ROLLING BEARING DEVICE

Abstract

Provision of a rolling bearing arrangement that ensures excellent grease lubrication stability under high-speed conditions and suppresses temperature rise during the break-in period. A rolling bearing arrangement 20 comprises an angular contact ball bearing 1 and a lubricating oil supply mechanism 11. The angular contact ball bearing 1 comprises an inner ring 2, an outer ring 3, several balls 4 arranged between the inner ring 2 and the outer ring 3, and a grease composition 7 enclosed in a bearing space between the inner ring 2 and the outer ring 3. The grease composition 7 contains a base oil with a kinematic viscosity at 40 °C of less than 120 mm². 2 / s and a thickening agent formed from a urea compound. The working penetration of the grease composition, measured according to JIS K 2220, is 230-300. The lubricating oil supply mechanism 11 is designed to supply lubricating oil into the bearing chamber in the angular contact ball bearing 1 and to supply the lubricating oil to a raceway surface.

Description

TECHNICAL AREA

[0001] The present invention relates to a rolling bearing arrangement comprising a rolling bearing and a lubricating oil supply mechanism, in particular a rolling bearing arrangement used for supporting a main shaft of a machine tool. STATE OF THE ART

[0002] A main shaft of a machine tool is preferably designed to rotate at high speed to improve machining performance, which is why various lubrication methods are used in a bearing for the main shaft. Examples of lubrication methods suitable for high-speed rotating main shafts are air-oil lubrication and oil mist lubrication.

[0003] In recent years, the demand for CO2 neutrality measures and further cost reductions has increased in the machine tool sector, which has also led to a rise in the demand for grease lubrication. Grease lubrication eliminates the need for an air-oil supply device, which is required for air-oil lubrication, as well as a device for spraying the air-oil onto the bearing. This makes grease lubrication environmentally friendly and reduces acquisition and operating costs.

[0004] With grease lubrication, the bearing is lubricated by the initial grease applied during assembly. Consequently, the grease deteriorates due to the bearing's heat generation at high speeds, making it difficult to maintain consistent lubrication. Therefore, grease lubrication must be able to withstand even higher speeds (improving lubrication stability). Generally, urea compound is used as a thickening agent in greases for high-speed rolling bearings. Urea grease forms a film of the urea compound on the bearing raceway surface, aiding lubrication. Therefore, urea grease offers superior lubrication stability at high speeds compared to metal-based greases, which do not form a similar film.

[0005] Urea grease has the advantage described above that it exhibits minimal oil separation. However, when used under even higher rotational speeds (e.g., dn value (d (inner diameter of bearing (mm)) × n (rotational speed (min-1)) = 110 × 10⁴ or more)), insufficient oil film formation may occur. Therefore, in such applications, it is preferable to add a component that promotes oil film formation. For example, patent document 1 discloses a conventional technique to address this problem, in which urea grease is used in conjunction with a grease exhibiting improved oil separation performance. STATE OF THE TECHNOLOGY PATENT DOCUMENT

[0006] Patent Document 1: JP 5916781 B SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, with the method disclosed in patent document 1, it is relatively difficult to both dispose of the grease in a storage room and to control the quantity and behavior of a base oil, so there is still room for improvement with regard to reliability.

[0008] Furthermore, in the case of rolling bearings, such as bearings for the main shaft of a machine tool operating at high speeds, the running-in process is carried out at high speeds, which can easily lead to a temporary temperature increase during the running-in period. If a significant temporary temperature increase occurs, the running-in process must be interrupted each time. Therefore, it is desirable to suppress such a temperature increase for operational reasons.

[0009] To solve these problems, the objective of the present invention is to provide a rolling bearing arrangement that can ensure the stability of lubrication under high rotational speeds with grease lubrication and suppress a temperature increase during the break-in period. MEANS TO SOLVENT THE PROBLEMS

[0010] A rolling bearing arrangement of the present invention comprises a rolling bearing and a lubricating oil supply mechanism. The rolling bearing comprises an inner ring, an outer ring, a plurality of rolling elements arranged between the inner ring and the outer ring, and a grease composition enclosed in a bearing space between the inner ring and the outer ring. The grease composition contains a base oil with a kinematic viscosity at 40 °C of less than 120 mm². 2 / s and a thickener formed from a urea compound. The working penetration of the grease composition, measured according to JIS K 2220, is 230-300. The lubricating oil supply mechanism is designed to supply lubricating oil into the bearing chamber in the rolling bearing to deliver the lubricating oil to a raceway surface.

[0011] The base oil and the lubricating oil can each be selected from the group consisting of synthetic hydrocarbon oil, ester oil and a mixed oil of hydrocarbon oil and ester oil.

[0012] The kinematic viscosity at 40 °C of the base oil and the lubricating oil can range from 10 to 50 mm. 2 / s.

[0013] The walking penetration of the fat composition, measured according to JIS K 2220, can be between 250 and 280.

[0014] The urea compound can be a diurea compound formed by the reaction of a diisocyanate component and a monoamine component with each other, and the monoamine component can contain aliphatic monoamine.

[0015] The base oil and the lubricating oil can each be selected from the group consisting of synthetic hydrocarbon oil, ester oil, and a blend of hydrocarbon oil and ester oil; the kinematic viscosity at 40 °C of the base oil and the lubricating oil can be 10 to 50 mm. 2 / s, and the walking penetration of the fat composition measured according to JIS K 2220 can be 250 to 280.

[0016] The lubricating oil supply mechanism can be designed to deliver the lubricating oil towards the vicinity of a raceway surface of the inner ring. IMPACT OF THE INVENTION

[0017] The rolling bearing arrangement of the present invention comprises: the rolling bearing, which contains the grease composition comprising the base oil with a specific kinematic viscosity at 40 °C and the thickening agent formed from the urea compound, wherein the rolling penetration of the grease composition is 230 to 300; and the lubricating oil supply mechanism, which is configured to supply the lubricating oil into the bearing chamber in the rolling bearing in order to supply the lubricating oil to the raceway surface. Accordingly, by supplying the lubricating oil, an oil deficiency on the raceway surface is prevented, so that an oil film is readily formed even under conditions of high rotational speeds, while using a urea grease which is relatively advantageous with respect to lubrication stability. As described below, the aggregation of the thickening agent is prevented by the supply of the lubricating oil, so that the progressive wear of the urea grease can be suppressed.This ensures reliable lubrication even under high-speed conditions. Furthermore, the grease composition effectively suppresses temperature rises during the break-in period.

[0018] The base oil and the lubricating oil are each selected from the group consisting of synthetic hydrocarbon oil, ester oil and a mixture of hydrocarbon oil and ester oil, and the kinematic viscosity at 40 °C of the base oil and the lubricating oil is 10 to 50 mm. 2 / s. Accordingly, the aggregation of the thickening agent is easily broken down and the lubricating oil is easily released onto the raceway surface.

[0019] The walking penetration of the fat composition, measured according to JIS K 2220, is 250 to 280. Accordingly, the aggregation of the thickening agent is further slightly disrupted.

[0020] The urea compound is a diuretic formed by the reaction of a diisocyanate component and a monoamine component, the monoamine component containing aliphatic monoamine. Accordingly, the urea compound is suitable and advantageous for preventing thickener aggregation under high-speed conditions.

[0021] The lubricating oil supply mechanism is designed to deliver the lubricating oil close to the raceway surface of the inner ring. Accordingly, the lubricating oil can be supplied to the raceway surface while suppressing the influence of torque fluctuations due to the oil supply. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a general view showing an example of a rolling bearing arrangement according to the present invention. Fig. Figure 2 is a view that shows an overview of a calculation of the adhesion work. Fig. Figures 3(a) to 3(c) are graphs showing a curve of an ester oil based on an infrared spectrum. Fig. Figures 4(a) to 4(d) are microscopic images of a fat composition. TYPE OF IMPLEMENTATION OF THE INVENTION

[0022] The inventors conducted an investigation to improve the lubrication stability of a grease lubrication under high-speed conditions. It was found that, when using a urea-based grease, as oil separation from the grease progresses and the proportion of thickening agent in the grease increases, some of the grease aggregates due to the shear caused by the bearing's rotation. Furthermore, it was found that supplying lubricating oil in such a condition eliminates the oil deficiency on the raceway surface and breaks up the aggregation of the thickening agent. The present inventions are derived from these findings.

[0023] A rolling bearing arrangement according to the present invention is used in a machine device such as a machine tool spindle, which is used particularly at high speeds. For example, the machine tool spindle comprises a rotating shaft, an inner cylinder of the housing, an outer cylinder of the housing arranged on an outer circumference of the inner cylinder, and a bearing arrangement that rotatably supports the rotating shaft relative to the inner cylinder. The bearing arrangement further comprises a rolling bearing. In this spindle, the rolling bearing can be positioned by an inner ring spacer and an outer ring spacer, each arranged on an inner ring side and an outer ring side, respectively.

[0024] An example of a rolling bearing arrangement of the present invention is given with reference to Fig. 1 described. As in Fig.As shown in Figure 1, a rolling bearing arrangement 20 comprises an angular contact ball bearing 1 and a lubricating oil supply mechanism 11, which supplies lubricating oil into a bearing chamber of the angular contact ball bearing 1. In the Fig. In the example shown, the lubricating oil supply mechanism 11 is represented by a functional block diagram.

[0025] As in Fig.As shown in Figure 1, the angular contact ball bearing 1 comprises an inner ring 2 having an inner ring raceway surface 2a on an outer circumferential surface, an outer ring 3 having an outer ring raceway surface 3a on an inner circumferential surface, several balls 4 arranged between the inner ring raceway surface 2a and the outer ring raceway surface 3a, and a cage 5 that holds the balls 4 at a specific circumferential distance. The inner ring 2 and the outer ring 3 are each in radial contact with the ball 4 at a specific angle θ (contact angle) relative to a centerline and are designed to accommodate a radial load and an axial load in one direction. The cage 5 is an outer ring guide cage and is guided by the outer ring 3 when an outer ring guide surface 5a of the cage 5 is in contact with an inner circumferential surface of the outer ring 3.The outer ring guide surface 5a is formed on a section of the outer circumferential surface (both end sections in axial direction) of the cage 5.

[0026] A specific quantity of a grease composition 7 is pre-enclosed in the bearing space between the inner ring 2 and the outer ring 3. A sealing element 6 is attached to an end section in the axial direction of the bearing space. The inner ring 2 and the outer ring 3 are each made of an iron-based metal material. The grease composition 7 is positioned between the ball 4 and the raceway surface to lubricate the bearing.

[0027] As in Fig.As shown in Figure 1, the lubricating oil supply mechanism 11 comprises a power supply unit 12, a control unit 13, a drive unit 14, a pump 15, and a tank 16. The power supply unit 12 is connected to the control unit 13 and the drive unit 14 to supply power to the control unit 13 and the drive unit 14. The control unit 13 consists, for example, of a microcomputer and is connected to the drive unit 14 to transmit a command to the drive unit 14. The drive unit 14 is a drive circuit for driving the pump 15.

[0028] The pump 15 can be configured to draw lubricating oil from the tank 16 in order to deliver a specific quantity of lubricating oil. Examples of pump 15 include a pneumatic or hydraulic piston pump, a hydraulic pump such as a gear pump, and a diaphragm pump.

[0029] The drive unit 14 drives the pump 15 based on a command from the control unit 13 to supply the lubricating oil into the bearing chamber via a nozzle 17. A distal section of the nozzle 17 extends into the interior of the bearing chamber. For example, in an inner ring rotary bearing, the lubricating oil is discharged from the nozzle 17 onto the outer circumferential surface of the inner ring 2. More precisely, the lubricating oil is discharged towards one side (one side opposite a shoulder section 2b) of the inner ring raceway surface 2a. In this case, the discharged lubricating oil moves towards the inner ring raceway surface 2a due to centrifugal force, thus eliminating the oil shortage on the raceway surface.

[0030] The oil supply quantity for each oil supply by the oil supply mechanism 11 is preferably very small, so that it does not affect the torque fluctuations of the bearing caused by the oil supply. The oil supply quantity is, for example, 0.001 to 0.1 ml. The oil supply quantity or the timing of the oil supply can be controlled, for example, based on the lubrication condition of the rolling bearing. The lubrication condition can be detected, for example, by a sensor arranged in or around the rolling bearing.

[0031] The starting grease composition, which is pre-sealed in the rolling bearing arrangement of the present invention, is a urea grease containing a base oil and a thickening agent formed from a urea compound.

[0032] Any common oil typically used in grease formulations can be used as the base oil in the grease composition. Examples of base oils include mineral oils such as paraffinic mineral oil and naphthenic mineral oil, synthetic hydrocarbon oils such as poly-α-olefin (PAO) oil, alkylbenzene oil, alkylnaphthalene oil, polyphenylene oil, synthetic naphthenic oil and polybutene oil, ester oil, ether oil, silicone oil, and fluorinated oil. Each of these base oils can be used alone or in combination with two or more of them.

[0033] Of these oils, the base oil is preferably one from the group of synthetic hydrocarbon oils, ester oils and a mixed oil of the synthetic hydrocarbon oil and the ester oil, wherein the synthetic hydrocarbon oil or the mixed oil of the synthetic hydrocarbon oil and the ester oil is even more preferred.

[0034] PAO oil, which is a synthetic hydrocarbon oil, is a mixture of α-olefins or isomerized α-olefin oligomers or polymers. Examples of α-olefins are 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-docosene, and 1-tetradocosene. A mixture of these α-olefins is typically used.

[0035] Ester oil is a compound that is liquid at room temperature and contains an ester group in its molecule. Examples of ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, and dioctyl adipate; aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellite; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane triic acid ester, and pentaerythritol ester oil; carbonate ester oil; phosphate ester oil; and polymer ester oil.

[0036] The kinematic viscosity at 40 °C of the base oil (in the case of a mixed oil, this applies accordingly to the kinematic viscosity of the mixed oil) is, for example, less than 120 mm. 2 / s. This allows the resistance to agitation to be suppressed, and, for example, the degree of temporary temperature rise during the initial operation can be reduced. The kinematic viscosity is preferably 10-50 mm. 2 / s, even more preferred 10-40 mm 2 / s. A kinematic viscosity of 10 mm 2 A value of / s or higher can prevent the base oil from evaporating during operation.

[0037] The thickening agent used in the fat composition is a urea compound obtained by the reaction of a polyisocyanate component and a monoamine component. Examples of polyisocyanate components include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Of these polyisocyanate components, aromatic diisocyanates are preferable. Alternatively, polyisocyanate obtained by the reaction of a diamine (ethylenediamine, propanediamine, etc.) and a diisocyanate that is present in excess of the diamine in the molar ratio can also be used.

[0038] Examples of the monoamine component include aliphatic monoamine, alicyclic monoamine, and aromatic monoamine. Examples of aliphatic monoamine include hexylamine, octylamine, dodecylamine, hexadecylamine, stearylamine, and oleylamine. An example of an alicyclic monoamine is cyclohexylamine. Examples of aromatic monoamine include aniline and p-toluidine.

[0039] In the present invention, aliphatic monoamine is preferably used for the monoamine component, more preferably more than 50 mol% of the aliphatic monoamine, based on the total monoamine. In this case, the monoamine component can contain only aliphatic monoamine, a combination of aliphatic monoamine and alicyclic monoamine, or a combination of aliphatic monoamine and aromatic monoamine. In a case where the monoamine component uses aliphatic monoamine, the aggregates are easily soluble.

[0040] For example, the base fat is obtained by mixing the diurea compound into the base oil as a thickening agent. The base fat containing the diurea compound as a thickening agent is formed by the reaction of the diisocyanate component and the monoamine component in the base oil. The thickening agent content is, for example, 5 to 30 wt.%, preferably 10 to 20 wt.%, more preferably more than 10 wt.% and 14 wt.% or less, and even more preferably more than 10 wt.% and 13 wt.% or less, based on the total amount (100 wt.%) of the base oil and the thickening agent.

[0041] Furthermore, a known additive can be added to the fat composition as required. Examples of additives include: an antioxidant such as an amine-based compound, a phenol-based compound, and a sulfur-based compound; an extreme pressure reagent such as phosphate (e.g., tricresyl phosphate), phosphite (e.g., tricresyl phosphite), thiophosphate, thiophosphite, zinc alkyl dithiophosphate (ZnDTP), molybdenum alkyl dithiophosphate (MoDTP), and zinc dithiocarbamate (ZnDTC); and a rust inhibitor such as calcium sulfonate and barium sulfonate.

[0042] The working penetration (JIS K 2220) of the grease composition is preferably in the range of 230 to 300, more preferably in the range of 250 to 280. As described below, if the working penetration is less than 230, the aggregates of the thickening agent are hardly loosened and the grease composition hardens, which can easily lead to vibrations. If the working penetration is more than 300, the running-in performance may be impaired.

[0043] The grease composition exhibits relatively good lubricating stability; however, at even higher speeds, a deterioration of the grease composition, a lack of oil, or vibrations on the raceway surface can occur. In this respect, the rolling bearing arrangement of the present invention can prevent oil loss by supplying the lubricating oil to the raceway surface via the oil supply and can also prevent the aggregation of the thickening agent (see, for example, [reference]). Fig. 4), so that the progression of the deterioration of the fat composition or the vibration can be suppressed.

[0044] Any of the oils described above as base oils can be used as the lubricating oil supplied by the lubricating oil supply mechanism. Preferably, a lubricating oil selected from the group consisting of synthetic hydrocarbon oils, ester oils, and blended oils of synthetic hydrocarbon oils and ester oils is used. Regarding its relationship to the base oil, for example, the lubricating oil can be the ester oil and the base oil the synthetic hydrocarbon oil or the blended oil of the synthetic hydrocarbon oil and the ester oil. The lubricating oil and the base oil can also be the same type of oil. For example, both the lubricating oil and the base oil can be the synthetic hydrocarbon oil.

[0045] The kinematic viscosity of the lubricating oil at 40 °C is preferably 10 to 100 mm². 2 / s, preferably 10 to 50 mm 2 / s. Furthermore, the kinematic viscosity of the lubricating oil at 40 °C is ± 30 mm² / s, ± 20 mm 2 / s or ± 10 mm 2 / s, based on the kinematic viscosity at 40 °C of the base oil, or alternatively, the kinematic viscosity at 40 °C of the lubricating oil can be equal to the kinematic viscosity at 40 °C of the base oil.

[0046] Taking into account compatibility with the base oil, a type of lubricating oil is preferably used that exhibits high compatibility with the base oil, or an oil whose kinematic viscosity is closer to that of the base oil. This allows the lubricating oil to easily reach the desired position (running surface or the like) after being supplied, and thus the desired effect can preferably be achieved.

[0047] The oil separation rate of the grease composition increases with increasing operating time of the rolling bearing due to the deterioration of the grease composition. When the oil separation rate of the grease composition increases, it can be difficult to form a sufficient oil film around the rolling element. In the present invention, the oil separation rate of the grease composition, which has an increased oil separation rate, can be reduced by supplying lubricating oil. For example, in a condition where the oil separation rate is 50% or more (preferably 60% or more), the oil supply can reduce the oil separation rate to 30% or less (preferably 25% or less). The oil separation rate is calculated according to the following formula (1). Oil separation rate (wt. %) = (1 − (concentration of thickener in new fat) / (concentration of thickener in used fat)) × 100

[0048] The additive(s) described in the above-described grease composition can be mixed into the lubricating oil as required.

[0049] Fig. Figure 1 shows an example where the angular contact ball bearing is used as the rolling bearing; however, the rolling bearing of the rolling bearing arrangement of the present invention can be a deep groove ball bearing, a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, a needle bearing, an axial cylindrical roller bearing, an axial tapered roller bearing, an axial needle bearing, or an axial self-aligning roller bearing.

[0050] The rolling bearing arrangement of the present invention is not limited to the one described in Fig. The example shown is limited. For example, a pump or tank can be arranged in the rolling bearing as part of the lubricating oil supply mechanism.

[0051] The rolling bearing arrangement of the present invention exhibits excellent lubrication stability even under high-speed conditions and can therefore be used for extended periods. High-speed conditions are defined in particular as a dn value of 7 × 10⁴ or more, preferably 110 × 10⁴ or more. The upper limit of the dn value is not specifically defined, but can, for example, be 200 × 10⁴. 4 or 180 × 10 4 be.

[0052] In this way, the rolling bearing arrangement can supply the lubricating oil to a rolling area of ​​the rolling bearing, resulting in long-term stability of the rolling performance and an improvement in its service life. EXAMPLE

[0053] The grease composition specified in Tables 1 and 2 is manufactured as a pre-filled grease mixture for the rolling bearing. Tables 1 and 2 specify the content of each base oil and thickener as a percentage (wt%) relative to the base grease (base oil + thickener). If the monoamine compound in the thickener is a combination of aliphatic and alicyclic monoamine, or a combination of aliphatic and aromatic monoamine, the molar ratio of the amines is set to 1:1. Furthermore, the oil type and additive used in the lubricating oil supplied by the lubricating oil delivery device are indicated with a "•" in the table columns. In Tables 1 and 2, PAO oil is used as a synthetic hydrocarbon oil. Items 1 to 8 in Table 1 also apply to Table 2.The result of Example 3 is also listed in Table 2 for comparison.

[0054] The following test is performed for each of the combinations of grease composition and lubricating oil listed in Tables 1 and 2 in order to evaluate the individual points. 1. Arrival quantity of the supplied oil based on the thickener1-1. Work of adhesion

[0055] The adhesive force of an oil-insoluble component in the grease (thickener, solid additive, etc.) of any grease formulation to a steel surface is determined as the work of adhesion. When two materials adhere to an interface, the work of adhesion is the energy required to separate the two materials. The greater the work of adhesion, the stronger the bond between the two materials. The work of adhesion is measured using the Nick Corporation's Surface Energy Contact Angle Gauge (LSE-B100), a device that allows for a simple and quantitative assessment of the adhesive force of the thickener on steel. First, a residue (undissolved organic solvent; solid component of the grease) of the grease formulation, from which the oil component (dissolved organic solvent) was extracted by Soxhlet extraction, is homogenized using a homogenizer and then diluted with gasoline to form a dipping fluid.A steel test piece (SUJ2, Ra = 0.1 µm) is immersed in the immersion fluid and the petroleum evaporates to obtain a test piece.

[0056] Two test liquids (water, diiodomethane), whose surface tension is known, are dripped onto the test piece and the contact angle θ is measured. Subsequently, a simultaneous linear equation with two unknowns is solved according to the Young-Dupre formula based on the two-component theory according to Kaelble-Uy (γtotal = γd + yp) to obtain the adhesion work W12 (see formula (2) in Fig. ). Fig. shows an overview of the calculation of adhesion work. 1-2. Arrival quantity of the supplied oil<Fettzusammensetzung mit Grundöl, das kein Esteröl enthält>

[0057] A break-in procedure with the grease composition is carried out, for example, using a machine tool durability tester at a dn value of 150 × 10⁴. Subsequently, a specific quantity of the ester oil is applied as a lubricating oil (tracer) to a specific position on the tester. The flow rate of the ester oil is measured using FT-IR. An absorption at a peak (dotted area in the infrared spectrum) is determined from the infrared spectrum. Fig. ) derived from an ester group, and the amount of movement is calculated based on the previously created calibration curve. The FT-IR of each sample to which a specific amount of the ester oil has been added to the fat composition is measured beforehand, so that the calibration curve in Fig. is obtained, which represents the relationship between the amount of ester oil added and the absorption rate. <Fettzusammensetzung mit Basisöl, das Esteröl enthält>

[0058] A break-in procedure with the grease composition is performed, for example, using a machine tool durability tester at a dn value of 150 × 10⁴. Subsequently, the lubricating oil, to which a specific amount of ZnDTP (tracer) has been added, is applied to a specific area of ​​the tester. The amount of zinc dispersed is measured using fluorescence X-rays. Again, the amount of dispersed zinc is calculated based on the previously determined calibration curve.

[0059] The results of the adhesion work and the arrival quantity of the added oil are comprehensively considered to evaluate the arrival quantity of the added oil based on the thickening agent. A favorable result is marked with "A" and an unfavorable result with "D", and the evaluation result is also shown in Tables 1 and 2. 2. Ease of resolution of thickener aggregation

[0060] A bearing test is performed, for example, at a dn value of 150 × 10⁴ using a machine tool fatigue tester. After the test, the grease composition is extracted from the bearing. This extracted grease is placed in a container and mixed with a suitable quantity of lubricating oil (the quantity at which the oil separation rate is 0% when the sample absorbs all the added lubricating oil) and stirred. The oil separation rate of the grease after stirring is then analyzed, and the reduction in the oil separation rate compared to the value before the addition of lubricating oil is determined. Furthermore, microscopic examination is performed to determine whether there is a reduction in the aggregation of the thickening agent. The reduction and the result of the microscopic examination are comprehensively considered to evaluate the ease with which the aggregation is resolved.In this assessment, a case where the reduction in the oil separation rate is 40% or more and the aggregation is refined is defined as "A"; a case where the reduction in the oil separation rate is 10% or more and less than 40% and the aggregation is refined is defined as "B"; a case where the reduction in the oil separation rate is 10% or more and less than 40% and the aggregation remains unchanged is defined as "C"; and a case where the reduction in oil separation is less than 10% and the aggregation remains unchanged is defined as "D". The assessment results are also presented in Tables 1 and 2.

[0061] Here, microscopic observation is described with reference to the Fig. 4(a) to 4(d) described. Fig. Figures 4(a) to 4(d) are microscopic images of the fat composition. Each of the Fig.Figures 4(a) to 4(d) show an image of each state of the fat composition observed with an optical microscope at a magnification of 200x. Fig. Each figure shows a new (unused) grease composition in a state where no rolling or shear forces act upon it. In these cases, no aggregation is observed, regardless of the oil separation rate. However, after driving the rolling bearing with the sealed grease composition at a high speed of dn = 150 × 10⁴, aggregation of the thickening fibers is observed, as shown in Fig. depicted. Fig. shows a state after lubricating oil has been added to the grease mixture in this state and it has been stirred. As in Fig. As shown, the oil separation rate is greatly reduced (reduction by approximately 48%) and a refinement of the aggregation can be observed. 3. Running-in behavior

[0062] A break-in period with the specified grease composition is carried out, for example, at a dn value of 150 × 10⁴, until the temperature reaches a stable temperature. When evaluating the break-in behavior, a case in which the temporary temperature rise (peak temperature) during the break-in period is 30 °C or less than the stable temperature (temperature after the break-in period) at every rotational speed is defined as "A"; a case in which the temporary temperature rise is more than 30 °C and 40 °C or less than the stable temperature is defined as "B"; a case in which the temporary temperature rise is more than 40 °C and 50 °C or less than the stable temperature is defined as "C"; and a case in which the temporary temperature rise is more than 50 °C above the stable temperature is defined as "D". The evaluation results are also shown in Tables 1 and 2.Here, the break-in operation does not include a "short-term break-in operation" in which the break-in is repeated two or three times at approximately the maximum speed for about one minute. Table 1 Example 1 2 3 4 5 6 7 8 9 Composition of the lubricating grease base oil Synthetic hydrocarbon oil 1) - - - - 87 - - - - Synthetic hydrocarbon oil 2) 88 89 88 76 - 30 - 86 90 Synthetic hydrocarbon oil 3) - - - - - 58 - - - mineral oil 4) - - - - - - 88 - - mineral oil 5) - - - - - - - - - About Esther 6) - - - 12 - - - - - Thickener Amine: Cyclohexylamine 2.3 Amine:Octylamine 4.1 3.0 3.2 3.2 3.4 3.2 3.2 3.7 2.7 Amine: p-Toluidine - - 2.6 2.6 2.9 2.6 2.6 3.1 2.2 Diisocyanate:MDI 7.9 5.7 6.2 6.2 6.7 6.2 6.2 7.2 5.1 Complex Ba soap - - - - - - - - - Base oil viscosity (mm 2 / s at 40°C) 31 31 31 31 14 53 97 31 31 Edited penetration (60 bpm) 265 265 265 265 265 265 265 230 300 lubricating oil Oil type About Esther 6) ● ● ● ● ● ● ● ● ● About Esther 7) - - - - - - - - - About Esther 8) - - - - - - - - - Additive ZnDTP - - - ● - - - - - Lubricating oil viscosity (mm) 2 / s at 40°C) 33 33 33 33 33 33 33 33 33 Evaluation Quantity of delivered oil based on the thickening agent A A A A A A A A A Easy dissolution of thickening agent aggregation A A A A A A A B A Running-in behavior A A A A A A B B A 1) 14.3 mm 2 / s at 40°C (PAO 3.5) 2) 30.7 mm 2 / s at 40°C (PAO 6) 3) 65.1 mm 2 / s at 40°C (PAO 10) 4) 97.1 mm 2 / s at 40° C (Super oil M100) 5) 136mm 2 / s at 40° C (super oil M150) 6) 32.9 mm 2 / s at 40°C (kaolube 262) 7) 45.9 mm 2 / s at 40° C (kaolube 190) 8) 90.7 mm 2 / s at 40°C (Adeka test device T90) Table 2 Example Comparative example 3 10 11 19) 2 3 4 5 Composition of the lubricating grease base oil Synthetic hydrocarbon oil 1) - - - - - - - - Synthetic hydrocarbon oil 2) 88 88 88 - - 85 91 88 Synthetic hydrocarbon oil 3) - - - - - - - - mineral oil 4) - - - - 33 - - - mineral oil 5) - - - - 55 - - - About Esther 6) - - - - - - - - Thickener Amine: Cyclohexylamine - - - - - - - - Amine:Octylamine 3.2 3.2 3.2 3.2 4.0 2.4 3.2 Amine: p-Toluidine 2.6 2.6 2.6 - 2.6 3.3 2.0 2.6 Diisocyanate:MDI 6.2 6.2 6.2 6.2 7.7 4.6 6.2 Complex Ba soap - - - 30 - - - - Base oil viscosity (mm 2 / s at 40°C) 31 31 31 - 122 31 31 31 Edited penetration (60 beats per minute) 265 265 265 - 265 210 320 265 lubricating oil Oil type About Esther 6) θ - - ● ● ● ● ● About Esther 7) - ● - - - - - About Esther 8) - - ● - - - - Additive ZnDTP - - - ● - - - Lubricating oil viscosity (mm) 2 / s at 40°C) 33 46 91 33 33 33 33 Evaluation Arrival quantity of delivered oil on A A A D A A A - base of the thickening agent Easy dissolution of thickening agent aggregation A A B - A C A - Running-in behavior A A A B D D D A 9) Mineral oil + PAO oil + Ester oil

[0063] As shown in Tables 1 and 2, in Examples 1 to 11, each using a combination of grease composition with a base oil kinematic viscosity at 40 °C of less than 120 mm² / s and a working penetration of 230–300, and adding the lubricating oil, excellent results are achieved in every evaluation. In particular, further excellent results in evaluating the ease of dissolving the thickener aggregate are achieved by adjusting the working penetration of the grease composition and the kinematic viscosity at 40 °C of the lubricating oil within suitable ranges (Examples 3 and 8 to 11). Generally, the lower the working penetration, the greater the amount of thickener, which leads to easier aggregation and more difficult dissolution (Comparative Example 3).Furthermore, comparison example 4 is superior in terms of the ease with which thickener aggregation is resolved, while its break-in performance is inferior. Since comparison example 4 exhibits high flexural penetration, which softens the grease composition, a transition from a foaming state to a channeling state is hardly initiated. Consequently, grease backflow to the raceway surface is assumed, resulting in poorer break-in performance.

[0064] As in Fig. As shown in Figure 4(c), vibration can be increased by the rolling element rolling over the aggregate if the thickener aggregate is caused by high-speed operation. In this case, the supply of lubricating oil as described above refines the aggregate through the lubricating oil and the mixing caused by the rolling, resulting in a reduction of vibration.

[0065] As described above, the combination of the specified urea grease and the supply of lubricating oil breaks down the thickener's aggregation and ensures the smooth flow of the lubricating oil. Accordingly, excellent lubrication stability can be achieved even with grease lubrication under high-speed conditions. INDUSTRIAL APPLICABILITY

[0066] The rolling bearing arrangement of the present invention can ensure lubrication stability with grease lubrication under high-speed conditions and suppress temperature rise during the break-in period. Therefore, the rolling bearing arrangement is particularly advantageous in a rolling bearing arrangement such as a bearing for a main shaft of a machine tool that is used at high speeds. LIST OF TERMS 1 Angular contact ball bearing (rolling bearing) 2 inner ring 3 Outer ring 4 balls (rolling elements) 5 cage 6 sealing element 7 Fat composition 11 Lubricating oil supply mechanism 12 Power supply unit 13 Control unit 14 Drive unit 15 pump 16 Tank 17 nozzle 20 rolling bearing arrangement QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 5916781 B

[0006]

Claims

[1] Rolling bearing arrangement comprising: a roller bearing; and a lubricating oil supply mechanism comprising the rolling bearing: an inner ring an outer ring a plurality of rolling elements arranged between the inner ring and the outer ring, and a lubricating grease composition enclosed in a bearing space between the inner ring and the outer ring, comprising a base oil with a kinematic viscosity at 40 °C of less than 120 mm² / s and a thickening agent of a urea compound, wherein the working penetration of the lubricating grease composition as measured according to JIS K 2220 is 230 to 300, and wherein the lubricating oil supply mechanism is configured to supply lubricating oil to the bearing space in the rolling bearing in order to supply the lubricating oil to a raceway surface. [2] The rolling bearing arrangement according to claim 1, wherein the base oil and the lubricating oil are each selected from the group consisting of synthetic hydrocarbon oil, ester oil and a mixed oil of the hydrocarbon oil and the ester oil. [3] The rolling bearing arrangement according to claim 1, wherein the kinematic viscosity at 40 °C of the base oil and the lubricating oil is 10 to 50 mm2 / s respectively. [4] The rolling bearing arrangement according to claim 1, wherein the working penetration of the grease composition measured according to JIS K 2220 is 250 to 280. [5] The rolling bearing arrangement according to claim 1, wherein the urea compound is a diurea compound formed by the reaction of a diisocyanate component and a monoamine component together, and the monoamine component contains aliphatic monoamine. [6] The rolling bearing arrangement according to claim 1, wherein the base oil and the lubricating oil are each selected from the group consisting of synthetic hydrocarbon oil, ester oil and a mixture of the hydrocarbon oil and the ester oil, The kinematic viscosity at 40 °C of both the base oil and the lubricating oil is 10 to 50 mm2 / s, the fat composition contains more than 10 wt.% and 14 wt.% or less of the thickener, based on the total amount of the base oil and the thickener, and The working penetration of the fat composition, measured according to JIS K 2220, is 250 to 280. [7] Rolling bearing arrangement according to claim 1, wherein the lubricating oil supply device is configured to deliver the lubricating oil in the direction of a surrounding area of ​​a raceway surface of the inner ring.

Images