JP2014020402A - Rolling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling device capable of solving problems associated with sticking of an abrasive grain, change in shape, waving, etc., and also securely obtaining effects on low torque, burning resistance, suppression of heat generation, etc.SOLUTION: A rolling device comprises an inward member having an orbital plane, an outward member having an orbital plane, a plurality of rolling bodies which are arranged between the inward member orbital plane and outward member orbital plane to freely roll, and each have a rolling plane for the inward member orbital plane and outward member orbital plane, and a holder which holds the rolling bodies in a free rolling state, and is characterized in that the rolling bodies each have a hollow on a surface, the hollow being formed by performing surface roughening after polishing and then performing finish polishing.

Description

  The present invention relates to a rolling device, and in particular, can be used for a linear motion device such as a rolling bearing, a linear guide, or a ball screw.

In general, in rolling devices such as rolling bearings, linear guides, ball screws, etc., a rolling motion is performed between an inner member, an outer member and a rolling element constituting the rolling device.
The raceway surface of the outer member and the rolling surface of the rolling element are 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 quenched and tempered in the case of bearing steel, and the hardness is set to HRC 58 or more and 64 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 a requirement, there is one disclosed in Patent Document 1 as a process for forming irregularities on the surface of a rolling element of the prior art. In this technique, after forming irregularities on the surface by shot peening that projects approximately spherical ceramic particles with an average particle size of 200 μm or less, shot peening that projects approximately spherical rubber particles with an average particle size of 1.5 mm or less onto the raceway surface Is to be applied. By performing shot peening with these rubber particles, it is characterized in that uneven portions are removed.

JP 2008-151235 A

  However, by projecting ceramic particles, particle sticking occurs on the surface, the shape of the rolling element changes, and rubber particles cannot completely remove the convex portions on the surface, and the roughness is small. There were problems such as being able to do it and not being able to reduce the bend anymore. For this reason, there have been problems such as those that have an early bearing life and those that have poor characteristics such as sound and vibration. In the present invention, in order to solve this problem, after rolling the shape of the rolling element, the surface roughness Ra (arithmetic average roughness) is roughened to about 0.2 μm by rough polishing, shot peening, plastic working or the like. The invention is characterized in that the concave portion is left on the surface by polishing as a finishing process of the surface later. As a result, problems such as piercing of abrasive grains, change in shape, and generation of waviness can be solved, and effects such as low torque, seizure resistance, and suppression of heat generation can be reliably obtained. The present invention can be expected to further extend the life and lower the torque by forming a solid lubricant having a small shearing force such as MoS2 on the rolling element by shot machining or sputtering.

  In order to achieve the above object, a rolling device according to the present invention includes an inner member having a raceway surface, an outer member having a raceway surface, and the inner member raceway surface and the outer member raceway surface. In a rolling device comprising a plurality of rolling elements that are movably arranged and have rolling surfaces with respect to the inner member raceway surface and the outer member raceway surface, and a holder that holds the rolling body in a freely rolling manner, A recess is formed on the surface of the rolling element, and the recess is formed by performing surface roughing after polishing and then performing finish polishing. Moreover, it is preferable that a solid lubricant is applied to the rolling elements in which the recesses are formed.

  In the present invention, a rolling device excellent in seizure resistance and wear resistance can be provided.

1 is a cross-sectional view illustrating a schematic configuration of a rolling device according to an embodiment of the present invention using a ball bearing as an example. It is an example of the formation method of the uneven | corrugated | grooved part which concerns on one Embodiment of this invention. It is an example of the formation method of the uneven | corrugated | grooved part which concerns on one Embodiment of this invention. It is a metal micrograph of the surface which concerns on one Embodiment of this invention. It is an example of the formation method which concerns on one Embodiment of this invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  An embodiment 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 ball bearing which is a kind of rolling bearing which is an embodiment of a rolling device according to the present invention. This ball bearing includes an inner member 1 (inner ring) having a raceway surface 1a on the outer peripheral surface, and an outer member 2 (outer ring) having a raceway surface 2a facing the raceway surface 1a of the inner member 1 on the inner peripheral surface. A plurality of rolling elements 3 (balls) arranged so as to be freely rollable between both raceway surfaces 1a and 2a, and a cage 4 holding the rolling elements 3 between the inner member 1 and the outer member 2, It has.

  The material of the inner member 1, the outer member 2, and the rolling element 3 is not particularly limited. For example, it may be made of SUJ2, which is a high carbon chromium bearing steel, and carbonitrided, or made of SUJ2. It may be subjected to sublimation quenching or induction quenching, or may be made of SCM420 being chromium molybdenum steel or SCr420 being chromium steel and subjected to carbonitriding or carburizing treatment. Further, the material of the cage 4 is not particularly limited, and examples thereof include plastic and steel. Furthermore, a lubricant may be enclosed in a space formed between the inner member 1 and the outer member 2.

  In the manufacturing process of the rolling element 3, the rolling element is formed into a certain sphere shape by forging, and after performing heat treatment, a process of smoothing the surface shape and making the shape into a true sphere by polishing is performed. In a normal process, the surface roughness of the rolling element is 0.05 to 0.15 μm at this stage, and the surface roughness is smoothed to 0.003 to 0.010 μm by further polishing. .

  However, in this invention, at this stage, the surface roughness Ra is changed from 0.1 μm to 0.5 μm by surface roughing such as rough polishing, shot peening, plastic processing, etc. By polishing, recesses having a surface roughness Ra of 0.003 μm to 0.04 μm and recesses of several tens of μm in diameter are formed, and those with a depth of 1 μm or more are uniform at intervals of 200 μm or less. Can be arranged. The area ratio is preferably about 3% to 25%, more preferably 15% to 22%.

  In addition, about the said plastic working, an example is shown in FIG. 2, FIG. Unevenness can be formed on the surface by rolling the ball by applying pressure to the uneven surface made of cemented carbide or the like. It is to be noted that various shapes of irregularities can be formed on the surface of the ball by changing the shape of the irregularities of the cemented carbide.

  In addition, by forming a solid lubricant having a small shearing force such as MoS2 on this rolling element by shot machining or sputtering, the solid lubricant that is immediately removed on a normal smooth surface can also be used as an anchor effect of the film. The durability of the low torque can be improved by releasing the solid lubricant in the dimple.

Tables 1 and 2 list the surface roughening method, polishing time, finish roughness, solid lubricant, area ratio, torque ratio, and life ratio of Examples and Comparative Examples. The life test conditions are as follows.
Load: 6223N
Rotational speed: 3000min-1
Lubricating oil: Turbine oil whose ISO viscosity grade is ISOVG68

As shown in Table 1 and Table 2, after roughing by plastic working, the surface having a roughness of 0.15 μm by finishing gave low torque and long life.
Furthermore, it was found that by forming a film of MoS2 that is a solid lubricant by shot processing, the torque is further reduced and the life is extended.

DESCRIPTION OF SYMBOLS 1 Inner member 1a, 2a Raceway surface 2 Outer member 3 Rolling body 4 Cage 5 Uneven surface

Claims (2)

  An inner member having a raceway surface, an outer member having a raceway surface, and the inner member raceway surface and the outer member raceway surface. In a rolling device comprising a plurality of rolling elements having a rolling surface with respect to the side member raceway surface, and a cage that holds the rolling element in a freely rollable manner, a depression is formed on the surface of the rolling element. A rolling device characterized in that it is formed by performing a surface roughing process after a polishing process and then performing a final polishing process. The rolling device according to claim 1, wherein a solid lubricant is applied to the rolling element in which the recess is formed.

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