JP2006275196A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing capable of attaining a high speed, the long service life and maintenance-free, by stably providing superior lubricity even in high speed operation. <P>SOLUTION: A grease reservoir forming part 6 and a clearance forming part 7 are arranged in this rolling bearing having inner-outer races 1 and 2, a cage 4 and a rolling body 3. The grease reservoir forming part 6 is arranged in contact with the outer race 2 being a fixed side bearing ring, by forming a grease reservoir 9 inside. The clearance forming part 7 is a member for forming clearance 14 communicating with the grease reservoir 9 along a peripheral surface on the raceway surface 2a side of the outer race 2, and is arranged in the outer race 2. This clearance forming part 7 has clearance 15 of a degree of not contacting a tip part 7a with the rolling body 3 by extending inside a bearing more than the cage 4. Consistency of the grease inside of the bearing and in the grease reservoir 9 is set to 240 to 290. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rolling bearing such as a cylindrical roller bearing with a grease reservoir used for a machine tool main shaft or the like.

  As a lubrication method for the spindle bearing of a machine tool, there are grease lubrication that can be used without maintenance, and air-oil lubrication in which lubricating oil is mixed with transport air and the oil is injected into the bearing from a nozzle. In recent years, machine tools are required to have higher speeds in order to increase machining efficiency, and air-oil lubrication is often used for lubrication in a high speed range. However, air oil lubrication requires an air oil supply device as ancillary equipment and a structure that injects air oil to the bearing and requires a large amount of air, so there are problems from the viewpoint of cost, energy saving, and resource saving. is there. There is also a problem of deteriorating the working environment due to noise caused by wind noise of air and oil scattering. In order to avoid these problems, speeding up by grease lubrication has recently been required.

  Grease lubrication is performed only with the initial sealed grease that was sealed when the bearing was assembled. However, when this is applied to the machine tool spindle, it is necessary to keep the temperature rise of the bearing due to stirring resistance low, so the amount of initial sealed grease is the enclosed space. The volume is reduced to 10 to 20%. Further, the grease in the bearing is removed on both sides of the raceway surface of the inner diameter of the outer ring by centrifugal force during rotation, so that only a small amount of grease remains on the raceway surface. As a result, when operating in a high-speed rotation range where the dn value exceeds 800,000 (bearing inner diameter mm × rotational speed rpm), it is easy to run out of oil, leading to premature seizure, which makes it difficult to guarantee the grease life. Become.

New proposals have been introduced as a means to extend grease lubrication. For example, there is a proposal (Patent Document 1) aiming at high-speed life by providing a grease reservoir on the outer ring raceway surface portion. In addition, there is a proposal (Patent Document 2) in which a bearing is properly lubricated and lubricated by a grease replenishing device provided outside the spindle.
Japanese Patent Laid-Open No. 11-108068 Japanese Unexamined Patent Publication No. 2000-113998

However, the technologies of the above proposed examples cannot provide satisfactory lubrication performance when operated in a high-speed rotation region such as the use rotation speed equivalent to air oil lubrication, and are not satisfactory in view of maintenance-free.
In order to solve such a problem, the present applicant has proposed one having a grease reservoir forming component and a clearance forming component in which a clearance is formed from the grease reservoir to the vicinity of the raceway surface of the outer ring (Japanese Patent Application No. 2003-424619). However, depending on the grease used, there are cases where the temperature rise due to stirring resistance, oil film forming ability, and lubricity are poor.

  An object of the present invention is to provide a rolling bearing capable of solving the above-described problems, obtaining excellent lubricity, achieving high speed, long life, and maintenance-free.

  The rolling bearing of the present invention is a rolling bearing having a plurality of rolling elements interposed between the inner and outer rings and the raceway surfaces of the inner and outer rings and held by a cage, and does not rotate among the inner ring and the outer ring that are the bearing rings. A grease reservoir forming part that is provided in contact with the stationary side race ring and that forms a grease reservoir therein, and a clearance that is provided in the stationary side race ring and communicates with the grease reservoir is a circumferential surface on the raceway surface side of the stationary side race ring. A gap forming part formed along the gap between the bearing and the grease reservoir. The consistency of the grease is 230-290.

In the rolling bearing of this configuration, grease is filled in a grease reservoir formed by a grease reservoir forming part and a gap formed by a gap forming part at the time of assembling the bearing, and grease for initial lubrication is enclosed inside the bearing. Used. When the bearing is operated, the grease inside the bearing is scattered by centrifugal force, and a part of the grease accumulates in the gap between the tip of the gap forming component and the rolling element. As the grease accumulates in this way, the grease reservoir and the raceway surface of the fixed-side raceway are connected by the grease. Since the base oil in grease permeates and moves due to capillary action, if the base oil is consumed as lubricating oil at the rolling element contact part of the raceway surface of the fixed side raceway, the grease reservoir and the raceway surface of the fixed side raceway are connected. Using grease as a passage, grease base oil is continuously supplied to the rolling element contact portion as lubricating oil. As described above, since the lubricating oil is supplied by utilizing the capillary phenomenon, the consumed base oil is continuously replenished, whereby a good lubricating performance can be obtained even at high speed operation, and the speed can be increased.
Since the tip of the gap forming component extends to the inside of the bearing rather than the cage, the base oil passage made of grease can be brought closer to the rolling element, and the base oil that becomes the lubricating oil can be smoothly supplied. .
Also, since the consistency of grease in the bearing and in the grease reservoir is 240-290, there is no problem of temperature rise during high-speed operation, excellent oil film forming ability, good lubrication performance, and maintenance-free High speed operation and long life of bearings can be achieved. If the consistency of the grease is lower than 240, the grease is hard, which increases the stirring resistance, and causes a large temperature increase at high speed rotation. In addition, the contact surface between the rolling elements in the bearing and the race is insufficient in oil film forming capability and inferior in lubrication performance. If the consistency of the grease exceeds 290, the grease is too soft and the viscosity cannot be maintained in the high speed region, resulting in poor lubricity.

  In the grease, the thickener may be urea, and the base oil may be a mixed oil of poly α-olefin oil and ester oil. Poly α-olefin is abbreviated as PAO. When the grease composition is used in this way, it exhibits good lubricity in a wide temperature range from low temperature to high temperature, can prevent the occurrence of cold noise immediately after starting at low temperature, and is durable at high temperature for a long time The excellent properties can be maintained and the bearing life can be extended.

In the present invention, the rolling bearing may be used for supporting a spindle of a machine tool.
Machine tool spindles are strongly desired to be maintenance-free for high-speed rotation to improve machining efficiency, prevention of bearing heat generation to ensure machining accuracy, and improvement of production seats by shortening operation stoppage time. For this reason, by using the rolling bearing of the present invention, the advantage that it is possible to achieve high speed, long life and maintenance-free by using the encapsulated grease is effectively exhibited.

  The rolling bearing of the present invention is a rolling bearing having a plurality of rolling elements interposed between the inner and outer rings and the raceway surfaces of the inner and outer rings and held by a cage, and does not rotate among the inner ring and the outer ring that are the bearing rings. A grease reservoir forming part that is provided in contact with the stationary side race ring and that forms a grease reservoir therein, and a clearance that is provided in the stationary side race ring and communicates with the grease reservoir is a circumferential surface on the raceway surface side of the stationary side race ring. A gap forming part formed along the gap between the bearing and the grease reservoir. Because the grease has a consistency of 240 to 290, excellent lubricity can be obtained even during high-speed operation while being lubricated with grease. It is possible to achieve a Nsufuri.

  A first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, this rolling bearing has a plurality of rolling elements 3 interposed between raceways 1a and 2a of an inner ring 1, an outer ring 2, and inner and outer rings 1 and 2, and a grease pool forming component 6 and a gap forming component. 7. This rolling bearing is a cylindrical roller bearing, and the rolling element 3 consists of a cylindrical roller. The grease reservoir forming component 6 and the gap forming component 7 are provided on both sides in the axial direction of the bearing. The plurality of rolling elements 3 are held by a cage 4.

  The outer ring 2 serving as a fixed-side raceway is provided with tapered surfaces 2b that change in diameter continuously from both sides of the raceway surface 2a to the middle of both outer ring width surfaces, and further, both ends from the outer diameter end of each tapered surface 2b. Flat inner diameter surfaces 2c extending in the axial direction toward the outer ring width surface are provided.

  The grease reservoir forming component 6 is a ring-shaped component having a grease reservoir 9 formed therein, and is provided in contact with the width surfaces on both sides of the outer ring 2. In this example, the grease reservoir forming component 6 includes an outer ring positioning spacer 10 provided in contact with the width surface of the outer ring 2 and an outward groove-shaped grease reservoir forming component fitted to the inner diameter surface of the outer ring positioning spacer 10. It consists of a main body 11. An internal space sandwiched between the outer ring positioning spacer 10 and the grease reservoir forming component main body 11 is defined as a grease reservoir 9. The outer ring positioning spacer 10 has a step surface 10a on the inner diameter surface opposite to the outer ring 2 on which the side wall portion 11a of the grease reservoir forming component main body 11 abuts. The grease reservoir forming component main body 11 is positioned in the axial direction with respect to the outer ring positioning spacer 10 by bringing the side wall portion 11a into contact with the step surface 10a of the outer ring positioning spacer 10 after the grease is filled in the grease reservoir 9. Is done. A sealing part (not shown) is provided at a contact portion between the grease reservoir forming component main body 11 and the outer ring positioning spacer 10, thereby preventing grease leakage. The two grease reservoir forming components 6 arranged in this way also serve as seals at both ends of the bearing.

  The gap forming component 7 is a ring-shaped part that forms a gap 14 communicating with the grease reservoir 9 along the peripheral surface of the outer ring 2 where the raceway surface 2a is formed. The gap forming component 7 is formed integrally with the grease reservoir forming component main body 11. That is, the grease pool forming component main body 11 extends integrally from the outer diameter end portion of the side wall portion 11b adjacent to the bearing. Specifically, as shown in an enlarged view in FIG. 2, the gap forming component 7 extends to the inner side of the bearing from the cage 4 to the extent that the tip 7 a does not contact the rolling element 3, and the outer ring 2 is flat. A gap 14 (preferably a gap width of 0.2 mm or more) is formed between the inner surface 2 c and a predetermined gap 15 is secured between the tip 7 a and the rolling element 3. As a result, one end of the gap 14 opens to a portion of the outer ring tapered surface 2 b close to the rolling element 3.

  A grease having a consistency of 240 to 290 is used as the grease enclosed in the bearing and in the grease reservoir 9. As a grease having a consistency within this range, there is MP-1 grease manufactured by NTN Corporation, which corresponds to a consistency 243. As the thickener of grease, urea type (particularly aliphatic or aromatic) is suitable. As the base oil of the grease, a mixed oil of a synthetic hydrocarbon oil such as PAO (poly α-olefin) oil and an ester oil is preferable. An ester synthetic oil can be used as the ester oil.

  In this case, the ester-based synthetic oil is one in which a predetermined number or more of ester groups are arranged in a comb shape on one side of the carbon atom sequence constituting the chain molecule of the oil, and all the ester groups are adsorbed on the metal surface. Can be involved. Thereby, the said ester synthetic oil is excellent in the adaptability to a metal surface compared with normal ester synthetic oil, and can form a uniform oil film on a metal surface rapidly.

  In contrast, in pentaerythritol ester represented by the following chemical formula 1 used as a base oil of ordinary grease, an ester group is arranged so as to surround one carbon atom. If one ester group is used when adsorbing to the surface, the other three ester groups cannot participate in the adsorption.

(Wherein R _{1 to} R ₄ are all alkyl groups)

Synthetic hydrocarbon oil, which is one of the above base oil compositions, is poly α-olefin oil, polybutene, olefin copolymer, and has a viscosity (40 ° C.) of 20 to 100 mm ² / s and can be used safely. In order to do this, it is preferable to employ a flash point of 220 ° C. or higher.

  These are structures in which α-olefin is low-polymerized to form an oligomer, and hydrogen is added to the terminal double bond, and examples are shown in the following chemical formula 2. Polybutene is also a kind of poly α-olefin, which can be produced by polymerizing a starting material mainly composed of isobutylene using aluminum chloride as a catalyst. Polybutene may be used as it is or after hydrogenation.

(In the formula, R represents an alkyl group, and n = 1 to 6).
As shown in Chemical Formula 3 below, the ester-based synthetic oil is one in which eight or more ester groups are arranged in a comb-tooth shape on one side of eight or more carbon atoms constituting the oil chain molecule. A copolymer of an ester of a dibasic acid.

(In the formula, R _{1 to} R ₄ are all alkyl groups, and x ≧ 2, y ≧ 2, and x and y represent integers.)
Moreover, the range of the suitable molecular weight of such an ester synthetic oil is 1000 to 3000, and the viscosity is 10 to 245 mm ² / s at 40 ° C., and preferable results are obtained. In addition, when it is used as a grease for enclosing a ball bearing of an automobile pulley, it is preferable to use a flash point of 220 ° C. or higher because of its high safety.

  In the composition of the base oil described above, the synthetic hydrocarbon oil and the predetermined ester synthetic oil are blended at a weight ratio of 0.65 to 0.75: 0.35 to 0.25. The reason is that if the synthetic hydrocarbon oil in the base oil is less than the above range, the desired performance of the grease at low temperatures will be inferior, and if it exceeds the above range, the heat resistance will not be sufficient, which is not preferable. is there.

The urea-based thickener may be a known urea compound as shown in the following chemical formula 4. This is a linear polyurea compound obtained by subjecting an amine and diisocyanate as materials to polyaddition reaction in a base oil to cause precipitation, and the diisocyanate forming R ₂ is 4,4. Examples include '-diphenylmethane diisocyanate and tolylene diisocyanate. In the formula, the amine forming R ₁ and R ₃ may be any combination of alicyclic amines such as toluidine, cyclohexylamine and stearylamine, aromatic amines and aliphatic amines. Particularly good results have been obtained using aliphatic amines.

Wherein R ₁ and R ₃ are monovalent groups composed of amines such as toluidine, cyclohexylamine and stearylamine, and R ₂ is a divalent group composed of diisocyanates such as 4,4′-diphenylmethane diisocyanate and tolylene diisocyanate. Represents.)
The blending ratio of such a urea-based thickener in the grease is preferably 5 to 20% by weight. This is because if the amount is less than 5% by weight, the liquid is poor in viscosity and easily leaks, making it difficult to seal the bearing. On the other hand, if it exceeds 20% by weight, it will solidify to a consistency of 200 or less, and the practicality as a grease for enclosing a bearing will be reduced.

  In addition, if it is a range which does not impair the effect of this invention, antioxidant, a rust preventive agent, an extreme pressure agent, an oil-based agent etc. can be added as needed.

  Here, zinc dithiophosphate (ZnDPT) can be illustrated as a typical extreme pressure agent. ZnDTP reacts with the metal surface to form a strong film, and has the effect of suppressing wear of the race and rolling elements. In addition, since a uniform oil film is formed on the metal surface, when such an extreme pressure agent is used, abnormal noise due to oil film breakage is less likely to occur when used at low temperatures. In order to obtain such a preferable result, the amount of ZnDPT added is preferably 0.1 to 10% by weight.

  The operation of the above configuration will be described. When the bearing is assembled, the grease reservoir 9 and the gap 14 are filled with grease. In addition, grease for initial lubrication is sealed inside the bearing. When the bearing is operated, grease inside the bearing is scattered by centrifugal force, and a part G of the grease accumulates in the gap 15 between the tip 7a of the gap forming part 7 and the rolling element 3 as shown in FIG. As grease accumulates in this way, the grease reservoir 7 and the outer ring raceway surface 2a are connected by the grease. Since the base oil in the grease penetrates and moves due to capillary action, if the base oil is consumed as lubricating oil at the rolling element contact portion of the outer ring raceway surface 2a, the grease reservoir 7, the gaps 14 and 15, and the outer ring raceway surface 2a are connected. Using grease as a passage, the base oil of grease is continuously supplied to the rolling element contact portion as lubricating oil.

Thus, in this rolling bearing, since grease connecting the grease reservoir 7, the gaps 14, 15 and the outer ring raceway surface 2a is used as a passage, the base oil of the grease is continuously replenished to the rolling element contact portion as lubricating oil. Lubricating oil can be reliably supplied even in high-speed operation.
Further, since the tip end portion 7a of the gap forming component 7 extends to the inside of the bearing with respect to the cage 4, the base oil passage made of grease can be brought closer to the rolling element 3, and the base oil serving as the lubricating oil can be replenished. It can be done smoothly.
Further, since the consistency of the grease in the bearing and in the grease reservoir 9 is 240 to 290, the bearing can be operated at high speed and the service life can be extended without maintenance.

  FIG. 3 and Table 1 show the results of tests conducted by the inventor on the relationship between grease consistency and life ratio.

Table 1 shows the consistency and life ratio of each of the grease samples A to D having different compositions. FIG. 3 is a graph showing the relationship between the consistency and the life ratio by preparing a plurality of greases of sample B in Table 1 having different consistency.
According to the test results, grease B had the longest life when the grease composition was different. That is, a grease using fatty urea and aromatic urea as a thickener and using PAO and polyol ester as a base oil has the longest life.
Further, as can be seen from FIG. 3, in the grease B, it can be confirmed that the life ratio becomes high when the consistency of the grease is 240 to 290.

  If the grease consistency is lower than 240, the grease is hard and the agitation resistance becomes large. When used for high-speed operation such as a bearing of a spindle device for machine tools, the temperature rises and the rolling elements in the bearing increase. The oil film forming ability deteriorates at the contact surface between the inner and outer rings and the lubrication performance decreases. When the grease consistency is higher than 290, since the grease is soft, the viscosity cannot be maintained in a high speed range, and the lubricating performance is deteriorated.

  FIG. 4 shows an example of a spindle device for a machine tool using the rolling bearing of the above embodiment. This spindle device for machine tools uses two of the above rolling bearings. The two rolling bearings 23 and 24 rotatably support both ends of the main shaft 21 within the housing 22. The inner ring 1 of each rolling bearing 23, 24 is positioned by an inner ring positioning spacer 26 and an inner ring spacer 27, and is fastened and fixed to the main shaft 21 by an inner ring fixing nut 29. The outer ring 2 is positioned and fixed in the housing 22 by an outer ring positioning spacer 10, an outer ring spacer 30, and outer ring pressing lids 31 and 32. The housing 22 is formed by fitting a housing inner cylinder 22A and a housing outer cylinder 22B, and an oil passage groove 33 for cooling is provided in the fitting portion.

  The spindle 21 is provided with a chuck (not shown) for detachably attaching a tool or a work (not shown) to the front end 21a, and a drive source such as a motor transmits rotation to the rear end 21b. They are connected via a mechanism (not shown). The motor may be built in the housing 22. The spindle device can be applied to various machine tools such as a machining center, a lathe, a milling machine, and a grinding machine.

  According to the spindle device of this configuration, the effects of stable supply of lubricant, high speed, long life, and maintenance-free operation in the rolling bearings 23 and 24 of this embodiment are effectively exhibited.

  FIG. 5 shows another embodiment of the present invention. In this embodiment, the grease reservoir forming component 6 and the gap forming component 7 in the first embodiment shown in FIG. 1 are provided only on one side in the axial direction of the bearing. Here, the inner circumference of the outer ring 2 has a tapered surface 2d that changes in diameter continuously from both sides of the raceway surface 2a, and a gap is formed so as to form a gap 14 along the tapered surface 2d. A part 7 extends inside the bearing. Other configurations are the same as those in the embodiment of FIG.

  In each of the above embodiments, the case where the grease pool forming component 6 and the gap forming component 7 are provided on the outer ring 2 side has been described. However, when the inner ring 1 is a fixed side ring, the grease pool forming component 6 is provided on the inner ring 1. The gap forming component 7 is provided.

It is a fragmentary sectional view of the rolling bearing concerning a 1st embodiment of this invention. It is a partial expanded sectional view of the rolling bearing. It is a graph which shows the test result of the relationship between the consistency of grease, and a life ratio. It is sectional drawing of the spindle apparatus for machine tools using the said rolling bearing. It is a fragmentary sectional view of the rolling bearing concerning other embodiments of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner ring 2 ... Outer ring 1a, 2a ... Raceway surface 3 ... Rolling element 4 ... Cage 6 ... Grease accumulation forming part 7 ... Gap formation part 7a ... Tip part 9 ... Grease accumulation 14, 15 ... Gap

Claims (3)

  In a rolling bearing having an inner ring, an outer ring, and a plurality of rolling elements interposed between the raceway surfaces of the inner and outer rings and held by a cage, the inner ring and the outer ring that are the race rings are in contact with a non-rotating fixed raceway ring. A grease reservoir forming component that is provided and has a grease reservoir therein, and a gap formation that is provided in the stationary bearing ring and that communicates with the grease reservoir along the circumferential surface of the stationary bearing ring on the raceway surface side. The gap forming component has a gap that allows the tip portion to extend inward of the bearing from the cage and not to contact the rolling elements, and the consistency of the grease in the bearing and in the grease reservoir is A rolling bearing having 240 to 290.   2. The rolling bearing according to claim 1, wherein the thickener of the grease is a urea type, and the base oil is a mixed oil of a poly α-olefin oil and an ester oil.   The rolling bearing according to claim 1 or 2, wherein the rolling bearing is used for supporting a main shaft of a machine tool.

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