WO2003071148A1

WO2003071148A1 - Rolling bearing unit for wheel support

Info

Publication number: WO2003071148A1
Application number: PCT/JP2003/001943
Authority: WO
Inventors: Junshi Sakamoto
Original assignee: Nsk Ltd.
Priority date: 2002-02-25
Filing date: 2003-02-21
Publication date: 2003-08-28
Also published as: AU2003207106A1; JP2005299684A

Abstract

Of the two end openings of a space in which balls (14, 14) are received, the inner end opening is closed by a cap (17a). Further, the outer end opening is closed by a sealing ring (16c) having three seal lips. The rolling resistance that changes on the basis of preload is controlled to be within the range of 0.12 - 0.23 N·m, and the rotation resistance of this seal ring (16c) based on the friction between each seal lip and the mating surface is controlled to be within the range of 0.03 - 0.2 N·m. This reduces the rotation torque of the hub rotating with the wheel while securing steering stability, thus improving the traveling performance of the vehicle centered on acceleration performance and fuel consumption performance.

Description

Description Rolling bearing unit for wheel support Technical field

The present invention relates to a rolling bearing unit for supporting wheels, which rotatably supports wheels, particularly driven wheels (rear wheels of FF vehicles, front wheels of FR vehicles and RR vehicles), with respect to a suspension system of a vehicle. Regarding improvement. Background art

As a rolling bearing unit for supporting a wheel, for example, Japanese Patent Application Laid-Open No. 2001-221243 describes a structure as shown in FIGS. First, the structure of the first example shown in FIG. 12 will be described. A wheel 1 constituting a wheel is rotatably supported on an end of an axle 3 constituting a suspension device by a rolling bearing unit 2 for supporting a wheel. 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 fixed by the nut 6. . On the other hand, the wheel 1 is fixedly connected to a hub 7, which is a rotating raceway, constituting the wheel supporting rolling bearing unit 2 by a plurality of studs 8, 8 and nuts 9, 9.

The inner circumferential surface of the hub 7 is formed with double-row outer raceways 10a and 10b, each of which is a rotating raceway surface, and the outer circumferential surface is formed with a mounting flange 11 respectively. The wheel 1 is mounted on one side (the outer side in the illustrated example) of the mounting flange 11 together with a drum 12 for constituting a braking device by the studs 8 and 8 and nuts 9 and 9. The connection is fixed.

Balls 14, 10 are provided between the outer raceways 10a, 10b and the inner raceways 13, 13 formed on the outer peripheral surface of the inner races 5, 5, each of which is a stationary raceway surface. 14 are provided so as to roll freely while being held by a plurality of cages 15 and 15, respectively. By combining the constituent members in this way, a double-row anguilla type ball bearing, which is a back-to-back combination, is configured, and the hub 7 is rotated around each of the inner rings 5, 5. It supports freely and radial and thrust loads freely. In addition, seal rings 16a and 16b are provided between the inner peripheral surfaces of both ends of the above-mentioned eight lobes 7 and the outer peripheral surfaces of the ends of the above-mentioned inner races 5 and 5, respectively, so that the above-mentioned balls 1 It blocks the space provided with 4, 14 and the outside space. Further, the outer end of the above-mentioned bracket 7 (the term "outer in the axial direction" means the outer side in the width direction when assembled to the vehicle. Similarly, the center side in the width direction is called "inside". The same applies throughout the present specification.) Is closed by a cap 17 which is a sealing member other than the seal ring.

When using the rolling bearing unit 2 for wheel support as described above, as shown in FIG. 11 Fix wheel 1 and drum 12 with tires (not shown) in combination. Also, a drum drum for braking is configured by combining the drum 12 of these with a wheel cylinder and a shoe (not shown) supported by a packing plate 18 fixed to the end of the axle 3. At the time of braking, a pair of shoes provided on the inner diameter side of the drum 12 is pressed against the inner peripheral surface of the drum 12.

Next, a second example of the conventional structure shown in FIG. 13 will be described. In the case of this wheel supporting rolling bearing unit 2a, a hub 7a as a rotating raceway is provided on the inner diameter side of an outer ring 19 as a stationary raceway, and a plurality of balls each being a rolling element. It is supported rotatably by 14 and 14. For this purpose, the double-row outer raceways 10a and 10b, each of which is a stationary raceway surface, are rotated on the inner circumferential surface of the outer race 19, respectively, on the outer circumferential surface of the hub 7a. First and second inner raceways 20 and 21 which are side raceway surfaces are provided, respectively. The hub 7a is formed by combining a hub body 22 and an inner ring 23. At the outer end of the outer peripheral surface of the hub body 22, the mounting flange 11 a for supporting the wheel is also provided, the first inner raceway 20 is also provided at the intermediate portion, and the inner end track is also provided at the intermediate portion. The small-diameter step portions 24 each having a smaller diameter than the portion where the first inner ring raceway 20 is formed are provided. The inner ring 23 provided with the second inner ring raceway 21 having an arc-shaped cross section on the outer peripheral surface is externally fitted to the small-diameter stepped portion 24. Further, the inner end surface of the inner ring 23 is suppressed by a caulking portion 25 formed by plastically deforming the inner end portion of the hub body 22 radially outward, and the inner ring 23 is attached to the hub body 22. On the other hand, it is fixed. Further, the inner peripheral surfaces of both ends of the outer ring 19, the outer peripheral surface of the intermediate portion of the hub 7a, and the inner ring Seal rings 16c and 16d are provided between the inner peripheral surface of the inner end of the outer ring 19 and the outer peripheral surface of the hub 7a. It blocks the space where 14 and 14 are installed from the external space.

In the case of the conventional structure described above, seal rings 16a and 16b (or 16c and 16d) were installed at the openings at both ends of the internal space where balls 14 and 14 were installed. It is inevitable that the torque required to rotate the hub 7 (or 7a) (the rolling resistance of the wheel bearing rolling bearing unit) will increase. On the other hand, a structure in which one end of the internal space is closed with a cap and a seal ring is provided only on the other end in the axial direction to shut off the internal space from the external space is disclosed in, for example, As described in Japanese Patent Application Laid-Open No. 241450, it has been conventionally known.

However, in the case of a conventional rolling bearing unit for supporting a wheel, since the rotational resistance of the seal ring is not necessarily low, the rolling resistance of the rolling bearing unit for supporting a wheel cannot be sufficiently reduced. As a result, the running performance of the vehicle incorporating the wheel supporting rolling unit is deteriorated, mainly in terms of acceleration performance and fuel efficiency. Therefore, improvement is desired in response to the recent trend of energy saving. ing.

Conventionally, as a structure for reducing the rotational torque of a rolling bearing by reducing the resistance of the seal ring installation portion, a seal lip tightening as disclosed in Japanese Patent Application Laid-Open No. H10-252527 has been proposed. In addition to the devised structure, it is considered to devise the bearing type, preload amount, shape of each part, internal design such as contact angle and radius of curvature of raceway surface, type of grease, shape of seal ring, material, etc. . However, it was troublesome to design these elements in a proper manner while associating them with each other to secure the required sealing performance and to reduce the rotational torque. Therefore, it is desired to realize a structure that can more easily reduce the rotational torque of the wheel supporting rolling bearing unit.

However, even if the rotational torque is reduced, foreign matter infiltrates into the internal space of the rolling bearing unit to secure the support rigidity of the wheel to secure the steering stability and to ensure the durability of the rolling bearing unit. It is necessary to have a structure that can sufficiently prevent such problems. In other words, in order to ensure the above steering stability, it is necessary to increase the rigidity of the rolling bearing unit to secure the supporting rigidity, but simply increase the preload applied to each rolling element in order to increase the rigidity. Then, the rolling resistance of each of these rolling elements increases, The rotation torque cannot be reduced. In addition, if the only consideration is to lower the sliding resistance of the seal ring, it is not possible to sufficiently prevent foreign substances from entering the interior space of the rolling bearing unit, and the durability described above cannot be secured sufficiently. .

The rolling bearing unit for supporting wheels of the present invention has been invented in view of such circumstances. Disclosure of the invention

The rolling bearing unit for supporting a wheel of the present invention includes a stationary raceway, a rotating raceway, a plurality of balls, and a seal ring, similarly to the above-described conventionally known rolling bearing unit for supporting a wheel. And

Of these, the stationary race is supported and fixed to the suspension device in use.

In addition, the rotating raceway rings support and fix the wheels in use.

Further, each of the balls is present on the opposing peripheral surfaces of the stationary raceway ring and the rotating raceway ring. Each of the balls has a circular cross-section between the stationary raceway surface and the rotating raceway surface. It is located between them.

Further, the seal ring closes an opening at one end of a space in which the balls are installed between peripheral surfaces of the stationary raceway ring and the rotating raceway facing each other.

The seal ring has two or three seal lips, each of which is made of a resilient material.

Particularly, in the rolling bearing unit for supporting a wheel of the present invention, the axial load for applying a preload to each of the balls is 0.49 to 2.94 kN (50 to 30 Okgf).

When the axial load is 1.96 kN (20 Okgf), it is necessary to rotate the stationary raceway and the rotating raceway relative to each other at 20 Omin- ¹ based on the rolling resistance of each ball. The torque (rolling resistance) is between 0.12 and 0.23N * m.

Also, the stiffness coefficient when the axial load is 1.96 kN is 0.09 or more.

Further, based on the friction between each seal lip and the mating surface, The torque (seal resistance) required for relative rotation with the rotating side raceway at 20 Omin- ¹ is 0.03 to 0.2 N'm.

It is preferable that a sealing member be provided in addition to the seal ring to block the entire axial one-end opening of the raceway located on the outer diameter side of the stationary raceway and the rotating raceway.

The seal ring is provided on a side opposite to the sealing member in the axial direction.

The rigidity coefficient described in the present specification is defined as the rigidity R [kN-m / deg] of the wheel supporting rolling bearing unit and the radial dynamic load rating C r of the wheel supporting rolling bearing unit. This is the ratio (RZC r) to [N]. In addition, the rigidity R in this case is the above-mentioned two values when a moment load is applied to the rotating raceway while the stationary raceway constituting the wheel supporting rolling bearing unit is fixed. It is expressed by the inclination angle of the bearing ring, and is measured, for example, as shown in FIG. FIG. 14 shows a state in which the rigidity R of the wheel supporting rolling bearing unit 2a shown in FIG. 13 is measured.

During the measurement work, the outer ring 19, which is the stationary raceway, is fixed to the upper surface of the fixing base 38, and the base end of the lever plate 39 is attached to the mounting flange 11a of the hub 7a, which is the rotating raceway (Fig. 14). (The left end). Then, a load is applied to a portion of the upper surface of the lever plate 39 which is separated from the center of rotation of the above-mentioned bracket 7a by a distance L corresponding to the rotation radius of the tire. Then, a moment load of 1.5 kN'm is applied. Since the hub 7a is inclined with respect to the outer ring 19 based on the moment load, the inclination angle is determined by the inclination angle [deg] of the mounting surface 41 of the mounting flange 11a with respect to the upper surface 40 of the fixed base 38. Measured as Then, the stiffness R [kN-m / deg] is obtained by dividing the moment load (1.5 kN'm) by the inclination angle. Further, the rigidity coefficient is obtained by dividing the rigidity R by the radial dynamic load rating Cr [N] of the wheel supporting rolling bearing unit 2a.

In the case of the rolling bearing unit for supporting a wheel of the present invention configured as described above, the rotating torque can be sufficiently reduced while securing the required rigidity and durability.

That is, the axial load for applying the preload is 0.49 kN or more, When the rolling load is 1.96 kN, the rolling resistance is 0.12 Nm or more, and the stiffness coefficient is 0.09 or more. Therefore, the steering stability can be improved.

On the other hand, the axial load for applying the preload is 2.94 kN or less, the rolling resistance is 0.23 N * m or less, the rotation resistance (torque) of the seal ring is 0.2 N * m or less, Since each is suppressed, the above-described rotational torque can be reduced. If the axial load exceeds 2.94 kN, the rolling resistance cannot be kept low (for example, 0.23 N'm or less), and the rotational torque cannot be reduced. On the other hand, when the axial load is less than 0.49 kN, it becomes difficult to secure the rigidity of the wheel supporting rolling bearing unit, and the steering stability is reduced.

On the other hand, the required seal performance (mainly muddy water resistance to prevent infiltration of muddy water) can be ensured because the seal ring has a rotational resistance of at least 0.03 Nm.

That is, as a result of an experiment conducted by the inventor, as long as the number of the seal lip is two or three, regardless of the shape and material of the seal lip, regardless of the structure of the seal ring, the rotation of the seal ring is performed. It was found that the suitability of the sealing performance could be determined based on the magnitude of the resistance. At the same time, it was found that the required sealing performance could be obtained if the rotational resistance of the seal ring was set to 0.03 N'm or more.

As a result, the axial load for applying the preload is 0.49 to 2.94 kN, and when this axial load is 1.96 kN, the rolling resistance is 0.12 to 0.23 N In the case of the rolling bearing unit for supporting a wheel according to the present invention in which the coefficient is 0.09 or more and the rotation resistance of the seal ring is 0.03 to 0.2 Nm, the rotation torque is ensured while ensuring rigidity and durability. It can be understood that can be sufficiently reduced. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view showing a first example of a structure to which the present invention is applied.

FIG. 2 is a cross-sectional view showing a second example of the structure to which the present invention is applied.

Figure 3 is a half sectional view showing a third example of the subject to the structure of the present invention ₍ FIG. 4 is a half sectional view showing a fourth example of the structure to which the present invention is applied.

FIG. 5 is a partial cross-sectional view showing a first example of a specific structure of a seal ring applicable to the present invention.

FIG. 6 is a partial cross-sectional view showing a second example of the specific structure of the seal ring applicable to the present invention.

FIG. 7 is a partial cross-sectional view showing a third example of the specific structure of the seal ring applicable to the present invention.

FIG. 8 is a partial cross-sectional view showing a fourth example of the specific structure of the seal ring applicable to the present invention.

FIG. 9 is a partial cross-sectional view showing a fifth example of the specific structure of the seal ring applicable to the present invention.

FIG. 10 is a partial sectional view showing a sixth example of the specific structure of the seal ring applicable to the present invention. '

FIG. 11 is a partial sectional view showing a seventh example of the specific structure of the seal ring applicable to the present invention.

FIG. 12 is a cross-sectional view showing a first example of a conventionally known rolling bearing unit for supporting a wheel in a state where the rolling bearing unit is mounted on a suspension device.

FIG. 13 is a cross-sectional view showing a second example of a conventionally known rolling bearing unit for supporting a wheel.

FIG. 14 is a cross-sectional view showing a state in which the rigidity of the wheel supporting rolling bearing unit is measured. BEST MODE FOR CARRYING OUT THE INVENTION

First, four examples of the structure of the rolling bearing unit for supporting a wheel, which is the subject of the present invention, will be described. First, FIG. 1 shows, as a first example, a structure in which the structure shown in FIG. 12 described above is modified to make it easier to reduce the rotational torque while ensuring sealing performance. For this reason, in the case of this example, the inner inner raceway 13a is formed directly on the outer peripheral surface of the intermediate portion of the support shaft 4a. As a result, it is possible to prevent foreign matter from entering through the fitting portion between the inner inner ring 5 and the support shaft 4, which was considered in the conventional structure shown in FIG. It has a structure. Further, the outer seal ring 16a, which is incorporated in the conventional structure shown in FIG. 12, is omitted, and only the inner seal ring 16b is provided.

When the present invention is applied to such a structure, the preload is applied to the balls 14, 14 by appropriately regulating the torque for tightening the nut 6 screwed to the outer end of the support shaft 4a. The axial load to be applied shall be 0.49 to 2.94 kN. When the axial load is 1.96 kN, the torque (rolling resistance) required to rotate the hub 7 around the support shaft 4a at 20 OmiiT ¹ is 0.12 to 0.23N '. m. In addition, the stiffness coefficient when the axial load is 1.96 kN is set to 0.09 or more. Further, the rotation resistance (torque) of the inner seal ring 16 is regulated in the range of 0.03 to 0.2 N * m. To prevent foreign matter such as muddy water from entering the space in which the balls 14 and 14 are installed, a sealing member other than the seal ring 16 b and the seal ring attached to the outer end opening of the hub 7 is used. This is prevented by cap 17. 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 rolling bearing unit for supporting a wheel, which is an object of the present invention. While the structure shown in FIG. 1 described above fixes the inner ring 5 with a nut 6 screwed to the outer end of the support shaft 4a, in this example, the outer end of the support shaft 4b is The outer end surface of the inner race 5 is held down by a caulking portion 25 that is plastically deformed in the outward direction, and the inner race 5 is fixed to the support shaft 4b. The axial load for applying the preload is adjusted by the load at the time of processing the caulking portion 25. The structure of the other parts is the same as in the first example described above.

Next, FIG. 3 shows a third example of a rolling bearing unit for supporting a wheel, which is an object of the present invention. In this example, the structure shown in FIG. 13 is changed to a structure to which the present invention can be applied. For this reason, in the case of this example, the inner end opening of the outer ring 19 is closed with a cap 17a which is a sealing member other than the seal ring, and the inner peripheral surface of the outer end of the outer ring 19 and the outer peripheral portion of the intermediate portion of the hub body 22. The surface is closed with a seal ring 16c. The sealing 16d (FIG. 13) between the inner peripheral surface of the inner end of the outer ring 19 and the outer peripheral surface of the inner ring 23 is omitted. The rotation resistance of the seal ring 16c is regulated in the range of 0.03 to 0.2 N · m. Each ball 14, 14 installed The seal ring 16c and the cap 17a prevent the foreign matter such as muddy water from entering the space. The axial load for applying the preload is adjusted by the load at the time of processing the caulked portion 25. The structure of the other parts is the same as the first and second examples described above and the conventional structure shown in FIG.

Next, FIG. 4 shows a fourth example of a rolling bearing unit for supporting a wheel, which is an object of the present invention. In the case of this example, the inner ring 2 externally fitted to the small-diameter stepped portion 24 of the hub main body 2 2a by a nut 27 screwed to the male screw portion 26 provided at the inner end of the hub main body 22a. The inner end face of 3 is held down. In accordance with this, the shape of the cap 17 b, which is a sealing member other than the seal ring attached to the inner end opening of the outer ring 19, is expanded to prevent interference with the male screw part 26 and the nut 27. I have. The axial load for applying the preload is adjusted by the torque for tightening the nut 27. Other configurations are the same as those of the above-described second example.

Next, seven examples of the specific structure of the seal ring applicable to the present invention will be described with reference to FIGS. Of these, the five examples shown in Figs. 5 to 9 are the first and second examples of the rolling bearing unit for wheel support shown in Figs. 1 and 2 above, and have a structure that can be used as the inner seal ring 16b. Is shown.

First, the first example shown in FIG. 5 includes an outer-diameter-side seal ring 28 that is fitted and fixed to the inner end of the hub 7 (FIGS. 1 and 2), and the support shafts 4a (FIG. 1) and 4b ( This is a combination seal ring that combines the inner side seal ring 29 that is externally fitted and fixed to the inner end portion of Fig. 2) .Two total seal lips, two on the inner side and one on the outer side Is provided. In the case of such a structure, conventionally, the torque (rotational resistance) required for the relative rotation between the outer diameter side and the inner diameter side seal rings 28, 29 was 0.22 N'm or more. On the other hand, when the structure of this example is applied to the present invention, the outer diameter side and the inner diameter based on the friction between the leading edges of the three seal lips and the mating surface (the surface of the metal core). The torque (rotational resistance) required for the relative rotation between the two sealing rings 28, 29 is restricted to the range of 0.03 to 0.2 Nm.

Next, in the second example shown in FIG. 6, a seal ring 30 that is fitted and fixed to the inner end of the hub 7 (FIGS. 1 and 2), and the support shafts 4a (FIG. 1) and 4b (FIG. 2) is a combination seal ring in which a slinger 31 fixed externally to the portion near the inner end of Ring 30 with three sealing lips. In the case of this example, the sealing ring is formed based on the friction between the leading edges of the three sealing lips and the surface of the slinger 31.

The torque (rotational resistance) required for relative rotation between the slinger 30 and the slinger 31 is restricted to a range of 0.03 to 0.2 N · m.

Next, in the third example shown in FIG. 7, the seal ring 30a for internally fitting and fixing to the inner end of the hub 7 (FIGS. 1-2) is one of the two seal lips 32a and 32b. The seal lip 32a on the inside of the support shaft 4a (FIG. 14b (FIG. 2)) is slid in contact with the outer peripheral surface of the portion near the inner end of the support shaft 4a (FIG. 14b (FIG. 2). The seal ring 30a and the support shafts 4a and 4b are formed based on the friction between the tip edges of the two seal lips 32a and 32b and the outer peripheral surface of the portion near the inner ends of the support shafts 4a and 4b. The torque (rotational resistance) required for relative rotation is restricted to the range of 0.03 to 0.2 N * m.

Next, in a fourth example shown in FIG. 8, a seal ring 34a that locks on the inner peripheral surface of the inner end of the hub 7 (FIGS. 1 and 2), and the support shafts 4a (FIG. 1) and 4b (FIG. ) Is a combination seal ring that combines a seal ring 34b that locks to the outer peripheral surface of the portion near the inner end of (). In the case of this example, two seal rings 34a that lock to the hub 7 side,

4 A seal ring 34b that locks to the b side has one seal lip, one in total. In the case of this example, based on the friction between the leading edge of these three seal lips and the mating surface, the inner peripheral surface of the bush 7, the outer peripheral surfaces of the support shafts 4a and 4b, and the surface of the core metal, The torque (rotational resistance) required for the relative rotation between the hub 7 and the support shafts 4a, 4b is 0.03 to 0.3.

Restrict to the range of 2N · m.

Next, FIG. 9 shows that the front edges of the two seal lips provided on the seal ring 35 fitted inside the inner end of the hub 7 (FIGS. 1-2) are supported by the support shaft 4a (FIG. 14b (FIG. 2)). In this case, the outer edges of the two seal lips and the inner ends of the support shafts 4a and 4b are in contact with each other. The torque (rotational resistance) required for the relative rotation between the seal ring 35 and the support shaft 4a based on the friction is

Restrict within the range of 0.03 to 0.2N · m.

Next, the two examples shown in FIGS. 10 and 11 are the third and fourth examples of the wheel supporting rolling bearing unit shown in FIGS. 3 and 4, respectively, and the inner peripheral surface of the outer end of the outer ring 19 (FIGS. 3 and 4). And hub body This figure shows a structure that can be used as a seal ring provided between the outer peripheral surface of the intermediate portion 22 (FIG. 3) and 22a (FIG. 4). First, the seal ring of the first example shown in FIG.

36 has three seal lips on a metal core that can be fitted and fixed inside the outer end of the outer ring 19, and the leading edge of each seal lip is attached to the mounting flange 11a (Figs. 3 and 4). The inner surface or a curved surface that connects the inner surface to the outer peripheral surface of the hub body 22, 22a can be slidably contacted. In the case of this example, the relative rotation between the sealing ring 36 and the hub bodies 22, 22a based on the friction between the tip edges of the three sealing lips and the surfaces of the hub bodies 22, 22a. Torque (rotational resistance) required in the range of 0.03 to 0.2 N · m.

Next, in the case of the second example shown in FIG. 11, the middle seal lip 37 of the three seal lips provided on the seal ring 36a is connected to the hub body by the spring 33a. 22 (Fig. 3) and 22a (Fig. 4) are pressed against the outer peripheral surface. In the case of this embodiment as well, the relative rotation between the seal ring 36a and the hub bodies 22, 22a based on the friction between the tip edges of the three seal lips and the surfaces of the hub bodies 22, 22a. Torque (rotational resistance) required in the range of 0.03 to 0.2 N'm. Example

Next, the results of experiments performed to confirm the effects of the present invention will be described. In the first experiment, for the seven types of seal rings shown in Figs. 5 to 11, the relationship between the rotational resistance (seal torque) of the seal ring alone and the seal performance was determined. Adjustment of the seal torque was performed by adjusting the interference (the amount of elastic deformation) of the seal lip, changing the elastic material, and adjusting the state of contact with the opposite surface. For each of the above seven types of seal rings, six types with seal torques from 0 to 0.22 Nm were manufactured. Then, each seal ring was assembled into a wheel supporting rolling bearing unit shown in FIG. 1 or FIG. 3 and subjected to a muddy water intrusion test. Lubrication of the wheel supporting rolling bearing Interview two Tsu DOO is performed by a viscosity encapsulating grease ^{10~14 c S t (10X 10- 6} ~14X 10- 6 m 2 / s), an environment of 20 Then, the hubs 7 and 7a were rotated at 20 Omin- ¹ . Table 1 shows the results of the experiment conducted under these conditions.

[table 1 ]

In Table 1, the mark “X” indicates that a large amount of muddy water has infiltrated the interior space filled with grease, the mark “△” indicates that a small amount of muddy water has penetrated, and the mark “〇” indicates that muddy water has penetrated. Indicates that was not observed. From the results of such experiments, it can be seen that muddy water can be prevented from infiltrating with any structure of seal ring if the seal torque is 0.03 N · m or more.

Next, to understand the effects of seal torque (rotational resistance), axial load for applying preload, rolling resistance, and stiffness coefficient on steering stability, rotational torque, and durability of the entire rolling bearing unit. The second to fifth experiments performed by incorporating the seal ring 36 shown in FIG. 10 into the wheel supporting rolling bearing unit shown in FIG. 10 will be described with reference to Tables 2 to 5. In Tables 2 to 5 below, the symbol “X” indicates that some problem occurred in some aspects, the symbol “△” indicates that some problem occurred in some aspects, and the symbol “〇” indicates It indicates that no problem occurred from any aspect. The second to fifth experiments were performed three times under the same conditions.

First, Table 2 shows the results of a second experiment performed to determine the effect of the sealing torque on the rotation torque and durability of the entire rolling bearing unit. This experiment was performed at a rotation speed of 20 O min- ¹ . [Table 2]

As a result of the second experiment shown in Table 2, if the above-mentioned sealing torque is in the range of 0.03 to 0.20 m, the rolling bearing unit is satisfactory in terms of both rotational torque and durability. I found that I could get the performance I could. On the other hand, when the above-mentioned shield is 0.0 IN m and 0.02 Nm, foreign matters cannot be sufficiently prevented from entering the interior space where the balls 14, 14 are installed, and the durability is high. A problem arose in terms of security. On the other hand, when the sealing torque was 0.22 N · m and 0.25 N · m, the rotation torque of the entire rolling bearing unit could not be suppressed sufficiently. Next, Table 3 shows the results of a third experiment performed to determine the effect of the axial load (preload) on the stiffness of the rolling bearing unit and the overall rotational torque.

[Table 3]

As a result of the third experiment shown in Table 3, if the above-mentioned axial load is 0.49 to 2.94 kN, satisfactory performance can be obtained from both aspects of steering stability and rotational torque of the entire rolling bearing unit. I found that I could get it. On the other hand, when the axial load was 0.294 kN and 0.392 kN, the rigidity of the rolling bearing unit was low, and sufficient steering stability could not be secured. On the other hand, when the axial load was 3.43 kN and 3.92 kN, the rolling resistance was high, and the rotational torque of the entire rolling bearing unit could not be suppressed sufficiently. Next, Table 4 shows the results of a fourth experiment performed to determine the effect of the rolling resistance on the rigidity of the rolling bearing unit and the overall rotational torque. This experiment was performed with an axial load (preload) of 1.96 kN (200 kgf) and a rotation speed of SO Omin- ¹ .

[Table 4]

As a result of the fourth experiment shown in Table 4, if the above-mentioned rolling resistance is 0.12 to 0.23 mm, the steering stability and the rolling torque of the entire rolling bearing unit can be satisfied. It turns out that performance can be obtained. In contrast, when the rolling resistance was 0.1 N · m or 0.11 N · m, the rigidity of the rolling bearing unit was low, and sufficient steering stability could not be secured. On the other hand, when the rolling resistance was 0.24 N'm and 0.25 N · m, the rotation torque of the entire rolling bearing unit could not be suppressed sufficiently.

Further, Table 5 shows the results of a fifth experiment conducted to determine the effect of the rigidity coefficient on the rigidity of the rolling bearing unit. This experiment was performed with an axial load of 1.96 kN applied.

[Table 5]

As a result of the fifth experiment shown in Table 5, it was found that if the stiffness coefficient was 0.09 or more, satisfactory performance in terms of steering stability could be obtained. On the other hand, when the rigidity coefficients were 0.07 and 0.08, the rigidity of the rolling bearing unit was low, and sufficient steering stability could not be secured.

Further, Table 6 below shows the results of an experiment conducted to find out the effect of the sealing torque and the rolling resistance on the rotation torque of the rolling bearing unit as a whole. This experiment was performed at an axial load (preload) of 1.96 kN (20 Okgf) and a rotation speed of 200 min- ¹ .

[Table 6]

In Table 6, “X” indicates that the rotation torque was large as a whole, “△” indicates that it was slightly large, and “〇” indicates that it was small. This As is clear from Table 6, the present invention, in which the sealing torque is suppressed to 0.2Νππ or less and the rolling resistance is suppressed to 0.23Νm or less, the rotational torque as a whole is 0.43Νm or less. , Can be kept low. Industrial applicability

Since the rolling bearing unit for supporting a wheel according to the present invention is configured and operates as described above, the steering torque and the rotating torque of the hub that rotates with the wheel are reduced while maintaining the steering stability and durability, thereby improving the acceleration performance. However, it can contribute to the improvement of the running performance of vehicles mainly on fuel efficiency.

Claims

The scope of the claims

1. A stationary raceway that is supported and fixed to the suspension device in use, a rotating raceway that supports and fixes the wheels in use, and the facing surfaces of the stationary raceway and the rotating raceway facing each other A plurality of balls provided between the stationary-side raceway surface and the rotating-side raceway surface each having an arc-shaped cross section, and the stationary-side raceway and the rotating-side raceway facing each other. A seal ring for closing the opening at one end of the space where the balls are installed between the peripheral surfaces, the seal ring having two to three seal lips each made of an elastic material. In a rolling bearing unit for supporting a wheel, the axial load for applying a preload to each of the above balls is 0.49 to 2.94 kN, and when the axial load is 1.96 kN, Based on the rolling resistance of the ball, the stationary race and the rotation The torque required to rotate the side bearing ring relative to the side raceway at 20 Omin- ¹ is 0.12 to 0.23 Nm, and the stiffness coefficient is 0.09 when the axial load is 1.96 kN. The torque required to relatively rotate the stationary raceway ring and the rotating raceway ring at 200 min- ¹ based on the friction between the respective seal lip and the mating surface is 0.03-0. A rolling bearing unit for supporting wheels, characterized in that it is 2N'm.

2. Claim 1 further comprising a sealing member other than a seal ring for closing the entire axial one end opening of the raceway located on the outer diameter side of the stationary raceway and the rotation raceway. The rolling bearing unit for supporting wheels described in the above item.