JP2020193677A - Bearing device for wheel - Google Patents

Abstract

To provide a bearing device for a wheel which does not become unable to travel immediately even if a shaft body part is broken.SOLUTION: A bearing device 10 for a wheel includes: an outer ring member 12; an inner shaft member 14 having a shaft body part 36 and a flange part 38 to which a wheel 7 is fixed by a bolt 8; and rolling elements 16 provided between the outer ring member 12 and the inner shaft member 14. The shaft body part 36 is provided with a recessed part 46 recessed from one axial side to the other axial side. The recessed part 46 is formed with a slit 48 which guides occurrence of a crack along a surface including a center line C1 of the shaft body part 36 when an abnormal load acts on the shaft body part 36.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wheel bearing device.

In vehicles such as automobiles, a wheel bearing device (hub unit) is used to support the wheels. The wheel bearing device is located between an outer ring member (also referred to as an outer member) to which a wheel is attached, an inner shaft member (also referred to as an inner member) to which a wheel is attached, and an outer ring member and an inner shaft member. It is provided with a plurality of rolling elements (balls) provided.

In recent years, weight reduction has been required for wheel bearing devices. Patent Document 1 describes a wheel bearing device in which a recess is formed in the shaft body of the inner shaft member, and the thickness of the shaft body is set according to the shape of the recess to reduce the weight. It is disclosed.

Japanese Unexamined Patent Publication No. 2012-184848

When an excessive load (abnormal load) acts on the wheel bearing device, for example, when an automobile rides on a curb while traveling at high speed, the inner shaft member 91 fixing the wheel 99 is fixed as shown in FIG. A crack may occur in the shaft body portion 92 of the above. In particular, if the shaft body 92 is thinned for weight reduction, cracks are likely to occur.

Specifically, when an excessive load acts on the wheel bearing device, a crack occurs in the circumferential direction along the raceway surface 93 starting from the position 95 where the ball 94 contacts the raceway surface 93 of the shaft body portion 92. 100 can occur. In FIG. 5, the crack 100 that occurs is shown by a broken line. In this case, it is conceivable that the flange portion 96 fixing the wheel 99 is separated from the portion 97 on the vehicle inner side of the shaft main body portion 92. Then, the car becomes inoperable immediately.

Therefore, an object of the present disclosure is to provide a wheel bearing device that does not immediately become inoperable even if the shaft body portion is broken.

The wheel bearing device of the present disclosure includes an outer ring member, a shaft main body portion provided inward in the radial direction of the outer ring member, and a wheel extending radially outward from one axial side of the shaft main body portion. A wheel bearing device including an inner shaft member having a flange portion to which is fixed, and a rolling element provided between the outer ring member and the inner shaft member, and a shaft is attached to the shaft body portion. A recess is provided that is recessed from one side in the direction to the other side in the axial direction, and when an abnormal load is applied to the shaft body, cracks occur along the surface including the center line of the shaft body. A slit for guiding the wheel is formed in the recess.

According to the wheel bearing device, even if an abnormal load acts on the shaft body and a crack is generated in the shaft body, the crack is guided to the slit and forms the center line of the shaft body. It occurs along the containing surface. Even if the shaft body is broken in two at the crack, one of the broken shafts and the other are not separated because the wheels are fixed to the flange by bolts. That is, even if the shaft body is broken in two at the crack, the shape of the shaft is maintained. Therefore, the rolling element rolls so as to pass through the raceway surface where the crack is generated, but the rolling element is not immediately disabled.

Further, preferably, the slit is formed in a range including the bottom portion of the recess on the other side in the axial direction and including the center line of the shaft body portion.
Even if a bending load is generated on the shaft body in a normal running state, a large stress is unlikely to be generated in the region along the center line of the shaft body. Therefore, by forming the slit in the above range, the slit does not have a strong influence on the shaft main body portion in normal running.

Further, in the unlikely event, the slit preferably has the following sharp shape in order to guide and generate a crack along the surface including the center line of the shaft body portion. That is, it is preferable that the slit has a sharp shape in a direction that guides the generation of cracks along the surface including the center line of the shaft body portion. The "pointed shape" includes not only the "sharp and pointed shape" but also the "rounded and pointed shape".

Further, preferably, a plurality of bolt holes through which the bolt penetrates are formed in the flange portion along the circumferential direction, and the slit has a flat shape having a long axis and a short axis. A virtual extension line along the long axis intersects the region between the two adjacent bolt holes in the circumferential direction.
In this case, a crack occurs in the shaft body portion, and even if the crack reaches the flange portion, the crack does not easily reach the bolt hole. If the crack reaches the bolt hole, the fastening force of the wheel by the bolt may be weakened at the flange portion. However, according to the above configuration, the fastening force is not weakened, and even if the shaft main body is broken in two at the crack, one of the broken shaft main bodies and the other are not separated by the wheel.

According to the present invention, even if an excessive load acts on the wheel bearing device and the shaft body portion is broken, it is possible to prevent the wheel bearing device from being immediately unable to travel.

It is sectional drawing which shows an example of the rolling bearing apparatus. It is the figure which looked at the inner shaft member from one side in the axial direction. It is an enlarged view which looked at the slit on one side in the axial direction. It is explanatory drawing which shows the inner shaft member in a simplified manner, and is the figure which looked at the inner shaft member from the outside in the radial direction. It is sectional drawing which shows the conventional rolling bearing apparatus.

[Rolling bearing device]
FIG. 1 is a cross-sectional view showing an example of a wheel bearing device. The wheel bearing device 10 shown in FIG. 1 (hereinafter, also referred to as “bearing device 10”) is attached to a suspension device (also referred to as “knuckle”) provided on the vehicle body of a vehicle (automobile), and the wheel 7 is attached. Supports rotatably. The bearing device 10 is also referred to as a hub unit. With the bearing device 10 attached to the vehicle body side (suspension device), the left side of FIG. 1 is the wheel 7 side, which is referred to as the vehicle outer side. The right side of FIG. 1 is the center side of the vehicle body and is referred to as the vehicle inner side.

In the bearing device 10 of the present disclosure, the direction along the center line C of the bearing device 10 is defined as the "axial direction". This axial direction also includes a direction parallel to the center line C of the bearing device 10. The direction orthogonal to the bearing center line C is defined as the "diameter direction". In the bearing device 10 of the present disclosure, the vehicle outer side is one side in the axial direction, and the vehicle inner side is the other side in the axial direction.

The bearing device 10 includes a plurality of bearing devices 10 provided between the outer ring member (also referred to as an outer member) 12, the inner shaft member (also referred to as an inner member) 14, and the outer ring member 12 and the inner shaft member 14. It includes a rolling element 16. The rolling element 16 of the present disclosure is a ball.

The outer ring member 12 has a cylindrical outer ring main body portion 22 and a fixing flange portion 24 that extends outward in the radial direction from the outer ring main body portion 22. An outer raceway surface 26 is formed on one side and the other side of the inner circumference of the outer ring main body 22 in the axial direction. The flange portion 24 is attached to a knuckle (not shown) which is a vehicle body side member. As a result, the bearing device 10 including the outer ring member 12 is fixed to the vehicle body.

The inner shaft member 14 has a shaft-shaped hub shaft 32 (inner shaft) and an inner ring 34 fixed to the other side of the hub shaft 32 in the axial direction. The hub shaft 32 has a shaft main body portion 36 provided inward in the radial direction of the outer ring member 12 and a flange portion 38. The shaft body portion 36 is a portion long in the axial direction. The flange portion 38 is a portion of the shaft body portion 36 extending from one side in the axial direction toward the outside in the radial direction. A bolt hole 39 is formed in the flange portion 38. The wheel 7 is fixed to the flange portion 38 by the bolt 8 attached to the bolt hole 39. The inner ring 34 is an annular member, and is externally fitted and fixed to a part 40 on the other side in the axial direction of the shaft main body portion 36.

A shaft raceway surface 42 is formed on the outer peripheral side of the shaft main body 36, and an inner ring raceway surface 44 is formed on the outer peripheral surface of the inner ring 34. A plurality of rolling elements 16 are provided between the outer ring raceway surface 26 on one side in the axial direction and the shaft raceway surface 42. A plurality of rolling elements 16 are provided between the outer ring raceway surface 26 on the other side in the axial direction and the inner ring raceway surface 44. In each row, the plurality of rolling elements 16 are held by the cage 18. From the above, the inner shaft member 14 rotates about the center line C with respect to the outer ring member 12.

The outer ring member 12 and the shaft main body 36 are formed into a predetermined shape by forging. After that, predetermined portions (raceway surface, etc.) of the outer ring member 12 and the shaft main body 36 are machined.

The shaft body 36 is provided with a recess 46 that is recessed from one side in the axial direction toward the other side in the axial direction. As shown in FIGS. 1 and 2, a slit (notch) 48 is formed in the recess 46. FIG. 2 is a view of the inner shaft member 14 as viewed from one side in the axial direction. The slit 48 is formed in a range including at least a part of the bottom portion 47 on the other side in the axial direction of the recess 46, and is formed in a range including the center line C1 of the shaft body portion 36. The center line C1 of the shaft body 36 coincides with the center line C of the bearing device 10. In the present disclosure, the slit 48 is formed only in the bottom portion 47 facing one side in the axial direction, but may be formed beyond the bottom portion 47. The slit 48 is also provided when the shaft body portion 36 is formed by forging.

FIG. 3 is an enlarged view of the slit 48 viewed from one side in the axial direction. The shape of the slit 48 of the present disclosure as viewed from the axial direction is an elliptical shape, but may be an oval shape. The slit 48 has a flat shape having a long axis Y and a short axis X. Although not shown, a straight line may be included as a part of the contour line when the slit 48 is viewed from the axial direction.

The slit 48 has sharpened portions 49 on both sides of the shaft main body portion 36 in the radial direction. The shape of the pointed portion 49 may be a sharply pointed shape, but in the present disclosure, it is a rounded and pointed shape. The pointed direction of the slit 48 is the radial direction centered on the center line C1 of the shaft body portion 36. The slit 48 is provided with a stress concentration portion at the pointed portion 49. The pointed portion 49 is weaker in strength than the other portions. The pointed direction of the slit 48 is the direction in which the crack (fracture surface) 50 is guided and generated along the surface of the shaft body 36 including the center line C1. The crack 50 may occur when an abnormal load (excessive load) acts on the shaft body 36. In FIG. 2, the crack 50 that occurs is shown by a broken line.

The slit 48 has a sharp shape in the direction in which the crack 50 is guided and generated along the surface of the shaft body 36 including the center line C1. That is, the slit 48 is generated by guiding the crack 50 in the radial direction. The case where the abnormal load as described above acts on the shaft main body 36 is a case where the vehicle equipped with the bearing device 10 is traveling at a high speed and rides on a curb or the like.

As shown in FIG. 2, a plurality of bolt holes 39 (five in the illustrated example) through which the bolt 8 (see FIG. 1) is penetrated are formed in the flange portion 38 along the circumferential direction. The virtual extension line K in the direction along the long axis Y (see FIG. 3) of the slit 48 intersects the region 45 between two bolt holes 39 adjacent to each other in the circumferential direction.

As described above, in the bearing device 10 of the present disclosure, the shaft main body portion 36 of the inner shaft member 14 is provided with a recess 46 recessed from one side in the axial direction toward the other side in the axial direction. A slit 48 is formed in the recess 46. The slit 48 is configured to guide the generation of cracks along the surface of the shaft body 36 including the center line C1 when an abnormal load is applied to the shaft body 36.

According to this bearing device 10, even if an abnormal load acts on the shaft body 36 and a crack 50 is generated in the shaft body 36, the crack 50 is guided to the slit 48 and the shaft body 36 It occurs along the surface including the center line C1. FIG. 4 is an explanatory view showing the inner shaft member 14 in a simplified manner, and is a view of the inner shaft member 14 viewed from the outside in the radial direction. As shown in FIG. 4, even if the shaft main body 36 is broken in two at the crack 50 as a boundary, the wheel 7 is fixed to the flange 38 by the bolt 8, so that the broken shaft main body 36 One 51 and the other 52 are not separated.

Further, as described above, an annular inner ring 34 is fitted and attached to a part 40 of the shaft body 36 on the other side in the axial direction. Further, as shown in FIG. 1, a plurality of rolling elements 16 arranged along the outer raceway surface 26 of the outer ring member 12 and held by the cage 18 are provided around the broken shaft body portion 36. Therefore, even if the shaft body portion 36 breaks in two with the crack 50 as a boundary, the broken one 51 and the other 52 do not separate.

That is, even if the shaft main body 36 breaks in two with the crack 50 as a boundary, the shape as a shaft is maintained. Therefore, the rolling element 16 (see FIG. 1) rolls so as to pass through the raceway surface (axial raceway surface 42) in which the crack 50 is generated, but the rolling element 16 does not immediately become inoperable. From the above, the bearing device 10 of the present disclosure has a fail-safe function.

Here, even if a bending load is generated on the shaft main body 36 in a normal traveling state, a large stress is unlikely to be generated in the region along the center line C1 of the shaft main body 36. This is because the center line C1 is a substantially neutral axis. In the present disclosure, as described above (see FIGS. 1 and 2), the slit 48 is formed in a range including the bottom portion 47 on the other side in the axial direction of the recess 46 and including the center line C1 of the shaft body portion 36. Has been done. Therefore, although the slit 48 is formed in a part of the shaft main body 36, the slit 48 does not have a strong influence on the shaft main body 36 in normal running. That is, in a state where the vehicle is normally traveling, the shaft body portion 36 does not naturally crack. However, when an excessive force is applied to the bearing device 10, stress concentration occurs in the sharp portion 49 of the slit 48, and a crack 50 occurs in the radial direction starting from the sharp portion 49.

In the present disclosure (see FIG. 3), the slit 48 has a flat shape having a major axis Y and a minor axis X. As described above, the virtual extension line K in the direction along the long axis Y intersects the region 45 between the two bolt holes 39, 39 adjacent to each other in the circumferential direction at the flange portion 38. Therefore, even if a crack 50 is generated in the shaft body portion 36 and the crack 50 reaches the flange portion 38, the crack 50 is unlikely to reach the bolt hole 39 as shown in FIG. If the crack 50 reaches one bolt hole 39, the fastening force of the wheel 7 by the bolt 8 at the flange portion 38 may be weakened at one place. However, according to the above-described configuration of the present disclosure, even if the fastening force is not weakened and the shaft main body 36 breaks in two at the crack 50 as a boundary, the shaft main body 36 broken by the wheel 7 or the like (FIG. (See 4) One 51 and the other 52 are not separated.

The embodiments disclosed this time are exemplary in all respects and are not restrictive. The technical scope of the present invention is not limited to the above-described embodiment, and the technical scope includes all modifications within a range equivalent to the configuration described in the claims.

7: Wheel 8: Bolt 10: Bearing device for wheel 12: Outer ring member 14: Inner shaft member 16: Rolling element 36: Shaft body 38: Flange 39: Bolt hole 45: Area between bolt holes 46: Recess 47 : Bottom 48: Slit 49: Pointed 50: Crack C1: Center line K: Virtual extension line X: Short axis Y: Long axis

Claims (4)

Outer ring member and
An inner shaft member having a shaft body portion provided inward in the radial direction of the outer ring member, and a flange portion extending radially outward from one side of the shaft body portion in the axial direction and to which a wheel is fixed by a bolt.
A rolling element provided between the outer ring member and the inner shaft member,
It is a bearing device for wheels provided with
The shaft main body is provided with a recess recessed from one side in the axial direction toward the other side in the axial direction.
A wheel bearing device in which a slit for guiding the occurrence of a crack along a surface including the center line of the shaft body portion is formed in the recess when an abnormal load is applied to the shaft body portion. The wheel bearing device according to claim 1, wherein the slit is formed in a range including the bottom portion of the recess on the other side in the axial direction and including a center line of the shaft body portion. The slit has a sharp shape in a direction that guides the generation of cracks along the surface including the center line of the shaft body portion.
The wheel bearing device according to claim 1 or 2. A plurality of bolt holes for passing the bolts are formed in the flange portion along the circumferential direction.
The slit has a flat shape having a long axis and a short axis.
The wheel bearing device according to any one of claims 1 to 3, wherein the virtual extension line in the direction along the long axis intersects the region between the two bolt holes adjacent to each other in the circumferential direction.

Images