JP2008006859A - Bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing unit capable of suppressing the slackness of a CVJ nut by hardening a CVJ nut seat surface on which the CVJ nut abuts, and capable of effectively preventing the generation of noise. <P>SOLUTION: The bearing unit comprises a stationary wheel 2 fixed to a vehicle body structure member; a rotating wheel 4 fixed to a wheel structure member and a wheel driving shaft structure member, and rotating together with them; and a plurality of rolling elements 18a, 18b rotatably mounted between raceway surfaces 2s, 4s and 2t, 4t opposite to each other formed on the stationary wheel and the rotating wheel. In a state of being fitted with the wheel driving shaft structure member, the rotating wheel is fixed to the wheel driving shaft structure member by a fastening member from one side in the extending direction of a driving shaft. In the rotating wheel, at at least a part 12c on which the fastening member abuts, a predetermined hardened layer S set to have hardness larger than that of a part in the vicinity of the layer is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bearing unit that supports, for example, a vehicle wheel, and more particularly to an improvement in a bearing unit structure for preventing the generation of abnormal noise from the bearing unit.

This type of bearing unit includes, for example, as shown in FIGS. 2A and 2B, a stationary wheel 2 fixed to a vehicle body (a knuckle (not shown) of a suspension device) and a wheel (disc wheel 42). And a rotating wheel 4 that rotates together with the disc wheel 42. That is, in this case, the bearing unit is configured such that the outer ring side is the stationary ring 2 and the inner ring side is the rotating ring 4.
Also, in such a bearing unit, a plurality of rolling elements (balls) 18 are incorporated so as to be able to roll between the mutually opposing double-row (two rows) raceway surfaces formed on the stationary wheel 2 and the rotating wheel 4 respectively. It is. In this case, the rolling elements (balls) 18 roll between the raceway surfaces in a state where the rolling elements (balls) 18 are rotatably held one by one in a pocket formed in the annular cage 20.

  In the configuration shown in FIG. 2 (a), a stationary flange 2 is integrally formed with a fixing flange 2f that protrudes outward (in the direction of increasing the diameter) from its outer peripheral surface 2a. The stationary wheel 2 can be fixed to a knuckle of a suspension device (suspension) (not shown) by inserting a fixing bolt 58 into the fixing hole 2h that passes therethrough and fastening it to the vehicle body side.

  The rotating wheel 4 is provided with a hub 12 having a substantially cylindrical shape. The hub 12 is fixed to a disc wheel 42 of a wheel via a braking member (brake disc 40), and together with the disc wheel 42 It is configured to rotate. The hub 12 is provided with a hub flange 12f for fixing (externally fitting) the disk portion 42d of the disk wheel 42 to one side (left side of the figure) in the axial direction (left-right direction in FIG. 2A). Projecting continuously along the circumferential direction.

  In this case, the hub flange 12f extends outward (in the radial direction of the hub 12) beyond the stationary ring 2, and a plurality of through-holes (in the circumferential direction) are provided in the vicinity of the extended edge. Bolt holes) 12h are provided. Also, a plurality of through holes 40h, 42h that can communicate with the bolt holes 12h are provided along the circumferential direction in the disk portion 42d of the brake disk 40 and the disk wheel 42 (for example, the same number as the bolt holes 12h). It has been. Then, by inserting a plurality of hub bolts 14 from the bolt holes 12h into the through holes 40h and 42h and fastening with the hub nuts 76, the brake disc 40 and the disc wheel 42 can be positioned and fixed with respect to the hub flange 12f. .

Further, in the configuration shown in FIG. 2 (a), the bearing unit includes driving wheels (FR (front engine rear wheel drive)) and RR (rear engine rear wheel drive) rear wheels, FF (front Engine front wheel drive) is configured as a bearing unit that supports the front wheels of a vehicle and all wheels of a four-wheel drive vehicle. The hub 12 has one axial end to the other end (in FIG. 2A). A spline hole 12t having a predetermined size penetrating from the left end side to the right end side is formed, and the spline shaft 92s of the constant velocity joint 92 is inserted into the spline hole 12t. The hub 12 can be rotated together with the spline shaft 92s by being externally fitted to the spline shaft 92s.
The hub 12 has an annular inner ring structure 16 (a member constituting the rotating wheel 4 together with the hub 12) on the other side (right side in FIG. 2) in the axial direction (left and right direction in FIG. 2A). It is designed to be fitted.

  In this case, for example, after the inner ring component 16 is externally fitted to the step 12 s formed on the hub 12 with the plurality of rolling elements 18 held between the stationary wheel 2 and the rotating wheel 4 by the cage 20. The spline shaft 92s of the constant velocity joint 92 is inserted into the spline hole 12t of the hub 12 from the inside of the vehicle body to the outside (from the right side to the left side in FIG. 2A). At the tip end portion (left end portion in FIG. 2A) of the spline shaft 92s, the spline shaft 92s is provided at a portion protruding from the CVJ nut seat surface 12c of the hub 12 toward the vehicle body outward direction (left direction in FIG. 2A). The hub 12 and the spline shaft 92s can be positioned and fixed by screwing the CVJ nut 94 into the male threaded portion 92t and fastening the CVJ nut 94 so as to contact the CVJ nut seat surface 12c of the hub 12. . At this time, the inner ring constituting body 16 has one end face (end face on the inner side of the vehicle body (right side in FIG. 2A)) 16a is one end face of the constant velocity joint 92 (end face on the outer side of the vehicle body (left side in FIG. 2A)). ) 92a abuts, and is fixed by being sandwiched between the end surface 92a of the constant velocity joint 92 and the step portion 12s of the hub 12. Further, when the inner ring component 16 is positioned and fixed, a predetermined preload is applied to the bearing unit.

  In the configuration shown in FIG. 2A, the inner ring component 16 is sandwiched between the end surface 92a of the constant velocity joint 92 and the step portion 12s of the hub 12, and the one side of the hub 12 (the vehicle body The CVJ nut 94 is fastened from the outside (left side of FIG. 2A), and is positioned and fixed. For example, as shown in FIG. May be.

  In this case, after the inner ring constituting body 16 is externally fitted to the step portion 12s of the hub 12, the end portion 12d on one side of the hub 12 (the inner side of the vehicle body (the right side in FIG. 2 (b))) is crimped. The structural body 16 can be fixed to the hub 12 and a predetermined preload can be applied to the bearing unit. FIG. 2B is a conceptual diagram showing only the basic configuration of the bearing unit. For example, the description of members such as constant velocity joints, spline shafts, and CVJ nuts is omitted. Yes. However, even in this case, as in the case of the configuration shown in FIG. 2A, the hub 12 is connected to the hub 12 by the CVJ nut 94 from one side of the hub 12 (outside the vehicle body (left side of FIG. 2A)). The spline shaft 92s of the constant velocity joint 92 is positioned and fixed. In this state, the end portion 12d of the hub 12 after crimping is in contact with one end surface of the constant velocity joint 92 (corresponding to the end surface 92a in FIG. 2A) (not shown).

  Further, in such a bearing unit, a rolling element (ball) 18 is sandwiched between the stationary wheel 2 and the rotating wheel 4 so that the bearing unit is sealed on both sides (the left side and the right side in FIG. 2A). The sealing plate 98 is provided. By providing the sealing plate 98 in this way, foreign matter (for example, muddy water, dust) is prevented from entering the inside from the outside of the bearing unit, and a lubricant (for example, grease, oil, etc.) enclosed in the inside is prevented. ) Is prevented from leaking outside.

  By the way, the hub 12 constituting such a bearing unit has a raceway surface (outboard) for rolling the hub flange 12 f and the pilot portion 12 p for positioning and fixing the brake disc 40 and the disc wheel 42 and the rolling element 18. Side raceway surface) 4s is integrally formed. In this way, the hub 12 in which the hub flange 12f, the pilot portion 12p, and the raceway surface 4s are integrally formed ensures the rolling fatigue life of the raceway surface 4s and the bending strength of the hub flange 12f, and impacts the hub flange 12f. It is necessary to have a rigidity capable of preventing rapid breakage when added.

  For this reason, structural steel for machinery is applied to the hub 12 of the bearing unit, and the structural steel for machinery is hot forged to form the raceway surface 4s, and then the high frequency is applied to the raceway surface 4s. The hub 12 is configured by performing processing (quenching processing). On the other hand, the CVJ nut seat surface 12c of the hub 12 is not quenched, and the hub 12 is configured with the CVJ nut seat surface 12c as a non-quenched portion.

  For such a bearing unit, while the vehicle is running, a reaction force against the force applied to the road surface when the vehicle accelerates or decelerates acts from the road surface, and a variable moment load associated with the reaction force is applied to the wheel (illustrated). 2) and the disc wheel 42 continuously, and the distortion (bending) may occur in the hub 12 of the bearing unit. When the distortion occurs in the hub 12 as described above, the CVJ nut 94 for positioning and fixing the hub 12 and the spline shaft 92s may be loosened depending on the degree of the distortion. In this case, for example, in the configuration shown in FIG. 2A, the end surface 16a of the inner ring component 16 and the end surface 92a of the constant velocity joint 92 are irregularly contacted, and in the configuration shown in FIG. The end portion 12d after the caulking of the hub 12 and the end surface 92a of the constant velocity joint 92 may contact each other irregularly, and abnormal noise such as stagnation may occur.

Here, there are three main causes for the looseness of the CVJ nut 94 under the situation where the variable moment load continues to act on the bearing unit. In the following description, for the sake of convenience, a bearing unit having the configuration shown in FIG. 2A is assumed as an example.
First, as a first cause, a portion where the CVJ nut 94 and the CVJ nut seat surface 12c of the hub 12 come into contact with each other (wear) is worn by friction, and the hub 12 (inner ring component 16) and the spline It can be mentioned that the axial force of the spline shaft 92s is reduced when the portions 16a and 92a that are in contact with (abut each other) with the shaft 92s wear due to friction.

  Next, as a second cause, the CVJ nut seat surface 12c of the hub 12 that contacts (abuts) the CVJ nut 94 is depressed due to high surface pressure, and the hub 12 (inner ring component 16) and the spline shaft 92s. One side of the portions 16a and 92a that are in contact with each other (striking) is depressed by a high surface pressure, so that the axial force of the spline shaft 92s is reduced.

  The third cause is that the CVJ nut 94 is displaced in the radial direction (vertical direction in FIG. 2A) because the hub 12 of the bearing unit is continuously and variably distorted (bent). In other words, a loosening torque of the CVJ nut 94 is generated.

Based on the above causes, the following measures are conventionally known as measures for preventing the occurrence of loosening of the CVJ nut 94 as described above.
For example, a lubricant is applied to a portion where the CVJ nut 94 and the CVJ nut seat surface 12c of the hub 12 come into contact with each other (contact) as a countermeasure against the looseness caused by the first cause described above. For example, there is a means for preventing wear of the contact portion. On the other hand, with respect to the portions 16a and 92a where the hub 12 (inner ring component 16) and the spline shaft 92s come into contact with each other (abut), for example, Patent Document 1 discloses an end face 16a of the hub 12 (inner ring component 16). A means for forming a continuous groove along the circumferential direction is disclosed.

  Next, as a countermeasure against the looseness caused by the second cause described above, for example, the contact area of the CVJ nut seat surface 12c of the hub 12 that contacts (contacts) the CVJ nut 94 is increased. There are means for reducing the surface pressure and means for increasing the surface strength. On the other hand, the portions 16a and 92a where the hub 12 (inner ring component 16) and the spline shaft 92s contact (abut each other) are usually large in diameter, and the CVJ nut of the hub 12 is large. Compared with the seating surface 12c side, the surface pressure is not large. Moreover, since the hub 12 (inner ring structure 16) has been quenched, there is little risk of being depressed.

  As a countermeasure against the looseness caused by the third cause described above, for example, the surface frictional force (friction resistance) of the CVJ nut seat surface 12c of the hub 12 that contacts (abuts) the CVJ nut 94 is determined as the CVJ nut. There is a means for preventing the CVJ nut 94 from being displaced in the radial direction (vertical direction in FIG. 2A) by setting it to be larger than the loosening torque of 94.

In consideration of these, in order to prevent the looseness of the CVJ nut 94, the shape of the CVJ nut 94 is processed to increase the surface pressure at the CVJ nut seat surface 12c that contacts the CVJ nut 94, and the CVJ nut seat surface. It is effective to prevent the wear of the contact portion with 12c. On the other hand, for the hub 12, it is effective to increase the surface strength of the CVJ nut seat surface 12c with which the CVJ nut 94 abuts and to increase the surface frictional force (friction resistance).
JP 2003-136908 A

  However, for example, when a lubricant is applied to the portion where the CVJ nut 94 and the CVJ nut seating surface 12c of the hub 12 are in contact with each other, wear of the contact portion can be prevented. The surface frictional force (friction resistance) of the CVJ nut seat surface 12c becomes small. Thus, in the portion where the CVJ nut 94 and the CVJ nut seating surface 12c of the hub 12 are in contact with each other, preventing wear and increasing the surface frictional force (friction resistance) have a so-called trade-off relationship. Therefore, it is difficult to make these both compatible, and there is a demand for the realization of an effective countermeasure.

  The present invention has been made to solve such problems, and its purpose is to harden the CVJ nut seating surface of the hub with which the CVJ nut abuts, thereby suppressing loosening of the CVJ nut and generating abnormal noise. It is an object of the present invention to provide a bearing unit that can effectively prevent the above-described problem.

  In order to achieve such an object, a bearing unit according to the present invention includes a stationary wheel fixed to a vehicle body component member, a rotating wheel fixed to a wheel component member and a wheel drive shaft component member, and rotating together therewith, And a plurality of rolling elements that are formed on the stationary wheel and the rotating wheel, respectively, so as to be able to roll between the mutually facing raceway surfaces. In this case, the rotating wheel is fixed to the wheel drive shaft constituent member by a fastening member from one side in the extending direction of the drive shaft in a state of being externally fitted to the wheel drive shaft constituent member. In at least a portion where the fastening member abuts, a predetermined hardened layer set so as to have a hardness higher than that of a nearby portion is formed.

  The rotating wheel is subjected to a predetermined surface treatment on a portion where the fastening member abuts, and a hardened layer is formed by the surface treatment. Further, the hardened layer may be formed integrally with the rotating wheel by forming the rotating wheel by tempering or by adjusting the cooling rate after hot forging. Moreover, in these bearing units, the hardness of the hardened layer is set larger than the hardness of the fastening member.

  According to the bearing unit of the present invention, by hardening the CVJ nut seat surface of the hub with which the CVJ nut abuts, it is possible to suppress loosening of the CVJ nut and to effectively prevent the generation of abnormal noise. it can.

  Hereinafter, a bearing unit of the present invention will be described with reference to the accompanying drawings. The bearing unit according to the present invention can be applied as a bearing unit that rotatably supports the wheels of various vehicles such as automobiles and railway vehicles. Here, the bearing unit that supports the wheels of the automobile is used. Is assumed as an example. Particularly in this case, such a bearing unit is assumed as an example of a bearing unit that supports driving wheels of an automobile (rear wheels of FR and RR vehicles, front wheels of FF vehicles, and all wheels of four-wheel drive vehicles). The configuration will be described. Further, the basic configuration of the bearing unit and its peripheral members according to the present embodiment is the same as the configuration of the conventional bearing unit and its peripheral members (see FIG. 2 (a)) described above. The same or similar components are denoted by the same reference numerals in the drawings, and the description thereof is omitted or simplified.

  FIG. 1 shows a bearing unit according to an embodiment of the present invention. The bearing unit includes a stationary wheel 2 fixed to a vehicle body component (for example, a knuckle (not shown) of a suspension device). These are fixed to wheel components (for example, disc wheel 42 (see FIG. 2A)) and wheel drive shaft components (for example, spline shaft 92s of constant velocity joint 92 (see FIG. 2A)). A rotating wheel 4 that rotates together with the rotating wheel 4 is provided. That is, in this case, the bearing unit is configured such that the outer ring side is the stationary ring 2 and the inner ring side is the rotating ring 4.

  Also, in such a bearing unit, a plurality of rolling elements (balls) 18a, 18b are formed between the double-row (two rows) raceway surfaces 2s, 4s formed on the stationary wheel 2 and the rotating wheel 4, respectively. It is installed so that it can roll between the raceway surfaces 2t and 4t. In this case, the rolling elements (balls) 18a and 18b are rotatably held one by one in pockets formed in the annular cage 20, and between the raceway surfaces 2s and 4s and between the raceway surfaces 2t and 4t. It is rolling between. In this embodiment, balls are used as the rolling elements 18a, 18b.For example, various rollers (tapered rollers, cylindrical rollers, spherical rollers, etc.) are used depending on the configuration and type of the bearing unit. You may apply.

  In the configuration shown in FIG. 1, a stationary flange 2 is integrally formed with a fixing flange 2 f that protrudes outward (in the direction of increasing the diameter) from the outer peripheral surface 2 a, and is fixed through the fixing flange 2 f. By inserting a fixing bolt (not shown) into the hole 2h and fastening it to the vehicle body side, the stationary wheel 2 can be fixed to a knuckle of a suspension device (suspension) not shown.

  The rotating wheel 4 is provided with a hub 12 having a substantially cylindrical shape, and the hub 12 is connected to a disc wheel of a wheel via a braking member (for example, a brake disc 40 (see FIG. 2A)). 42 (FIG. 2A) and is configured to rotate together with the disc wheel 42. The hub 12 has a disk portion 42d (FIG. 2A) of the disk wheel 42 fixed (externally fitted) on one side (left side in the figure) in the axial direction (left and right direction in FIG. 1). The hub flange 12f is continuously provided along the circumferential direction.

Further, in the configuration shown in FIG. 1, the bearing unit includes driving wheels of an automobile (FR (front engine rear wheel drive) vehicle and RR (rear engine rear wheel drive) vehicle rear wheel, FF (front engine front wheel drive). ) It is configured as a bearing unit that supports the front wheels of the vehicle and all the wheels of a four-wheel drive vehicle, and the hub 12 has one axial end to the other end (from the left end to the right end in FIG. 1). A spline hole 12t having a predetermined size is formed, and a spline shaft 92s (FIG. 2A) of a constant velocity joint is inserted into the spline hole 12t. The hub 12 can be rotated together with the spline shaft 92s by being externally fitted to the spline shaft 92s.
The hub 12 is fitted with an annular inner ring structure 16 (a member constituting the rotating wheel 4 together with the hub 12) on the other side (right side in the figure) in the axial direction (left and right direction in FIG. 1). It is like that.

In the bearing unit, the rotating wheel 4 (hub 12) is externally fitted to a wheel drive shaft constituent member (spline shaft 92s (see FIG. 2 (a))), and the drive shaft extends direction (FIG. 1). It is fixed to the spline shaft 92s (FIG. 2 (a)) by a fastening member (CVJ nut 94 (see FIG. 2 (a))) from one side (left and right side) in the left-right direction.
In this case, the hub 12 constituting the rotating wheel 4 has a flat surface continuous along the circumferential direction at one end (left side in the drawing) of the spline hole 12t in the axial direction (left-right direction in FIG. 1). A CVJ nut seat surface 12c is provided. A CVJ nut 94 (FIG. 2A) is brought into contact with the CVJ nut seat surface 12c from one side (left side in FIG. 1) in the drive shaft direction (left and right direction in FIG. 1) to tighten the rotating wheel. 4 can be positioned and fixed with respect to the spline shaft 92s (FIG. 2A). At this time, as an example, the rotating wheel 4 has an inner ring structure 16 in which one end surface of the constant velocity joint 92 (FIG. 2A) (an end surface on the outer side of the vehicle body (left side in FIG. 1)) 92a (FIG. 2A). And is fixed in a state of being sandwiched between the step portion 12s of the hub 12.

Alternatively, for example, as in the configuration shown in FIG. 2B, the rotating wheel 4 is configured such that after the inner ring component 16 is externally fitted to the step 12s of the hub 12, one side of the hub 12 (the vehicle body By caulking the inner end portion 12d (right side in FIG. 2B), the inner ring constituting body 16 is positioned and fixed in a state where it is sandwiched between the step portion 12s and the end portion 12d of the hub 12. Also good.
In any case, a predetermined preload is applied to the bearing unit by positioning and fixing the rotating wheel 4 (hub 12 and inner ring component 16).

  Further, in the rotating wheel 4, a predetermined hardened layer set so that its hardness is larger than that of a nearby portion is formed at least at a portion where the CVJ nut 94 (FIG. 2A) abuts. . In the present embodiment, as an example, the predetermined hardened layer S is formed by subjecting the CVJ nut seat surface 12c of the hub 12 to surface treatment.

  For example, the hardened layer S can be formed by subjecting the CVJ nut seat surface 12c of the hub 12 to a quenching treatment as a surface treatment. In addition, when hardening with respect to the CVJ nut seat surface 12c, as a method, various methods, such as induction hardening and carburizing hardening, can be applied besides the normal hardening method. In this case, various conditions at the time of quenching (heating method, time, temperature and speed, cooling method, time, temperature and speed, etc.) depend on, for example, the composition of the hub 12 and the set hardness after quenching. Therefore, there is no particular limitation here.

  Further, for example, the hardened layer S may be formed by subjecting the CVJ nut seat surface 12c of the hub 12 to shot peening as a surface treatment. In this case, the type and size (particle size) of the shot material to be injected are specifically set according to, for example, the composition of the hub 12 and the set hardness after quenching, and are not particularly limited here.

  Further, the hardened layer S may be formed by forming the entire hub 12 and then subjecting the CVJ nut seat surface 12c to the surface treatment such as quenching or shot peening described above. It may be formed. For example, the hardened layer S may be formed by tempering the entire hub 12, or the hardened layer S may be formed by adjusting the cooling rate after hot forging the entire hub 12. May be.

  The size, shape, depth, and the like of the hardened layer S are arbitrarily set according to, for example, the size of the hub 12 and the shape of the contact surface of the hardened layer S of the CVJ nut 94 (FIG. 2A). Therefore, there is no particular limitation here. As an example, the hardened layer S has a CVJ nut bearing surface 12c whose inner diameter is substantially the same as the diameter of the spline hole 12t and whose outer diameter is slightly larger than the diameter of the CVJ nut 94 (FIG. 2 (a)). What is necessary is just to form in the annular | circular shape which comprises a diameter. In this case, the hardened layer S may be formed so as to form a continuous annular shape, or may be formed so as to form an intermittent shape. In addition, the hardened layer S may be formed so as to form a multiple (for example, double) concentric ring.

  Here, in the present embodiment, the hub 12 is combined with the hardened layer S of the CVJ nut seat surface 12c and the raceway surface (outboard raceway surface) 4s for rolling the rolling elements (balls) 18a. Also, the hardened layer 40s is formed by various methods similar to those of the hardened layer S described above. In this case, the hardened layer S of the CVJ nut seat surface 12c is not integrated with the hardened layer 40s formed on the raceway surface (outboard raceway surface) 4s, that is, the hardened layer S does not reach the hardened layer 40s. It is preferable to form at a predetermined depth (distance in the left-right direction in FIG. 1).

  For example, when the hardened layer S is formed by quenching the CVJ nut seat surface 12c of the hub 12, the hardened layer having a depth of the hardened layer S formed on the raceway surface (outboard side raceway surface) 4s. Various conditions at the time of quenching (heating method, time, temperature and speed, cooling method, time, temperature and speed, etc.) are set so as not to reach 40 s, and the CVJ nut bearing surface of the hub 12 is set. A quenching process may be applied to 12c. The hardened layer S and the hardened layer 40s may be formed at the same time, or only one of them may be formed first.

  Further, the specific hardness of the hardened layer S is not particularly limited here because it is arbitrarily set according to, for example, the hardness of the CVJ nut 94 (see FIG. 2A) that abuts. However, it is preferable to set the hardened layer S so that at least the hardness thereof is a predetermined hardness larger than the hardness of the CVJ nut 94 (FIG. 2A). As an example, in the present embodiment, the CVJ nut 94 has a hardness based on the Vickers hardness (Hv) set to Hv 500 or higher, and the hardened layer S has a predetermined value larger than at least the Hv 500 that is the hardness of the CVJ nut 94. What is necessary is just to set so that it may become (hardness (Hv)). Thereby, the abrasion which arises between the hardened layer S of the CVJ nut seat surface 12c which mutually contacts, and the contact surface of the CVJ nut 94 (FIG. 2 (a)) can be suppressed.

  On the other hand, in this embodiment, as an example, the hub 12 and the CVJ nut 94 (FIG. 2A) are made of the same kind of metal (for example, the same kind of structural steel for machinery). That is, the CVJ nut seat surface 12c (hardened layer S) of the hub 12 and the contact surface of the CVJ nut 94 (FIG. 2 (a)) that are in contact with each other are made of the same type of metal (for example, the same type of structural steel for machinery, etc. ). Thereby, the surface frictional force (friction resistance) in the contact portion can be increased.

  As described above, by forming the hardened layer S on the CVJ nut seating surface 12c of the hub 12, the hardened layer S of the CVJ nut seating surface 12c and the CVJ nut 94 (FIG. 2 (a)) contact each other. It is possible to effectively prevent wear at the contact portion and at the same time effectively increase the surface friction force (friction resistance). Thereby, in the bearing unit, the looseness of the CVJ nut 94 (FIG. 2A) can be suppressed, and as a result, it is possible to effectively prevent the generation of abnormal noise from the bearing unit.

Sectional drawing which shows the structural example of the bearing unit which concerns on one Embodiment of this invention. FIG. 4 is a diagram illustrating a conventional bearing unit, in which (a) is a cross-sectional view illustrating a configuration example in which a rotating wheel is fastened and fixed;

Explanation of symbols

2 Static wheel 2s, 2t, 4s, 4t Raceway surface 4 Rotating wheel 12 Hub 12c CVJ nut seat surface 16 Inner ring structure 18a, 18b Rolling body (ball)
S Hardened layer

Claims (4)

A stationary wheel fixed to the vehicle body constituting member, a rotating wheel fixed to the wheel constituting member and the wheel drive shaft constituting member and rotating therewith, and a raceway surface formed on each of the stationary wheel and the rotating wheel and facing each other A plurality of rolling elements incorporated so as to be capable of rolling in between,
The rotating wheel is fixed to the wheel drive shaft constituent member by a fastening member from one side in the extending direction of the drive shaft in a state of being externally fitted to the wheel drive shaft constituent member. A bearing unit, wherein a predetermined hardened layer set so as to have a higher hardness than a nearby portion is formed at a portion where the fastening member abuts.   2. The bearing unit according to claim 1, wherein a predetermined surface treatment is applied to a portion where the fastening member contacts the rotating wheel, and a hardened layer is formed by the surface treatment.   The bearing unit according to claim 1, wherein the hardened layer is formed simultaneously with the rotating wheel by forming the rotating wheel by tempering or by adjusting a cooling rate after hot forging. The bearing unit according to claim 1, wherein the hardened layer has a hardness greater than that of the fastening member.

Images