JPH11182556A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the lubricity while suppressing remarkable change in dimension of a rolling bearing, and to improve the wear resistance and seizure resistance. SOLUTION: A nitrosulfurized layer is formed on at lest either surface of a bearing component. The nitroscelfurized layer is obtained through the gas nitrosulfurizing treatment, and because the sulfur composition excellent in lubrication is contained in the layer, the friction resistance is reduced, and the coagulation phenomenon can be prevented while suppressing the temperature rise by the friction heat even in a condition where the lubricating oil is difficult to feed. In addition, the gas nitrosulfurizing treatment can be achieved at a lower temperature and in a shorter time compared with the conventional tufftride treatment and the thermosetting treatment, and the thermal strain of a base metal is difficult to generate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rolling bearing. In addition, this rolling bearing is, for example, around a crank journal of a two-cycle engine and a kerosene engine,
Examples include those used in applications where lubrication conditions are severe, such as for ships, around the cylinder head of a 4-cycle engine.

[0002]

2. Description of the Related Art In a rolling bearing used in an environment as described above, for example, inner and outer rings and rolling elements are made of, for example, SUJ based on JIS standard, and these are subjected to a thermosetting treatment. As the thermosetting treatment, usually from 900 to 930 ° C,
The quenching is performed by lowering the temperature to an appropriate temperature, and the tempering is usually performed at 160 to 180 ° C. in consideration of the ambient temperature in the use environment.

When the retainer is made of a metallic retainer such as a press-formed corrugated retainer or an extruded retainer, the surface of the retainer is coated with a salt called a so-called tuftride treatment. Surface treatment including soft nitriding such as bath nitriding and gas soft nitriding may be performed.

[0004]

Even if such a heat curing treatment or a tuftride treatment is performed, in an environment where lubrication conditions are quite severe, an oil film is liable to be cut off, so that the wear resistance and the seizure resistance are unsatisfactory. There is room for improvement, such as remaining.

Moreover, in the above-mentioned conventional heat-curing treatment, since the metal structure is transformed from martensite to austenite and the temperature change during the treatment is large, the distortion of the base material is increased and the dimensional change is likely to be large. Therefore, the polishing cost and the super-finishing process must be performed after the heat treatment, resulting in an increase in manufacturing cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rolling bearing capable of improving lubricity while suppressing remarkable dimensional change, thereby improving wear resistance and seizure resistance.

[0007]

According to a first aspect of the present invention, at least one of the bearing components is formed of a metal material, and a sulfided nitrided layer is formed on a surface portion thereof.

In a rolling bearing according to a second aspect of the present invention, at least a cage of the bearing components is formed of a metal material, and a sulfided nitrided layer is formed on a surface portion thereof.

According to a third aspect of the present invention, there is provided a rolling bearing, wherein the sulfur-nitrided layer according to the first or second aspect is formed on a sulfur-containing layer formed on the surface side of a member to be formed and a sulfur-depressed layer below the sulfur-containing layer. And a diffusion layer in which nitrogen is diffused below the nitrided compound layer.

[0010] As described above, in the present invention, the nitrosulphurized layer formed on the surface of the bearing component is obtained by gas nitrosulphurization and contains a sulfur component having excellent lubricity. When this oxynitriding layer is formed, the oxide film inevitably existing on the surface of the metal base material is removed and the surface of the metal base material is cleaned before the formation of the layer. The layer is formed in a high quality state. For these reasons, the friction resistance of the oxynitrided layer is reduced, and even in a situation where lubricating oil is difficult to be supplied, the temperature rise due to frictional heat is suppressed and the occurrence of the adhesion phenomenon is suppressed.

In addition, since the above-mentioned gas sulphiditriding treatment is performed at a lower temperature than conventional tufftriding treatment or thermosetting treatment, thermal distortion of the metal base material is less likely to occur. As a result, post-processing such as polishing can be omitted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on each embodiment shown in FIGS.

1 to 3 relate to an embodiment of the present invention. FIG. 1 is a sectional view of an upper half of a rolling bearing, and FIG.
FIG. 3 is a cross-sectional photograph of the oxynitrided layer and a schematic cross-sectional view of the cage alone shown in FIG.

The illustrated rolling bearing 1 includes an inner ring 2, an outer ring 3,
A plurality of spherical rolling elements 4 and a retainer 5 are provided. On the outer peripheral surface of the inner race 2 and the inner peripheral surface of the outer race 3, there are formed raceway grooves (reference numerals omitted) serving as raceways of the rolling elements 4.

In the rolling bearing 1, a oxynitrided layer 6 is formed on the entire surface of at least one of the inner and outer races 2, 3, the rolling element 4 and the cage 5, which are its components. In this embodiment, as shown, it is assumed that the oxynitrided layer 6 is formed on the entire surface of the cage 5.

The inner and outer rings 2 and 3 and the rolling elements 4 are
It is formed of stainless steel such as JIS SUS440C, or a metal material containing an alloy element having a strong affinity for nitrogen (for example, carburized steel such as JIS SCM415 or JIS SACM-based nitrided steel). In addition, inner and outer rings 2, 3,
The rolling elements 4 are mainly composed of silicon nitride (Si ₃ N ₄ ), and as sintering aids, yttria (Y ₂ O ₃ ) and alumina (A
l ₂ O ₃ ), ceramics using aluminum nitride (AlN), titanium oxide (TiO ₂ ), spinel (MgAl ₂ O ₄ ), alumina (Al ₂ O ₃ ), silicon carbide (SiC) ), Zirconia (ZrO ₂ ), aluminum nitride (AlN) or the like.

As shown in FIG. 2, the retainer 5 is a corrugated retainer formed by joining two annular plates in the axial direction. The retainer 5 is, for example, a low carbon steel plate such as SPCC material or a JIS standard S.
It is formed of a metal material such as stainless steel such as US304.

When the oxynitrided layer 6 is formed on the cage 5 as in this embodiment, the oxynitrided layer 6
As shown in, in order toward the interior from the surface side of the metal matrix 60 (5), a relatively hard mainly composed of relatively soft immersion硫層61, Fe _2-3 N mainly composed of FeS It has a hierarchical structure including a dense nitride compound layer 62 and an ultra-hard nitride diffusion layer 63 in which N atoms are diffused into the metal base material 60 (5). The cross-sectional photograph of the oxynitrided layer 6 shown in FIG.
Photographed at 400 times magnification with an electron microscope.

Next, a method for forming the oxynitrided layer 6 for the components of the rolling bearing 1 will be described. Here, the retainer 5 is used as the target product.

First, a finished product holder 5 is prepared. The holder 5 is set in a chamber having an airtight structure, and a required reaction gas is supplied in a vacuum state. As the reaction gas, a mixture of a carburizing gas, a nitriding gas, and a sulfurizing gas, that is, CO ₂ + (NH ₃ + N ₂ ) + H ₂ S is used.

Here, the temperature in the chamber is 480 ° C. to 700 ° C.
For example, at 550 ° C., for 0.5 to 5 hours, for example,
Hold for a minute. Thereafter, cooling is performed by oil cooling or air cooling over a required time.

Thus, first of all, the reaction gas, especially H ₂ S
Removes an impurity factor such as an oxide film inevitably present on the surface of the retainer 5 which is the target product, and exposes a pure surface of the metal base material. Subsequently, N quickly penetrates and diffuses deeply into the metal base material to form the above-mentioned oxynitrided layer 6.

The depth of the oxynitrided layer 6 can be controlled by appropriately setting the processing temperature and the holding time. In the case of a bearing, however, the shear stress applied to the raceway surface from the surface is 0.1%.
Since it acts in the range of up to 0.4 mm, the depth of the oxynitrided layer 6 should be at least the above-mentioned range.

The oxynitrided layer 6 is formed as described above. However, since the processing temperature is lower than that of the conventional tuftride processing or thermosetting processing, the occurrence of thermal distortion of the metal base material is suppressed. become. Incidentally, the surface roughness of the oxynitrided layer 6 is determined by the surface roughness of the target product before it is formed (center line average roughness Ra = 0.7 μm to 1.0 μm, ten-point average roughness Rz = 4). 0.0 μm to 7.0 μm, maximum height Rmax =
(4.5 μm to 7.5 μm). As described above, since the dimensional change due to thermal strain can be suppressed in the process of forming the oxynitrided layer 6, it is not necessary to polish the surface after this processing.

As described above, the oxynitrided layer 6 obtained in the present embodiment
Has a sulfurized layer 61 excellent in lubricity containing a sulfur component on a hard nitrided compound layer 62 which is formed densely and smoothly and is comparable to the case of the conventional thermosetting treatment. From which the frictional resistance decreases,
Even in a situation where lubricating oil is difficult to supply, characteristics such as abrasion resistance and seizure resistance are improved, for example, by suppressing the rise in temperature due to frictional heat and suppressing the occurrence of adhesion phenomenon. Incidentally, the coefficient of friction between the oxynitrided layer 6 of the present embodiment and the nitrided layer obtained by the conventional tuftride treatment is 0.24 and 0.54, respectively, in a non-lubricated state. It is excellent at less than 1/100. In an experiment for examining the friction coefficient, a ball (SUJ2 material) was loaded on a test piece (SPCC material having a sulfided nitride layer 6 on its surface) with a load of 200 gf and a speed of 100 mm using an HRIDON type abrasion tester.
The sample was reciprocated 10 times at a distance of 20 mm / sec, and the dynamic friction coefficient at that time was measured.

It should be noted that the present invention is not limited to only the above embodiment, and various applications and modifications are conceivable.

(1) In the above embodiment, the oxynitrided layer 6
Is formed only on the retainer 5, but the oxynitrided layer 6 is formed with the inner and outer rings 2 and 3, the rolling elements 4, which are bearing components.
What is necessary is just to form it in at least one of the retainers 5, and it is arbitrary as to which combination of the object to form the oxynitrided layer 6 and which is included in the present invention. Further, when the inner and outer rings 2 and 3 are to be used as targets, it is not necessary to form them on the entire surface thereof, and it is sufficient to form them only on at least the raceway surface.

(2) When the cage 5 is formed of a synthetic resin material as a rolling bearing, the oxynitrided layer 6 is attached to at least one of the inner and outer rings 2 and 3 and the rolling elements 4 which are the bearing components. It may be formed.

(3) In the above embodiment, a deep groove ball bearing is taken as an example. However, the present invention is applied to various bearing types such as a cylindrical roller bearing, a tapered roller bearing, a spherical roller bearing, and a needle roller bearing. Can be applied. Similarly, the present invention can be applied to a type in which a race is formed integrally with a rotating shaft, a housing, and the like.

[0030]

According to the first to third aspects of the present invention, by forming a nitrocarburized layer on any of the components of the rolling bearing, the lubricating property can be extremely reduced while suppressing the heat distortion of the base material during the formation process. I try to make it better. This makes it possible to omit post-treatments such as polishing that were conventionally required in forming the oxynitrided layer, so that the production cost can be reduced, the frictional resistance is reduced, and the lubricating oil is reduced. Even in a situation where it is difficult to supply water, characteristics such as wear resistance and seizure resistance can be improved, for example, by suppressing the rise in temperature due to frictional heat and suppressing the occurrence of an adhesion phenomenon.

As described above, according to the present invention, it is possible to provide a rolling bearing which can suppress the production cost at a low cost and has excellent wear resistance and seizure resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view of an upper half of a rolling bearing according to an embodiment of the present invention.

FIG. 2 is a perspective view of the retainer shown in FIG. 1;

FIG. 3 is a cross-sectional photograph of a oxynitrided layer and a schematic cross-sectional view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Sulfur-nitrided layer 61 Sulfur-nitrided layer 62 Sulfur-nitrided layer nitride compound layer 63 Sulfur-nitrided layer nitrided diffusion layer

Continuing on the front page (72) Inventor Haruo Kimura 3-5-8 Minamisenba, Chuo-ku, Osaka Koyo Seiko Co., Ltd.

Claims (3)

[Claims] 1. A rolling bearing, wherein at least one of the bearing components is formed of a metal material, and a oxynitrided layer is formed on a surface portion thereof. 2. A rolling bearing, wherein at least a cage of a bearing component is formed of a metal material, and a oxynitrided layer is formed on a surface portion thereof. 3. The rolling bearing according to claim 1, wherein the sulfur-nitrided layer includes a sulfur-containing layer formed on a surface side of a member to be formed and a nitrided layer formed below the sulfur-containing layer. A rolling bearing comprising a compound layer and a diffusion layer in which nitrogen is diffused below the compound layer.