DE102019135337B4 - ALIMINIUM-CERAMIC COMPOSITE BRAKE ASSEMBLY - Google Patents

Abstract

A brake assembly (2) comprising: a one-piece brake rotor (4) having an axis of rotation (RA1) and comprising a central opening (10) and projections (26) extending radially inward towards the axis (RA1), the projections ( 26) are formed without an internal cavity; a hub (6) disposed within the central opening (10) and including through holes (40) spaced around a circumference of the hub (6); andcovers (8) which are arranged on the projections (26);wherein the projections (26) are arranged in the through holes (40) to thereby connect the rotor (4) to the hub (6);wherein the projections ( 26) can move radially with respect to the through holes (40) without separating the rotor (4) from the hub (6); the covers (8) preventing the projections (26) from touching the hub (6). wherein the covers (8) completely cover tips (32) of the projections (26), and wherein a gap (52) is provided between the covers (8) and the through holes (40) to thereby permit radial movement of the covers (8) and the projections (26) with respect to the through holes (40).

Description

BACKGROUND

Aluminum-ceramic composite brake rotors are known for use in vehicles as part of a disc brake mechanism. Compared to iron-based brake rotors, aluminum-ceramic composite brake rotors are lighter, reducing overall vehicle weight and generating savings in fuel costs. However, these aluminum-ceramic composite rotors cannot be welded to a metal hub and therefore present challenges when attaching the rotor to a metal hub and axle of a vehicle.

Also, these aluminum-ceramic composite brake rotors experience some thermal expansion due to the heat generated from friction during a braking operation. This heat causes the aluminum-ceramic composite rotors to expand and contract at a different rate/rate than the metal hub due to differences in the coefficients of thermal expansion of the two materials. The difference in thermal expansion can also result from the hub not being exposed to the same amount of heat as the rotors during braking events since the hub does not experience friction during braking events. Such a difference in expansion between the aluminum-ceramic composite rotors and the metal hubs must be taken into account when joining the two components, which is another challenge when using aluminum-ceramic composite rotors.

From the DE 10 2007 001 567 A1 a brake assembly is known having a brake rotor with an axis of rotation, comprising a central opening and protrusions extending radially inward toward the axis, and a hub disposed within the central opening and comprising through-holes formed around a periphery of the are spaced apart from the hub, the projections being located in the through-holes to thereby connect the rotor to the hub, and the projections being able to move radially with respect to the through-holes without separating the rotor from the hub.

From the DE 10 2010 026 070 A1 and the FR 3 028 904 A1 a further brake assembly is known in each case, which comprises a brake rotor and a hub, the brake rotor and hub being connected by projections on the brake rotor being arranged in a radially movable manner in through-holes in the hub.

From the DE 10 2009 013 358 A1 a brake assembly is known which comprises a brake rotor and a hub, the brake rotor and hub being connected by projections on the brake rotor being arranged radially movably in blind holes in the hub.

TASK AND SOLUTION

The object of the present invention is to provide a brake assembly with a one-piece brake rotor and a hub, and a method for producing such a brake assembly, which brake assembly enables a reliable connection of the brake rotor to the hub even at elevated temperatures of the brake rotor.

This object is achieved by a brake assembly having the features of claim 1 or claim 15 and a method having the features of claim 8. Advantageous embodiments of the invention are specified in the dependent claims.

character list

• 1 12 is an internal perspective view of a prior art brake rotor.
• 2 Figure 12 is an internal perspective view of a prior art hub.
• 3 14 is an internal perspective view of a brake assembly incorporating the brake rotor of FIG 1 and the hub of 2 according to the state of the art.
• 4 Figure 14 is an interior perspective view of covers according to the present invention.
• 5 12 is an internal perspective view of a brake rotor incorporating the covers of FIG 4 according to that of the present invention.
• 6 14 is an internal perspective view of a brake assembly incorporating the brake rotor of FIG 5 according to the present invention.
• 7 12 is a cross-sectional view of the brake assembly of FIG 3 along line 7-7.
• 8th 12 is a cross-sectional view of the brake assembly of FIG 6 along line 8-8.
• 9 Figure 12 is a cross-sectional view of a prior art brake assembly.
• 10 Figure 12 is a cross-sectional view of a prior art brake assembly.

DETAILED DESCRIPTION

A brake assembly includes a rotor and a hub. The rotor includes a plurality of protrusions that extend into through holes in the hub. These through holes engage the bosses in a manner that prevents removal of the rotor from the hub but allows thermal expansion of the rotor (radially inward) when the rotor is in service and exposed to elevated temperatures.

Referring to the 1-10 a brake assembly 2 comprises a brake rotor 4 (also referred to as "rotor") and a hub 6 and according to the invention further covers 8 ( 4-6 , 8th and 10 ).

The brake assembly 2 may be included in a vehicle as part of a disc brake mechanism, which may further include brake calipers that press a pair of brake pads against the rotor 4 during braking operations to slow or stop the vehicle. The brake assembly 2 can be included in any type of vehicle and attached to a rotating shaft such as a spindle or axle or a wheel of the vehicle to inhibit rotation of the shaft or wheel.

The brake rotor 4 can be a one-piece unit or can be a multi-component assembly. The rotor 4 can be made of any suitable material, such as cast iron, aluminum, magnesium, or alloys or composites, including aluminum ceramic composite (ACC), also known as aluminum metal matrix composite or aluminum -MMC) and the like. In a preferred embodiment, the rotor 4 is formed from an ACC in a sand mold casting process and is a one-piece unit. Illustrative ACCs and methods of forming ACCs that can be used for the rotor 4 are in FIG U.S. Patent No. 7,267,882 is disclosed, the relevant disclosure of which is hereby incorporated by reference as if fully set forth herein. However, alternative known ACCs and methods of manufacturing rotors are contemplated. The rotor 4 can be machined after casting to achieve the desired dimensions.

The rotor 4 includes a central opening 10 sized to receive the hub 6 as shown in FIGS 3 and 6-10 shown. The rotor 4 has an axis of rotation RA1 about which the rotor 4 rotates when the brake assembly 2 is mounted on a rotating vehicle axle or wheel. The central opening 10 is centered on the axis of rotation RA1.

The rotor 4 includes a first friction plate 14, a second friction plate 16 separated from the first friction plate 14 by a gap 18, and veins 20 in the gap 18 connecting the two friction plates 14, 16 in a spaced configuration. The central opening 10 extends through the two friction plates 14, 16. The two plates 14, 16 provide respective braking surfaces 22, 24 which the brake pads engage when compressed by brake calipers during a braking operation to prevent rotation of the rotor 4 to inhibit. During a braking event, the friction between the brake pads and the surfaces 22, 24 causes the rotor 4 to heat up. The gap 18 allows air to circulate between the two plates 14, 16 to dissipate the heat generated, thereby cooling the rotor 4 during and after braking.

The rotor 4 includes projections 26 for engaging the hub 6. The central opening 10 defines a radially inwardly facing surface 28 on the second friction plate 16, and the projections 26 can extend radially inwardly from the surface 28 of the second plate 16 and into Extend direction of the axis RA1. As used herein, "radial" and related terms means deviating in lines from the axis of rotation RA1 (or axes of rotation RA2 and RA3, discussed in more detail herein) in a plane perpendicular to the axis of rotation. Alternatively, the protrusions 26 may extend from the first friction plate 14 instead. The protrusions 26 extend from only one of the two friction plates 14,16. However, this is not required and more or fewer and different protrusions 26 may be used and/or the protrusions 26 may be differently (e.g., randomly) spaced about the radially inward-facing surface 28 .

How best in the 7-10 As shown, the protrusions 26 are spaced axially a distance D from a line L, the line L being perpendicular to the axis RA ₁ and the line L extending radially from the axis RA ₁ through a center of the gap 18 . This configuration of the protrusions 26 with respect to the gap 18 is referred to herein as protrusions 26 lying "outward" of the gap 18, ie indicates that they are located farther from a body of the vehicle associated with the brake assembly 2; while the term "inward" indicates that they are located closer to the body of the vehicle. In this axially spaced arrangement, since the projections 26 are spaced axially outward from line L, the projections 26 do not block air flowing through the gap 18 . This arrangement allows air to flow freely through the gap 18 along the line L without being obstructed by the projections 26 and thus allows air to flow freely between the two friction plates 14,16 to cool the rotor 4. If the projections 26 were instead in line with the line L, for example by being thicker in the axial direction, the projections 26 could impede the flow of air through the gap 18, partially blocking the gap 18 and thus cooling the rotor 4 would hinder.

The projections each include a base 30 at one end in contact with the radially inwardly facing surface 28 of the second friction plate 16, and a tip 32 at the other end and engaging the hub 6. According to the invention, the tips 32 of the projections 26 are through the covers 8 ( 5 , 6 , 8th and 10 ) covered. The covers 8 are arranged on the tips 32 so that after the rotor 6 and the hub 4 are joined together, the tips 32 do not contact the hub 6 to form the brake assembly 2 . In particular, the covers 8 according to the invention completely cover the tips 32 of the projections 26 ( 5 , 6 and 8th ). In an embodiment not belonging to the invention, the covers 8 do not completely cover the tips 32 of the projections 26 ( 10 ).

The covers 8 can be made of an iron-based material such as steel. The aluminum component in the ACC in the protrusions 26 can get hot enough to soften or melt during a braking event. The hub 6 also includes aluminum and thus heated aluminum in the protrusions 26 may begin to adhere to portions of the hub 6 contacted by the protrusions 26 . Heat from the protrusions 26 may also be transferred to the aluminum in the hub 6 and the protrusions 26 may therefore further fuse, bond or otherwise adhere to the hub 6 . The covers 8 made of iron-based material can have a higher softening/melting temperature than the aluminum in the ACC material, whereby such fusing, sticking or adhesion between the hub 6 and the projections 26 can be prevented. The covers 8 may comprise other materials including metals, alloys, ceramics, composites, etc. that have a higher melting/softening point than aluminum.

The covers 8 can be placed over the tips 32 after the rotor 4 has been formed. This method of application can be performed by any process including, for example, pouring, dipping, spraying, electrostatic deposition, thermal spraying, brushing, roll coating, flow coating, etc. The covers 8 can alternatively be supplied as stand alone components in the form of a box (e.g. 4 ) defining, for example, an interior space with one open side 34 and five closed sides, or other shapes having one open side and closed on all others to define an interior space. In an embodiment not belonging to the invention, the covers 8 can have the form of a shell with two open sides ( 10 ). The covers 8 can initially be placed in a mold and a molten ACC material can then be delivered into the mold. The melted ACC material can fill the inside of the covers 8. Subsequent solidification of the ACC material forms the rotor 4 with the caps 8 at the tips 32 of the bosses 26. The caps 8 may include one or more retention features such as; B. Lips 12 located on the outer and/or inner radius of the hub 6 to prevent removal of the covers 8 from the through holes 40.

The hub 6 is arranged in the central opening 10 of the rotor 4 and itself has a central hole 36 through which a vehicle axle, for example, can be inserted. The hub 6 may also include additional holes 38 through which threaded bolts may be inserted to secure the hub 6 to a vehicle. The hub 6 has an axis of rotation RA ₂ about which the hub 6 rotates when the brake assembly 2 is mounted on a rotating vehicle axle or wheel. The central hole 36 is centered on the axis of rotation RA ₂ . When the hub 6 is disposed in the central opening 10 of the rotor 4 and connected to the rotor 4, the axis of rotation RA ₂ may be collinear with the axis of rotation RA ₁ of the rotor 4, both of which are collinear with an axis of rotation RA ₃ of the brake assembly 2. In this regard, the brake assembly 2 includes the axis of rotation RA ₃ about which the brake assembly 2 rotates when the brake assembly 2 is mounted on a rotating vehicle axle or wheel. The axis of rotation RA ₁ and the axis of rotation RA ₂ correspond to the axis of rotation RA ₃ (ie are collinear with this) when the rotor 4 and the Hub 6 are connected to form the brake assembly 2.

The hub 6 can be made of any suitable material, such as cast iron, aluminium, magnesium or alloys or composite materials. In a preferred embodiment, the hub 6 is cast from an aluminum material, such as an aluminum alloy or aluminum metal. The hub 6 can be cast by inserting the rotor 4 into a mold together with a sand core and supplying a molten aluminum material into the mold. The aluminum material is solidified to form the hub 6, which is thereby connected to the rotor 4, as will be described in more detail below.

Hub 6 includes through holes 40 spaced around a circumference of hub 6 which mate with bosses 26 to secure hub 6 and rotor 4 together. The through holes 40 are located in a rim 42 that extends around a circumference of the hub 6 . The through holes 40 are arranged in a spaced configuration on the rim 42 to radially align with the protrusions 26 on the rotor 4 for engagement with the protrusions 26 . The rim 42 includes a radially inward side 44 and a radially outward side 46, and the through holes 40 extend completely through the rim 42 from the radially inward side 44 to the radially outward side 46. One direction each of the through holes 40 is the direction in which each extends through the rim 42 between the radially inward side 44 and the radially outward side 46, rather than the through holes 40 extending in an axial direction. The direction of each of the through holes 40 may be perpendicular to the radially inward side 44 and the radially outward side 46, and may be radial to the rotation axis RA2 in a plane perpendicular to the rotation axis RA2.

An inner edge 48 of rim 42 may be continuous, ie, flat ( 2 ), or can indentations 50 ( 6 ) spaced around the edge 48 and located circumferentially between the through holes 40 . The indentations 50 may allow for increased airflow through the gap 18 compared to that provided by a rim 42 with a flat edge 48 .

When the hub 6 and the rotor 4 are connected, e.g. B. by casting the hub 4 to be located in the central opening 10 of the rotor 4, the protrusions 26 on the rotor 4 are at least partially located in the through holes 40 to connect the rotor 4 to the hub 6. The protrusions 26 extend through the through holes 40 from the radially outer side of the through holes 40 toward the rotation axis RA3.

The protrusions 26 (with or without covers 8) and through-holes 40 may or may not be tightly abutted, and the protrusions 26 may move radially with respect to the through-holes 40 without separating the rotor 4 from the hub 6. In other words, the mating of the protrusions 26 and the through-holes 40 need not result from a tight connection between the protrusions 26 and the through-holes 40 . Instead, the connection between the protrusions 26 and the through-holes 40 may allow some radial movement of the protrusions 26 relative to the through-holes 40 . The cross-sectional sizes of the projections 26 (or the covers 8, if included) may be slightly smaller than that of the through-holes 40 to provide a gap 52 between the projections 26 (or the covers 8, if included), e.g. as in 7-8 shown; or there may be a close fit with no clearance between the projections 26 (or the covers 8 if included), e.g. B. as in the 9-10 shown. When the covers 8 are included, the cross-sectional sizes of the covers 8 may be smaller than that of the through holes 40 to provide the clearance 52 between the covers 8 and the through holes 40 ( 8th ). It will be appreciated that the projections 26 (or the covers 8, if included) may also fit snugly within the through holes 40 as shown in FIGS 9-10 shown. These arrangements, which may or may not include gaps 52, may result in non-firm contact between the projections 26 (or the covers 8, if included) and the through-holes 40. Such non-firm contact between the projections 26 (or the covers 8, if present) and the through-holes 40 may allow movement of the projections 26 radially with respect to the through-holes 40. Such movement of the projections 26 relative to the through holes 40 may be caused by thermal expansion of the rotor 4 and the projections 26 due to heat generated during a braking operation. Alternatively, if the covers 8 are included with two open ends as in 10 As shown, the projections 26 can move radially with respect to the covers 8, which may be fixed by lips 12 relative to the through holes 40.

The exemplary brake assembly 2 is highly mechanical in practical applications and thermal stresses, with thermal stresses generally increasing in proportion to temperature. Since the rotor 4 is subjected to direct frictional heat during a braking operation, and the thermal expansion coefficients of the aluminum hub 6 and the ACC rotor 4 are significantly different, the rotor 4 can expand faster than the hub 6. Therefore, the loose connection and the gap 52 between the Projections 26 and the through holes 40 thermal expansion of the rotor 4 when heated. Therefore, the thermal stresses of the rotor 4 can be reduced compared to known constructions when the temperature is increased or decreased.

The protrusions 26 may extend partially through the through holes 40 such that the tips 32 of the protrusions 26 do not extend radially inward of the radially inward side of the rim 42; or the protrusions 26 may extend completely through the rim 42 such that the tips 32 of the protrusions 26 extend radially inward of the radially inward side of the rim 42 . During heating and subsequent cooling, protrusions 26 may expand and contract in a radial direction such that tips 32 are between these two positions. The hub 6 is dimensioned in relation to the rotor 4 in such a way that the projections 26 cannot contract due to the cooling in such a way that all the projections 26 are completely removed from the through holes 40 . That is, the tips 32 of the protrusions 26 are always disposed radially inward of the radially outward facing side 46 of the rim 42 . In this way, each of the projections 26 can be prevented from being removed from the corresponding through hole 40 due to the connections formed between the other projections 26 and their corresponding through holes 40 . Additionally, when the covers 8 are included on the bosses 26, the covers 8 may have a retention feature (e.g., lips 12) that prevents their removal from the through-holes 40.

The brake assembly 2 may include bores 54 formed between the bosses 26 and the rim 42 as shown. These bores 54 may extend axially through the brake assembly 2 and allow air to flow therethrough or help air flow through the gap 18 to cool the brake assembly 2 including the rotor 4 .

A method of manufacturing a brake assembly 2 includes providing the rotor 4 from aluminum-ceramic composite material, which may be formed by casting an ACC material. The rotor 4 is placed in a mold together with a sand core. Molten aluminum or an aluminum alloy can be introduced into the mold and solidified to form the hub 6 which is located within the central opening 10 of the rotor 4 and includes the through holes 40 . The projections 26 are arranged in the through holes 40 to thereby connect the rotor 4 to the hub 6 .

The method according to the invention comprises placing covers 8 (e.g. iron-based covers) on the protrusions 26, which covers 8 prevent the protrusions 26 from touching the hub 6.

It is understood that various of the features and functions disclosed above and others, or alternatives or variants thereof, can preferably be combined into many other different systems or applications, as long as the combinations are encompassed by the scope of protection given in the claims. Also, various presently unforeseen or unexpected alternatives, modifications, variations, or improvements thereto may be made hereinafter by those skilled in the art, so long as they come within the scope of protection set forth in the claims.

Claims (17)

Brake assembly (2) comprising: a one-piece brake rotor (4) having an axis of rotation (RA ₁ ) and comprising a central opening (10) and projections (26) extending radially inwardly towards the axis (RA ₁ ), the projections (26) are formed without an internal cavity; a hub (6) disposed within the central opening (10) and including through holes (40) spaced around a circumference of the hub (6); and covers (8) placed on the projections (26); the projections (26) being located in the through holes (40) to thereby connect the rotor (4) to the hub (6); the projections (26) being able to move radially with respect to the through holes (40) without separating the rotor (4) from the hub (6); the covers (8) preventing the projections (26) from touching the hub (6), the covers (8) completely covering tips (32) of the projections (26), and between the covers (8) and the through holes (40) a gap (52) is provided to thereby radial movement of the To allow covers (8) and the projections (26) with respect to the through holes (40). brake assembly (2). claim 1 wherein: the rotor (4) includes a radially inwardly facing surface (28) from which the projections (26) extend radially inwardly towards the axis (RA ₁ ); and a direction of each of the through holes (40) is radial to the axis (RA ₁ ). brake assembly (2). claim 1 wherein the projections (26) extend completely through the through holes (40). brake assembly (2). claim 1 wherein: the rotor (4) comprises two friction plates (14, 16) separated by a gap (18) and connected by wires (20) arranged in the gap (18); and the projections (26) extend from only one of the two friction plates (14,16) and are axially spaced from the gap (18). brake assembly (2). claim 1 wherein: the hub (6) includes a rim (42) in which the through holes (40) are located; and the projections (26) extend through the rim (42). brake assembly (2). claim 5 wherein: the rim (42) has a radially inward side and a radially outward side; and the projections (26) extend through the rim (42) from the radially outward side to the radially inward side. brake assembly (2). claim 1 wherein: the rotor (4) comprises an aluminum-ceramic composite; the hub (6) comprises aluminum; and the covers (8) are iron-based covers (8). A method of manufacturing a brake assembly (2) comprising: providing a one-piece aluminum-ceramic composite rotor (4) having an axis of rotation (RA ₁ ) and comprising a central opening (10) and extending radially inwardly towards the axis (RA ₁ ) extending projections (26), said projections (26) being formed without an internal cavity; placing covers (8) on the projections (26); arranging the rotor (4) in a mould; introducing a molten aluminum alloy into the mold; and solidifying the aluminum alloy to form a hub (6) disposed in the central opening (10) of the rotor (4), the hub (6) having through holes (40) formed around a periphery of the hub (6 ) are spaced; the projections (26) being located in the through holes (40) to thereby connect the rotor (4) to the hub (6); and wherein the projections (26) can move radially with respect to the through holes (40) without separating the rotor (4) from the hub (6); the covers (8) preventing the projections (26) from touching the hub (6); the covers (8) completely covering tips (32) of the projections (26); and wherein a clearance (52) is provided between the covers (8) and the through holes (40) to thereby allow radial movement of the covers (8) and the projections (26) with respect to the through holes (40). procedure after claim 8 , wherein the rotor (4) comprises a radially inwardly facing surface (28) from which the projections (26) extend radially inwardly towards the axis (RA ₁ ). procedure after claim 8 wherein: the rotor (4) comprises two friction plates (14, 16) separated by a gap (18) and connected by wires (20) arranged in the gap (18); and the projections (26) extend from only one of the two friction plates (14,16) and are axially spaced from the gap (18). procedure after claim 8 , wherein the hub (6) has a peripheral edge (42) in which the through holes (40) are arranged. procedure after claim 11 wherein: the rim (42) has a radially inward side and a radially outward side; and the projections (26) extend through the rim (42) from the radially outward side to the radially inward side. procedure after claim 11 wherein: the rim (42) includes indentations (50) in an edge of the rim (42), and the indentations (50) are circumferentially disposed between the through-holes (40). procedure after claim 8 wherein: the covers (8) are iron-based covers (8). A brake assembly (2) comprising: a one-piece brake rotor (4) having an axis of rotation (RA ₁ ) and comprising a central opening (10) and projections (26) extending radially inward toward the axis (RA ₁ ), the projections (26) being formed without an internal cavity; and a hub (6) disposed within said central opening (10) and including through holes (40) spaced around a circumference of said hub (6); the projections (26) being located in the through holes (40) to thereby connect the rotor (4) to the hub (6); and wherein the rotor (4) has a first friction plate (14) and a second friction plate (16) separated from the first friction plate (14) by a gap (18); the projections (26) being spaced axially outward of the gap (18); the covers (8) preventing the projections from touching the hub (6); the covers (8) completely covering tips (32) of the projections (26); and wherein a clearance (52) is provided between the covers (8) and the through holes (40) to thereby allow radial movement of the covers (8) and the projections (26) with respect to the through holes (40). brake assembly (2). claim 15 wherein the projections (26) can move radially with respect to the through holes (40) without separating the rotor (4) from the hub (6). brake assembly (2). claim 15 wherein: the rotor (4) comprises an aluminum-ceramic composite; the hub (6) comprises aluminum; and the covers (8) are iron-based covers (8).

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