JP2003314560A - Rolling equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the high performance of abrasion resistance without peeling of DLC layer even if high contact stress is given in a roller bearing that the DLC layer is formed on the plane of an orbit, etc. <P>SOLUTION: An under layer 6 consisting of chrome thin film, a intermediate layer 7 consisting of 'chrome + carbon' thin film and a DLC layer 8 containing argon are formed to this order on the face of a member 5 of SUJ2 (in other words, whole outer circumference face 10 of an inner ring 1, whole inner circumference face 20 of an outer ring 2 and whole surface of a ball 3). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rolling devices such as rolling bearings, ball screws, and linear guides.

[0002]

2. Description of the Related Art Diamond-like carbon (hereinafter referred to as "D
LC "is abbreviated. ) The film has a surface hardness that is similar to that of diamond (plastic deformation hardness of 10 GPa or more),
Regarding the sliding resistance, the coefficient of friction is 0.2 or less, which is as small as that of molybdenum disulfide or fluororesin. for that reason,
The DLC film has attracted attention as a new wear resistant film formed on the raceway surface of a rolling device.

The formation of a DLC film on the raceway surface of a bearing ring of a rolling bearing or the raceway surface of a rolling element is disclosed, for example, in Japanese Patent Laid-Open No. 9-96952.
-144764, JP 2000-136828, JP 2000-205277, and JP 200
0-205279, JP 2000-205280.
It is described in Japanese Patent Publication No.

[0004]

The DLC film formed on the raceway surface or the like of the rolling bearing has a problem that it is easily separated from the raceway surface or the like due to high contact stress. International publication WO
In order to solve this problem, a metal layer, a transition zone (alternate layer of a metal carbide layer and a metal layer), on a raceway surface made of bearing steel, has been disclosed in 99/14512 (Japanese Patent Publication No. 2001-516857). It is described that a metal mixed DLC layer is provided in this order. However, this method has room for further improvement.

According to the present invention, in a rolling device in which a DLC layer is formed on the raceway surface of a raceway groove and / or the rolling surface of a rolling element, the DLC layer is not separated even when a high contact stress is applied, It is an object to obtain high wear resistance.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an inner member and an outer member that are arranged relatively inside and between a raceway groove of both members. A plurality of rolling elements arranged so as to be freely rollable, wherein one of the inner member and the outer member relatively moves with respect to the other when the rolling elements roll, Chromium (Cr), tungsten (W), titanium (Ti), on the raceway groove formed of the steel material of the inner member and / or the outer member, or on the rolling surface formed of the steel material of the rolling element, Silicon (Si), Nickel (N
i) and an underlayer having a composition containing at least one element of iron (Fe), a constituent element of the underlayer and carbon (C), and the carbon content is lower on the side opposite to the underlayer. An intermediate layer larger than the formation layer side, an additive component containing at least one of hydrogen (H), argon (Ar), and nitrogen (N), and a DLC layer containing carbon are formed in this order. And a layer having a three-layer structure including a DLC layer on the surface thereof.

When the additive component of the DLC layer is hydrogen, its content is preferably 0.1% by mass or more and 15% by mass or less. When the additive component is argon, its content is preferably 0.02 mass% or more and 5 mass% or less. The underlayer is a film made of an element having a lattice constant similar to iron, and has excellent adhesiveness to a raceway groove or a rolling surface formed of a steel material. By forming the DLC layer having the above structure on this underlayer via the intermediate layer having the above structure, peeling of the DLC layer is prevented even when high contact stress is applied. That is, by providing the underlayer, the intermediate layer thereon, and the layer having the three-layer structure in which the DLC layer is further formed thereon (the layer including the DLC layer on the surface) in the raceway groove or the rolling surface, Even if a contact stress is applied, peeling of the DLC layer is prevented.

The underlayer has a thickness of, for example, 40 nm to 50 nm.
0 nm, the thickness of the intermediate layer is, for example, 40 nm to 500 n
m, and the thickness of the DLC layer is, for example, 0.22 μm to 4.0.
μm, the total thickness of the three layers is, for example, 0.3 μm to 5.0 μm
And The total thickness of the three layers is preferably 0.8 μm to 2.0 μm. Since the DLC layer contains the additive component in addition to carbon, the equivalent elastic constant becomes equal to or less than that of the steel material. Therefore, even if repetitive stress is applied, a raceway groove or rolling surface formed of the steel material. It becomes difficult to peel from. The equivalent elastic constant of this DLC layer is 80 GPa or more 2
It is preferably 40 GPa or less. When it is less than 80 GPa, the surface hardness of the DLC layer becomes low, and the wear resistance decreases. When it exceeds 240 GPa, it has a higher equivalent elastic constant than that of the steel material, and thus it is easily peeled from the raceway groove or the rolling surface formed of the steel material by the repeated application of stress.

Here, the DLC film has an amorphous structure in which SP3 bonds having a diamond structure and SP2 bonds having a graphite structure are mixed, the SP3 bond imparts hardness, and the SP2 bond has slidability (lubricity). Is given. Therefore, the properties of the DLC film change depending on the ratio of SP3 bond and SP2 bond. That is, the DLC film having many SP3 bonds tends to be hard but have low slidability, and the DLC film having many SP2 bonds tends to have high slidability but low film strength. In the present invention, D containing the above-mentioned additional components in a predetermined range other than carbon
By forming the LC layer, SP3 coupling and SP of the DLC layer
Good balance of 2 couplings and suitable sliding property and strength for rolling device.

The DLC layer can be formed by a film forming method capable of supplying hydrogen, argon, or nitrogen in a gaseous state, such as a plasma CVD method or a sputtering method. In particular, the unbalanced magnetron is used. It is preferably formed by a sputtering (hereinafter abbreviated as “UBMS”) method. The UBMS method uses a magnetron cathode with a non-equilibrium magnetic field distribution,
Since the plasma density in the vicinity of the substrate (deposition surface) can be increased as compared with the ordinary magnetron sputtering method (balanced magnetron sputtering method), the substrate temperature during film formation can be lowered. Also,
There is also an advantage that a hard DLC layer can be formed by bias sputtering performed by applying negative power to the substrate.
In particular, the bias sputtering by the UBMS method is a particularly preferable film forming method because the composition of the DLC layer can be easily controlled by controlling the target power and the bias voltage and the gas introduction amount.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. As an embodiment of the rolling device of the present invention, the rolling bearing shown in FIG. 1 was manufactured. This rolling bearing has an inner diameter of 3
It is a deep ball bearing having a diameter of 0 mm and an outer diameter of 62 mm, and includes an inner ring (inner member) 1, an outer ring (outer member) 2, balls (rolling elements) 3, and a cage 4. Inner ring 1, outer ring 2, and ball 3 are S
UJ2 (high carbon chrome bearing steel type 2), the entire outer peripheral surface 10 including the raceway groove 11 of the inner ring 1, the raceway groove 21 of the outer ring 2
A thin film was formed on the entire inner peripheral surface 20 including and the entire surface of the ball 3 by the following method. As the cage 4, a corrugated cage made of low carbon steel was used.

As a film forming apparatus, U of Kobe Steel Ltd. is used.
A BMS device “504” was used. Chromium and carbon (targets) were set as the targets at predetermined positions of this device. First, the inner ring 1, the outer ring 2, and the balls 3 that are the objects to be film-formed.
Was washed with a solvent to remove oil, and then dried. Next, these were placed on a turntable of a film forming apparatus, and a process (bombard process) of cleaning and activating the surface of the film forming object by sputtering was performed. In this bombarding process, the pressure in the chamber is set to about 10 ^-2 Pa with the target power being 0, argon gas is introduced into the chamber, negative power is applied to the film formation target, and sputtering is performed with argon plasma for 15 minutes. It was done by doing.

Next, the target power of chromium is set to "-", a negative bias voltage (-50V to -100V) larger than this is applied to the film-forming target, and argon gas is introduced into the chamber. UBMS was performed. As a result, a chromium thin film having a thickness of 0.2 μm is formed as a base layer on the entire outer peripheral surface 10 including the raceway groove 11 of the inner ring 1, the entire inner peripheral surface 20 including the raceway groove 21 of the outer ring 2, and the entire surface of the ball 3. Formed.

Next, while gradually decreasing the chromium target power and gradually increasing the carbon target power, argon gas was introduced into the chamber, and the UBMS was applied while the bias voltage of the film-forming target remained unchanged. went. Thereby, the outer peripheral surface 1 including the raceway groove 11 of the inner ring 1
0, the entire inner peripheral surface 20 including the raceway groove 21 of the outer ring 2, and the underlayer (chrome thin film) on the entire surface of the ball 3,
As the intermediate layer, a thin film made of chromium and carbon and having a gradually increasing carbon content was formed with a thickness of 0.3 μm. The target power of chromium and carbon was controlled so that the target power of chromium became 0 when the thickness of the intermediate layer reached 0.3 μm.

Next, a carbon target power was applied, and with the chromium target power being 0, a film was formed while continuing to introduce argon gas into the chamber. As a result, the entire outer peripheral surface 10 including the raceway groove 11 of the inner ring 1, the entire inner peripheral surface 20 including the raceway groove 21 of the outer ring 2, and each intermediate layer (“chrome + carbon” thin film) on the entire surface of the ball 3 are formed. At this time, a DLC layer containing argon was formed in a thickness of 2 μm.

As a result, as shown in FIG. 2, the surface of the member 5 made of SUJ2 (that is, the entire outer peripheral surface 10 of the inner ring 1, the entire inner peripheral surface 20 of the outer ring 2, and the entire surface of the ball 3).
A base layer 6 made of a chromium thin film, an intermediate layer 7 made of a "chrome + carbon" thin film containing argon, and a DLC layer 8 containing argon were formed in this order. here,
By changing the argon supply amount at the time of forming the DLC layer 8,
The inner ring 1, the outer ring 2, and the balls 3 having various values of the argon content of the LC layer 8 were produced. Then, the inner ring 1, the outer ring 2, and the balls 3 having the same argon content in the DLC layer 8 are combined to assemble a rolling bearing, and an axial load: 60
It was rotated under the conditions of 0 N, rotation speed: 8000 rpm, lubricant: spindle oil (3 microliter application), and the time until seizure occurred was examined. The argon content in the DLC layer was measured by fluorescent X-ray analysis.

The seizure time and D obtained from the results
A graph showing the relationship with the argon content in the LC layer is shown in FIG.
Shown in. As can be seen from this graph, when the argon content in the DLC layer is 0.02% by mass or more, the burn-in time is 12 hours or more, and when the argon content in the DLC layer is 1.0% by mass or more, the burn-in occurs. The time is over 20 hours.

Since the burn-in time is about 3 hours in the DLC layer containing no argon, the content of argon in the DLC layer is set to 0.02% by mass or more, which is four times or more that in the case of the DLC layer containing no argon. Seizure resistance can be obtained. If the content of argon in the DLC layer exceeds 5.0% by mass, the crystal structure of carbon forming the DLC layer becomes sparse and wear resistance decreases.

Therefore, according to the rolling bearing of this embodiment, the underlayer 6 made of a chromium thin film is formed on the entire surface of the raceway groove 11 of the inner ring 1 formed of SUJ2, the raceway groove 21 of the outer ring 2 and the ball 3, Intermediate layer 7 consisting of a "chromium + carbon" thin film containing argon, D containing argon
The LC layer 8 is formed in this order, and by setting the argon content in the DLC layer 8 to 0.02 mass% or more and 5.0 mass% or less, a very small amount of lubricant can be used or no lubricant can be used at all. Even in this case, high wear resistance can be obtained.

In the above embodiment, the DL formed on the outermost surface
Although the C layer contains argon as an additive component other than carbon, the additive component may be hydrogen or nitrogen. Below, DLC containing hydrogen as the additional component
The relationship between the hydrogen content of the DLC layer and the wear resistance of the surface when the layer is formed on the outermost surface will be described. A ball-on-disk test was conducted to investigate this relationship. First,
As a test piece for this test, a disc (disc) test piece (diameter: 62 mm, thickness: 7 mm, surface roughness: 0.004 Ra) 91 made of SUJ2 was prepared. Also, the diameter is 8
A ball 92 made of SUJ2 having a size of mm was prepared.

As shown in FIG. 4, a disk-shaped test piece 9
In No. 1, a layer 93 having a three-layer structure including a DLC layer was formed on the surface. This layer 93 is composed of a base layer made of a chromium thin film, an intermediate layer made of a "chrome + carbon" thin film, and a DLC layer containing hydrogen in this order from the test piece 91 side. The layer 93 was formed by the same method as the above-described film forming method until the formation of the underlayer and the intermediate layer, and the formation of the DLC layer containing hydrogen was performed by introducing methane gas into the chamber. By changing the introduction amount of this methane gas, the DLC layers having different hydrogen contents are formed into a layer 93 having a three-layer structure.
Each test piece 91 having the outermost surface was obtained.

Using each of the obtained test pieces 91, the sliding speed:
A ball-on-disk test was performed under the conditions of 2.5 m / s, surface pressure: 2.5 GPa, lubrication: non-lubrication, and a sliding resistance value (friction coefficient) was measured using a load cell. The hydrogen content in the DLC layer was measured by glow discharge emission spectrometry. FIG. 5 is a graph showing the relationship between the coefficient of friction and the hydrogen content in the DLC layer, which was obtained from the results. As can be seen from this graph, when the hydrogen content in the DLC layer is 0.1% by mass or more, the friction coefficient is 0.15 or less. The DLC layer containing no hydrogen has a friction coefficient of 0.30, so the hydrogen content in the DLC layer is 0.1
By setting the content by mass% or more, the friction coefficient can be reduced to 1/2 or less of that in the case of the DLC layer containing no hydrogen. That is, by forming the DLC layer containing 0.1 mass% or more of hydrogen on the outermost surface, better wear resistance can be obtained than when the DLC layer containing no hydrogen is formed on the outermost surface.

The present invention can also be applied to rolling devices other than rolling bearings (for example, ball screws and linear guides). In a ball screw, the screw shaft is the inner member and the nut is the outer member. In the linear guide, one of the guide rail and the slider is an inner member and the other is an outer member.

[0024]

As described above, according to the present invention,
DLC on raceway surface of raceway groove and / or rolling surface of rolling element
In the rolling device in which the layer is formed, even if a high contact stress is applied, the DLC layer does not peel off and high wear resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a rolling bearing corresponding to an embodiment of a rolling device of the present invention.

FIG. 2 is a cross-sectional view showing a layer structure formed by the present invention.

FIG. 3 is a graph showing the relationship between the burn-in time and the argon content in the DLC layer, obtained from the test results of the embodiment.

FIG. 4 is a view showing a test piece of a ball-on-disk test.

FIG. 5 is a graph showing the relationship between the coefficient of friction and the hydrogen content in the DLC layer, obtained from the test results of the embodiment.

[Explanation of symbols]

1 inner ring 11 Inner ring raceway groove 10 Outer surface of inner ring 2 outer ring 21 outer raceway groove 20 Inner peripheral surface of outer ring 3 balls (rolling elements) 4 cage Member made of 5 SUJ2 6 Underlayer 7 Middle class 8 DLC layer 91 Disc-shaped test piece 92 balls 93 Layer having a three-layer structure including a DLC layer on the surface

Claims (3)

[Claims] 1. An inner member relatively arranged on the inner side and an outer member arranged on the outer side, and a plurality of rolling elements rotatably arranged between raceway grooves of the both members. A rolling device comprising at least one of an inner member and an outer member that moves relative to the other by rolling of a rolling element, wherein the inner member and / or the outer member is made of a steel material. Chromium (Cr), tungsten (W), titanium (T) in the raceway groove or on the rolling surface made of steel material of the rolling element
i), silicon (Si), nickel (Ni), and iron (F
e) an underlayer having a composition containing at least one element, an intermediate layer containing a constituent element of the underlayer and carbon (C), and having a carbon content on the side opposite to the underlayer and higher than that on the underlayer side. A diamond layer on the surface of which a layer and a diamond-like carbon layer containing carbon and an additive component containing at least one of hydrogen (H), argon (Ar) and nitrogen (N) are formed in this order A rolling device having a three-layer structure including a like carbon layer. 2. The rolling device according to claim 1, wherein the additive component contained in the diamond-like carbon layer is hydrogen, and the content ratio thereof is 0.1% by mass or more and 15% by mass or less. 3. The additive component contained in the diamond-like carbon layer is argon, and its content is 0.0
The rolling device according to claim 1, which is 2% by mass or more and 5% by mass or less.