JP2023154326A - Wheel bearing device - Google Patents

Abstract

To provide a wheel bearing device which prevents internal grease from being discharged along with air from a sealed space to the external space of the bearing due to positive pressure and negative pressure which are generated in the sealed space, and also prevents seal lips from adhering to the sliding surface and increasing friction torque, thereby contributing to reduced torque.SOLUTION: A wheel bearing device comprises a ventilation mechanism 8 for maintaining a bearing internal space A at atmospheric pressure. The ventilation mechanism 8 has a ventilation hole 8a opened toward the bearing internal space A, and taking in and discharging air in the bearing internal space A, and a ventilation pipe 8b connected to the ventilation hole 8a. Sealing devices (6, 7) have first seal lips (64a, 64b, 72a and 72b) for preventing the intrusion of foreign matter from a bearing external space B, and second seal lips (64c, 72c) for sealing grease into the bearing internal space A. The stiffness of the second seal lips (64c, 72c) is set lower than that of the first seal lips (64a, 64b, 72a and 72b).SELECTED DRAWING: Figure 1

Description

The present invention relates to a wheel bearing device.

BACKGROUND ART Wheel bearing devices that rotatably support wheels have been known. In such a wheel bearing device, an outer member is fixed to the vehicle body. Further, an inner member is disposed inside the outer member, and a plurality of rolling elements are interposed between raceway surfaces of the outer member and the inner member. In this way, the wheel bearing device constitutes a rolling bearing structure, and allows the wheel attached to the inner member to freely rotate.

By the way, in such a wheel bearing device, a bearing internal space is formed between the outer member and the inner member, so that foreign matter (muddy water, dust, etc.) cannot enter the bearing internal space, or the inside of the bearing can be damaged. There is a possibility that the grease sealed in the space (hereinafter referred to as internal grease) may leak. Therefore, the wheel bearing device includes an inner sealing device and an outer sealing device to close both open ends of the bearing internal space. In wheel bearing devices, when the internal pressure of the bearing internal space changes, there is a risk that the seal lip will stick to the sliding surface and friction torque will increase. The hub unit bearing (wheel bearing device) of Patent Document 1 has the following three structures in order to suppress internal pressure changes in the internal space (bearing internal space) including the sealed space (space surrounded by the seal lip). ing.

The first structure is a structure in which a vent hole and a pressure sensor are provided inside the outer ring, and an air supply pipe (vent pipe) leading to an atmosphere opening, a compressed air supply source, and a controller is connected to the vent hole. The controller sends an appropriate amount of air from the compressed air supply through the air pipe into the interior space when the pressure sensor senses negative pressure. Thereby, the hub unit bearing can always maintain the internal space at atmospheric pressure or positive pressure.

The second structure is such that a ventilation hole is provided inside the hub wheel of the driven wheel to connect the internal space and the external space (bearing external space). Inside the hub ring, a pressure spring and a piston are provided in order from the outside in the radial direction. A vent hole is provided on the radially outer side of the side surface of the cylinder where the piston slides, mediating an inner air passage leading to a ventilation hole in the inner space and an outer air passage leading to a ventilation hole in the outer space. . A vent hole communicating with the external space is provided on the radially inner bottom surface of the cylinder, and the space inside the cylinder in the radial direction is always kept at the same pressure as atmospheric pressure.

During operation, the piston moves radially outward against the pressing force of the pressing spring due to centrifugal force, thereby closing the vent hole on the side surface of the cylinder. When stopped, the centrifugal force disappears, and the piston moves radially inward due to the pressing force of the pressing spring, opening the ventilation hole on the side of the cylinder. Air flows into the interior space through pores, interior air channels, and ventilation holes in the interior space. Thereby, the hub unit bearing can always maintain the internal space at atmospheric pressure or positive pressure.

The third structure is such that a ventilation hole is provided inside the hub wheel of the driven wheel to connect the internal space and the external space. Inside the hub ring, a pressure spring and a piston are provided in order from the outside in the radial direction. A ventilation hole is provided on the radially inner bottom surface of the cylinder, and is connected to the air path (first air path, second air path, third air path) leading to the internal space ventilation hole and the external space ventilation hole. ing. A first check valve and a second check valve are provided in the axial direction of the air passage so as to form a closed space between the radially inner side of the cylinder and the air passage.

During operation, the piston within the cylinder moves radially outward against the pressing force of the pressing spring due to centrifugal force, and the internal pressure of the internal space becomes higher than atmospheric pressure. When the internal pressure of the internal space becomes higher than atmospheric pressure, the second check valve closes, and communication between the internal space and the external space (second closed space) is cut off. When stopped, the centrifugal force disappears, and the piston moves radially inward due to the pressing force of the pressing spring, and the internal pressure of the internal space becomes lower than atmospheric pressure. When the internal pressure of the internal space becomes lower than atmospheric pressure, both the first check valve and the second check valve open, and the internal space and the external space (second closed space) are brought into communication. Thereby, the hub unit bearing can always maintain the internal space at atmospheric pressure or positive pressure. With the above three structures, the hub unit bearing always maintains the internal space at atmospheric pressure or positive pressure, prevents the seal lip from adhering to the sliding surface, and suppresses an increase in frictional torque.

However, although the first structure is relatively simple, it requires separate design of external devices such as a controller and a pressurized air supply source, as well as the power required to operate the external devices and the prevention of lip adsorption. Compared to the energy secured by reducing friction torque, it may not be effective in improving the energy efficiency of the entire vehicle. Furthermore, the internal space is made to have positive pressure to allow air to leak into the external space, but at the same time internal grease may be released into the external space and the performance of the sealing device may deteriorate due to poor lubrication. There are also concerns.

The second and third structures require a plurality of holes (cylinders, air passages) to be provided in the hub ring, and require high precision especially on the sliding surfaces of the piston and cylinder, which requires a lot of man-hours. In addition, since the structure uses springs, it is necessary to take into consideration the resonance phenomenon of the springs due to changes in the rotational speed when designing, and it is thought that a considerable amount of time and cost will be required to put it into practical use. Further, dust and the like may be sucked in from the external space through the ventilation holes of the hub ring (external space), which may shorten the life of the bearing.

JP2020-118222A

In conventional wheel bearing devices, the bearing internal space a (see Figure 3) and the sealed spaces c, d, e, and f (see Figure 3) are in a sealed state, so air leakage occurs due to the rise in bearing temperature during driving. The expansion creates positive pressure in the sealed spaces c, d, e, f. As a result, a pressing force acts on the lip surface and sliding surface in contact with the sealed spaces c, d, e, and f, and the tip of the lip is lifted radially outward, creating a gap between the seal lip and the sliding surface. air leaks into the external space of the bearing. At this time, there is a possibility that the internal grease may be released into the external space of the bearing, and there is also concern that the performance of the sealing device may deteriorate due to poor lubrication. When the vehicle is stopped, negative pressure is generated in the sealed spaces c, d, e, and f due to air contraction due to a decrease in bearing temperature. As a result, the seal lip deforms inward in the radial direction, causing the seal lip to stick to the sliding surface (see FIG. 3), resulting in an increase in frictional torque.

Therefore, in the present invention, internal grease is released from the seal space together with air into the external space of the bearing due to the positive and negative pressures generated in the seal space, and the seal lip is attracted to the sliding surface to generate friction torque. To provide a wheel bearing device that can prevent an increase in torque and contribute to lower torque.

That is, the first invention includes an outer member having a double row outer raceway surface on the inner periphery;
an inner member having a double-row inner raceway surface facing the double-row outer raceway surface;
a double row of rolling elements rotatably housed between raceway surfaces of the outer member and the inner member;
a sealing device that closes an open end of a bearing internal space formed by the outer member and the inner member;
A wheel bearing device comprising: a rotation sensor that detects the rotational speed of a rotating member of the outer member and the inner member,
The rotation sensor includes a ventilation hole that maintains the bearing interior space at atmospheric pressure by taking in and exhausting air in the bearing interior space, and a ventilation pipe connected to the ventilation hole,
comprising a ventilation mechanism that maintains the internal space of the bearing at atmospheric pressure;
The ventilation mechanism includes a ventilation hole that opens toward the bearing internal space and takes in and exhausts air in the bearing internal space, and a ventilation pipe connected to the ventilation hole,
The sealing device has a first seal lip that prevents foreign matter from entering the bearing external space, and a second seal lip that seals grease in the bearing internal space,
The second seal lip has lower rigidity than the first seal lip.

The present invention has the following effects.

That is, according to the first invention, internal grease is discharged from the sealing space together with air into the external space of the bearing due to the positive pressure and negative pressure generated in the sealing space, and the seal lip is attracted to the sliding surface. This prevents friction torque from increasing and contributes to lower torque.

FIG. 2 is a sectional view showing a wheel bearing device. II-II cross-sectional view of the wheel bearing device in Figure 1 FIG. 1 is a sectional view showing a conventional wheel bearing device.

The overall configuration of a wheel bearing device 1 will be described using FIG. 1. In the following description, the inner side refers to the vehicle body side of the wheel bearing device 1 when attached to the vehicle body, and the outer side refers to the wheel side of the wheel bearing device 1 when attached to the vehicle body. . The axial direction refers to a direction along the rotation axis R of the wheel bearing device 1. The radial direction refers to a direction perpendicular to the rotation axis R of the wheel bearing device 1. The circumferential direction refers to a direction along an arc centered on the rotation axis R of the wheel bearing device 1.

The wheel bearing device 1 rotatably supports a wheel in a suspension system of a vehicle such as an automobile. The wheel bearing device 1 includes an outer ring 2, a hub ring 3, an inner ring 4, rolling elements 5, an inner sealing device 6, an outer sealing device 7, a ventilation mechanism 8, and a rotation sensor 9. .

An outer ring 2, which is an outer member, supports a hub ring 3 and an inner ring 4. The inner peripheral surface of the inner end 2a of the outer ring 2 is provided with a fitting surface 2b into which the inner sealing device 6 is fitted. The inner peripheral surface of the outer end 2c of the outer ring 2 is provided with a fitting surface 2d into which the outer sealing device 7 is fitted. A vehicle body attachment flange (not shown) is integrally provided on the outer peripheral surface 2e of the outer ring 2.

The inner member is composed of a hub ring 3 and an inner ring 4. The hub wheel 3 rotatably supports a wheel of a vehicle (not shown). At the inner end of the outer circumferential surface of the hub ring 3, a small-diameter stepped portion 3a that extends in the axial direction and has a reduced diameter is provided. A wheel attachment flange 3b for attaching a wheel is integrally provided at the outer end of the hub wheel 3. A hub bolt 3c for fastening the hub wheel 3 and a wheel or a brake device is press-fitted into the wheel attachment flange 3b. Alternatively, a tapped hole for fastening a hub bolt may be provided in the wheel mounting flange 3b. Further, on the outer peripheral surface of the hub ring 3, an inner raceway surface 3d is provided that faces the outer raceway surface 2h. That is, on the outer side of the inner member, the hub ring 3 forms an inner raceway surface 3d. A sliding surface 3e on which the outer sealing device 7 slides is provided on the base side of the wheel attachment flange 3b of the hub wheel 3. In the hub wheel 3, an annular encoder 3f whose outer peripheral surface serves as a detection surface is fitted between an inner rolling element 5 and an outer rolling element 5.

The inner ring 4 is press-fitted into the small diameter stepped portion 3a of the hub ring 3. The inner ring 4 applies preload to the rolling elements 5. The outer peripheral surface of the inner ring 4 is provided with an inner raceway surface 4a that faces the inner outer raceway surface 2g. That is, on the inner side of the inner member, the inner ring 4 forms an inner raceway surface 4a. Furthermore, a fitting surface 4b into which the inner sealing device 6 is fitted is provided on the outer peripheral surface of the inner end 4c of the inner ring 4.

The rolling elements 5 are composed of balls. The inner rolling elements 5 and the outer rolling elements 5 are each held by a retainer 51. The inner rolling elements 5 are sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner outer raceway surface 2g of the outer ring 2 in a freely rolling manner. The outer rolling element 5 is rotatably sandwiched between the inner raceway surface 3d of the hub ring 3 and the outer raceway surface 2h of the outer ring 2. In other words, the inner rolling elements 5 and the outer rolling elements 5 are rotatably housed between the raceway surfaces of the outer member and the inner member. In this manner, in the wheel bearing device 1, the outer ring 2, the hub ring 3, the inner ring 4, and the double row rolling elements 5 constitute a double row angular contact ball bearing. Note that the wheel bearing device 1 may include a double-row tapered roller bearing instead of the double-row angular ball bearing.

The inner sealing device 6 and the outer sealing device 7, which are sealing devices, close the open end of the bearing internal space A formed by the outer member and the inner member.

The inner sealing device 6 includes a slinger 61 and a seal ring 62. The slinger 61 has a cylindrical fitting portion 61a and a disk-shaped side plate portion 61b extending radially outward from the fitting portion 61a. The fitting portion 61a is fitted to the fitting surface 4b of the inner ring 4. On the other hand, the seal ring 62 has an elastic member 64 fixed to a core metal 63. The core metal 63 has a cylindrical fitting portion 63a and a disk-shaped side plate portion 63b extending radially inward from the fitting portion 63a. The fitting portion 63a is fitted to the fitting surface 2b of the outer ring 2. The elastic member 64 is formed with side lips 64a and 64b, and the tip of each lip is in contact with the sliding surface 61d of the side plate portion 61b of the opposing slinger 61. Furthermore, a grease lip 64c is formed on the elastic member 64, and the tip of the lip contacts or is close to the sliding surface 61c of the fitting portion 61a of the opposing slinger 61.

The outer sealing device 7 includes a core metal 71 and an elastic member 72. In the outer sealing device 7, an elastic member 72 is fixed to a core metal 71. The core metal 71 has a cylindrical fitting portion 71a and a disk-shaped side plate portion 71b extending radially inward from the fitting portion 71a. The fitting portion 71a is fitted to the fitting surface 2d of the outer ring 2. A side lip 72a is formed on the elastic member 72, and the tip of the lip contacts the sliding surface 3e of the hub wheel 3. Further, the elastic member 72 is formed with an intermediate lip 72b, the tip of which is in contact with the sliding surface 3e of the hub wheel 3. Furthermore, a grease lip 72c is formed on the elastic member 72, and the tip of the lip contacts or is close to the sliding surface 3e of the hub wheel 3.

Next, the features and effects of the wheel bearing device 1 will be described using FIGS. 1 and 2. The first seal lip in the present application is constituted by the side lips 64a and 64b, the side lip 72a, and the intermediate lip 72b, and prevents foreign matter from entering from the bearing external space B. The second seal lip in the present application is constituted by a grease lip 64c and a grease lip 72c, and seals the grease in the bearing internal space A.

The wheel bearing device 1 includes a ventilation mechanism 8 provided in a rotation sensor 9. The ventilation mechanism 8 maintains the bearing internal space A at atmospheric pressure. The ventilation mechanism 8 includes one or more ventilation holes 8a, a ventilation pipe 8b connected to the ventilation hole 8a, and a filter 8c connected to an end of the ventilation pipe 8b. Note that the object to which the ventilation mechanism 8 is provided is not limited to the rotation sensor 9, and may be provided to other sensors.

The rotation sensor 9 detects the rotation speed of the rotating member of the outer member (outer ring 2) and the inner member (hub ring 3 and inner ring 4). In this embodiment, the rotation sensor 9 is an ABS sensor whose rotating members are the hub wheel 3 and the inner wheel 4, and which detects the rotational speed of the wheels for controlling an ABS (anti-lock brake system). The rotation sensor 9 passes through the outer ring 2 in the radial direction, and is provided facing a detection surface formed from the outer peripheral surface of the encoder 3f.

The ventilation hole 8a is formed to open toward the bearing internal space A, and takes in and exhausts air in the bearing internal space A. The ventilation pipe 8b communicates with the bearing external space B through the filter 8c, and keeps the bearing internal space A at atmospheric pressure at all times. The ventilation hole 8a is connected to a ventilation pipe 8b, and the ventilation pipe 8b is guided into the vehicle interior together with the wiring 9a of the rotation sensor 9. The ventilation pipe 8b is separated from the wiring 9a of the rotation sensor 9 inside the vehicle, and is connected to a filter 8c that separates the bearing external space B from the ventilation pipe 8b. The filter 8c takes in and exhausts air in the bearing external space B, and also prevents the intrusion of foreign substances that are harmful to the function of the bearing.

Next, the features and effects of the inner sealing device 6 will be explained.

The side lips 64a and 64b extend from upstream to downstream with respect to the outflow direction of air when air leaks from the bearing internal space A to the bearing external space B. The grease lip 64c extends from downstream to upstream and is in contact with the bearing internal space A with respect to the outflow direction of air when air leaks from the bearing internal space A to the bearing external space B. The grease lip 64c has lower rigidity than the side lips 64a and 64b and is easily deformed. Note that the seal lip may be one in which at least one first seal lip and at least one second seal lip are formed and extend in the above-mentioned extension direction, and the shape and number of the seal lips are limited to the specifications of the present application. isn't it.

When positive pressure is gradually generated in the sealed spaces C and D due to air expansion due to a rise in the temperature of the bearing, or when an instantaneous positive pressure increases in the sealed spaces C and D due to shock during assembly. When this occurs, a pressing force acts on the lip surfaces and sliding surfaces 61c and 61d that are in contact with the sealed spaces C and D. Here, the bearing external space B is at atmospheric pressure with respect to the seal sealed space C, and the bearing internal space A is at atmospheric pressure with respect to the seal sealed space D.

Since the grease lip 64c is more easily deformed than the side lips 64a and 64b, a gap between the grease lip 64c and the sliding surface 61c opens, and the air in the sealed space D is discharged into the bearing internal space A. As a result, the sealing space D becomes a negative pressure with respect to the sealing space C, so that a force that pulls the side lip 64b toward the sealing space D side acts to cancel out the positive pressure in the sealing space C. This allows the air in the sealed space C to be discharged into the bearing external space B from the gap between the side lip 64a and the sliding surface 61c, and at the same time prevents internal grease from being discharged into the bearing external space B. Furthermore, compared to conventional wheel bearing devices, the total amount of air leaking from the sealed spaces C and D can be suppressed to a low level, thereby suppressing the increase in torque due to lip adsorption.

Next, the features and effects of the outer sealing device 7 will be explained.

The side lip 72a and the intermediate lip 72b extend from upstream to downstream with respect to the outflow direction of air when air leaks from the bearing internal space A to the bearing external space B. The grease lip 72c extends from downstream to upstream and is in contact with the bearing internal space A with respect to the outflow direction of air when air leaks from the bearing internal space A to the bearing external space B. The grease lip 72c has lower rigidity and is more easily deformed than the side lip 72a and the intermediate lip 72b.

When positive pressure is gradually generated in the sealed spaces E and F due to air expansion due to a rise in the temperature of the bearing, or when an instantaneous increase in positive pressure occurs in the sealed spaces E and F due to shock during assembly. When this occurs, a pressing force acts on the lip surface and sliding surface 3e that are in contact with the sealed spaces E and F. Here, the bearing external space B is at atmospheric pressure with respect to the sealing space E, and the bearing internal space A is at atmospheric pressure with respect to the sealing space F.

Since the grease lip 72c is more easily deformed than the side lip 72a and the intermediate lip 72b, a gap is opened between the grease lip 72c and the sliding surface 3e, and the air in the sealed space F is discharged into the bearing internal space A. As a result, the seal space F has a negative pressure with respect to the seal space E, so a force that pulls the intermediate lip 72b toward the seal space F side acts to cancel out the positive pressure in the seal space E. This allows the air in the sealed space E to be discharged into the bearing external space B from the gap between the side lip 72a and the sliding surface 3e, and at the same time prevents internal grease from being discharged into the bearing external space B. Furthermore, compared to conventional wheel bearing devices, the total amount of air leaking from the seal-sealed spaces E and F can be suppressed to a low level, so that an increase in torque due to lip adsorption can be suppressed.

According to the wheel bearing device 1 configured as described above, by providing the conventional ABS sensor with the ventilation hole 8a and the ventilation pipe 8b, the bearing internal space A is maintained at atmospheric pressure, and the sealed spaces C, D, Depending on the pressure difference between E and F, air can flow out from the seal-sealed spaces D and F to the bearing internal space A. As a result, the pressure inside the seal spaces C, D, E, and F can be adjusted without using an external device (there is no energy loss due to the operation of the external device), preventing internal grease from leaking to the outside, and preventing the seal lip from leaking. By suppressing adsorption of the sliding surfaces (64a, 64b, 64c, 72a, 72b, 72c) to the sliding surfaces (3e, 61c, 61d), the inherent performance of the sealing device can be brought out.

That is, in the wheel bearing device 1, internal grease is released together with air from the sealed spaces C, D, E, and F into the bearing external space B due to the positive and negative pressures generated in the sealed spaces C, D, E, and F. This prevents the seal lips (64a, 64b, 64c, 72a, 72b, 72c) from adhering to the sliding surface (3e, 61c, 61d) and increasing friction torque, contributing to lower torque. . In addition, the wheel bearing device 1 is a conventional built-in ABS sensor with a ventilation hole 8a and a ventilation pipe 8b, and since it operates by utilizing the environment that may occur when the vehicle is running, it has the above three structures. Compared to other products, it has a lead in terms of feasibility, energy efficiency, and grease leakage prevention. Further, in the wheel bearing device 1, since the ventilation pipe 8b is connected to the filter 8c, it is possible to prevent dust and the like from being sucked into the bearing internal space A from the bearing external space B, and thereby reducing the bearing life.

The wheel bearing device 1 of each embodiment has been described above as a wheel bearing device 1 with a third generation structure of inner ring rotation in which the inner raceway surface 3d of the rolling element 5 is directly formed on the outer periphery of the hub ring 3. The present invention is not limited to this, and for example, a second generation structure in which a pair of inner rings 4 are press-fitted and fixed to the hub ring 3 and has a rotating inner ring may be used. Moreover, a third generation structure or a second generation structure with outer ring rotation may be used. Further, the above-described embodiments merely show typical forms of the present invention, and various modifications can be made without departing from the gist of the present invention.

1 Wheel bearing device 2 Outer ring (outer member)
2g Outer raceway surface 2h Outer raceway surface 3 Hub ring (inner member)
3a Small diameter stepped portion 3d Inner raceway surface 4 Inner ring (inner member)
4a Inner raceway surface 6 Inner side sealing device 64a Side lip (first seal lip)
64b Side lip (first seal lip)
64c Grease lip (second seal lip)
7 Outer side sealing device 72a Side lip (first seal lip)
72b Intermediate lip (first seal lip)
72c Grease lip (second seal lip)
8 Ventilation mechanism 8a Ventilation hole 8b Ventilation pipe 8c Filter 9 Rotation sensor 9a Wiring A Bearing internal space B Bearing external space

Claims (4)

an outer member having a double-row outer raceway surface on the inner periphery;
an inner member having a double-row inner raceway surface facing the double-row outer raceway surface;
a double row of rolling elements rotatably housed between raceway surfaces of the outer member and the inner member;
A wheel bearing device comprising: a sealing device that closes an open end of a bearing internal space formed by the outer member and the inner member,
comprising a ventilation mechanism that maintains the internal space of the bearing at atmospheric pressure;
The ventilation mechanism includes a ventilation hole that opens toward the bearing internal space and takes in and exhausts air in the bearing internal space, and a ventilation pipe connected to the ventilation hole,
The sealing device includes a first seal lip that prevents foreign matter from entering the bearing external space, and a second seal lip that seals grease in the bearing internal space,
The wheel bearing device, wherein the second seal lip has lower rigidity than the first seal lip. The first seal lip extends from upstream to downstream with respect to an air outflow direction when air leaks from the bearing internal space to the bearing external space,
The second seal lip extends from downstream to upstream and is in contact with the bearing internal space with respect to the outflow direction of air when air leaks from the bearing internal space to the bearing external space. The wheel bearing device according to claim 1. comprising a rotation sensor that detects the rotational speed of a rotating member of the outer member and the inner member,
The wheel bearing device according to claim 1 or 2, wherein the ventilation mechanism is provided in the rotation sensor. The ventilation mechanism includes a filter that takes in and exhausts air in the external space of the bearing and prevents foreign matter from entering.
The wheel bearing according to claim 3, wherein the ventilation pipe is guided into the vehicle together with the rotation sensor wiring, is separated from the rotation sensor wiring inside the vehicle, and is connected to the filter. Device.

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