JP2003239999A - Rolling bearing unit for supporting wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce rotation torque of a hub rotating together with a wheel to improve running performance of a vehicle based on acceleration performance and fuel economy performance mainly while ensuring required durability. <P>SOLUTION: Grease is filled into an inside space in which balls 14, 14 are provided to lubricate a rolling contact part. Dynamic viscosity of this grease at 100°C is regulated within a scope of 5.0×10<SP>-6</SP>to 9.0×10<SP>-6</SP>m<SP>2</SP>/s. Owing to this configuration, a leak of grease from a sealing member is prevented, and rolling resistance in the rolling contact part is reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a wheel supporting rolling bearing unit for rotatably supporting wheels on a vehicle suspension. [0002] As a rolling bearing unit for supporting wheels,
For example, JP-A-2001-221243 discloses that FIG.
7 is described. First, the structure of the first example shown in FIG. 6 will be described. The wheel 1 constituting the wheel includes a wheel supporting rolling bearing unit 2
Thereby, it is rotatably supported at the end of the axle 3 constituting the suspension device. That is, the inner races 5, which are stationary raceways, constituting the wheel supporting rolling bearing unit 2 are externally fitted to the support shaft 4 fixed to the end of the axle 3, and the nut 6
It is fixed by. On the other hand, the wheel 1 is mounted on a hub 7, which is a rotating raceway, that constitutes the wheel supporting rolling bearing unit 2, and a plurality of studs 8, 8 and nuts 9,
9 and fixed. On the inner peripheral surface of the hub 7, double rows of outer raceways 10a and 10b, each of which is a rotating raceway surface, are formed, and on the outer peripheral surface, a mounting flange 11 is formed. The wheel 1 is connected and fixed to one side surface (outside surface in the illustrated example) of the mounting flange 11 together with a drum 12 for constituting a braking device by the studs 8, 8 and nuts 9, 9. ing. A rolling element is provided between each of the outer raceways 10a, 10b and each of the inner raceways 13, 13 formed on the outer peripheral surface of each of the inner races 5, 5, each of which is a stationary raceway surface. A plurality of balls 14, 14 are provided so as to roll freely while being held by holders 15, 15, respectively. By combining the constituent members in this way, a double row angular type ball bearing that is a back combination is configured,
The hub 7 is rotatable around each of the inner rings 5, 5,
In addition, it supports the radial load and the thrust load freely. In addition, seal rings 16a and 16b are provided between the inner peripheral surfaces of both ends of the hub 7 and the outer peripheral surfaces of the ends of the inner rings 5 and 5, respectively, and the internal space in which the balls 14 and 14 are provided. 17 and the outside space. Further, the outer end of the hub 7 (the term "outside in the axial direction" refers to the outside in the width direction when assembled to the vehicle. Similarly, the center side in the width direction is referred to as "in". The same applies throughout the specification). , And the cap 18. When the above-described rolling bearing unit 2 for supporting a wheel is used, as shown in FIG. 6, the supporting shaft 4 having the inner rings 5, 5 externally fixed thereto is fixed to the axle 3, and the mounting flange of the hub 7 is fixed. 11, the wheel 1 and the drum 12 combined with a tire (not shown) are fixed. Further, a drum brake for braking is constituted by combining the drum 12 among them, a wheel cylinder and a shoe (not shown) supported on a backing plate 19 fixed to the end of the axle 3. At the time of braking, 1 is provided on the inner diameter side of the drum 12.
A pair of shoes is pressed against the inner peripheral surface of the drum 12.
It should be noted that grease is sealed in the internal space 17 so that the outer raceways 10a, 10b and the inner raceways 13, 1
The lubrication of the rolling contact portion between the ball 3 and the rolling surface of each of the balls 14, 14 is performed. Next, a second example of the conventional structure shown in FIG. 7 will be described. This wheel supporting rolling bearing unit 2a
In the case of, on the inner diameter side of the outer race 20 which is a stationary raceway,
The hub 7a, which is a rotating raceway, is rotatably supported by a plurality of balls 14, 14, each of which is a rolling element. For this purpose, double-row outer raceways 10a and 10b, each of which is a stationary raceway surface, are provided on the inner circumferential surface of the outer race 20, and first and second outer raceways which are rotation raceway surfaces, respectively, on the outer circumferential surface of the hub 7a. Are provided respectively. The hub 7a is formed by combining a hub main body 23 and an inner ring 24. The mounting flange 11a for supporting the wheel is provided at the outer end of the outer peripheral surface of the hub main body 23, the first inner raceway 21 is also provided at the intermediate part, and the first inner race is provided at the part near the inner end of the intermediate part. Small-diameter step portions 25 each having a smaller diameter than the portion where the track 21 is formed are provided. The inner ring 24 provided with the second inner ring raceway 22 having an arc-shaped cross section on the outer peripheral surface is externally fitted to the small diameter step 25. Further, the inner ring 24 is formed by a caulking portion 26 formed by plastically deforming the inner end of the hub body 23 radially outward.
Of the hub body 2 by pressing down the inner end face of the hub body 2.
3 is fixed. Further, seal rings 16c and 16d are provided between the inner peripheral surfaces of both ends of the outer ring 20 and the outer peripheral surface of the intermediate portion of the hub body 23 and the inner peripheral portion of the inner ring 24, respectively. Internal space 17a in which the balls 14, 14 are provided between the inner peripheral surface of the hub 20 and the outer peripheral surface of the hub 7a.
And the outside space. Grease is sealed in the inner space 17a, and the outer raceways 10a, 10a
b and the rolling contact portions between the first and second inner raceways 21, 22 and the rolling surfaces of the balls 14, 14 are lubricated. [0008] In the case of the rolling bearing units 2 and 2a for supporting wheels as described above, conventionally, the grease sealed in the internal spaces 17, 17a has a kinematic viscosity of 10 at 100 ° C. × 10 ^{-6 to} 16 × 10 ^-6 m ² / s (10
〜16 cSt). For this reason, the torque (rotational resistance of the wheel supporting rolling bearing unit) required for the rotation of the hubs 7 and 7a cannot always be reduced sufficiently. As a result, the wheel supporting rolling bearing unit 2,
Since the running performance of the vehicle incorporating the 2a, especially the acceleration performance and the fuel consumption performance, is deteriorated, improvement is desired in response to the recent trend of energy saving. The rolling bearing unit for supporting a wheel of the present invention has been invented in view of such circumstances. [0009] The rolling bearing unit for supporting a wheel according to the present invention comprises a stationary raceway and a rolling bearing similar to the above-mentioned rolling bearing unit for supporting a wheel.
The vehicle includes a rotating race and a plurality of rolling elements. Of these, the stationary raceway is supported and fixed to the suspension device in use. Further, the rotating raceway supports and fixes the wheel in use. Further, each of the rolling elements is provided between a stationary raceway surface and a rotating raceway surface which are present on peripheral surfaces of the stationary raceway ring and the rotating raceway facing each other. Then, a rolling contact portion between each of the raceway surfaces and each of the rolling elements is lubricated with grease. In particular, in the wheel bearing rolling bearing unit of the present invention, the kinematic viscosity at 100 ° C. of the grease is 5.0 × 10 ^{−6 to} 9.0 × 10 ⁻⁶ m ² / s.
(5.0 to 9.0 cSt). In the case of the rolling bearing unit for supporting a wheel according to the present invention constructed as described above, the lubricating property of the rolling contact portion between each of the stationary and rotating track surfaces and the rolling surface of each rolling element. And the rotational torque can be sufficiently reduced. First, the reason why the rotational torque can be reduced will be described with reference to FIG. FIG. 5 shows a graph of 100
4 shows the relationship between the kinematic viscosity of grease at ° C. and the rotational torque (rotational resistance) of a wheel supporting rolling bearing unit lubricated by the grease. As is apparent from FIG. 5, the rotational torque increases as the kinematic viscosity increases, but the kinematic viscosity becomes 9.0 × 10 ⁻⁶ m ² / s.
When it exceeds (9.0 cSt), it rapidly increases. On the other hand, in the case of the rolling bearing unit for supporting a wheel of the present invention, the kinematic viscosity is suppressed to 9.0 × 10 ⁻⁶ m ² / s or less, so that the rotational torque of the rolling bearing unit for supporting a wheel is reduced. Can be kept low. Next, the reason why the lubrication of the rolling contact portion can be ensured will be described. If the kinematic viscosity is too low, the fluidity of the grease becomes excessively high, so that the grease easily leaks from sealing means such as a seal ring and a cap. The following Table 1 shows that the present inventor used a wheel supporting rolling bearing unit as shown in FIG.
The results of an experiment conducted to determine the effect of the kinematic viscosity of grease at 00 ° C. on the presence or absence of leakage from the sealing means are shown. [Table 1] As is clear from the description in Table 1, 10 of the above greases
The kinematic viscosity at 0 ° C. is 5 × 10 ⁻⁶ m ^{2 / s (} 5.0 cSt)
If the above is ensured, it is possible to prevent the grease from leaking from the sealing means. And, despite long-term use,
The stationary side, the rotating side each track surface and the rolling contact surface of each rolling element prevents the amount of grease present in the rolling contact portion from being insufficient, ensuring the lubrication of the rolling contact portion, and supporting the wheel. The rolling fatigue life of the rolling bearing unit can be ensured. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Four examples of the structure of a rolling bearing unit for supporting a wheel to which the present invention is applied will be described. still,
The feature of the present invention is to properly regulate the kinematic viscosity of the grease sealed in the space in which the rolling elements are installed, and to lubricate the rolling contact portions between the stationary and rotating track surfaces and the rolling surfaces of the rolling elements. The point is to reduce the rotational torque while ensuring the performance. The specific structure of the wheel bearing rolling bearing unit in which the grease is to be filled is also applicable to the structure shown in FIGS. 6 and 7 described above. Hereinafter, a more preferable structure for practicing the present invention will be described. I will explain this. First, FIG. 1 shows a first example of a structure suitable as a rolling bearing unit for supporting a wheel, which is an object of the present invention. In this example, the structure shown in FIG. 7 is improved to further reduce the rotational torque of the hub 7b. For this reason, in the case of this example, the inner end opening of the outer ring 20 is closed by the cap 18a, and the space between the inner peripheral surface of the outer end of the outer ring 20 and the outer peripheral surface of the intermediate portion of the hub body 23 is sealed by the seal ring 16c. I'm blocking. Outer ring 2
The seal ring 16d (FIG. 7) between the inner peripheral surface of the inner end portion 0 and the outer peripheral surface of the inner race 24 is omitted. Prevention of foreign matter such as muddy water from entering the internal space 17b in which the balls 14, 14 are installed is prevented by the seal ring 16c and the cap 18a. The grease sealed in the internal space 17b has a kinematic viscosity at 100 ° C. of 5.0.
Using those ^{× 10 -6 ~9.0 × 10 -6 m} 2 / s. The structure of the other parts is the same as the conventional structure shown in FIG. Next, FIG. 2 shows a second example of a structure suitable as a rolling bearing unit for supporting a wheel, which is an object of the present invention. In the case of this example, a male screw portion 27 is provided at the inner end of the hub main body 23a constituting the hub 7c, and the hub main body 23a is screwed onto the male screw portion 27 by a nut 28.
The inner end surface of the inner ring 24 fitted to the small-diameter step portion 25 is suppressed. In accordance with this, the shape of the cap 18b attached to the inner end opening of the outer ring 20 is expanded, and the male screw 2
7 and the nut 28 are prevented from interfering with each other. Other configurations are the same as those in the first example described above. Next, FIG. 3 shows a third example of a structure suitable as a rolling bearing unit for supporting a wheel, which is an object of the present invention. The first and second examples described above correspond to driven wheels (FR and R
In contrast to the structure for supporting the front wheels of the R vehicle and the rear wheels of the FF vehicle, in the case of this example, the driving wheels (the rear wheels of the FR and RR vehicles, the front wheels of the FF vehicle, and the four wheels of the WD vehicle) This is a structure for supporting all wheels). For this reason, in the case of this example, a spline hole 29 is provided at the center of the hub main body 23b constituting the hub 7d, which is the rotating raceway, rotatably supported on the inner diameter side of the outer race 20, which is the stationary raceway. Has formed. A spline shaft (not shown) attached to the constant velocity joint is inserted into the spline hole 29 in an assembled state to the vehicle. The inner end surface of the inner race 24 externally fitted to the small diameter step 25 formed at the inner end of the hub main body 23b is formed by plastically deforming the inner end of the hub main body 23b radially outward. The inner ring 24 is fixed to the hub main body 23b while being held down by the caulking portion 26, thereby constituting the hub 7d. Seal rings 16c and 16d are provided between inner peripheral surfaces of both ends of the outer ring 20 and outer peripheral surfaces of an intermediate portion of the hub body 23b and inner ends of the inner ring 24, respectively.
And an inner space 17b in which the balls 14, 14 are provided between the inner peripheral surface of the outer race 20 and the outer peripheral surface of the hub 7b,
It blocks off the outside space. Other configurations are the same as those in the first and second examples. Next, in the case of the fourth example shown in FIG. 4, the inner ring 24 which is externally fitted to the small-diameter stepped portion 25 provided at the inner end of the hub body 23c and forms the hub 7e together with the hub body 23c.
Is projected more inward than the inner end face of the hub body 23c. When the inner ring 24 is mounted on the vehicle,
An outer end surface of a constant velocity joint (not shown) abuts on the inner end surface of the inner ring to prevent the inner ring 24 from falling off from the small-diameter stepped portion 25. Other configurations are the same as those of the above-described third example. The rolling bearing unit for supporting a wheel according to the present invention is constructed and operates as described above, so that the rotating torque of the hub that rotates together with the wheels is reduced while ensuring the required durability. As a result, it is possible to contribute to the improvement of the running performance of the vehicle, mainly the acceleration performance and the fuel consumption performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a half sectional view showing a first example of a structure to which the present invention is applied. FIG. 2 is a half sectional view showing the second example. FIG. 3 is a sectional view showing a third example. FIG. 4 is a sectional view showing a fourth example. FIG. 5 is a diagram showing a relationship between kinematic viscosity of grease and rotation torque of a rolling bearing unit. FIG. 6 is a cross-sectional view showing a first example of a conventionally known rolling bearing unit for supporting a wheel in a state of being assembled to a suspension device. FIG. 7 is a sectional view showing the second example. [Description of Signs] 1 Wheel 2, 2a Rolling bearing unit for wheel support 3 Axle 4 Support shaft 5 Inner ring 6 Nut 7, 7a, 7b, 7c, 7d, 7e Hub 8 Stud 9 Nut 10a, 10b Outer ring raceway 11, 11a Mounting Flange 12 Drum 13 Inner ring track 14 Ball 15 Cage 16a, 16b, 16c, 16d Seal ring 17, 17a, 17b Internal space 18, 18a, 18b Cap 19 Backing plate 20 Outer ring 21 First inner ring track 22 Second inner ring track 23, 23a, 23b, 23c Hub main body 24 Inner ring 25 Small diameter stepped portion 26 Caulked portion 27 Male screw portion 28 Nut 29 Spline hole

Claims (1)

Claims: 1. A stationary raceway supported and fixed to a suspension device in a use state, a rotating raceway supporting and fixing a wheel in a use state, and a stationary raceway and a rotating raceway. A plurality of rolling elements provided between the stationary raceway surface and the rotating raceway surface which are present on the peripheral surfaces facing each other with the wheel, and a rolling contact portion between each raceway surface and each rolling body is provided. In a wheel supporting rolling bearing unit lubricated by grease, the kinematic viscosity at 100 ° C. of the grease is 5.0 × 10 ^{−6 to} 9.0.
× 10 ⁻⁶ m ² / s, a rolling bearing unit for supporting wheels.