JP2007327594A - Rolling sliding member and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling sliding member and a rolling device that are suitably usable even under conditions of a large contact stress being applied, or under no lubrication. <P>SOLUTION: A DLC layer D coats the base material of an inner ring 1, an outer ring 2, and balls 3 on the contact face between the inner ring 1, outer ring 2, and balls 3 of a thrust ball bearing. The surface roughness Ra at a part in the base material coated with the DLC layer D is 0.03-0.2 μm. The DLC layer D is composed of five layers of: a carbon layer C composed of carbon; a composite carbon layer FC composed of molybdenum and carbon; a first metal layer M1 composed of molybdenum; a composite metal layer FM composed of molybdenum and chromium; and a second metal layer M2 composed of chromium. The five layers are respectively 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 from the surface side of the DLC layer D. Each equivalent elastic constant of the five layers is 0.8-1.5 times the equivalent elastic constant of the base material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rolling sliding member having excellent lubricity and a rolling device constituted by the rolling sliding member, and can be suitably used particularly under conditions where a large contact stress acts or under no lubrication. The present invention relates to a rolling sliding member and a rolling device.

Diamond-like carbon (hereinafter sometimes referred to as DLC) has a hardness similar to that of diamond, and its sliding resistance is as low as 0.2 or less, like molybdenum disulfide and fluororesin. Therefore, it has been conventionally used as a lubricating material.
For example, in a magnetic disk device, by forming a DLC film of several tens of angstroms on the surface of the magnetic element or the magnetic disk, the lubricity between the magnetic element and the magnetic disk is improved to protect the surface of the magnetic disk. Yes.

On the other hand, DLC has attracted attention as a new lubricating material for rolling and sliding members due to the unique surface properties as described above, and has recently been used to impart lubricity to bearings.
For example, Patent Document 1 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, for example, Patent Documents 2 to 7).

International Publication No. WO99 / 14512 Japanese Patent Laid-Open No. 9-147464 JP 2000-136828 A JP 2000-205277 A JP 2000-205279 A JP 2000-205280 A JP 2003-56575 A

According to the technique described in Patent Document 7, damage to the DLC film due to repeated stress and peeling of the DLC film from the base material are unlikely to occur. Although it can be used under low or unlubricated conditions, further improvement is desired in consideration of use under conditions where a larger contact stress acts.
The following two points can be considered as causes of the above damage.

First, the first point is a problem of embrittlement of the metal intermediate layer interposed in order to improve the adhesion between the steel and the DLC film. That is, since the metal constituting the metal intermediate layer and the carbon constituting the DLC film are combined to produce brittle metal carbide, the metal intermediate layer becomes brittle and the DLC film is easily damaged.
The second problem is that the DLC film has a property of being hardly deformed even when stress is applied. Since DLC is hard and highly elastic, if it is covered with a metal material having a small equivalent elastic constant such as stainless steel or bearing steel, the DLC follows the deformation of the base material due to the difference in the equivalent elastic constant between the two. In some cases, the DLC film may be damaged.

Further, if the adhesion at the interface between the base material and the DLC film is insufficient, the entire DLC film may be peeled off from the base material.
Accordingly, the present invention provides a rolling sliding member that can solve the above-described problems of the prior art and can be suitably used even under conditions in which a large contact stress acts or under no lubrication. Let it be an issue. Another object of the present invention is to provide a rolling device having such a rolling sliding member and having excellent lubricity.

In order to solve the above problems, the present invention has the following configuration. That is, the rolling sliding member of claim 1 according to the present invention is characterized by satisfying the following five conditions in a rolling sliding member in which relative rolling contact or sliding contact occurs with a counterpart member. To do.
Condition 1: On the contact surface with the mating member, a steel base material is coated with a diamond-like carbon layer having lubricity.
Condition 2: A portion of the base material covered with the diamond-like carbon layer has a surface roughness Ra of 0.03 μm or more and 0.2 μm or less.

    Condition 3: The diamond-like carbon layer includes a carbon layer made of carbon, a composite carbon layer made of one kind of metal of silicon, titanium, and molybdenum and carbon, and one kind of metal made of silicon, titanium, and molybdenum. The first metal layer is composed of five layers: a composite metal layer composed of one kind of silicon, titanium, and molybdenum and chromium, and a second metal layer composed of chromium.

Condition 4: 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.
Condition 5: The equivalent elastic constants of the carbon layer, the composite carbon layer, the first metal layer, the composite metal layer, and the second metal layer are all 0.8 times or more the equivalent elastic constant of the base material. 1.5 times or less.

Such a rolling sliding member has excellent adhesion between the diamond-like carbon layer (hereinafter also referred to as a DLC layer) excellent in lubricity and steel as a base material. Further, the adhesion between the five layers constituting the DLC layer is also excellent.
Further, since the equivalent elastic constant of the five layers is 0.8 to 1.5 times the equivalent elastic constant of the base material, and the DLC layer has an equivalent elastic constant close to that of the base material, the repeated stress Even when this occurs, the DLC layer can follow the deformation of the base material, and the DLC layer is not easily damaged. If the equivalent elastic constant of the base material exceeds 1.5 times, the equivalent elastic constant of the DLC layer is too large compared to the base material, so that the DLC layer follows the deformation of the base material when repeated stress is applied. Is difficult, and the DLC layer is easily damaged. On the other hand, if it is less than 0.8 times, the hardness of the DLC layer becomes low and wear tends to occur.

Furthermore, if the surface roughness Ra of the portion of the base material covered with the DLC layer is more than 0.2 μm, the roughness of the contact surface with the mating member increases, which may cause acoustic problems. is there. On the other hand, if it is less than 0.03 μm, the contact area between the base material and the second metal layer becomes small, and there is a possibility that sufficient adhesion between the DLC layer and the base material cannot be secured. The rolling sliding member of the present invention can be used without any problem even under non-lubrication due to the lubricity of the DLC layer, and the surface roughness Ra is not limited at all from the viewpoint of lubricity.
The rolling sliding member according to claim 2 according to the present invention is the rolling sliding member according to claim 1, wherein the ratio of carbon in the composite carbon layer is from the first metal layer side to the carbon layer side. It is characterized by gradually increasing toward. With such a configuration, the adhesion between the DLC layer and the steel base material becomes more excellent.

Furthermore, a rolling sliding member according to a third aspect of the present invention is the rolling sliding member according to the first or second aspect, wherein the diamond-like carbon layer is formed by sputtering using a non-equilibrium magnetron. It is characterized by that.
Such a physical film forming method is easy to obtain a DLC layer having a suitable equivalent elastic constant and strength as compared with CVD method, plasma CVD method, ion beam forming method, ionized vapor deposition method, etc. It is suitable for a part constituting a device such as a device on which large contact stress acts.

  As described above, the rolling sliding member of the present invention includes a lubricating film (DLC layer) that is not easily damaged even when a large contact stress is applied, and thus a device (for example, a rolling bearing or the like) on which a large contact stress acts. It is possible to apply suitably to the member etc. which comprise a rolling device). In addition, since it has excellent lubricity, it can be suitably used even without lubrication. In addition, there is little wear and heat generation, and it is strong against repeated stress and has a long life.

  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 the composite carbon layer, the first metal layer, the composite metal layer, and the second metal layer that are not located on the surface, the equivalent elastic constant of each layer is obtained by interrupting the film formation process and preparing samples in which each layer is located on the surface. Ask for.

For example, when the thickness of the DLC layer is 2 μm, the indentation load is appropriately set between 0.4 and 50 mN for measurement. 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 amount of elastic deformation 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 device of claim 4 according to the present invention has an inner member having a raceway surface on the outer surface and a raceway surface facing the raceway surface of the inner member, and is disposed outside the inner member. In the rolling device comprising: an outer member, and a rolling element that is arranged so as to be freely rollable between the both raceway surfaces, at least one of the inner member, the outer member, and the rolling element. The rolling sliding member according to any one of claims 1 to 3 is used.

With such a configuration, the DLC layer of the rolling sliding member constituting the rolling device is not easily damaged even when a large contact stress is applied. Long life even when used.
Examples of the rolling device of the present invention include a rolling bearing, a linear motion guide bearing (linear guide device), a ball screw, and a linear motion bearing.
The inner member is an inner ring in the case where the rolling device is a rolling bearing, a guide rail in the case of a linear guide bearing, a screw shaft in the case of a ball screw, and a shaft in the case of a linear bearing. Each means. In addition, the outer member is an outer ring when the rolling device is a rolling bearing, a slider when the same is a linear guide bearing, a nut when it is a ball screw, and an outer cylinder when it is also a linear bearing. means.

  The rolling sliding member and the rolling device of the present invention can be suitably used under conditions where a large contact stress acts or under no lubrication.

Embodiments of a rolling sliding member and a rolling device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a configuration of a thrust ball bearing which is an embodiment of a rolling device according to the present invention, and FIG. 2 is a partially enlarged sectional view showing an enlarged portion A of FIG. is there.
The thrust ball bearing of FIG. 1 includes an inner ring 1 having a raceway surface 1a, an outer ring 2 having a raceway surface 2a opposite to the raceway surface 1a, and a plurality of balls arranged so as to roll between both raceway surfaces 1a and 2a. 3 and a cage 4 that holds a plurality of balls 3 equally between the raceway surfaces 1a and 2a in the circumferential direction of the bearing.

The inner ring 1, the outer ring 2, and the ball 3 are made of steel such as SUJ2. The dimensions of the inner ring 1 and the outer ring 2 are an inner diameter of 25 mm, an outer diameter of 52 mm, and a thickness of 18 mm. The cross-sectional shape of the raceway surfaces 1a and 2a is an arc shape having a curvature radius of 54% of the diameter of the ball 3.
The inner ring 1, the outer ring 2 and the ball 3 are in rolling contact or sliding contact with each other, and the raceway surface 1a of the inner ring 1, the raceway surface 2a of the outer ring 2, and the rolling surface 3a of the ball 3 correspond to the contact surfaces. On these contact surfaces, the base material of the inner ring 1, the outer ring 2, and the balls 3 is covered with a diamond-like carbon (DLC) layer D having lubricity. And surface roughness Ra of the part by which DLC layer D is coat | covered among base materials shall be 0.03 micrometer or more and 0.2 micrometer or less.

  Further, as shown in FIG. 2, the DLC layer D includes a carbon layer C made of carbon and a composite carbon layer made of one kind of metal of silicon (Si), titanium (Ti), and molybdenum (Mo) and carbon. FC, a first metal layer M1 made of one kind of silicon, titanium, and molybdenum, a composite metal layer FM made of one kind of metal of silicon, titanium, and molybdenum and chromium, and a first metal layer made of chromium. The two metal layers M2 and the five metal layers are composed 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 from the surface side of the DLC layer D. Arranged in the order of M2.

The equivalent elastic constants 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 are all 0.8 times or more the equivalent elastic constant of the base material. 1.5 times or less.
Here, a method of forming the DLC layer D will be described using the outer ring 2 as an example. First, the surface roughness Ra of the surface of the outer ring 2 that becomes the raceway surface 2a was adjusted by shot blasting. The apparatus used is FD-4LD-501 type manufactured by Fuji Seisakusho, and the projection material is steel beads having a particle size of 20 to 30 μm. The shot conditions are a projection pressure of 0.4 MPa and a projection distance of 150 mm. And surface roughness Ra was adjusted by setting process time suitably. In addition, as long as the surface roughness Ra can be adjusted to 0.03 μm or more and 0.2 μm or less, not only the shot blast processing but also other methods such as barrel processing can be adopted.

Next, the outer ring 2 from which the oil has been degreased is placed in an unbalanced magnetron sputtering apparatus 504 (hereinafter referred to as a UBMS apparatus) manufactured by Kobe Steel Co., Ltd., and by sputtering using argon plasma, Bombarding was performed for 15 minutes on the portion to be the raceway surface 2a.
Then, using chromium as a target, the second metal layer M2 made of chromium was formed by sputtering chromium onto a portion of the surface of the base material that would become the raceway surface 2a. Next, while continuing the sputtering of chromium, sputtering with a target of one kind of metal of silicon, titanium, and molybdenum (hereinafter, described using molybdenum as an example) was started. By such sputtering, a composite metal layer FM made of molybdenum and chromium was formed on the second metal layer M2. During the sputtering, the sputtering efficiency of molybdenum 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 molybdenum was formed on the composite metal layer FM only for the sputtering of molybdenum.

  Next, while continuing the sputtering of molybdenum, sputtering of carbon using carbon as a target was started. By such sputtering, a composite carbon layer FC made of metal carbide in which molybdenum and carbon are bonded was formed on the first metal layer M1. Furthermore, the sputtering efficiency of carbon was gradually increased while the sputtering efficiency of molybdenum was gradually decreased. Then, the sputtering of molybdenum was finished, 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 molybdenum 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 it is needless to say that silicon or titanium may be used. It is. 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 outer ring 2).

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 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, in the present 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.

In the present embodiment, the thrust ball bearing has been described as an example, but the rolling device of the present invention can be applied to various rolling bearings. For example, radial type rolling bearings such as deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust type rolling bearings such as thrust roller bearings .
Further, in the present embodiment, the rolling bearing is exemplified as the rolling device, but the rolling device of the present invention can be applied to various other types of rolling devices. For example, the present invention can be suitably applied to other rolling devices such as a linear motion guide bearing, a ball screw, and a linear motion bearing.

〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples. In the bearing having substantially the same configuration as the thrust ball bearing of FIG. 1, the surface roughness Ra (center line roughness) of the portion of the base material covered with the DLC layer and the equivalent elastic constant of the five layers constituting the DLC layer Various changes were made (see Tables 1 and 2), and the durability (life) was examined by a rotation test.

  The rotation test was interrupted every 24 hours, the DLC layer was observed, and it was confirmed whether peeling occurred in the DLC layer. When peeling did not occur, the rotation test was continued, and when peeling occurred, the life was determined. The rotation test is performed in turbine oil whose ISO viscosity grade is ISO VG68. The conditions for the rotation test are an axial load of 8820 N and a rotation speed of 1500 rpm.

  The results of the rotation test are shown in Tables 1 and 2. In addition, the numerical value of the lifetime of Table 1, 2 is shown by the relative value when the lifetime of the comparative example 1 is set to 1. From the results of Tables 1 and 2, it can be seen that the equivalent elastic constants of the five layers constituting the DLC layer are preferably 0.8 to 1.5 times the equivalent elastic constant of the base material. In addition, in the base material, the surface roughness Ra of the portion covered with the DLC layer is smaller (smooth one) has a longer life, and if the surface roughness Ra is 0.08 μm or less, the life is particularly long. It can be seen (see the graph in FIG. 4).

It is a longitudinal section showing the composition of the thrust ball bearing which is one embodiment of the rolling device concerning the present invention. It is the elements on larger scale which expanded and showed the A section of FIG. It is the measurement chart which analyzed the element which forms a DLC layer. It is a graph which shows the relationship between surface roughness Ra and the lifetime of a bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Raceway surface 2 Outer ring 2a Raceway surface 3 Ball 3a Rolling surface 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 sliding member in which relative rolling contact or sliding contact occurs with a mating member, wherein the following five conditions are satisfied:
Condition 1: On the contact surface with the mating member, a steel base material is coated with a diamond-like carbon layer having lubricity.
Condition 2: A portion of the base material covered with the diamond-like carbon layer has a surface roughness Ra of 0.03 μm or more and 0.2 μm or less.
Condition 3: The diamond-like carbon layer includes a carbon layer made of carbon, a composite carbon layer made of one kind of metal of silicon, titanium, and molybdenum and carbon, and one kind of metal made of silicon, titanium, and molybdenum. The first metal layer is composed of five layers: a composite metal layer composed of one kind of silicon, titanium, and molybdenum and chromium, and a second metal layer composed of chromium.
Condition 4: 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.
Condition 5: The equivalent elastic constants of the carbon layer, the composite carbon layer, the first metal layer, the composite metal layer, and the second metal layer are all 0.8 times or more the equivalent elastic constant of the base material. 1.5 times or less.   The rolling sliding member 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 sliding member according to claim 1 or 2, wherein the diamond-like carbon layer is formed by sputtering using a non-equilibrium magnetron.   An inner member having a raceway surface on the outer surface, an outer member having a raceway surface opposite to the raceway surface of the inner member and arranged on the outer side of the inner member, and freely rollable between the both raceway surfaces A rolling device provided with a rolling element, wherein at least one of the inner member, the outer member, and the rolling element is a rolling device according to any one of claims 1 to 3. A rolling device characterized by being a sliding member.

Images