JP2009250316A - Cage for rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cage for a rolling bearing having necessary mechanical strength and capable of maintaining excellent seize resistance and abrasion resistance for a long period of time even under a severe lubrication condition. <P>SOLUTION: The cage 35 is formed of a sintered porous metallic material having Fe as a main component, contains Cu of 5 to 40 wt.% and has a porosity of 10 to 40%. Lubrication oil is impregnated in pores of the sintered metallic material forming the cage 35 in advance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rolling bearing cage that is not lubricated for a long time depending on the installation location and usage environment, and is operated under conditions where lubrication is likely to be insufficient. For example, a spindle support for a wind power generator It is suitable for rolling bearings used for supporting the rotating shafts of gearboxes and gearboxes, and rolling bearings used for automobiles and construction machinery.

  In recent years, wind power generation has attracted attention as part of an environmentally friendly power generation method, and installation of large-scale wind power generators is increasing mainly in European countries. For example, in a 1.5 MW class wind power generator, the main body is installed in a place with a height of 50 m or more, and therefore, maintenance work for the main shaft support of the blade and the rolling bearing used for the gearbox is extremely dangerous. In addition, since it is operated continuously over a long period of 10 to 20 years, the lubricant (grease / oil) inside the bearing will gradually be depleted, and as a result, it may be operated under the harsh conditions of trace lubrication. It is done. Also, bearings used in automobiles and construction machines do not always follow the recommended greasing cycle, and may be operated under insufficient lubrication conditions.

  Of the bearing parts, a cage that holds rolling elements at a predetermined interval is generally formed of iron (steel), copper alloy, resin, or the like. In particular, a metal cage made of iron / copper alloy (high-strength brass CAC301) or the like is used under use conditions that require high cage strength such as high-speed rotation and vibration. During operation of the rolling bearing, the rolling element revolves on the raceway surface while rotating, and the cage is rotated by being driven by the rolling element or the raceway. At that time, when the lubricant inside the bearing is insufficient and an oil film breakage occurs at the contact portion between the rolling element and the cage pocket, the wear of the cage is rapidly accelerated by the metal contact between the two. The metal powder generated by the wear of the cage is caught in the contact portion between the rolling element and the raceway surface, which causes surface peeling of the rolling element and the raceway surface. Furthermore, in the case of an iron cage, seizure is likely to occur because it is the same metal (toggle) as the bearing steel that is the material of the rolling elements.

As means for improving the wear resistance and seizure resistance of the cage material, for example, a solid lubricant such as MoS ₂ , graphite, or Sn, or a resin such as PTFE (fluorine resin) or PA (polyamide) is coated on the cage surface as a film. It is possible. However, if the oil film breaks due to poor lubrication, the coating may be worn away, so this is not a perfect countermeasure for the long term.

  On the other hand, sliding bearings (sintered oil-impregnated bearings) in which pores of a sintered metal material that is a porous body are impregnated with lubricating oil are widely used. For example, Patent Document 1 below discloses an iron-based sintered oil-impregnated bearing that has improved durability under high-speed rotation.

Patent Document 2 below discloses that the cage of the rolling bearing is formed of a sintered metal material that is a porous body in order to prevent the cage from being damaged in a high-speed and high-temperature environment. Has been.
Japanese Patent No. 3410595 JP 2003-049841 A

In general, since a rolling bearing is operated at a higher speed than a sliding bearing, it is preferable that the cage for holding the rolling elements has sufficient mechanical strength and seizure resistance. However, when the density of the porous sintered metal material is lowered, the mechanical strength becomes smaller than that of the melting material (solid metal material), and the mechanical strength necessary for the cage cannot be satisfied. On the other hand, when an iron-based sintered metal material (sintered metal material containing iron as a main component) is used as the cage material, the strength problem is somewhat mitigated, but the roller formed of bearing steel is used. Since the moving body, the race and the cage are made of the same metal, seizure tends to occur at the contact portion of the cage under severe lubrication conditions.

  In view of the above circumstances, the present invention is a rolling bearing retainer that has necessary mechanical strength and can maintain excellent seizure resistance and wear resistance for a long period even under severe lubrication conditions. It is an issue to provide.

  In order to solve the above problems, the present invention is formed of a porous sintered metal material mainly composed of Fe, contains 5 wt% or more and 40 wt% or less of Cu, and has a porosity of 10 to 40%. There is provided a cage for a rolling bearing characterized by being. Here, the porosity is defined as {(ρt−), where the density of the sintered metal material is ρs, and the density of the metal material having the same component content as the sintered metal material and having no pores (for example, forged material) is ρt. ρs) / ρt} × 100.

  By forming the cage with a sintered metal material that is a porous body, the pores of the sintered metal material can have a function as a lubricant reservoir. That is, a part of the lubricating oil (or lubricating grease) fed into the bearing is drawn by the capillary force and held in the pores of the cage. And if the lubricating oil held in the pores is insufficient in the bearing, the lubricating oil oozes out from the surface opening of the cage (the portion where the pores are opened on the surface) and contacts with the rolling elements or race rings. To be supplied. In addition, since the surface opening is provided in the cage, the retention property of the lubricating oil interposed in the contact portion with the rolling elements and the like is increased, and the formation of the oil film is promoted. Due to these effects, good lubricity of the contact portion between the cage and the rolling elements is maintained over a long period of time.

  In order for the pores of the sintered metal material to have a function as the lubricating oil reservoir as described above, a porosity of 10% or more is necessary. On the other hand, when the porosity exceeds 40%, a problem of material strength occurs. From the viewpoint of ensuring the required material strength while giving the pores a function as a lubricant reservoir, the porosity needs to be 10 to 40%.

  Further, by using a sintered metal material (iron-based sintered metal material) containing Fe as a main component, the mechanical strength required for the cage can be satisfied, and more than 5 wt% and less than 40 wt%. By containing Cu, it is possible to increase the initial conformability of the contact portion with the rolling elements and the bearing rings formed of a steel material such as bearing steel, and to prevent seizure. Moreover, by containing Cu, Cu melts at the time of sintering and fills the internal cavity, and at the same time, it is alloyed with iron at the interface of the iron particles to improve the tensile strength of the sintered metal material. Such an effect can be obtained by setting the Cu content to 5 wt% or more. On the other hand, since the tensile strength of copper itself is lower than that of iron, when the Cu content exceeds 40 wt%, the tensile strength of the sintered metal material is lowered and the wear resistance is also lowered. Therefore, the Cu content needs to be 40 wt% or less.

  In the above configuration, the sintered metal material can contain 3 wt% or less of graphite. Since graphite is alloyed with iron to form steel by sintering, the strength of the cage is increased and at the same time improvement of toughness can be expected. In addition, graphite can be expected to serve as a solid lubricant, and the effect of preventing seizure at the contact portion of the cage is enhanced. On the other hand, since the decarburization of graphite proceeds during sintering, the yield is difficult to be constant, but it is preferable to add the graphite so that the content in the finished cage product is 3 wt% or less.

  Moreover, when high abrasion resistance and corrosion resistance are requested | required by a holder | retainer, it may replace with some or all of iron powder, and may use stainless steel powder as raw material metal powder of a sintered metal material. In this case, the stainless steel powder refers to an iron alloy powder having a chromium content of 12 wt% or more.

  Also, if the lubricating oil is impregnated in advance in the pores of the cage (sintered metal material), the initial conformability is effective.

  Further, in order to improve the wear resistance and seizure resistance of the cage, the pores of the cage (sintered metal material) may be impregnated with a solid lubricant or resin, or the cage (sintered metal material). A resin coating may be applied to the surface.

  According to the present invention, there is provided a cage for a rolling bearing which has necessary mechanical strength and can maintain excellent seizure resistance and wear resistance for a long period even under severe lubrication conditions. Can do.

  FIG. 1 shows an example of a rolling bearing that rotatably supports a main shaft of a blade and a rotating shaft of a speed increaser, particularly a main shaft of a blade in a wind power generator. The main shaft of the blade receives a radial load and a moment load generated by its own weight and rotation in addition to an axial load generated when the blade receives wind. Therefore, a rolling bearing that rotatably supports the spindle is required to have a function capable of supporting a radial load, an axial load, and a moment load. In order to satisfy this function, in this embodiment, self-alignment for supporting the spindle is performed. A roller bearing 31 (double-row self-aligning roller bearing) is used. A single-row or double-row tapered roller bearing, an angular ball bearing, or a deep groove ball bearing may be used for supporting the main shaft.

  A self-aligning roller bearing 31 shown in FIG. 1 includes an inner ring 32 having two rows of raceway surfaces 32c and 32d on an outer diameter surface, an outer ring 33 having a raceway surface 33a on an inner diameter surface, and raceway surfaces 32c and 32d of the inner ring 32. Two rows of spherical rollers 34 interposed between the outer ring 33 and the raceway surface 33a of the outer ring 33, and a pair of cages 35 for holding the rows of spherical rollers 34, respectively. The inner ring 32, the outer ring 33, and the spherical roller 34 are made of bearing steel, and the cage 35 is made of a porous sintered metal material.

  The raceway surfaces 32 c and 32 d of the inner ring 32 and the raceway surface 33 a of the outer ring 33 have a shape along the rolling surface 34 a of the spherical roller 34. Further, an inner collar 32e is provided at the axial center of the outer diameter surface of the inner ring 32, and outer collars 32f are provided at both axial ends.

  Each of the pair of cages 35 is an annular body made of a sintered metal material containing Fe as a main component and containing 5 wt% to 40 wt% of Cu and having a porosity of 10 to 40%. A plurality of pockets are provided for accommodating the spherical rollers 34 and holding them at equal intervals around the circumference. Further, the internal pores of the sintered metal material constituting the cage 34 are impregnated in advance (in the state of the finished bearing) with lubricating oil or lubricating grease.

It is preferable that the material forming the cage 35 as described above has a tensile strength of 150 N / mm ² or more. A sintered metal material using only iron powder as a raw metal powder can only secure a tensile strength of about 100 to 140 N / mm ² , and remains uneasy when used as a material for a cage of a rolling bearing. Moreover, the porosity is also deeply related to the strength of the sintered metal material, but the strength can be greatly improved by adding copper powder as the raw metal powder. That is, since the melting point of copper is 1084 ° C., the sintering temperature is set to 1100 to 1250 ° C., so that the copper powder is melted and solidified with the iron powder to be alloyed to improve the strength of the sintered metal material. In addition, there is an effect of promoting sintering. The tensile strength of the sintered metal material is the highest when the Cu content is around 10 wt%, but the trace of the melted and diffused copper becomes a cavity, so that if the Cu content is too high, the strength decreases. Therefore, the Cu content needs to be 40 wt% or less. On the other hand, since the copper powder as the raw metal powder is higher in cost than the iron powder, the Cu content is preferably 5 to 20 wt%.

  The sintered metal material (test piece No. 1-10) which has the component content and porosity shown in the following Table 1 and the melt | dissolution material (test piece No. 11) of high strength brass CAC301 are produced, and are shown in FIG. Wear resistance and seizure resistance were evaluated using a Sabang type wear tester. Porosity (%) is defined as {(ρt−ρs) //, where ρs is the density of the sintered metal material, and ρt is the density of the metal material (forged material) having the same component content as the sintered metal material and no pores. It is a value calculated by ρt} × 100. The test piece No. 10 is a bronze sintered metal material containing about 10 wt% of Sn. Table 2 below shows the test conditions of the Sabang type wear tester.

  The above test conditions were set so that the wear amount of the test piece assuming the counterpart material (bearing steel SUJ2) assuming the rolling elements of the rolling bearing and the cage can be evaluated under boundary lubrication conditions. That is, the object is to evaluate the wear resistance under lubrication conditions involving metal contact. For the evaluation of wear resistance, the amount of wear was calculated from the short axis length (rotating direction of the mating member) by utilizing the fact that the wear scar (elliptical shape) remaining on the test piece had a constant aspect ratio. Also, when evaluating the seizure resistance with the bearing steel, assuming the worst lubrication condition (oil shortage), the felt pad that supplies the lubricating oil in the Saban-type wear test in FIG. The rolling sliding test was conducted, and as a guide, the time when the friction coefficient exceeded 0.4 was compared. The friction coefficient is a value calculated by measuring the tensile force (friction force) generated by the friction between the counterpart material (SUJ2) and the test piece with a load cell and dividing by the load.

The result of the seizure resistance test carried out under the above conditions is shown in FIG. Compared with the result of high strength brass CAC301 (Cu-Zn alloy: test piece No. 11), which is widely used as a standard cage material for rolling bearings and has excellent seizure resistance with steel materials, seizure resistance of each test piece Were evaluated relative to each other. Each test piece of No. 1-10 which is a sintered metal material is degreased in petroleum benzine, and then lubricated (V
The seizure resistance test was performed in a state where the lubricant was immersed in G2) for 1 hour and impregnated (oil-impregnated) with the lubricating oil.

As shown in FIG. 3, in the iron-based sintered metal material (test pieces No. 1 and 2), the test piece No. 2 having a higher porosity was superior in seizure resistance, but it was in an oil-impregnated state. However, it was inferior to CAC301 (test piece No. 11). Further, even with Fe-Cu sintered metal material (test piece No. 3) to which 2 wt% of copper was added, only seizure resistance almost equivalent to that of CAC301 (test piece No. 11) was obtained, but copper was 5 wt%. Fe-Cu sintered metal material added (test pieces No. 4 to 6)
Then, it was confirmed that the seizure resistance was greatly improved. Furthermore, when test pieces No. 4, 7, and 8 were compared, seizure resistance was greatly improved when the amount of copper added was increased even though the porosity was substantially the same. From this, it can be seen that copper in the sintered metal material has a great effect in improving seizure resistance. In addition, even with the same Fe-5% Cu-based sintered metal material, test piece No. 4 with a porosity of 13% cannot be said to have significantly superior seizure resistance, but the porosity is 19, 40%. As it increased, the seizure resistance tended to be remarkably improved (test pieces No. 5 and 6). Since the test pieces No. 6, 8, and 9 were settled at a friction coefficient of about 0.35 and No. 10 was about 0.3, the test was terminated.

Next, the results of the abrasion resistance test are shown in FIG. Here, the specific wear amount is a value obtained by dividing the wear volume by the product of the load and the friction distance (Nm), and the lower this value, the better the wear resistance. As shown in FIG. 4, each sintered metal material (test pieces No. 1 to 10) is a high-strength brass CAC30 that is a raw material.
It turns out that it is excellent in abrasion resistance compared with 1 (test piece No. 11). This is considered to be due to the fact that the hardness is higher than that of the raw material because sintering is performed at a high temperature and the oil film forming ability is excellent because it is a porous body. In addition, sintered metal material (test piece No.
It can be seen that the sintered metal material added with copper is more excellent in wear resistance than 1, 2).

Next, the result of the tensile strength test is shown in FIG. It is desirable that the cage material has a strength of 150 N / mm ² or more. Brass as a melting material (test piece No. 11) shows high tensile strength, and sintered metal materials as porous bodies generally have low strength. In particular, test pieces No. 1 and No. 2 which are sintered metal materials of pure iron are insufficient in strength to be used as cages, and are similarly bronze-based (Cu-1
Test piece No. 10 which is a 0 wt% Sn) sintered metal material is also insufficient in strength to be used as a material for the cage. On the other hand, the strength of the Fe-Cu-based sintered metal material is greatly increased as compared with the sintered metal material having a single component composition. Test piece No. 4 containing 5wt% copper and low porosity of 13%
Has substantially the same strength as the brass melting material (test piece No. 11). And even if the content rate of copper is the same (5 wt%), intensity | strength is falling as the porosity increases (test piece No. 4-6). Moreover, the test piece No. 5 containing 5 wt% of copper and the test piece No. 7 containing 10 wt% of copper are comparable to the test piece No. 3 containing 2 wt% of copper. Even the porosity shows a high tensile strength, and it can be seen that copper is effective in improving the tensile strength. However, the strength of the test piece No. 8 having a high copper content of 40 wt% is low. Therefore, the amount of copper added is preferably 40 wt% or less.

  From the above three test results, the optimal amount of copper added to the iron-based sintered metal material is 5 to 40 wt%, and the porosity is optimally 10 to 40%.

In addition, when the cage is required to have excellent corrosion resistance and wear resistance, the cage may be formed of a sintered metal material using stainless steel powder instead of iron powder as the raw metal powder. The stainless steel powder in this case refers to an iron-based alloy powder having a chromium content of 12 wt% or more. In addition, the porous sintered metal material absorbs the lubricating oil even during operation and functions as an oil reservoir. By impregnating the lubricating oil in advance, a function excellent in initial familiarity can be expected. Further, as a lubricant to be impregnated, a solid lubricant such as MoS ₂ , graphite, or Sn, or a resin such as PTFE (fluorine resin) or PA (polyamide) may be used. By encapsulating the solid lubricant in the surface opening of the sintered metal material, it is possible to exhibit excellent performance in both wear resistance and seizure resistance.

It is sectional drawing which shows the self-aligning roller bearing which concerns on embodiment of this invention. It is a conceptual diagram of a Saban-type abrasion test. It is a figure which shows the result of a seizure resistance test. It is a figure which shows the result of an abrasion resistance test. It is a figure which shows the result of a tensile strength test.

Explanation of symbols

32 Inner ring 33 Cage 34 Spherical roller 35 Cage

Claims (9)

  Roller bearing retainer formed of a porous sintered metal material mainly composed of Fe, containing 5 wt% to 40 wt% of Cu, and having a porosity of 10 to 40% .   The rolling bearing retainer according to claim 1, comprising 3 wt% or less of graphite.   The cage for a rolling bearing according to claim 1 or 2, wherein a part or all of the Fe component of the sintered metal material is a component of stainless steel blended as a raw metal powder.   The rolling bearing cage according to any one of claims 1 to 3, wherein pores of the sintered metal material are impregnated with lubricating oil.   The rolling bearing cage according to any one of claims 1 to 3, wherein pores of the sintered metal material are impregnated with a solid lubricant or a resin.   The rolling bearing cage according to any one of claims 1 to 3, wherein a resin coating is applied to a surface of the sintered metal material.   A rolling bearing in which the rolling bearing cage according to any one of claims 1 to 6 is incorporated.   A rotating device in which a rotating shaft is rotatably supported by the rolling bearing according to claim 7.   A wind power generator in which a rotating shaft is rotatably supported by the rolling bearing according to claim 7.

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