WO2012003848A1 - Flanged hub of a wheel bearing unit - Google Patents

Flanged hub of a wheel bearing unit Download PDF

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Publication number
WO2012003848A1
WO2012003848A1 PCT/EP2010/004188 EP2010004188W WO2012003848A1 WO 2012003848 A1 WO2012003848 A1 WO 2012003848A1 EP 2010004188 W EP2010004188 W EP 2010004188W WO 2012003848 A1 WO2012003848 A1 WO 2012003848A1
Authority
WO
WIPO (PCT)
Prior art keywords
flanged hub
heat shield
hub according
flanged
flange
Prior art date
Application number
PCT/EP2010/004188
Other languages
French (fr)
Inventor
Cornelius Petrus Antonius Vissers
Victor Haans
Daniel Back
Andreas Knopf
Original Assignee
Skf B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Skf B.V. filed Critical Skf B.V.
Priority to PCT/EP2010/004188 priority Critical patent/WO2012003848A1/en
Publication of WO2012003848A1 publication Critical patent/WO2012003848A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B27/00—Hubs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B27/00—Hubs
    • B60B27/0005—Hubs with ball bearings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B27/00—Hubs
    • B60B27/0015—Hubs for driven wheels
    • B60B27/0021—Hubs for driven wheels characterised by torque transmission means from drive axle
    • B60B27/0026—Hubs for driven wheels characterised by torque transmission means from drive axle of the radial type, e.g. splined key
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B27/00—Hubs
    • B60B27/0047—Hubs characterised by functional integration of other elements
    • B60B27/0052—Hubs characterised by functional integration of other elements the element being a brake disc
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B27/00—Hubs
    • B60B27/0078—Hubs characterised by the fixation of bearings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B27/00—Hubs
    • B60B27/0094—Hubs one or more of the bearing races are formed by the hub
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30—Parts of ball or roller bearings
    • F16C33/58—Raceways; Race rings
    • F16C33/60—Raceways; Race rings divided or split, e.g. comprising two juxtaposed rings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30—Parts of ball or roller bearings
    • F16C33/58—Raceways; Race rings
    • F16C33/64—Special methods of manufacture
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00—Parts or details
    • F16D65/02—Braking members; Mounting thereof
    • F16D65/12—Discs; Drums for disc brakes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
    • F16C19/02—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows
    • F16C19/14—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load
    • F16C19/18—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls
    • F16C19/181—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact
    • F16C19/183—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles
    • F16C19/184—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles in O-arrangement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
    • F16C19/22—Bearings with rolling contact, for exclusively rotary movement with bearing rollers essentially of the same size in one or more circular rows, e.g. needle bearings
    • F16C19/34—Bearings with rolling contact, for exclusively rotary movement with bearing rollers essentially of the same size in one or more circular rows, e.g. needle bearings for both radial and axial load
    • F16C19/38—Bearings with rolling contact, for exclusively rotary movement with bearing rollers essentially of the same size in one or more circular rows, e.g. needle bearings for both radial and axial load with two or more rows of rollers
    • F16C19/383—Bearings with rolling contact, for exclusively rotary movement with bearing rollers essentially of the same size in one or more circular rows, e.g. needle bearings for both radial and axial load with two or more rows of rollers with tapered rollers, i.e. rollers having essentially the shape of a truncated cone
    • F16C19/385—Bearings with rolling contact, for exclusively rotary movement with bearing rollers essentially of the same size in one or more circular rows, e.g. needle bearings for both radial and axial load with two or more rows of rollers with tapered rollers, i.e. rollers having essentially the shape of a truncated cone with two rows, i.e. double-row tapered roller bearings
    • F16C19/386—Bearings with rolling contact, for exclusively rotary movement with bearing rollers essentially of the same size in one or more circular rows, e.g. needle bearings for both radial and axial load with two or more rows of rollers with tapered rollers, i.e. rollers having essentially the shape of a truncated cone with two rows, i.e. double-row tapered roller bearings in O-arrangement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2220/00—Shaping
    • F16C2220/02—Shaping by casting
    • F16C2220/04—Shaping by casting by injection-moulding
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2226/00—Joining parts; Fastening; Assembling or mounting parts
    • F16C2226/30—Material joints
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2326/00—Articles relating to transporting
    • F16C2326/01—Parts of vehicles in general
    • F16C2326/02—Wheel hubs or castors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00—Parts or details
    • F16D65/02—Braking members; Mounting thereof
    • F16D2065/13—Parts or details of discs or drums
    • F16D2065/134—Connection
    • F16D2065/1384—Connection to wheel hub

Definitions

  • the present invention relates to a flanged hub of a wheel bearing unit having a flange part and a hub part which are made from different materials. More specifically, the hub part comprises a raceway made of bearing steel and the flange part predominantly comprises a second material that is joined to the hub part in a moulding process.
  • a flanged hub of the above kind is known from US6485188. Specifically, this document concerns a wheel mounting with a bearing race embedded in a cast component.
  • the cast component is a bearing outer ring with a flange for receiving a vehicle wheel and brake disc.
  • the flanged ring can be made of aluminium which is cast around an insert made of bearing steel that comprises hardened outer raceways.
  • the resulting flanged hub is lighter than a flanged hub made entirely of bearing steel, which benefits the car owner in terms of fuel economy.
  • One drawback of using aluminium instead of bearing steel is that aluminium has a higher thermal conductivity. This can be disadvantageous when an excessive amount of heat is generated due to friction between e.g. brake pads and a brake disc.
  • the present invention resides in a flanged hub of a wheel bearing unit comprising a hub part and a flange part, the hub part having a raceway made of a first material, being a bearing steel material, and the flange part having a mounting surface for the attachment of a brake rotor and vehicle wheel rim.
  • the flange part predominantly comprises a second material that is joined to the hub part in a moulding process.
  • the flange part further comprises an integrally moulded heat shield made of a third material which, in comparison with the second material, has a lower coefficient of thermal conductivity.
  • a flanged hub according to the invention inhibits heat transfer from the brake rotor to the raceway via the flange part, meaning that the raceway is protected from reaching a temperature that could reduce the hardness of the bearing steel.
  • the third material of the heat shield has a higher modulus of elasticity in axial direction than the second material.
  • flange stiffness is enhanced because the heat shield is integrally moulded in the flange part.
  • the overmoulded flange is therefore capable of withstanding higher axial bending loads than a flange of the same thickness that is made entirely from the second material. Consequently, it is also possible to reduce the thickness of the overmoulded flange while retaining a required level of strength and stiffness.
  • the heat shield is positioned at an outboard side of the flange part, such that the mounting surface is at least partly defined by an outer surface of the heat shield.
  • the outboard surface of the heat shield has a surface profile, to reduce the area of contact between the brake rotor and the mounting surface and thereby reduce heat transfer.
  • the outboard surface can be grooved, or a have certain surface roughness.
  • any parts of the mounting surface which are formed by the second material can also be grooved or roughened.
  • the second material of the flange part which is moulded to the hub part preferably comprises a lightweight metal such as aluminium, magnesium, or alloys thereof. Moulding should be understood as a process in which the second material is joined to the hub part in a moulten state or a semi-moulten state.
  • the second material is aluminium and is joined to the hub part in a semi-solid metal process, being one of a rheocasting process, a rheoforming process, a rheomoulding process, a thixocasting process, a thixoforming process or a thixomoulding process.
  • the microstructure of the cast metal or metal alloy contains interlocking dendrites that result in material brittleness.
  • the advantage of a semi-solid process is that spherical grains are formed, and the metal has fine, uniform microstructures which give enhanced mechanical properties. Semi-solid metal processing is also less susceptible to air entrapment and a component produced in this way has fewer defects and lower porosity than e.g. a cast component.
  • the second material may also be a fibre composite material comprising a polymer matrix and e.g. carbon fibres. In such examples of a flanged hub according to the invention, the second material will additionally insulate the raceway of bearing steel against potentially harmful temperature rises.
  • a heat shield remains advantageous, however, as it will protect the polymer matrix from temperature rises that could cause melting. Also, as mentioned above, by using a heat shield material with a higher elastic modulus in axial direction, flange stiffness can be enhanced.
  • Suitable materials for the heat shield include mild steel, stainless steel and ceramics, which are stiff materials and are poorer thermal conductors than most lightweight metals.
  • Stainless steel and ceramic materials have the additional advantage of being corrosion-resistant and will therefore prevent corrosion between e.g. a steel brake disc and an aluminium flange.
  • the heat shield is made of mild steel, its outboard surface may be treated with a chemically passive coating. Alternatively, the outboard surface may be given a sacrificial coating of e.g. ZnAI15, which will preferentially corrode and thereby protect the brake disc mounting surface from corrosion.
  • the heat shield consists of a disc with a circular outer periphery.
  • the heat shield can be shaped such that its outer periphery follows the geometry of the outboard face of the flange.
  • the heat shield comprises a plurality of separate, thermally insulating elements that are arranged around the outboard side face of the flange.
  • the heat shield comprises one or more axial extensions. This increases the second moment of area of the heat shield in axial direction, thereby enhancing flange stiffness. Furthermore, the one or more axial extensions provide additional surface area against which the overmoulded second material can contract as it cools, thereby improving radial locking.
  • the disc part may also comprise openings into which the overmoulded second material flows. This provides additional radial locking and also rotationally locks the heat shield with the flange.
  • the axial extensions are formed by threaded inserts for receiving mounting bolts or stud bolts.
  • Fig. 1 shows a cross-section of an example of a wheel bearing unit comprising a first embodiment of a flanged hub according to the invention
  • Fig. 2a shows a partial cross-section of a further example of a wheel bearing unit comprising a second embodiment of a flanged hub according to the invention
  • Fig. 2b is a perspective view of a heat shield used in the flanged hub of Fig.
  • Fig. 3a and 3b show a partial cross-section of further embodiments of a flanged hub according to the invention.
  • FIG. 1 An example of a wheel bearing unit 100 comprising a flanged hub 120 according to the invention is shown in Figure 1.
  • the flanged hub 120 in this example is adapted for inner ring rotation and comprises a hub part 122 made of bearing steel.
  • the hub part 122 has a radially outer surface that serves as an inner raceway 125 for an outboard row of rolling elements and further comprises a seat for a separate inner ring that forms the raceway for an in board row of rolling elements.
  • a flange part 127 of the flanged hub is made from aluminium. The aluminium of the flange part has been joined around the hub part 122 in a rheocasting process.
  • the flange part 127 generally known as the wheel mounting flange, has a mounting surface 130 to which a mounting part 142 of a brake rotor 140 and a wheel rim (not shown) are bolted.
  • a brake disc is shown in this example, but the brake rotor could also be a drum brake.
  • Heat that is generated during braking is therefore transferred to the wheel mounting flange 127 through the mounting surface 130.
  • the generated heat is then conducted through the flange 127 to the hub 122 made of bearing steel.
  • Aluminium has a higher coefficient of thermal conductivity than bearing steel, meaning that a faster rate of heat transfer occurs through the aluminium. Therefore, when an excessive amount of heat is generated in the brake rotor 140, e.g.
  • the heat that is lost through conduction and through dissipation to the surroundings may not be sufficient to prevent a harmful rise in temperature at the inboard raceway 125.
  • the inboard raceway experienced a temperature of e.g. 140 °C for 15 seconds, raceway hardness would be lost, dramatically reducing the service life of the bearing unit 100.
  • the flange 127 of a flanged hub 120 comprises an integrally moulded heat shield 150.
  • the heat shield is made of stainless steel, which has a coefficient of thermal conductivity k of 16 W/mK. Aluminium has a k-value of around 250 W/mK; bearing steel has k-value of around 30 - 45 W/mK [the given values are for a reference temperature of 25 °C].
  • the heat shield 150 in this example is a stainless steel disc, which is positioned within the flange 127 such that the mounting surface 130 is formed by an outboard surface of the heat shield.
  • a further advantage of a stainless steel mounting surface 130 is that corrosion between the flange and the mounting part 142 of the brake rotor is prevented.
  • a still further advantage of integrating a heat shield of stainless steel is improved flange stiffness.
  • Stainless steel and aluminium respectively have a modulus of elasticity of 200 and 70 GPa. Consequently, the flange 127 of the flanged hub 120 according to the invention has higher axial bending strength and stiffness than a flange of the same thickness that is entirely made from aluminium.
  • the heat shield 150 can be designed with a second moment of area in axial direction that optimises flange stiffness.
  • the heat shield may have a minimum thickness in axial direction.
  • the second moment of area of the heat shield can be increased, without increasing the weight of the shield, by effectively making the shield longer in axial direction.
  • the heat shield may comprise a disc portion, which at least partly serves as the mounting surface, and further comprise one or more axial extensions.
  • the axial extensions are formed by threaded inserts.
  • Fig. 2a An example of a wheel bearing unit comprising a flanged hub according to the further development is shown in Fig. 2a, while Fig.
  • FIG. 2b is a perspective view of the heat shield that is integrally moulded in the flange.
  • the bearing unit 200 is adapted for outer ring rotation and the hub part 222 of the flanged hub 220 comprises outer raceways for first and second rows of tapered rollers.
  • the hub part 222 is made from bearing steel and the flange 227 in this example is predominantly made of aluminium, which has been joined to the hub part in a rheocasting process.
  • the integrally moulded heat shield 250 is made of mild steel in this example.
  • the heat shield 250 comprises a disc part 255, against which the brake rotor mounting part 242 is mounted.
  • the heat shield further comprises a plurality of axial extensions 257 having an inner thread 260 for receiving e.g. stud bolts.
  • the stud bolts connect the brake rotor mounting part 242 to the flange 227, and consequently form an additional path for heat conduction from the brake rotor 240 to the overmoulded material of the flange.
  • the internally threaded axial extensions 257 of the heat shield 250 therefore retard heat transfer, providing the flanged hub with additional thermal protection.
  • a further advantage of incorporating internally threaded extensions in the heat shield is that the necessary flange mounting holes can be accurately positioned and toleranced.
  • the axial extensions 257 of the heat shield rotationally lock the heat shield 250 within the flange 227 and provide additional surface area against which the overmoulded flange material can contract as it cools. Contraction takes place in a radially inward direction, meaning that radially outer surfaces of the heat shield effectively serve as attachment interfaces.
  • the flange 127 has a larger outer circumference than the heat shield 150. Consequently, a portion of the overmoulded aluminium is able to contract against the outer circumferential surface of the shield 150. Needless to say, increasing the surface area against which the cooling aluminium can contract leads to better retention of the heat shield within the flange.
  • the disc part 255 of the heat shield comprises a plurality of openings 256.
  • the semi-solid aluminium also flows into these openings and provides additional retention.
  • FIG. 3a depicts part of a further embodiment of a flanged hub 320a according to the invention.
  • the heat shield 350a is a disc with openings 356. Consequently, the outer circumference of the shield forms a first attachment interface 365 and the radially outer surface 367 of the heat shield at the openings 356 form a second attachment interface.
  • FIG. 3b A still further embodiment of a flanged hub according to the invention is shown, in part, in Fig. 3b.
  • the flanged hub 320b comprises a still further example of a heat shield 350.
  • the heat shield is formed by a disc, whereby an outer periphery of the disc has been bent over, thereby creating an axial extension in the form of a lip 357.
  • the lip 357 not only provides an attachment interface of increased surface area, but also increases the second moment of area of the heat shield 350b.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Rolling Contact Bearings (AREA)

Abstract

The present invention resides in a flanged hub (120) of a wheel bearing unit (100) comprising a hub part (122) and a flange part (127), the hub part having a raceway (125) made of a bearing steel material and the flange part having a mounting surface (130) for the attachment of a brake rotor (140) and vehicle wheel rim. The flange part (127) predominantly comprises a second material that is joined to the hub part in a moulding process. According to the invention, the flange part further comprises an integrally moulded heat shield (150) made of a third material which, in comparison with the second material, has a lower coefficient of thermal conductivity.

Description

FLANGED HUB OF A WHEEL BEARING UNIT
FIELD OF THE INVENTION
The present invention relates to a flanged hub of a wheel bearing unit having a flange part and a hub part which are made from different materials. More specifically, the hub part comprises a raceway made of bearing steel and the flange part predominantly comprises a second material that is joined to the hub part in a moulding process. BACKGROUND
A flanged hub of the above kind is known from US6485188. Specifically, this document concerns a wheel mounting with a bearing race embedded in a cast component. In one embodiment, the cast component is a bearing outer ring with a flange for receiving a vehicle wheel and brake disc. The flanged ring can be made of aluminium which is cast around an insert made of bearing steel that comprises hardened outer raceways. The resulting flanged hub is lighter than a flanged hub made entirely of bearing steel, which benefits the car owner in terms of fuel economy. One drawback of using aluminium instead of bearing steel is that aluminium has a higher thermal conductivity. This can be disadvantageous when an excessive amount of heat is generated due to friction between e.g. brake pads and a brake disc. Since part of the brake disc is mounted against the aluminium flange, heat is transferred through conduction from the brake disc to the bearing steel insert via the flange. The aluminium flange allows more heat to be conducted than a bearing steel flange. Thus, under severe and prolonged braking conditions, there is a greater risk that an amount of heat will be transferred to the raceways that causes a temperature increase which can adversely affect raceway hardness. Consequently, there is room for improvement. DISCLOSURE OF THE INVENTION
The present invention resides in a flanged hub of a wheel bearing unit comprising a hub part and a flange part, the hub part having a raceway made of a first material, being a bearing steel material, and the flange part having a mounting surface for the attachment of a brake rotor and vehicle wheel rim. The flange part predominantly comprises a second material that is joined to the hub part in a moulding process. According to the invention, the flange part further comprises an integrally moulded heat shield made of a third material which, in comparison with the second material, has a lower coefficient of thermal conductivity.
Thus, a flanged hub according to the invention inhibits heat transfer from the brake rotor to the raceway via the flange part, meaning that the raceway is protected from reaching a temperature that could reduce the hardness of the bearing steel.
In a further development of the invention, the third material of the heat shield has a higher modulus of elasticity in axial direction than the second material. As a result, flange stiffness is enhanced because the heat shield is integrally moulded in the flange part. The overmoulded flange is therefore capable of withstanding higher axial bending loads than a flange of the same thickness that is made entirely from the second material. Consequently, it is also possible to reduce the thickness of the overmoulded flange while retaining a required level of strength and stiffness.
The heat shield is positioned at an outboard side of the flange part, such that the mounting surface is at least partly defined by an outer surface of the heat shield. Thereby, the area of surface contact between the brake rotor and the second material of the flange part is reduced, which in turn reduces the amount of heat transfer. In a further development, the outboard surface of the heat shield has a surface profile, to reduce the area of contact between the brake rotor and the mounting surface and thereby reduce heat transfer. For example, the outboard surface can be grooved, or a have certain surface roughness. Advantageously, any parts of the mounting surface which are formed by the second material can also be grooved or roughened.
The second material of the flange part which is moulded to the hub part preferably comprises a lightweight metal such as aluminium, magnesium, or alloys thereof. Moulding should be understood as a process in which the second material is joined to the hub part in a moulten state or a semi-moulten state. In a particularly preferred embodiment, the second material is aluminium and is joined to the hub part in a semi-solid metal process, being one of a rheocasting process, a rheoforming process, a rheomoulding process, a thixocasting process, a thixoforming process or a thixomoulding process. In a conventional molten metal process such as casting, the microstructure of the cast metal or metal alloy contains interlocking dendrites that result in material brittleness. The advantage of a semi-solid process is that spherical grains are formed, and the metal has fine, uniform microstructures which give enhanced mechanical properties. Semi-solid metal processing is also less susceptible to air entrapment and a component produced in this way has fewer defects and lower porosity than e.g. a cast component. The second material may also be a fibre composite material comprising a polymer matrix and e.g. carbon fibres. In such examples of a flanged hub according to the invention, the second material will additionally insulate the raceway of bearing steel against potentially harmful temperature rises. A heat shield remains advantageous, however, as it will protect the polymer matrix from temperature rises that could cause melting. Also, as mentioned above, by using a heat shield material with a higher elastic modulus in axial direction, flange stiffness can be enhanced.
Suitable materials for the heat shield include mild steel, stainless steel and ceramics, which are stiff materials and are poorer thermal conductors than most lightweight metals. Stainless steel and ceramic materials have the additional advantage of being corrosion-resistant and will therefore prevent corrosion between e.g. a steel brake disc and an aluminium flange. When the heat shield is made of mild steel, its outboard surface may be treated with a chemically passive coating. Alternatively, the outboard surface may be given a sacrificial coating of e.g. ZnAI15, which will preferentially corrode and thereby protect the brake disc mounting surface from corrosion.
In some embodiments, the heat shield consists of a disc with a circular outer periphery. Alternatively, the heat shield can be shaped such that its outer periphery follows the geometry of the outboard face of the flange. In other embodiments, the heat shield comprises a plurality of separate, thermally insulating elements that are arranged around the outboard side face of the flange.
In a further development, the heat shield comprises one or more axial extensions. This increases the second moment of area of the heat shield in axial direction, thereby enhancing flange stiffness. Furthermore, the one or more axial extensions provide additional surface area against which the overmoulded second material can contract as it cools, thereby improving radial locking. The disc part may also comprise openings into which the overmoulded second material flows. This provides additional radial locking and also rotationally locks the heat shield with the flange.
In a still further development of the invention, the axial extensions are formed by threaded inserts for receiving mounting bolts or stud bolts. One advantage of this further development is that heat transfer via the brake rotor mounting bolts is inhibited, providing the flanged hub with even better thermal protection.
As demonstrated, a flanged hub according to the invention has several advantages. Other benefits will be come clear from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a cross-section of an example of a wheel bearing unit comprising a first embodiment of a flanged hub according to the invention;
Fig. 2a shows a partial cross-section of a further example of a wheel bearing unit comprising a second embodiment of a flanged hub according to the invention;
Fig. 2b is a perspective view of a heat shield used in the flanged hub of Fig.
2a.
Fig. 3a and 3b show a partial cross-section of further embodiments of a flanged hub according to the invention.
DETAILED DESCRIPTION
An example of a wheel bearing unit 100 comprising a flanged hub 120 according to the invention is shown in Figure 1. The flanged hub 120 in this example is adapted for inner ring rotation and comprises a hub part 122 made of bearing steel. The hub part 122 has a radially outer surface that serves as an inner raceway 125 for an outboard row of rolling elements and further comprises a seat for a separate inner ring that forms the raceway for an in board row of rolling elements. To reduce the weight of the flanged hub 120 in comparison with conventional hubs that are made entirely from bearing steel, a flange part 127 of the flanged hub is made from aluminium. The aluminium of the flange part has been joined around the hub part 122 in a rheocasting process. The flange part 127, generally known as the wheel mounting flange, has a mounting surface 130 to which a mounting part 142 of a brake rotor 140 and a wheel rim (not shown) are bolted. A brake disc is shown in this example, but the brake rotor could also be a drum brake. Heat that is generated during braking is therefore transferred to the wheel mounting flange 127 through the mounting surface 130. The generated heat is then conduced through the flange 127 to the hub 122 made of bearing steel. Aluminium has a higher coefficient of thermal conductivity than bearing steel, meaning that a faster rate of heat transfer occurs through the aluminium. Therefore, when an excessive amount of heat is generated in the brake rotor 140, e.g. due to prolonged braking when driving down a long and steep slope, the heat that is lost through conduction and through dissipation to the surroundings may not be sufficient to prevent a harmful rise in temperature at the inboard raceway 125. For example, if the inboard raceway experienced a temperature of e.g. 140 °C for 15 seconds, raceway hardness would be lost, dramatically reducing the service life of the bearing unit 100.
To prevent such an occurrence, the flange 127 of a flanged hub 120 according to the invention comprises an integrally moulded heat shield 150. In the depicted example, the heat shield is made of stainless steel, which has a coefficient of thermal conductivity k of 16 W/mK. Aluminium has a k-value of around 250 W/mK; bearing steel has k-value of around 30 - 45 W/mK [the given values are for a reference temperature of 25 °C]. The heat shield 150 in this example is a stainless steel disc, which is positioned within the flange 127 such that the mounting surface 130 is formed by an outboard surface of the heat shield. Consequently, heat transfer from the brake disc mounting part 142 to the aluminium of the flange 127 is slowed down and a damaging increase of temperature at the raceway 125 becomes practically impossible. A further advantage of a stainless steel mounting surface 130 is that corrosion between the flange and the mounting part 142 of the brake rotor is prevented.
A still further advantage of integrating a heat shield of stainless steel is improved flange stiffness. Stainless steel and aluminium respectively have a modulus of elasticity of 200 and 70 GPa. Consequently, the flange 127 of the flanged hub 120 according to the invention has higher axial bending strength and stiffness than a flange of the same thickness that is entirely made from aluminium.
Depending on the application requirements, the heat shield 150 can be designed with a second moment of area in axial direction that optimises flange stiffness. For example, the heat shield may have a minimum thickness in axial direction. Alternatively, the second moment of area of the heat shield can be increased, without increasing the weight of the shield, by effectively making the shield longer in axial direction. In other words, the heat shield may comprise a disc portion, which at least partly serves as the mounting surface, and further comprise one or more axial extensions. In a further development of the invention, the axial extensions are formed by threaded inserts. An example of a wheel bearing unit comprising a flanged hub according to the further development is shown in Fig. 2a, while Fig. 2b is a perspective view of the heat shield that is integrally moulded in the flange. In this example, the bearing unit 200 is adapted for outer ring rotation and the hub part 222 of the flanged hub 220 comprises outer raceways for first and second rows of tapered rollers. The hub part 222 is made from bearing steel and the flange 227 in this example is predominantly made of aluminium, which has been joined to the hub part in a rheocasting process. The integrally moulded heat shield 250 is made of mild steel in this example.
The heat shield 250 comprises a disc part 255, against which the brake rotor mounting part 242 is mounted. The heat shield further comprises a plurality of axial extensions 257 having an inner thread 260 for receiving e.g. stud bolts. The stud bolts connect the brake rotor mounting part 242 to the flange 227, and consequently form an additional path for heat conduction from the brake rotor 240 to the overmoulded material of the flange. The internally threaded axial extensions 257 of the heat shield 250 therefore retard heat transfer, providing the flanged hub with additional thermal protection. A further advantage of incorporating internally threaded extensions in the heat shield is that the necessary flange mounting holes can be accurately positioned and toleranced.
In addition to enhancing stiffness, the axial extensions 257 of the heat shield rotationally lock the heat shield 250 within the flange 227 and provide additional surface area against which the overmoulded flange material can contract as it cools. Contraction takes place in a radially inward direction, meaning that radially outer surfaces of the heat shield effectively serve as attachment interfaces. In the example of Fig. 1 , the flange 127 has a larger outer circumference than the heat shield 150. Consequently, a portion of the overmoulded aluminium is able to contract against the outer circumferential surface of the shield 150. Needless to say, increasing the surface area against which the cooling aluminium can contract leads to better retention of the heat shield within the flange.
In the example of Figure 2b, the disc part 255 of the heat shield comprises a plurality of openings 256. During the rheocasting process, the semi-solid aluminium also flows into these openings and provides additional retention. A further example of a heat shield which comprises such openings is shown in Fig. 3a, which depicts part of a further embodiment of a flanged hub 320a according to the invention. The heat shield 350a is a disc with openings 356. Consequently, the outer circumference of the shield forms a first attachment interface 365 and the radially outer surface 367 of the heat shield at the openings 356 form a second attachment interface.
A still further embodiment of a flanged hub according to the invention is shown, in part, in Fig. 3b. The flanged hub 320b comprises a still further example of a heat shield 350. In this example, the heat shield is formed by a disc, whereby an outer periphery of the disc has been bent over, thereby creating an axial extension in the form of a lip 357. The lip 357 not only provides an attachment interface of increased surface area, but also increases the second moment of area of the heat shield 350b. A number of aspects/embodiments of the invention have been described. It is to be understood that each aspect/embodiment may be combined with any other aspect/embodiment. The invention may thus be varied within the scope of the accompanying patent claims. Reference numerals
100 wheel bearing unit
120 flanged hub
122 hub part of flanged hub
125 inner raceway on hub part
127 flange part of flanged hub
130 mounting surface of flange part
140 brake rotor
142 mounting part of brake rotor
150 heat shield
200 wheel bearing unit
220 flanged hub
222 hub part of flanged hub
227 flange part of flanged hub
240 brake rotor
242 mounting part of brake rotor
250 heat shield
255 disc part of heat shield
256 openings in disc part
257 axial extensions (threaded inserts)
260 inner thread
320a, 320b flanged hub
350a, 350b heat shield
356 openings in heat shield
357 axial extension of heat shield (lip) 365, 367 first and second attachment interface

Claims

Flanged hub (120, 220, 320a, 320b) of a wheel bearing unit (100, 200) comprising a hub part (122, 222) and a flange part (127, 227),
the hub part having a raceway (125) made of a first material, being a bearing steel material, and the flange part having a mounting surface (130) for the attachment of a brake rotor (140, 240), where the flange part is predominantly made of a second material that is joined to the hub part in a moulding process,
characterized in that
the flange part (127, 227) comprises an integrally moulded heat shield (150, 250, 350a, 350b) made of a third material which, in comparison with the second material, has a lower coefficient of thermal conductivity, whereby the mounting surface (130) is at least partly defined by an outboard surface of the heat shield.
Flanged hub according to claim 1 , wherein the third material has a higher modulus of elasticity in axial direction than the second material.
Flanged hub according to claim 1 or 2, wherein the outboard surface of heat shield is profiled for reducing surface area contact with a mounting part (142, 242) of the brake rotor.
Flanged hub according to any preceding claim, wherein the outboard surface of the heat shield is provided with a chemically passive coating or a chemically sacrificial coating.
Flanged hub according to any preceding claim, wherein the heat shield (250) comprises a disc part (255).
Flanged hub according to claim 5, wherein the disc part (255) comprises openings (256, 356).
7. Flanged hub according to any preceding claim, wherein the heat shield (250, 350a, 350b) comprises one or more axial extensions (257, 357).
8. Flanged hub according to claim 7, wherein the one or more axial extensions (257) are provided with an inner thread (260) for receiving a stud bolt or mounting bolt.
9. Flanged hub according to any preceding claim, wherein the second material is a lightweight metal in comparison with bearing steel.
10. Flanged hub according to claim 9, wherein, the lightweight metal is aluminium or an aluminium alloy that is joined to the hub part in a semi solid metal process. ·
11. Flanged hub according to claim 10, wherein the third material is a ceramic material or a steel material.
12. Flanged hub according to any of claims 1 to 8, wherein the second material is a fibre composite material.
13. Flanged hub according to claim 12, wherein the third material is a ceramic material.
14. Wheel bearing unit comprising a flanged hub according to any of claims 1 to 13.
PCT/EP2010/004188 2010-07-09 2010-07-09 Flanged hub of a wheel bearing unit WO2012003848A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2010/004188 WO2012003848A1 (en) 2010-07-09 2010-07-09 Flanged hub of a wheel bearing unit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2010/004188 WO2012003848A1 (en) 2010-07-09 2010-07-09 Flanged hub of a wheel bearing unit

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITTO20120266A1 (en) * 2012-03-26 2013-09-27 Skf Ab METHOD FOR THE REALIZATION OF A STEEL INSERT FOR AN EXTERNAL RING OF A ROLLING BEARING, IN PARTICULAR OF A WHEEL HUB UNIT
EP2644297A1 (en) 2012-03-26 2013-10-02 Aktiebolaget SKF Equipment for manufacturing by rolling a complex shape annular element, in particular a steel insert for an outer ring of a rolling bearing
ITTO20130841A1 (en) * 2013-10-17 2015-04-18 Skf Ab HUB FOR A WHEEL OF A MOTOR VEHICLE
FR3021719A1 (en) * 2014-05-30 2015-12-04 Ntn Snr Roulements BEARING BEARING HUB
FR3037527A1 (en) * 2015-06-18 2016-12-23 Ntn-Snr Roulements ROLLING BEARING HUB INTEGRATING AN ARMATURE
DE102017212608A1 (en) * 2017-07-21 2019-01-24 Ford Global Technologies, Llc Wheel hub unit with thermal barrier coating to reduce the thermal load of a wheel bearing
EP3612400A4 (en) * 2017-04-20 2020-12-23 Watson & Chalin Manufacturing, Inc. Vehicle suspension with common hub and/or knuckle assembly

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EP0799723A1 (en) * 1996-04-03 1997-10-08 SKF Industrial Trading & Development Company, B.V. Lightweight hub unit
US6485188B1 (en) 2000-04-21 2002-11-26 The Timken Company Wheel mounting with a bearing race embedded in a cast component
JP2008157409A (en) * 2006-12-26 2008-07-10 Nsk Ltd Hub unit bearing with braking member
WO2008147284A1 (en) * 2007-06-01 2008-12-04 Aktiebolaget Skf A bearing component for a rolling bearing or for a sliding bearing
WO2010063299A1 (en) * 2008-12-02 2010-06-10 Ab Skf Bearing unit

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Publication number Priority date Publication date Assignee Title
EP0799723A1 (en) * 1996-04-03 1997-10-08 SKF Industrial Trading & Development Company, B.V. Lightweight hub unit
US6485188B1 (en) 2000-04-21 2002-11-26 The Timken Company Wheel mounting with a bearing race embedded in a cast component
JP2008157409A (en) * 2006-12-26 2008-07-10 Nsk Ltd Hub unit bearing with braking member
WO2008147284A1 (en) * 2007-06-01 2008-12-04 Aktiebolaget Skf A bearing component for a rolling bearing or for a sliding bearing
WO2010063299A1 (en) * 2008-12-02 2010-06-10 Ab Skf Bearing unit

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102036379B1 (en) 2012-03-26 2019-10-24 아크티에볼라게트 에스케이에프 Equipment for manufacturing by rolling a complex shape annular element, in particular a steel insert for an outer ring of a rolling bearing
EP2644297A1 (en) 2012-03-26 2013-10-02 Aktiebolaget SKF Equipment for manufacturing by rolling a complex shape annular element, in particular a steel insert for an outer ring of a rolling bearing
KR20130109059A (en) * 2012-03-26 2013-10-07 아크티에볼라게트 에스케이에프 Equipment for manufacturing by rolling a complex shape annular element, in particular a steel insert for an outer ring of a rolling bearing
ITTO20120266A1 (en) * 2012-03-26 2013-09-27 Skf Ab METHOD FOR THE REALIZATION OF A STEEL INSERT FOR AN EXTERNAL RING OF A ROLLING BEARING, IN PARTICULAR OF A WHEEL HUB UNIT
ITTO20130841A1 (en) * 2013-10-17 2015-04-18 Skf Ab HUB FOR A WHEEL OF A MOTOR VEHICLE
EP3001055A1 (en) 2013-10-17 2016-03-30 Aktiebolaget SKF A hub for a motor vehicle wheel
EP2863082A1 (en) 2013-10-17 2015-04-22 Aktiebolaget SKF A hub for a motor vehicle wheel
FR3021719A1 (en) * 2014-05-30 2015-12-04 Ntn Snr Roulements BEARING BEARING HUB
FR3037527A1 (en) * 2015-06-18 2016-12-23 Ntn-Snr Roulements ROLLING BEARING HUB INTEGRATING AN ARMATURE
EP3612400A4 (en) * 2017-04-20 2020-12-23 Watson & Chalin Manufacturing, Inc. Vehicle suspension with common hub and/or knuckle assembly
US11278343B2 (en) 2017-04-20 2022-03-22 Watson & Chalin Manufacturing, Inc. Vehicle suspension with common hub and/or knuckle assembly
DE102017212608A1 (en) * 2017-07-21 2019-01-24 Ford Global Technologies, Llc Wheel hub unit with thermal barrier coating to reduce the thermal load of a wheel bearing
US11396207B2 (en) 2017-07-21 2022-07-26 Ford Global Technologies, Llc Wheel hub unit with thermally insulating coating for reducing the thermal load on a wheel bearing
DE102017212608B4 (en) 2017-07-21 2023-11-16 Ford Global Technologies, Llc Wheel hub unit with thermal insulation coating to reduce the thermal load on a wheel bearing

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