Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2000-01-11
2002-10-01
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of metal
C188S21800R, C188S25000B, C192S10700R, C192S10700R, C192S01200R, C192S03000R
Reexamination Certificate
active
06458466
ABSTRACT:
The present invention relates to a brake or clutch component where at least a portion of the component is a ceramic-metal composite.
Generally, in an automotive disk brake, the brake rotor is attached to the car by an axle. As the car travels, the brake rotor rotates with the wheel of the car. The brake caliper assembly contains the brake piston and brake pads and is rigidly mounted to the car frame. Upon application of the brake pedal, hydraulic fluid drives the brake piston or pistons outward from the cylinders in the caliper assembly forcing the brake pads to engage the rotor causing the frictional braking force that stops the car from traveling.
Since the discovery of the toxic effects of asbestos, brakes for light duty vehicles, such as pickup trucks and cars, have been made from cast iron rotors or drums engaged by brake pads or shoes having semi-metallic or non-asbestos organic composite pads. These brakes have suffered from problems such as noise, shudder, vibration and short lifetimes of the pads, rotors and drums. Drums and rotors have also tended to warp due to greater heat generation as a result of the use of semi-metallic brake pads. A consequence of this has been excessive warranty costs to automobile manufacturers, which has been estimated to be about $85 per car in North America.
In addition, since the present pads or shoes wear out quickly, the hydraulic brake piston that forces the pad into contact with the rotor or drum has needed to have a long travel to compensate for the wearing out of the brake pad or shoe (that is, the pad has to be thicker to compensate for the faster wear rate). The long travel necessitates the use of a larger caliper assembly and larger piston, which adds weight to the brake. The excessive wear of today's brake pads also cause aesthetic problems, such as brake pad dust on the wheels.
More recent alternative brakes, such as carbon/carbon composite brakes, have only been used, due to cost and design considerations, on the most exotic applications (for example, race cars and military aircraft).
Therefore, it would be desirable to provide a brake that is lighter, avoids the short lifetime, dusting and repair costs associated with today's light duty vehicle brakes at a cost competitive with current metal brakes.
A first aspect of this invention is a braking component comprised of a metal substrate that has a friction material laminated onto at least a portion of one face of the metal substrate, wherein the friction material is a ceramic-metal composite comprised of a metal phase and a ceramic phase, the ceramic phase being present in an amount of at least 20 percent by volume of the composite. Another aspect of this invention is a brake having at least one braking component of the first aspect of this invention. A third aspect of this invention is a clutch having at least one braking component of the first aspect of this invention.
The braking component of the present invention may be used as a brake component, such as a brake rotor, brake drum, brake shoe and brake pad. The braking component may also be used as a clutch disk or flywheel. Examples of clutches include automotive drivetrain clutches, air conditioner clutches and compressor clutches in refrigerators. The braking components of this invention may be made with lighter metals having lower melting temperatures than metals currently used in brakes. The braking component consequently allows light duty vehicle brakes to be less massive. In addition, the use of the braking components generally provide reduced wear compared to current brakes, consequently, brakes made from these components can be smaller while providing the same lifetimes as current brakes. Similar enhancements result for clutches.
The Braking Component
The braking component may be any component that generates a braking or frictional force when contacted with an opposing component. In particular, the braking component is a component that contacts an opposing component moving relative to the braking component such that the relative motion of the two components is arrested. Examples of the braking component include brake pads, brake shoes, brake rotors, brake drums, clutch disks, flywheels and centrifugal chucks.
The braking component is comprised of a metal substrate having a friction material laminated to at least a portion of one face. In general, the metal substrate supports the friction material and provides the shape of the braking component and points of attachment of the braking component to a greater mechanism, such as a brake, transmission or car. The metal substrate, when attached to a greater mechanism, transfers the frictional force generated by the friction material to the greater mechanism, for example, to stop a car.
The metal substrate may be any known or conventional metal used in the manufacture of brakes, clutches or structural metal components. Examples of metals include ferrous metals (for example, steels and cast iron), aluminum, aluminum alloys, titanium, titanium alloys, magnesium and magnesium alloys. Preferably the metal of the metal substrate is a ferrous metal, aluminum or aluminum alloy. More preferably the metal is aluminum or alloy thereof.
The friction material is laminated to at least a portion of a face of the metal substrate such that, under normal operating conditions, the friction material is the only part of the braking component that contacts an opposing component to provide the frictional force. For example, when the braking component is a brake rotor, the friction material is laminated to the braking face of a metal rotor (that is, metal substrate) where the braking face of the rotor is the area contacted and swept by a brake pad upon braking. The friction material may be laminated to the metal substrate in segments or continuously. That is to say, there may be gaps between the CMC laminated to the metal substrate as long as the friction material is the only part that contacts, under normal operation, an opposing component to generate the frictional force. An illustrative example is a brake rotor that has pads of friction material that are uniformly distributed around and laminated on the braking face of the metal brake rotor. Generally, the friction material covers from 10 percent to 100 percent of any particular face.
The frictional material may be any thickness depending on, for example, the particular braking component (for example, truck brake versus car brake), desired lifetime of the component and severity of the environment the braking component may operate in. Generally, the thickness of the braking component is from 0.5 to 20 mm. Preferably, the thickness is from 1 to 10 mm.
The Ceramic-Metal Composite (CMC)
The friction material is a ceramic-metal composite (CMC) that is comprised of a ceramic phase and a metal phase dispersed within each other. Herein, the CMC is understood to contain essentially no resinous binder (for example, phenol-formaldehyde resins), except that which may penetrate open pores of the CMC when it is glued to the metal substrate using an adhesive described under “Preparing the Braking Component.” Otherwise, essentially no resinous binder is an amount corresponding to at most a trace amount in the body of the CMC.
The metal phase of the CMC may be a metal selected from the Periodic Table Groups
2
,
4
-
11
,
13
and
14
and alloys thereof. Said groups conform to the new IUPAC notation, as described on pages 1-10 of the
CRC Handbook of Chemistry and Physics
71
st Ed
., 1990-91. Preferred metals include silicon, magnesium, aluminum, titanium, vanadium, chromium, iron, copper, nickel, cobalt, tantalum, tungsten, molybdenum, zirconium, niobium or mixtures and alloys thereof. More preferred metals are aluminum, silicon, titanium and magnesium or mixtures and alloys thereof. Most preferably the metal is aluminum and alloys of aluminum, such as those that contain one or more of Cu, Mg, Si, Mn, Cr and Zn. Exemplary aluminum alloys include Al—Cu, Al—Mg, Al—Si, Al—Mn—Mg and Al—Cu—Mg—Cr—Zn. Specific examples of aluminum alloys include 6061 al
Jones Bart R.
Prunier, Jr. Arthur R.
Pyzik Aleksander J.
Blackwell-Rudasill Gwendolyn
Dow Global Technologies Inc.
Jones Deborah
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