JPH094642A - Bearing unit for wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make any plastic deformation hard to take place in an intermediate part by forming a hardened layer across the total width of the intermediate part positioned between adjacent inner raceway tracks from the inner raceway track parts in plural lines and making the outer diameter of a hardened layer formed on this intermediate part smaller than the outer diameter of a hardened layer formed in inner raceway track parts in plural lines. SOLUTION: The outer diameter of a hardened layer 12 in an intermediate portion 15 is smaller than the outer diameter of the hardened layer 12 formed on the surfaces of respective inner raceway tracks 10, 10. Therefore, thickness and size of parts other than the hardened layer 12 including raw part, etc., existing on the circumference of the hardened layer 12 formed on the inner peripheral surface of the intermediate portion 15 can be secured sufficiently. Also the hardened layer 12 is provided from inner raceway tracks 10, 10 parts in plural lines formed on the inner peripheral surface of an outer ring 5 to an intermediate part 15 exiting between both inner raceway tracks 10, 10. Therefore, the hardness of the intermediate part 15 is increased, and even when any excessive moment is applied to the outer ring 5 and roller bodies 3, 3 ride on the intermediate part 15, plastic deformation is made to hardly take place in this intermediate part 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION A wheel bearing unit according to the present invention is used when a wheel is rotatably supported on a kingpin or axle shaft of an automobile.

[0002]

2. Description of the Related Art Non-driving wheels of an automobile (rear wheels in an FF vehicle, front wheels in an FR vehicle) are rotatably mounted on a kingpin or axle shaft. FIG. 4 shows a structure described in Japanese Utility Model Laid-Open No. 61-159202 as an example of a bearing unit that is incorporated in such a portion to support a wheel.

This bearing unit comprises a pair of cages 1, 2
A plurality of rolling elements (balls) 3 and 3 held by the pair of cages 1 and 2, and a pair of inner races 4 and 4 for abutting the inner peripheral portions of the rolling elements 3 and 3. Similarly, it is composed of an outer ring 5 that abuts the outer peripheral portions of the rolling elements 3, 3.

Outer tracks 6 and 6 having arcuate cross sections are formed on the outer peripheral surfaces of the pair of inner rings 4 and 4, respectively. And, between the outer raceways 6, 6 and one end edge are thick portions 7, 7 through which the inner peripheral portions of the plurality of rolling elements 3, 3 held by the retainers 1, 2 cannot pass. . On the other hand, the outer track 6,
Between the 6 and the other end edge, there are thinned portions 8, 8 through which the inner peripheral portions of the rolling elements 3, 3 can pass.

[0005] The outer ring 5 for mounting the wheel has an intermediate portion on the inner peripheral surface, which is a small-diameter intermediate portion through which the outer peripheral portions of the plurality of rolling elements 3 held by the retainers 1 and 2 cannot pass. It is part 9. Then, both sides of the intermediate portion 9 are brought into contact with the outer peripheral portions of the plurality of rolling elements 3, 3 held by the pair of cages 1, 2, and the inner orbits 10, 1 having an arc-shaped cross section are brought into contact.
It is set to 0. The mounting flange 1 is attached to the outer peripheral surface of the outer ring 5.
1 is formed so that a wheel can be mounted and fixed on the outer ring 5.

[0006] The kingpin or axle shaft of the vehicle is inserted and fixed in the pair of inner rings 4,4. Then, based on the rotation of the outer ring 5 based on the rolling of the plurality of rolling elements 3, 3, the wheel is rotatably supported with respect to the kingpin or the axle shaft. The outer ring 5 is integrally formed by subjecting a carbon steel material to forging, and the inner races 10 and 10 formed on the inner peripheral surface of the outer ring 5 are hardened by induction hardening or the like. The layers 12, 12 are formed. And
The hardened layers 12 and 12 prevent the rolling elements 3 and 3 from being strongly pressed against the inner raceways 10 and 10, but the inner raceways 10 and 10 are not deformed such as dents.

A seal member 13 is fitted and fixed to the fitting portion 16 existing on the inner peripheral surface of the end portion of the outer ring 5. This seal member 13 closes an open end of a space 14 existing between the inner peripheral surface of the outer race 5 and the outer peripheral surface of the inner race 4,
Prevent rainwater and dust from entering inside.

[0008]

However, the conventional wheel bearing unit constructed and operated as described above has the following disadvantages. That is, on the inner peripheral surface of the outer ring 5 that constitutes the conventional wheel bearing unit, the intermediate portion 9 located between the pair of inner raceways 10, 10 is not provided with the hardened layer 12, and the intermediate portion 9 is It remains in a raw state. Therefore, when an excessive moment is applied to the outer ring 5 by a wheel fixed to the outer ring 5 riding on a curb of the road, the balls 3 and 3 are disengaged from the hardened layer 12, and the raw intermediate portion 9 is left. There was a possibility to get on. Then, when the balls 3, 3 ride on the intermediate portion 9, there is a possibility that plastic deformation occurs in the intermediate portion 9.

Intermediate portion 9 deviating from the inner tracks 10, 10.
Anyway, if the above-described plastic deformation occurs, it is not preferable because it may cause deterioration of the bearing performance of the wheel bearing unit. The wheel bearing unit of the present invention eliminates the above-mentioned inconvenience.

[0010]

A bearing unit for a wheel according to the present invention is, like the above-mentioned conventional bearing unit for a wheel, integrally made of carbon steel so as to have a cylindrical shape as a whole and has an inner peripheral surface. An outer race having a double-row inner raceway and a mounting flange formed on the outer circumferential surface; and a pair of inner races having an outer raceway formed on the outer circumferential surface and having an outer raceway facing the inner raceway; It is composed of a plurality of rolling elements provided between the inner raceway and the outer raceway, and by hardening a part of the carbon steel, a hardened layer is formed on the surface of the inner raceway. In particular, in the bearing unit for a wheel of the present invention, the hardened layer is extended from the inner raceway portion to an intermediate portion located between adjacent inner raceways, and the hardened layer formed on the intermediate portion. Has an outer diameter smaller than that of the hardened layer formed on the surface of the double-row inner raceway.

[0011]

The bearing action of the wheel bearing unit of the present invention constructed as described above is the same as that of the conventional wheel bearing unit described above. That is, the kingpin or axle shaft of the vehicle inserted and fixed inside the inner ring and the wheel fixed outside the outer ring are rotatable based on the rolling of a plurality of rolling elements.

Particularly, in the wheel bearing unit of the present invention, since the hardened layer is provided so as to extend from the inner raceway portion to the intermediate portion located between the adjacent inner raceways, the outer ring is excessively large. Even if a large moment is applied, it becomes difficult for plastic deformation to occur in the intermediate portion.

[0013]

1 is a cross-sectional view showing a first example of an embodiment of a wheel bearing unit of the present invention. A plurality of rolling elements 3, 3 are provided in each of the pair of cages 1, 2,
Holds freely rolling. The inner peripheral portion of each of these rolling elements 3, 3 is an outer raceway 6, 6 formed on the outer peripheral surface of the pair of inner rings 4, 4, and the outer peripheral portion is an inner raceway 10 formed on the inner peripheral surface of the outer ring 5. 10 are brought into contact with each other. or,
A mounting flange 11 is formed on the outer peripheral surface of the outer ring 5 so that a wheel can be mounted and fixed on the outer ring 5.

The outer ring 5 is integrally formed by forging carbon steel. On the inner peripheral surface of this outer ring 5,
Since the outer peripheral portions of the plurality of rolling elements 3 and 3 are brought into contact with each other as described above, the pair of inner raceways 10 and 10 are formed. The hardened layers 12, 12 are formed on the surfaces of the inner raceways 10, 10 by induction hardening or the like.

Further, the fitting portion 1 provided on the inner peripheral surface of the end portion of the outer ring 5
A seal member 13 is fitted and fixed in 6 to close an opening end of a space 14 existing between the inner peripheral surface of the outer ring 5 and the outer peripheral surface of the inner ring 4, and rainwater and dust enter the space 14. We try to prevent that. The hardened layer 12 formed on the surface of the inner track 10 adjacent to the fitting portion 16 also
Has not been reached. Accordingly, the time required for machining for accurately finishing the inner diameter of the fitting portion 16 in order to fix the inside of the sealing member 13 can be shortened.

The above structure is the same as that of the conventional wheel bearing unit described above. Particularly, in the wheel bearing unit of the present invention, the hardened layer 12 is formed by the inner race 1
It is provided so as to extend from the 0, 10 portion to the intermediate portion 15 existing between both inner orbits 10, 10. Of the hardened layer 12 formed continuously with the pair of inner tracks 10 and 10 and the intermediate portion 15, the hardened layer 12 of the intermediate portion 15 is formed.
Has an outer diameter smaller than the outer diameter of the hardened layer 12 formed on the surface of each of the inner raceways 10, 10. Therefore, the thickness of the raw portion which is not hardened by quenching and exists around the hardened layer 12 formed on the inner peripheral surface portion of the intermediate portion 15 is sufficiently secured.

The reason why the thickness of the green portion is sufficiently ensured is as follows. The hardened layer 12 formed by subjecting carbon steel to induction hardening has high hardness and is less likely to be plastically deformed, but has poor toughness and is easily cracked. Therefore, a hardened layer 12 is formed on the inner peripheral surface portion of the intermediate portion 15 to increase the hardness of the inner peripheral surface, while at the same time ensuring the thickness dimension of the raw portion to ensure toughness. ing. In the case of a wheel bearing unit, a large impact may be applied when the wheel rides on a curb. It is important to secure the toughness in order to prevent the outer ring 5 from cracking due to such an impact.

The bearing action itself of the wheel bearing unit of the present invention constructed as described above is the same as that of the conventional wheel bearing unit described above. That is, the kingpin or axle shaft of the automobile inserted and fixed inside the inner rings 4 and 4 and the wheel fixed to the mounting flange 11 provided on the outer peripheral surface of the outer ring 5 are connected to the plurality of rolling elements 3 and 3. It becomes rotatable based on rolling.

Particularly, in the wheel bearing unit of the present invention, the hardened layer 12 is provided on the inner raceway 10 of the inner peripheral surface of the outer ring 5.
It is provided so as to extend from the portion to an intermediate portion 15 existing between the two inner tracks 10, 10. Therefore, the hardness of the intermediate portion 15 becomes high (hard to be deformed), an excessive moment is applied to the outer ring 5 by a wheel fixed to the outer ring 5 riding on a curb of the road, and the rolling elements 3 and 3 are in an intermediate position. Even when riding on the portion 15, the intermediate portion 15 is less likely to undergo plastic deformation. For this reason, it is possible to prevent the performance of the wheel bearing unit from deteriorating due to the plastic deformation of the intermediate portion 15.

Next, FIGS. 2 to 3 show a second example of the embodiment of the present invention. In the case of the present embodiment, not only the hardened layer 12 is extended from the inner raceway 10 portion of the inner peripheral surface of the outer ring 5 to the intermediate portion 15, but also the fitting portion 1 into which the seal member 13 is fitted.
6, the inner track 10 and the fitting portion 16 have the same surface hardness. In this way, the inner orbit 10
By making the surface hardness of the fitting portion 16 and that of the fitting portion 16 the same, even if the surface of the inner raceway 10 and the surface of the fitting portion 16 are simultaneously finished with a single shaping grindstone, a part of this shaping grindstone is used. It is possible to make it difficult for the portion facing the fitting portion 16 to be clogged. Then, the life of the forming whetstone can be extended.

In this case, it is preferable that the hardened layer 12 extending to the fitting portion 16 be terminated by the chamfered portion 17 formed on the inner peripheral edge of the end portion of the outer ring 5, as shown in FIG. The reason for this is that the hardened layer 12 is not exposed to the end face 5a of the outer race 5, and the hardened layer 12 is hard to peel off from the uncured portion (raw portion). Other configurations and operations are the same as those in the first embodiment described above, and therefore, duplicate description will be omitted.

[0022]

Since the wheel bearing unit of the present invention is constructed as described above, even if an excessive moment is applied to the outer ring through the wheel, a part of the outer ring is plastically deformed. Is less likely to occur, and the durability of the outer ring can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first example of an embodiment of a wheel bearing unit of the present invention.

FIG. 2 is a sectional view showing the second example.

FIG. 3 is an enlarged view of a portion A in FIG. 2;

FIG. 4 is a sectional view showing an example of a conventional wheel bearing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 2 Cage 3 Roller 4 Inner ring 5 Outer ring 5a End face 6 Outer track 7 Thick section 8 Thin section 9 Intermediate section 10 Inner track 11 Mounting flange 12 Hardened layer 13 Seal member 14 Space 15 Intermediate section 16 Fitting section 17 chamfer

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[Procedure amendment]

[Submission date] August 7, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Wheel bearing unit

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION A wheel bearing unit according to the present invention is used when a wheel is rotatably supported on a kingpin or axle shaft of an automobile.

[0002]

2. Description of the Related Art Non-driving wheels of an automobile (rear wheels in an FF vehicle, front wheels in an FR vehicle) are rotatably mounted on a kingpin or axle shaft. FIG. 4 shows a structure described in Japanese Utility Model Laid-Open No. 61-159202 as an example of a bearing unit that is incorporated in such a portion to support a wheel.

This bearing unit comprises a pair of cages 1, 2
And a plurality of rolling elements (balls) 3 and 3 held by the pair of cages 1 and 2, and a pair of inner rings 4 and 4 for abutting inner peripheral portions of these rolling elements 3 and 3, respectively. Similarly, an outer ring 5 that abuts the outer peripheral portions of the rolling elements 3 is provided.

Outer tracks 6, 6 having an arcuate cross section are formed on the outer peripheral surfaces of the pair of inner rings 4, 4, respectively. Then, between the outer raceways 6, 6 and one end edge are formed as thick portions 7, 7 through which the inner peripheral portions of the plurality of rolling elements 3, 3 held by the retainers 1, 2 cannot pass. I have. On the other hand, between the outer raceways 6, 6 and the other end edge are thin portions 8, 8 through which the inner peripheral portions of the rolling elements 3, 3 can pass.

[0005] The outer ring 5 for mounting the wheel has an intermediate portion on the inner peripheral surface, which is a small-diameter intermediate portion through which the outer peripheral portions of the plurality of rolling elements 3 held by the retainers 1 and 2 cannot pass. It is part 9. Then, both sides of the intermediate portion 9 are brought into contact with the outer peripheral portions of the plurality of rolling elements 3, 3 held by the pair of cages 1, 2, and the inner orbits 10, 1 having an arc-shaped cross section are brought into contact.
It is set to 0. The mounting flange 1 is attached to the outer peripheral surface of the outer ring 5.
1 is formed so that a wheel can be mounted and fixed on the outer ring 5.

[0006] The kingpin or axle shaft of the vehicle is inserted and fixed in the pair of inner rings 4,4. Then, by the rotation of the outer ring 5 based on the rolling of the plurality of rolling elements 3, the wheels are rotatably supported on the kingpin or axle shaft.

The outer race 5 is integrally formed by forging a material made of carbon steel or the like, and the surfaces of the inner raceways 10 and 10 formed on the inner peripheral surface of the outer race 5 are induction hardened. The cured layers 12, 12 are formed by the method described above. Then, the rolling elements 3, 3 are formed by the hardened layers 12, 12 so that
Even if it is strongly pressed to 0, 10, this inner trajectory 10,
Deformation such as dents does not occur on the surface 10.

A seal member 13 is fixedly fitted in a fitting portion 16 present on the inner peripheral surface of the end of the outer ring 5. This seal member 13 closes an open end of a space 14 existing between the inner peripheral surface of the outer race 5 and the outer peripheral surface of the inner race 4,
Prevent rainwater and dust from entering inside.

[0009]

However, the conventional wheel bearing unit constructed and operated as described above has the following disadvantages. That is, the intermediate portion 9 located between the pair of inner races 10 and 10 on the inner peripheral surface of the outer ring 5 constituting the conventional wheel bearing unit is not provided with the hardened layer 12 and is provided with the intermediate portion 9. It remains raw. On the other hand, when an excessive moment load is applied to the outer ring 5 due to, for example, a wheel fixed to the outer ring 5 riding on a curb of the road, the balls 3, 3 come off the hardened layer 12, and the raw intermediate portion 9. Could get on. Then, when the balls 3, 3 ride on the intermediate portion 9, there is a possibility that plastic deformation occurs in the intermediate portion 9.

Intermediate portion 9 deviating from inner tracks 10, 10
Anyway, if the above-described plastic deformation occurs, it is not preferable because it may cause deterioration of the bearing performance of the wheel bearing unit. Even when the balls 3, 3 do not ride on the intermediate portion 9 as described above, the excessive moment load applied to the outer ring 5 causes the pair of inner races 10, 10 to move.
A large thrust load in the compression direction may be applied between them. Alternatively, even in a normal state where the excessive moment load is not applied, the pair of inner orbits 1 may be formed by the loads applied to the inner orbits 10 and 10 from the balls 3 and 3.
Between 0 and 10, a thrust load is applied in the compression direction. If the intermediate portion 9 is intact as in the prior art, the thrust load in the compression direction causes the intermediate portion 9 to remain intact.
May be plastically deformed in the compression direction, and the shape of the outer ring 3 may be distorted. When the outer ring 3 is distorted in this way, the rotational accuracy of the wheel bearing unit deteriorates, which causes vibration or deterioration of durability.

On the other hand, the microfilm disclosed in Japanese Utility Model Application No. 57-71467 (Japanese Utility Model Application Laid-Open No. 58-173502) includes not only a pair of inner races formed on the inner peripheral surface of the outer ring, but also these 1 An invention is described in which a hardened layer is formed even in an intermediate portion existing between a pair of inner orbits. However,
In the case of the invention described in this microfilm, the outer diameter of the hardened layer formed in the intermediate portion is made larger than the outer diameter of the hardened layer formed in the pair of inner raceway portions.

However, if the thickness of the hardened layer existing in the intermediate portion between the pair of inner raceways formed on the inner peripheral surface of the outer ring becomes large, it becomes difficult to secure the toughness of the outer ring. . That is, the hardened layer obtained by quenching steel is not easily deformed by a large load or an impact load, but is easily cracked when subjected to an impact load.
As in the invention described in the microfilm, when the hardened layer existing in the intermediate portion is thick, it is difficult to secure the toughness of the outer ring, and it is difficult to prevent the outer ring from cracking due to an impact load.

In particular, when the thickness of the outer ring is reduced in order to reduce the weight of the wheel bearing unit, such cracks are generated.
More likely to occur. Therefore, in the case of the invention described in the microfilm, it is difficult to ensure the reliability of the wheel bearing unit. The wheel bearing unit of the present invention,
The invention was made in view of such circumstances.

[0014]

A bearing unit for a wheel according to the present invention is, like the above-mentioned conventional bearing unit for a wheel, integrally made of carbon steel so as to have a cylindrical shape as a whole and has an inner peripheral surface. Outer rings each having a double row inner raceway and mounting flanges on the outer circumferential surface, a pair of inner races each having an outer raceway opposed to the inner raceway on each outer circumferential surface, and each inner raceway described above. And a plurality of rolling elements provided between each outer raceway, and a hardened layer is formed on the surface of each inner raceway.

Particularly, in the wheel bearing unit of the present invention, the hardened layer is formed over the entire width of the intermediate portion located between the inner rows of the double rows and the adjacent inner races. In addition, the outer diameter of the hardened layer formed in the intermediate portion is made smaller than the outer diameter of the hardened layer formed in the double-row inner track portions.

[0016]

The bearing action of the wheel bearing unit of the present invention constructed as described above is the same as that of the conventional wheel bearing unit described above. That is, the kingpin or axle shaft of the vehicle inserted and fixed inside the inner ring and the wheel fixed outside the outer ring are rotatable based on the rolling of a plurality of rolling elements.

In particular, in the wheel bearing unit of the present invention, the hardened layer is provided over the entire width of the intermediate portion located between the inner rows of the double rows and the adjacent inner tracks.
Even if an excessive moment load is applied to the outer ring, plastic deformation does not easily occur in the intermediate portion. Therefore, deformation of the outer race is prevented, rotation accuracy of the wheel bearing unit is ensured, and generation of vibration or deterioration of durability can be prevented.

Further, since the outer diameter of the hardened layer formed in the intermediate portion is smaller than the outer diameter of the hardened layer formed in the double-row inner raceway portion, the toughness of the outer ring is secured, Even when an impact load is applied to the outer ring, the outer ring can be prevented from cracking and the reliability of the wheel bearing unit incorporating the outer ring can be improved.

In the case of the wheel bearing unit of the present invention, a pair of inner races are formed on the inner peripheral surface of the outer ring while double rows of inner raceways are formed on the outer peripheral surface. Since it is arranged inside the outer ring, an appropriate preload can be applied to the plurality of rolling elements. That is, when the outer ring having a double row inner raceway formed on its inner peripheral surface and the single inner ring having a double row outer raceway formed on its inner peripheral surface are combined, these inner raceways are It becomes difficult to apply an appropriate preload to the rolling element provided between the rolling element and the outer raceway. In the case of a wheel bearing unit in which an appropriate preload is not applied to the rolling elements, rattling occurs in the radial direction and the thrust direction, so that vibrations and noise generated during running of the vehicle are likely to increase.
On the other hand, in the case of the structure in which a pair of inner rings is provided as in the present invention, a desired preload is applied to the rolling element by bringing the pair of inner rings close to each other after the rolling element is installed. Since it can be performed, it is possible to suppress the above vibration and noise to a low level.

[0020]

FIG. 1 is a sectional view showing a first embodiment of the present invention. A plurality of rolling elements 3 are respectively held on the pair of retainers 1 and 2 so as to freely roll. The inner peripheral portion of each of these rolling elements 3 and 3 is formed on outer raceways 6 and 6 formed on the outer peripheral surface of a pair of inner races 4 and 4, and the outer peripheral portion is formed on the inner race surface of a pair of inner races 4 and 4. Orbit 1
0 and 10 respectively. Further, a mounting flange 11 is formed on the outer peripheral surface of the outer ring 5 so that a wheel can be mounted and fixed on the outer ring 5.

The outer ring 5 is integrally formed by forging carbon steel. On the inner peripheral surface of this outer ring 5,
As described above, in order to make the outer peripheral portions of the plurality of rolling elements 3 abut against each other, the double-row inner tracks 10 are formed. The hardened layers 12, 12 are formed on the surfaces of the inner raceways 10, 10 by induction hardening or the like.

A fitting portion 1 provided on the inner peripheral surface of the end of the outer race 5
A seal member 13 is fitted and fixed in 6 to close an opening end of a space 14 existing between the inner peripheral surface of the outer ring 5 and the outer peripheral surface of the inner ring 4, and rainwater and dust enter the space 14. We try to prevent that. The hardened layer 12 formed on the surface of the inner track 10 adjacent to the fitting portion 16 also
Has not been reached. Accordingly, the time required for machining for accurately finishing the inner diameter of the fitting portion 16 in order to fix the inside of the sealing member 13 can be shortened.

The above structure is the same as that of the conventional wheel bearing unit described above. Particularly, in the wheel bearing unit of the present invention, the hardened layer 12 is separated from the double-row inner races 10 and 10 by the two inner races 10 and 10.
The intermediate portion 15 is formed over the entire width of the intermediate portion 15 existing therebetween. In the hardened layer 12 continuously formed on the inner races 10 and 10 and the intermediate portion 15 in the double row, the intermediate portion 15
The outer diameter of the hardened layer 12 is smaller than the outer diameter of the hardened layer 12 formed on the surface of each of the inner raceways 10, 10. Therefore,
It is possible to sufficiently secure the thickness dimension of the portion other than the hardened layer 12, including the raw portion, existing around the hardened layer 12 formed on the inner peripheral surface portion of the intermediate portion 15.

As described above, the outer diameter of the hardened layer 12 existing in the intermediate portion 15 is suppressed to be small and the thickness of the hardened layer 12 is suppressed to ensure the toughness of the outer ring 5. That is, the hardened layer 12 formed by subjecting the carbon steel to induction hardening has high hardness and is hardly deformed, but has poor toughness and is easily cracked. Therefore, the intermediate portion 15
A hardened layer 12 is formed on the inner peripheral surface portion of the outer ring 5 to increase the hardness of the inner peripheral surface portion while suppressing the thickness of the hardened layer 12 to ensure the toughness of the outer ring 5. When the wheel bearing unit is used, a large impact load may be applied to the outer ring 5 from the mounting flange 11 side when the wheel rides on a curb. Due to such an impact load, the outer ring 5
It is important to ensure the above toughness in order to prevent cracking.

The bearing action itself of the wheel bearing unit of the present invention constructed as described above is the same as that of the conventional wheel bearing unit described above. That is, the wheels fixed to the mounting flange 11 provided on the outer peripheral surface of the outer ring 5 with respect to the kingpin or axle shaft of the vehicle inserted and fixed inside the inner rings 4, 4 It becomes freely rotatable based on.

In particular, in the wheel bearing unit of the present invention, the two inner raceways 10, 1 are formed from the double-row inner races 10, 10 in which the hardened layer 12 is formed on the inner peripheral surface of the outer race 5.
It is provided even to the intermediate part 15 existing between 0. For this reason, the hardness of the intermediate portion 15 is increased (it is difficult to deform), and an excessive moment load is applied to the outer ring 5 due to, for example, a wheel fixed to the outer ring 5 riding on a curb of a road.
Even when the rolling elements 3 ride on the intermediate portion 15, plastic deformation is less likely to occur in the intermediate portion 15. or,
Even when a thrust load in the compression direction is applied to the intermediate portion 15 from the rolling elements 3 and 3, the intermediate portion 15 is less likely to be plastically deformed. For this reason, it is possible to prevent the performance of the wheel bearing unit from deteriorating due to the plastic deformation of the intermediate portion 15.

Further, since the outer diameter of the hardened layer 12 formed on the intermediate portion 15 is smaller than the outer diameter of the hardened layer 12 formed on the inner rows 10 and 10 of the double rows, The thickness of the hardened layer 12 existing in the portion close to the inner diameter of the portion 15 is suppressed, and the thickness dimension of the portion other than the hardened layer 12 existing in the intermediate portion 15 can be sufficiently ensured. For this reason, the toughness of the outer ring 5 is sufficiently ensured, and even when a large impact load is applied to the outer ring 5, the outer ring 5 can be prevented from breaking.

Further, while a plurality of rows of inner raceways 10 and 10 are formed on the inner peripheral surface of the outer ring 5, a pair of inner races 8 and 8 having outer raceways 6 and 6 formed on the outer peripheral surfaces thereof, respectively, Outer ring 5
Since it is arranged inside, it is possible to apply an appropriate preload to the plurality of rolling elements 3, 3. That is, when the outer ring 5 having the double-row inner raceways 10 and 10 formed on the inner peripheral surface thereof and the single inner ring having the double-row outer raceways formed on the inner peripheral surface thereof are combined, It becomes difficult to apply an appropriate preload to the rolling elements provided between the inner races 10 and 10 and the outer races.
In the case of a wheel bearing unit in which an appropriate preload is not applied to the rolling elements, rattling occurs in the radial direction and the thrust direction, so that vibrations and noises generated during running of the vehicle are likely to increase. On the other hand, as in the present invention, 1
In the case of the structure in which the pair of inner rings 8 and 8 are provided, the pair of inner rings 8 and 8 are brought close to each other after the rolling bodies 3 and 3 are installed, so that the desired preload is applied to the rolling bodies 3 and 3. Since it can be added, the vibration and noise can be suppressed to a low level.

Next, FIGS. 2 to 3 show a second example of the embodiment of the present invention. In the case of this example, the hardened layer 12 is extended not only from the inner races 10 and 10 of the inner peripheral surface of the outer ring 5 to the intermediate portion 15, but also to the fitting portion 16 into which the seal member 13 is fitted. By providing the inner track 10 and the fitting portion 16, the surface hardness of the inner race 10 is the same. In this way, by making the surface hardness of the inner raceway 10 and the fitting portion 16 the same, even if the surface of the inner raceway 10 and the surface of the fitting portion 16 are simultaneously finished by a single forming grindstone. It is possible to prevent clogging of a part of the forming grindstone that faces the fitting portion 16. Then, the life of the forming whetstone can be extended.

In this case, it is preferable that the hardened layer 12 extending to the fitting portion 16 is terminated by the chamfered portion 17 formed on the inner peripheral edge of the end portion of the outer ring 5, as shown in FIG. The reason for this is that the hardened layer 12 is not exposed to the end face 5a of the outer race 5, and the hardened layer 12 is hard to peel off from the uncured portion (raw portion). Other configurations and operations are the same as those in the case of the above-described first example, and thus redundant description will be omitted.

[0031]

Since the wheel bearing unit of the present invention is constructed as described above, even when an excessive moment load is applied to the outer ring via the wheel, a part of the outer ring becomes plastic. Deformation can hardly occur. Moreover, since the toughness of the outer ring can be secured while preventing such plastic deformation, the outer ring and the bearing unit for a wheel incorporating the outer ring are prevented from being plastically deformed, and the outer ring is prevented from being cracked by an impact load. Therefore, reliability can be improved. As a result, it is also possible to achieve both reduction in the weight of the wheel bearing unit and securing of reliability. Furthermore, by applying an appropriate preload to the rolling elements, it is possible to suppress the vibration and noise generated during the operation of the wheel bearing unit to a low level.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first example of an embodiment of a wheel bearing unit of the present invention.

FIG. 2 is a sectional view showing the second example.

FIG. 3 is an enlarged view of a portion A in FIG. 2;

FIG. 4 is a sectional view showing an example of a conventional wheel bearing unit.

[Explanation of Codes] 1, 2 Cage 3 Rolling element 4 Inner ring 5 Outer ring 5a End face 6 Outer raceway 7 Thick wall portion 8 Thin wall portion 9 Intermediate portion 10 Inner raceway 11 Mounting flange 12 Hardened layer 13 Sealing member 14 Space 15 Intermediate Part 16 Fitting part 17 Chamfer part

Claims (1)

[Claims] 1. An outer ring integrally formed of carbon steel and formed into a cylindrical shape. The inner race has a double row inner raceway and the outer circumferential surface has a mounting flange, and the inner raceway. And a plurality of rolling elements provided between the inner race and the outer race. In a bearing unit for a wheel in which a hardened layer is formed on the surface of the inner raceway by hardening a part of the inner raceway, the hardened layer is formed in an intermediate portion located between the inner raceway portions and adjacent inner raceways. A bearing unit for a wheel, characterized in that the outer diameter of the hardened layer formed in the middle portion is made smaller than the outer diameter of the hardened layer formed on the surface of the double-row inner raceway.