotation,
Heat generation and increased preload significantly increase the risk of seizures and bearing damage.

In order to prevent such a situation, and to prevent the entire machine tool from being thermally deformed and the machining accuracy from being lowered, an appropriate lubrication method is selected to minimize the heat generation of the bearing supporting the main shaft. Must be suppressed. For this reason, conventionally, the lubrication of rolling bearings that support a machine tool main shaft rotating at high speed has a cooling effect, an oil-air lubrication method,
A nozzle jet lubrication method or an underrace lubrication method (a method of lubricating the track surface from below) has been adopted.

Here, oil lubrication is generally used as a lubrication system for a rolling bearing that supports a high-speed rotating main shaft.

[0005]

In each of the above-mentioned conventional lubrication systems, it is essential to introduce a lubrication device for supplying lubricating oil into the bearing. For this reason, it is not only necessary to secure the area occupied by the auxiliary equipment of the lubricating device, but also disadvantageous in terms of reducing the operating cost. For this reason,
The use of grease lubricated rolling bearings, which can be expected to reduce the size of machine tool devices and reduce operating costs, is strongly required to increase the speed of machine tool spindles. For this reason, a lubrication system that is not suitable for high-speed rotation has conventionally been adopted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a rolling bearing in which grease that generates little heat even under high-speed rotation can be achieved even when grease lubrication is employed. The task is to provide. Specifically, grease lubrication and a dmn value of 130
It is intended to provide a rolling bearing that can be used for more than ten thousand.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a rolling bearing employing grease lubrication, wherein the grease sealed in the rolling bearing is 10% by weight or more of the base oil. % By weight or less is a carbonate ester, and the kinematic viscosity of the base oil is 10 × 10 ⁻⁶ at 40 ° C.
(M ² / s) or more and 200 × 10 ⁻⁶ (m ² / s) or less.

According to the present invention, a lubricating grease using a carbonate ester as the base oil has a low heat generation under high-speed shearing, has a long bearing life, and further has a machine tool for machining. This is due to the finding that the accuracy is improved (see FIG. 3). The reason why 10% by weight or more and 100% by weight or less of the base oil is carbonic acid ester is as follows.

[0009] The greater the distribution of the carbonate ester in the base oil, the more the heat generation is reduced. If the amount of the carbonate is less than 10% by weight based on the total amount of the base oil, a sufficient heat generation reducing effect cannot be expected (see FIG. 4). For this reason, the lower limit is set to 10% by weight. In particular, when the amount of the carbonate is 30% by weight or more with respect to the total amount of the base oil, the effect of reducing the heat generation due to the increase of the carbonate becomes small, and the temperature of the bearing outer ring can be suppressed to 50 ° C or less. Therefore, the amount of the carbonate based on the total amount of the base oil should be 30% by weight or more and
It is preferable that the content be not more than% by weight (see FIG. 4).

The kinematic viscosity of the base oil is 10 × 10 4 at 40 ° C.
^-6 to 200 × 10 ^-6 (m ² / s) for the following reason. Base oil kinematic viscosity at 40 ° C is 200 × 10
^If it exceeds ^-6 (m ² / s), the heat generation increases rapidly due to an increase in the viscosity during high-speed rotation, and as a result, the seizure life of the bearing is sharply shortened. Therefore, the upper limit is 2
00 × 10 ⁻⁶ (m ² / s) (see FIG. 5).

On the other hand, the base oil kinematic viscosity at 40 ° C. is 10 × 10
^If it is smaller than ^-6 (m ² / s), the thickness of the lubricating oil film formed during the rotation of the bearing is less than the necessary minimum limit, the sufficient load supporting capacity cannot be maintained, and the seizure life is shortened (FIG. 5). reference). Therefore, the lower limit is set to 10 × 10 ⁻⁶ (m ² / s). Then, the kinematic viscosity of the base oil is set to 10 × 10 ⁻⁶ at 40 ° C.
By setting it to 200 × 10 ⁻⁶ (m ² / s), long-term durability of the bearing can be ensured.

Particularly, the grease has a kinematic viscosity of base oil at 40 ° C. of 10 × 10 ⁻⁶ (m ² / s) or more and 130 × 10 ⁻⁶ (m ² / s).
If s) or less, the temperature of the bearing outer ring can be suppressed to 50 ° C. or less, and the life of the bearing becomes the best. That is, the kinematic viscosity of the base oil at 40 ° C. is 10 × 10 ⁻⁶ (m ² / s) or more and 130 × 1
It is more preferred to be 0 ^-6 (m ² / s) or less. Here, the amount of grease to be enclosed is 1 to the bearing space volume.
It is effective to prevent the temperature from rising at 0 to 50% by volume under high-speed rotation (see FIG. 6).

The bearing space volume is the volume of the space formed between the inner ring and the outer ring.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, an angular ball bearing suitable for supporting a main shaft of a machine tool rotating at high speed will be described as an example. FIG. 1 is a sectional view of a main part of the ball bearing. That is, the ball bearing 1 of the present embodiment is configured such that a plurality of balls 4 (rolling elements) are interposed between the inner ring 2 and the outer ring 3 arranged coaxially, and the inner diameter side of the inner ring 2 is the main shaft 6. It is fixed so as to be integral with the body. In FIG. 1, reference numeral 5 denotes a cage.

Grease is sealed in the space between the inner and outer rings 3. The grease contains 10 to 100% by weight of a carbonate based on the total amount of the base oil, and the kinematic viscosity of the base oil is 10 × 10 ⁻⁶ to 200 × 10 ⁶ at 40 ° C.
^-6 (m ² / s). Here, the thickener of the grease is not particularly limited. For example, lithium soap, lithium complex soap, barium soap, barium complex soap, aluminum soap, aluminum complex soap, sodium soap, urea compound, calcium sulfonate, and sodium-calcium soap, lithium-calcium soap, and sodium which are mixed soaps -Aluminum soap and the like can be used.
Examples of the antioxidant added to the grease include amine compounds such as phenyl-α-naphthylamine, phenols such as di-t-butyl-P-cresol, thioamines such as phenothiazine, dialkyldithiophosphates, and dialkyldithiocarbamines. Acid salts and the like can be exemplified.

When the rolling bearing 1 having the above structure is used, since grease lubrication is used, it is not necessary to introduce a bearing lubrication device.
It is possible to reduce the size and reduce the operating cost of the machine tool. Also, despite the grease lubrication, even if the spindle 6 rotates at a high speed of 1.3 million or more with dmn value of 1.3 million or more, the heat generation of the bearing 1 can be suppressed to 55 ° C. or less. Is suppressed, and a decrease in processing accuracy is prevented.

[0017]

EXAMPLES The rolling bearing according to the present invention was evaluated for heat generation at high speed rotation of the bearing 1. As the bearing, an angular contact ball bearing 140BNC10TP4 was used, and 1.0 g of grease was sealed in the bearing. The grease filling amount corresponds to 15% by volume of the bearing space volume.

The grease used was lithium soap as a thickener, and the amount of the thickener was unified so as to be 15% by weight based on the total amount of the grease. Also,
As base oils, all have a kinematic viscosity at 40 ° C. of about 30 × 10 ^−6.
(M ² / s) oil was used. Then, four types of rolling bearings 20 each using 100% by weight of a carbonate ester, an ester, a synthetic hydrocarbon, and a mineral oil as base oils of the grease to be sealed were prepared and tested.

That is, two test bearings 1 were prepared for each of the above-mentioned types of rolling bearings 1, and evaluation was performed using a test machine as shown in FIG. The testing machine has a spindle structure in which the main shaft 6 is supported by two test bearings 20 arranged in a back-to-back combination, and the main shaft 6 is rotationally driven via a motor and a transmission (not shown). Also,
A through hole for supplying lubricant in a radial direction is provided at a substantially central portion in the axial direction of the testing machine main body 24 and at an intermediate position between the two test bearings 20. Is inserted. The oil air nozzle 21 has a structure that can be replaced with a grease nipple.
Further, an exhaust path 23 is provided for exhausting the air in the set space of the bearing 20.

Further, a thermocouple 25 is provided to measure the temperature rise of the bearing outer ring 20a. The preload (axial clearance) of the bearing 20 is a constant value (60 kg) at a spacer or the like.
To prevent the temperature rise due to the difference in preload from being affected. After the rotation of the main shaft 6 reached a predetermined number of revolutions, the temperature was left to stand for about 2 hours to saturate the heat generation temperature, and then the temperature of the bearing outer ring 20a was measured. The above test was repeated with various changes in the predetermined number of revolutions.

FIG. 3 shows the result. FIG. 3 summarizes the dependence of the heat generation characteristics of each prototype grease on the dmn value. As can be seen from FIG. 3, when grease using carbonate ester as a base oil is used as a lubricant, the bearing 20 generates less heat even when used under high-speed rotation as compared with a case where another grease is used as a lubricant. You can see that there is. This is because the base oil using a carbonate ester has a low viscosity, and has good adhesion to the raceway surface of the bearing 20 and the rolling surface or sliding surface which is a metal surface such as a rolling element and a cage. This is because the wettability is superior to that of the base oil, and the thin film is quickly formed on the raceway surface and the like, and has the effect of increasing the wear resistance and impact resistance. Further, since the heat generation is low, the oil film forming ability at a low torque is excellent. Also, it has excellent heat resistance.

From the viewpoint of grease life, the bearing 2
The lower the heat generation during the zero revolution, the better. Specifically, if the bearing outer ring temperature is 55 ° C. or lower, a long life can be expected. As shown in FIG. 3, by using grease containing carbonate ester as a base oil as a lubricant, the bearing outer ring temperature is less than 55 ° C. even when the main shaft 6 is rotated at a high speed at which the dmn value becomes 1.3 million or more. It can be seen that it can be suppressed to.

Here, a similar test was carried out by changing barium complex soap and calcium sulfonate as thickeners for grease, but the same tendency was observed, that is, the thickeners were affected. Without
The superiority of the base oil using carbonate ester was confirmed. Next, a carbonate ester having a kinematic viscosity at 40 ° C. of 30 × 10 ⁻⁶ (m ² / s) and a kinematic viscosity at 40 ° C. of 30 × 10 ^−6.
A grease using a mixed oil with (m ² / s) mineral oil as a base oil was used, and a test was performed using the same testing machine as described above to determine the temperature of the bearing outer ring.

Here, lithium soap was used as the thickener, and its amount was 15% by weight based on the total amount of grease. Grease filling amount is 15% by volume of bearing 20 space volume
It is. Rotation test: dmn 1.3 million, preload 60
kg. Then, using a grease in which the mixing ratio of the mixed oil serving as the base oil was changed, the bearing outer ring temperature was obtained. The measured temperature was a dmn value of 13
Each was left for about 2 hours in a high-speed rotation state of 100,000 to saturate the temperature.

FIG. 4 shows the result. As can be seen from FIG. 4, the mixing ratio of the carbonate ester to the whole base oil is 10%.
When the content is not less than% by weight, the temperature of the bearing outer ring can be suppressed to 55 ° C. or less, and severe operating conditions are relaxed. In particular, when grease having a compounding ratio of carbonate ester of 30% by weight or more with respect to the entire base oil is used, the temperature of the bearing outer ring becomes 50
° C or lower. Further, even if the ratio of the carbonate ester to the whole base oil is more than 30% by weight, the effect of reducing the temperature of the bearing outer ring is gradually reduced, and the temperature of the bearing outer ring does not largely change.

On the other hand, it can be seen that the effect of reducing the temperature of the bearing outer ring cannot be obtained when grease containing less than 10% by weight of the carbonate ester relative to the total amount of the base oil is used. That is, it can be seen that the heat generation of the bearing 20 can be effectively suppressed by setting the mixing ratio of the carbonate ester to the entire base oil to 10% by weight or more, preferably 30% by weight or more.

Next, the relationship between the kinematic viscosity of the base oil and the bearing seizure life when the carbonate oil is used as the base oil, and the relationship between the kinematic viscosity and the temperature of the bearing outer ring during rotation using the above-described test machine were measured under the same conditions. Was tested. That is, the test conditions used were a grease containing 15% by weight of the total amount of lithium soap as a thickener, and the amount of grease sealed in the bearing 20 was set to 15% of the bearing space volume. The rotation test was performed with dmn of 1.3 million and a preload of 60 kg.

A test was conducted on a plurality of bearings 20 in which the base oil kinematic viscosity at 40 ° C. of the grease to be sealed was changed, and the results shown in FIG. 5 were obtained. In addition, each bearing 20 is allowed to stand at the target rotational speed for about two hours to achieve saturation of the heat generation temperature. Here, the concentration of the base oil of the carbonate ester shown on the horizontal axis in FIG. 5 is determined by adding the carbon chain length of about C _{4 to} C ₁₀ in addition to the carbonate chains having an alkyl chain length of 1 or 2 such as dimethyl carbonate and diethyl carbonate. The resulting carbonic acid esters were mixed to create viscosities of various base oils (at 40 ° C.) and subjected to the above test. This is an example of changing the base oil viscosity.

As can be seen from FIG. 5, when the kinematic viscosity of the base oil at 40 ° C. becomes larger than 200 × 10 ⁻⁶ (m ² / s), the heat generation due to the increase in the viscosity sharply increases.
The baking life of 0 is sharply shortened. On the other hand, when the kinematic viscosity of the base oil at 40 ° C. becomes smaller than 10 × 10 ⁻⁶ (m ² / s),
The thickness of the lubricating oil film formed during the rotation of the bearing 20 is less than the necessary minimum limit, so that the sufficient load supporting ability cannot be maintained, and the seizure life is shortened.

As described above, grease base oil at 40 ° C.
10 × 10 kinematic viscosity^-6(M^Two/ S) more than 200 × 10^-6
(M^Two/ S), the long-term durability of the bearing 20
It can be seen that long-term performance can be achieved. In particular, grease 4
Base oil kinematic viscosity at 0 ° C is 10 × 10^-6(M^Two/ S) 1 or more
30 × 10^-6(M^Two/ S), the temperature of the bearing outer ring
Is maintained at 50 ° C. or less, and the life of the bearing 20 becomes the best.
You. That is, the base oil kinematic viscosity at 40 ° C. is 10 × 10
^-6(M^Two/ S) more than 130 × 10^-6(M^Two/ S)
It becomes a more preferable range.

Next, the relationship between the amount of grease to be enclosed, the temperature of the bearing outer ring during rotation, and the remaining amount of grease after rotating for a predetermined time (after 20 hours) was determined using the above-described tester. The grease (lubricant) used was carbonate ester as a base oil, and the kinematic viscosity of the base oil at 40 ° C. was 30.
× 10 ⁻⁶ (m ² / s), and lithium soap (15% by weight based on the total amount of grease) was used as a thickener. The rotation test was performed with dmn of 1.3 million and a preload of 60 kg.

FIG. 6 shows the result. Here, the remaining amount of grease was determined by stopping the rotation after 20 hours from reaching the target rotation speed, disassembling the tester, and measuring the mass of the bearing 20. In addition, the initial grease filling amount and the remaining grease amount were evaluated based on the ratio to the bearing space volume.

As can be seen from FIG. 6, when the initial grease filling amount is less than 10% by volume of the bearing space area, the lubrication is insufficient and the temperature rises abnormally. On the other hand, as the initial filling amount increases, the amount of residual grease in the bearing 20 increases little by little, which is advantageous for durability.
Abnormal temperature rise occurs due to the stirring resistance of the lubricant. Therefore, the amount of grease to be sealed is desirably 10% by volume or more and 50% by volume or less of the space volume of the bearing 20.

FIG. 7 summarizes the results of the above tests. That is, the rolling bearing 2 according to the present invention
0 indicates that the bearing 20 is good in that heat generation is suppressed even when used at high speeds, despite the adoption of grease lubrication.

[0035]

As described above, by employing the present invention, it is possible to provide a grease-lubricated rolling bearing capable of suppressing heat generation even when used in a rotating state where the rotating speed is 1.3mn or more. Becomes In addition, since the grease lubrication system is used, it is possible to reduce the size of the device incorporating the rolling bearing and reduce the operating cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a rolling bearing according to an embodiment according to the present invention.

FIG. 2 is a cross-sectional view illustrating a tester used in an example.

FIG. 3 is a diagram showing a relationship between a dmn value and a bearing outer ring temperature in an example.

FIG. 4 is a diagram showing the relationship between the concentration of carbonate in a base oil and the temperature of a bearing outer ring.

FIG. 5 is a diagram showing the relationship between base oil kinematic viscosity, bearing outer ring temperature, and bearing seizure life.

FIG. 6 is a diagram showing a relationship between an initial grease filling amount, a bearing outer ring temperature, and a grease remaining amount.

FIG. 7 is a diagram summarizing the results of all tests of the examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball bearing 2 Inner ring 3 Outer ring 4 Ball 6 Main shaft 20 Test bearing 20a Outer ring 25 Thermocouple

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C10N 20:02 C10N 40:02 40:02 50:10 50:10 B23Q 1/26 DF term ( Reference) 3C011 FF06 3C048 CC04 DD11 EE02 3J101 AA02 AA13 AA54 AA62 EA63 FA33 FA44 GA31 4H104 BB37A EA02A PA01 QA18

Claims (1)

[Claims] In a rolling bearing employing grease lubrication, the grease sealed in the rolling bearing is such that 10% by weight or more and 100% by weight or less of a base oil are carbonate esters, and that the grease is lubricated. Viscosity 10 × 10 ^-6 at 40 ° C.
(M ² / s) or more and 200 × 10 ⁻⁶ (m ² / s) or less.