JPH11141554A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the maximum load capacity of a roller by inhibiting the concentration of the damage such as the equivalent stress, the maximum shearing stress or the like, received by a material. SOLUTION: A raceway surface 14 of an inner ring 12 and a raceway surface 15 of an outer ring 13 are usually formed into the shape of a circular cone. Accordingly by forming the sectional shape along a bus, of an outer peripheral face 18 of a conical roller 16, into the crowning shape determined by a specific expression, the distribution of the equivalent stress in a bus direction can be unified, and the concentration of the damage inside of a material can be prevented. A relative gap between an border line of the roller 16 and a border line of the inner ring, is determined to unify the distribution of the dimensionless equivalent stress in a bus direction of the conical roller 16. Accordingly the concentration of the dimensionless equivalent stress on the edge parts of both ends in an axial direction of the conical roller 16 can be prevented. That is, the static maximum load capacity and the dynamic maximum load capacity of the conical roller 16 can be increased by an amount corresponding to the prevention of the concentration of the dimensionless equivalent stress.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the crowning shape of a roller in a rolling bearing.

[0002]

2. Description of the Related Art Conventionally, in a cylindrical roller bearing or a tapered roller bearing, a bus of a roller disposed between an inner ring and an outer ring has
In order to avoid concentration of contact pressure, a slight bulge called crowning is formed. Lundberg has proposed a crowning shape that makes the contact pressure uniform in the axial direction of the rollers, and this crowning shape is currently considered optimal.

[0003]

However, according to the conventional Lundberg crowning shape, a uniform contact pressure distribution in the axial direction of the rollers is certainly exhibited. However, when evaluating the damage actually taken by the above rollers,
There is a problem that the distribution of damage to the material such as fracture, metal fatigue and plastic deformation in the axial direction is not uniform. FIG.
Is the equivalent stress σ under the uniform contact pressure in the axial direction generated in the above roller applying the Lundberg crowning shape.
_E shows the distribution of Hertz (Hertz) maximum contact stress P _h in dimensionless dimensionless equivalent stress sigma _E of (= sigma _E / P _h) a. here,
Equivalent stress σ _E is a kind of von ·
It is a stress component used for the yield condition of Mises (Von Mises).

[0004] From FIG. 8, the dimensionless equivalent stress す る_E for evaluating damage to a material such as fracture, metal fatigue and plastic deformation inside the roller is 0.8 times the effective length in the radial direction from the rotation axis. At the point A in the form of a band. In particular, a strong value exceeding the yield stress (= 0.60) is shown in the region B near the side surface of the strip-shaped portion A, and it can be seen that the breakdown starts from the region B. Thus, even if the contact pressure distribution is made uniform in the axial direction, the three-dimensional equivalent stress distribution is not always uniform, and there are places where the equivalent stresses are concentrated. Therefore, there is a problem that the maximum load capacity cannot be given to the cylindrical roller.

An object of the present invention is to provide a rolling bearing which can increase the maximum load capacity by eliminating the concentration of damage to a material represented by an equivalent stress or a maximum shear stress.

[0006]

Means for Solving the Problems To achieve the above object, the invention according to claim 1 is directed to a rolling bearing having a raceway, wherein the distance between the contact surface between the roller and the raceway in the axial direction of the roller is increased. The change is set so that the physical quantity for evaluating the damage to the material such as the equivalent stress distribution or the maximum shear stress distribution in the axial direction under the contact pressure becomes uniform.

According to the above configuration, the change in the distance between the contact surfaces between the rollers and the raceway in the axial direction is represented by an equivalent stress distribution or a maximum shear stress distribution in the axial direction under a contact pressure. The material is set so that the damage it receives is uniform. Therefore, there is no place where damage is concentrated on the material represented by the equivalent stress or the maximum shear stress, and the maximum load capacity of the roller is increased by that amount.

According to a second aspect of the present invention, in the rolling bearing according to the first aspect of the present invention, the axial change in the distance between the contact surface between the roller and the track is substantially expressed by the following equation. It is characterized by being represented.

(Equation 2)

According to the above configuration, the equivalent radius R in the rotational direction, the equivalent Young's modulus E ', the effective length _{Lwe of the} rollers, the strength σ _{Emax of} the material compression, and the strength τ _max of the maximum shear stress of the material. , The distance between the contact surface of the roller and the raceway can be easily obtained such that the equivalent stress distribution or the maximum shear stress distribution in the axial direction under the contact pressure becomes uniform.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a side view of a tapered roller bearing as an example of the rolling bearing of the present embodiment. FIG. 2 is a sectional view taken along the line II in FIG. The tapered roller bearing 11 includes an inner ring 12, an outer ring 13, a tapered roller 16, and a retainer 17 (shown only in FIG. 2 and omitted in FIG. 1). The large-diameter end of the tapered roller 16 is pressed against the large collar 19 of the inner ring 12 so that the axial position of the tapered roller 16 is determined.

The shaft 20 and the outer ring 13 of the tapered roller 16
The problem of the relative gap between the roller contour, which is the intersection of the plane passing through the shaft 21 of the tapered roller and the outer peripheral surface 18 of the tapered roller 16, and the outer ring contour, which is the intersection of the raceway 15 of the outer ring 13 and the above plane, is as follows. 3 can be replaced by the problem of the gap between the finite width cylinder 25 and the semi-infinite body (hereinafter, simply referred to as a plane) 26 as shown in FIG. In FIG. 3, X, Y, and Z are dimensionless coordinates.
The axis is x / b, the Y axis is y / b, and the Z axis is z / b. Where x,
y and z are coordinates, and b is 接触 of the contact width of Hertz in the rotation direction. Similarly, the roller outline and the inner ring 12
The problem of the relative gap between the raceway surface 14 and the inner ring contour which is the line of intersection of the above-mentioned plane can also be replaced with the dynamic model shown in FIG. Therefore, the relative gap between the roller contour and the outer ring contour and the relative gap between the roller contour and the inner ring contour will be described below with reference to the dynamic model of FIG. In addition, the relative gap between the roller contour and the outer ring contour,
Since the relative gap between the roller contour and the inner ring contour is symmetric with respect to the shaft 20 of the tapered roller 16, if only one is described, the other is the same.

As described above, the finite width cylinder 2 shown in FIG.
5 and the plane 26, a finite width cylinder 25
Even if the contact pressure distribution is uniform in the axial direction of the finite width cylinder 25, the three-dimensional equivalent pressure distribution will not be uniform. Therefore, in the present embodiment, focusing on the above points, the finite width cylinder 2 is set so that the equivalent stress distribution or the maximum shear stress distribution in the axial direction of the finite width cylinder 25 becomes uniform.
The crowning shape of No. 5 (that is, the crowning shape of the tapered roller 16) is determined.

First, an arbitrary crowning shape is given to the finite width cylinder 25, and the relative distance H between two contacting objects (that is, between the finite width cylinder 25 and the plane 26) is determined by using a basic formula in the dry contact problem. And contact pressure. Then, a three-dimensional internal stress distribution is obtained using the obtained contact pressure distribution, and an equivalent stress is obtained from the three-dimensional internal stress distribution by the following equation. σ _E = [1/2 {(σ _X −σ _Y ) ² + (σ _Y −σ _Z ) ² + (σ _Z −σ _X ) ²
+ 6τ _XY ² + 6τ _YZ ² + 6τ _ZX ² } ^0.5 ] where σ _E : equivalent stress σ _X : vertical stress component acting on the YZ plane σ _Y : vertical stress component acting on the XZ plane σ _Z : acting on the XY plane Vertical stress component τ _XY : Shear stress component acting on XY plane τ _YZ : Shear stress component acting on YZ plane τ _ZX : Shear stress component acting on ZX plane

Then, the crowning shape is changed so that the distribution of the equivalent stress σ _E thus obtained is uniform in the axial direction of the finite width cylinder 25, and the above analysis is repeated. Thus, the crowning shape is determined so that the damage inside the material is uniformly distributed in the axial direction.

The equation of the crowning shape derived as described above is as follows.

(Equation 3)

FIG. 4 is a diagram showing an example of the crowning amount of the finite width cylinder 25 calculated by the above-mentioned equation of the crowning shape. Further, FIG. 5, the crowning profile of the formula has been applied maximum contact Hertz contact pressure p in a finite width cylinder 25 stresses P _h in dimensionless dimensionless contact pressure P of the (= p / P _h) Distribution. FIG. 5A shows the contact pressure distribution on the ZX plane when Y = 0, and FIG. 5B shows the contact pressure distribution on the YZ plane when X = 0. FIG. 6 is similar to FIG.
Shows the distribution of dimensionless equivalent stress sigma _E in the axial direction at the same loading conditions as for.

As can be seen from FIG. 5 (b), according to the crowning shape in the present embodiment, the contact pressure distribution in the axial direction of the finite width cylinder 25 is slightly from the center to the edges at both ends in the axial direction. And gradually decreases at the edge portion.

[0018] Thus, as can be seen from the distribution of non-dimensional equivalent stress sigma _E in the Y-axis direction shown in FIG. 6, the non-dimensional equivalent stress sigma _E at the edge portion of the case of applying the crowning shape of the Rundoberugu (See FIG. 8) disappears, and decreases as it is in a curve. As a result, the concentration of a strong equivalent stress exceeding the yield stress appearing in the vicinity of the side surface of the band-shaped region A as shown in FIG. 8 is avoided.

Normally, the raceway surface 14 of the inner race 12 and the raceway surface 15 of the outer race 13 are formed in a conical shape. Therefore, in this case, if the cross-sectional shape of the outer peripheral surface 18 of the tapered roller 16 along the generatrix is a crowning shape determined by the above equation, the equivalent stress distribution in the generatrix direction can be made uniform, and It is possible to eliminate the point where the damage is concentrated. When the raceway surface 14 of the inner race 12 and the raceway surface 15 of the outer race 13 are not conical, the relative gap between the above-mentioned roller contour and the outer race contour,
And, the relative gap between the roller contour and the inner ring contour,
What is necessary is just to make it into the shape calculated | required by said Formula.

As described above, in the present embodiment,
The relative gap between the above-mentioned roller contour and the outer ring contour between the tapered roller 16 and the outer ring 13 that mutually transmit rolling force, and the above-mentioned roller and inner ring contour between the tapered roller 16 and the inner ring 12. Are determined so as to make the distribution of the dimensionless equivalent stress の_E in the generatrix direction of the tapered rollers 16 uniform. Therefore, it is possible to prevent the non-dimensional equivalent stress 両 端_E from being concentrated at both axial end portions of the tapered roller 16. That is, according to the present embodiment, dimensionless equivalent stress Σ _E
, The static maximum load capacity and the dynamic maximum load capacity of the tapered roller 16 can be increased.

FIG. 7 shows the relationship between the cumulative failure probability and the life time when the crowning shape according to the present embodiment and the Lundberg crowning shape are applied to the tapered rollers of the tapered roller bearing. From FIG. 7, it is approximately 1 when the crowning shape according to the present embodiment is applied.
A 0-fold improvement in life was observed. That is, the above tapered roller 1
6 is made of the same material as that of the conventional tapered roller and has the same macroscopic dimensions, the rolling fatigue life is 3 to 10 times by applying the crowning shape of the present embodiment according to the above equation. It has been proven to grow phenomenally.

In the above embodiment, a tapered roller bearing used as a radial bearing is described as an example. However, a tapered roller bearing used as a thrust bearing may be used. Needless to say, the present invention is also applicable to the case of a cylindrical roller bearing. Further, the present invention can be applied to a linear bearing having a flat raceway surface.

[0023]

As is apparent from the above description, the rolling bearing according to the first aspect of the present invention is capable of detecting the axial change in the distance between the contact surface of the roller and the track in the axial direction under a contact pressure. Since the physical quantity for evaluating the damage to the material such as the equivalent stress distribution or the maximum shear stress distribution to the material is set to be uniform, the point where the damage to the material represented by the equivalent stress or the maximum shear stress is concentrated Does not exist, and the static maximum load capacity and the dynamic maximum load capacity of the above rollers can be increased accordingly. Further, it is possible to improve the pressure resistance and life of the rollers.

In the rolling bearing according to the second aspect of the present invention, the change in the axial direction in the space between the contact surface of the roller and the track is substantially expressed by the following equation. If the equivalent radius R, the equivalent Young's modulus E ', the effective length _{Lwe of the} roller, the strength σ _Emax of the material for compression, and the strength τ _max of the maximum shear stress of the material are known, the axial direction under the contact pressure can be obtained. Can be easily obtained such that the equivalent stress distribution or the maximum shear stress distribution becomes uniform.

(Equation 4)

[Brief description of the drawings]

FIG. 1 is a side view of a tapered roller bearing as an example of a rolling bearing of the present invention.

FIG. 2 is a sectional view taken along the line II in FIG.

FIG. 3 is a diagram showing a dynamic model of the tapered roller bearing shown in FIGS. 1 and 2;

FIG. 4 is a diagram showing an example of a crowning amount applied to the tapered rollers in FIGS. 1 and 2;

FIG. 5 is a view showing a contact pressure distribution of tapered rollers in FIGS. 1 and 2;

6 is a view showing a dimensionless equivalent stress distribution of the tapered rollers in FIGS. 1 and 2. FIG.

FIG. 7 is a diagram showing the relationship between the cumulative failure probability and the life time when the crowning shape according to the present invention is applied to the tapered rollers and when the Lundberg crowning shape is applied.

FIG. 8 is a diagram illustrating a dimensionless equivalent stress distribution under the same load condition as in FIG. 6 when a Lundberg crowning shape is applied.

[Description of Signs] 11: Tapered roller bearing, 12: Inner ring, 13
... outer ring, 14,15 ... track surface,
16: tapered roller, 20: tapered roller shaft 21: outer ring shaft.

Claims (2)

[Claims] 1. A rolling bearing having a raceway, wherein a change in the distance between the contact surface of the roller and the raceway in the axial direction of the roller corresponds to an equivalent stress distribution or a maximum shear stress in the axial direction under a contact pressure. A rolling bearing, wherein a physical quantity for evaluating damage to a material such as distribution is set to be uniform. 2. The rolling bearing according to claim 1, wherein the change in the distance between the contact surfaces of the rollers and the raceway in the axial direction is substantially represented by the following equation. bearing. (Equation 1)