JP2008151264A - Cage for roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller bearing cage having excellent abrasion resistance applicable to a roller bearing used in a high-speed revolution region and a high PV region. <P>SOLUTION: The cage 5 incorporated in the self-aligning roller bearing 1 is a pressed cage formed by press-molding a steel plate. The surface of the base material is coated with a diamond-like carbon (DLC) layer D having a lubricating property. The DLC layer D is composed of five layers, a carbon layer C composed of carbon, a composite carbon layer FC composed of tungsten and carbon, a first metal layer M1 composed of tungsten, a composite metal layer FM composed of tungsten and chromium and a second metal layer M2 composed of chromium. The five layers are arranged in the order of the carbon layer C, the composite carbon layer FC, the first metal layer M1, the composite metal layer FM and the second metal layer M2 starting from the surface side of the DLC layer D. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steel cage incorporated in a rolling bearing.

  Conventionally, a high-strength brass machined cage that is excellent in strength is often used for a rolling bearing on which a load acts. However, high strength brass has a self-lubricating property, but is expensive. Therefore, a high strength brass machined cage has a problem of high material cost. In addition, since it is processed by milling, the processing cost is high and the material yield is low. Therefore, the high-strength brass machined cage has been limited to special applications. For these reasons, in recent years, many press retainers manufactured from cold rolled steel sheets typified by SPCC materials or hot rolled steel sheets typified by SPHD materials have been used.

  In general, SPCC materials are inferior in sliding property and wear resistance compared to high-strength brass. Therefore, when the lubrication conditions are severe, the contact portion between the rolling element and the cage pocket, the guide surface of the cage and the race wheel Wear may significantly progress at the contact area with the material, and rotation accuracy may be reduced. In the worst case, seizure may occur and damage may occur. For this reason, the cage made of SPCC material or SPHD material is subjected to soft nitriding treatment represented by salt bath nitriding treatment or gas soft nitriding treatment to hold a hard nitride layer made of a compound of iron and nitrogen. Efforts have been made to improve wear resistance by forming on the vessel surface.

  For example, Patent Document 1 discloses a technique for improving wear resistance by applying a soft nitriding treatment to a steel plate press cage to form a nitride layer on the surface. Since the wear resistance of the nitride layer is governed by the structure of the nitride layer, by defining the thickness of the porous layer formed on the surface and the dense layer formed immediately below the porous layer, The effect of the porous layer as an oil reservoir is enhanced, and the wear resistance of the cage is improved.

  On the other hand, as a means for improving the slidability and wear resistance of the material, there is a coating of diamond-like carbon (hereinafter sometimes referred to as DLC). DLC has a hardness similar to that of diamond and has a sliding coefficient as low as 0.2 or less, as well as molybdenum disulfide and fluororesin. . Furthermore, due to its unique surface properties, DLC has attracted attention as a new lubrication material for rolling and sliding members, and has recently been used to impart lubricity to bearings.

For example, Patent Document 2 discloses a rolling bearing including a DLC film containing metal on the raceway surface of a raceway or the surface of a rolling element. In this rolling bearing, the contact stress is relieved by the DLC film.
In addition, a rolling bearing having a DLC film formed on the raceway surface of the raceway and the surface of the rolling element by CVD method, plasma CVD method, ion beam forming method, ionized vapor deposition method, sputtering method using non-equilibrium magnetron, etc. A rolling device is known (see Patent Document 3).
JP 2001-90734 A WO99 / 14512 pamphlet JP 2003-56575 A

  However, the cage described in Patent Document 1 can exhibit stable wear resistance due to the effect of the oil accumulation in the porous layer when the usage conditions of the rolling bearing are normal conditions. Is rotated at a high speed close to the permissible rotational speed, and when used in a high PV region where the sliding speed between the cage and the rolling element is 15 m / s, the outermost porous layer with low strength falls off. However, the wear resistance may be insufficient.

Further, according to the technique described in Patent Document 3, a DLC film having a composite layer composed of two or more metals and carbon is excellent in adhesion and small in brittleness, so that a large contact stress acts. Although it can be used under such conditions and under non-lubricated conditions, further improvement is desired in consideration of use under conditions where a large tangential force acts (for example, under high-speed rotation conditions).
Accordingly, the present invention solves the problems of the conventional rolling bearing retainer as described above, and is applicable to rolling bearings used in high-speed rotation and high PV ranges, and has excellent wear resistance. It is an object to provide a cage.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling bearing cage of claim 1 according to the present invention is a steel rolling bearing cage that holds a plurality of rolling elements freely between an inner ring and an outer ring of a rolling bearing. It is characterized by satisfying three conditions.

Condition 1: A diamond-like carbon layer having lubricity is coated on the surface.
Condition 2: The diamond-like carbon layer includes a carbon layer composed of carbon, a composite carbon layer composed of one kind of metal of silicon, titanium, tungsten, and molybdenum and carbon, and silicon, titanium, tungsten, and molybdenum. It consists of five layers: a first metal layer made of one kind of metal, a composite metal layer made of one kind of silicon, titanium, tungsten, and molybdenum and chromium, and a second metal layer made of chromium. ing.
Condition 3: The five layers are arranged in the order of the carbon layer, the composite carbon layer, the first metal layer, the composite metal layer, and the second metal layer from the surface side of the diamond-like carbon layer.

  In such a rolling bearing cage, the composite carbon layer, the first metal layer, the composite metal layer, and the second metal layer are interposed between a steel base material and the carbon layer. Therefore, the adhesion between the diamond-like carbon layer (hereinafter sometimes referred to as a DLC layer) excellent in lubricity and the steel base material is excellent. Further, the adhesion between the five layers constituting the DLC layer is also excellent.

Further, since the composite metal layer is composed of two kinds of metals (one kind of silicon, titanium, tungsten, and molybdenum and chromium), the metal and carbon are combined to produce metal carbide. Even so, the brittleness of the metal carbide is small. Therefore, the DLC layer is not easily damaged even when repeated stress or shear force is applied.
The rolling bearing retainer according to claim 2 according to the present invention is the rolling bearing retainer according to claim 1, wherein the ratio of carbon in the composite carbon layer is from the first metal layer side to the carbon. It is characterized by gradually increasing toward the layer side. With such a configuration, the adhesion between the DLC layer and the steel base material becomes more excellent.

Furthermore, the rolling bearing cage of claim 3 according to the present invention is the rolling bearing cage of claim 1 or 2, wherein the equivalent elastic constant of the diamond-like carbon layer is 100 GPa or more and 240 GPa or less. It is characterized by that.
With such a configuration, the DLC layer has a smaller equivalent elastic constant than the base steel, so that the DLC layer can be deformed when a repeated stress is applied. As a result, since the DLC layer can follow the deformation of the base material, the DLC layer is hardly damaged.

If the equivalent elastic constant of the DLC layer exceeds 240 GPa, the DLC layer will have a larger equivalent elastic constant than steel, so that the DLC layer will follow the deformation of the base material when repeated stress is applied. This makes it difficult to damage the DLC layer. On the other hand, if it is less than 100 GPa, the hardness of the DLC layer becomes low and wear tends to occur.
For a thin film such as a DLC layer, the elastic constant cannot be measured by a normal method. Therefore, in the present invention, an equivalent elastic constant based on the elastic constant measured by the following method is used. That is, the indentation depth is at least within the thickness of the DLC layer, measurement is performed with a microhardness meter, and the equivalent elastic constant is obtained from the obtained load-unloading curve.

For example, when the thickness of the DLC layer is 2 μm or less, the indentation load is appropriately set between 0.4 to 50 mN and measurement is performed. In the present invention, an equivalent elastic constant measured using a micro hardness tester manufactured by Elionix Co., Ltd. and an indentation load of 50 mN is used.
As another method for measuring the equivalent elastic constant, there is a method using a micro hardness measuring device manufactured by Fischer. In this method, it is desirable not to use a (micro) Vickers hardness tester but to use a micro hardness tester or a nano indentator that can be controlled by capacitance. In addition, the indentation depth needs to be within the thickness of the DLC layer. And an equivalent elastic constant is calculated | required from the elastic deformation amount of the load-unloading curve obtained by the said micro hardness meter or the nano indentator.

  In addition, when the equivalent elastic constant of the surface of the high carbon chromium steel (SUJ2) of HRC60 is calculated | required by said method, it will be 250 GPa and will be a result larger than 210 GPa normally described in the catalog etc. This is because the above method is a measurement in a minute indentation region, and is therefore influenced by the work hardening layer on the surface of SUJ2.

Furthermore, the rolling bearing cage according to claim 4 of the present invention is the rolling bearing cage according to any one of claims 1 to 3, wherein the diamond-like carbon layer uses a non-equilibrium magnetron. It is characterized by being formed by sputtering.
Such a physical film formation method has a large contact because a DLC layer having a suitable equivalent elastic constant and strength is easily obtained as compared with a CVD method, a plasma CVD method, an ion beam forming method, an ionized vapor deposition method and the like. It is suitable for parts constituting a device on which stress acts.

  The cage for a rolling bearing of the present invention is provided with a DLC layer having excellent adhesion and wear resistance and low sliding resistance on its surface, so it has excellent wear resistance, high speed rotation, high PV It can also be applied to rolling bearings used in the region.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a rolling bearing cage according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial longitudinal sectional view showing a configuration of a self-aligning roller bearing in which a press cage, which is an embodiment of a rolling bearing cage according to the present invention, is incorporated, and FIG. It is typical sectional drawing which shows the structure of the DLC layer of the holder | retainer with which a spherical roller bearing is provided.
This self-aligning roller bearing 1 includes an inner ring 2, an outer ring 3, two rows of spherical rollers 4 disposed between the inner ring 2 and the outer ring 3, and an inner ring 2 and an outer ring 3. It is comprised by the holder | retainers 5 and 5 which hold | maintain the some spherical roller 4 so that rolling is possible. On the outer peripheral surface of the inner ring 2, raceway surfaces 2a, 2a of two rows of spherical rollers 4 are formed, and the outer diameter of the inner ring 2 is formed larger at the center than at both ends in the width direction. Further, the inner peripheral surface of the outer ring 3 is a two-row integral spherical raceway surface 3a. Note that a lubricant such as grease or lubricating oil may be disposed in an internal space formed between the inner ring 2 and the outer ring 3.

The cage 5 of the self-aligning roller bearing 1 is a press cage manufactured by press-molding a steel plate, and is a contact portion that contacts the surface of the base material (in particular, the inner ring 2, the outer ring 3, and the spherical roller 4). ) Is coated with a diamond-like carbon (DLC) layer D having lubricity.
As shown in FIG. 2, the DLC layer D includes a carbon layer C made of carbon, and one kind of metal of silicon (Si), titanium (Ti), tungsten (W), and molybdenum (Mo) and carbon. A composite carbon layer FC, a first metal layer M1 made of one of silicon, titanium, tungsten and molybdenum, and a composite metal made of one of silicon, titanium, tungsten and molybdenum and chromium. The layer FM and the second metal layer M2 made of chromium are composed of five layers, and these five layers are the carbon layer C, the composite carbon layer FC, the first metal layer M1, the composite from the surface side of the DLC layer D. The metal layer FM and the second metal layer M2 are arranged in this order.

  Such a DLC layer D has excellent adhesion to the base material, and is excellent without causing damage such as peeling even when the cage 5 is used under severe conditions in which metals directly contact each other. Demonstrate wear resistance. Therefore, it can be used suitably also for the self-aligning roller bearing 1 used in high speed rotation and a high PV area | region. Further, it can be suitably used under conditions where a large contact stress acts or under non-lubricated conditions.

Note that the proportion of carbon in the composite carbon layer FC is preferably gradually increased from the first metal layer M1 side toward the carbon layer C side. The equivalent elastic constant of the DLC layer D is preferably 100 GPa or more and 240 GPa or less.
Here, a method of forming the DLC layer D will be described. The degreased cage 5 is installed in an unbalanced magnetron sputtering apparatus 504 (hereinafter referred to as UBMS apparatus) manufactured by Kobe Steel, Ltd., and bombarded on the surface for 15 minutes using sputtering with argon plasma. did.

  Then, using chromium as a target, a film was formed by sputtering chromium on the surface of the base material to form a second metal layer M2 made of chromium. Next, while continuing the sputtering of chromium, sputtering with a target of one kind of metal of silicon, titanium, tungsten, and molybdenum (hereinafter, described using tungsten as an example) was started. A composite metal layer FM made of tungsten and chromium was formed on the second metal layer M2 by such sputtering. During the sputtering, the sputtering efficiency of tungsten was gradually increased while the sputtering efficiency of chromium was gradually decreased. Then, the sputtering of chromium was terminated, and the first metal layer M1 made of tungsten was formed on the composite metal layer FM only for the sputtering of tungsten.

  Next, while continuing sputtering of tungsten, sputtering of carbon using carbon as a target was started. By such sputtering, a composite carbon layer FC made of metal carbide in which tungsten and carbon were bonded was formed on the first metal layer M1. Furthermore, the sputtering efficiency of carbon was gradually increased while the sputtering efficiency of tungsten was gradually decreased. Then, the sputtering of tungsten was terminated, and the carbon layer C was formed on the composite carbon layer FC only for carbon sputtering (the thickness of the entire DLC layer D was 2.2 μm).

  In the above description, the example in which tungsten is used as the metal constituting the composite metal layer FM, the first metal layer M1, and the composite carbon layer FC is shown, but silicon, titanium, or molybdenum may be used. Of course. Further, it is not necessary to use the same kind of metal for the composite metal layer FM, the first metal layer M1, and the composite carbon layer FC, and another metal may be used for one of these layers. Different metals may be used.

  When film formation is performed by such sputtering, it is possible to form the DLC layer D in which the composition of the layer gradually and gradually changes from the second metal layer M2 toward the carbon layer C. The DLC layer D having such a configuration has very good adhesion between each layer (second metal layer M2, composite metal layer FM, first metal layer M1, composite carbon layer FC, and carbon layer C). At the same time, the adhesion between the carbon layer C having excellent lubricity and the steel as the base material is very excellent.

  The UBMS apparatus can be equipped with a plurality of targets used for sputtering, and can control the sputtering efficiency of each component arbitrarily by independently controlling the sputtering power source of each target. is there. For example, in the process of forming the composite carbon layer FC and the carbon layer C in the above case, the power of the sputtering power source (DC power source) of the carbon target is simultaneously reduced while the power of the sputtering power source (DC power source) of the metal target is reduced. (At this time, a negative bias voltage is applied to the cage 5).

  The equivalent elastic constant of the DLC layer D can be changed by controlling the bias voltage applied to the cage 5 or by controlling the partial pressure of the introduced gas. By controlling the type and partial pressure ratio of the introduced gas (hydrocarbon gas such as argon, hydrogen, methane, etc.), it is possible to freely control the sliding resistance of the surface as well as the equivalent elastic constant of the DLC layer D. Therefore, a desired DLC layer suitable for the purpose can be formed by introducing the gas alone or in combination. Furthermore, the thickness of the DLC layer D and each layer (the second metal layer M2, the composite metal layer FM, the first metal layer M1, the composite carbon layer FC, and the carbon layer C) can be accurately controlled by the sputtering time. .

  Here, the results of analyzing the elements forming the DLC layer D using a glow discharge emission analyzer (GDLS-9950 manufactured by Shimadzu Corporation) are shown in the measurement chart of FIG. The chart of FIG. 3 is a chart of the DLC layer D in which tungsten is used as the metal constituting the composite metal layer FM and the first metal layer M1, and silicon is used as the metal constituting the composite carbon layer FC. The horizontal axis of the chart indicates the depth from the surface, and 0 μm means the surface of the DLC layer. Moreover, the vertical axis | shaft has shown content of each element in the depth position.

  In addition, since the information of the depth direction is obtained by the discharge using argon gas, the curve which shows content of each element is broad in the interface of steel and DLC layer D which are base materials. In addition, since the interface between the steel and the DLC layer D is located near 8000 nm, it can be seen from this chart that the thickness of the DLC layer D is about 8 μm. Therefore, the thickness of the actual DLC layer D is 2.2 μm.

In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, the type of steel constituting the cage is not particularly limited, and the cage may be manufactured using a material other than a cold rolled steel plate or a hot rolled steel plate. Further, the manufacturing method of the cage is not particularly limited, and is not limited to the press cage and may be a machined cage.
In this embodiment, the DLC layer is formed by sputtering using a non-equilibrium magnetron, but a pulsed laser arc deposition method, a plasma CVD method, or the like can also be used. However, sputtering using a non-equilibrium magnetron that can easily control the equivalent elastic constant, plastic deformation hardness, and the like is most preferable.

  Furthermore, in the present embodiment, the cage for the self-aligning roller bearing has been described as an example. However, the type of the rolling bearing is not limited to the self-aligning roller bearing, and the present invention includes various types. It can be applied to rolling bearings. For example, radial rolling bearings such as deep groove ball bearings, angular contact ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and thrust type rolling bearings such as thrust ball bearings and thrust roller bearings It is a bearing.

〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples.
A press cage for a self-aligning roller bearing (nominal number 22211) is manufactured by press forming from a cold rolled steel plate SPCC material, and a DLC layer is formed on the surface of the cage by sputtering using a non-equilibrium magnetron. Filmed.

  Examples 1 to 10 are cages provided with a DLC layer having a five-layer structure as described above. Comparative Example 1 is a cage that is not sputtered and does not have a DLC layer. Comparative Examples 2 and 3 are cages in which a DLC layer having a three-layer structure is formed by sputtering. The DLC layer includes a carbon layer made of carbon (corresponding to the carbon layer C of this embodiment), a composite layer made of chromium and carbon (corresponding to the composite carbon layer FC of this embodiment), and a metal made of chromium. Layer (corresponding to the second metal layer M2 of the present embodiment) and the three layers are arranged in the order of the carbon layer, the composite layer, and the metal layer from the surface side of the DLC layer. . Comparative Example 4 is a cage in which a DLC layer having a single layer structure is formed by sputtering. The DLC layer is a carbon layer made of carbon (corresponding to the carbon layer C of the present embodiment).

Next, the abrasion resistance of the cages of Examples 1 to 10 and Comparative Examples 1 to 4 was evaluated. That is, the cage was incorporated in a self-aligning roller bearing (nominal number 22211), a high-speed rotation test was performed, and the wear situation of the cage after the high-speed rotation test was evaluated by mass change. The conditions for the high-speed rotation test are as follows.
・ Load: 15415N
・ Rotation speed: 6750 min ^-1
-Lubrication conditions: Grease lubrication-Test time: 24 hours Table 1 shows the wear amount of the cage. The wear amount of the cage is shown as a relative value when the wear amount of the cage of Comparative Example 1 is 1.

  In Comparative Examples 2 to 4 in which the DLC layers having the single-layer structure and the three-layer structure were formed, the wear amount was larger than that in Comparative Example 1 having no DLC layer. This is the base material because the DLC layer peels off from the base material immediately after the start of the high-speed rotation test because the adhesive strength between the DLC layer and the base material, or the adhesive strength between the layers constituting the DLC layer is weak. This is because the steel was worn out. On the other hand, Examples 1-10 in which the DLC layer of 5 structures was formed had less abrasion amount than the comparative example 1. In particular, Examples 1 to 7 having an equivalent elastic constant of 100 to 240 GPa had very little wear.

It is a fragmentary longitudinal cross-section which shows the structure of the self-aligning roller bearing incorporating the press retainer which is one Embodiment of the roller bearing retainer which concerns on this invention. It is typical sectional drawing which shows the structure of the DLC layer of the holder | retainer with which the self-aligning roller bearing of FIG. 1 is provided. It is the measurement chart which analyzed the element which forms a DLC layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Self-aligning roller bearing 2 Inner ring 2a Raceway surface 3 Outer ring 3a Spherical raceway surface 4 Spherical roller 5 Cage C Carbon layer D Diamond-like carbon layer FC Composite carbon layer FM Composite metal layer M1 First metal layer M2 Second metal layer

Claims (4)

A rolling bearing cage for a steel rolling bearing, in which a plurality of rolling elements are rotatably held between an inner ring and an outer ring of a rolling bearing, wherein the following three conditions are satisfied: Condition 1: A diamond-like carbon layer having lubricity is coated on the surface.
Condition 2: The diamond-like carbon layer includes a carbon layer composed of carbon, a composite carbon layer composed of one kind of metal of silicon, titanium, tungsten, and molybdenum and carbon, and silicon, titanium, tungsten, and molybdenum. It consists of five layers: a first metal layer made of one kind of metal, a composite metal layer made of one kind of silicon, titanium, tungsten, and molybdenum and chromium, and a second metal layer made of chromium. ing.
Condition 3: The five layers are arranged in the order of the carbon layer, the composite carbon layer, the first metal layer, the composite metal layer, and the second metal layer from the surface side of the diamond-like carbon layer.   The rolling bearing retainer according to claim 1, wherein a ratio of carbon in the composite carbon layer gradually increases from the first metal layer side toward the carbon layer side.   The rolling bearing retainer according to claim 1 or 2, wherein the diamond-like carbon layer has an equivalent elastic constant of 100 GPa to 240 GPa.   The rolling bearing retainer according to any one of claims 1 to 3, wherein the diamond-like carbon layer is formed by sputtering using a non-equilibrium magnetron.

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