JP2008267403A - Rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life rolling device hardly causing damage of a raceway surface. <P>SOLUTION: At least one of the raceway surface 1a of the inner ring 1 of a conical rolling bearing and the raceway surface 2a of the outer ring 2 thereof is finished by projecting substantially spherical ceramic particles having an average particle diameter of 200 μm or smaller, surface roughness Ra is set to not less than 0.04 μm nor more than 0.25 μm, and surface residual stress is set to not less than -1400 MPa nor more than -900 MPa. After projecting the ceramic particles, solid carbon dioxide powder may be projected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rolling device such as a rolling bearing, a linear guide device, a ball screw, a linear motion bearing and the like.

Generally, in a rolling device such as a rolling bearing, a rolling motion is performed between an inner member, an outer member, and a rolling element constituting the rolling device, and the inner member, the raceway surface of the outer member, and the rolling member. The rolling surface of the moving body is repeatedly subjected to shear stress under high surface pressure. Therefore, the materials constituting the inner member, the outer member, and the rolling element are required to have properties such as being hard and having a long rolling fatigue life.
Therefore, high carbon chrome bearing steel such as SUJ2 and case-hardened steel such as SCr420, SCM420, and SAE4320H are often used as materials constituting these members. In order to obtain the required properties such as rolling fatigue life, these materials are hardened and tempered if they are bearing steel, and the hardness is set to HRC 58 or more and 64 or less. In case of case-hardened steel, quenching and tempering are performed after carburizing or carbonitriding, and the surface hardness is HRC 58 or more and 64 or less, and the core hardness is HRC 30 or more and 48 or less.

  However, in recent years, there has been a demand for maintenance-free rolling devices and reduction in fuel consumption of automobiles equipped with rolling devices, and the use conditions of the rolling devices have become severe. For this reason, the foreign matter mixed in the lubricant for lubricating the rolling device and the damage and peeling of the raceway surface and the rolling surface due to poor lubrication of the rolling device have become a problem. There is an increasing demand for extending the life of rolling devices.

In response to such demands, Patent Documents 1 to 3 propose methods for extending the life of a rolling device by paying attention to compressive residual stress effective in improving rolling fatigue life.
Patent Document 1 describes a rolling component in which a number of minute depressions that become oil pools are formed on the rolling surface by barrel finishing after shot blasting. And the minimum value of the compressive residual stress in the surface layer part from the surface of this rolling surface to the depth of 100 μm is 90 MPa or more.

Further, in Patent Document 2, by performing shot peening, the maximum compressive residual stress at the outermost surface portion of the raceway surface of the raceway is set to 100 kgf / mm ² or more, and the compressive residual stress at a position 300 μm below the surface is set to 40 kgf. A rolling bearing with a / mm ² or more is described.
Furthermore, Patent Document 3 describes a rolling sliding component in which the maximum compressive residual stress in the surface layer portion is set to 50 to 110 kgf / mm ² and the average wavelength of the surface roughness is set to 25 μm or less by performing shot peening. Has been.
Japanese Patent Laid-Open No. 8-232964 Japanese Patent No. 2949794 Japanese Patent No. 3125434

  However, in the rolling component described in Patent Document 1, the barrel finish is performed after shot blasting to finish the rolling surface. Therefore, due to the barrel finishing property of rotating the workpiece in the basket, the rolling component is a cam follower. There is a risk of being limited to a small diameter such as an outer ring. Therefore, for example, it is difficult to apply to a large-diameter rolling bearing having an inner diameter exceeding 80 mm. In addition, there is a problem that the workpieces collide with each other during barrel finishing, resulting in a dent, which is difficult to apply to the ball bearing race.

  Further, in the rolling bearing described in Patent Document 2, the surface roughness of the raceway surface of the raceway ring is not specified, but in shot peening, a shot material having a large particle size (for example, having an average particle size of 0.72 mm) is used. Since steel balls are often used, the surface roughness after shot peening inevitably increases. Therefore, in order to make the surface roughness of the raceway surface at a level that can be used as a rolling bearing, it is necessary to finish the surface by performing polishing after shot peening. However, in particular, a rolling bearing with a large diameter and a large grinding allowance has a problem that a surface layer to which a compressive stress is applied is removed by the allowance, and is difficult to apply.

Furthermore, in the rolling and sliding component described in Patent Document 3, it is assumed that the mating surface to be slid is a relatively rough surface such as an outer ring of a cam follower, so that the so-called compatibility is improved. In addition, the surface roughness is defined in a wide range. For this reason, when the other surface to be slid is a mirror surface like the raceway of a ball bearing, there is a possibility that the other surface may be damaged, making it difficult to apply.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a rolling device that solves the above-described problems of the prior art and is less likely to damage the raceway surface and has a long life.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling device according to claim 1 of the present invention includes 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 outward of the inner member. And a plurality of rolling elements arranged so as to be able to roll between the two raceway surfaces. At least one of the raceway surfaces has a substantially spherical shape with an average particle size of 200 μm or less. The ceramic grain is projected to finish, the surface roughness Ra is 0.04 μm or more and 0.25 μm or less, and the surface residual stress is −1400 MPa or more and −900 MPa or less.

  Since the surface residual stress of the raceway surface has a suitable value due to the projection of the ceramic particles, the rolling device has a long life. Moreover, since the finishing process is given by projection, the raceway surface is finished very smoothly. Therefore, it is not necessary to finish the surface by performing polishing after finishing by projection. Moreover, even when the sliding counterpart surface is a mirror surface, such as a ball bearing race, there is almost no risk of damage to the counterpart surface. Furthermore, since it is a relatively simple process of projecting fine particles, the shape and size of the inner and outer members to be processed are not limited, and for almost all types of rolling devices. Thus, the present invention can be applied.

  If the average particle size of the ceramic particles is more than 200 μm, the surface roughness of the raceway surface after projecting the ceramic particles becomes excessive, so that the finish of the raceway surface becomes insufficient. Further, when the shape of the ceramic particles is not a spherical shape or a substantially spherical shape which is a smooth curved surface but a shape having corners, the surface roughness of the raceway surface after the ceramic particles are projected may be excessive. Furthermore, if the material of the projection material is soft, such as tin, the projection energy is expended on the deformation of the projection material itself, and the surface residual stress cannot be sufficiently applied to the raceway surface. Must be a good ceramic.

  Furthermore, in order not to impair the functions (for example, life and acoustic performance) required for the rolling device (particularly, a ball bearing that requires high accuracy), the surface roughness Ra of the raceway surface after finishing is performed. Needs to be 0.25 μm or less. However, in order to make it less than 0.04 μm, finishing for a long time is required and it is not efficient. Therefore, the surface roughness Ra of the raceway surface needs to be 0.04 μm or more.

  Further, if the surface residual stress of the raceway surface is −900 MPa or less, that is, if the surface compressive residual stress is 900 MPa or more, the occurrence of cracks on the raceway surface is suppressed, and the rolling device has a long life. However, if the surface residual stress is less than −1400 MPa, that is, if the surface compressive residual stress is more than 1400 MPa, the raceway surface is overpeened, and on the contrary, it becomes a source of cracks and has a short life. There is a fear.

According to a second aspect of the present invention, there is provided the rolling device according to the first aspect, wherein a solid carbon dioxide powder is projected after the ceramic particles are projected.
After the ceramic particles are projected, some ceramic components may remain on the raceway surface, but by projecting solid carbon dioxide powder, the remaining ceramic components may be completely removed from the raceway surface. it can. As a result, the wear on the raceway surface is extremely unlikely to occur, and the acoustic performance is greatly improved, making it suitable for applications that require excellent wear resistance and acoustic performance.

  The present invention can be applied to various rolling devices. For example, a rolling bearing, a ball screw, a linear guide device, a linear motion bearing, and the like. Further, the inner member in the present invention means an inner ring when the rolling device is a rolling bearing, a screw shaft when the ball screw is also used, a guide rail when the linear guide device is used, and a linear motion bearing. Means each axis. The outer member is the outer ring when the rolling device is a rolling bearing, the nut when it is a ball screw, the slider when it is a linear guide device, and the outer cylinder when it is also a linear bearing. Each means.

  The rolling device of the present invention has a long life with little damage to the raceway surface.

DESCRIPTION OF EMBODIMENTS Embodiments of 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 structure of a tapered roller bearing which is an embodiment of a rolling device according to the present invention.
The tapered roller bearing shown in FIG. 1 includes an inner ring 1 (inner member) fitted to a bearing seat 6a at one end of a rotating shaft 6 and an outer ring 2 (outer member) fitted to an outer ring fitting member 8 of a housing 7. ), A plurality of rolling elements (tapered rollers) 3 arranged between the raceway surface 1a of the inner ring 1 and the raceway surface 2a of the outer ring 2, and a plurality of rolling elements 3 between the two wheels 1 and 2. And a retainer 4 to be held in the housing.

  Further, a ring-shaped lid body 10 having a water supply passage 9 is attached to the end face of the outer ring fitting member 8, and the outlet of the water supply passage 9 is sprayed so as to face the large end face 3 a of the tapered roller 3. A device 11 is attached. Furthermore, the radial load is applied to the tapered roller bearing by applying a radial load Fr to the rotary shaft 6 using a radial load loading means (not shown). Further, the axial load is applied to the tapered roller bearing by applying an axial load Fs to the outer ring fitting member 8 using a hydraulic cylinder (not shown).

  At least one of the raceway surfaces 1a and 2a of the tapered roller bearing is finished by projecting substantially spherical ceramic particles (for example, glass beads) having an average particle size of 200 μm or less, and the surface roughness Ra is It is 0.04 μm or more and 0.25 μm or less, and the surface residual stress is −1400 MPa or more and −900 MPa or less. Note that the both raceway surfaces 1a and 2a may be subjected to super finishing before the ceramic particles are projected. Alternatively, solid carbon dioxide powder may be projected after the ceramic particles are projected.

A general-purpose shot peening apparatus can be used for projecting the ceramic particles. The injection pressure is preferably 0.196 to 0.588 MPa, and the injection time is preferably 10 to 20 minutes. Moreover, as for the mass of the inner ring | wheel and outer ring | wheel used for one process, 1-20 kg is respectively preferable.
When projecting solid carbon dioxide powder, a shot peening apparatus as shown in FIG. 2 may be used. That is, the shot peening apparatus includes a solid carbon dioxide supply device that supplies solid carbon dioxide powder, a tank that stores the solid carbon dioxide powder supplied from the solid carbon dioxide supply device, and compressed air. A compressor for supplying, an air dryer for drying compressed air supplied from the compressor, a nozzle for jetting mixed solid carbon dioxide powder and compressed air, and a shot unit for accommodating a workpiece to be projected It is equipped with.

  Compressed air dried by an air dryer is mixed with solid carbon dioxide powder from the tank toward the nozzle, and sprayed onto the workpiece from the nozzle. The injection pressure is preferably 0.196 to 0.588 MPa, and the injection time is preferably 10 to 20 minutes. Moreover, as for the mass of the workpiece | work (inner ring, outer ring) used for one process, 1-20 kg is preferable, respectively. A solid carbon dioxide pellet may be used in place of the solid carbon dioxide powder.

The surface roughness Ra of the raceway surfaces 1a and 2a subjected to these treatments is 0.04 μm or more and 0.25 μm or less. Moreover, the surface residual stress of the raceway surfaces 1a and 2a is -1400 MPa or more and -900 MPa or less.
The tapered roller bearing obtained by assembling the inner ring 1 and the outer ring 2 together with the rolling elements 3 and the cage 4 has a long life because the raceway surfaces 1a and 2a are hardly damaged.

  The material of the inner ring 1, outer ring 2, and rolling element 3 is not particularly limited. For example, SUJ2 made of carbonitriding treatment may be used, or SUJ2 made of quenching or induction hardening. It may be made of SCM420 or SCr420 and subjected to carbonitriding or carburizing. Further, the material of the cage 4 is not particularly limited, and examples thereof include plastic and steel. Further, a lubricant may be enclosed in a space formed between the inner ring 1 and the outer ring 2.

  Furthermore, in the present embodiment, the tapered roller bearing is described as an example of the rolling device, but the type of the rolling bearing is not limited to the tapered roller bearing, and the present invention is applicable to various types of rolling bearings. It can be applied to. For example, radial rolling bearings such as deep groove ball bearings, angular contact ball bearings, self-aligning ball bearings, self-aligning roller bearings, needle roller bearings, and cylindrical roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing. Furthermore, the present invention can be applied not only to rolling bearings but also to various types of various rolling devices. For example, a ball screw, a linear guide device, a linear motion bearing, or the like.

The present invention will be described more specifically with reference to the following examples. Test bearings having different surface residual stresses and surface roughnesses on the inner and outer ring raceways are prepared by changing the projection conditions in the bearing having the same configuration as the tapered roller bearing of FIG. 1 described above. (See Table 1) and its life was evaluated.
That is, in shot peening of ceramic particles, the type (material, shape) and average particle size of the ceramic particles used were variously changed. In the case of glass ceramic particles, the shape is substantially spherical. In the case of silicon carbide (SiC) ceramic particles, the shape is a shape having corners. In addition, tests were performed with and without performing shot peening of solid carbon dioxide powder after shot peening of ceramic particles.

This tapered roller bearing is a bearing having a nominal number HR32017XJ, and has an inner diameter of 85 mm, an outer diameter of 130 mm, and a width of 29 mm. The basic dynamic load rating is 143000N. Further, the inner ring and the outer ring are made of SUJ2 steel, the surface hardness is HRC58-64, and the surface retained austenite amount is 3-10% by volume. This amount of retained austenite is the amount of retained austenite present in the portion from the surface of the raceway surface of the inner ring and outer ring to a depth of 20 μm, and is a measured value by X-ray.
In the present embodiment, the inner ring, the outer ring, and the rolling element are subjected to carbonitriding, but may be subjected to submerged quenching and induction quenching without performing carbonitriding. Further, instead of SUJ2 steel, SCM420 and SCr420 subjected to carburizing treatment or carbonitriding treatment may be used.

Such a test bearing was rotated under the following conditions, and the rotation was stopped when the vibration value reached 5 times the initial value. Using a stereomicroscope, the presence or absence of damage such as peeling or abrasion was confirmed. If the raceway surface was damaged, the life was reached. If there was no damage, the rotation test was continued. The results are shown in Table 1. In addition, the numerical value of the lifetime of Table 1 is shown by the relative value when the lifetime of the comparative example 1 which has not performed the shot peening of the ceramic particle is set to 1.
Radial load: 35750N
Axial load: 15680N
Inner ring rotation speed: 1500rpm
Lubricant: Pure grease lubrication (grease amount 60g)
However, the lubricant contains 0.05 g of stainless steel powder as a foreign matter. The hardness of the stainless steel powder is HRC64, and the particle size is 70 to 140 μm.

As can be seen from Table 1, Examples 1 to 6 had a much longer life than Comparative Example 1, and had a life of 5.7 times or more that of Comparative Example 1. In particular, Examples 1 to 3, which performed shot peening of solid carbon dioxide powder, were less prone to wear and had a longer life.
Comparative Example 2 had a short life because the surface roughness was too large due to the influence of the shape of the ceramic particles. Further, in Comparative Example 3, since the compressive residual stress was excessive due to the large average particle size of the ceramic particles, a minute crack was generated and the life was shortened. Furthermore, Comparative Example 4 had a short life because the compressive residual stress was too small.

It is a longitudinal cross-sectional view which shows the structure of the tapered roller bearing which is one Embodiment of the rolling device which concerns on this invention. It is a figure explaining the shot peening apparatus used when projecting the powder of solid carbon dioxide.

Explanation of symbols

1 inner ring 1a raceway surface 2 outer ring 2a raceway surface 3 rolling element

Claims (2)

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 rolling between the both raceway surfaces In a rolling device comprising a plurality of freely arranged rolling elements,
At least one of the raceway surfaces is finished by projecting substantially spherical ceramic particles having an average particle size of 200 μm or less, the surface roughness Ra is 0.04 μm or more and 0.25 μm or less, and the surface residual stress. Is a rolling device characterized in that -1400 MPa or more and -900 MPa or less.   The rolling device according to claim 1, wherein a solid carbon dioxide powder is projected after the ceramic particles are projected.

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