JP2015094402A - Roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roller bearing the wear resistance and seizure resistance of which can be improved by improving lubricity even under severe use conditions.SOLUTION: A roller bearing 10 comprises an inner ring 11 having a raceway surface 11a on the outer peripheral face thereof, an outer ring 12 having a raceway surface 12a on the inner peripheral face thereof, and a plurality of rollers 13 rollably provided between the raceway surfaces of the inner ring and the outer ring and having rolling surfaces 13a on the outer peripheral faces thereof. A plurality of groove portions having a length in the circumferential direction are intermittently formed on at least any of the raceway surface of the inner ring, the raceway surface of the outer ring, and the rolling contact surfaces of the rollers. When a surface roughness of the surface in which the groove portions are formed, is axially measured, a depth Rvk of a projection valley portion and a height Rpk of a projection peak portion satisfies 4.1≤Rvk/Rpk≤7.2.

Description

  The present invention relates to a roller bearing.

  The processing technology using machine tools is becoming more and more sophisticated year by year, and accordingly, the use conditions of bearings in these machine tools have become severe. Conventionally, in a bearing used in a harsh environment, various techniques for improving lubricity by providing a predetermined surface shape on a contact surface have been proposed (see, for example, Patent Document 1 and Patent Document 2). .

  In the technique proposed in Patent Document 1, in order to prevent damage such as peeling or peeling of the rolling surface under trace oil or depletion lubrication, the roller rolling surface is provided with a minute dent and contact. The part is finished smoothly. Further, on the rolling surface, the square root height Rq (μm) of the contour curve, the maximum peak height Rp (μm) of the contour curve, the protruding valley depth Rvk (μm), the maximum valley depth Rv (μm), It is determined that the average value calculated for each reference length satisfies Rvk ≧ 0.3, Rp / Rq ≦ 1.4, and Rv / Rp ≧ 3.8, and suppresses the protruding portion of the contact portion and improves smoothness. ing. Furthermore, in the technique proposed in Patent Document 1, it is determined that the average length RSm (μm) of the contour curve elements satisfies RSm ≧ 30, and the contact surfaces other than the oil sump valleys are smoothed.

  The technique proposed in Patent Document 2 aims at high oil film forming ability in a severe lubricating environment, and randomly and innumerably forms indentations of minute concave shapes on the rolling element surface. The surface roughness parameter Ryni of the surface provided with the depression satisfies 0.4 μm ≦ Ryni ≦ 1.0 μm, and the Sk value indicating the degree of distortion from the average line satisfies Sk ≦ −1.6, and the axial surface The value of the ratio between the roughness Rqni (L) and the circumferential surface roughness Rqni (C) satisfies Rqni (L) / Rqni (C) ≦ 1.0.

JP 2004-183783 A JP 2008-39142 A

  By the way, in recent years, a machine tool is often used under a rapid acceleration / deceleration operation condition that accelerates to several tens of thousands of revolutions within one second from a stationary state and returns to a stationary state in several seconds again. Therefore, it is desired to further improve the lubrication performance of the bearing.

  However, the square root height Rq of the contour curve used in Patent Document 1 is a value greatly influenced by a deep flaw. Therefore, even if the contact surface is not sufficiently smooth, if the dent is sufficiently deep, Rp / Rq ≦ 1.4 may be satisfied, and smoothness may not be guaranteed.

  In addition, the Sk value used in the above-mentioned Patent Document 2 is a value indicating how large the unevenness is with respect to the average line, and other roughness parameters do not distinguish between the contact surface and the indentation. Is the averaged value. For this reason, the standard regarding the smoothness of the contact surface cannot be said to be sufficient, and it may be insufficient to determine a surface shape having an excellent lubricating effect.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a roller bearing capable of improving wear resistance and seizure resistance by improving lubricity even under severe use conditions. And

The above object of the present invention can be achieved by the following constitution.
(1) an inner ring having a raceway surface on the outer peripheral surface;
An outer ring having a raceway surface on the inner peripheral surface;
A plurality of rollers provided in a freely rollable manner between the raceways of the inner ring and the outer ring, and having a rolling surface on the outer peripheral surface;
A roller bearing comprising:
At least one of the raceway surface of the inner ring, the raceway surface of the outer ring, and the rolling surface of the roller, a plurality of grooves having a length in the circumferential direction are intermittently formed,
When the surface roughness of the surface on which the groove is formed is measured in the axial direction, the roller valley depth Rvk and the protrusion peak height Rpk satisfy 4.1 ≦ Rvk / Rpk ≦ 7.2. .
(2) When the concave portion having a depth from the average line of the surface roughness of −1.0 μm or more is the groove portion, and the opening of the groove portion in the average line is the groove width,
The roller bearing according to (1), wherein a ratio of the groove width to the evaluation length is 4.2% or more and 17.3% or less.

  According to the roller bearing of the present invention, by specifying the surface shape of the contact surface with each parameter, it is possible to improve wear resistance and seizure resistance by improving lubricity even under severe use conditions. It is.

It is sectional drawing of the roller bearing which concerns on one Embodiment of this invention. It is a figure for demonstrating the groove part and groove width in this embodiment. (A)-(d) shows the test piece of Examples 1-4, (e) (f) shows the surface shape of the test piece of Comparative Examples 1 and 2, respectively. It is an evaluation result of the seizing time of the test pieces of Examples 1 to 4 and Comparative Examples 1 and 2. It is a graph which shows the relationship between Rvk / Rpk and image sticking time.

  Hereinafter, a roller bearing according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the roller bearing 10 according to the present embodiment is a cylindrical roller bearing in which a plurality of cylindrical rollers 13 are arranged between an inner ring 11 and an outer ring 12. Each roller 13 is held by a cage 14 in which a plurality of pockets (not shown) are formed at equal intervals in the circumferential direction so that the circumferential interval is constant.

  An inner ring raceway surface 11 a is provided on the outer peripheral surface of the inner ring 11, and an outer ring raceway surface 12 a is provided on the inner peripheral surface of the outer ring 12. The plurality of rollers 13 having a rolling surface 13a which is a cylindrical surface on the outer peripheral surface rolls between the inner ring raceway surface 11a and the outer ring raceway surface 12a.

  In the present embodiment, in order to improve the lubrication performance, the surfaces of the members constituting the roller bearing 10 are in contact with each other, that is, the surface shape of at least one of the inner ring raceway surface 11a, the outer ring raceway surface 12a, and the rolling surface 13a. Is specified. Hereinafter, these inner ring raceway surface 11a, outer ring raceway surface 12a, and rolling surface 13a are also referred to as contact surfaces. More specifically, at least one of these contact surfaces has a length in the circumferential direction and intermittently forms a plurality of grooves that can hold the lubricant, and using the roughness parameter or the like, The shape of the groove and the shape of the contact surface other than the groove are defined.

  Here, the roughness shape of the contact surface is measured in the axial direction using a contact-type roughness measuring machine. Here, the roughness parameter obtained from the roughness shape measured in the axial direction is used, where the cutoff value λc is 0.25 (mm) and the measurement length is 5λc.

  As shown in FIG. 2, in this embodiment, a recess having a depth of −0.1 μm or more from the average line of the surface roughness measured in the axial direction is defined as a groove, and a recess smaller than that is regarded as a groove. Make it not exist. If a groove having a depth from the average line of −0.1 μm or more is formed on the contact surface, it can be expected to improve lubricity. Further, the axial opening of the groove portion on the average line is defined as a groove width v.

  The following conditions A to D are defined as the surface shape of the contact surface having wear resistance and seizure resistance due to improvement in lubricity. Here, based on JIS B 0671-2: 2002, Rpk indicates the protruding peak height, Rvk indicates the protruding valley depth, and Rk indicates the effective load roughness. In addition, n is the number (grooves) of groove portions per evaluation length of 1 mm, and (v / l) is the ratio (%) of the groove width per evaluation length of 1 mm.

Condition A: 4.1 ≦ Rvk / Rpk ≦ 7.2
Condition B: 0.075 ≦ Rk ≦ 0.089
Condition C: 3.5 ≦ n ≦ 6.4
Condition D: 4.2 ≦ (v / l) ≦ 17.3

  In the roller bearing of the present embodiment, since at least one of the inner ring raceway surface 11a, the outer ring raceway surface 12a, and the rolling surface 13a satisfies the condition A, there is no peak portion protruding on the contact surface. Smoothness of portions other than can be ensured, and damage due to load can be suppressed. Moreover, when the condition A is satisfied, the number of grooves on the contact surface can be sufficiently increased. As a result, the groove portion can hold a sufficient amount of lubricant, and the lubricant can be supplied to the contact surface, so that the lubricating performance can be improved. In the condition A, it is more preferable that 4.1 ≦ Rvk / Rpk ≦ 5.6 is satisfied.

  Further, when the condition D is satisfied, the ratio of the groove portion in the surface area of the contact surface is in an appropriate range. Further, when the condition D is satisfied, the groove portion has a sufficient volume for holding the lubricant and has a sufficient opening for discharging the lubricant, so that the lubricating performance can be improved. Therefore, in the roller bearing of the present embodiment, it is preferable that any one of the contact surfaces satisfies the condition D in addition to the condition A.

  The effective load roughness Rk indicates the height excluding protruding peaks and protruding valleys in the surface roughness shape. Therefore, when the condition B is satisfied, the portion of the contact surface excluding the groove, that is, the surface responsible for the load becomes sufficiently smooth, and damage due to the load can be suppressed. Further, when the condition C is satisfied, the ratio of the groove portion in the surface area of the contact surface is in an appropriate range. Therefore, in the roller bearing of the present embodiment, it is more preferable that any one of the contact surfaces satisfies the conditions B and C in addition to the conditions A and D.

  By using these conditions A, B, C, and D, the groove portion for holding and supplying the lubricant and the load are handled in at least one of the inner ring raceway surface 11a, the outer ring raceway surface 12a, and the rolling surface 13a. The shape and roughness of the surface can be determined appropriately. Thereby, the roller bearing 10 of this embodiment can obtain the wear resistance effect and seizure resistance effect due to the improved lubricity.

  Here, in order to demonstrate the effect of the roller bearing 10 according to the present invention, the wear resistance effect and seizure resistance effect by applying the surface shape defined in the present invention to the contact surface were confirmed using a two-cylinder testing machine. .

  A surface shape that satisfies the above conditions (Example) or a surface shape that does not satisfy the above conditions (Comparative Example) is imparted to one of the test pieces simulating the inner ring raceway surface and the roller rolling surface. The test pieces of the examples were produced by super-finishing or lapping the ground surface using a rough grindstone. Here, since grinding is performed along the circumferential direction, a groove having a length in the circumferential direction is formed. Further, intermittent grooves are formed by the movement of the grinding wheel contact surface and the removal of the abrasive grains. Moreover, the test piece of the comparative example was produced by grinding finishing. A pair of test pieces is provided with a ground surface having an arithmetic average roughness Ra (μm) of about 0.05.

  The two-cylinder test was carried out at a sliding speed and a sliding rate simulating an actual cylindrical roller bearing. The load was the same as the actual machine, and the test was performed in a depleted lubrication state where grease was thinly applied as a lubricant to the surface of the test piece, and the effect was confirmed with the time until the test machine stopped due to torque increase as the seizure time.

  Table 1 and FIG. 3 show the measurement results of the roughness of the test pieces of Examples 1 to 4 and Comparative Examples 1 and 2. The values of arithmetic average roughness Ra, effective load roughness Rk, number of grooves n, and v / l shown in Table 1 are the average values of the measurement results of each test piece, and Rvk / Rpk is the average of the measurement results. Value. Table 1 also shows the ratio (%) at which each Rvk / Rpk measurement result is 3.5 to 10.

  4 and 5 show the results of comparing the seizure times of the test pieces obtained in the test. In Examples 1 to 4 that satisfy the above-described conditions, the seizure time was 3 to 4 times that of Comparative Examples 1 and 2 that did not satisfy Conditions A and D. Furthermore, even in the range of Condition B, it was found that the seizure time of Examples 1 and 2 having a relatively large number of grooves was 5 to 10 times that of Comparative Examples 1 and 2. Moreover, it was found from FIG. 5 that when 4.1 ≦ Rvk / Rpk ≦ 5.6 is satisfied, the seizing time is further increased. In addition, in the outer ring raceway surface, the inner ring raceway surface, and the roller rolling surface that do not satisfy the condition A, the life is further improved by setting the surface roughness Ra (μm) to 0.01 ≦ Ra ≦ 0.10. be able to. Further, by setting the ratio of 3.5 to 10 in each measurement result of Rvk / Rpk to 63 to 100%, variation in the number of grooves can be reduced, and the life can be further improved.

  From the above results, it can be seen that according to the roller bearing of the present invention, it is possible to improve wear resistance and seizure resistance by improving lubricity.

  In addition, this invention is not limited to embodiment mentioned above, A change, improvement, etc. are possible suitably. In the above-described embodiment, a cylindrical roller bearing is exemplified as the roller bearing, but the present invention can also be applied to other roller bearings. Further, as in the above embodiment, when a groove having a length in the circumferential direction is formed on either the raceway surface of the inner ring or the rolling surface of the roller, the wear resistance effect and the seizure resistance effect are obtained. Although it can improve especially, it is not limited to this. In the present invention, if a plurality of grooves having a length in the circumferential direction are intermittently formed on at least one of the raceway surface of the inner ring, the raceway surface of the outer ring, and the rolling surface of the roller, the wear resistance / It is possible to improve seizure resistance.

DESCRIPTION OF SYMBOLS 10 Roller bearing 11 Inner ring 11a Inner ring raceway surface 12 Outer ring 12a Outer ring raceway surface 13 Roller 13a Rolling surface 14 Cage

Claims (2)

An inner ring having a raceway surface on the outer peripheral surface;
An outer ring having a raceway surface on the inner peripheral surface;
A plurality of rollers provided in a freely rollable manner between the raceways of the inner ring and the outer ring, and having a rolling surface on the outer peripheral surface;
A roller bearing comprising:
At least one of the raceway surface of the inner ring, the raceway surface of the outer ring, and the rolling surface of the roller, a plurality of grooves having a length in the circumferential direction are intermittently formed,
When the surface roughness of the surface on which the groove is formed is measured in the axial direction, the roller valley depth Rvk and the protrusion peak height Rpk satisfy 4.1 ≦ Rvk / Rpk ≦ 7.2. . When the concave portion whose depth from the average line of the surface roughness is −1.0 μm or more is the groove portion, and the opening of the groove portion in the average line is the groove width,
The roller bearing according to claim 1, wherein a ratio of the groove width to the evaluation length is 4.2% or more and 17.3% or less.

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