JP2004197819A - Differential gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential gear enabling improvement of fuel economy by using a low torque bearing instead of a taper roller bearing and improving problems of reduction of lifetime and increase of cost. <P>SOLUTION: The differential gear is provided with a pair of rolling bearings 30, 31 rotatably supporting a differential case 5 on a differential carrier 1. Angular ball bearing is used for each rolling bearing 30, 31. Heat treatment of carbonitriding hardening, subzero treatment, and tempering at 180°C, in order, is applied on inner rings 32, 36. Fine carbonitrides is precipitated in a surface layer of the inner rings 32, 36. Hardness of the inner rings 32, 36 and balls 34, 38 satisfy conditions of 61≤Rockwell hardness C of the inner ring≤66, 0<(Rockwell hardness C of the ball-Rockwell hardness C of the inner ring)≤1 with a condition 62≤Rockwell hardness C of the ball≤67 satisfied. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a differential device that makes a difference in rotation between left and right wheels, and more particularly, to a differential device having an improved rolling bearing.
[0002]
[Prior art]
As a differential device, a pinion shaft rotatably supported by a differential carrier and having a pinion gear disposed at one end thereof, a ring gear meshed with the pinion gear, and a ring gear attached to the ring gear A differential case and a pair of rolling bearings that rotatably support the differential case on a differential carrier are used.
[0003]
Rolling bearings of differential devices have been conventionally tapered roller bearings in order to obtain high rigidity. However, lowering the torque of the bearings has been an issue from the viewpoint of improving fuel efficiency, and rotational torque is smaller than that of tapered roller bearings. It has been proposed to use ball bearings. (See Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-161466
[Problems to be solved by the invention]
In differential devices using ball bearings, the rigidity is usually lower than that of tapered roller bearings. Therefore, the manufacturing cost increases due to material changes to achieve both low torque and high rigidity. There are new issues such as concern over the reduction of service life due to use in oil, and there is a need for a differential device having a bearing that solves these new issues and ensures low torque and high rigidity. ing.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a differential device that uses a low torque bearing instead of a tapered roller bearing to improve fuel efficiency and improve the problem of reduced life and increased cost.
[0007]
[Means for Solving the Problems and Effects of the Invention]
The differential according to the present invention includes a pinion shaft rotatably supported on a differential carrier and having a pinion gear disposed at one end thereof, a ring gear meshed with the pinion gear, and a ring gear. A differential device comprising an attached differential case and a pair of rolling bearings rotatably supporting the differential case on a differential carrier, wherein at least a pinion gear of the pair of rolling bearings The one that is far from the meshing position with the ring gear is an oblique contact ball bearing, and the hardness of the inner ring and the ball of the oblique contact ball bearing satisfies the following conditions. is there.
[0008]
0 <(ball Rockwell C hardness−inner ring Rockwell C hardness) ≦ 1,
61 ≦ Rockwell C hardness of inner ring ≦ 66,
62 ≦ Tama Rockwell C hardness ≦ 67
Here, the hardness of the inner ring and the ball refers to the hardness at the surface layer portion (about 0.5 mm deep from the surface).
[0009]
The Rockwell C hardness of the inner ring of the conventional bearing steel (JIS SUJ-2) oblique contact ball bearing is 60 to 64, and the Rockwell C hardness of the ball of the conventional oblique contact ball bearing is 62 to 67. It is. In order to satisfy the above conditions, it is necessary to increase the hardness of the inner ring as compared with the prior art. For this reason, the inner ring is subjected to a heat treatment that is tempered at about 180 ° C. after carbonitriding and quenching, for example. Is done. In addition, as described in Japanese Examined Patent Publication No. 3-56305, heat treatment may be performed after sub-zero treatment after carbonitriding. Although the contact angle of the ball bearing is 15 to 20 °, the load capacity decreases as the contact angle increases, so 15 to 17 ° is more preferable.
[0010]
According to the differential of the present invention, since the rolling bearing is an oblique contact ball bearing, the rotational torque is smaller than that of the tapered roller bearing, the fuel efficiency can be improved, and the hardness of the inner ring of the bearing is substantially reduced. In particular, by making it the same as the hardness of the ball, the wear resistance in the foreign oil is improved and the life is prevented from being shortened. Oblique contact ball bearings are advantageous in terms of load capacity and rigidity compared to deep groove ball bearings. In this oblique contact ball bearing, the hardness of the inner ring is made equal to the hardness of the ball, so that low torque and high torque are achieved. Coexistence with rigidity becomes possible. Moreover, in order to make the hardness of the both substantially the same, it can be achieved by an appropriate heat treatment method without using means such as changing the material to ceramic, and low torque and high rigidity can be achieved without increasing costs. Can be made compatible.
[0011]
A pair of rolling bearings is usually used face to face. The oblique contact ball bearing on the side far from the gear meshing position is, for example, a single row ball bearing. In this case, the rolling bearing on the side close to the gear meshing position may be a single row oblique contact ball bearing. However, those having higher rigidity than those on the far side, such as a tapered roller bearing and a double row oblique contact ball bearing, are more preferable. By making the rolling bearing on the side closer to the gear meshing position relatively rigid, the rotational torque can be reduced and the fuel consumption can be improved compared to the case where both of the rolling bearings are tapered roller bearings. In addition, the load on the oblique contact ball bearing on the side far from the gear meshing position can be reduced, and it can also be applied to vehicles with severe use conditions such as heavy vehicle weight and large horsepower. For example, when a double-row oblique contact ball bearing is used on the side closer to the gear meshing position, the effect of lowering the rotational torque is great, and the rated capacity of the bearing can be increased.
[0012]
In the above differential device, it is preferable that fine carbonitride is deposited on the surface layer portion of the inner ring of the oblique contact ball bearing. This carbonitride preferably has an average particle size of 0.3 to 0.8 μm and a maximum particle size of 4 μm or less. In order to obtain such an inner ring, the inner ring made of a high carbon steel material is subjected to a treatment such as carbonitriding or nitriding so that the substrate of the surface layer part becomes high carbon / high nitrogen from the inside, and at least the surface layer part is made of carbon / It is possible to form nitrides and perform quenching to increase the retained austenite of the surface layer substrate from the inside, and then to perform tempering in the range of 180 to 250 ° C. Instead of tempering in the range, it is also possible to perform tempering in the range of 150 to 200 ° C. after performing the sub-zero treatment. As a result, the inner ring after the heat treatment is substantially free of retained austenite inside, while an appropriate amount of austenite remains in the surface layer portion, and the surface layer portion has retained austenite more than in the interior. Due to the large amount of decomposition, the residual compressive stress is also increased, and the surface hardness is also maintained by the tempering resistance of the carbonitrided layer.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following description, the left and right refer to the left and right in the figure.
[0014]
FIG. 1 shows a first embodiment of a differential device according to the present invention. The differential device is rotatably supported by a differential carrier (1) and a drive pinion gear (3) is arranged at one end. The installed pinion shaft (2), the ring gear (4) meshed with the drive pinion gear (3), the differential case (5) attached to the ring gear (4), and the differential gear A pair of left and right rolling bearings (10) and (11) that rotatably support the case (5) on the differential carrier (1), and left and right side gear shafts (6) extending from the differential case (5) to the left and right A side gear (7) disposed at each inner end portion and a differential pinion gear (8) rotatably supported by the spider (9) and meshed with the side gear (7) are provided.
[0015]
The left rolling bearing (10), that is, the bearing close to the meshing position of the drive pinion gear (3) and the ring gear (4) is an inner ring (12) fixed to the outer periphery of the left end of the differential case (5). ), An outer ring (13) fixed to the differential carrier (1) at a position facing the inner ring (12), a plurality of balls (14) disposed between both wheels (12) and (13), and a cage (15) Is a single row oblique contact ball bearing. The counter bore (13a) is positioned on the right side (in the axial direction) of the outer ring (13).
[0016]
The right rolling bearing (11), that is, the bearing far from the meshing position of the drive pinion gear (3) and the ring gear (4) is an inner ring (16) fixed to the outer periphery of the right end of the differential case (5). ), An outer ring (17) fixed to the differential carrier (1) at a position facing the inner ring (16), a plurality of balls (18) arranged between both wheels (16) and (17), and a cage (19) Is a single row oblique contact ball bearing. The counter bore (17a) is positioned on the left side (axially inner side) of the outer ring (17).
[0017]
In each oblique contact ball bearing which is the left and right rolling bearings (10) and (11), the hardness of the inner rings (12) and (16) is substantially the same as the hardness of the balls (14) and (18). More specifically, the inner rings (12) and (16) are subjected to heat treatment in the order of carbonitriding and quenching and tempering at 180 ° C., so that the surface of the inner rings (12) and (16) is finely carbonized. Nitride precipitates (average particle size 0.6 μm, maximum particle size 3 μm), 61 ≦ inner ring Rockwell C hardness ≦ 66, 0 <(ball Rockwell C hardness−inner ring Rockwell C hardness ) ≦ 1, where 62 ≦ ball Rockwell C hardness ≦ 67.
[0018]
According to the differential device of the first embodiment, the left and right rolling bearings (10) and (11) are oblique contact ball bearings, so that the rotational torque of the left and right rolling bearings is smaller than that of the tapered roller bearing. The fuel consumption can be improved, and the hardness of the inner rings (12) and (16) is substantially equal to the hardness of the balls (14) and (18) in both the left and right oblique contact ball bearings (10) and (11). Since they are the same, the wear resistance is improved and the life of the rolling bearings (10) and (11) in foreign oil is improved.
[0019]
FIG. 2 shows a second embodiment of the differential according to the present invention. Since the difference from the first embodiment is only the rolling bearing, the configuration other than the rolling bearing is denoted by the same reference numeral and the description thereof is omitted, and only the rolling bearing will be described below.
[0020]
In the second embodiment, the left rolling bearing (20), that is, the bearing closer to the meshing position of the drive pinion gear (3) and the ring gear (4) is the outer periphery of the left end of the differential case (5). The inner ring (22) fixed to the inner ring (22), the outer ring (23) fixed to the differential carrier (1) at a position facing the inner ring (22), and a plurality of tapered rollers arranged between both wheels (22) (23) ( 24) and a single row tapered roller bearing provided with a cage (25).
[0021]
And the right rolling bearing (21), that is, the bearing far from the meshing position of the drive pinion gear (3) and the ring gear (4) is the inner ring fixed to the outer periphery of the right end of the differential case (5). (26), an outer ring (27) fixed to the differential carrier (1) at a position facing the inner ring (26), a plurality of balls (28) disposed between both wheels (26) and (27), and a cage ( It is a single row oblique contact ball bearing with 29). The counter bore (27a) is positioned on the left side (axially inner side) of the outer ring (27).
[0022]
In the oblique contact ball bearing which is the right rolling bearing (21), the hardness of the inner ring (26) is substantially the same as the hardness of the ball (28). More specifically, the inner ring (26) is subjected to heat treatment in the order of carbonitriding and quenching and tempering at 180 ° C., whereby fine carbonitride (average particle size) is formed on the surface layer portion of the inner ring (26). 0.6 [mu] m, maximum particle size 3 [mu] m), and 61≤inner ring Rockwell C hardness≤66, 0 <(ball Rockwell C hardness-inner ring Rockwell C hardness) ≤1 (however, 62 ≦ ball Rockwell C hardness ≦ 67).
[0023]
According to the differential device of the second embodiment, since the right rolling bearing (21) is an oblique contact ball bearing, the left and right rolling bearings are smaller in torque than the tapered roller bearing, and the fuel consumption is reduced. Can be improved. Since the left rolling bearing (20), that is, the bearing with the larger load load is a tapered roller bearing, the rigidity is higher than that of the first embodiment, and a greater load resistance can be obtained. .
[0024]
FIG. 3 shows a third embodiment of the differential according to the present invention. Since the difference from the first embodiment is only the rolling bearing, the configuration other than the rolling bearing is denoted by the same reference numeral and the description thereof is omitted, and only the rolling bearing will be described below.
[0025]
In the third embodiment, the left rolling bearing (30), that is, the bearing close to the meshing position of the drive pinion gear (3) and the ring gear (4) is the outer periphery of the left end portion of the differential case (5). The inner ring (32) fixed to the inner ring (32), the outer ring (33) fixed to the differential carrier (1) at a position facing the inner ring (32), and a plurality of rows arranged in two rows between both wheels (32) (33) A double-row tandem oblique contact ball bearing including a ball (34) and a cage (35) is provided. In this oblique contact ball bearing (30), the inner ring (32) and the outer ring (33) are integrally formed, and the counter bore (33a) is positioned on the right side (axially inside) of the outer ring (33). The inner ring raceway diameter and the outer ring raceway diameter on the left side (axially outer side) are made smaller than the inner ring raceway diameter and the outer ring raceway diameter on the right side (axially inner side), respectively.
[0026]
The right rolling bearing (31), that is, the bearing far from the meshing position of the drive pinion gear (3) and the ring gear (4) is an inner ring fixed to the outer periphery of the right end of the differential case (5). (36), an outer ring (37) fixed to the differential carrier (1) at a position facing the inner ring (36), a plurality of balls (38) disposed between both wheels (36) and (37), and a cage ( 39) and a single row oblique contact ball bearing. The counter bore (37a) is positioned on the left side (axially inner side) of the outer ring (37).
[0027]
In each oblique contact ball bearing which is the left and right rolling bearings (30) and (31), the hardness of the inner rings (32) and (36) is substantially the same as the hardness of the balls (34) and (38). More specifically, the inner ring (36) is subjected to heat treatment in the order of carbonitriding and quenching and tempering at 180 ° C., whereby fine carbonitride (average particle size) is formed on the surface layer portion of the inner ring (36). 0.6 [mu] m, maximum particle size 3 [mu] m), and 61≤inner ring Rockwell C hardness≤66, 0 <(ball Rockwell C hardness-inner ring Rockwell C hardness) ≤1 (however, 62 ≦ ball Rockwell C hardness ≦ 67).
[0028]
According to the differential device of the third embodiment, since the left and right rolling bearings (30) and (31) are oblique contact ball bearings, the rotational torque of the left and right rolling bearings is smaller than that of the tapered roller bearing. , Fuel economy can be improved. And since the left rolling bearing (30), that is, the bearing with the larger load load is a double row oblique contact ball bearing, the rated capacity is increased and the use conditions are more severe than those of the first embodiment. Applicable to cars.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a first embodiment of a differential according to the present invention.
FIG. 2 is a longitudinal sectional view showing a second embodiment of the differential according to the present invention.
FIG. 3 is a longitudinal sectional view showing a third embodiment of the differential according to the present invention.
[Explanation of symbols]
(1) Differential carrier
(2) Pinion shaft
(3) Pinion gear
(4) Ring gear
(5) Differential case
(10) (20) (30) Left rolling bearing
(11) (21) (31) Right rolling bearing
(12) (16) (26) (32) (36) Inner ring
(14) (18) (28) (34) (38) Ball

Claims (2)

A pinion shaft rotatably supported by a differential carrier and having a pinion gear disposed at one end thereof, a ring gear meshed with the pinion gear, and a differential case attached to the ring gear; In a differential having a pair of rolling bearings that rotatably support a differential case on a differential carrier,
Among the pair of rolling bearings, at least the one farther from the meshing position of the pinion gear and the ring gear is the oblique contact ball bearing. A differential device characterized by satisfying each condition.
0 <(ball Rockwell C hardness−inner ring Rockwell C hardness) ≦ 1,
61 ≦ Rockwell C hardness of inner ring ≦ 66,
62 ≦ Tama Rockwell C hardness ≦ 67 2. The differential according to claim 1, wherein fine carbonitride is deposited on the surface layer portion of the inner ring of the oblique contact ball bearing.

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