Coulomb friction damped disc brake rotors

A Coulomb friction damped disc brake rotor, wherein damping is provided Coulomb friction in generally coextensive relation with the braking surfaces of the one or more rotor cheeks. The Coulomb friction damped disc brake rotor has at least one interfacial boundary formed in at least one rotor cheek disposed in generally coextensive relation to the braking surface thereof. The interfacial boundary provides a mechanically distinguishable surface boundary between two surfaces which are in mutual contact such that a state of Coulomb friction exists therebetween.

TECHNICAL FIELD

The present invention relates to disc brake rotors used in automotive applications, and more particularly to Coulomb friction damped disc brake rotors in which the damping is provided by at least one interfacial boundary disposed in substantially coextensive relation with a braking surface of at least one rotor cheek thereof.

BACKGROUND OF THE INVENTION

Motor vehicle disc brake systems utilize a disc brake rotor at each respective wheel, wherein the disc brake rotor typically includes a rotor hat for connecting to an axle hub of a rotatable axle of the motor vehicle, and at least one annular rotor cheek connected to the rotor hat, wherein the at least one rotor cheek has a pair of mutually opposed braking surfaces onto which brake pads are selectively applied when braking is desired. Typically, the rotor cheek configuration may be solid, in which case a single rotor cheek has opposing braking surfaces thereon, or may be vented, in which case a pair of rotor cheeks are mutually separated by a web of ventilation vanes and each rotor cheek provides a respective braking surface so that, in combination, two mutually opposed braking surfaces are provided.

The disc brake system further typically includes a caliper which supports a mutually opposed pair of brake pads, one brake pad disposed overlying a respective rotor cheek braking surface, wherein the caliper, the brake pads, and other associated brake components collectively form a “brake corner”. Normally, the caliper keeps the brake pads separated from the braking surfaces of the one or more rotor cheeks. Braking of the motor vehicle occurs at the brake corner by the caliper pressing the brake pads upon the braking surfaces of the one or more rotor cheeks. Frictional interaction between the one or more rotating rotor cheeks and non-rotating brake pads causes braking of the motor vehicle to transpire, the rate of braking depending upon the pressure of the brake pads against the braking surfaces.

Brake squeal can be undesirably generated at the brake corner when braking occurs. This brake squeal is the result of modal excitations of the disc brake rotor (composed usually of cast iron) by the frictional material of the brake pads. It is known in the prior art that brake squeal can be addressed by reducing modal excitation on the disc brake rotor by the friction material of the brake pads (ie., lowering the frictional coefficient), by modifying the modal excitation response of the brake corner via changing the modal properties of the rotor cheeks (ie., in terms of resonant frequencies, mode shapes, and structural damping through higher carbon content of the one or more rotor cheeks and/or increasing the disc brake rotor mass, or using exotic, expensive materials), and by introducing additional damping for example via a shim disposed at a backing plate of the brake pads.

The aforementioned brake squeal countermeasures are relatively effective for most brake corner designs, but they require a significant amount of testing and analytical resources in order to be effective. And unfortunately, brake corners for performance motor vehicles, or those motor vehicles with high friction lining materials, are resistant to the prior art brake squeal countermeasures, due to the high amount of modal excitation from the friction material of the brake pads.

U.S. Pat. No. 5,855,257 describes a concept directed toward reducing unwanted disc brake noise via a ring damper affixed around the periphery of the disc brake rotor in a manner which permits relative motion and slippage between the ring damper and the disc brake rotor when the disc brake rotor vibrates during braking. In a preferred embodiment, a groove formed at the periphery of the rotor cheek and the ring damper is disposed in the groove with a pre-loading both radially and transversely.

While the concept described in U.S. Pat. No. 5,855,257 is noteworthy in that an attempt is made to apply Coulomb friction damping to reduce brake squeal, it falls short of this goal. The reason for this is the requirement that the ring damper must be peripherally disposed on the disc brake rotor. Unfortunately, the modal excitations induced during braking at the brake corner arise at the contact between the brake pads and the braking surfaces of the one of more rotor cheeks. Therefore, reliance on radial loading that the peripheral placement of the damping ring of U.S. Pat. No. 5,855,257 cannot achieve adequate brake squeal damping in the region of the disc brake rotor coextensively with the braking surfaces of the rotor cheek.

Accordingly, what remains needed in the art is to somehow provide damping disposed in generally coextensive relation to the braking surfaces of the one or more rotor cheeks.

SUMMARY OF THE INVENTION

The present invention is a Coulomb friction damped disc brake rotor, wherein damping of the modal excitations is provided generally coextensively with the braking surfaces of the one or more rotor cheeks.

The Coulomb friction damped disc brake rotor according to the present invention has at least one interfacial boundary formed in at least one rotor cheek which is disposed in generally coextensive relation to the braking surface thereof. In this regard, by “interfacial boundary” is meant a mechanically distinguishable surface boundary between two surfaces which are in mutual contact such that a state of Coulomb friction exists therebetween, and wherein the term “Coulomb friction” represents the energy absorption processes at the interface between two material surfaces through mechanical interaction of the surfaces, as for example temperature, pressure, time, etc.

In a preferred embodiment of the Coulomb friction damped disc brake rotor according to the present invention, an insert is disposed in at least one rotor cheek of a disc brake rotor having either a solid or vented rotor cheek configuration, wherein the insert provides mutually opposed interfacial boundaries with respect to the surrounding rotor cheek, and wherein the insert is annularly configured and disposed generally coextensively with a braking surface of the rotor cheek. Alternatively, a plurality of inserts may be provided in the one or more rotor cheeks. Alternatively further, the interfacial boundary may be provided by an interstice formed in the rotor cheek in which the surfaces of rotor cheek which define the interstice mutually form therebetween the interfacial boundary, wherein any number of interstices may be provided in one or more rotor cheeks.

In a method of manufacture of the Coulomb friction damped disc brake rotor according to the present invention, the subject rotor cheek may be machined or molded with one or more interstices so as to provide an interfacial boundary at each, or is machined or molded to provide one or more annular slots into each of which an insert is respectively cast, inserted, wound into or otherwise located therein so as to provide a pair of interfacial boundaries at each insert. In another method of manufacture according to the present invention, the subject rotor cheek is molded around one or more pre-manufactured inserts.

It is further believed that a Coulomb friction damped disc brake rotor according to the present invention has the following attributes: 1) the greater the surface area of the interfacial boundaries, the greater will be the damping; 2) the greater the number of interfacial boundaries, the greater will be the damping; 3) pre-tensioning and/or pre-loading is not required so long as the interfacial boundary provides Coulomb friction damping; and finally, 4) the thickness of the insert may be optimized based upon experimentation (ie., a smallest possible thickness while still providing at least one interfacial boundary), and it is thought to be optimal if the thickness of the insert is small relative to the thickness of the rotor cheek

While the noise damping benefits of the invention have been developed for brake rotor applications, it is apparent that the invention may be utilized in other articles having body portions that are subject to mechanical vibrations and body surfaces that radiate noise. It is apparent that the inclusion of one or more interstices or inserts can be used within body portions of such articles and near noise making surfaces to provide a damped article.

Accordingly, it is an object of the present invention to provide a Coulomb friction damped disc brake rotor, wherein damping is provided generally coextensively with the braking surfaces of the one or more rotor cheeks. An alternative embodiment of the invention provides a damped article having a noise producing surface on a body portion wherein sound damping is provided within the body using an interstice(s) and/or an insert(s) within the body to provide friction engaging surfaces for reducing noise.

This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the Drawing,FIGS. 1 through 7depict various aspects of an example of a Coulomb friction damped disc brake rotor100for motor vehicle disc brake applications according to the present invention,FIGS. 8 through 12depict various alternative configurations of a Coulomb friction damped disc brake rotor according to the present invention, andFIGS. 13A through 15Mdepict various examples of manufacturing methods for a Coulomb friction damped disc brake rotor according to the present invention.

Turning attention firstly toFIGS. 1 through 3, the Coulomb friction damped disc brake rotor100has, by way of non-limiting example, a rotor hat102(which need not be present for purposes of the present invention), a rotor cheek104of solid rotor cheek configuration, and an insert106disposed within the rotor cheek, wherein the insert is generally coextensive with the braking surfaces108of the rotor cheek. In this regard, the insert106radially extends, from a radially inward edge106ieto a radially outward edge106oe, a distance R which is generally coextensive with the radial extent of the radially inward edge108ieand the radially outward edge108oeof the braking surfaces108of the rotor cheek104, and further annularly extends around the rotor cheek. The insert106provides a pair of oppositely disposed interfacial boundaries110between the insert and the rotor cheek104, wherein the interfacial boundaries each have a mechanically distinguishable surface boundary between two surfaces which are in mutual contact such that a state of Coulomb friction exists therebetween.

FIG. 4depicts a manufacturing methodology for the Coulomb friction damped disc brake rotor100ofFIGS. 1 through 3, in which an annular slot112is machined radially into the rotor cheek104so as to be generally coextensive with the braking surfaces, and wedge shaped insert components106a,106b,106cand106d(there could be alternatively two semi-circular insert components) are pressed into the slot to thereby collectively form the insert106shown atFIGS. 1 through 3.

FIGS. 5 through 6show comparative brake corner noise data obtained utilizing a brake noise dynamometer of the Coulomb friction damped disc brake rotor100and a conventional disc brake rotor without damping, referred to hereafter as a “baseline” disc brake rotor. The resulting test plots were generated by utilizing using identical test procedures, dynamometers and brake corners for each of the Coulomb friction damped disc brake rotor100and the baseline disc brake rotor. The noise plot N depicted inFIG. 5is that of the Coulomb friction damped disc brake rotor100and has a magnitude too small to be detected, indicating the brake corner is quiet. In contradistinction, noise plot N′ of the baseline brake disc rotor depicted inFIG. 6shows a high magnitude of noise both in the warm section (diamond symbols) and the cold section (square symbols) thereof. The difference between the noise plots N, N′ was due to the high level of damping occurring only at the Coulomb friction damped disc brake rotor100according to the present invention.

FIG. 7shows frequency response function (FRF) test plots comparatively of the FRF plot F for the Coulomb friction damped disc brake rotor100and of the FRF plot F′ of the baseline disc brake rotor. It will be seen that the Coulomb friction damped disc brake rotor100had a greater than one order of magnitude increase in damping (disc brake rotor loss factor) as compared to that of the baseline disc brake rotor. In this regard, the 6th nodal diametrical mode ND6for the Coulomb friction damped disc brake rotor has a loss factor greater than 0.037, whereas ND6for the baseline disc brake rotor has a loss factor of 0.0012; and the 7th nodal diametrical mode ND7for the Coulomb friction damped disc brake rotor has a loss factor greater than 0.046, whereas ND7for the baseline disc brake rotor has a loss factor of 0.0010. Again, this result is attributed to the damping occurring only in the Coulomb friction damped disc brake rotor100according to the present invention.

Turning attention now toFIGS. 8 through 12, various alternative embodiments of the Coulomb friction damped disc brake rotor according to the present invention will be discussed.

FIG. 8depicts an alternative embodiment of a Coulomb friction damped disc brake rotor100aaccording to the present invention in which the insert106ais generally coextensive with the braking surfaces108a, and is completely surrounded by the rotor cheek104a, providing a pair of interfacial boundaries110a. This embodiment of the Coulomb friction damped disc brake rotor is applicable to solid or vented rotor cheek configurations, a solid rotor cheek configuration being shown merely by way of exemplification.

FIG. 9depicts another alternative embodiment of a Coulomb friction damped disc brake rotor100baccording to the present invention in which the insert106ais generally coextensive with the braking surfaces108b, and in which a pair of inserts106bare disposed within the same rotor cheek104b, each providing a pair of interfacial boundaries110b(in this regard, if they touch then they would share an interfacial boundary). It will be understood that while two inserts are shown, any number of inserts may be provided. It will further be understood that an embodiment having a plurality of inserts is applicable to both a solid rotor cheek configuration and to each, or either, rotor cheek of a vented rotor cheek configuration.

FIGS. 10A through 10Cdepict yet another embodiment of a Coulomb friction damped disc brake rotor100caccording to the present invention having a vented rotor cheek configuration composed of a first (hat proximal) rotor cheek104pand a second (hat distal) rotor cheek104d, the rotor cheeks being mutually separated by a web104wof ventilation vanes. An insert106cpis provided in the first rotor cheek104pand an insert106cdis provided in the second rotor cheek104d, both inserts being generally coextensive with the braking surfaces108c, and each providing a pair of interfacial boundaries110c. Optionally, an anchorage106anis provided at the radially inward edge106cie, wherein the anchorage is in the preferable form of a bulbous which interferingly engages the surrounding rotor cheek.

FIGS. 11A and 11Bdepict still another embodiment of a Coulomb friction damped disc brake rotor100daccording to the present invention having a vented rotor cheek configuration in which only the first (hat proximal) rotor cheek104pdhas an insert106dwhich generally coextensively extends with the braking surfaces108d, and providing a pair of interfacial boundaries110d. The second (hat distal) rotor cheek104ddhas no insert.

FIGS. 11C and 11Ddepict an additional embodiment of a Coulomb friction damped disc brake rotor100eaccording to the present invention having a vented rotor cheek configuration in which only the second (hat distal) rotor cheek104dehas an insert106ewhich generally coextensively extends with the braking surfaces108eand provides a pair of interfacial boundaries110e. The first (hat proximal) rotor cheek104pehas no insert. Now, by way merely of example, the second rotor cheek104deis thicker than the first rotor cheek104peso as to accommodate the thickness of the insert106e; however, this increased thickness is an optional feature.

It is to be understood that all the variations of Coulomb friction damped disc brake rotor embodiments exemplified above may be mixed and varied. For example, a single rotor cheek, or both rotor cheeks, of a vented rotor cheek configuration may have a plurality of inserts.

FIG. 12Adepicts yet another embodiment of a Coulomb friction damped brake rotor100faccording to the present invention in which an interfacial boundary110fis provided by an interstice120formed in the rotor cheek104f, wherein the surfaces of rotor cheek which define the interstice mutually form therebetween the interfacial boundary, and whereat therebetween Coulomb friction is present. The interstice is generally coextensive with the braking surfaces108f.FIG. 12Bdepicts a Coulomb friction damped disc brake rotor100f′, wherein a plurality of interstices120a,120beach provide an interfacial boundary110fin the rotor cheek104fthereof, wherein the interstices each are generally coextensive with the braking surfaces108f. It is to be understood that one or more interstices may be provided in one or both rotor cheeks of a vented rotor cheek configuration.

Referring now toFIGS. 13A through 15M, various exemplar methodologies of manufacture of a Coulomb friction damped disc brake rotor according to the present invention will be detailed, wherein it is to be understood that the methodologies presented herein are merely by way of exemplification and not limitation.

InFIGS. 13A through 13C, a disc brake rotor200has a rotor cheek202of solid rotor cheek configuration, having an annular slot204provided therein, as for example by being machined therein or provided at the time of casting. The annular slot204extends radially inward so as to be generally coextensive with the braking surfaces206of the rotor cheek202. As shown atFIG. 13B, a filament208is wound into the slot204so as to form an insert210coextensive with the braking surfaces206, thereby providing a Coulomb friction damped disc brake rotor216, as depicted inFIG. 13C. The Coulomb friction damped disc brake rotor216has interfacial boundaries212with the rotor cheek202so as to have damping therewith, and, advantageously, has additional damping at the interfacial boundaries214at the mutually contacting surfaces of the filament208. The filament208is non-limiting, and includes any highly elongated material capable of being wound into the slot, as for example metallic wire or thread of non-metallic material.

FIGS. 13D through 13Fdepict sequential manufacturing steps as those described inFIGS. 13A through 13C, wherein now a disc brake rotor200′ having vented rotor cheek configuration having two rotor cheeks202a,202bwith braking surfaces206′ is depicted, and wherein now primes denote similar functioning parts as those described above inFIGS. 13A through 13C. In this regard, the Coulomb friction damped disc brake rotor216′ has filaments208a,208bwound, respectively, into each annular slot204′ so as to thereby form inserts210′ which are generally coextensive with the braking surfaces206′. Each of the inserts210′ provide interfacial boundaries212′ in each of the two rotor cheeks202a,202bso as to have damping therewith, and, advantageously, has additional damping at the interfacial boundaries214′ at the mutually between contacting surfaces of each filament208a,208b.

InFIGS. 14A through 14E, a disc brake rotor300has a rotor cheek302of solid rotor cheek configuration, having an annular slot304provided therein, as for example by being machined therein or provided at the time of casting. The annular slot304extends radially inward so as to be generally coextensive with the braking surfaces306of the rotor cheek302. The disc brake rotor300is placed into a mold308a,308b. In a first case of manufacture, shown atFIG. 14B, molten metal310of a preselected composition to maximize damping and ease of casting is molded by being cast or injected into the annular slot304. In a second case of manufacture, shown atFIG. 14C, a high temperature polymer, a metal powder, or a ceramic paste312is molded by being injected into the annular slot304. In this regard if a metal powder is used, the powder is compacted into the annular slot under pressure then placed in an oven and sintered in a controlled atmosphere at elevated temperature so that the powder coalesces into a solid body with a predefined porosity (which can be zero), wherein a tolerance, for example, of 0.3% is expected, and if a suitable coating in the slot is used to lessen gapping at the interface boundary with the rotor cheek, a tolerance, for example, of 0.1% can be expected. In either case of manufacturing methods shown inFIGS. 14A through 14E, a Coulomb friction damped disc brake rotor314is provided, as shown atFIGS. 14D and 14E, wherein the insert316provided thereby in the annular slot is generally coextensive with the braking surfaces306and provides a pair of interfacial boundaries318.

It is to be noted that if the annular slot304is cast into the rotor cheek302, then no machining need be provided, and the disc brake rotor300is placed into the mold308a,308b. In order that the material used for the insert316be subsequently locked into place, the groove may be sprayed with a coating or otherwise have the surface thereof treated (e.g., shot peening or surface roughing), or an aforementioned anchorage (that is, a mechanical interlock) can be pre-cast into the annular slot304. The coating and insert material composition have a synergistic relationship to provide optimum interfacial boundaries between the disc brake rotor and the solidified insert to maximize damping and minimize brake noise. The molding of the insert subsequent to the casting of the disc brake rotor can be achieved by any suitable means including, for example, a permanent mold die, or the disc brake rotor can be used as an insert in a die casting machine.

FIGS. 14F through 14Jdepict sequential manufacturing steps as those described inFIGS. 14A through 14E, wherein now a Coulomb friction damped disc brake rotor314′ having a vented rotor cheek configuration having two rotor cheeks302a,302bis provided, starting with a disc brake rotor300′, wherein now primes denote similar functioning parts as those described above inFIGS. 14A through 14E. In this regard, the Coulomb friction damped disc brake rotor314′ has a molded insert316′ provided atFIGS. 14G and 14H, per any of the manufacturing methodologies described above with respect toFIGS. 14B and 14C, respectively, in each annular slot304′. The inserts316are generally coextensive with the braking surfaces306′ and provide interfacial boundaries318′ in each of the two rotor cheeks302a302bso as to have damping therewith.

InFIGS. 15A through 15F, a disc brake rotor is molded by casting around a pre-manufactured insert400(seeFIG. 15A). The insert400is placed into a mold402(seeFIG. 15B) and becomes part of the mold package (seeFIG. 15C). Molten metal404is then poured into the mold402. The insert400may be, for example, metallic or may be a ceramic that could be reinforced. Once removed from the mold (seeFIGS. 15E and 15F), a Coulomb friction damped disc brake rotor406having a solid rotor cheek configuration is provided, wherein the insert400is generally coextensive with the braking surfaces408of the rotor cheek412and provides a pair of interfacial boundaries410. An advantage of this method of manufacture is that the insert400can be totally encapsulated within the rotor cheek412, as for example depicted atFIG. 8. Further, the insert400may be sprayed with a coating or otherwise have its surface treated (e.g., shot peening or surface roughing) to optimize the seating thereof in the annular slot formed therearound by rotor cheek. More than one insert may be cast over by formation of the disk brake rotor.

FIGS. 15G through 15Mdepict sequential manufacturing steps as those described inFIGS. 15A through 15F, wherein now a vented rotor cheek configuration having two rotor cheeks412a,412b(seeFIGS. 15L and 15M) is provided, wherein now primes denote similar functioning parts as those described above inFIGS. 15A through 15F. In this regard, a pre-manufactured sacrificial web pattern414is provided and is sandwiched in a mold402′ between two pre-manufactured inserts400a,400b. Molten metal404′ is poured into the mold402′, and the sacrificial web pattern serves to provide a vaned ventilation web416of the metal404′. In each rotor cheek412a,412bof the manufactured Coulomb friction damped disc brake rotor406′, the inserts400a,400bare generally coextensive with the braking surfaces408′ and provide interfacial boundaries318′ so as to have damping therewith.

It is to be understood that any of the manufacturing methodologies described hereinabove can be readily adapted to provide multiple inserts in the rotor cheeks.

Further, it is to be noted that any of the manufacturing methodologies described hereinabove can be used for other articles which require noise damping.

To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.