JP2003042148A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing capable of preventing the occurrence of skidding damage during high speed rotation with a light load without using an advanced complex design. SOLUTION: When a pitch circle is set at Dm mm, a roller diameter is set at Da mm, the number of assembled rollers 3 is set at Z pieces, the length of a roller is set at Le mm, the sum of a crowning dropped amount at an inner ring raceway side is set at δi mm, and the sum of a crowning dropped amount at an outer ring raceway side is set at δo mm, the sum δi of the crowning dropped amount at the inner ring raceway side, the sum δo of the crowning dropped amount at the outer ring raceway side, and the number Z of the rollers are determined satisfying the following equalities. In case of ki<=0.027, ko<=0.04688×ki-0.000156 In case of ki>=0.027, ko<=0.01161×ki-0.0008

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supports a shaft such as a machine tool, a jet engine or a gas turbine having a light-load and high-speed rotating shaft. The present invention relates to a rolling bearing suitable for: Here, the light load generally means that the radial load P is the basic dynamic load rating Cr.
Means that the load is smaller than 0.05 times, that is, P <0.05 · Cr. 2. Description of the Related Art Generally, a rolling bearing is used for a portion to which a load is applied to some extent. Conversely, when a rolling bearing is used under a light load, a contact force between a rolling element and a raceway surface is insufficient. In some cases, slippage may occur between the two. This phenomenon becomes remarkable especially at high speed rotation, and may eventually lead to damage called skidding. [0003] When little load is applied to the bearings, such as for design reasons or during no-load operation, special consideration is required as a measure against skidding. Conventionally, for example, the following design has been made. Was. (1) By setting the radial gap to be negative, the contact force between the rolling element and the raceway surface is set to be large. This setting includes
A method in which the radial gap is negative over the entire circumference while keeping the raceway surface in a perfect circle, and a method in which the raceway surface shape on the outer ring side is mainly non-round (elliptical, conical, etc.) and only a part of the radial clearance There is a way to make it negative. (2) The retainer is of an inner ring guide type, and the rotation of the inner ring pulls the retainer at the outer diameter of the inner ring to promote the rotation of the retainer, thereby reducing the relative sliding of the rolling elements. (3) Increasing the number of pockets for holding devices more than the number of rolling elements,
Provide alternate pockets that do not accommodate rolling elements. However, the above-mentioned countermeasures have the following problems. In other words, in measures to make the radial gap negative, the radial gap must be set in anticipation of thermal expansion due to temperature rise during operation.However, the actual amount of thermal expansion depends on the mechanical device or operating environment in which the bearing is used. It is different, and it is generally difficult to estimate the temperature rise. Further, the allowable range of the gap tends to be narrow, and high-precision processing is required. In the countermeasure for using the cage as the inner ring guide system, it is necessary to newly consider the damage to the guide surface of the special guard device caused by dragging the cage with a predetermined traction force.
In particular, the problem increases as the rotation speed increases. In addition, simply increasing the number of pockets for holding devices to the number of rolling elements,
Depending on the distance between the adjacent rolling elements, there is a concern that the raceway surfaces of the inner ring and the outer ring are deformed in the radial load applying portion, which may cause an increase in vibration. In particular, the problem increases as the rotation speed increases. SUMMARY OF THE INVENTION The present invention has been made to address the above-described problems, and an object of the present invention is to provide a rolling bearing which can prevent skidding damage during high-speed rotation under a light load without performing a sophisticated and complicated design. And [0008] In order to solve the above problems, a rolling bearing according to the present invention is a rolling bearing in which rolling elements are arranged in a single row or double rows between an inner ring and an outer ring.
The pitch circle diameter is Dm (mm), the rolling element diameter is Da (mm), the rolling element length is Le (mm), the sum of the amount of crowning fall between the inner ring raceway surface and the rolling element rolling surface (hereinafter, inner ring raceway side crowning Δi (mm), the sum of the crowning fall of the outer ring raceway surface and the rolling element rolling surface (hereinafter, referred to as the sum of the crowning fall of the outer ring raceway side) is δo (mm), and the circumference. When the number of rolling elements arranged in one row in the direction is Z (pieces), the sum of the pitch circle diameter, the rolling element diameter, the rolling element length, the inner ring raceway side crowning reduction amount, and the outer ring raceway side crowning reduction amount It is characterized in that the sum and the number of rolling elements are values satisfying the following equation. When ki ≦ 0.027, ko ≦ 0.04688 × ki−0.000156 When ki ≧ 0.027, ko ≦ 0.01161 × ki + 0.0008 where: Here, the crowning falloff amounts are the displacement amounts δa and δb of the crowning from a reference plane as shown in FIG. As shown in FIG. 1, the sum of the crowning drop amounts in the present invention is the crowning drop amount δa of the rolling element rolling surface with respect to the rolling element length, and the crowning drop amount δb of the raceway surface at the corresponding position. Is the sum of Although FIG. 1 shows an example between the inner ring and the rolling element, the same applies to the area between the outer ring and the rolling element. The above-mentioned ki and ko are indices indicating the degree of crowning drop of the inner / outer ring raceway side with respect to the length of the rolling element of the rolling bearing. The values of ki and ko increase as the crowning drop amount increases. As shown in FIG. 2, the inventors have determined that the relative sliding speed between the inner ring (driving wheel) and the rolling element is V (m / s) based on the accumulated data and the theoretical analysis over many years. Although it depends on the conditions (load, rotation speed, lubrication condition, etc.), it has been confirmed that there is a limit value of the occurrence of skidding damage within a range of the relative slip velocity V of about 60 to 80 (m / s). That is, it was confirmed that when the relative sliding speed V was larger than the relative sliding speed limit value somewhere in the above range, skidding damage was remarkably generated. The present invention specifies the relationship between the crowning of the inner raceway surface and the rolling element rolling surface and the crowning of the outer raceway surface and the rolling element rolling surface, for example, to specify the relationship between the inner raceway surface and the rolling element rolling surface. By increasing the contact surface pressure and increasing the traction force acting on the rolling element's rotation, the relative sliding speed between the rolling element and the inner ring is consequently suppressed to prevent skidding damage. That is, in this embodiment, the contact area between the rolling element and the bearing ring is reduced by crowning, so that the surface pressure increases and the frictional force increases. As a result, the maximum rolling element load is reduced by the lubricating oil. Drag force (stirring resistance)
Is relatively reduced, the relative sliding speed V between the rolling elements and the drive wheels is kept low, and skidding damage is prevented. In FIG. 3 which is a schematic diagram, Fa represents the maximum rolling element load, and Fb represents the drag force. Reference numeral 5 represents a lubricating oil. Then, it was found that optimizing the crowning so as to satisfy the above-mentioned equation according to the specifications can prevent skidding damage, so the above equation is limited (see FIG. 7). Here, normally, the rolling element of the rolling bearing is driven by a rotating wheel in a load zone and rolls, and in a non-load zone, re-enters the load zone while rotating by its inertia. Here, the revolution of the rolling element (or the retainer) is in a state in which the sum of the drag force acting on each rolling element and the sum of the driving force (traction force) acting on the rolling element and the bearing ring are substantially balanced. The driving force becomes very small when the rolling element load is small. Therefore, the driving force acting on the rolling elements in the non-load zone is very small, and the sum of the driving forces is considered to be substantially the sum of the driving forces acting on the rolling elements in the load zone. The driving force is
It increases as the slip between the rolling elements and the bearing ring (spinning slip) increases, but reaches a plateau when it slides to some extent. It should be noted that there is a certain relationship between the rotation slip and the cage revolution speed. On the other hand, the drag force increases as the rotation speed increases. In a state where a certain load is applied, a large amount of driving force (corresponding to the drag force) is generated by a slight sliding of the rolling element, so that the rolling element (retainer) revolves in a rolling state in effect. Even when the rotation speed is low, the same can be said because the drag force is small. However, when the load is reduced, the reduction in the number of rolling elements in the load zone and the reduction in the rolling element load are combined, and the traction force is reduced, so that the (revolution) slip of the rolling elements is observed. This is particularly noticeable when the rotation speed is high (the drag force is large), and eventually leads to skidding damage. In the above invention, the crowning is optimized without complicated calculations of the dimensions of the bearing parts and the number of rolling elements, thereby suppressing the relative sliding speed and preventing skidding damage. Skidging damage can also be suppressed by regulating the roughness of the rolling elements and the raceway surface to suppress relative slippage. In this case, the rms of the inner raceway surface
The roughness is Ri (μm), and the rms roughness of the outer raceway surface is Ro (μm).
m), when the rms roughness on the rolling element bus is Rr (μm), the relative sliding speed is less than the limit value by defining the roughness of the rolling element and the raceway surface so as to satisfy the following two expressions. (See the third and fourth embodiments described later). √ (Ro ² + Rr ² ) ≦ 0.5 (μm) √ (Ro ² + Rr ² ) ≦ √ (Ri ² + Rr ² ) −
0.2 The applicant has disclosed the invention described in Japanese Patent Application No. Hei 11-200616 as a means for solving the same problem as the present application. While the relative slip speed is suppressed by defining the number to prevent skidding damage, the invention of the present application suppresses the relative slip speed by specifying the crowning according to the specifications to prevent skidding damage. It is to prevent. Next, an embodiment of the present invention will be described with reference to the drawings. The rolling bearing according to the present embodiment will be described using a single-row cylindrical roller bearing as an example. FIG.
FIG. 2 is a sectional view of the cylindrical roller bearing. In FIG. 4, the crowning shape is shown in a large scale for easy understanding. The pitch circle diameter is Dm (mm), and the roller diameter is Da.
(Mm), the number of rollers 3 to be incorporated is Z (pieces), the roller length is Le (mm), and the sum of the crowning drop of the inner raceway side is δi.
(Mm), the sum of the amount of crowning fall on the outer ring raceway side is δo (m
m), the pitch circle diameter Dm, the roller diameter Da, the roller length Le, the sum δi of the inner ring raceway-side crowning fall, the sum δo of the outer ring raceway-side crowning fall, δo, so as to satisfy the following equation: And the number Z of rollers are determined. Code 4
Represents a cage. When ki ≦ 0.027, ko ≦ 0.04688 × ki−0.000156 When ki ≧ 0.027, ko ≦ 0.01161 × ki−0.0008 where: For example, the inner ring 1, the outer ring 2, and the rollers 3 to be used
If the dimensions of the roller 3 and the number of the rollers 3 to be incorporated are determined, the crowning set on at least one of the raceway surfaces of the inner and outer rings 1 and 2 and the rolling surface of the rollers 3 is adjusted to satisfy the above expression. To do. By using the roller bearing with the above configuration, the radial load is 0.05% of the basic dynamic load rating.
High speed with a small light load state than doubled, for example be d _m n value is rotating at 700,000 or more, the occurrence of skidding damage can be greatly reduced. Furthermore, the skidding resistance can be improved by a simple design in which the crowning is specified by a simple calculation based on, for example, the roller diameter and the pitch circle diameter. Here, in the above description, a single-row roller bearing is illustrated, but a double-row roller bearing may be used, or the present invention can be applied to a case where a roller having another shape such as a tapered roller is used as a roller. Furthermore, even for rolling bearings that use balls as rollers,
The present invention is applicable. When determining the number Z of rollers to be incorporated,
The number of rollers Z may be selected so as to satisfy the following expression based on Japanese Patent Application No. 11-200616. 1.5 ≦ k ≦ 2.5 where k = (π · Dm) / (Z · Da). That is, since Z = (π · Dm) / (k · Da), it can be described as (π · Dm) / (1.5 · Da) to (π · D
m) / (2.5 · Da)
The number Z of rollers may be determined and incorporated. By defining the number of rollers Z in this way, it is possible to more reliably prevent skidding and to suppress inner ring runout to 1 μm or less. [First Embodiment] NU224 of standard design (inner diameter: 120 mm, outer diameter: 215 mm, width: 40 m)
m, the number of rollers: 16), when a rotation test was performed by the test device shown in FIG. 5 at a radial load of 500 N and a rotation speed of 11000 rpm, significant skidding damage occurred. When the bearing performance theoretical analysis was performed, the value of the relative sliding speed V was 72.0 (m / s). The pitch circle diameter of the bearing is 167.5 mm, and the diameter of the roller 3 is 24.0 mm. FIG. 6 shows that k = (π · Dm) / (Z · Da)
4 shows a graph in which a relative slip speed is obtained when is a variable. The above k is an index representing the ratio of the space length occupied by other than the rollers to the circumferential length at the pitch circle diameter of the rolling bearing, and becomes a larger value as the number of rollers is relatively reduced,
Further, k ≒ 1 represents a full-roller type rolling bearing. From FIG. 6, it can be seen that in the rolling bearing of the above specification, the limit value of the relative sliding speed at which skidding occurs is 64 (m / s). Here, in the test apparatus of FIG.
Is a screw for applying a radial load.
By adjusting the position, the amount of deflection of the radial load leaf spring 8 is adjusted. Reference numeral 9 denotes a test shaft (drive shaft), reference numeral 10 denotes a support bearing, and reference numeral 11 denotes a load bearing.
A radial load is applied by pulling up the center through the load bearing 11. Reference numeral 12 represents a test bearing,
Turbine oil is supplied as lubricating oil. Reference numeral 13 denotes the installation position of the sensor, which detects the runout of the inner ring 1 and the rotation speed of the retainer 4. Further, the relative slip speed V is obtained by calculating the rotation speed Vi of the inner ring 1 and the revolution speed Vc of the retainer, and V = Vi−
Vc. The rotation speed of the inner ring 1 is known in advance by calculation from the rotation speed of the test shaft and the groove size of the inner ring 1.
The revolution speed Vc of the cage can be obtained from the actually measured rotation speed Nc of the cage by using the following equation. [0030] Then, other than the sum δi of the inner ring raceway side crowning fall amount and the sum of the outer ring raceway side crowning fall amount δo, the radial load and the rotation speed of the inner ring are kept constant, and the sum δi of the inner ring raceway measurement crowning fall amount is maintained. The relative slip velocity values V were obtained by combining the sum δo of the crowning fall amounts of the outer ring raceway side under various conditions. FIG. 7 shows a summary of the results. However, the sums δi, δ of the crowning falling amounts in the present embodiment.
o assumes single circular crowning on the inner raceway surface, the outer raceway surface, and the roller rolling surface. In FIG. 7, the symbol x in parentheses (described as Example 1 in FIG. 7) is the position of the current product in which skidding has occurred in the rotation test. Further, ▲ indicates the position when the calculation results by the theoretical analysis are arranged by variously combining the crowning fall amounts on the inner and outer raceway side. As can be seen from the results shown in FIG. 7, the relative slip speed exceeds 64 (m / s) where the sum δi of crowning drops on the inner raceway side is small and the sum δo of crowning drops on the outer raceway side is large. It became. Further, it can be seen from the theoretical analysis that the crowning drop amount of the current product in which skidding has occurred belongs to a range exceeding the relative sliding speed of 64 (m / s). On the other hand, if the ko value is (ki
−0.00833) or less and 0.0011 or less, that is, ki ≦ 0.027 and ko ≦ (0.046
88 × ki−0.000156) (in FIG. 7,
At the position △ belonging to the gray trapezoidal portion), the relative sliding speed V is smaller than 64 (m / s), and it can be seen that no skidding damage occurs. That is, in the NU224 roller bearing of the standard design, the range of the gray trapezoidal portion in the drawing (ki ≦ 0.027 and ko ≦ (0.04688 × k
By setting a single arc crowning on the inner ring raceway surface, outer ring raceway surface, and roller rolling surface so as to be in the range of i-0.000156), skidding damage is obtained even under light load and high speed rotation conditions. It can be seen that can be prevented. [Second Embodiment] A cylindrical roller bearing (inner diameter: φ111 mm, outer diameter: φ157.84 mm, width: 20.5 mm, number of rollers:
25), radial load: 160N, rotation speed: 148
When a rotation test was performed at 00 rpm using the same test apparatus as described above (see FIG. 5), skidding damage was significantly generated. When the bearing performance theoretical analysis was performed, the value of V was 73 (m / s) which was larger than the skidding damage limit value. The pitch circle diameter of the test bearing is 135.5 mm,
The roller diameter is 11.0 mm. Therefore, while keeping the dimensions and radial loads other than the roller number Z and the rotational speed of the inner ring 1 constant, the number of rollers is reduced, and the relative sliding speed and the runout of the inner ring 1 at each roller number Z are reduced. When the amount (roller 3-pass vibration) was determined, the result shown in FIG. 8 was obtained. The horizontal axis is the k value described above. As can be seen from FIG. 8, in the above-mentioned rolling bearing, the boundary value of the relative sliding speed at which skidding occurs is 69 (m / s). The inner wheel raceway-side crowning drop amount is maintained by keeping the internal specifications other than the sum δi of the inner ring raceway-side crowning fallout amount, the sum of the outer ring-race-side crowning fallout amount δo, the radial load, and the rotation speed of the inner ring. Δi and the sum δo of the outer ring raceway side crowning fall amounts were combined under various conditions to determine the relative sliding speed V of each. The results are summarized in FIG. 7 described above.
Here, the sum δ of the crowning drop amount in the present embodiment
i and δo assume a single arc crowning on the inner raceway surface, the outer raceway surface, and the roller rolling surface. In FIG. 7, the symbol x in the triangle (described as Example 2 in FIG. 7) indicates the position of the current product where skidding has occurred in the rotation test. Further, the closed circles indicate the results of calculations based on theoretical analysis performed by combining the crowning dropouts of the inner and outer raceways. As can be seen from FIG. 7, when the sum δi of the crowning drop of the inner raceway side is small and the sum δo of the crowning fall of the outer raceway is large, the relative sliding speed exceeds 69 (m / s), resulting in skidding. It can be seen from the theoretical analysis that the amount of generated crowning fall of the current product belongs to a range exceeding the relative sliding speed of 70 (m / s). On the other hand, ki ≦ 0.02
7 and ko ≦ (0.04688 × ki− 0.000
156) and ki ≧ 0.027 and ko ≦
(0.01161 × ki + 0.0008) (FIG. 7)
At the point ○ belonging to the middle, gray trapezoidal portion), the relative sliding speed V becomes smaller than 69 (m / s), and no skidding damage occurs. As described above, by setting each crowning so as to be the sum of the respective crowning drop amounts satisfying the above-described formula based on the present invention, skidding damage can be suppressed in any rolling bearing. It turns out that it is possible. Here, in the first embodiment and the second embodiment,
Although both cases have been described only in the case of single arc crowning, the same effect can be expected in other crowning shapes, for example, in the case of partial crowning in which the center of the roller bus is straight. [Third Embodiment] Under the same rolling bearing (NU224) and the same test conditions as those of the first embodiment described above, with the dimensional specifications other than the roughness, the radial load, and the number of rotations of the inner ring kept constant, Inner ring synthesis rms Roughness and outer ring synthesis
The rms roughness was changed under various conditions in combination, and the values of V were obtained and arranged. As a result, the results shown in FIG. 9 were obtained. The number of rollers is 16 in the standard design specification. Here, the inner ring combined rms roughness = √ (Ri ² + Rr ² ), the outer ring combined rms roughness = √ (Ro ² + Rr ² ) where the rms roughness of the raceway surface of the inner ring 1 is Ri (μm), The rms roughness of the raceway surface of the outer ring 2 is Ro (μm), and the rms roughness on the roller bus is
s The roughness is Rr (μm). As can be seen from FIG. 9, √ (Ro ² + Rr ² ) ≦ 0.5 (μm) and √ (Ro ² + Rr ² ) ≦ √ (Ri ² + Rr ² ) −
By setting the specification value to be 0.2, the relative slip velocity V
Can be reduced to 64 (m / s) or less. Considering the meaning of the above equation, if √ (Ro ² + Rr ² )> 0.5 (μm), the traction (pulling force) of dragging the roller 3 by the raceway surface of the outer ring 2 becomes large. , Inner ring 1 side, roller 3
It is supposed that the relative slip speed V exceeds 64 (m / s) between the inner ring 1 and the raceway surface of the inner ring 1.
At high speed rotation, the outer ring 2 side traction is originally larger than the inner ring 1 side traction due to centrifugal force.
Therefore, √ (Ro ² + Rr ² ) ≦ 0.5 (μ
m), the traction conditions on the outer ring 2 side are relaxed. Further, {(Ro ² + Rr ² ) ≦ √
(Ri ² + Rr ² ) −0.2, that is, by increasing the traction on the inner wheel 1 side so that the traction on the inner wheel 1 side approaches the traction on the outer wheel 2 side, the relative sliding speed is reduced. Thus, skidding damage is prevented, and the life is improved. “−0.2” is an experimental value. As can be seen from FIG. 9, ９ (Ri ²
If + Rr ² ) exceeds 0.9, the roughness is too large, and even with a light load, wear and vibration increase, leading to a reduction in the life of the rollers. Therefore, √ (Ri ² + Rr ² ) is desirably 0.9 or less, preferably 0.7 or less. This embodiment can be applied to the bearing provided with the crowning of the first embodiment, and skidding can be more reliably prevented by a synergistic effect of an increase in traction force. [Fourth Embodiment] Under the same rolling bearing (a bearing used for a main shaft of a jet engine, etc.) and the same test conditions as those of the second embodiment, dimensions other than roughness, radial load, inner ring one revolution With the number kept constant, the combined rms roughness of the inner ring and the combined rms roughness of the outer ring were changed under various conditions in combination, and the values of each V were obtained and arranged. Obtained. The number of rollers is 25. As can be seen from FIG. 10, the same result as in FIG. 9 is obtained, where √ (Ro ² + Rr ² ) ≦ 0.5 (μm) and √ (Ro ² + Rr ² ) ≦ √ (Ri ² + Rr ² ) −
By setting the specification value to be 0.2, the relative slip velocity V
Can be reduced to less than 69 (m / s). The present embodiment can also be applied to the bearing provided with the crowning of the second embodiment, and skidding can be more reliably prevented by a synergistic effect of an increase in traction force. As described above, according to the present invention, it is only necessary to adjust the sum of the amount of crowning drop on the inner raceway side and the amount of crowning fall on the outer raceway side within a predetermined range. There is an effect that a bearing having excellent skidding resistance can be provided without performing special treatment on the bearing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a sum of crowning drop amounts. FIG. 2 is a diagram showing a relationship between a relative slip speed and a damage rate. FIG. 3 is a schematic diagram showing sliding of a rolling element. FIG. 4 is a sectional view showing a rolling bearing according to an embodiment according to the present invention. FIG. 5 is a sectional view showing an example of a test apparatus. FIG. 6 is a diagram showing a result of the first example. FIG. 7 is a diagram showing a relationship between ki and ko and a sliding speed. FIG. 8 is a diagram showing a result of the second embodiment. FIG. 9 is a diagram showing the results of the third example. FIG. 10 is a diagram showing the results of the fourth example. [Description of Signs] 1 Inner ring 2 Outer ring 3 Cylindrical roller (rolling element) 4 Cage Da Roller element diameter Dm Pitch circle diameter Z Number of rollers

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Shinichi Natsuda             Kanagawa Prefecture Fujisawa City Kugenuma Shinmei 1-chome 5-50             Nippon Seiko Co., Ltd. F term (reference) 3J101 AA15 AA24 AA32 AA42 AA43                       AA52 AA62 FA35 FA60 GA26                       GA31

Claims (1)

Claims: 1. In a rolling bearing in which rolling elements are arranged in a single row or double rows between an inner ring and an outer ring, a pitch circle diameter is Dm (mm), and a rolling element diameter is Da (mm). , The rolling element length is L
e (mm), δi (mm) is the sum of the crowning drop of the inner raceway surface and the rolling element rolling surface (hereinafter referred to as the sum of the crowning fall of the inner raceway side), and When the sum of the crowning drops (hereinafter referred to as the sum of the crowning drops on the outer ring raceway side) is δo (mm), and the number of rolling elements arranged in a line in the circumferential direction is Z (pieces), Rolling characterized in that the diameter, rolling element diameter, rolling element length, sum of inner ring raceway side crowning drop, sum of outer ring raceway crowning drop, and the number of rolling elements satisfy the following formulas: bearing. When ki ≦ 0.027, ko ≦ 0.04688 × ki−0.000156 When ki ≧ 0.027, ko ≦ 0.01161 × ki + 0.0008 where: