阅读说明：本技术 圆锥滚子轴承 (Tapered roller bearing ) 是由 千岛将来 山中启阳 大岛裕之 于 2020-03-19 设计创作，主要内容包括：在圆锥滚子轴承(10)中,对于圆锥滚子(13)的至少滚动面(13c)及大直径侧端面(13b)的表面粗糙度,突出峰部高度Rpk为0.02～0.17μm,芯部的水平差Rk为0.12～0.21μm,突出谷部高度Rvk为0.07～0.43μm,在该圆锥滚子(13)的表面存在的细微的凹凸中的凹部的平均面积为5μm～(2)以下。由此,通过在稀薄润滑情况下、润滑油低粘度化情况下使油膜形成性提高,能够兼顾抑制滚动接触部分处的表面损伤以及抑制滑动接触部分的摩擦增加。(In a tapered roller bearing (10), the height Rpk of the projecting crests is 0.02 to 0.17 [ mu ] m, the level difference Rk of the core is 0.12 to 0.21 [ mu ] m, the height Rvk of the projecting troughs is 0.07 to 0.43 [ mu ] m, and the average area of the recesses in the fine irregularities present on the surface of a tapered roller (13) is 5 [ mu ] m, with respect to the surface roughness of at least the rolling surface (13c) and the large-diameter side end surface (13b) of the tapered roller (13) 2 The following. Thus, by improving the oil film formability in the case of lean lubrication or in the case of a low viscosity of the lubricating oil, it is possible to achieve both suppression of surface damage at the rolling contact portion and suppression of an increase in friction at the sliding contact portion.)

1. A tapered roller bearing is provided with:

an inner ring and an outer ring; and

a plurality of tapered rollers arranged between the inner ring and the outer ring so as to be rollable, wherein the tapered roller bearing is characterized in that,

the height Rpk of the projecting peak part is 0.02 to 0.17 μm and the level difference Rk of the core part is 0.1 with respect to the surface roughness of at least the rolling surface and the large-diameter side end surface of each tapered roller2 to 0.21 μm, a height of a projected valley portion Rvk of 0.07 to 0.43 μm, and an average area of a concave portion in fine irregularities present on the surface of the tapered roller of 5 μm ²The following.

2. The tapered roller bearing according to claim 1,

the surface of each of the tapered rollers is finished by barrel processing,

the hardness of the polar surface of the surface is 105% to 135% relative to the surface before the roller processing.

3. Tapered roller bearing according to claim 1 or 2,

the aspect ratio Str of the surface properties of each tapered roller is 0.2 or more.

Technical Field

The present invention relates to a tapered roller bearing, and more particularly to a tapered roller bearing used for a transmission or a differential of a vehicle.

Background

In recent years, from CO₂In view of the improvement in fuel consumption of an engine and the improvement in electric power consumption in the case of an electric vehicle due to emission regulations, it is required to improve rotational efficiency even when a rolling bearing used in a transmission or the like is used in a lean lubrication condition in which stirring resistance is low or when the viscosity of lubricating oil is reduced.

In addition, conventionally, various proposals have been made for specifying the surface properties of the rolling elements in such a rolling bearing used under the lean lubrication. For example, in the rolling bearing described in patent document 1, it is specified that a plurality of independent dimples of a minute concave shape are formed at random on at least one of the surface of the rolling element and the raceway surface of the raceway ring, that the surface is formed as a smooth surface except the dimples, and that the equivalent circle diameter is removed When the area ratio of the depressions is 14% to 21%, the average area is 10 μm²Above and 30 μm²The maximum area is 300 μm²Above and 500 μm²The volume of the recess is 0.007mm³/cm²Above and 0.010mm³/cm²The following.

In the tapered roller bearing described in patent document 2, the roller coefficient γ is set to exceed 0.94 by reducing the roller pitch diameter, and a plurality of minute concave-shaped dimples are randomly provided on the surface of the tapered roller, the surface roughness parameter Ryni of the surface on which the dimples are provided is set to 0.4 μm or less and Ryni or less and 1.0 μm or less, the Sk value is set to-1.6 or less, and the cage is set to a specific shape.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4754234

Patent document 2: japanese patent No. 4994638

Disclosure of Invention

Technical problem to be solved by the invention

However, when the rolling element having the surface properties described in patent document 1 is applied to a tapered roller bearing, even in the case of thin lubrication or in the case of a low viscosity of the lubricating oil, surface damage such as flaking can be suppressed by improving the oil film formability of the rolling contact portion at the rolling contact portion between the rolling surface of the tapered roller and the raceway surface of the raceway ring. However, at the sliding contact portion between the large diameter side end surface of the tapered roller and the large flange portion, the irregularities of the large diameter side end surface of the tapered roller are large, and the effect of deterioration of the oil film forming property due to deterioration of the surface roughness is stronger than the effect of improvement of the oil film forming property due to improvement of the lubricant oil retaining property, and thus there is a possibility that deterioration, seizure, or the like of the bearing rotational torque due to increase of friction occurs.

In the tapered roller bearing described in patent document 2, the sliding contact portion between the large-diameter side end surface of the tapered roller and the large flange portion is not considered.

Accordingly, an object of the present invention is to provide a tapered roller bearing which is defined by using a parameter that more accurately indicates the surface properties of tapered rollers, and which can achieve both suppression of surface damage at rolling contact portions and suppression of deterioration of bearing rotational torque and burnout deterioration at sliding contact portions without deteriorating oil film formability in the case of lean lubrication or the case of a reduction in viscosity of lubricating oil.

Means for solving the problems

That is, the above object of the present invention is achieved by the following configuration.

(1) A tapered roller bearing is provided with:

an inner ring and an outer ring; and

a plurality of tapered rollers arranged between the inner ring and the outer ring so as to be rollable, wherein the tapered roller bearing comprises a plurality of tapered rollers,

the height Rpk of the projecting peak part is 0.02 to 0.17 [ mu ] m, the level difference Rk of the core part is 0.12 to 0.21 [ mu ] m, the height Rvk of the projecting valley part is 0.07 to 0.43 [ mu ] m, and the average area of the recessed part in the fine unevenness existing on the surface of each tapered roller is 5 [ mu ] m ²The following.

(2) The tapered roller bearing according to (1), wherein,

the surface of each of the tapered rollers is finished by barrel machining,

the hardness of the surface, the pole surface, is 105% to 135% of the hardness of the surface before the roller processing.

(3) The tapered roller bearing according to (1) or (2), wherein,

the aspect ratio Str of the surface properties of each tapered roller is 0.2 or more.

Effects of the invention

In the tapered roller bearing of the present invention, the average area of the concave portions is reduced to 5 μm for at least the surface properties of the rolling surface and the large-diameter side end surface²Hereinafter, by setting Rpk, Rk, and Rvk to finer irregularities defined in the above-described specific ranges, it is possible to improve the oil film formability in the case of lean lubrication or in the case of a low viscosity of the lubricating oil, and to achieve both suppression of surface damage at the rolling contact portion and suppression of deterioration of the bearing rotation torque and seizure at the sliding contact portion. Thus, a tapered roller bearing having a long life can be obtained without causing problems such as deterioration of bearing rotational torque and deterioration of seizure properties.

Drawings

Fig. 1 is a sectional view showing an example of a tapered roller bearing.

In fig. 2, (a) shows the three-dimensional surface roughness of the rolling surface of the tapered roller after the grinding and finishing, and (b) is a polar diagram showing the three-dimensional surface roughness by an angular spectrum.

In fig. 3, (a) shows the three-dimensional surface roughness of the rolling surface of the tapered roller after the barrel processing, and (b) is a polar diagram showing the three-dimensional surface roughness by an angular spectrum.

Fig. 4 is a graph showing the results of test 1.

Fig. 5 is a graph showing the results of test 2.

Fig. 6 is a graph showing the results of test 3.

Description of the symbols

10 tapered roller bearing

11 outer ring

12 inner ring

13 tapered roller

13b major diameter side end face

13c rolling surface

Detailed Description

Hereinafter, a tapered roller bearing according to an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in fig. 1, the tapered roller bearing 10 according to the present embodiment is suitable for use in a transmission or a differential of a vehicle used in a lubrication environment where oil film formation is poor, such as a lean lubrication condition or a low viscosity condition of a lubricating oil. The tapered roller bearing 10 includes: an outer ring 11 having an outer ring raceway surface 11a on an inner circumferential surface; an inner ring 12 having an inner ring raceway surface 12a on an outer circumferential surface; a plurality of tapered rollers 13 rollably disposed between the outer ring raceway surface 11a and the inner ring raceway surface 12 a; and a cage 14 that holds the plurality of tapered rollers 13 at equal intervals in the circumferential direction.

The inner race 12 has: a small flange portion 15 provided at the small-diameter-side end portion of the inner ring raceway surface 12 a; and a large flange portion 16 provided at a large-diameter side end portion of the inner ring raceway surface 12 a. The small flange portion 15 contacts the small diameter side end surface 13a of the tapered roller 13, and the large flange portion 16 contacts the large diameter side end surface 13b of the tapered roller 13.

In manufacturing the tapered roller 13 of the tapered roller bearing 10, a cylindrical material such as bearing steel is subjected to plastic working such as forging to form a frustum-conical intermediate material, and then at least the rolling surface 13c and the large-diameter side end surface 13b are subjected to grinding and grinding finishing. The surface of the tapered roller 13 immediately after the grinding finish is a surface having various directions (anisotropic surface), and a plurality of fine streak-like irregularities are formed. Fig. 2(a) is a three-dimensional surface roughness obtained by measuring the surface of the rolling surface 13c of the tapered roller 13 immediately after grinding and finishing by a three-dimensional surface roughness measuring instrument, and (b) is a polar diagram obtained by expressing the three-dimensional surface roughness by an angular spectrum, but a strong peak (angular spectrum) appears in a certain direction (in the vicinity of 90 ° in fig. 2). The polar diagram and the angular spectrum are specified by ISO 25178. In such a streak-like machining mark, the valley portions are gathered in one direction, and the retention ability of the lubricating oil is low.

Therefore, in the present embodiment, after the grinding finish, the rolling process is performed on all the surfaces including the rolling surface 13c, the small diameter side end surface 13a, and the large diameter side end surface 13b of each tapered roller 13, and a plurality of fine irregularities having no directivity and defined below are formed on all the surfaces. In particular, the rolling surface 13c and the large-diameter side end surface 13b of the tapered roller 13 are:

(a) the height Rpk of the projected peak is set to 0.02 to 0.17 μm, preferably 0.03 to 0.10 μm

(b) The level difference Rk of the core is set to 0.12 to 0.21 μm, preferably 0.12 to 0.19 μm

(c) The height of the projected valley portion Rvk is set to 0.07 to 0.43 μm, preferably 0.17 to 0.41 μm

(d) The average area of the concave portions was set to 5 μm²Hereinafter, it is preferably 1 μm²Hereinafter, more preferably 0.8. mu.m²The following.

Rpk, Rk and Rvk are defined in ISO 13565-1(JIS B0671-2). In addition, the average area of the concave portions is the area at the outermost surface position of the tapered roller 13.

By providing fine irregularities that satisfy the requirements (a) to (d), even in the case of thin lubrication or in the case of a low viscosity of the lubricating oil, it is possible to suppress surface damage due to oil film breakage at the rolling contact portions between the rolling surfaces 13c of the tapered rollers 13 and the raceway surfaces 11a and 12a of the outer ring 11 or the inner ring 12, and it is possible to suppress deterioration of the bearing rotational torque and deterioration of seizure properties at the sliding contact portions between the large-diameter side end surfaces 13b of the tapered rollers 13 and the large flange portions 16, and it is possible to maintain a good lubrication state at each contact portion, and to obtain a long-life tapered roller bearing 10.

Further, the hardness of the pole surface of the tapered roller 13 can be increased by barrel processing. The hardness of the pole surface after the barrel processing differs depending on the steel type and the heat treatment, but in the present embodiment, it is increased by 105% to 135%, preferably 110% to 120%, as compared with that before the barrel processing. The life can be improved by increasing the hardness of the pole surface. The pole surface is a portion from the surface to a depth of 5 μm, and the hardness of the pole surface is measured by a test force of 100g in a micro vickers hardness tester.

In addition, if the surface of the rolling surface 13c of the tapered roller 13 after the barrel processing is measured by using the three-dimensional surface roughness measuring instrument in the same manner, the three-dimensional surface roughness as shown in fig. 3(a) and the polar coordinate graph as shown in fig. 3(b) are obtained. In this case, all the surfaces including the rolling surface 13c, the small diameter side end surface 13a, and the large diameter side end surface 13b of the tapered roller 13 after the rolling process are non-directional surfaces (isotropic surfaces), and the angular spectrum is dispersed in almost all directions. In addition, the peak height of the angular spectrum is not particularly high for a specific angle, and it can be said that the irregularities are uniformly distributed in almost all directions.

As an index indicating an anisotropic surface and an isotropic surface, a surface property aspect ratio Str defined in ISO25178 is known. Str is in the range of 0 to 1, and the closer to 1, the higher the "isotropy". In the present embodiment, the aspect ratio Str of the surface properties of the surfaces 13a, 13b, and 13c of the tapered roller 13 is preferably 0.2 or more, more preferably 0.5 or more, and particularly preferably 0.7 or more. When Str is less than 0.2, the isotropy of the irregularities is insufficient, the retention ability of the lubricating oil due to the irregularities is insufficient, and the effect of improving the durability may not be sufficiently obtained.

Examples

The effects of the present invention were confirmed by tests 1 to 3 using conventional examples, examples and reference examples.

In the conventional example, a steel material (SUJ2) is subjected to plastic working, grinding, and finish grinding to produce a tapered roller of a tapered roller bearing. In the examples, the tapered rollers of the conventional examples were further barrel-processed to have surface properties shown in table 1. Further, in the reference example, under conditions different from those in the examples, the tapered rollers of the conventional example were barrel-processed to have surface properties shown in table 1. In the reference examples and examples in table 1, the number n of tapered rollers is 30, and Rpk, Rk, and Rvk represent the minimum value and the maximum value of the n tapered rollers.

[ Table 1]

	Rpk(μm)	Rk(μm)	Rvk(μm)	Average area of concave portion
					Reference example	0.01～0.29	0.17～0.37	0.25～0.95	1.2μm2The following
Examples	0.02～0.17	0.12～0.21	0.07～0.43	0.8μm2The following

(test 1)

In the tapered roller bearings using the tapered rollers of the conventional examples and examples, low viscosity oil (assumed to be ISO VG10 to VG15) supplied at the same supply amount was used as lubricating oil, and a durability test under a lean lubrication condition was performed. In the endurance test, a dynamic equivalent load of about 20000N is applied to make the bearing rotate at 4000min^-1The rotation was performed, and the rotation time until the occurrence of the abnormality was measured.

As a result, as shown in fig. 4, it is understood that in the conventional example, an abnormality such as peeling which is likely to occur in a situation where the oil film forming property is not good occurs at an early stage on the rolling surface of the tapered roller, but in the example, the abnormality does not occur even after about 8 times of the rotation time of the conventional example, and the oil film forming property improving effect by the fine irregularities is achieved, and the durability is improved.

(test 2)

Next, for the tapered roller bearings using the tapered rollers of the conventional examples, and reference examples, a general-purpose oil corresponding to ISO VG32 was applied as a lubricating oil to the bearings before the start of the test, and during the test, the axial load 4000N was applied without supplying the lubricating oil, and the bearings were rotated at 4000min ^-1The rotation was carried out, and the rotation time (seizure life) until seizure was reached between the large-diameter side end face mainly including sliding friction and the large flange portion was measured.

As shown in fig. 5, the seizure life was almost the same as that of the conventional example, but was reduced to about 1/4 in the reference example. This is considered to be because the reference example has larger fine irregularities than the examples, and therefore, friction between the large-diameter side end surface and the large flange portion increases, and heat generation increases.

(test 3)

Further, in the tapered roller bearings using the tapered rollers of the conventional examples, and reference examples, the rotational speed of the bearings was changed while supplying the same lubricating oil as in test 2, and an axial load 3000N was applied to the bearings, and the rotational torque of the bearings was measured for each rotational speed.

As a result, as shown in fig. 6, it is understood that the example and the conventional example show substantially the same behavior, but the bearing rotation torque at low speed is increased in the reference example in which the fine irregularities are larger than in the example.

From the above results, it was confirmed that the surface properties of each tapered roller of the tapered roller bearing including a plurality of tapered rollers are such that the height Rpk of the projecting peak portion is 0.02 to 0.17 μm, the level difference Rk of the core portion is 0.12 to 0.21 μm, the height Rvk of the projecting valley portion is 0.07 to 0.43 μm, and the average area of the recessed portions in the fine irregularities present on the surface of the tapered roller is 0.8 μm ²As described below, good durability, seizure resistance, and torque performance can be obtained.

While various embodiments have been described above with reference to the drawings, it is needless to say that the present invention is not limited to the examples. It is obvious that those skilled in the art can conceive various modifications and alterations within the scope of the present invention as defined by the claims. In addition, the respective components in the above embodiments may be arbitrarily combined without departing from the scope of the invention.

In addition, the present application is based on the japanese patent application filed on 25/3/2019 (japanese patent application 2019-56970), the contents of which are incorporated herein by reference.