Wheel bearing device

Abstract

To provide a wheel bearing device that can improve the mechanical properties of the wheel bearing device, such as camber rigidity, by increasing the pitch circle diameter of the outer rolling elements without compromising the maintainability of the vehicle. [Solution] A wheel bearing device 1 comprises an inner member consisting of an outer ring 2, a hub ring 3, and an inner ring 4 fitted to the hub ring 3 on the inner side of the inner raceway surface 3c, an outer ball row 6, and an inner ball row 5, wherein the wheel mounting flange 3b has a tapped hole 3e into which a wheel bolt 3f is inserted from the outer side, the pitch circle diameter of the outer ball row 6 is larger than the pitch circle diameter of the inner ball row 5, and the thickness Ha of the wheel mounting flange 3b forming the tapped hole 3e is 1.02 times or more and less than 1.3 times the nominal diameter R of the wheel bolt 3f to be inserted.

Description

Technical Field

[0001] The present invention relates to a wheel bearing device.

Background Art

[0002] Conventionally, a wheel bearing device that rotatably supports a wheel in a suspension device of a vehicle such as an automobile is known.

[0003] In recent years, in vehicles in which wheel bearing devices are used, fuel regulations have been imposed due to social backgrounds such as energy conservation and decarbonization, and the trend toward electrification has been advancing. In the future, in electric vehicles that use an in-vehicle battery as the main power source and are expected to spread, the vehicle weight is larger and the axle load tends to increase compared to gasoline vehicles.

[0004] Generally, when the axle load increases, the rotational torque of the wheel bearing device increases, and it is necessary to increase the size of the wheel bearing device from the viewpoints of durability and strength. For example, in a wheel bearing device used in an electric vehicle, the outer diameter at the axial end of the outer ring has a tendency to be narrowed and enlarged, which is larger than the axial distance between the flange surface of the wheel mounting flange provided on the hub ring and the axial end surface of the inner ring fitted to the hub ring, and the weight is increased compared to the wheel bearing device used in a gasoline vehicle. Therefore, in a wheel bearing device used in an electric vehicle, reduction of torque and weight are required.

[0005] For example, as shown in Patent Document 1, fixing by hub bolts in which hub bolts are press-fitted into a wheel mounting flange provided on a hub ring and the wheel is fastened with nuts on the wheel side is known. Further, in a wheel bearing device, when the pitch circle diameter (P.C.D.) of the outer rolling elements is formed larger than the pitch circle diameter (P.C.D.) of the inner rolling elements, the camber rigidity increases, and the handling stability of the vehicle is improved.

[0006] This configuration improves mechanical properties such as camber rigidity while also improving the durability of the wheel bearing device. However, in the fixing method using hub bolts as shown in Patent Document 1, the hub bolts are press-fitted into the wheel mounting flange. Therefore, when performing vehicle maintenance, it is necessary to set aside space so that the hub bolts can be removed toward the vehicle body, and it was not possible to sufficiently enlarge the pitch circle diameter (PCD) of the outer rolling element, which is on one axial side. If the pitch circle diameter (PCD) of the outer rolling element is made too large, the outer diameter of the outer ring will overlap radially when removing the hub bolts, which may prevent the hub bolts from being removed. In addition, if the bolt threads of the hub bolts are stripped, it becomes impossible to remove the wheel from the vehicle body. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-155837 [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, the present invention has been made in view of the above circumstances, and provides a wheel bearing device that can improve the mechanical properties of the wheel bearing device, such as camber rigidity, by increasing the pitch circle diameter (PCD) of the outer rolling elements without impairing the maintainability of the vehicle. [Means for solving the problem]

[0009] That is, the wheel bearing device comprises an outer member having a first outer raceway surface formed on one axial side and a second outer raceway surface formed on the other axial side of the first outer raceway surface; an inner member having a wheel mounting flange for mounting a wheel on one axial side of the outer member and a first inner raceway surface facing the first outer raceway surface; an inner ring fitted to the hub ring on the other axial side of the first inner raceway surface and a second inner raceway surface facing the second outer raceway surface; a first rolling element rotatably housed between the first outer raceway surface and the first inner raceway surface; and a second rolling element rotatably housed between the second outer raceway surface and the second inner raceway surface, wherein the wheel mounting flange has a tapped hole into which a bolt is inserted from one axial side; the pitch circle diameter of the first rolling element is larger than the pitch circle diameter of the second rolling element; and the thickness of the wheel mounting flange forming the tapped hole is 1.02 times or more and less than 1.3 times the nominal diameter of the bolt to be inserted. [Effects of the Invention]

[0010] According to the present invention, the pitch circle diameter (PCD) of the outer rolling elements can be increased without impairing the maintainability of the vehicle, thereby improving the mechanical properties of the wheel bearing device, such as the camber rigidity. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side cross-sectional view showing a wheel bearing device according to this embodiment. [Figure 2] This is a view from the inner side showing the wheel bearing device according to this embodiment. [Figure 3] This is an enlarged view of the main part of the wheel bearing device according to this embodiment. [Figure 4] This is a magnified view of the main components of a conventional wheel bearing device. [Figure 5] This is a magnified view of the main components of a conventional wheel bearing device. [Figure 6] This is a magnified view of the main components of a conventional wheel bearing device. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention will be described below with reference to the attached drawings.

[0013] [Wheel bearing device] The wheel bearing device 1 shown in Figure 1 is one embodiment of the wheel bearing device according to the present invention, and is used to rotatably support a wheel in the suspension system of a vehicle such as an automobile.

[0014] In the following explanation, "axial direction" refers to the direction along the rotation axis X of the wheel bearing device 1. "Radial direction" refers to the direction perpendicular to the rotation axis X. Furthermore, "outer side" refers to one axial end of the wheel bearing device 1, which is the wheel side when mounted on the vehicle body, and "inner side" refers to the other axial end of the wheel bearing device 1, which is the vehicle body side when mounted on the vehicle body.

[0015] The wheel bearing device 1 has a configuration referred to as the third generation, and comprises an outer ring 2 which is an outer member, a hub ring 3 and an inner ring 4 which are inner members, two rows of inner ball rows 5 and outer ball rows 6 which are rolling rows, and an inner sealing member 9 and an outer sealing member 10.

[0016] An inner side opening 2a is formed at the inner side end of the outer ring 2, into which the inner side sealing member 9 can be fitted. An outer side opening 2b is formed at the outer side end of the outer ring 2, into which the outer side sealing member 10 can be fitted.

[0017] The inner circumferential surface of the outer ring 2 has an inner outer raceway surface 2c and an outer outer raceway surface 2d. The outer outer raceway surface 2d is an example of a first outer raceway surface, and the inner outer raceway surface 2c is an example of a second outer raceway surface. A vehicle body mounting flange 2e (see Figure 2) for attaching the outer ring 2 to the vehicle body side member is integrally formed on the outer circumferential surface of the outer ring 2.

[0018] On the inner side end of the outer peripheral surface 3j of the hub ring 3, a small-diameter stepped portion 3a having a smaller diameter than the outer side end is formed. On the outer side end of the hub ring 3, a wheel mounting flange 3b for mounting the wheel is integrally formed.

[0019] The wheel mounting flange 3b is formed with a plurality of tapped holes 3e into which the wheel bolts 3f are inserted. On the inner peripheral surface of the tapped hole 3e, an internal thread that is screwed with the wheel bolt 3f for fastening the hub ring 3, the wheel WH, and the brake rotor BR is formed. The wheel mounting flange 3b has a flange surface 3k facing the outer side. The hub ring 3 has a through hole 3i penetrating in the axial direction, and a constant velocity joint can be fitted into the through hole 3i so as to be rotatable integrally with the hub ring 3.

[0020] On the outer peripheral surface 3j of the hub ring 3, an inner side raceway surface 3c on the outer side is provided so as to face the outer side raceway surface 2d on the outer side of the outer ring 2. That is, on the outer side of the inner member, the inner side raceway surface 3c is formed by the hub ring 3. The inner side raceway surface 3c of the hub ring 3 is an example of the first inner side raceway surface. In the hub ring 3, a lip sliding surface 3d with which the outer side seal member 10 slides is formed on the base side of the wheel mounting flange 3b.

[0021] The inner side seal member 9 is fitted to the inner side opening end of the annular space S formed by the outer ring 2 and the hub ring 3, and closes the inner side opening end. The outer side seal member 10 is fitted to the outer side opening end of the annular space S formed by the outer ring 2 and the hub ring 3, and closes the outer side opening end.

[0022] The inner ring 4 is provided on the small-diameter stepped portion 3a of the hub ring 3. The inner ring 4 is fixed to the small-diameter stepped portion 3a of the hub ring 3 by press-fitting. The inner ring 4 applies preload to the inner side ball row 5 and the outer side ball row 6 which are rolling rows. The inner ring 4 fitted to the small-diameter stepped portion 3a of the hub ring 3 has a fitting surface 4c with respect to the hub ring 3. The fitting surface 4c is the inner peripheral surface of the inner ring 4.

[0023] The outer circumferential surface of the inner ring 4 is provided with an inner raceway surface 4a that faces the outer raceway surface 2c on the inner side of the outer ring 2. In other words, the inner raceway surface 4a is formed on the inner side of the inner member by the inner ring 4. The inner raceway surface 4a of the inner ring 4 is an example of a second inner raceway surface.

[0024] The inner ball row 5 and the outer ball row 6, which are rolling elements, are composed of multiple balls 7, which are rolling elements, held by a cage 8. The inner ball row 5 is rotatably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner outer raceway surface 2c of the outer ring 2. The outer ball row 6 is rotatably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer outer raceway surface 2d of the outer ring 2.

[0025] In other words, the inner ball row 5 and the outer ball row 6 are rotatably housed between the raceway surfaces of the outer and inner members. The balls 7 of the outer ball row 6 are an example of first rolling elements, and the balls 7 of the inner ball row 5 are an example of second rolling elements.

[0026] In the wheel bearing device 1, a double-row angular contact ball bearing is constructed from an outer ring 2, a hub ring 3 and an inner ring 4, an inner ball row 5, and an outer ball row 6. Alternatively, the wheel bearing device 1 may be configured with a double-row tapered roller bearing instead of the double-row angular contact ball bearing.

[0027] [Relationship of dimensions of various parts in a wheel bearing system] As shown in Figure 1, the pitch circle diameter of the balls 7 constituting the inner ball row 5 is PCDi, and the pitch circle diameter of the balls 7 constituting the outer ball row 6 is PCDo. The pitch circle diameter PCDi of the inner ball row 5 is the diameter of the circle that is centered on the rotation axis X and passes through the center Ci of the balls 7 in the inner ball row 5. The pitch circle diameter PCDo of the outer ball row 6 is the diameter of the circle that is centered on the rotation axis X and passes through the center Co of the balls 7 in the outer ball row 6.

[0028] The pitch circle diameter PCDo of the outer ball row 6 and the pitch circle diameter PCDi of the inner ball row 5 satisfy the relationship PCDo > PCDi. In other words, the pitch circle diameter PCDo of the outer ball row 6 is larger than the pitch circle diameter PCDi of the inner ball row 5.

[0029] Thus, in the wheel bearing device 1, the pitch circle diameter PCDo of the outer ball row 6 is made larger than the pitch circle diameter PCDi of the inner ball row 5, thereby improving the vehicle's handling stability by increasing camber rigidity while achieving environmental performance such as reduced torque and weight. Camber rigidity is a coefficient that refers to the lateral rigidity of the wheel with respect to the camber angle when the wheel tilt (camber angle) is small. Specifically, it is the proportionality constant when the lateral force (camber thrust) generated when the wheel is tilted is proportional to the camber angle.

[0030] Increasing camber rigidity allows for the generation of strong camber thrust, improving the vehicle's driving stability and cornering performance. Specifically, generating strong camber thrust prevents the vehicle from being disrupted by external disturbances such as uneven road surfaces or crosswinds, thus improving driving stability. Furthermore, generating strong camber thrust improves responsiveness when the wheels are tilted by the steering wheel, thus improving cornering performance.

[0031] As shown in Figure 3, the thickness of the wheel mounting flange 3b that forms the tapped hole 3e is Ha. The thickness Ha of the wheel mounting flange 3b that forms the tapped hole 3e is the length from the inner opening end to the outer opening end of the tapped hole 3e. Preferably, the thickness Ha of the wheel mounting flange 3b that forms the tapped hole 3e is 1.02 times or more and less than 1.3 times the nominal diameter R of the wheel bolt 3f to be inserted. The nominal diameter R of the wheel bolt 3f is the dimension representing the outer diameter of the threaded portion of the wheel bolt 3f.

[0032] In this way, by making the thickness Ha of the wheel mounting flange 3b in which the tapped hole 3e is formed 1.02 times or more the nominal diameter R of the wheel bolt 3f, the axial force of the wheel bolt 3f can be fully exerted, and the wheel WH and brake rotor BR can be fixed. Alternatively, by making the thickness Ha of the wheel mounting flange 3b in which the tapped hole 3e is formed less than 1.3 times the nominal diameter R of the wheel bolt 3f, the tapped hole 3e can be formed without increasing the thickness of the wheel mounting flange 3b itself, thereby preventing an increase in the axial dimension of the wheel bearing device 1.

[0033] Next, we will explain the relationship between the vehicle body mounting flange 2e of the outer ring 2 and the outer side portion 2h located on the outer side of the vehicle body mounting flange 2e. As shown in Figure 3, the outer side portion 2h is a cylindrical portion located on the outer side of the vehicle body mounting flange 2e and houses the outer side ball row 6 inside.

[0034] The outer side portion 2h is continuous with the vehicle body mounting flange 2e, and the outer diameter r of the outer side portion 2h decreases towards the outer side. The outer diameter ra of the outer side portion 2h at the intersection point 2ha of the radially extending straight line passing through the groove bottom 2da of the outer raceway surface 2d and the outer peripheral surface of the outer side portion 2h is formed to be smaller than the outer diameter of the inner end of the vehicle body mounting flange 2e.

[0035] By configuring it in this way, the outer diameter of the outer ring 2 increases in the radial direction, which prevents the radial size of the wheel bearing device 1 from increasing.

[0036] Furthermore, d1 is defined as the radial length between the groove bottom of the outer ring raceway surface and the outer circumferential surface of the outer side portion 2h of the outer ring 2. The radial length d1 is preferably 3.6 mm or more and less than 6 mm.

[0037] When the radial length d1 was less than 3.6 mm, the heat-treated hardened layer applied from the surface of the outer raceway 2d toward the outer diameter could reach the outer circumferential surface of the outer ring 2, causing quenching cracks. Also, when the radial length d1 was 6 mm or more, the thickness of the outer ring 2 itself increased, leading to an increase in the weight and size of the wheel bearing device 1. Therefore, d1 is defined as the radial length between the outer ball 7, the groove bottom 2da of the outer raceway 2d, and the outer circumferential surface of the outer side portion 2h of the outer ring 2. By setting the radial length d1 to 3.6 mm or more and less than 6 mm, the wheel bearing device 1 can be miniaturized while ensuring a predetermined thickness of the untreated layer, which has not undergone heat treatment hardening, from the outer diameter of the outer ring 2, thereby preventing quenching cracks.

[0038] [Method for mounting wheels to wheel bearing devices] When attaching the brake rotor BR and wheel WH to the wheel mounting flange 3b of the wheel bearing device 1, the holes provided in the brake rotor BR and wheel WH are aligned radially with the tapped holes 3e, and the wheel bolts 3f are inserted from the outer side to the inner side. By screwing the male threaded portion of the wheel bolt 3f with the female threaded portion of the tapped holes 3e, a fastening force is generated, fixing the brake rotor BR and wheel WH to the wheel mounting flange 3b.

[0039] Furthermore, if the threads of the wheel bolt 3f become stripped and the fastening force decreases, the wheel bolt 3f can be easily removed by pulling it outwards from the wheel WH. This makes it easier to replace the wheel bolt 3f. Also, since the wheel bolt 3f can be removed from the outer side with a tool, it becomes easier to remove the wheel WH and perform internal maintenance. Therefore, maintainability is improved.

[0040] For example, in the conventional method of fixing a hub bolt 3g by press-fitting it into a bolt hole provided in the wheel mounting flange 3b, as shown in Figure 4, the head of the hub bolt 3g is located on the inner side of the wheel mounting flange 3. As shown in Figure 5, if the pitch circle diameter PCDo of the outer ball row 6 is increased, the head of the hub bolt 3g comes into contact with the outer circumferential surface of the outer opening 2b of the outer ring 2 and interferes. For this reason, there were limitations on increasing the pitch circle diameter PCDo of the outer ball row 6.

[0041] Furthermore, as shown in Figure 6, when the pitch circle diameter PCDi of the balls 7 constituting the inner ball row 5 and the pitch circle diameter PCDo of the balls 7 constituting the outer ball row 6 are set to the same diameter, the head of the hub bolt 3g does not come into contact with the outer surface of the outer opening 2b of the outer ring 2, but it was difficult to improve the camber rigidity.

[0042] Therefore, as shown in Figures 1 and 3, by providing a tapped hole 3e in the wheel mounting flange 3b and inserting the wheel bolt 3f from the outer side towards the inner side, the head of the wheel bolt 3f is positioned on the outer side of the wheel mounting flange 3b. With this configuration, the head of the wheel bolt 3f does not come into contact with the outer circumferential surface of the outer opening 2b of the outer ring 2, and the pitch circle diameter PCDo of the outer ball row 6 can be made larger than the pitch circle diameter PCDi of the inner ball row 5.

[0043] As described above, the wheel bearing device 1 of the present invention comprises an outer ring 2 having an outer raceway surface 2d on the outer side and an outer raceway surface 2c formed on the inner side of the outer raceway surface 2d, a hub ring 3 having a wheel mounting flange 3b for attaching a wheel WH on the outer side of the outer ring 2 and an inner raceway surface 3c facing the outer raceway surface 2d, and an inner ring 4 fitted to the hub ring 3 on the inner side of the inner raceway surface 3c and having an inner raceway surface 4a facing the outer raceway surface 2c, and between the outer raceway surface 2d and the inner raceway surface 3c A wheel bearing device 1 comprises an outer ball row 6 that is rotatably housed therein, and an inner ball row 5 that is rotatably housed between an outer raceway surface 2c and an inner raceway surface 4a, wherein the wheel mounting flange 3b has a tapped hole 3e into which a wheel bolt 3f is inserted from the outer side, the pitch circle diameter of the outer ball row 6 is larger than the pitch circle diameter of the inner ball row 5, and the thickness Ha of the wheel mounting flange 3b forming the tapped hole 3e is 1.02 times or more and less than 1.3 times the nominal diameter R of the wheel bolt 3f to be inserted. By configuring it in this way, the pitch circle diameter PCDo of the outer ball row 6 is made larger than the pitch circle diameter PCDi of the inner ball row 5, thereby improving the vehicle's handling stability by increasing camber rigidity while achieving environmental performance such as reduced torque and weight.

[0044] Furthermore, the tapped holes 3e can be formed without increasing the thickness of the wheel mounting flange 3b itself, thus preventing an increase in the axial dimension of the wheel bearing device 1.

[0045] Furthermore, the outer ring 2 has a vehicle body mounting flange 2e for attaching the outer ring 2 to the vehicle body side member, and an outer side portion 2h located on the outer side of the vehicle body mounting flange 2e. The outer diameter ra of the outer side portion 2h at the intersection point 2ha of the radially extending straight line passing through the groove bottom 2da of the outer raceway surface 2d and the outer circumferential surface of the outer side portion 2h is smaller than the outer diameter of the inner end of the vehicle body mounting flange 2e. By configuring it in this way, the outer diameter of the outer ring 2 increases in the radial direction, which prevents the radial size of the wheel bearing device 1 from increasing.

[0046] Furthermore, it is preferable that the radial length d1 between the groove bottom 2da of the outer raceway surface 2d and the outer peripheral surface of the outer side portion 2h of the outer ring 2 is 3.6 mm or more and less than 6 mm. By configuring it in this way, the wheel bearing device 1 can be miniaturized, and a predetermined thickness of the untreated layer, which has not undergone heat treatment hardening, can be secured from the outer diameter of the outer ring 2, thereby preventing cracking during heating.

[0047] Although embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, but is merely illustrative. It can be implemented in various other forms without departing from the spirit of the invention, and the scope of the present invention is indicated by the claims, and further includes all modifications within the meaning and scope of equivalents as described in the claims. [Explanation of Symbols]

[0048] 1. Wheel bearing device 2 Outer ring 2c (Inner side) outer raceway surface 2d (Outer side) outer raceway surface 3 Hub wheels 3a Small diameter stepped section 3b Wheel mounting flange 3c Inner raceway surface 3e tapped hole 3f Wheel bolts 4. Inner Ring 4a Inner raceway surface 4b Inner side end face 5. Inner ball row 6 Outer ball row 7 Ball PCDi (Pitch circle diameter of balls in the inner ball row) PCDo (Pitch circle diameter of balls in the outer ball row)

Claims

1. An outer member having a first outer raceway surface formed on one axial side and a second outer raceway surface formed on the other axial side of the first outer raceway surface, The inner member comprises a wheel mounting flange located on one axial side of the outer member, a hub ring having an axially extending outer surface, and at least one inner ring press-fitted onto the outer surface of the hub ring, and having double rows of inner ring raceway surfaces facing the first outer raceway surface and the second outer raceway surface of the outer member, A first rolling element is housed so as to be rotatable between the first outer raceway surface and the first inner raceway surface, A wheel bearing device comprising a second rolling element rotatably housed between the second outer raceway surface and the second inner raceway surface, The wheel mounting flange has a tapped hole into which a bolt is inserted from one axial side. The pitch circle diameter of the first rolling element is larger than the pitch circle diameter of the second rolling element. A wheel bearing device in which the thickness of the wheel mounting flange forming the tapped hole is 1.02 times or more and less than 1.3 times the nominal diameter of the bolt to be inserted.

2. The outer member has a vehicle body mounting flange for attaching the outer member to the vehicle body side member, and an axial side portion located on one axial side of the vehicle body mounting flange. The outer diameter of the axial side at the intersection of a straight line extending radially through the bottom of the groove of the first raceway surface and the outer circumferential surface of the axial side is smaller than the outer diameter of the vehicle body mounting flange. The wheel bearing device according to claim 1.

3. The radial length between the groove bottom of the first outer raceway surface of the outer member and the outer circumferential surface of one axial side of the outer member is 3.6 mm or more and less than 6 mm. The wheel bearing device according to claim 1.

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