JP2018136009A - Tapered roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce torque in a low-revolution range of a tapered roller bearing.SOLUTION: A tapered roller bearing 10 having an inner ring 1, an outer ring 2 and tapered rollers 3 is provided in which at least one of a large rib face 11a of the inner ring 1 and a large-diameter end face 3a of the tapered roller 3 satisfies at least one of the following requirements (a) to (c). (a): An arithmetic average height (Ra) of a roughness curve satisfies 0.002 μm≤Ra≤0.1 μm. (b): A ratio (APH/Rpk) of an actual protrusion crest height (Actual peak height: APH) which is obtained from a load curve of the roughness curve to a protrusion crest average height (Rpk) satisfies 0.5≤APH/Rpk≤2.1. (c): The kurtosis (Rku) of the roughness curve satisfies 7.5≤Rku≤30, and the skewness (Rsk) of the roughness curve satisfies -5≤Rsk≤-1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tapered roller bearing.

  The tapered roller bearing includes an inner ring having a raceway surface on an outer peripheral surface, an outer ring having a raceway surface on an inner peripheral surface, and a plurality of tapered rollers arranged so as to roll between the raceway surface of the inner ring and the raceway surface of the outer ring. Have The tapered roller has a shape in which the tip of the cone is cut by a plane parallel to the bottom surface, and the diameter of the bottom surface is larger than the diameter of the cut surface. That is, the tapered roller has a large-diameter end face (large-diameter end face) and a small-diameter end face (small-diameter end face). A large collar surface that can be brought into contact with the large-diameter end face of the tapered roller and a small collar surface that can be brought into contact with the small-diameter end face are respectively provided on the large collar part and the small collar part of the inner ring.

  During operation of the tapered roller bearing, the large collar surface of the inner ring and the large-diameter end surface of the tapered roller are in sliding contact with each other, so that friction is generated between the contact surfaces. In the low rotation range, most of the torque loss is caused by sliding friction between the large-diameter end surface of the tapered roller and the large collar surface of the inner ring.

  FIG. 8 shows an example of an automobile transfer 100 described as a prior art in Patent Document 1 in which such a tapered roller bearing is used. In the transfer 100, an umbrella pinion shaft 105, a ring gear 106, and a differential (differential) 107 are arranged in a casing (gear box) 101. The umbrella pinion shaft 105 is supported on the casing 101 via two tapered roller bearings 111 and 112 spaced from each other. These tapered roller bearings 111 and 112 are preloaded in the axial direction by a threaded member 110.

  The differential 107 includes a differential case 171, pinion gears (differential gears) 173 that are rotatably supported at both ends of a pinion shaft 172 fixed to the differential case 171, and side gears 174 that mesh with the pinion gears 173. One end of the axle shaft 108 is coupled to each side gear 174, and the other end side of the axle shaft 108 is connected to the driving wheel via a constant velocity joint or the like (not shown).

  An umbrella pinion gear 151 at the tip of the umbrella pinion shaft 105 meshes with the ring gear 106. The ring gear 106 is fixed to the flange portion 171a of the differential case 171. The cylindrical portions 171 b at both ends of the differential case 171 are supported by the casing 101 via a pair of tapered roller bearings 113 and 113. The rotation of the umbrella pinion shaft 105 drives the differential 107 through the umbrella pinion gear 151 and the ring gear 106.

  This transfer 100 has a problem that wear occurs between the end faces of the tapered rollers constituting the tapered roller bearings 111 and 112 that support the umbrella pinion shaft 105 and the edge of the inner ring, thereby generating sliding friction. In Patent Document 1, in order to solve this problem, that is, to reduce torque, at least one of the raceway surface of the inner ring or the outer ring, the rolling surface of the roller, the end surface of the roller, and the flange surface that contacts the end surface of the roller. It is described that the target surface is to satisfy the following requirements.

  The requirement is that a large number of indentations having circular openings having a diameter of 10 μm or more and 50 μm or less are formed at intervals of 10 μm or more and 200 μm or less, and the arithmetic average height (Ra) of the roughness curve indicating the surface roughness is 0. 1 to 0.2 μm, skewness (Rsk) is −1.0 to −0.2, and kurtosis (Rku) is 3 to 7.

  Further, as a surface treatment method for ensuring that the target surface satisfies the above requirements, spherical particles having a Mohs hardness of 6 or more and a diameter of 10 μm or more and 100 μm or less with respect to the surface to be treated (for example, silica particles, alumina) It is described that a shot blasting process for forming irregularities by projecting particles, steel particles) is performed. Further, as the surface treatment method described above, there is also described a method of performing a convex portion removing step of removing a convex portion generated in the shot blast step after performing the shot blast step.

JP 2011-196543 A

  By the way, in the transfer 100 shown in FIG. 8, the pair of tapered roller bearings 113 and 113 that rotatably support the differential 107 on the casing 101 rotate at the same rotational speed as drive wheels (not shown). Accordingly, when the vehicle is traveling in an urban area (signal stop to approximately 60 km / h), the frequency of use in the low rotation range increases. In the low rotation range, as described above, most of the torque loss is caused by sliding friction between the large-diameter end surface of the tapered roller and the large collar surface of the inner ring. For this reason, by reducing this sliding friction, it is possible to reduce the necessary torque in the low rotation range, and it is possible to contribute to higher power transmission efficiency and fuel saving.

  The subject of this invention is reducing the torque of the low rotation area of a tapered roller bearing.

The above object of the present invention is 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 tapered rollers arranged to roll freely between the raceway surface of the inner ring and the raceway surface of the outer ring;
A large collar portion having a large collar surface formed on the inner ring and capable of contacting a large diameter end surface of the tapered roller,
A tapered roller bearing in which at least one of the large flange surface and the large-diameter end surface satisfies at least one of the following requirements (a) to (c), more preferably all.
(A) The arithmetic average height (Ra) of the roughness curve satisfies 0.002 μm ≦ Ra ≦ 0.1 μm.
(B) The ratio (APH / Rpk) of the actual peak height (APH) to the average peak height (Rpk) obtained from the load curve of the roughness curve is 0.5 ≦ APH / Rpk. ≤2.1 is satisfied.
(C) The kurtosis (Rku) of the roughness curve satisfies 7.5 ≦ Rku ≦ 30, and the skewness (Rsk) of the roughness curve satisfies −5 ≦ Rsk ≦ −0.5.
(2) The tapered roller bearing according to (1), wherein the viscosity of the lubricating oil for lubricating the tapered roller bearing or the base oil viscosity of the grease is 50 cSt @ 40 ° C. or less.

  According to the tapered roller bearing of the present invention, at least one of the large collar surface of the inner ring or outer ring and the large-diameter end surface of the tapered roller has a surface roughness parameter in a specific range, so that low rotation The torque in the region can be reduced.

It is sectional drawing which shows a part of tapered roller bearing equivalent to one Embodiment of this invention. It is a graph which shows the roughness curve of the large diameter end surface of the tapered roller of an Example. It is a graph which shows the load curve obtained from the roughness curve of FIG. It is a graph which shows the roughness curve of the large diameter end surface of the tapered roller of a comparative example. It is a graph which shows the load curve obtained from the roughness curve of FIG. It is sectional drawing which shows the vertical type inner ring | wheel rotation type testing machine used by the test done in the Example. It is a graph which shows the result (torque) obtained by the test of the Example. It is a figure which shows an example of the conventional transfer.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to embodiment shown below. In the embodiment described below, a technically preferable limitation is made for carrying out the present invention, but this limitation is not an essential requirement of the present invention. A tapered roller bearing 10 of FIG. 1 includes a plurality of inner rings 1 having a raceway surface 1a on an outer peripheral surface, an outer ring 2 having a raceway surface 2a on an inner peripheral surface, and a plurality of rolls disposed between both raceway surfaces 1a and 2a. The tapered roller 3 and a cage 4 having a pocket 41 for holding the tapered roller 3 one by one. The tapered roller 3 has a large-diameter end surface 3a and a small-diameter end surface 3b.

  A large collar part 11 and a small collar part 12 are formed on both sides of the raceway surface 1a in the axial direction of the outer peripheral surface of the inner ring 1. The large collar portion 11 has a large collar surface 11 a that can come into contact with the large diameter end surface 3 a of the tapered roller 3. The small flange portion 12 has a small flange surface 12 a that can come into contact with the small diameter end surface 3 b of the tapered roller 3.

The large-diameter end surface 3a of the tapered roller 3 satisfies all of the following requirements (a) to (c).
(A) The arithmetic average height (Ra) of the roughness curve satisfies 0.002 μm ≦ Ra ≦ 0.1 μm.
(B) The ratio (APH / Rpk) of the actual peak height (APH) to the average peak height (Rpk) obtained from the load curve of the roughness curve is 0.5 ≦ APH / Rpk. ≤2.1 is satisfied.
The load curve of the roughness curve is defined in JIS B0671-2: 2002 / ISO13565-2: 1966. APH is the height of the actual protruding ridge above the core of the roughness curve, and can be determined from the load curve of the roughness curve. Rpk is the average height of the protruding peaks above the core of the roughness curve.
(C) The kurtosis (Rku) of the roughness curve satisfies 7.5 ≦ Rku ≦ 30, and the skewness (Rsk) of the roughness curve satisfies −5 ≦ Rsk ≦ −0.5.

<About requirement (a)>
The larger the arithmetic average height (Ra), the more easily the surface is worn and seized. Therefore, the arithmetic average height (Ra) of the large-diameter end surface 3a of the tapered roller 3 is preferably small, but if it is too small, the tapered roller 3 The large-diameter end face 3a may be galling, which is disadvantageous in terms of processing cost. When the arithmetic average height (Ra) is in the range of 0.002 μm ≦ Ra ≦ 0.1 μm, it is more advantageous in terms of surface performance and cost than when the arithmetic average height (Ra) is out of this range.

  That is, by satisfying the requirement (a), it is possible to make the large diameter end surface 3a of the tapered roller 3 less susceptible to wear, seizure, and galling. More preferably, 0.005 μm ≦ Ra ≦ 0.06 μm is further advantageous in terms of surface performance and cost.

<Regarding requirement (b)>
In JIS, the “average height Rpk of protruding ridges” is employed as a parameter representing the protruding height above the core portion, not the actual height of the protruding ridges. The reason is considered to be that the average height is used to eliminate the influence of abnormally high protrusions and suppress variation in value. However, the presence of protrusions that are abnormally higher than the surroundings causes direct contact between the solids, causing high friction, seizure, and abnormal wear.

  Therefore, the present inventors have decided to use “APH / Rpk” as a parameter by using “actual protruding peak height APH” which is not defined in JIS. A value close to APH and Rpk indicates that there are no abnormally high protrusions on the surface that adversely affect friction and wear, so APH / Rpk is a parameter indicating the lubrication characteristics of the surface.

  When APH / Rpk exceeds 2.1, it means that there are many abnormally high protrusions (protrusion peaks) that adversely affect friction and wear on the surface. In addition, APH / Rpk never becomes less than 0.5 on a normal surface. That is, it can be said that the surface satisfying 0.5 ≦ APH / Rpk ≦ 2.1 is a surface exhibiting good lubrication characteristics.

  Therefore, by satisfying the requirement (b), the lubricity between the large-diameter end surface 3a of the tapered roller 3 and the large collar surface 11a of the inner ring 1 is improved, and high friction, seizure, and abnormal wear are suppressed. I can expect. That is, adopting APH / Rpk as a parameter and specifying the range contributes to the realization of low torque. Moreover, it is more preferable that it is in the range of 0.5 ≦ APH / Rpk ≦ 2.0.

<About requirement (c)>
Rku is a parameter representing the degree of sharpness of the surface height distribution, and the value of Rku increases when there are sharp peaks and valleys. Since the surface satisfying the requirement (b) does not have an abnormally high protrusion (protruding peak), a large value of Rku indicates that a protruding valley exists. This valley portion serves as a reservoir (oil reservoir) for supplying the lubricant to the contact surface.

  When the value of Rku is small, it is difficult to sufficiently lubricate the contact surface because the number of protruding troughs serving as oil reservoirs is small. On the other hand, when the value of Rku is too large, the sharpness of the protruding valley is large and the width of the valley is narrow, so that it is difficult to hold a sufficient amount of lubricant. The surface satisfying 7.5 ≦ Rku ≦ 30 is a surface having an appropriate number of oil reservoirs and valleys with sharpness. More preferably, if it is 8 ≦ Rku ≦ 15, the surface having the optimum valley portion is obtained.

  Rsk is a parameter that represents the symmetry between the peak and valley when the average line is the center, and the value of Rsk increases when there are many protruding peaks, and Rsk when there are many protruding valleys. The value of becomes smaller. The smaller the protruding ridges, the more direct contact between the solids can be prevented. Therefore, in order to improve the surface lubrication characteristics, the value of Rsk is preferably small. However, there is a lower limit on the value of Rsk on a realistic surface, and −5 ≦ Rsk ≦ −0.5 is an appropriate range. More preferably, −3 ≦ Rsk ≦ −0.9.

  Therefore, by satisfying both the requirement (b) and the requirement (c), the large-diameter end surface 3a of the tapered roller 3 and the inner ring 1 are compared with the case where the requirement (b) is satisfied but the requirement (c) is not satisfied. The lubricity with the large collar surface 11a is improved.

  As can be seen from the above description, according to the tapered roller bearing 10 of this embodiment, the large-diameter end surface 3a of the tapered roller 3 is a surface that satisfies all of the requirements (a) to (c), thereby reducing the low rotational speed range. Torque can be reduced.

  Further, when the viscosity of the lubricating oil for lubricating the tapered roller bearing is lowered to 50 cSt @ 40 ° C. or less, the stirring resistance of the lubricating oil is lowered and the torque is reduced. However, in such a case, it is difficult to maintain good lubrication, and surface damage such as seizure and wear may occur. However, when the surface satisfies all the requirements (a) to (c), a low torque can be maintained even under low viscosity lubrication such that the viscosity of the lubricating oil is 50 cSt @ 40 ° C. or less.

  In the case of the tapered roller 3 in which a general heat treatment is applied to a material composed of two types of high carbon chromium bearing steel (SUJ2), only the large-diameter end surface 3a is a surface that satisfies all the requirements (a) to (c). Examples of the method include the following methods. One example is polishing the large-diameter end surface 3a with a coarse-grained grindstone to form relatively large irregularities on the surface of the large-diameter end surface 3a, and then polishing with a fine-grained grindstone to remove the convex portions on the surface. It is a method to do. In another example, the large-diameter end surface 3a is ground with a coarse grindstone to form relatively large irregularities on the surface of the large-diameter end surface 3a, and then shot peening, barrel processing, lapping or buffing is performed. In this method, the process of removing the convex portions on the surface is performed.

In the above embodiment, only the large-diameter end surface 3a of the tapered roller 3 is a surface that satisfies all the requirements (a) to (c). However, in the case of the tapered roller bearing 10 of FIG. Only the large ridge surface 11a may be a surface satisfying all the requirements (a) to (c), or both may be a surface satisfying all the requirements (1) to (3).
Further, a collar may be provided on the outer ring instead of the inner ring (not shown). In this case, at least one of the small-diameter end surface 3b of the tapered roller 3 and the flange portion that can come into contact with the small-diameter end surface of the tapered roller formed on the outer ring, or both surfaces are surfaces satisfying all the requirements (a) to (c). Also good.

  As the tapered roller bearing 10 having the structure of FIG. 1, a tapered roller bearing having a nominal number HR32008XJ (bearing inner diameter: 40 mm, bearing outer diameter: 68 mm, maximum width: 19 mm) was produced for testing.

  The inner ring 1, the outer ring 2, and the tapered roller 3 were produced as follows. First, after the raw material which consists of SUJ2 was processed into each shape, oil quenching and tempering were performed. Thereby, the hardness of the inner ring 1, the outer ring 2, and the tapered roller 3 was made to be in the range of HRC58 to 64 (Hv650 to 800). In addition to the large-diameter end surface 3a of the tapered roller 3, normal grinding and finishing processes were performed.

  Next, in Samples 1 to 6 (Examples 1 to 6), only the large-diameter end surface 3a of the tapered roller 3 is ground with a coarse grindstone, thereby forming irregularities on the surface of the large-diameter end surface 3a. The process of removing the convex part of the surface was performed by polishing or buffing with a fine grindstone. FIG. 2 shows an example of a roughness curve (measured based on JIS B0601: 2001) of the large-diameter end face 3a. Ra, APH, Rpk, Rku, and Rsk were obtained from this roughness curve and the load curve shown in FIG. 3 obtained based on JIS B0671-2: 2002 from this roughness curve. In addition, APH / Rpk was calculated.

  In Samples 7 to 9 (Comparative Examples 1 to 3), only the large-diameter end surface 3a of the tapered roller 3 is ground with a fine grindstone to form irregularities on the surface of the large-diameter end surface 3a. The process of removing is not performed. FIG. 4 shows an example of a roughness curve (measured based on JIS B0601: 2001) of the large-diameter end face 3a. Ra, APH, Rpk, Rku, Rsk, and RSm were obtained from this roughness curve and the load curve shown in FIG. 5 obtained from this roughness curve based on JIS B0671-2: 2002. In addition, APH / Rpk was calculated.

  For measurement, a non-contact type measuring device (CCI MP-HS) manufactured by Taylor Hobson was used. A Kaussian filter (filter size 0.08 mm) was used when measuring Ra, Rku, and Rsk, and a double Gaussian filter (filter size 0.08 mm) was used when measuring APH and Rpk.

  Using the inner ring 1, the outer ring 2, and the tapered rollers 3 of the samples 1 to 9 obtained as described above, and the cage cage 4 made of SPCC, the tapered roller bearing 10 of the example and the comparative example is assembled. A rotation test was performed using the apparatus shown in FIG. The apparatus shown in FIG. 6 is a vertical inner ring rotating tester, and includes a main shaft 21, a support bearing 22 that rotatably supports the main shaft 21, a main body portion 23, and a hydrostatic bearing 24. The hydrostatic bearing 24 is provided on the upper end surface in the axial direction of the main body 23. This testing machine is used by fitting the inner ring 1 of the tapered roller bearing 10 as a test bearing to the axial end portion 21 a of the main shaft 21 and the outer ring 2 to the main body 23.

  An axial load Fa can be applied from above the hydrostatic bearing 24. A load cell 26 is connected to the side surface of the main body 23 via a bar 25. A dynamic friction torque applied to the main body 23 can be detected by the load cell 26. A passage 27 for supplying lubricating oil J to the inside of the test bearing is formed in the main body portion 23. The passage 27 is open on the side surface of the main body 23. A thermocouple 28 for measuring the temperature of the test bearing is also provided.

To this apparatus, the tapered roller bearings 10 of the example and the comparative example were respectively attached as test bearings, and while supplying mineral oil (viscosity grade: ISO VG32) at a temperature of 58 ° C. ± 1 ° C. at a supply rate of 1000 ml / min, Fa The torque was measured by rotating the inner ring 1 under the conditions of = 4 kN and a rotational speed of 250 min ⁻¹ . Further, the torque ratio with the measured torque value of the tapered roller bearing of Comparative Example 1 as “1” was calculated.

  These results are shown in Table 1. The surface roughness parameter of the large-diameter end face of the tapered roller in Table 1 is an average value of the tapered rollers assembled to the tapered roller bearing. In the case of HR32008XJ, there are 22 tapered rollers. The 22 tapered roller large-diameter end faces were measured, and the average value is shown in Table 1. The torque ratio is shown in a graph in FIG.

  From this result, the following can be understood. Only the difference in surface roughness of the large-diameter end surface 3a of the tapered roller 3 causes a difference in torque in the low rotation region of the tapered roller bearing 10. Ra of the large-diameter end face 3a is 0.002 μm ≦ Ra ≦ 0.1 μm, APH / Rpk is 0.5 ≦ APH / Rpk ≦ 2.1, Rku is 7.5 ≦ Rku ≦ 30, Rsk In the tapered roller bearing of the example in which −5 ≦ Rsk ≦ −0.5, the torque in the low rotation region can be reduced compared to the tapered roller bearing of the comparative example.

  The application of the present invention is not limited to the transfer exemplified as the conventional example, and can be appropriately changed without departing from the gist of the present invention. For example, it can be used for applications that require torque reduction in a low rotation range such as for transmissions.

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Inner ring raceway surface 11 Large collar part 12 Small collar part 11a Large collar surface 12a Small collar surface 2 Outer ring 2a Outer ring raceway surface 3 Tapered roller 3a Large diameter end surface 3b Small diameter end surface 4 Cage 10 Conical roller bearing

Claims (3)

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 tapered rollers arranged to roll freely between the raceway surface of the inner ring and the raceway surface of the outer ring;
A large collar portion having a large collar surface formed on the inner ring and in contact with a large diameter end surface of the tapered roller,
A tapered roller bearing in which at least one of the large flange surface and the large-diameter end surface satisfies at least one of the following requirements (a) to (c).
(A) The arithmetic average height (Ra) of the roughness curve satisfies 0.002 μm ≦ Ra ≦ 0.1 μm.
(B) The ratio (APH / Rpk) of the actual peak height (APH) to the average peak height (Rpk) obtained from the load curve of the roughness curve is 0.5 ≦ APH / Rpk. ≤2.1 is satisfied.
(C) The kurtosis (Rku) of the roughness curve satisfies 7.5 ≦ Rku ≦ 30, and the skewness (Rsk) of the roughness curve satisfies −5 ≦ Rsk ≦ −0.5. 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 tapered rollers arranged to roll freely between the raceway surface of the inner ring and the raceway surface of the outer ring;
A large collar portion having a large collar surface formed on the inner ring and in contact with a large diameter end surface of the tapered roller,
A tapered roller bearing in which at least one of the large collar surface and the large-diameter end surface satisfies all of the following requirements (a) to (c).
(A) The arithmetic average height (Ra) of the roughness curve satisfies 0.002 μm ≦ Ra ≦ 0.1 μm.
(B) The ratio (APH / Rpk) of the actual peak height (APH) to the average peak height (Rpk) obtained from the load curve of the roughness curve is 0.5 ≦ APH / Rpk. ≤2.1 is satisfied.
(C) The kurtosis (Rku) of the roughness curve satisfies 7.5 ≦ Rku ≦ 30, and the skewness (Rsk) of the roughness curve satisfies −5 ≦ Rsk ≦ −0.5. The tapered roller bearing according to claim 2, wherein the viscosity of the lubricating oil for lubricating the tapered roller bearing or the base oil viscosity of the grease is 50 cSt @ 40 ° C or less.

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