JP2014009733A - Roller bearing - Google Patents

Abstract

A roller bearing having excellent seizure life and peeling life is provided.
An inner ring having an inner ring raceway surface, an outer ring having an outer ring raceway surface, a roller disposed so as to be able to roll between the both raceway surfaces, and the inner ring and / or the outer ring are selectively formed. A roller bearing comprising: an inner ring raceway surface, the outer ring raceway surface, a rolling surface of the roller, an end surface of the roller, and a flange surface, and at least the rolling surface of the roller and / or Alternatively, the rolling surfaces of the rollers and / or the end surfaces of the rollers are made to collide with the end surfaces of the rollers by impacting abrasive particles composed of abrasive particles on the surface of an elastic body having an average particle size of 45 μm or more. A polishing surface having a surface roughness (Ra) of 0.02 to 0.07 μm and a ratio Rz / Ra of the surface roughness (Ra) to the maximum height (Rz) satisfying Rz / Ra ≦ 3 is provided. Roller bearings characterized by that.
[Selection] Figure 2

Description

  The present invention relates to a roller bearing including an inner ring, an outer ring, a roller disposed between the two rings, and a flange selectively formed on the inner ring and / or the outer ring, and in particular, a roller rolling surface and / or an end surface of the roller. The present invention relates to a roller bearing having a polished surface obtained by colliding particles made of an elastic body and containing abrasive grains.

In sliding members such as inner rings, outer rings, rollers, inner rings or outer rings forming roller bearings, various surface properties represented by surface roughness are important in addition to the dimensional accuracy of rolling sliding parts. Is an element. It is known that the fatigue life of the rolling / sliding device is affected by these surface properties.
For example, in the finish polishing of cylindrical rollers used for cylindrical roller bearings, so-called lapping or superfinishing has been conventionally performed in order to improve surface roughness and dimensional accuracy. As an example of lapping, there is a method disclosed in Patent Document 1.

  However, in lapping or superfinishing, the grindstone is pressed against the surface to be polished of the workpiece, so that it is possible to avoid the abrasive grains falling off the grindstone from being pressed against the surface to be polished. Absent. Abrasive grains that pierce the surface to be polished cannot be easily removed in a subsequent cleaning process or the like, and remain until a final product is obtained. If the use conditions are high load conditions or rolling or sliding at high speed while the abrasive grains are pierced, surface damage or surface wear occurs due to the pierced abrasive grains.

Although the number of abrasive grains remaining on the surface to be polished can be reduced by improving the supply and discharge of the grinding fluid, the grinding fluid filter, and the composition of the grinding wheel, the number of remaining abrasive grains should be smaller. Contributes to the long life of cylindrical roller bearings.
Further, in Patent Document 2, as a method for improving the surface roughness of the processed surface of a workpiece using an existing abrasive or blasting apparatus without using a special abrasive or grinding fluid, It has been proposed to inject an abrasive together with a compressed fluid on a processed surface of a workpiece under conditions that satisfy a specific incident velocity and incident angle relationship.

However, since the surface properties of the sliding member obtained under the above conditions are not defined, it cannot be said to be optimal for extending the life of the bearing.
Patent Document 3 proposes a grinding device for a workpiece surface that can perform grinding or polishing until finishing in a short time even on a complicated surface, and can maintain a good working environment. Since the surface property of the obtained sliding member is not specified, it cannot be said that it is optimal for the long life of the bearing.

Furthermore, in Patent Document 4, in order to obtain a rolling and sliding device having an aesthetic appearance, polishing is performed by causing polishing particles made of an elastic body and containing abrasive grains to collide with an object to be polished. It has been proposed that the surface of the polished article be a finished surface having a glossiness of 20 or more.
However, the glossiness is insufficient as an index for defining the surface properties for improving the seizure life and the peeling life.

JP 2002-086341 A Japanese Patent Laid-Open No. 2005-022015 Japanese Patent Laid-Open No. 11-347945 JP 2009-113189 A

  The present invention has been made by paying attention to the above-mentioned problems, and provides an optimum index of the surface properties of sliding members such as inner rings, outer rings, rollers, inner rings or outer rings forming roller bearings. By specifying, it aims at providing the roller bearing excellent in the seizure life and the peeling life.

  The inventors of the present invention have earnestly studied the index of the surface property of the sliding member for providing a roller bearing with excellent seizure life and peeling life, and it is not sufficient to specify the surface roughness Ra. It was found that reducing the maximum height Rz is effective. In particular, it has been found that satisfying the ratio Rz / Ra ≦ 3 of the surface roughness to the maximum height is effective in improving the seizure life and the peeling life. Furthermore, in roller bearings, it has been found that the convex portions of the rollers are more harmful on the rolling surfaces and end surfaces than the convex portions of the inner ring raceway surface and the outer ring raceway surface.

In order to reduce the convex portions, mirror shot processing is effective. Mirror shot processing is a method of processing a surface by causing a medium containing abrasive grains such as diamond on the surface of an elastic body such as rubber to collide with an object using air pressure, mechanical energy, or the like.
The gist of the present invention is as follows.

(1) An inner ring having an inner ring raceway surface, an outer ring having an outer ring raceway surface, a roller disposed so as to be able to roll between the both raceway surfaces, and a collar selectively formed on the inner ring and / or the outer ring. A roller bearing comprising: the inner ring raceway surface, the outer ring raceway surface, the roller rolling surface, the roller end surface, and the flange surface, and at least the roller rolling surface and / or The roller rolling surface and / or the end surface of the roller are brought into contact with the end surface of the roller by causing abrasive particles containing abrasive particles to collide with the surface of an elastic body having an average particle diameter of 45 μm or more. A polishing surface having a roughness (Ra) of 0.02 to 0.07 μm and a ratio Rz / Ra of the maximum height (Rz) to the surface roughness (Ra) satisfying Rz / Ra ≦ 3 is provided. Roller bearings characterized by that.

(2) The roller bearing according to (1), wherein the polished surface has an area ratio of 75% to 95% of the rolling surface of the roller or the end surface of the roller.
(3) The roller bearing according to (1) or (2), wherein the abrasive grains are made of diamond, alumina, or silicon carbide.

(4) Ra which is the ratio of the surface roughness Ra (parallel) parallel to the rolling direction on the rolling surface and / or end surface of the roller to the surface roughness Ra (vertical) perpendicular to the direction. The roller bearing according to any one of the above (1) to (3), wherein (parallel) / Ra (vertical) is α, 0.8 ≦ α ≦ 1.2 is satisfied.
(5) The roller bearing according to any one of (1) to (4), wherein the inner ring raceway surface is subjected to manganese phosphate treatment.

  ADVANTAGE OF THE INVENTION According to this invention, the roller bearing excellent in the seizure lifetime and the peeling lifetime can be provided. Further, since the mirror shot processing is performed, the abrasive grains adhering at the time of polishing can be removed, and the seizure life can be further improved.

Sectional drawing of a cylindrical roller bearing is shown. The schematic diagram of the mirror surface shot processing method is shown. The method of the lifetime test of an Example is shown. The optical microscope photograph of the grinding | polishing surface of the roller bearing of an Example is shown.

Embodiments of the present invention will be described below with reference to the drawings.
In general, in the case of a cylindrical roller bearing, the roller bearing is composed of an inner ring 11, an inner ring rod 13, an outer ring rod 15, and a cylindrical roller 19, as shown in FIG.
The roller bearing of the present invention includes an outer ring and an inner ring. Of these, the outer ring has an outer ring raceway on the inner peripheral surface, and the inner ring has an inner ring raceway on the outer peripheral surface. In addition, the inner ring and the outer ring are selectively formed with wrinkles, but may not have wrinkles.

In the present invention, among the inner ring and outer ring raceway surfaces, the rolling surfaces and end surfaces of the rollers, and the flange surfaces formed on the inner and outer rings, at least the rolling surfaces of the rollers and / or the end surfaces of the rollers have an average particle diameter of 45 μm or more. The surface property is improved by causing abrasive particles containing abrasive grains to collide with the surface of the elastic body, thereby improving the seizure life and the peeling life.
FIG. 2 shows a polishing method by collision of abrasive particles. As shown in FIG. 2, after the peripheral surface portion of the roller (rolling element) 21 is ground with a grindstone (not shown), abrasive particles 25 having an average particle size of 45 μm or more are projected from the shot blast nozzle 23 onto the peripheral surface portion of the roller 21. And polish.

  In the present invention, among the inner ring and outer ring raceway surfaces, the rolling surfaces and end surfaces of the rollers, and the flange surfaces formed on the inner and outer rings, at least the rolling surfaces of the rollers and / or the end surfaces of the rollers have an average particle diameter of 45 μm or more. Abrasive particles containing abrasive grains are collided with the surface of the elastic body so that the surface roughness Ra of the rolling surface of the roller and / or the end surface of the roller is 0.02 to 0.07 μm. Grind. If the surface roughness Ra of the rolling surface of the roller and / or the end surface of the roller exceeds 0.07, the seizure life will be reduced, so it is set to 0.07 or less. Further, if the surface roughness Ra is less than 0.02, the processing time is increased for controlling the roughness, the cost is increased, and the effect of the roughness control is saturated. The surface roughness Ra is required to be 0.02 to 0.07 at least on the rolling surface of the roller and / or the end surface of the roller, but is selectively formed on the inner ring and the outer ring raceway surface and the inner ring and the outer ring. It is more preferable that the range is also controlled in this range.

  In the present invention, it has been found that it is not sufficient to define the surface roughness Ra in order to improve the seizure life and the peeling life, and it is effective to reduce the maximum height Rz. Of the inner ring and outer ring raceway surfaces, the rolling surfaces and end surfaces of the rollers, and the flange surfaces formed on the inner and outer rings, at least the ratio between the surface roughness and the maximum height of the rolling surfaces of the rollers and / or the end surfaces of the rollers is Rz. / Ra ≦ 3. When Rz / Ra exceeds 3, the baking life is reduced, so that it is set to 3 or less. Rz / Ra is required to be 3 or less at least on the rolling surface of the roller and / or the end surface of the roller, but it is also 3 or less on the inner ring and the outer ring raceway surface and the flange formed on the inner ring and the outer ring. More preferably, it is controlled.

  In the present invention, as described above, the surface property is controlled by mirror shot processing in which abrasive particles composed of abrasive grains are collided with the surface of an elastic body having an average particle diameter of 45 μm or more. In the mirror shot processing, generally, abrasive particles such as hard diamond attached to the surface of an elastic body such as rubber are used as abrasive particles. In this method, the abrasive particles are projected onto an object using air pressure and impeller (mechanical energy) to process the surface. When the average particle diameter of the elastic body is less than 45 μm, the collision energy is small and efficient polishing becomes difficult.

The abrasive contained in the elastic body of the abrasive particles used in the present invention is not particularly limited as long as it is a hard member having an appropriate hardness, but diamond, alumina, or silicon carbide is preferably used.
Natural rubber, synthetic rubber, natural resin, and synthetic resin are used as the elastic material of the abrasive particles used in the present invention, but are not particularly limited. These rubbers or resins may contain various additives. When the abrasive particles collide with the surface of the object to be burned, heat is generated by the collision energy, so if the elastic body is a thermoplastic resin or rubber, it tends to soften due to the collision energy, and the surface to be polished tends to form during sliding. Therefore, it is more preferable.

  In the present invention, it is preferable that at least a portion of 75% or more and 95% or less in the area ratio of the rolling surface of the roller and / or the end surface of the roller is a polishing surface due to collision of abrasive particles. When the area ratio of the polished surface is less than 75%, the effect of improving the seizure life and the peeling life tends to decrease, and when it exceeds 95%, the effect tends to decrease because galling occurs. It is preferable that it is 75 to 95%. The area ratio of the polished surface is more preferably in the range of 75 to 95% not only on the rolling surface of the roller and / or the end surface of the roller, but also on the inner ring and outer ring raceway surface and on the inner ring and outer ring. preferable.

  In the present invention, the surface roughness Ra (parallel) parallel to the rolling direction of the rolling surface and / or end face of the roller, and the surface roughness in the vertical direction is Ra (parallel) / Ra, which is the ratio of Ra (vertical). When (vertical) is α, it is preferable to satisfy 0.8 ≦ α ≦ 1.2. If the polished surface has no directionality, oil silence is likely to occur. If α exceeds 1.2, oil silence is likely to occur, so 1.2 or less, and 0.8 or more due to side leakage and centrifugal force.

  On the polished surface subjected to mirror shot, the area ratio of the portion where the abrasive particles remain is preferably as low as possible. In the present invention, the area ratio of particles having a particle size of 0.5 to 2 μm having a hardness Hv (Vickers hardness) of 800 or more is 0.05 to 1.2% or less on the surface subjected to mirror shot. It is preferable. When the area ratio in which the hard particles remain is 1.2% or more, the service life is remarkably reduced. Therefore, it is preferably 1.2% or less. If the area ratio in which the hard particles remain is less than 0.05%, it cannot be distinguished from the hard particles contained from the time of steelmaking of the bearing.

Moreover, if it is a particle | grain below Hv800, it will not have a big influence on a lifetime. On the other hand, when particles of Hv 800 or higher are stuck and remain, the surface starting type peeling starts.
The particle size of the remaining particles is preferably 0.5-2 μm. The larger the particles are, the shorter the life is. Therefore, the presence of particles having a particle size exceeding 2 μm is not preferable because the life is decreased. Further, since particles less than 0.5 μm may be included during steelmaking of the bearing, there is no problem.

  The inner raceway surface of the roller bearing of the present invention is preferably treated with manganese phosphate. Manganese phosphate treatment can impart wear resistance by immersing the surface to be treated in a manganese phosphate treatment solution. Other chemical conversion treatments such as phosphate treatment and chromate treatment, and surface treatment such as black dyeing may be used.

Hereinafter, the present invention will be described more specifically based on examples. Tapered roller bearings for rolling mill roll necks were prepared and their life was evaluated. The specifications of this tapered roller bearing are as follows.
Identification number: HR32017XJ
Bearing inner diameter: 85mm
Bearing outer diameter: 130mm
Assembly width: 29mm
Basic dynamic load rating: 143000N
Rotation speed: 1500min ^-1
Lubricant: Grease (Lithium soap grease, 177 cSt @ 40 degrees)
Moreover, the inner ring, the outer ring, and the rolling element are made of SUJ2 steel, and the properties thereof are as follows.

Surface hardness: HRC58-64
Surface retained austenite amount: 20 to 45% by volume
Surface carbon concentration: 0.8-1.1% by mass
Surface nitrogen concentration: 0.05 to 0.3% by mass
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.

  The apparatus used for the test for life evaluation is shown in FIG. In FIG. 3, reference numeral W denotes a tapered roller bearing (workpiece) of a test object, reference numeral 31 denotes an inner ring, reference numeral 32 denotes an outer ring, reference numeral 33 denotes a tapered roller, and reference numeral 34 denotes a cage. The work W is mounted by fitting the inner ring 31 to the bearing seat 36a at one end of the rotating shaft 36 of the life testing machine, and the outer ring 32 is fitted and fixed to the outer ring fitting member 38 of the housing 37 of the testing machine. A radial load Fr is applied to the rotary shaft 36 by a radial load loading means (not shown), thereby loading the workpiece W 1 with a radial load. Further, an axial load Fs is applied to the outer ring fitting member 38 by a hydraulic cylinder (not shown), thereby applying an axial load to the workpiece W 1.

  The life test was conducted while pouring water. The water injection condition is 30 cc / 6 hr. In order to generate peeling due to rust, (1) after rotating for 96 hours in the above operation, (2) water was injected with the rotation stopped for 96 hours. This generates rust during the stop. The above steps (1) and (2) are performed in a cycle of (1) → (2) → (1) → (2) → (1)... Until peeling occurs.

  In the present invention, the seizure life means the life until peeling occurs. In this example, the peeling was determined as seizure by determining that the torque was three times the initial value or the bearing temperature increased by 20 ° C. as seizure. Table 1 shows the results of the life test. In addition, the numerical value of the life in Table 1 is shown as a relative value when the life of the bearing of Comparative Example 17 is 1.

  Referring to Table 1, Examples 1 to 16, which are examples of the present invention, all have a surface roughness Ra in the range of 0.02 to 0.07 μm, and a ratio between the surface roughness Ra and the maximum height Rz. Since Rz / Ra is 3 or less, it can be seen that the baking life is 3.2 to 14 times that of Comparative Example 17, which is remarkably excellent.

  In Example 12, since the area ratio of the polished surface is 70%, the lifetime is not improved as much as the other examples, but it can be seen that it is remarkably improved as compared with the comparative example. In Examples 13 and 16, α which is the ratio of the surface roughness Ra (parallel) parallel to the rolling direction to the surface roughness Ra (vertical) in the vertical direction is 0.8 ≦ α ≦ 1. Since it is out of the range of 2, the lifetime is not improved as much as the other examples, but it can be seen that it is remarkably improved as compared with Comparative Examples 17-20. In Comparative Examples 17 to 19, the surface roughness Ra is outside the scope of the present invention, and in Comparative Example 20, Rz / Ra is outside the scope of the present invention.

  Further, in Table 1, a manganese phosphate coating is formed on the inner ring only in Example 9 and Comparative Example 19. In Example 9, the surface properties of the rolling surface of the roller and / or the end surface of the roller satisfy the scope of the present invention, and the life is remarkably improved by the formation of the manganese phosphate coating on the inner ring. However, as shown in Comparative Example 18, even if a manganese phosphate coating is formed on the inner ring, the bearing is not effective in terms of the surface properties of the roller rolling surface and / or the roller end surface. I understand that there is no.

  Furthermore, the optical micrograph of the result of having observed the grinding | polishing surface of Example 10 with the optical microscope was shown in FIG. As a result of analyzing the micrograph in FIG. 4, it was found that the area ratio of particles having a particle diameter of 0.5 to 2 μm was 0.4%.

  ADVANTAGE OF THE INVENTION According to this invention, the roller bearing excellent in the seizure lifetime and the peeling lifetime can be provided. Moreover, since the mirror shot processing is performed, the abrasive grains adhering during the polishing processing can be removed, and the seizure life can be improved, so that the industrial applicability is high.

DESCRIPTION OF SYMBOLS 1 Cylindrical roller bearing 11 Inner ring 13 Inner ring collar 15 Outer ring 17 Outer ring collar 19 Cylindrical roller 21 Roller 23 Shot blast nozzle 25 Abrasive particle 27 Abrasive grain 29 Elastic body 31 Inner ring 32 Outer ring 33 Tapered roller 34 Cage 36 Rotating shaft 36a Bearing seat 37 Howdin 38 Outer ring fitting member

Claims (5)

  An inner ring having an inner ring raceway surface, an outer ring having an outer ring raceway surface, a roller disposed so as to be able to roll between the both raceway surfaces, and a flange selectively formed on the inner ring and / or the outer ring. A roller bearing provided, wherein the inner ring raceway surface, the outer ring raceway surface, the roller rolling surface, the roller end surface, and the flange surface, at least the roller rolling surface and / or the roller By causing the end surface to collide with abrasive particles containing abrasive grains on the surface of an elastic body having an average particle size of 45 μm or more, the rolling surface of the roller and / or the end surface of the roller has a surface roughness ( Ra) is 0.02 to 0.07 μm, and the polishing surface has a ratio Rz / Ra between the surface roughness (Ra) and the maximum height (Rz) satisfying Rz / Ra ≦ 3. Roller bearing characterized by   2. The roller bearing according to claim 1, wherein the polished surface has an area ratio of 75% or more and 95% or less of a rolling surface of the roller or an end surface of the roller.   The roller bearing according to claim 1, wherein the abrasive grains are made of diamond, alumina, or silicon carbide.   Ra (parallel), which is the ratio of the surface roughness Ra (parallel) parallel to the rolling direction on the rolling surface and / or end surface of the roller to the surface roughness Ra (vertical) perpendicular to the direction. The roller bearing according to claim 1, wherein when α / Ra (vertical) is α, 0.8 ≦ α ≦ 1.2 is satisfied.   The roller bearing according to any one of claims 1 to 4, wherein the inner ring raceway surface is subjected to manganese phosphate treatment.

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