JP2008039001A - Roller and thrust roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller capable of enhancing bearing functions. <P>SOLUTION: Microscopic indentations are provided in the surface of the roller 11. The surface roughness parameter Ryni of the surface provided with the indentations is in the range of 0.4 to 1.0 μm. A full crowning provided on the outside diameter surface 13 of the roller 11 includes a first crowning 14a, a second crowning 14b and a third crowning 14c. If the length of the roller 11 along the direction of its axis of rolling is not more than twice the radial length of the roller 11, the radius R1 of curvature of the first crowning 14a in a position that is 32% of its length away from the end face 12a of the roller 11 along the axis of rolling is R551 to R1000. The radius R2 of curvature of the second crowning 14b in a position that is 23% of its length away from the end face 12a of the roller 11 along the axis of rolling is R321 to R550. The radius R3 of curvature of the third crowning 14c in a position that is 15% of its length away from the end face 12a of the roller 11 along the axis of rolling is R200 to R320. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a roller and a thrust roller bearing.

When a thrust load is applied to the roller bearing that supports the rotating shaft, a thrust roller bearing is used. Thrust roller bearings used in car air conditioner compressors, automatic transmissions, manual transmissions, hybrid vehicles, etc., have been used harshly, such as high-speed rotation and lean lubrication environment due to recent demands for fuel saving, downsizing, and higher output. Characteristics that can withstand use even in an environment are required. Thrust roller bearings that can withstand harsh usage environments are disclosed in Japanese Patent No. 3604458 (Patent Document 1), Japanese Patent No. 3661133 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2-16821 (Patent Document 3).
Patent 3604458 (paragraph number 0018, FIG. 3) Patent 3661133 (paragraph numbers 0020 to 0021, FIGS. 1 and 2) JP-A-2-168211

  According to Patent Document 1, the thrust roller bearing has a roller and a race (race ring). First and second crownings having different curvatures are provided on the outer peripheral surface of the roller in the rolling axis direction. By doing so, the contact surface pressure is reduced in accordance with the bending of the raceway, and the occurrence of an excessive load is suppressed, thereby stabilizing the bearing function and improving the life. However, the relationship between the length in the radial direction of the roller and the length in the rolling axis direction is unknown, and an optimum crowning cannot be formed according to the size of the roller.

  Here, in the roller included in the thrust needle roller bearing disclosed in Patent Document 2, the ratio of the length in the rolling axis direction to the length in the radial direction of the roller is 1.2 to 2.0. The crowning is provided so that the contact length with the raceway surface is 3/4 or less of the length of the roller in the rolling axis direction. By doing so, the posture of the roller is stabilized and the life is improved.

  However, the crowning provided on the roller is a partial crowning, and there is a portion where no crowning is provided in the direction of the rolling axis of the roller. If it does so, there exists a possibility of producing various malfunctions in the above-mentioned severe use environment.

  Further, according to Patent Document 3, the surface of the roller is subjected to surface treatment, and the parameters relating to the surface roughness are defined, thereby improving the wear resistance of the roller. Specifically, a minute concave recess is provided on the surface of the roller by surface treatment, and the surface roughness parameter RMS (L) in the rotation direction of the surface provided with the recess and the surface roughness in the direction orthogonal thereto. The value of RMS (L) / RMS (C), which is the ratio to the parameter RMS (C), is set to 1.0 or more, and the surface roughness parameter Sk value is specified to be −1.6 or less.

  Here, the surface roughness parameter RMS is a square root of a value obtained by integrating the square of the height deviation from the roughness center line to the roughness curve in the measurement length interval and averaging the integration. Also known as root mean square roughness (ISO4287: 1997). Moreover, it is synonymous with the surface roughness parameter Rqni mentioned later.

  Further, the surface roughness parameter Sk value refers to the degree of distortion (skewness) of the roughness curve (ISO 4287: 1997), and is a statistic of a measure for knowing the asymmetry of the uneven distribution, and is a symmetric distribution such as a Gaussian distribution. In this case, the Sk value is close to 0, and takes a negative value when the concave and convex portions are deleted, and takes a positive value in the opposite case.

  By defining the ratio of the surface roughness parameter RMS and the like in this way, even if the mating surface is a rough surface or a finished surface, the wear resistance of the roller or the like is improved and the life is extended.

  However, in situations where the oil film thickness is extremely thin, such as when low-viscosity oil is used, sufficient wear resistance cannot be ensured, and the life of roller bearings equipped with such rollers can be extended. I can't plan.

  An object of the present invention is to provide a roller capable of improving the bearing function.

  Another object of the present invention is to provide a thrust roller bearing having an improved bearing function.

  The roller according to the present invention is provided with a full crowning on the outer diameter surface. The surface of the roller is provided with a small concave recess, and the surface roughness parameter Ryni (average value of the maximum height for each reference length) of the surface provided with the recess is 0.4 to 1.0 μm. Is within the range. The full crowning includes a first crowning provided in the center of the rolling axis of the roller, a second crowning provided on both end surfaces of the first crowning so as to be continuous with the first crowning, and a second crowning And a third crowning provided on both ends of the second crowning so as to be continuous with the crowning. Here, when the length in the rolling axis direction of the roller is not more than twice the length in the radial direction of the roller, 32% of the length in the rolling axis direction of the roller from both ends of the roller The radius of curvature R1 of the first crowning at the position is R551 to R1000, and the radius of curvature R2 of the second crowning at the position of 23% of the length in the rolling axis direction of the roller from the both end faces of the roller is R321. The radius of curvature R3 of the third crowning at a position 15% of the length in the rolling axis direction of the roller from the both end faces of the roller is R200 to R320. If the length of the roller in the axial direction of the roller is more than twice and less than 3 times the radial length of the roller, the length from the both end faces of the roller in the direction of the axial axis of the roller The radius of curvature R4 of the first crowning at a position of 22% of R2 is R561 to R670, and the radius of curvature of the second crowning at a position of 16% of the length in the rolling axis direction of the roller from both ends of the roller R5 is R421 to R560, and the radius of curvature R6 of the third crowning at the position of 12% of the length in the rolling axis direction of the roller from the both end faces of the roller is R310 to R420.

  Such a roller can appropriately receive a load applied depending on the size. Specifically, depending on the ratio of the length in the radial direction of the rolling axis of the roller, when receiving a relatively small load, the load is received by the first crowning having a large curvature radius. be able to. Further, when the load is relatively large or the bearing mounting seat surface is bent or tilted, the load can be received by the first crowning having a large radius of curvature and the second crowning having a slightly larger radius of curvature. If the load is larger or if the bearing mounting seat has a large deflection or inclination, the load is received by the first crowning with a large radius of curvature, the second crowning with a slightly larger radius of curvature, and the third crowning with a smaller radius of curvature. be able to. If it does so, it can receive a load appropriately by each crowning from which a curvature radius differs with respect to various load conditions.

  In addition, an oil film can be appropriately formed by providing a minute concave recess on the surface of the roller and defining the value of the surface roughness parameter Ryni within the above range. Here, the surface roughness parameter Ryni is the average value of the maximum height for each reference length, that is, the reference curve is extracted from the roughness curve in the direction of the average line, and the peak line and valley line of this extracted part are extracted. Is the value measured in the direction of the vertical magnification of the roughness curve (ISO 4287: 1997).

  As a result, the bearing function can be improved by improving the service life and quietness, reducing the torque, and the like.

  Preferably, the surface roughness parameter Sk value of the surface provided with the depression is −1.6 or less. Furthermore, by defining the surface roughness parameter Sk value in such a range, the concave portion for storing the so-called lubricating oil can be defined in an effective range, the thickness of the formed oil film is ensured, and the oil film is appropriately formed. Can be formed.

  More preferably, the surface roughness parameter Rymax (the maximum value of the maximum height for each reference length) of the surface provided with the recess is in the range of 0.4 to 1.0 μm. The surface roughness parameter Rymax is the maximum value of the maximum height for each reference length (ISO 4287: 1997). By defining the surface roughness parameter Rymax in such a range, an oil film can be formed more appropriately.

  More preferably, the surface roughness parameter Rqni (L) in the rolling axis direction of the roller when the surface roughness of the surface provided with the depression is expressed by a surface roughness parameter Rqni (root mean square roughness). However, Rqni (L) / Rqni (C), which is a ratio to the surface roughness parameter Rqni (C) in the circumferential direction, is 1.0 or less. By defining the value of the surface roughness parameter Rqni within such a range, an oil film can be formed more appropriately.

  More preferably, carbonitriding is performed. By comprising in this way, intensity | strength, toughness, etc. can be improved.

  In another aspect of the present invention, a thrust roller bearing includes any of the rollers described above and supports a thrust load. Such a thrust roller bearing can improve life and quietness, reduce torque, and the like.

  Such a roller can appropriately receive a load applied depending on the size. If it does so, it can receive a load appropriately by each crowning from which a curvature radius differs with respect to various load conditions. In addition, an oil film can be appropriately formed by providing a minute concave recess on the surface of the roller and defining the value of the surface roughness parameter Ryni within the above range. As a result, the life and quietness can be improved and torque can be reduced, and the bearing function can be improved.

  Moreover, according to the thrust roller bearing which concerns on this invention, while improving a lifetime and silence, a torque can also be reduced and a bearing function can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 shows a part of a roller when a roller whose length in the rolling axis direction is not more than twice the length in the radial direction of the roller is cut along a plane including the rolling axis of the roller. It is sectional drawing shown. The length Lw of the roller 11 in the rolling axis direction is not more than twice the length Dw of the roller 11 in the radial direction. That is, it has a relationship of Lw / Dw ≦ 2.

  With reference to FIG. 1, the roller 11 has both end surfaces 12a and 12b located at both ends in the rolling axis direction, and an outer diameter surface 13 serving as a rolling surface. Both end faces 12a and 12b of the roller 11 are F end faces, that is, flat end faces.

  The outer diameter surface 13 is provided with a full crowning. Full crowning refers to a shape in which crowning is provided over the entire area in the rolling axis direction excluding the chamfered portion of the roller 11. The full crowning is a first crowning 14a provided at the center of the roller 11 in the rolling axis direction, and a second crown provided on both end faces 12a and 12b of the first crowning 14a so as to be continuous with the first crowning 14a. And a third crowning 14c provided on both end faces 12a, 12b of the second crowning 14b so as to be continuous with the second crowning 14b. That is, the 1st-3rd crowning 14a-14c is provided so that it may continue smoothly.

  Here, assuming that 32% of the length Lw in the rolling axis direction of the roller is the length L1, the curvature radius R1 of the first crowning 14a at the position L1 from one end face 12a of the roller 11 is R551 to R1000. It is. The same configuration is provided on the other end face 12b side. That is, the first crowning 14a is provided such that the curvature radius R1 at a position of 32% of the length Lw of the roller 11 from both end faces 12a, 12b of the roller 11 is R551 to R1000. Yes.

  Also, assuming that 23% of the length Lw in the rolling axis direction of the roller is the length L2, the radius of curvature R2 of the second crowning 14b at the position L2 from one end face 12a of the roller 11 is R321 to R550. is there. The same configuration is provided on the other end face 12b side. That is, the second crowning 14b is provided so that the curvature radius R2 at a position of 23% of the length Lw in the rolling axis direction of the roller from the both end faces 12a, 12b of the roller 11 is R321 to R550. Yes.

  Further, assuming that 15% of the length Lw in the rolling axis direction of the roller is the length L3, the radius of curvature R3 of the third crowning 14c at the position L3 from one end face 12a of the roller 11 is R200 to R320. is there. The same configuration is provided on the other end face 12b side. That is, the third crowning 14c is provided such that the curvature radius R3 at a position of 15% of the length Lw in the rolling axis direction of the roller from the both end faces 12a, 12b of the roller 11 is R200 to R320. Yes.

  By comprising in this way, the roller 11 can receive the load loaded appropriately. Specifically, when receiving a relatively small load, the load can be received by the first crowning 14a having a large curvature radius R1. Further, when the load is relatively large and the deflection and inclination of the bearing mounting seat surface are small, the load is received by the first crowning 14a having a large curvature radius R1 and the second crowning 14b having a slightly larger curvature radius R2. it can. When the load or the bearing mounting seat surface is greatly deflected or inclined, the first crowning 14a having a large radius of curvature R1, the second crowning 14b having a slightly large radius of curvature R2, and a third crown having a small radius of curvature R3. A load can be received by the crowning 14c. If it does so, a load can be suitably received by the 1st-3rd crowning 14a-14c from which a curvature radius differs with respect to various load conditions.

  Here, the length in the rolling axis direction of the roller 11 from one end surface 12a to the vertex 15 of the outer diameter surface 13 of the roller 11 is a, and the vertex 15 of the outer diameter surface 13 of the roller 11 from the other end surface 12b. If the length of the roller 11 in the rolling axis direction is b, the difference in length | a−b | is 4% or less of the length Lw of the roller in the rolling axis direction. By doing so, the load applied to the roller 11 is distributed almost evenly to the left, right, first, second and third crowning 14a, 14b, 14c provided on both end faces 12a, 12b. Can receive. Therefore, the behavior of the roller 11 can be stabilized.

  Moreover, it is preferable that the roundness of the roller 11 in the part in which the 1st, 2nd and 3rd crowning 14a-14c was provided shall be 1.5 micrometers or less, respectively. Furthermore, the difference in the amount of crowning between the crowning provided on the one end face 12a side and the crowning provided on the other end face 12b side is preferably 1 μm or less. With this configuration, the bearing function can be further improved. The crowning amount refers to a virtual straight line drawn in parallel with the rolling axis of the roller 11 at the apex 15 of the outer diameter surface 13 of the roller 11, and the left and right first to third crowning described above from the virtual straight line. Each of the shortest lengths at positions L1, L2, and L3 from 14a to 14c.

  FIG. 2 shows the roller when the length of the roller in the axial direction of the roller is longer than twice the length in the radial direction of the roller and less than 3 times in the plane including the roller's rolling axis. It is sectional drawing which shows a part, and respond | corresponds to FIG. The length Lw ′ in the rolling axis direction of the roller 16 is longer than twice the length Dw ′ in the radial direction of the roller 16 and less than three times. That is, there is a relationship of 2 <Lw ′ / Dw ′ <3.

  Referring to FIG. 2, similar to the roller 11 described above, the outer diameter surface 18 of the roller 16 is provided with a full crowning. The full crowning is a first crowning 19a provided at the center of the roller 16 in the rolling axis direction, and a second crown provided on both end faces 17a and 17b of the first crowning 19a so as to be continuous with the first crowning 19a. And a third crowning 19c provided on both ends 17a and 17b of the second crowning 19b so as to be continuous with the second crowning 19b. The 1st-3rd crowning 19a-19c is provided so that it may continue smoothly.

  Here, assuming that 22% of the length Lw ′ in the rolling axis direction of the roller is the length L4, the curvature radius R4 of the first crowning 19a at the position of L4 from one end face 17a of the roller 16 is R561 to R561. R670. The same configuration is provided on the other end face 17b side. That is, the first crowning 19a is provided such that the curvature radius R4 at a position of 22% of the length Lw ′ in the rolling axis direction of the roller from the both end faces 17a, 17b of the roller 16 is R561 to R670. ing.

  Further, assuming that 16% of the length Lw ′ in the rolling axis direction of the roller is the length L5, the radius of curvature R5 of the second crowning 19b at the position L5 from one end face 17a of the roller 16 is R421 to R560. It is. The same configuration is provided on the other end face 17b side. That is, the second crowning 19b is provided such that the curvature radius R5 at a position of 16% of the length Lw ′ in the rolling axis direction of the roller from the both end faces 17a, 17b of the roller 16 is R421 to R560. ing.

  Further, assuming that 12% of the length Lw ′ in the rolling axis direction of the roller is the length L6, the curvature radius R6 of the third crowning 19c at the position L6 from one end face 17a of the roller 16 is R310 to R420. It is. The same configuration is provided on the other end face 17b side. That is, the third crowning 19c is provided such that the curvature radius R6 at a position of 12% of the length Lw ′ in the rolling axis direction of the roller from the both end faces 17a, 17b of the roller 16 is R310 to R420. ing.

  By configuring in this way, like the roller 11 described above, the roller 16 whose length in the rolling axial direction of the roller is longer than twice and less than three times the radial length of the roller is Can be appropriately received. If it does so, it can receive a load appropriately with the 1st-3rd crowning 19a-19c from which a curvature radius differs with respect to various load conditions.

  The length in the rolling axis direction of the roller 16 from one end surface 17a to the vertex 20 of the outer diameter surface 18 of the roller 16 is a ', and the vertex 20 of the outer diameter surface 18 of the roller 16 is from the other end surface 17b. If the length of the roller 16 in the rolling axis direction is b ′, the difference | a′−b ′ | is 3% or less of the length Lw ′ of the roller in the rolling axis direction. To do. By doing so, the load applied to the roller 16 can be received evenly distributed to the left and right crowning provided on both end faces 17a, 17b. Therefore, the behavior of the roller 16 can be stabilized.

  Also in this case, similarly, it is preferable that the roundness of the rollers 16 at the portions where the first, second and third crownings 19a to 19c are provided is 1.5 μm or less, respectively. Furthermore, the difference in the amount of crowning between the crowning provided on the one end face 17a side and the crowning provided on the other end face 17b side is preferably 1 μm or less.

  Next, a life test, an acoustic test, and a torque test were performed on the thrust roller bearing including the roller having the above-described configuration and the thrust roller bearing including the conventional roller. Tables 1 and 2 show the configurations of Examples 1 and 2 and Comparative Examples 1-8. Example 1 and Comparative Examples 1 to 4 shown in Table 1 are rollers in which the length of the roller in the rolling axis direction is not more than twice the length of the roller in the radial direction. Further, Example 2 and Comparative Examples 5 to 8 shown in Table 2 are rollers in which the length of the roller in the rolling axis direction is longer than twice and less than 3 times the radial length of the roller. Regarding the following evaluation tests, the bearing size used was such that the inner diameter φ41 mm × the outer diameter φ55.6 mm × when the length in the rolling axis direction of the roller was not more than twice the radial length of the roller. The width (the length in the radial direction of the roller) is 3 mm, and the number of rollers is 32. If the length of the roller in the rolling axis direction is longer than twice the length in the radial direction of the roller and less than 3 times, the inner diameter φ41 mm × outer diameter φ60.4 mm × width (the length of the roller in the radial direction) ) 3 mm and the number of rollers is 32. In the following table, “roller length” indicates “the length of the roller in the rolling axis direction”.

  Next, Table 3 shows the test conditions for the life test, and Tables 4 and 5 show the test results. In addition, about the test result of the life test, it has shown by the life ratio which made the life of Example 1, 2 1.

  Referring to Tables 1 to 5, when Example 1 and Comparative Example 1, and Example 2 and Comparative Example 5 are compared, the life of Comparative Example 1 is 0.71, and the life of Comparative Example 5 is 0.00. In all cases, the lifetime is shortened. The following reasons can be considered for this. In Comparative Examples 1 and 5, as compared with Examples 1 and 2, the position of the apex of the outer diameter surface of the roller is deviated from the center position in the rolling axis direction of the roller, so the behavior of the roller is not stable. If it does so, it will become easy to skew a roller, and the sliding of a roller will arise. Therefore, the oil film is cut, and the contact portion is heated to generate heat, resulting in surface damage and surface-origin peeling.

  When Example 1 and Comparative Example 2 are compared, and Example 2 and Comparative Example 6 are compared, the life of Comparative Example 2 is 0.83 and the life of Comparative Example 6 is 0.88. ing. The following reasons can be considered for this. In Comparative Examples 2 and 6, the roundness of each crowning is larger than those in Examples 1 and 2. When the roundness value of each crowning is large, the rotation of the rollers in the rolling direction becomes unstable. Therefore, the behavior of the rollers is not stable and cannot be rotated smoothly. Moreover, since the part which is contacting locally increases, a contact surface pressure becomes high locally and internal origin type peeling generate | occur | produced.

  When Example 1 and Comparative Example 3 are compared, and Example 2 and Comparative Example 7 are compared, the life of Comparative Example 3 is 0.36, and the life of Comparative Example 7 is 0.29. ing. The following reasons can be considered for this. In Comparative Examples 3 and 7, each crowning R is configured to be smaller than those in Examples 1 and 2. Therefore, the behavior of the rollers becomes unstable, the contact surface pressure increases as a whole, and internal origin type separation occurs.

  When Example 1 and Comparative Example 4 are compared, and Example 2 and Comparative Example 8 are compared, the life of Comparative Example 4 is 0.22, and the life of Comparative Example 8 is 0.14. ing. The following reasons can be considered for this. In Comparative Examples 4 and 8, each crowning R is configured larger than Examples 1 and 2. As a result, the contact surface pressure decreases as a whole, but edge loading occurs. Therefore, the contact surface pressure locally increased, and internal origin type peeling occurred. Also, roller slip is likely to occur due to skew. Therefore, the oil film is cut, and the contact portion is heated to generate heat, resulting in surface damage and surface-origin peeling.

  From the above, Example 1 has a longer life than Comparative Examples 1 to 4, and Example 2 has a longer life than Comparative Examples 5 to 8.

  Next, Table 6 shows the test conditions of the acoustic test, and Tables 7 and 8 show the test results. Moreover, about the test result of an acoustic test, an acoustic value is an average value when the frequency | count of a test is 10 times.

  When comparing Example 1 and Comparative Example 1, Example 2 and Comparative Example 5 with reference to Tables 6 to 8, the acoustic value of Example 1 is 65.2 dBA, whereas Comparative Example The acoustic value of 1 is 72.6 dBA, the acoustic value of Example 2 is 66.0 dBA, whereas the acoustic value of Comparative Example 5 is 72.3 dBA, both of which have high acoustic values. It has become. The following reasons can be considered for this. In Comparative Examples 1 and 5, with respect to Examples 1 and 2, the position of the apex of the outer diameter surface of the roller is deviated from the center position in the rolling axis direction of the roller. Therefore, the roller behavior is not stable.

  When Example 1 and Comparative Example 2 are compared, and Example 2 and Comparative Example 6 are compared, the acoustic value of Comparative Example 2 is 76.2 dBA, the acoustic value of Comparative Example 6 is 77.4 dBA, and both are acoustic values. Is high. The following reasons can be considered for this. In Comparative Examples 2 and 6, the roundness of each crowning is larger than those in Examples 1 and 2. When the roundness value of each crowning is large, the rotation of the rollers in the rolling direction becomes unstable. Therefore, the behavior of the rollers is not stable and cannot be rotated smoothly.

  When Example 1 and Comparative Example 3 are compared with Example 2 and Comparative Example 7, the acoustic value of Comparative Example 3 is 71.9 dBA, the acoustic value of Comparative Example 7 is 71.0 dBA, and both are acoustic values. Is high. The following reasons can be considered for this. In Comparative Examples 3 and 7, each crowning R is configured to be smaller than those in Examples 1 and 2. Therefore, the roller behavior is unstable.

  When Example 1 is compared with Comparative Example 4, Example 2 is compared with Comparative Example 8, the acoustic value of Comparative Example 4 is 65.3 dBA, and the acoustic value of Comparative Example 8 is 66.0 dBA. It is about the same as 1 and 2. The following reasons can be considered for this. In Comparative Examples 4 and 8, each crowning R is configured larger than Examples 1 and 2. Therefore, the roller behavior is stable.

  From the above, the acoustic value of Example 1 is lower than that of Comparative Examples 1 to 3, and the acoustic value of Example 2 is lower than that of Comparative Examples 5 to 7.

  Next, Table 9 shows the test conditions of the torque test, and Tables 10 and 11 show the test results. The test result of the torque test is shown as a rotational torque ratio with the rotational torque of Examples 1 and 2 as 1. Further, as Comparative Example 9, a partial crowning roller in which the length in the rolling axial direction of the roller is not more than twice the radial length of the roller and provided with partial crowning, as Comparative Example 10, A partial crowning roller in which the length in the rolling axis direction is longer than twice and less than 3 times the radial length of the roller and provided with partial crowning is shown.

  Referring to Tables 9 to 11, when comparing Example 1 and Comparative Example 1, Example 2 and Comparative Example 5, the rotational torque of Comparative Example 1 is 1.4, and the rotational torque of Comparative Example 5 is 1.4, and the torque is high in all cases. The following reasons can be considered for this. In Comparative Examples 1 and 5, as compared with Examples 1 and 2, the position of the apex of the outer diameter surface of the roller is deviated from the center position in the rolling axis direction of the roller, so the behavior of the roller is not stable. Therefore, the rollers are likely to skew, and the rollers slip.

  When Example 1 and Comparative Example 2 are compared, and Example 2 and Comparative Example 6 are compared, the rotational torque of Comparative Example 2 is 1.0, and the rotational torque of Comparative Example 6 is 1.0. It is about the same as 1 and 2. The following reasons can be considered for this. In Comparative Examples 2 and 6, the roundness of each crowning is larger than in Examples 1 and 2. When the roundness of each crowning is large, the behavior of the roller is not stable, but the rotation of the roller in the rolling direction becomes unstable, and the roller does not slip.

  When Example 1 and Comparative Example 3 are compared, and Example 2 and Comparative Example 7 are compared, the rotational torque of Comparative Example 3 is 1.1, and the rotational torque of Comparative Example 7 is 1.1. It has become. The following reasons can be considered for this. In Comparative Examples 3 and 7, each crowning R is configured to be smaller than those in Examples 1 and 2. Therefore, the behavior of the roller becomes unstable, and the contact surface pressure increases as a whole, and the elastic hysteresis loss increases.

  When Example 1 and Comparative Example 4 are compared, and Example 2 and Comparative Example 8 are compared, the rotational torque of Comparative Example 4 is 1.7 and the rotational torque of Comparative Example 8 is 1.9, both of which are high in torque. It has become. The following reasons can be considered for this. In Comparative Examples 4 and 8, each crowning R is configured larger than Examples 1 and 2. Accordingly, the roller skew easily causes the roller slip, and the roller slip and the rolling viscous resistance due to the roller slip increase.

  When Example 1 and Comparative Example 9 are compared, and Example 2 and Comparative Example 10 are compared, Comparative Example 9 is 2.5 and Comparative Example 10 is 3.2, both of which have high torque. The following reasons can be considered for this. Comparative Examples 9 and 10 have a longer effective contact length than Examples 1 and 2. Therefore, it is easy to skew and the sliding of the roller is large. In addition, the rolling viscous resistance is high regardless of the stability of the roller behavior.

  From the above, the torque of Example 1 is lower than that of Comparative Examples 1, 3, 4, and 9, and the torque of Example 2 is lower than that of Comparative Examples 5, 7, 8, and 10.

  In addition, wear resistance and the like can be improved by providing a minute concave recess on the surface of the roller. The minute concave recess can be provided by surface treatment such as barrel treatment. The barrel treatment refers to a surface treatment performed by putting a surface treatment and a medium into a barrel and rotating the barrel. The surface treatment state differs depending on barrel treatment conditions, that is, the number of rotations and the rotation time of the barrel, the granularity and amount of the medium to be loaded, and the like. Although the surface roughness of the roller changes due to the surface treatment by the barrel treatment, the surface roughness parameter Ryni, which will be described later, can be set within a specified range by making the barrel treatment conditions special.

  The method for calculating the surface roughness parameters Ryni, Rymax, Sk, Rqni is as follows.

Parameter calculation standard: JIS B0601: 1994 (Surfcom JIS 1994)
Cut-off type: Gaussian
Measurement length: 5λ
Cut-off wavelength: 0.25 mm
Measurement magnification: × 10000
Measurement speed: 0.30 mm / s
Measuring device: Surface roughness measuring device Surfcom 1400A (manufactured by Tokyo Seimitsu Co., Ltd.)
In addition, the area ratio and the average area of the minute concave recess provided by the surface treatment by the barrel treatment were measured by the following method.

  First, the surface of the roller is enlarged and quantified from the image by a commercially available image analysis system. Here, if the surface property inspection method and the surface property inspection device disclosed in Japanese Patent Laid-Open No. 2001-183124 are used, the measurement can be performed with high accuracy. The white portion of the image is analyzed as a flat surface portion, and the black portion is analyzed as a small concave recess.

  The evaluation method is as follows.

Area ratio: Percentage of pixels (black) smaller than the binarization threshold ((bright portion brightness + dark portion brightness) / 2) in the observation visual field range Average area: total / total number of black areas Observation visual field: 826 μm × 620μm (in the case of rollers, if the roller diameter is less than 4, 413μm × 310μm is desirable)
Here, the surface shape of the roller which did not perform surface treatment, the roller which performed conventional surface treatment, and the roller which changed surface treatment conditions was measured. 3 (A) to 3 (C) are diagrams showing the roughness curve of the surface of the roller. When the surface treatment is not performed on the roller (FIG. 3 (A)), the conventional surface treatment is performed. A case where the surface treatment is performed by changing the treatment conditions (FIG. 3B) is shown (FIG. 3B). Table 12 shows that, as Comparative Example 11, the length in the rolling axis direction of the roller was not more than twice the length in the radial direction of the roller, and the above-mentioned full crowning was performed and the surface treatment was not performed. As a comparative example 12, the length of the roller in the rolling axial direction is not more than twice the length of the roller in the radial direction, and the above-described full crowning is performed and the conventional surface treatment is performed. As Example 3, the length of the roller in the rolling axial direction is not more than twice the length of the roller in the radial direction, the above-mentioned full crowning is performed, the processing conditions are changed, and the surface treatment is performed. It is the table | surface which computed the surface roughness parameter Ryni etc.

Oil film parameter Λ: 0.10
FIG. 4 is a graph showing the life results of thrust roller bearings including the rollers shown in Comparative Examples 11 and 12 and Example 3. In FIG. 4, the vertical axis indicates the lifetime (time). Referring to FIG. 4, the life of Comparative Example 11 is 257 hours and the life of Comparative Example 12 is 278 hours, whereas the life of Example 3 is 375 hours, which is significantly longer.

  Therefore, the thrust roller bearing including the roller shown in Example 3 is excellent in wear resistance despite the severe lubrication condition in which the oil film parameter Λ is 0.10 with the lubricant containing PAG oil.

  Moreover, about such a thrust roller bearing, the peeling test which measures a metal contact rate was done. FIG. 5 is a schematic view of a two-cylinder testing machine 51 used for measuring the metal contact ratio. Referring to FIG. 5, a drive side cylinder 52 and a driven side cylinder 53 are attached to one end of each rotary shaft, and the two rotary shafts 54 and 55 are driven by separate motors via pulleys 56 and 57, respectively. It can be done. The rotating shaft 54 on the drive side cylinder 52 side was driven by a motor, and the driven side cylinder 53 was free-rolled to follow the drive side cylinder 52. For the driven cylinder 53, two types of Comparative Example 13 and Example 4 were prepared for the surface treatment.

  Detailed test conditions are shown in Table 13.

  FIG. 6 (A) and FIG. 6 (B) show the test results of the metal contact rate performed under such conditions. FIG. 6A is a diagram showing the metal contact rate and elapsed time in Comparative Example 13. FIG. 6B is a diagram illustrating the metal contact ratio and elapsed time in Example 4. The scales in the vertical direction and the horizontal direction are shown in FIGS. 6 (A) and 6 (B). 6A and 6B, the portion displayed in black in Example 4, that is, the portion in metal contact, is smaller than that in Comparative Example 13. . Specifically, in comparison with Comparative Example 13, Example 4 has an oil film formation rate (= 100% −metal contact rate) of about 10% at the start of operation and 2 at the end of the test (after 2 hours). % Improvement.

  The thrust roller bearing including the roller shown in Example 4 is superior to the thrust roller bearing including the roller shown in Comparative Example 13 in oil film forming ability and rarely causes uneven wear due to metal contact. An oil film can be formed appropriately between the mating surfaces.

  From the above, the above-described first to third crowning is provided on the outer diameter surface, a minute concave recess is provided on the surface, and the surface roughness parameter Ryni and the like are within the above-described range. It is possible to form an oil film and to receive a load appropriately. Therefore, the bearing function can be improved by improving the life and quietness, reducing the torque, and the like.

  In addition, the above-mentioned roller can implement | achieve a long life etc. by performing a carbonitriding process. The rollers are carbonitrided at 840 ° C. for 2 to 3 hours and tempered at 230 ° C., and then the rollers are provided with full crowning as described above. By carrying out like this, the amount of retained austenite in the surface layer (from the surface to 0.05 mm) of a roller can be made into 15%-35% of the whole. Therefore, strength, toughness, etc. can be improved, a long life can be realized, and the bearing function can be further improved.

  In addition, the thing of various structures is applied about the holder | retainer contained in a thrust roller bearing and hold | maintains the above-mentioned roller.

  FIG. 7 is a view of a thrust roller bearing according to an embodiment of the present invention as viewed from the axial direction, including the roller and the cage having the above-described configuration. 8 is a cross-sectional view of the thrust roller bearing shown in FIG. 7 taken along line VIII-O-VIII in FIG. FIG. 9 is an enlarged view of a portion indicated by IX in FIG. FIG. 10 is an enlarged view of a portion indicated by X in FIG.

  7 to 10, the thrust roller bearing 31 includes a plurality of rollers 41 and a cage 21 that holds the plurality of rollers 41. The roller 41 is provided with the above-described configuration, that is, the full crowning including the first, second and third crowning on the outer diameter surface. Further, a minute concave recess is provided on the surface, and the surface roughness parameter Ryni and the like of the roller 41 are as described above. The end surface 42 of the roller 41 is an end surface having an A end surface, that is, a radially central portion that bulges in the rolling axis direction, and whose cross section is configured with a single curvature. 7 to 10, from the viewpoint of easy understanding, the minute concave recess provided on the roller 41 and the full crowning shape of the roller 41 are not shown.

  The cage 21 is composed of a disk-shaped member, and connects the pair of annular portions 23a and 23b so as to form a pair of annular portions 23a and 23b and a pocket 22 for holding the rollers 41. A plurality of pillars 24. A plurality of pockets 22 are provided radially about the rotation axis. Each pocket 22 is provided with a roller stopper 25 for preventing the rollers 41 from falling off. The pocket 22 is provided with a play that allows the rollers 41 to move. The roller 41 can move in the rotational axis direction, the radial direction, and the circumferential direction within the allowable range in the pocket 22, and the amount of play in which the roller 41 can move is determined by the roller stopper 25 and the like.

  Central portions in the radial direction of the plurality of column portions 24 are bent so as to be folded back in the rotation axis direction. Further, the outer peripheral side and inner peripheral side flanges 26a and 26b of the cage 21 are also bent so as to be folded back in the rotation axis direction. The cross sections of the flange portions 26a and 26b and the column portion 24 are substantially W-shaped (see FIG. 8). On the outer peripheral wall surface 27 a of the pocket 22, the outer peripheral flange portion 26 a that is bent in the rotation axis direction as described above is located. In other words, the outer flange portion 26 a bent in the direction of the rotation axis forms a wall surface 27 a on the outer periphery side of the pocket 22.

  The thrust roller bearing having such a configuration has a PV value that is a value obtained by multiplying the contact surface pressure P and the sliding speed V when the outer peripheral end surface 42 of the roller 41 and the outer peripheral wall surface 27a of the pocket 22 come into contact with each other. Therefore, the bearing function can be further improved.

  In the above embodiment, the roller is provided with a minute concave recess by surface treatment by barrel treatment. However, the present invention is not limited to this, and the surface is subjected to surface treatment such as shot or liquid honing treatment. A concave shape may be provided, and the roller surface roughness parameter Ryni may be set to a value within the above-described range.

  Further, the end surface of the roller may be an AR end surface composed of a plurality of curved surfaces having different curvatures, or an R end surface having a substantially R-shaped cross section.

  In the above-described embodiment, the case where the present invention is applied to a thrust roller bearing has been described. However, the present invention is not limited to this and is also applicable to a radial roller bearing.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The roller and thrust roller bearings according to the present invention are improved in bearing function, and therefore require a long life in a severe operating environment such as high-speed rotation and lean lubrication environment. It is effectively used for hybrid vehicles and the like.

A sectional view showing a part of a roller when a roller whose length in the rolling axis direction is not more than twice the length in the radial direction of the roller is cut along a plane including the rolling axis of the roller. is there. A part of a roller when a roller whose length in the rolling axis direction is longer than twice and less than 3 times the radial length of the roller is cut by a plane including the rolling axis of the roller is shown. It is sectional drawing. It is a figure showing the roughness curve of the surface of a roller, (A) The roller without surface treatment, (B) The roller which performed the conventional surface treatment, (C) The roller which performed the surface treatment which changed conditions is shown. It is a graph which shows the lifetime result of the thrust roller bearing containing the roller shown in FIG. It is the schematic showing the 2 cylinder tester which measures a metal contact rate. It is a figure showing the metal contact rate measured with the testing machine shown in FIG. 5, (A) Conventional surface treatment, (B) The surface treatment which changed conditions was given. It is the figure which looked at the thrust roller bearing which concerns on one Embodiment of this invention from the axial direction. It is sectional drawing at the time of cut | disconnecting the thrust roller bearing shown in FIG. 7 by the line VIII-O-VIII in FIG. It is an enlarged view of the part shown by IX in FIG. 7 among the thrust roller bearings shown in FIG. It is an enlarged view of the part shown by X in FIG. 8 among the thrust roller bearings shown in FIG.

Explanation of symbols

  11, 16, 41 roller, 12a, 12b, 17a, 17b, 42 end face, 13, 18 outer diameter surface, 14a, 19a first crowning, 14b, 19b second crowning, 14c, 19c third crowning, 15 , 20 apex, 21 cage, 22 pocket, 23a, 23b annular part, 24 column part, 25 roller stopper, 26a, 26b collar part, 27a, 27b wall surface, 31 thrust roller bearing, 512 cylindrical tester, 52 drive Side cylinder, 53 Driven side cylinder, 54,55 Rotating shaft, 56,57 Pulley.

Claims (6)

It was a roller with full crowning on the outer diameter surface,
The surface of the roller is provided with a small concave recess.
The surface roughness parameter Ryni (average value of maximum height for each reference length) of the surface provided with the indentation is in the range of 0.4 to 1.0 μm,
The full crowning includes a first crowning provided at a center of the roller in a rolling axis direction, and a second crowning provided on both end surfaces of the first crowning so as to be continuous with the first crowning. And a third crowning provided on both end surfaces of the second crowning so as to be continuous with the second crowning,
When the length of the roller in the rolling axis direction is not more than twice the length of the roller in the radial direction, 32% of the length of the roller in the rolling axis direction from both end faces of the roller The radius of curvature R1 of the first crowning at the position of R2 is R551 to R1000, and the curvature of the second crowning at a position of 23% of the length in the rolling axis direction of the roller from both end faces of the roller. The radius R2 is R321 to R550, and the curvature radius R3 of the third crowning at a position 15% of the length in the rolling axis direction of the roller from the both end faces of the roller is R200 to R320.
When the length in the rolling axis direction of the roller is longer than twice and less than 3 times the radial length of the roller, the length in the rolling axis direction of the roller from both end faces of the roller. A radius of curvature R4 of the first crowning at a position of 22% of the length is R561 to R670, and the first radius at a position of 16% of the length in the rolling axis direction of the roller from both end faces of the roller. The radius of curvature R5 of the second crowning is R421 to R560, and the radius of curvature R6 of the third crowning at a position 12% of the length in the rolling axis direction of the roller from the both end faces of the roller is R310. Roll that is ~ R420. The roller according to claim 1, wherein a surface roughness parameter Sk (a degree of distortion of the roughness curve) of a surface provided with the depression is −1.6 or less. The roller according to claim 1 or 2, wherein a surface roughness parameter Rymax (maximum maximum height for each reference length) of the surface provided with the depression is in a range of 0.4 to 1.0 µm. When the surface roughness of the surface provided with the indentation is represented by a surface roughness parameter Rqni (root mean square roughness),
Rqni (L) / Rqni (C), which is the ratio of the surface roughness parameter Rqni (L) in the rolling axis direction of the roller to the surface roughness parameter Rqni (C) in the circumferential direction of the roller, is 1. The roller in any one of Claims 1-3 which is 0 or less. The roller according to any one of claims 1 to 4, wherein carbonitriding is performed. A thrust roller bearing comprising the roller according to claim 1 and supporting a thrust load.

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