JP2006022824A - Tapered roller bearing for differential - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a load capacity without lowering the rigidity of a cage. <P>SOLUTION: This tapered roller bearing 1 for a differential comprises an inner ring 2, an outer ring 3, a plurality of tapered rollers 4 rollingly disposed between the inner ring 2 and the outer ring 3, and the cage 5 holding the tapered rollers 4 at prescribed intervals in the circumferential direction. A roller factor γ is increased more than 0.94, where γ is (roller quantity x averaged roller diameter)/(π x PCD). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tapered roller bearing for an automobile differential.

  FIG. 7 illustrates a typical automobile differential. The top of the figure is the front of the vehicle body and the bottom is the rear of the vehicle body. A drive pinion shaft 42 is accommodated in the front portion of the differential case 41 and is rotatably supported by a pair of tapered roller bearings 44 and 45. A propeller shaft (not shown) is connected to the front end portion of the drive pinion shaft 42, and a drive pinion gear (reduction small gear) 43 that meshes with a link gear (reduction large gear) 46 is fixed or integrally provided to the rear end portion. It is.

  The link gear 46 is connected to a differential gear case 47, and the differential gear case 47 is rotatably supported with respect to the differential case 41 by a pair of tapered roller bearings 48 and 49. Inside the differential gear case 47, a pair of pinion gears 50 and a pair of side gears 51 that mesh with the pinion gears 50 are disposed. The pinion gear 50 is fixed to the pinion shaft 52, and the side gear 51 is attached to the differential gear case 47 through a thrust washer. Left and right drive shafts (not shown) are connected to the inner diameter portions of the side gears 51 corresponding to the drive shafts (serration connection or the like).

  The drive torque of the propeller shaft is transmitted through a path of drive pinion gear 43 → link gear 46 → differential gear case 47 → pinion gear 50 → side gear 51 → drive shaft. On the other hand, the driving resistance of the tire is transmitted from the drive shaft → the side gear 51 → the pinion gear 50.

  By the way, in recent years, low-viscosity oils tend to be used for automobile differentials in order to reduce fuel consumption. In an environment where low-viscosity oil is used, bearing lubrication is poor when adverse conditions such as (1) high oil temperature, (2) low oil volume, and (3) preload loss occur. Due to the extremely short life, surface-origin separation may occur on the inner ring raceway surface with high surface pressure.

  As a countermeasure for short life due to this surface-origin separation, reduction of the maximum surface pressure is a direct and effective solution. In order to reduce the maximum surface pressure, the bearing dimensions are changed, or if the bearing dimensions are not changed, the number of rollers of the bearing is increased. In order to increase the number of rollers without reducing the roller diameter, the pocket interval of the cage must be narrowed. For this purpose, it is necessary to enlarge the pitch circle of the cage and bring it closer to the outer ring side as much as possible.

As an example in which the cage is brought into contact with the inner surface of the outer ring, there is a tapered roller bearing shown in FIG. 8 (see Patent Document 1). The tapered roller bearing 61 guides the cage 62 by sliding the outer peripheral surface of the small-diameter side annular portion 62 a and the outer peripheral surface of the large-diameter side annular portion 62 b with the inner surface of the outer ring 63. In order to suppress drag torque on the outer diameter surface of the portion 62c, a recess 64 is formed to maintain a non-contact state between the outer diameter surface of the column portion 62c and the raceway surface 63a of the outer ring 63. The retainer 62 includes a plurality of small-diameter-side annular portions 62a, large-diameter-side annular portions 62b, small-diameter-side annular portions 62a, and large-diameter-side annular portions 62b that are axially connected to each other so that a recess 64 is formed on the outer diameter surface. Column part 62c. A plurality of pockets are provided between the column portions 62c for accommodating the tapered rollers 65 in a rollable manner. The small-diameter-side annular portion 62a is provided with a collar portion 62d that extends integrally on the inner-diameter side. The tapered roller bearing of FIG. 8 is intended to improve the strength of the cage 62, and is an example in which the cage 62 is brought into contact with the inner diameter surface of the outer ring 63 in order to increase the circumferential width of the column portion 62c of the cage 62. It is.
JP 2003-28165 A

  In the tapered roller bearing 61 described in Patent Document 1, the circumferential width of the column portion 62 c of the cage 62 is increased by moving the cage 62 toward the outside diameter until it comes into contact with the inside diameter surface of the outer ring 63. Further, since the recesses 64 are provided in the column portion 62c of the cage 62, the plate thickness is inevitably thinned, the rigidity of the cage 62 is reduced, and the cage 62 is deformed by the stress when the bearing 61 is assembled. There is also a possibility that the cage 62 is deformed while the bearing 61 is rotating.

  On the other hand, a conventional typical tapered roller bearing with a cage other than the tapered roller bearing described in Patent Document 1 avoids contact between the outer ring 71 and the cage 72 as shown in FIG. In order to secure the width and to obtain the appropriate column strength and smooth rotation of the cage 72, the roller coefficient γ (roller filling rate) defined by the following equation is usually designed to be 0.94 or less. .

Roller coefficient γ = (Z · DA) / (π · PCD)
Here, Z: number of rollers, DA: roller average diameter, PCD: roller pitch circle diameter.

  In FIG. 9, reference numeral 73 is a tapered roller, 74 is a column surface, 75 is an inner ring, and θ is a window angle.

  An object of the present invention is to prevent premature breakage due to an increase in load capacity and excessive surface pressure on a raceway surface, and to contribute to miniaturization of a differential and a long life.

  A tapered roller bearing for a differential according to the present invention includes an inner ring, an outer ring, a plurality of tapered rollers arranged to roll between the inner ring and the outer ring, and a cage that holds the tapered rollers at a predetermined circumferential interval. The roller coefficient γ is more than 0.94.

  According to a second aspect of the invention, in the differential tapered roller bearing of the first aspect, the window angle of the pocket is set to 55 ° or more and 80 ° or less. The window angle is an angle formed by the guide surface of the pillar portion that abuts on the peripheral surface of one roller. The reason why the window angle is set to 55 ° or more is to ensure a good contact state with the roller, and the reason why the window angle is set to 80 ° or less is that the pressing force in the radial direction is increased when the value is further increased, and self-lubricating property is obtained. This is because there is a risk that smooth rotation cannot be obtained even with this resin material. In a normal cage, the window angle is 25 ° to 50 °.

According to a third aspect of the present invention, in the differential tapered roller bearing according to the first or second aspect, the cage is made of an engineering plastic excellent in mechanical strength, oil resistance and heat resistance. By using a resin material for the cage, the cage weight is lighter, self-lubricating, and the coefficient of friction is smaller than the steel plate cage. Coupled with, it is possible to suppress the occurrence of wear due to contact with the outer ring.

  Since these resins are lighter and have a smaller friction coefficient than steel plates, they are suitable for reducing torque loss and cage wear when starting the bearing.

Engineering plastics include general purpose engineering plastics and super engineering plastics. Typical examples are listed below, but these are examples of engineering plastics, and engineering plastics are not limited to the following.
[General-purpose engineering plastics] Polycarbonate (PC), polyamide 6 (PA6), polyamide 66 (PA66), polyacetal (POM), modified polyphenylene ether (m-PPE), polybutylene terephthalate (PBT), GF reinforced polyethylene terephthalate (GF) -PET), ultra high molecular weight polyethylene (UHMW-PE)
[Super Engineering Plastics] Polysulfone (PSF), Polyethersulfone (PES), Polyphenylene sulfide (PPS), Polyarylate (PAR), Polyamideimide (PAI), Polyetherimide (PEI), Polyetheretherketone ( PEEK), liquid crystal polymer (LCP), thermoplastic polyimide (TPI), polybenzimidazole (PBI), polymethylbenten (TPX), poly 1,4-cyclohexanedimethylene terephthalate (PCT), polyamide 46 (PA46), polyamide 6T (PA6T), polyamide 9T (PA9T), polyamide 11,12 (PA11,12), fluororesin, polyphthalamide (PPA)

  According to the present invention, by setting the roller coefficient γ of the differential tapered roller bearing to γ> 0.94, not only the load capacity is increased, but also the maximum surface pressure of the raceway surface can be reduced. It is possible to prevent surface-origin separation with an extremely short life under lubrication conditions. Therefore, it is possible to contribute to miniaturization and long life of the differential.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. The tapered roller bearing 1 of the embodiment shown in FIGS. 1A and 1B is for a differential as described above with reference to FIG. 7 and has a conical raceway surface 2a. The inner ring 2 having a small brim 2b on the small diameter side of the surface 2a and the large brim 2c on the large diameter side, the outer ring 3 having a conical raceway surface 3a, the raceway surface 2a of the inner ring 2 and the raceway surface 3a of the outer ring 3 And a plurality of tapered rollers 4 disposed so as to be freely rotatable, and a cage 5 that holds the tapered rollers 4 at equal intervals around the circumference. Here, the tapered roller bearing 1 for differential has a roller coefficient γ> 0.94.

  The cage 5 is integrally formed with a super engineering plastic such as PPS, PEEK, PA, PPA, PAI, for example, and includes a small-diameter side annular portion 5a, a large-diameter side annular portion 5b, a small-diameter-side annular portion 5a, and a large-diameter. A plurality of column portions 5c that connect the side annular portion 5b in the axial direction are provided.

  As for the window angle θ of the column surface 5d, the lower limit window angle θmin is 55 ° as shown in FIG. 2, and the upper limit window angle θmax is 80 ° as shown in FIG. The window angle of a typical tapered roller bearing with a cage in which the cage is spaced from the outer ring as shown in FIG. 9 is about 50 °. The reason why the lower limit window angle θmin is set to 55 ° or more is to ensure a good contact state with the roller, and when the window angle is less than 55 °, the contact state with the roller is deteriorated. That is, when the window angle is 55 ° or more, γ> 0.94 is obtained while securing the cage strength, and a good contact state can be secured. Further, the upper limit window angle θmax is set to 80 ° or less. If the upper limit window angle θmax is larger than 80 °, the pressing force in the radial direction increases, and there is a risk that smooth rotation cannot be obtained even with a self-lubricating resin material. Because.

  FIG. 4 shows the results of bearing life tests. In FIG. 4, “Comparative Example 1” in the “Bearing” column is a typical conventional tapered roller bearing in which the cage and the outer ring are separated, and “Example 1” is a conventional tapered roller bearing of the present invention. Tapered roller bearings in which only the roller coefficient γ is γ> 0.94, “Example 2” is the present invention in which the roller coefficient γ is γ> 0.94 and the window angle is in the range of 55 ° to 80 °. This is a tapered roller bearing. The test was conducted under severe lubrication and overload conditions. As can be seen from the figure, “Example 1” has a lifetime that is at least twice that of “Comparative Example”. Furthermore, the bearing of “Example 2” has a roller coefficient of 0.96 which is the same as that of “Example 1”, but the life time is about five times or more that of “Example 1”. The dimensions of “Comparative Example”, “Example 1” and “Example 2” are φ45 × φ81 × 16 (unit mm), and the number of rollers is 24 (“Comparative Example”) and 27 (“Example 1”). “Example 2”), and the oil film parameter Λ = 0.2.

Next, a modified embodiment of the present invention will be described with reference to FIGS. The tapered roller bearing 1 shown in FIG. 1 is formed by forming a protruding portion 5f that protrudes toward the outer ring raceway surface on the outer diameter surface of a column portion 5c of a cage 5 integrally formed of engineering plastic. . The rest is the same as the cage 5 described above. As shown in FIG. 6, the protruding portion 5f has a circular cross-sectional contour shape of the column portion 5c. The arcuate curvature radius R ₂ is smaller than the outer ring raceway surface radius R _1. This is so that good wedge-like oil film between the projections 5f and the outer ring raceway surface is formed, preferably the radius of curvature R ₂ of the protrusion about 70% to 90% of the outer ring raceway surface radius R ₁ It is good to form. If it is less than 70%, the opening angle of the wedge-shaped oil film becomes too large, and the dynamic pressure decreases. On the other hand, if it exceeds 90%, the inlet angle of the wedge-shaped oil film becomes too small, and the dynamic pressure similarly decreases. Further, the lateral width W ₂ of the protruding portion 5f is desirably formed to be 50% or more of the lateral width W ₁ of the column portion 5c (W ₂ ≧ 0.5 × W). This is because if it is less than 50%, a sufficient height of the protrusion 5f for forming a good wedge-shaped oil film cannot be secured. Since the outer ring raceway surface radius R ₁ continuously changes from the large diameter side to the small diameter side, the curvature radius R ₂ of the projection 5f is correspondingly large and the large curvature radius R _{2 of the} large diameter side annular portion 5b. To a small radius of curvature R ₂ of the small-diameter-side annular portion 5a.

  Since the tapered roller bearing 1 of FIGS. 5 and 6 is configured as described above, when the bearing 1 rotates and the cage 5 begins to rotate, the space between the outer ring raceway surface and the protrusion 5f of the cage 5 is increased. A wedge-shaped oil film is formed. Since this wedge-shaped oil film generates a dynamic pressure substantially proportional to the rotational speed of the bearing 1, even if the pitch circle diameter (PCD) of the cage 5 is made larger than that of the conventional and close to the outer ring raceway surface, the bearing 1 is greatly worn. In addition, it is possible to rotate without causing torque loss, and it is possible to increase the number of rollers without difficulty.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the above-described embodiment, super engineering plastics such as PPS, PEEK, PA, PPA, and PAI are used for the cage material. However, if necessary, these resin materials or other engineering plastics may be made of glass. You may use what mix | blended fiber or carbon fiber.

(A) is a cross-sectional view of the tapered roller bearing of the present invention, (B) is a vertical cross-sectional view of the bearing. The partial expanded sectional view of the tapered roller bearing whose window angle is a minimum. The partial expanded sectional view of the tapered roller bearing whose window angle is an upper limit. The figure which shows the result of the life test of a bearing. The fragmentary sectional view of the tapered roller bearing which concerns on the modification of this invention. Sectional drawing of the pillar part of the holder | retainer of FIG. A sectional view of a general automobile differential. Sectional drawing of the conventional tapered roller bearing which brought the retainer to the outer ring side. The partial expanded sectional view of another conventional tapered roller bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing 2 Inner ring 2a Raceway surface 2b Small collar part 2c Large collar part 3 Outer ring 3a Raceway surface 4 Tapered roller 5 Cage 5a Small diameter side annular part 5b Large diameter side annular part 5c Column part 5d Column surface 5f Projection part

Claims (3)

  In a tapered roller bearing comprising an inner ring, an outer ring, a plurality of tapered rollers arranged to roll between the inner ring and the outer ring, and a retainer for holding the tapered rollers at a predetermined circumferential interval, A tapered roller bearing for a differential, characterized in that the roller coefficient γ exceeds 0.94.   2. The tapered roller bearing for a differential according to claim 1, wherein the window angle of the pocket is set to 55 ° or more and 80 ° or less. 3. The differential tapered roller bearing according to claim 1, wherein the cage is made of an engineering plastic excellent in mechanical strength, oil resistance and heat resistance.