JP2005319966A - Bearing device for supporting wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deformation of a flange face without altering the shape and dimension of a flange and without being accompanied by alteration of the material. <P>SOLUTION: This bearing system for supporting a wheel is used in a state where a rotator for braking and the wheel are joined and fixed to a side face of the flange 6 formed on the outer peripheral face of a hub ring 2 through a hub bolt 10. The hub ring 2 is made of copper and has a hardened/tempered layer 20 on at least one side face of the flange 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement in a bearing device for supporting a wheel provided with a flange for supporting a wheel of an automobile or the like, and a braking rotor such as a brake rotor or a brake drum.

  As a conventional wheel support bearing device of this type, for example, the one shown in FIG. 1 is known. The wheel support bearing device 1 includes a hub wheel 2, an inner ring 3, an outer ring 4, and a plurality of rolling elements 5. A wheel mounting flange 6 is provided on an end portion on the outboard side of the outer peripheral surface of the hub wheel 2 (an end portion on the outer side in the vehicle width direction in the assembled state in the automobile: the left end portion in FIG. 1). A plurality of hub bolts 10 for mounting a wheel and a brake rotor are planted on the side surface of the flange 6 on the outboard side at substantially equal intervals in the circumferential direction.

  In addition, a small-diameter step 8 is formed at the inboard side end of the hub wheel 2 (the inner end in the vehicle width direction in the assembled state on the automobile: the right end in FIG. 1). An inner ring raceway surface 9 is formed on the outer peripheral surface of the fitted inner ring 3, and an inner ring raceway surface 7 is formed on the outer peripheral surface of the hub ring 2 in the axial direction. The tip of the hub wheel 2 on the inboard side is formed in a cylindrical shape, and the inner ring 3 is caulked and fixed to the hub wheel 2 by caulking and expanding the cylindrical portion (caulking portion) 12 radially outward. ing. In addition, the inner ring | wheel 3 may give required pressurization by fastening with a nut other than caulking.

  An outer ring raceway surface 15 corresponding to the inner ring raceway surface 7 of the hub ring 2 and an outer ring raceway surface 16 corresponding to the inner ring raceway surface 9 of the inner ring 3 are formed on the inner peripheral surface of the outer ring 4. A suspension device mounting flange 17 is provided at an end portion on the side away from the wheel mounting flange 6. A plurality of rolling elements 5 are arranged between the double row inner ring raceway surfaces 7 and 9 and the double row outer ring raceway surfaces 15 and 16, respectively, so as to be able to roll in the circumferential direction via the cage 14. .

In the illustrated example, a ball is used as the rolling element 5, but a tapered roller may be used as the rolling element 5 in the case of a heavy wheel support bearing device.
Further, the region from the base portion on the inboard side of the wheel mounting flange 6 of the hub wheel 2 to the small-diameter step portion 8 through the inner ring raceway surface 7 is used for securing a rolling fatigue life and preventing fretting of the inner ring fitting portion. Therefore, a hardened layer T is formed by induction hardening.

In order to assemble the wheel support bearing device 1 as described above to an automobile, the suspension device mounting flange 17 of the outer ring 4 on the non-rotating wheel side is fixed to the suspension device, and the wheel mounting flange of the hub wheel 2 on the rotating wheel side is fixed. A brake rotor and a wheel are fixed to 6 via a hub bolt 10 and a nut (not shown). Thereby, a wheel can be rotatably supported with respect to a suspension apparatus.
By the way, the wheel mounting flange 6 formed on the hub wheel 2 on the rotating wheel serves as a reference surface for mounting the brake rotor. However, when the flange 6 is made thinner for the purpose of weight reduction, the hub bolt 10 and When a torque necessary for fastening with the nut is applied, a stress greater than the yield strength of the material is generated around the bolt hole 11 of the hub bolt 10, and plastic deformation on the micron order occurs on the flange surface of the reference surface.

As a means for preventing such plastic deformation of the flange surface, the wheel mounting flange 6 is made thicker, which goes against the flow of weight reduction and thinning. In addition, high yield strength can be achieved by increasing the carbon concentration of the material and adding Si, Mn, and V as strengthening elements, but an increase in cost is inevitable.
Furthermore, although means (for example, refer to Patent Document 1) for applying a hardened layer only to the base portion of the flange 6 is disclosed, there is no mention of minute deformation of the flange.
JP 2002-87008 A

  The present invention has been made to eliminate the above-described disadvantages, and can suppress the deformation of the flange surface without changing the shape and dimensions of the flange and without changing the material. An object of the present invention is to provide a wheel support bearing device.

In order to achieve the above object, the invention according to claim 1 includes a hub wheel having an inner ring raceway surface formed on the outer peripheral surface, and an outer ring surface formed on the outer peripheral surface while being fitted on the end of the hub ring. An outer ring formed with an inner ring raceway surface of the hub ring and a double row outer ring raceway surface corresponding to the inner ring raceway surface of the inner ring, an inner ring raceway surface of the hub ring and an inner ring raceway surface of the inner ring, A plurality of rolling elements arranged to be freely rollable between the double row outer ring raceway surfaces; and a flange formed on an outer peripheral surface of the raceway which is a rotation side of the hub ring and the outer ring; A wheel support bearing device used in a state in which a braking rotor and a wheel are coupled and fixed to a side surface of the flange via a bolt or a bolt and a nut,
The bearing ring on the rotating side is made of steel with a quenching and tempering layer provided on at least one side surface of the flange.

The invention according to claim 2 is characterized in that, in claim 1, the hardness of the quenched and tempered layer provided on the flange is HRC20 to 64, preferably HRC20 to 39.
According to a third aspect of the present invention, in the first or second aspect, the range of the quenching and tempering layer provided on the flange is a hole diameter of the bolt hole centered on a PCD (pitch circle diameter) of the bolt hole of the bolt. It is characterized by being 1.5 times or more.

Here, when a quenching and tempering layer is provided on the side surface (side surface on the outboard side) that becomes the mounting surface of the flange braking rotor by induction hardening, the quenching and tempering layer should not be applied to the pilot portion and the R portion of the flange base. Is preferred.
Moreover, since the problem of heat treatment deformation tends to occur when the quenching and tempering layer is deep, the depth of the quenching and tempering layer is preferably in the range of 0.5 to 2.0 mm.
Further, the bearing ring on the rotating side may be made of carbon steel having C of 0.40% by weight or more and 0.80% by weight or less in order not to lower the machinability in order to obtain necessary rolling fatigue strength. preferable.

  According to the present invention, since the raceway on the rotating side is made of steel with a quenching and tempering layer provided on at least one side surface of the flange, the shape of the flange is not changed and the material is changed. And deformation of the flange surface can be suppressed.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. In addition, since the basic structure of the wheel support bearing device of this embodiment is substantially the same as that described with reference to FIG. 1, the description will be made with reference to FIG.
The wheel support bearing device as an example of the embodiment of the present invention includes a brake rotor 21 and a wheel 22 on the side surface on the outboard side of the wheel mounting flange 6 formed on the outer peripheral surface of the hub wheel 2 on the rotation side. (See FIG. 2) are used in a state where they are coupled and fixed by a hub bolt 10 and a nut (not shown).

  The hub wheel 2 is made of steel provided with a quenching and tempering layer 20 (see FIGS. 4 to 7) on at least one side surface of the wheel mounting flange 6, and the hardness of the quenching and tempering layer 20 is set to HRC 20 to 64. In addition, the range of the quenching and tempering layer 20 is set to 1.5 times or more the hole diameter of the bolt hole 11 around the PCD (pitch circle diameter) of the bolt hole 11 of the hub bolt 10.

The deformation of the flange 6 occurs because the contact point with the wheel exists on a circumference wider than the bolt hole 11 (see FIG. 2), and the axial force of the hub bolt 10 acts on the flange 6 as a bending deformation force. . To suppress the deformation of the flange 6 is to improve the yield strength around the bolt hole 11 and to keep more area within the elastic limit.
For this purpose, a quenching and tempering layer 20 is formed by induction hardening around the bolt hole 11 on at least one side surface of the flange 6.

Since the deformation amount of the flange 6 is extremely small compared to the general plastic deformation amount on the order of microns and is a region slightly exceeding the elastic limit, the present inventors increase the strength of the portion responsible for the deformation. It was found that the deformation of the flange 6 can be suppressed.
Further, the microstructure of the quenched and tempered layer 20 is a structure in which carbides are uniformly dispersed in the martensite dough, and a forged and cooled structure (soft island-like ferrite and Compared with the mixed structure of pearlite, the strength characteristics are very good.

This is because the yield of the forged cool structure is preferentially deformed from a soft ferrite with a low stress, whereas the hardened region has a high average strength with little variation. As a result, the yield strength for the same hardness increases in the hardened region of the quenching and tempering layer 20.
In this way, by forming the quenching and tempering layer 20 on at least one side surface of the wheel mounting flange 6 by induction hardening, it is possible to increase the material C without changing the shape and dimensions of the wheel mounting flange 6. It is possible to suppress the deformation of the flange 6 without improving the addition of alloy elements or the like and without significantly changing the current processing method and existing equipment. Similar effects can be obtained even when the entire hub wheel 2 is uniformly heated and subjected to quenching and tempering treatment on the entire area of the hub wheel 2.

Hereinafter, the significance of numerical limitation will be described.
(Hardness of quenching and tempering layer: HRC20 to HRC64)
If the hardness of the side surface of the flange 6 is set to HRC20 or more by quenching and tempering, the yield strength is higher than that of the substrate, and the deformation of the flange 6 can be effectively suppressed. However, if HRC64 is exceeded, the impact strength is significantly reduced, so this is the upper limit. In order to obtain a higher impact strength, HRC20 to HRC39 are preferable.

(Depth of quenching and tempering layer)
Since the side surface of the flange 6 that is the mounting surface of the brake rotor 21 is a mounting reference surface, there is a possibility that there will be a considerable amount of heat treatment deformation if quench hardening is performed after turning. The deeper the quenching and tempering layer 20 is, the more easily heat treatment deformation occurs. Therefore, in order to prevent such deformation, the depth of the quenching and tempering layer 20 is preferably in the range of 0.5 to 2.0 mm.

(Range of quenching and tempering layer)
Since deformation occurs around the bolt hole 11 of the flange 6, the above effect cannot be sufficiently obtained if the hardening range by the quenching and tempering layer 20 is narrow with respect to the diameter of the bolt hole 11. Therefore, it is preferable that the range of the quenching and tempering layer 20 with respect to the 11 hole diameter for bolts is 1.5 times or more as described later.
Further, when forming the quenching and tempering layer 20 by uniformly heating the entire hub wheel 2 (see FIG. 7), it is necessary for a portion where impact strength is required such as a root portion of the flange 6 of the hub wheel 2. If the hardness is increased as described above, the impact strength may be lowered. In this case, the hardness of the quenched and tempered layer 20 needs to be HRC 20 to 39.

(Hub ring material)
In order to obtain the required rolling fatigue strength, C is required to be 0.40% by weight or more, but if it is added excessively, the machinability is lowered, so that it is preferably made of carbon steel of 0.80% by weight or less. .

In order to verify the effect of the present invention, the following experiment was conducted.
As shown in Table 1, four types of carbon steel (SAE1045, SAE1055, SAE1060, SAE1070) were cooled after hot forging and turned to provide a wheel support bearing device for a drive wheel as shown in FIG. A hub wheel 2 was produced. The main dimensions of the hub wheel 2 are a thickness t = 10 mm of the wheel mounting flange 6 and a screw hole diameter φ14 mm as a bolt hole 11 (in this example, inner tapping).

In addition, the quenching and tempering layer 20 was made into the heat treatment patterns 1 to 4 shown in FIGS. 4 to 7, and the hardness and the curing range with respect to the diameter of the bolt hole 11 were changed.
The heat treatment pattern 1 is an example in which a quenching and tempering layer 20 is formed on the side surface of the flange 6 on the inboard side. For example, the heat treatment pattern 3 is an example in which a quenching and tempering layer 20 is formed on both side surfaces of the flange 6 on the inboard side and the outboard side. FIG. 8 shows the heat treatment pattern 5 in which the quenching and tempering layer 20 is not applied.

For heat treatment patterns 1 to 3, after turning and tapping, a coil having a circumferential shape is installed at the PCD (pitch circle diameter) position of the bolt hole 11, and the hub wheel 2 is rotated around the central axis to perform induction hardening and tempering. went. The hardness of the quenched and tempered layer 20 was measured on the surface of the flange 6 and the depth was determined from the microstructure.
The heat treatment pattern 4 was uniformly heated to 840 ° C. after forging, quenched and tempered in a salt bath heated to 200 ° C. in order to prevent quench cracking, and then finished into a predetermined shape.

  Regarding the quality of the test product, the hardness of the flange 6 was measured with a Rockwell hardness meter (C scale, 150 kg) on the flange surface. The depth of the quenching and tempering layer 20 was determined by measuring the shape of a region where the flange cross-section was polished and corroded and a tempered structure in which carbides were dispersed in the matrix was formed. In the test, the brake rotor 21 and the wheel 22 were fastened to the flange 6 of the hub wheel 2 shown in FIG. 2 through the hub bolt 10 with a torque of 150 N · m. Thereafter, the hub bolt 10 was removed, and the deformation amount of the flange surface was measured at the inside and outside ± 10 mm positions with respect to the PCD position of the bolt hole 11 (see FIG. 3), and the average value of the two points was defined as the flange deformation amount Z. . The test results are shown in Table 1, FIG. 9 and FIG.

In Examples A-1 to A-16, the quenching and tempering layer 20 of 28 mm or more was applied to the bolt hole diameter φ14 mm, and the heat treatment pattern was changed, and good results were obtained. In Examples B-1 to B-4, the hardening range of the quenching and tempering layer 20 was changed with respect to the bolt hole diameter φ14 mm. The range of the quenching and tempering layer 20 (curing range) / the hole diameter of the bolt. The hardness of the hardened and tempered layer 20 is preferably HRC20 to 64, preferably HRC20 to 39, so that the flange deformation can be effectively reduced without reducing the strength of the hub wheel 2. It was found that it was possible to
On the other hand, Comparative Examples D-1 to D-4 did not provide the quenching and tempering layer 20, and a tendency to reduce the flange deformation along with the hardness was obtained, but the deformation amount was larger than that of the example.

It is sectional drawing which shows an example of the bearing apparatus for wheel support. It is the schematic which shows the state which couple | bonded and fixed the brake rotor and the wheel via the hub bolt to the side surface at the side of the outboard of the wheel mounting flange of a hub ring. It is a graph for demonstrating the flange deformation amount. FIG. 2 is a cross-sectional view of a main part showing a hub wheel in which a quenching and tempering layer is formed in a heat treatment pattern 1. It is principal part sectional drawing which shows the hub ring in which the quenching and tempering layer was formed with the heat processing pattern 2. FIG. It is principal part sectional drawing which shows the hub ring in which the hardening and tempering layer was formed with the heat processing pattern 3. FIG. It is principal part sectional drawing which shows the hub ring in which the quenching and tempering layer was formed with the heat processing pattern 4. FIG. It is principal part sectional drawing which shows the hub ring in which the hardening and tempering layer is not formed with the heat processing pattern 5. FIG. It is a graph which shows the relationship between the hardness of the quenching and tempering layer in Example and a comparative example, and a flange deformation amount. It is a graph which shows the relationship between the value of the quenching tempering layer range / the hole diameter for bolts, and a flange deformation amount in an Example and a comparative example.

Explanation of symbols

2 Hub wheel 3 Inner ring 4 Outer ring 5 Rolling element 6 Wheel mounting flange 7 Inner ring raceway surface (hub ring side)
9 Inner ring raceway surface (inner ring side)
DESCRIPTION OF SYMBOLS 10 Hub bolt 11 Bolt hole 15 Outer ring raceway surface 16 Outer ring raceway surface 20 Quenching and tempering layer 21 Brake rotor 22 Wheel

Claims (3)

A hub ring having an inner ring raceway surface formed on the outer peripheral surface, an inner ring fitted on the end of the hub ring and having an inner ring raceway surface formed on the outer peripheral surface, the inner ring raceway surface of the hub ring and the inner ring An outer ring in which a double row outer ring raceway surface corresponding to the inner ring raceway surface is formed, and an inner ring raceway surface of the hub wheel and an inner ring raceway surface of the inner ring and a double row outer ring raceway surface are movably arranged. A plurality of rolling elements provided, and a flange formed on an outer peripheral surface of a raceway ring that is a rotation side of the hub wheel and the outer ring, and a braking rotator and a wheel are provided on a side surface of the flange. In the wheel support bearing device used in a state of being coupled and fixed via bolts or bolts and nuts,
The bearing device for supporting a wheel according to claim 1, wherein the raceway on the rotating side is made of steel provided with a quenching and tempering layer on at least one side surface of the flange.   The wheel support bearing device according to claim 1, wherein the hardness of the quenching and tempering layer provided on the flange is set to HRC20 to 64.   The range of the quenching and tempering layer provided on the flange is 1.5 times or more the hole diameter of the bolt hole centering on the PCD (pitch circle diameter) of the bolt hole of the bolt. The bearing device for wheel support described in 1 or 2.

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