WO2006127877A1 - Brake pad cooling apparatus and method - Google Patents

Abstract

An exemplary embodiment providing one or more improvements includes a brake cooling apparatus and method in which heat is conducted from a brake pad to a heat dissipating portion through a heat receiving poriton and a heat dissipatinog portion dissipates the heat in to a cooling medium.

Description

BRAKE PAD COOLING APPARATUS AND METHOD

RELATED APPLICATIONS 1 The present application claims priority from U.S. Provisional Application Ser. No. 60/683,764, filed on May 24, 2005, U.S. Provisional Application Ser. No. 60/683,735, filed on May 24, 2005 and U.S. Provisional Application Ser, No. 60/711,760, tiled August 29, 2005, all of which are incorporated, herein by reference along with U.S. Patent Application Ser. No. [Attorney Docket Number: DEM-2] . Copies of those applications, except for DEM-2, are attached as appendixes A, B and C BACKGROUND 2 A typical disk brake system of a vehicle includes a caliper with one oi more pistons that hydraulically force brake pads toward one another and into contact with a rotor that spins relative to the caliper when the vehicle is moving. The pads have a high coefficient of friction so that when they are forced into contact with the spinning rotor during braking, the speed at which the rotor is spinning is decreased by the Motional contact between the pad and the rotor. As the rotor speed decreases, the kinetic energy of the rotor is converted into heat Substantial amounts of heat can be generated in the brake pads. Brake pad temperatures can reach well over the melting point of aluminum, greater than about 600 degrees Celsius. Many different techniques or mechanisms are used to remove heat from the disk brake system through the rotor, An example of one mechanism is to provide an integral vent in the rotor through which ambient air moves when the rotor is spinning to cool the rotor. Prior to the present invention, heat was usually primarily removed from the brake pads through contact with the rotor, and through the brake fluid and the brake caliper via the hydraulic pistons. 3 The lack of a good thermal sink for the brake pad can lead to significant problems in some instances. One problem that arises when brake pads get hot is a condition in. which the heat from the pad is conducted through the caliper piston to the brake fluid and causes the fluid to boiL Heat conducted through the caliper piston to the brake fluid can also lead to damaged brake caliper seals or warped caliper pistons. Another problem is a condition in which the brake pads get hot enough that they vaporize on contact with the rotor. Ia this condition, a cushion of gas is produced between the pad and the rotor which prevents the pad from contacting the rotor. Both of the above conditions lead to a decrease in brake efficiency which is also called fade, In extreme cases, the above conditions can τesult in a complete failure of the brake system. 4 Prior attempts have been made to address the problems arising from excessive heat in lie brake pad and several patents have been issued which relate to cooling disk brake systems, However, these patents generally depead on the manufacture of specifically designed custom calipers or rotors that replace or modify the original equipment calipers on ^• the vehicle. Examples of patents which require specially manufactured custom calipers are U.S. Patent 5,002,160 and U.S. Patent 6,446,766. 5 The ' 160 patent discloses a brake caliper that is specially manufactured to have a ventilation channel for ducting ambient air to a position between the m-akc pad backing plate and the piston of the caliper, Someone wishing to utilize

. the disk brake system disclosed in the '160 patent for cooling their brake pads would have to replace their calipers with the calipers disclosed in the '160 patent Since the calipers are the most expensive component of the brake system, replacing the calipers with the specially manufactured calipers of the '160 patent is likely to be an expensive prσposϊtioα 6 The '766 patent discloses a specially constructed brake caliper which includes a duct that is formed inside of the body of the caliper. The duct is designed to direct air to a series of specially constructed hydraulic pistons. The pistons each have a radiator element through which the air from the duct flows to dissipate heat. The '766 patent is an example of a type of device which relies on. a modified caliper and modified hydraulic pistons in an attempt to cool the brake pads. Specially constructing the caliper with air flow ducts adds to the complexity of the caliper and most likely also adds to the cost of manufacturing the caliper as welL In addition to the added cost of the caliper, the device described in the '766 patent also requires the hydraulic pistons to have radiator elements which would also have to be specially manufactured thereby increasing the cost of the device even farther. 7 Other U.S. patents also require modified calipers in attempts to cool the brake pads in a disk brake system. What is needed is an effective disk brake pad cooling system which can be economically utilized without modifying or replacing expensive existing brake system components, 8 The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon reading of the specification and a study of the drawings,

SUMMARY 9 The foEowing embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 10 In general, a brake pad cooling apparatus and method are described for use with a disk brake system for a raoveable vehicle. The disk brake system has a caliper which includes a hydraulic piston for moving a brake pad into forced contact with a rotor. The rotor rotates when the vehicle is moving and forced contact between, me rotor and the biake pad reduces the rate at which the τotor is rotating to slow the movement of the vehicle. The contact also generates heat in the brake pad. "The cooling apparatus comprises a thermally conductive sheet for positioning imo thermal communication with the brake pad. The conductive sheet includes a thermally conductive materia! for conducting heat away from the brake pad. The cooling apparatus also includes a heat sink which is thermally connected to the conductive sheet to allow heat to pass from the conductive sheet to the heat sink. The heat smk is positioned away from the brake pad when the conductive sheet is in thermal contact with the brake pad and the heat sink includes at least two cooling fiα members for dissipating heat into the surrounding air. During operation, the heat sink receives heat from the orake pad through the conductive sheet and dissipates the heat into the surrounding air to cool the brake pad. 11 In another embodiment, a method for cooling a brake pad in. a disk brake system of a moveable vehicle is disclosed. The disk brake system has a caliper which includes a hydraulic piston for moving a brake pad into forced contact with a rotor that rotates when the vehicle is moving. The forced contact between the rotor and the brake pad reduces the rate at which. Ihe rotor is rotating to slow the movement of the vehicle and the contact generates heat in the brake pad. A flieπnally conductive sheet is inserted between the brake pad and the hydraulic piston to receive the heat from the brake pad. A heat sink that includes at least two cooling fin members and which, is attached to the thermally conductive sheet is positioned at a location that is away from the brake pad and is generally surrounded by air. The heat sink receives heat from the btake pad through the conductive sheet and dissipates the heat to the surrounding air with the cooling fin members. 12 In yet another embodiment, a brake pad cooling apparatus and associated method are described for use with a disk brake system for a moveable vehicle. The disk brake system has a caliper which includes a peripheral outline and has a hydraulic piston for moving a brake pad into forced contact with a rotor. The rotor rotates when the vehicle is moving and forced contact between the rotor and the brake pad reduces the rate at which the rotor is rotating to slow the movement of the vehicle. The contact also generates heat in the brake pad. A heat receiving portion of the apparatus is in thermal communication with the brake pad and a distal heat dissipating portion extending out of the peripheral outline of the caliper is in thermal communication with the heat receiving portion. The heat dissipating portion receives heat from the heat receiving portion by thermal conduction and thereafter dissipates the heat into the ambient environment l3 In addition to the exemplary aspects and embodiments described above, fijrther aspects and embodiments will become apparent by reference to me drawings and by study of the following descriptions,

BRTBF DESCRIPTION OF THE DRAWINGS l4 Fig. 1 is a perspective view of disk brake coolers according to the present disclosure installed in a caliper of a disk brake system. l5 Fig.2 is an enlarged perspective view of the disk brake coolers shown in Fig. 1. 16 Fig.3 is a cross section view of the disk brake coolers and caliper taken along a cross sectional line 3-3 shown in Fig. I. 17 Fig.4 is a partial cut away view of the disk brake coolers and caliper shown in Fig. 1. I8 Fig.5 is a partially cut away elevation view of the disk brake coolers and caliper shown in Fig. 1. 19 Fig.6 is a perspective exploded view illustrating components of the disk brake cooler shown in Fig. 1. 20 Fig. 7 is a view of another disk brake cooler according to the present disclosure installed in a caliper of a disk brake system. 21 Fig.8 is a cross section view of the disk brake cooler and caliper shown in Fig, 7.

DETAILED DESCRIPHON 22 Disk brake coolers 20a and 20b, which maybe referred to individually or collectively by the reference number 20, according to (he present invention are shown in Fig. 1 installed in. a disk brake caliper 24, Caliper 24 is mounted to a chassis of a vehicle (not shown) for use as part of a disk brake system 26 that includes a rotαr 28 which rotates as the vehicle moves. Brake pad assftmblies 30 and 32 (Fig. 3) engage rotor 28 to slow or stop the rotation of rotor 28 which then slows or stops the vehicle movement. When, brake pad assemblies 30 and 32 engage and slow or stop the rotation of rotor 28, the rotational or kinetic energy of rotor 28 and the momentum of the vehicle are converted into heat in brake pad assemblies 30 and 32 and in rotor 28. 23 Disk brake coolers 20, one of which is shown in Fig. 2, take advantage of thermal conduction to flow heat from brake pad assemblies 30 and 32 to a position where the heat is more efficiently transferred to the atmosphere. Brake coolers 20 each include a thermally conductive sheet 34 and a heat sink 36. Brake cooler 20a includes thermally conductive sheet 34a and heat sink 36a, and brake cooler 20b includes thermally conductive sheet 34b and heat sink 36b. Sheets 34a and 34b are integrally formed or connected to heat sinks 36a and 36b, respectively, for conducting heat between sheets 34a and 34b and heat sinks 36a and 36b. 24 When brake coolers 20a and 2Oh are installed in caliper 24 (Fig. 1), conductive sheets 34a and 34b are in thermal contact with brake pad assemblies 30 and 32, respectively, and heat is transferred ftom brake pad assemblies 30 and 32 to sheets 34a and 34b, respectively. The heat is conducted from sheet 34a to heat sink 36a, and lroin sheet 34b to heat sink 36b. Heat sinks 36 extend out of caliper 24, as shown in Figs. 1, 3 and 5, where the heat sinks 36 transfer the heat to a cooling medium, such as surrounding air or a fluid in a cooling system, thereby removing the heat from brake assemblies 30 and 32 and decreasing the temperature found in the brake assemblies. 25 Caliper 24, shown in Figs. 1 and 5, is bolted to the vehicle suspension or other components of the vehicle chassis (not shown) through mounting holes 38 and 40. The caliper defines a peripheral outline 42, from which heat sinks 36 shown in Fig. 5 extend when brake coolers 20a and 20b are installed in caliper 24. Heat sinks 36 are positioned at least partially extending ftom the peripheral outline 42 to subject heat sinks 36 to greater air flow for cooling. 26 Details of the operation of disk brake coolers 20a and 20b are discussed below along with details of the operation of disk brake system 26. ϊn many instances brake coolers 20a and 20b can be essentially the same as one another except for rheϊr orientation with respect to one another when installed in the caliper 24. Caliper 24, of disk brake system 26, includes an inner caliper half 44 and an outer caliper half 46 which are connected together using caliper bolts 48 (Figs. 1 and 4). Guide pins 50 and 52 extend between inner and outer caliper halves 44 and 46 for restraining brake pad assemblies 30 and 32 against unwanted movement relative to caliper 24 during application of brake pad assemblies 30 and 32 to rotor 28 and during other times.. Inner caliper half 44 (Fig. 3) houses an inner hydraulic piston 54 which moves within the inner caliper half to force brake pad assembly 30 into contact with rotor 28.. Outer caliper half 46 houses an outer hydraulic piston 56 which moves within outer caliper half 46 to force brake pad assembly 32 into contact With rotor 28. 27 Inner hydraulic piston 54 is positioned in an inner cylinder bore 58 of inner caliper 44, (Fig. 3) for movement toward and away from rotor 28. A hydraulic seal 60 creates a fluid tight seal between the outer surface of piston 54 and the inner surface of cylinder bore 58 which together define an inner fluid reservoir 62. Outer hydraulic piston 56 is positioned in aπ outer cylinder bore 64 of outer caliper 46 for movement toward and away from rotor 28. A hydraulic seal 66 creates a fluid tight seal between the outer surface of piston 56 and the inner surface of outer cylinder bore 64 which together define an outer fluid reservoir 68. An inner dust shield 70 and outer dust shield 72 are positioned to prevent dust and other material from contacting hydraulic seals 60 and 66, respectively. 28 Inner and outer fluid reservoirs 62 and 68 are fluidly connected to one another with a fluid passage (not specifically shown) and the inner fluid reservoir 62 is connected to a hydraulic brake line 73 (Fig. 1) through an orifice 74 (Figs. 3 and 5) in inner caliper 44. Inner and outer fluid reservoir 62 and 68 (Fig. 3), the fluid passage and the hydraulic brake line are filled with a brake fluid (not shown) and excess air is removed through a bleeder screw 76 (Fig. 1). 29 In order to move the brake assemblies into forced contact with rotor 28, brake fluid is moved from brake line 73 into inner fluid reservoir 62 through orifice 74 and to outer fluid reservoir 68 through the fluid passage. Fluid reservoirs 62 and 68 expand to receive the increased amount of brake fluid and pistons 54 and 56 are thereby moved toward rotor 28, which moves the brake assemblies into contact with rotor 28. Movement of brake assemblies 30 and 32 away from rotor 28 is accomplished when hydraulic pressure is released such that brake fluid is release from fluid reservoirs 62 and 68 and fluid reservoirs 62 and 68 are contracted. Release of brake fluid from fluid reservoiτs 62 and 68 causes pistons 54 and 56 to move away from rotor 28 thereby relieving the forced contact between brake assemblies 30 and 32 and rotor 28. Inner and outer dust shields 70 and 72 contribute to the movement of pistons 54 and 56 away from rotor 28. Although the present example is described in conjunction with a caliper having a single piston on either side of the rotar, the disk brake cooler can be used with other calipers having multiple hydraulic pistons on either side, or a single piston on one side. 30 Brake pad assemblies 30 and 32 each include two components, a brake pad 78 and a backing plate 80, as shown in Pig.3. Brake pad assembly 30 includes brake pad 78a and backing plate 80a while brake pad assembly 32 includes brake pad 78b and hacking plate 8Oh. Brake pads 78a and 78b are forced toward one another to contact rotor 28 with hydraulic pistons 54 and 56 (Fig. 3) through backing plates 80a and 80b. Contact between, pads 78 and rotor 28 causes rotor 28 to slow and also causes pads 78 and rotor 28 to heat up. Heat from pads 78a and 78b normally conducts to backing plates 80a and 80b and pistons 54 and 56, respectively, as well as to caliper 24 and to the brake fluid, among other parts. Brake pads 78 are typically made of a combination of several materials that are able to withstand certain temperatures and which also have an abrasive surface to create the friction between pads 78 and rotor 28 when pads 78 axe forced into contact with rotor 28, Brake pads 78 are typically cast or otherwise fastened to backing plates 80, which aie used to connect brake assemblies 30 and 32 to caliper 28. 31 Backing plates 80 include slots or holes 82 and 84 (Figs. 1 and 3) which interact with guide pins 50 and 52 to generally constrain brake pad assemblies 30 and 32 against movement relative to caliper 24 in any direction except toward and away from one another. Other methods are also used for constraining backing plates, such as clips (not shown). When brake pads 78 are pressed against rotor 28, a rotational force of the rotating rotor is applied to brake pad assemblies 30 and 32 from rotor 28. Holes 82 and 84 engage pins 50 and 52 to iesist this rotational force and in. this way the iotational force of rotor 28 is resisted by caliper 24 when brake pads 78 are pressed against rotor 28. Backing plates 80 are constructed of a material which is able to resist the forces at holes 82 and. 84 and pins 50 and 52. Backing plates 80 also have yield properties which resist deformation when hydraulic pistons 54 and 56 are forcing brake pads 78 into contact against rotor 28, 32 Brake coolers 20a and 20b shown in Figs. 1 and 3 are positioned with conductive sheets 34a and 34b of brake coolers 20a and 20b interposed between backing plates 80a and 80b and pistons 54 and 56, respectively. Brake coolers 20a and 20b include guide pin slots or holes 86 (Figs. 2 and 5) which align with guide pins 50 and 52 or otlier mounting hardware of the brake pad assemblies when brake coolers 20a and 20b are installed in caliper 24, Conductive sheets 34 shown in Fig. 2 include a shape that is similar to a shape of backing plates 80. 33 To engage pads 78 against rotor 28 when brake coolers 20a and 20b are installed (Fig. 3), pistons 54 and 56 apply pressure to backing plates 80a and 80b through, conductive sheets 34a and 34b, respectively. Since considerable pressure is applied by pistons 54 and 56, conductive sheets 34 include a high yield strength material such as stainless steel that resists deformation from the applied pressures. When positioned as shown in Figs. 1 and 3, the heat from brake pads 78 is transferred through backing plates 80 to conductive sheets 34. Therefore, the high yield material of conductive sheets 34 is also able to resist deformation at the temperatures of the heat conducted through backing plates 80. 34 Conductive sheets 34 conduct the heat from backing plates 80 to heat sinks 36. In order to maximize the conduction of heat to heat sinks 36, conductive sheets 34 include a high thermal conductivity material such as copper. Conductive sheets 34 of the present example have a thermal conductivity greater than 100 Watts/meter-Kelvin. Other materials can also be used for the conductive sheet, for example copper tungsten has high yield strength and a high thermal conductivity, 35 When one of the conductive sheets is inserted between the backing plate and the piston, 1he overall distance between the piston and brake pad is increased. This makes pads 78 closer to rotor 28 when brake coolers 20a and 20b are installed than when brake coolers 20a and 20b are not installed by an amount generally equal to the thickness of conductive sheet 34. A thicker conductive sheet generally has an ability to conduct more heat than a thinner conductive sheet of the same material. However, if the conductive sheet is too thick, then the brake pad assembly and the conductive sheet of the brake cooler will not fit between the piston and the rotor. The thickness of conductive sheets 34 are chosen to maximize the thermal cross section of the thermal path to heat sink 36 while mmimizing the impact on displacing a set of new brake pad assemblies. Conductive sheets 34 of the present example are 1 millimeter thick. 36 Heat sinks 36 receive heat from brake pad assemblies 30 and 32 through conductive sheets.34, Heat sinks 36 shown in Fig. 1 are positioned remotely away from brake pads 78 and externally to caliper 24 where heat sinks 36 are in contact with surrounding air flow. As is apparent from the configuration and position shown in Fig. 1, heat sinks 36 will not interfere with a wheel (not shown) when the wheel is attached to the vehicle. 37 Heat sinks 36 sho wa in Fig. 1 and 2 include an arrangement of cooling fia members 88 which extend in a row. Cooling fin members 88 provide a large surface area in which to transfer heat from heat sink 36 to the surrounding air. Cooling fin members 88 shown in Fig. 4 extend m a direction that is perpendicular to a plane defined by rotor 28. Typically two or more cooling fin members provide surface area for dissipating heat conducted to heat sinks 36 from conductive sheets 34 when the heat sinks are exposed to air flow in the position shown in Fig. 1 , The cooling fin members can be formed in a variety of different shapes, so long as the shape allows the fin member to dissipate heat. Ia addition, the cooling fin members can be arranged in the heat sink in a variety of different ways so long as the arrangement allows the fin members to dissipate heat. For example, the cooling fin members can be transverse to the plane of the rotor and need not be parallel with respect to one another. 38 In the example shown in Fig. 1, heat sinks 36 are attached to conductive sheets 34 using brazing or mechanical fasteners. Since heat sinks 36 are not subject to the same pressures that conductive sheets 34 are, heat sinks 36 can be constructed of copper. In some instances the size and weight of heat sink 36 is such that high gravity force (G-force) maneuvering of the vehicle will cause stress in the connection between heat sink 36 and conductive sheet 34. One way in which to prevent heat sink 36 from folding or otherwise deforming conductive sheet 34 in these instances is to form heat sink 36 with a shape that prevents a single linear stress point such as a curved shape 90 shown hi Fig.2. 39 Installation of brake coolers 20a and 20b is fairly simple and in most instances will be similar to the installation of brake pad assemblies 30 and 32. Once access to caliper 24 is gained, pistons 54 and 56 are moved into caliper 24 away^' from rotor 28 thereby creating a space between brake pad assemblies 30 and 32 and pistons 54 and 56, respectively. Conductive sheets 34a and 34b are then inserted between brake pad assemblies 30 and 32 and pistons 54 and 56 which leaves heat sinks 36a and 36h at a position away from brake pads 78a and 78b. Conductive sheets 34 can also be inserted between brake pad assemblies 30 and 32 and pistons 54 and 56 by installing brake pad assemblies 30 and 32 after conductive sheets 34 are installed hi caliper 24. 40 In. the previous example, the brake coolers were described as an accessory to a standard brake assembly that includes the backing plate. In another example of the brake coolers, the thermally conductive sheet is utilized as the backing plate. In this instance the brake pad is permanently attached to the theππally conductive sheet and the heat sink

. is connected to the conductive sheet as before. Since the theπnally conductive sheet replaces the backing plate, the thermally conductive sheet can have a larger thickness while still being able to be positioned between the brake pad and the piston. This configuration is also beneficial in that the larger thickness allows for relatively large amounts of thermally conductive material to conduct the heat from the brake pad to the heat sink 41 Another embodiment of the brake cooler is described in conjunction with Fig. 6. In this embodiment, conductive sheet 34 is constructed of a primary sheet 92 and a secondary sheet 94 that are secured to one another. Heat sink 36 is constructed of a theππally conductive material such as copper that is folded into a series of cooling fin members 88. The cooling fin members 88 provide a surface area for transferring heat ftom heat sink 36 to cooling medium. The cooling fin members 88 shown in Fig, 6 have a relatively large surface area for transferring heat to surrounding air. Heat sink 36 in Fig, 6 is connected to the conductive sheet 34 by aligning heat sink 36 with alignment holes 96 and then using a braze material 98 that is heated to adhere to the heat sink 36 and the conductive sheet 34. 42 In the embodiment shown in Fig. 6, the primary sheet 92 is secured to the secondary sheet 94 using rivets 100. The rivets 100 extend through, holes 102 in the secondary sheet 94 and holes 104 in the primary sheet 92 before being expanded to physically secure the sheets 92 and 94 to one another. When the primary and secondary sheets 92 and 94 sie secured to one another, the guide pin holes are formed by cooperative alignment of a primary sheet guide hole 106 and a secondary sheet guide hole 108. 43 The overall conductive sheet 34, described above, is constructed using primary and secondary sheets 92 and 94 which have a complementary shape. In the instance shown in Fig. 6, primary sheet 92 defines a heat pickup hole 110 in which a heat pickup portion 112 of secondary sheet 94 fits. When, heat pickup portion 112 is positioned in heat pickup hole 110, the combination of heat pickup portion 112 and primary sheet 92 surrounding heat pickup hole 110 generally define a planar surface of conductive sheet 34. Secondary sheet 94 also includes a heat sink portion 114 which is sandwiched between primary sheet 92 and heat sink 36. A step 1 16 of secondary sheet 94 transitions between heat pickup portion 112 and heat sink portion 114 of secondary sheet 94. Step 116 allows heat pickup portion 112 to be positioned in heat pickup hole 110 of primary sheet 92 and heat sink portion 114 to be positioned at the surface of the primary sheet 92. 44 In the embodiment shown in Fig. 6, secondary sheet 94 is constructed of a high thermal conductivity material, for example copper. When installed in caliper 24, heat pickup portion 112 of secondary sheet 94 is positioned between the backing plate and the piston. Heat pickup portion 112 leceives heat from the backing plate and conducts the heat to the heat sink portion 114 where the heat is then transferred to heat sink 36. The heat sink shown in Fig. 6 has a large surface area that is in contact with the cooling medium, which in this case is ambient air. Because of the large surface area of the heat sink, heat is transferred from the heat sink to the cooling medium in an efficient manner. Removing heat through the heat pickup portion decreases the amount of heat that reaches the piston, thereby cooling the piston and decreasing or eliminating the occurrence of the piston and the other associated components overheating and boiling the brake fluid. 45 Also in the embodiment shown in Fig. 6, the primary sheet 92 is constructed of a high yield strength material such as stainless steel. When installed, in caliper 24 the primary sheet is positioned between the backing plate and the piston with the primary sheet extending substantially the entire distance across the backing plate and the piston contacting the primary sheet on opposite sides of heat pickup hole 110. Positioned in this way, primary sheet 92 resists deformation from the compressive force applied by the piston during braking and generally prevents the piston from deforming the heat pickup portion 112 of secondary sheet 94. A sheet of high yield strength and high thermal conductivity material, such as copper tungsten, can be substituted for the combination of the primary and secondary sheets. 46 Yet another embodiment of me brake cooler is described in conjunction with Figs. 7 and 8 for use with a single piston caliper 118. Single piston caliper 11 S includes a single piston 120 (Fig. 8) which moves laterally in a cylinder 122 relative to a rotor 124 to move inner and outer brake assemblies 126a and 126b toward and away from the rotor. Each of the brake assemblies shown in Figs, 7 and 8 includes a backing plate 128 and a brake pad 130. A caliper body 132 of the caliper extends around rotor 124 with a caliper cross member 134 and caliper arms 136 engage the outer brake assembly 126b. To engage the rotor with the biake assemblies, piston 120 moves toward the caliper arms 136 which cause the brake assemblies to move toward one another and forcibly engage the rotor. Single piston caliper 118 is connected to a mounting bracket 138 of a vehicle (not shown) using mounting bolts 140 (Fig. 7). 47 Movement of piston 120 is produced by hydraulic fluid passing through an orifice 142 to and ftom a brake line 144. The hydraulic fluid enters a fluid reservoir 146 (Fig. 8) defined by an. interior surface of cylinder 122 and exterior surface of piston 120. A hydraulic seal 150 extends around piston 120 to contain the fluid in fluid reservoir 146 and a dust shield 152 prevents dust and other contaminants from damaging the hydraulic seal. A bleeder screw 154 is included to remove air from the fluid reservoir, 48 The brake cooler 20 in the embodiment slwwn in Figs. 7 and 8 includes two heat sinks 156 and 158 which arc connected in a spaced apart relationship with a thermally conductive sheet 160. Heat sinks 156 and 158 each include fin members 162 for transferring heat to the surrounding atmosphere. Heat sink 156 is positioned on one side σf caliper cross member 134 and heat sink 158 is positioned on another side of caliper cross member 134. 49 Thermally conductive sheet 160 is sandwiched between piston 120 and backing plate I28a of the inner brake pad assembly 126a. Sheet 160 includes a high yield strength material such as stainless steel that resists deformation from the applied pressures, and a high thermal conductivity material (hat conducts heat from the brake pad assembly to heat sinks 156 and 158. A single heat sink may also be used with the single piston caliper, on either the forward or rearwaτd side of caliper cross member 134. Moreover, an additional brake cooler can be installed between brake pad assembly 126b and caliper arms 136 for removing heat from outer brake pad assembly 126b. 5O The brake coolers provide an effective mechanism for removing heat fiom the brake pads without having to modify the caliper or other components of the disk brake system. Since the calipers do not have to be replaced to install the brake coolers, the brake coolers are more economical than omer systems which do require the replacement of calipers or after expensive components. 5l Removal of the heat from the brake pads with the brake coolers lowers the heat level experienced by the hydraulic brake fluid, which can thereby eliminate or substantially reduce the dangerous incidence of the brake fluid boiling. The heat removal may also eliminate or reduce the incidence of heat induced damage to the pistons, seals and other cornponents of the caliper which can also lead to brake failure. The removal of heat from the brake pads by the brake coolers is also beneficial in helping to Teduce or eliminate instances where the pads are heated to the point where they vaporize on contact with the rotor. Removing heat from the brake pad can. result in the temperature of the pad remaining below the point where pad vaporization occurs, thereby substantially or completely eliminating brake pad vaporization. Reducing or eliminating the occurrences of brake fluid boiling and brake pad vaporization increases brake efficiency and may improve the safety of trie vehicle to which the brake coolers are attached.

Broadly, this writing discloses a brake cooling apparatus and method in which heat is conducted from a brake pad to a heat dissipating portion through a heat receiving portion. The heat dissipating portion dissipates the heat into a cooling medium.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope

APPENDIX A

Provisional Patent Application of Joseph R. Demers for TITLE: DISK BRAKE CALIPER PISTON COOLER

CROSS-REFERENCE TO RELATED APPLICATIONS: Not Applicable

FEDERALLY SPONSORED RESEARCH: Not Applicable

SEQUENCE LISTING OR PROGRAM: Not Applicable

BACKGROUND OF THE INVENTION — FIELD OF INVENTION

This invention relates to a disk brake system which is composed of a rotor and a brake caliper, specifically to providing external cooling for the piston(s) of the brake caliper.

BACKGROUND OF THE INVENTION — DISCUSSION OF PRIOR ART

In a typical disk brake system a caliper holds a pair of hydraulically actuated pistons which force a pair of pads into contact with a spinning rotor. The pads have a high coefficient of friction and when they are clamped onto the spinning rotor, they convert the kinetic energy of the rotor into heat. A lot of heat. Brake pads can reach temperatures well over the melting point of aluminum (~600^cC). Typically, the rotor has an integral vent which, during rotation, moves ambient temperature air through the rotor as a means to cool it down. The brake pads, however, have no such mechanism and cooling is primarily achieved through contact with the rotor and contact with the brake fluid and the brake caliper through the brake caliper piston.

The lack of a good thermal sink for the brake pads leads to two significant problems. First, the heat from the pad can heat up the piston to the point where the hydraulic fluid behind the piston boils, the seals are damaged or the piston warps. Second, the pads can get so hot that they vaporize upon contact with the rotor. This produces a cushion of gas between the rotor and the pads which prevents contact of the pad with the rotor. Both conditions lead to a decrease in the brake efficiency (i.e. termed fade) and, in extreme conditions, can result in complete brake failure. This is not an unknown issue and several patents exist related to cooling disk brake systems. However, they are generally dependent upon the manufacture of specifically designed custom calipers or rotors which is prohibitively expensive in all but the most demanding application. APPENDIX A

For instance, U.S. Patent 5,002,160 is a brake caliper that is manufactured to accept an external pipe that feeds a cooling medium into an integrated ventilation channel in the caliper. U.S. Patent 6,446,766 also incorporates a novel caliper with a ventilation channel for the ducting of air to between the brake pad backing plate and the caliper piston in a manner that is very similar to that of U.S. Patent 5,002,160. Unlike the brake cooler described in this patent application, both devices are integral to a complete caliper design. The dependence upon the requirement for a novel caliper is continued in U.S. Patents 5,284,227 and 5,238,090. The primary failure for all of the current patents related to improving the cooling of disk brake assemblies, is that they require the custom manufacture of the most expensive component of the brake ^' system.

BACKGROUND OF THE INVENTION - OB JECTS AND ADVANTAGES

Unlike^' the previous art, the invention described herein is a modification or accessory to a standard brake pad backing plate and therefore does not require a custom brake caliper, nor does it require modification of the existing brake caliper. Instead, a thermally conductive sheet which is mechanically connected to a . remote heat-sink is employed between the brake pad and the caliper piston(s) as a means to improve the conduction of the heat away from this interface. For the remainder of this document, it will be described as an accessory with^' the understanding that it could be directly incorporated into the brake pad backing plate without difficulty.

The invention also addresses the fact that the more difficult aspect of the art is choosing a material system . capable- of handling the high temperatures and high pressures found at the contact point between the brake caliper and the brake pad backing plate. While high yield strength steel could be used, it has very poor thermal conductivity and would not effectively conduct the heat to the sink. Most common materials with significant thermal conductivity will either have two low a melting point (like aluminum) or too low a yield strength (like copper) to be incorporated for this application. Fortunately, there are high thermal conductivity, high yield strength exotic composites like Copper Tungsten (CuW) which can be used for this demanding application.

Further objects and advantages of my invention will become apparent from a consideration of the drawings ahd the ensuing description.

^' SUMMARY OF THE INVENTION: The present invention includes a thermally conductive sheet employed between the brake pad backing plate

' arid the caliper piston(s) of a high performance brake system. Said thermally conductive sheet is mechanically connected to a remote heat-sink and improves the conduction of the heat away from the brake pad backing plate and the caliper piston(s) interface. Said invention does not require a custom brake APPENDIX A

caliper or modification of a standard high performance brake caliper, but is a complete brake accessory in and of itself.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 is an isometric view of a standard high performance brake caliper with the two external heat-sinks for the brake caliper piston cooler clearly visible above the brake caliper.

Figure 2 is a side view of a standard high performance brake caliper with the heat-sink of the brake caliper piston cooler clearly shown external to the caliper. A cut away view shows more detail.

Figure 3 is a top view of a standard high performance brake caliper and clearly illustrates two brake caliper piston coolers mounted to each respective pad of the disk brake system. .

Figure 4 is a cut away front view of a standard high performance brake caliper with a brake caliper piston cooler clearly mounted between the backing plates of the two brake pads and the caliper pistons. The figure clearly illustrates the position of the thermally conductive sheet of the brake caliper piston cooler between the brake caliper piston and the brake pad backing plate and also illustrates the thermal contact with the external heat-sink.

Figure 5 is an isometric view of a brake caliper piston cooler which clearly illustrates the separate heat-sink in intimate mechanical contact with the thermally conductive sheet.

DETAILED DESCRIPTION OF AN EMBODIMENT:

In the Figures, compon'ents being identical or corresponding to one another are given identical reference numbers.

FIGURES, l through 4 show a disk brake system composed of a rotor 2, and a caliper 1. The caliper is ^■ bolted onto the vehicle chassis (not shown) by means of two threaded holes 3 at the base of the caliper 1. Bolts 4 hold the two halves of the caliper 1 together and form a unit in which two opposed pistons 13 reside. Hydraulic fluid is delivered to the reservoir 15 directly behind the pistons 13 by means of a hydraulic line (not shown) connected to an orifice 6 in the caliper. The caliper has a bleeder screw 5 for the removal of air from the hydraulic system. An o-ring 14 on each piston prevents leakage of the brake fluid 15 around the pistons 13 and rubber dust shields 12, protect the o-rings 14 from damage. The rubber dust shields 12 also act to return the pistons 13 to their initial positions after brake actuation. The motion of the brake pads 8 are constrained by two guide pins 7 which prevent motion of the brake pa^'ds 8 in any direction other that that of the pistons 13 motion. The term "brake pad" commonly refers to a unit composed of a APPENDIX A

brake pad 9 and a brake pad backing plate 8 to which it is cast. For the purposes of clarification these two components are denoted separately herein.

As hydraulic fluid is forced into the brake piston reservoir 15 through the orifice in the caliper 6, the opposed pistons 13, and therefore the brake pads 9, are clamped onto the rotor 2. The force of the pistons 13 is transmitted to the brake pads 9 through the backing plates 8 upon which the brake pads 9 have been cast. In this embodiment, however, the force of the pistons 13 is transmitted through the thermally conductive sheet of the brake caliper piston cooler 10 which is in intimate thermal contact with both the backing plate 8 and the external heat-sink 11. The material system of the brake caliper piston cooler 10 is chosen such that it does not yield under the high contact pressures exerted by the pistons 13, and, further, that it has the characteristics of a high thermal conductivity to allow the heat from the piston 13 and ^■ backing plate 8 interface to be conducted efficiently to a remote heat-sink 11.

FIGURE 5 illustrates one implementation of the brake caliper piston cooler. It is formed from a high yield strength, thermally conductive sheet 10 that is cut in a manner that mimics the brake pad backing plate 8 and it has a mechanically attached high thermal conductivity heat-sink 11. The heat-sink 11 does not have the stringent high yield strength requirements and could therefore be constructed of simple Copper. It is attached to the thermally conductive sheet 10 with either high temperature braze (as shown), or with mechanical fasteners (not shown) and is shaped in a manner to prevent a single linear stress point in the thermally conductive sheet 10 (i.e. it has a curvature at the bottom to prevent the sheet from folding along a line at the base). In such an implementation, the thermally conductive sheet 10 must have yield properties at high temperature that adequately prevent deformation under the stresses of bearing the heat-sink during maneuvering. The holes 16, 17 in the sheet 10 and the heat-sink 11 are designed to allow the original brake pad mounting hardware to be employed to hold the brake caliper piston cooler 10, 11 in place between the brake pad backing plate 8 and the caliper piston 13.

The thickness of the thermally conductive sheet 10 is chosen so as to maximize the thermal cross section of the thermal path to the heat-sink 11 while minimizing the impact on displacing a set of new brake pads 9. In other words, if the thermally conductive sheet 10 is made too thick it conducts away the heat well, but new pads 9 can't be installed because they will hit the rotor 2 in the fully undamped position. On the other hand if the thermally conductive sheet 10 is made too thin, while it is possible to install new pads, the thermal cross section is too narrow to conduct much heat away from the piston 13 and backing plate interface 8. The thermal cross section for which a significant amount of heat is conducted away from the interface will depend upon the thermal conductivity of the thermally conductive sheet 10. Finite element analysis has shown that a significant amount of heat may be conducted away from the backing plate 8 and caliper piston 13 interface if the thermally conductive sheet 10 is 1 millimeter thick and has a thermal conductivity greater than 100 W/mK. APPENDIX A

ABSTRACT:

This invention relates to a disk brake system which is composed of a rotor and a brake caliper. Said caliper is mounted at the rim of the rotor and contains a pair of opposing brake pads that, when clamped onto the rotor by at least one piston type actuator, convert the kinetic energy of the spinning rotor into heat. A thermally conductive sheet which is mechanically connected to a remote heat-sink is employed between the brake pad and the caliper piston(s) as a means to improve the conduction of the heat away from the interface. Said invention does not require a custom brake caliper or modification of a standard high performance brake caliper, but is a complete accessory in and of itself.

APPENDIXA

APPENDIX A

APPENDIX A

APPENDIX A

Figure

APPENDIX B

Provisional Patent Application of

Joseph R. Demers for

TITLE: A HIGH THERMAL CONDUCTIVITY, HIGH YIELD STRENGTH,

METAL COMPOSITE

CROSS-REFERENCE TO RELATED APPLICATIONS: Not Applicable

FEDERALLY SPONSORED RESEARCH Not Applicable

SEQUENCE LISTING OR PROGRAM Not Applicable

BACKGROUND OF THE INVENTION — FIELD OF INVENTION

This invention relates to engineered materials, specifically, the combination of at least two metals through a method of cladding, electroplating and/or forming to produce a metal composite which has improved thermal conduction properties along at least one axis and high yield strength properties along multiple axis.

BACKGROUND OF THE INVENTION — DISCUSSION OF PRIOR ART

A composite may be described as a material produced by combining materials differing in composition or form on a macroscopic scale to obtain specific characteristics and properties. The constituents retain their identity; they can be physically identified, and they exhibit an interface between one another. For instance, a clad metal is a composite that contains two or more layers of different metal that have been bonded together. The bonding may be accomplished by co-rolling, co-extrusion, welding, diffusion bonding, casting, heavy chemical deposition, or heavy electroplating. Clad metals are commonly found on the bottoms of household pots and pans. Copper or aluminum is clad to the stainless steel pan as a means to improve the thermal conduction and de-localize heat from a burner to the entirety of the pan. For a household pan, the cladding process is usually achieved by diffusion bonding: compressing the two dissimilar metals together with high pressure at high temperatures. From this household pan example, it is clear that substantial previous art exists in the realm of cladding and electroplating.

While the system described above can produce a composite with the physical properties of both metals, it is symmetric in two of the three spatial dimensions (i.e. it is a sheet of copper bonded to a sheet of steel). In an application where a high temperature piston applies a high force normal to the copper and steel sheets, the piston would deform the low yield strength copper rather easily regardless of the thickness of the steel APPENDIX B

sheet. While the copper is adequate for conducting the heat from the piston, it cannot handle the applied forces without deformation particularly when at elevated temperature. Most common materials with significant thermal conductivity will either have a low melting point (like aluminum) or a low yield strength (like copper) and cannot be employed for the application of cooling a high temperature piston. While there are high thermal conductivity, high yield strength exotic materials like Copper Tungsten (CuW) which can be used for this demanding application, they are economically unfeasible. An economical solution which addresses all the force and temperature issues is the basis for this patent.

BACKGROUND OF THE INVENTION - OBJECTS AND ADVANTAGES The novelty of what is described herein is a metal composite that differs from standard cladding or electroplating in one significant characteristic: the secondary metal is clad, electroplated or formed onto specific regions of the primary metal and results in a three dimensional composite which retains the structural characteristics of the primary metal.

One motivation for producing a composite with a three dimensional structure would be to achieve greater thermal conductivity along the direction of the secondary material (e.q. copper) while still maintaining the high modulus of the primary metal (e.q. stainless steel). For instance, in the case described above where a stainless steel sheet has had a rib structure etched into it and filled with copper, the thermal conductivity along the rib direction will be greatly enhanced, but when the sheet is compressed between two pistons, the high modulus stainless steel ribs will prevent the deformation of the ductile copper. Patterns may be etched into the stainless steel to either improve thermal conductivity in particular directions or to enhance the modulus of the structure.

Further objects and advantages of the invention will become apparent from a consideration of the drawings and the ensuing description.

SUMMARY OF THE INVENTION:

The present invention includes several descriptions of three dimensional composites; specifically, stainless steel and copper composites which have the thermal properties of the copper and the high yield modulus properties of the stainless steel along multiple axis.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 is a base metal showing the etched pattern from a top view. Figure 1, Section AA is a cut through while Figure 1, Section AA, Detail B is a magnified view of the cut through. The deep etch pattern into the base metal is clear in Figure 1, Section AA, Detail B. Figure 1, Detail C is a magnified view which displays the hidden pattern on the far side of the base metal as dotted lines. As shown, the etched patterns in the APPENDIX B

bottom section are at right angles to each other and thereby prevent the base metal from bending along the longer etch regions in the upper section of the base metal.

Figure 2 shows the same base metal as in Figure 1, but the secondary metal has been plated into the etched regions. This is clearly illustrated in Figure 2, Section AA, Detail B.

Figure 3 is a three dimensional illustration of an etch pattern in a metal sheet which can be employed as the base metal or secondary metal. Figure 3, Detail D clearly shows the etching which results in through holes as well as half-depth plateaus in the metal.

Figure 4, Section EE, Detail F illustrates the complementary nature of the etch pattern as two metal sheets of different materials line up such that the highest non-etched sections of each metal sheet correspond to the through holes in the opposing metal sheet.

Figure 5, Section EE, Detail F shows the two sheets from Figure 4 combined to form a composite with metal from each sheet extending through the complete thickness and forming a "checker-board" pattern on each side.

Figure 6 is a three dimensional view of a metal sheet etched with a longitudal pattern of voids, mid-etch plateau and the un-etched regions. Figure 6, Detail G more clearly illustrates these features.

Figure 7 is the top view of two metal sheets with the pattern illustrated in Figure 6 etched into them. Figure 7, Section HH, Detail I shows the two different metal sheets etched with corresponding voids and raised sections.

Figure 8, Section HH, Detail I illustrates the two etched metal sheets when combined into a composite.

Figure 9 is the top view of a metal composite formed through stamping and forming. Figure 9, Section JJ, Detail K shows the two different metal sheets folded over in a hem in the sections where the corresponding holes are in the second metal sheet.

Figure 10, Section JJ, Detail K illustrates the two stamped and formed metal sheets when combined into the composite. The formed sections clearly complement each other extending completely through the thickness of the composite and in this case running almost the complete length as well. APPENDIX B

Figure 11 is a three dimensional illustration that more clearly shows how the stamped and formed features of the two metal sheets correspond to each other. Figure 11, Detail L magnifies a section of the two sheets more clearly illustrating the features.

DETAILED DESCRIPTION OF AN EMBODIMENT:

In the Figures, components being identical or corresponding to one another are given identical reference numbers.

FIGURE 1 shows a sheet of metal 1 that has a pattern etched or machined into it 2 that can more clearly be seen in the cut through SECTION AA, DETAIL B, 3 and 4. The pattern at the point of the cut through SECTION AA illustrates the voids 3, the thicker sections that remain 4 and the thin metal remaining as a backbone to hold the entire piece together 5. DETAIL C shows how the etched pattern on the sheet is at 45 degrees to the length 6 and that the etched pattern on the hidden side 7 (illustrated by the dashed lines) is at • 90 degrees to the etch pattern on the top side 7. This opposing etch pattern 6, 7 on the sheet 1 stiffens the sheet 1 and prevents it from being bent along the length of the etched pattern 2. FIGURE 2, SECTION AA, DETAIL B, illustrates the etched metal sheet 1 of FIGURE 1 after the voids 3 have been filled with the secondary metal 8 through a process of electroplating, co-rolling, pressing, diffusion bonding or similar. The base metal sheet 1 exists the full thickness 5 of the final composite.

FIGURE 3 is a three dimensional view of a metal sheet-9 into which a pattern (DETAIL D) has been etched, machined or stamped. FIGURE 3, DETAIL D more clearly shows the pattern of the original ^■ thickness region 10, the mid-thickness plane 11, and the through hole 12. The pattern of FIGURE 3, DETAIL D is complementary such that two sheets of metal 9 with the same pattern DETAIL D will fit together. FIGURE 4, SECTION EE, DETAIL F illustrates how the complementary features of two metal sheets 13, 14 with the same pattern shown in FIGURE 3, DETAIL D will fit together as shown in FIGURE 5, SECTION EE, DETAIL F. Unlike the metal composite of FIGURE 1 and FIGURE 2, in this composite FIGURE 4, both metal sheets 13, 14 extend through the thickness of the final composite.

FIGURE 6, DETAIL G is a magnified three dimensional view of a pattern different than that illustrated in FIGURE 3 that has been etched or machined into a metal sheet 15. FIGURE 6, DETAIL G clearly shows the original thickness region 16, the mid-thickness plane 17, and the through hole 18. FIGURE 7, SECTION HH, DETAIL I illustrates how the complementary features of two metal sheets IS, 19 with the same pattern shown in FIGURE 6, DETAIL G fit together as shown in FIGURE 8, SECTION HH, DETAIL I. In a manner similar to that of the metal composite of FIGURE 3, 4 and 5, this composite FIGURE 8, both metal sheets IS, 19 extend through the thickness of the final composite. APPENDIX B

FIGURE 9, SECTION JJ, DETAIL K illustrates two different sheets of metal 20, 21 into which a corresponding pattern of voids 22 and hems 23, 24 have been stamped and/or formed. These features are very similar to the etched sections 16, 17 and 18 illustrated in FIGURE 6, 7 and 8. FIGURE 10, SECTION JJ, DETAIL K shows how the two sheets 21, 22 fit together to form a composite wherein both metals extend the thickness of the composite. FIGURE 11, DETAIL L is a magnified view of a three dimensional rendering that illustrates the corresponding stamped and formed patterns 23, 24, 25 in the two metal sheets 21, 22.

ABSTRACT

This invention relates to metal composites. Specifically, a composite that is formed of a primary and at least one secondary metal that is clad, electroplated or formed onto specific regions of the primary material ^■and results in a three dimensional composite which retains the structural characteristics of the primary metal and is enhanced by the physical characteristics of the secondary metal.

APPENDIX B

SECTlONA-A SCALE 1 1

DETAIL C SCALE4:1

FIGURE 1 APPENDIX B

SCALE 6 : 1

SCALE 1 : 1

FIGURE 2 APPENDIXB

DETAIL D SCALE 4 : 1

FIGURE 3 APPENDIX B

SCALE 1 : 1

FIGURE 4 APPENDIX B

SCALE 1 : 1

FIGURE 5 APPEM⁾IXB

DETAlLG SCALE8:1

FIGURE 6

APPENDIX B

DETAIL I SCALE 4 : 1

FIGURE 7 APPENDIX B

SCALE 4 : 1

FIGURE 8 APPENDIX B

SGALE 6 : 1

Figure 9 APPENDIX B

SECTION J-J SCALE 1 : 1

FIGURE 10 APPENDIX B

DETAIL L SCALE 8 : 1

FIGURE 11

APPENDIX C

Could This Invention Revolutionize Braking? Development of the Fade Stop Brake Cooler By Joseph R. Demers, PIiD

Doc Demers has been writing for Sport Z Magazine since its inception five years ago. He's produced some landmark articles, but none as noteworthy as this one. Here, JD dissects the history and inner workings of brakes. More importantly, he presents—for the first time ever and to a worldwide audience—his potentially groundbreaking automotive invention: The Fade Stop Brake Cooler (FSBC). An SZM exclusive.

The history of the automotive brake system is primarily a narration in materials development. This is because the principles of the brake have always remained the same: ^"friction^" between two surfaces is employed to convert the kinetic energy of a vehicle into thermal energy (heat). Both the drum brake and the disc brake were invented at the turn of the 19^th century. What has changed over time is the size, the velocity, and the resulting kinetic energy of the vehicles that need to be stopped. The increases in kinetic energy have driven the development of materials that can handle higher and higher temperatures while still maintaining their physical characteristics. This is not a minor achievement when you consider that the modern brake system on a race car can reach temperatures in excess of 800⁰C (1550⁰F) which is well over the 65O⁰C (1200⁰F) melting point of aluminum.

My goals for this article are three-fold. First, I would like to briefly document the development of the modern automotive brake system. Second, I would like to discuss what limits the performance of a brake system and common techniques employed to improve this performance. Finally, I would like to introduce a new aftermarket brake product, the Fade Stop Brake Cooler (FSBC), and examine how it can improve even a modern brake system.

History

With just a cursory study of history, it quickly becomes clear that every shade tree mechanic and amateur inventor of the late nineteenth and early twentieth century was trying to develop either a complete automobile or some component for an automobile. As is generally the case, many people developed brake systems that were very similar to one another ... or were completely crazy .

Major Brake Developments, Late 19^th/EarIy 20^th Century

• In 1889 Elmer Ambrose Sperry of Cleveland invented a disc brake for his electric car, which employed electrically actuated pistons to clamp down on the disc.

• In 1902 F. W. Lanchester received a patent for a non-electric disc brake system that employed copper linings that clamped upon a metal disc.

• 1901 to 1902 Wilhelm Maybach and Louis Renault both independently invented the internal drum brake. Wedges rotated by levers push shoes into contact with a drum. APPENDIX C

• In 1907 Herbert Frood developed asbestos containing linings. The new material was quickly adopted by everyone for both drum and disc brakes.

• In 1918 Malcolm Lougheed (who later changed the spelling of his name to Lockheed) developed a hydraulic brake system.

• The Bragg-Kliesrath-invented vacuum-assisted brake booster made its debut on the 1928 Pierce-Arrow and other expensive cars in the late 1920s.

While there were a number of major developments in brake technology at the turn of the 20^th century, three are of particular importance. The first was the development of the asbestos-containing brake material invented by Frood in 1907. 1 state "containing" because even at this time brake linings were a hodge-podge of materials and included things like crysotile asbestos fibers, brass particles, low-ash bituminous coal, and plant fiber. Today, more than 2,000 different compounds can be found in commercial brake linings, but one of them is not asbestos [I]. From a performance standpoint, this is too bad since the physical characteristics of asbestos make it an exceptional filler for brake materials. For the curious, its particularly appealing characteristics are: thermally stable to over 500⁰C (93O⁰F), extremely low thermal conductivity, regenerates friction surface during use, cheap and easy to process, and the asbestos fibers are hard and abrasive [I]. Because of these characteristics, asbestos would remain a primary component of brake linings until the 1980s when health and safety concerns would see its removal from almost everything commercial.

The second key invention of the era was the hydraulic brake system in 1918 by Malcolm Lockheed. Until this time, brakes were typically installed on only the rear wheels because trying to employ rods, pulleys and wires to evenly distribute the motion of a pedal or lever equally to four wheels was extremely difficult. On the other hand, hydraulic systems are equally distributive. The 1921 the Model A Duesenberg was the first passenger car to employ four wheel, hydraulically actuated, internal drum brakes as a standard feature. Even though the disc brake had been invented, drum brakes were more effective. This is due to the fact that for a top-pivoting system, the rotating drum wedges the trailing brake shoe into the drum surface. This effectively results in a "power assist," which improves the effectiveness of the brake. Disc brakes have no such mechanism and although hydraulic leverage can be improved by increasing the caliper piston to master cylinder piston ratio, this has economical and practical limitations [2].

The final invention of significant interest was the development of the vacuum brake booster sometime in the 1920s. While I have found information that suggests that the vacuum brake booster was invented by Caleb S. Bragg and Victor W. Kliesrath for the aeronautics industry around 1924, Brain Joseph of Classic and Exotic Services (a supplier of Bragg-Kliesrath vacuum boosters) has informed me that many expensive cars from around that era had vacuum brake boosters [3]. For example, the 1928 Pierce Arrow was equipped with a Bragg-Kliesrath vacuum booster while the 1928 Minerva employed a De Wander vacuum booster. Duesenberg, Stutze, Lincoln, Cadillac, and Mercedes of the early 1930s also employed vacuum-assisted drum brakes. Even though the incorporation of a vacuum brake booster made it possible to employ disc brakes, four-wheel drum brakes remained the standard for decades primarily because they were cheaper to implement and they were capable of stopping the automobile.

3S APPENDIX C

Disc vs. Drum

In the 1960s the metal content of brake materials increased, the size and horsepower of the automobiles increased and, suddenly, drum brakes could no longer meet the increased demands; the disc brake became a requirement. Several characteristics make a disc the better geometry for a brake than a drum. First, and primarily, heat generated between the brake lining and the brake surface in a drum must travel through the drum material to be radiated into the ambient air. Cast iron is a relatively poor thermal conductor and the temperature gradient through the drum material will be high. One way to minimize the problem is to make the drum from a material with a high thermal conductivity, like aluminum, and use a cast iron lining for the brake surface. Datsun chose to employ this composite drum on the rear brakes of the 240Z. With a disc brake, the braking surface interacts with the ambient air 'directly and the thermal conductivity of the disc (i.e., rotor) is not as great an issue. Further, it is much easier to incorporate an internal vent to move air through the rotor to help dissipate the heat. Such a disc is refefred^'to as a vented rotor (see Figure 1) and is now the industry standard for front brakes.

There are two other, more subtle, issues that make the drum inferior to the disc. The first is due to thermal expansion. As the drum heats up, it expands and increases the distance between the brake shoe and the brake surface. This results in greater pedal travel as the drums heat up. On the other hand, as a disc expands it actually decreases the distance between the pads and the brake surface, which results in little or no change in the pedal travel. The second issue has to do with rotational inertia. Given a drum and a disc of the same mass, almost twice as much work will be required to get the drum to rotate at the same speed as the disc [5]. How does this impact the performance? Well, it will require more of your precious and limited torque to spin the brake drums up to speed than it will to spin up rotors. Also, it will require more work to change the angular velocity of the drum than the rotors. This means the car with drums will not respond as quickly to acceleration and deceleration as the same car with rotors of the same mass. So, if disc brakes are so superior to drum brakes, why then do a significant number of automobiles still have drum brakes on the rear axle?

Before discussing the answer to this question, it is worth asking a second, leading question: what stops the moving automobile? If your answer is "the brakes," then please think about the time you locked up all the wheels on that patch of ice. Did the car stop? As many of us have discovered first hand, it is possible to completely stop the rotation of the wheels via the brakes and yet not arrest the motion of the car. It is actually the interaction of the tires with the road that stops the automobile. If there is no friction (e.g., like on an ice patch) or no force (e.g., tire leaves the surface of the road) then the automobile will not stop regardless of how efficient the brakes are. Armed with this knowledge, let's revisit the question of why automobiles are built with drum brakes on the rear axle. When a forward moving automobile stops, it rotates about an axis that goes through the center of gravity that is located somewhere between the front and rear axles. The front of the automobile dips down while the back end rises up [6]. This is equivalent to the force on the front tires increasing and the force on the back tires decreasing. Now, since the force that the tire can exert to decelerate the car is equal to the frictional coefficient of the tire times the downward force on the tire, as the force on the tire decreases (like on the back tires), the amount of deceleration that can be achieved decreases. APPENDIX C

Therefore, regardless of the efficiency of the rear brakes, they will contribute less to arresting the forward motion of the automobile than the front brakes. And, since it's cheaper to incorporate an emergency brake into a drum, manufacturers have left it in place.

There is one final aspect to the interaction of the tire with the road that needs to be addressed in order to discuss the benefits of an Anti-lock Braking System (ABS). Fact: the contact patch of the tire is not moving with respect to the road surface. That's right, the automobile may be moving at 60 mph with respect to the road, but the contact patch of the tire is not. If the contact patch does move with respect to the road, then this is referred to as sliding and typically occurs when a driver "locks up" the brakes and stops the wheel from rotating. Now, the key point with this is that the static coefficient of friction (non-sliding) is typically higher than the kinetic coefficient of friction (sliding). Plugging either of these two coefficients into the formula described in the previous paragraph illustrates that once the tire starts sliding, the amount of force that it can apply to decelerating the automobile decreases compared to the noή-slidirig case. Therefore, the shortest stop will be achieved by applying the brakes to a point where the tire is just about to slip, but does not. What ABS does is monitor the rotation of the wheel and decrease the braking force as the wheel begins to lock-up [7].

Why Brakes Fail

Now that we can safely assume that it is possible to prevent the tire from slipping, what then limits the ability of the brakes to stop the car? In a word: heat. In a high- performance disc brake system a caliper holds a pair of hydraulically actuated pistons that force a pair of brake pads into contact with the spinning rotor (Figure 2). [Author's Note: Ηie first generation Z cars employ dual piston calipers, but the majority of domestic vehicles employ single piston calipers not described in this article.] The pads have a high coefficient of friction and when they are clamped onto the spinning rotor they convert the kinetic energy of the vehicle into heat— a considerable amount of heat. Kwangjin Lee of Delphi Automotive Systems has performed measurements of brake temperatures in the various disc brake components during a simulated mountain decent in a typical mid-size automobile with semi-metallic brake pads [8]. Ninety brake applications over a thirty minute interval resulted in brake rotor and brake pad temperatures that were nearly equal at 450⁰C (840⁰F), caliper temperatures of 150°C (300⁰F), and brake fluid temperatures of almost 100⁰C (212°F). Now that we have a picture of what the temperature profile is, we can discuss the two issues that lead to a significant degradation of brake performance or even failure: pad vaporization and brake fluid vaporization (i.e., boiling).

The most common degradation in brake performance occurs when the rotor reaches a temperature that exceeds the operating temperature of the pad. The pad contacts the rotor, vaporizes, and produces a cushion of gas that prevents further contact of the pad with the rotor. This leads to a condition referred to as "brake fade." The brake pedal still feels stiff, but application won't slow the automobile. A common method to decrease brake fade is to install higher temperature brake pads. While this may seem an obvious solution it is not without drawbacks. For instance, the Hawk MT-4s are competition pads that have an operating range of 200 to 65O⁰C (400 to 1200⁰F) [9]. While it would be very difficult to overheat these pads during typical driving, they are relatively expensive, and APPENDIX C

they will not work effectively until they reach a temperature of 200⁰C (400⁰F). A more suitable pad for a street car may be the Hawk HPS Plus pads, which have a temperature range of 40-425⁰C (100-800⁰F). There are a number of other manufacturers that offer high-temperature brake pads including: Wilwood, EBC, Performance Friction Brakes, US Brakes, Porterfield, and more.

While it may be difficult to believe, there are some applications in which even the MT-4s may start to vaporize. Such an application may require another modification that is still fairly economical: cross-drilled rotors. Cross-drilling a vented rotor (Figure 3) will help reduce the brake fade caused by the vaporizing pads by creating a path by which the gases can escape the pad-rotor interface. The cross-drilling also increases the surface area to volume ratio of the rotor and the turbulence of the air around the rotor, both of which will improve the heat transfer to the air. This helps the rotor cool more quickly. Cross- drilling has two detrimental effects however. First, it decreases the area of the pad that is in contact with the rotor. This decreases the heat transfer from the pad to the rotor, because, believe it or not, the rotor is the primary heat sink for the pads. Secondly, it decreases the mass of the rotor and therefore the thermal capacity. The thermal capacity (also known as heat capacity) is "the proportionality constant between the heat added to the object and the change in temperature that results [11]." This means that for equivalent braking in the absence of improved cooling, the cross-drilled rotor temperature will be higher than that of the non-cross drilled rotor. However, I am sure that these failings are more than offset by the improved cooling. In any case, this discussion has been about cross-drilled vented rotors. It is pointless to cross drill a non- vented rotor; where will the gases from the vaporized pad go? Instead of cross-drilling solid rotors it is much more effective to slot them (Figure 4).

While the brake system that we have discussed will handle the hypothetical mountain decent, high temperature pads and cross-drilled rotors are generally only a baseline requirement for competition. For the true automotive enthusiast it is generally necessary to install a "Big Brake Kit" /SZM will be reviewing the 350Z/G35 kit from Racing Brake, www.racingbrake.com, in an upcoming issue— EdJ These kits often increase the size of the rotors, the number of caliper pistons, and the size of the pads. This results in several benefits: first, if the larger rotor has a greater mass it will have a greater heat capacity; , second, the larger rotor will have an increased surface area for improved cooling; and third, the larger disk radius means that the same caliper will deliver more torque since it is further from the center of the wheel (i.e., it has more leverage). A common misconception is that the larger pad area is what generates the greater torque. But, unless there is a significant increase in the radius of the rotor (the third item), or an increase to the caliper piston to master piston size ratio [2], or an increase in the size of the vacuum booster, then increasing the size of the pads will not exert more force than what was applied with the stock system and there will be no change in the stopping distance [13]. The larger pad area will improve your braking from the standpoint of lowering your pad temperature and therefore reducing fade. One other point about "Big Brake Kits" is worth mentioning: if the larger rotors have more mass than the stock rotors (and therefore greater thermal capacity), they will require more torque to spin up as well as to stop. This will cause a slight decrease in the automobile's ability to accelerate and decelerate.

Another potential upgrade that will lower pad temperature and therefore decrease fade is to switch to carbon ceramic rotors (that even sounds expensive, doesn't it?). If you APPENDIX C

can afford it, switching to carbon ceramic rotors is a win-win-win situation. Carbon ceramic rotors are lower mass than their iron counterparts, which improves the "flywheel" effect (the first "win"). They also have a much higher thermal conductivity than that of iron. This helps to distribute the heat throughout the rotor and increases the rate of cooling (the second "win"). Finally, the carbon ceramic material has a higher specific heat than that of iron (the third "win"). Unlike the previously defined heat capacity, the specific heat is the ratio of the heat capacity of a substance to the heat capacity of a reference substance, usually water [11]. For instance, the specific heat of cast iron is approximately 450 J/(kg K) while that of a carbon ceramic can range from 600 to 1700 J/(kg K) [14]. This means that if a carbon ceramic rotor with a specific heat of 900 J/(kg K) is installed on one side of an automobile while a cast iron rotor of twice the mass is installed on the other side, they will both reach the same temperature under the same braking conditions. Unfortunately, you will pay (and I mean in the thousands) for a set of carbon ceramic rotors.

^"At mis^" point we^~have built a brake system that can easily handle the standard mountain decent, but on our heated sprint at the track, we ended up in dirt because of brake failure. What happened? Figure 5 illustrates the effect of water content on the boiling point of DOT 3 brake fluid [15]. From Kwangjin Lee's work [8] we know that our brake fluid temperature was getting close to 100⁰C (212⁰F) with the stock brakes and, while the cross-drilled and vented rotors with the better pads decreased the effects of brake fade, the brakes got hotter from our more aggressive driving and pushed the old brake fluid to the limit. The brake fluid temperature hit 130⁰C (265°F) and the fluid started to boil. Boiling (or vaporization) occurs at a temperature where the vapor pressure becomes great enough to establish bubbles of vapor in the liquid, and, while liquids are incompressible, gases are not. The boiling point is also dependent upon pressure, so when you step on the brakes, the boiling point will increase, the bubbles will collapse, and the brakes may start working again. This results in a "mushy" brake pedal response. At some point, however, the pressure will not offset the boiling point and the brakes will fail entirely. Historically, the only solution to this problem was to employ a high-temperature synthetic hydraulic fluid and change it frequently. For instance Wilwood has a high-temp brake fluid with a dry boiling point of 315°C (600⁰F) and a wet boiling point of 215°C (42O⁰F) [16]. There is now another solution available to prevent brake fluid boil: the Fade Stop Brake Cooler [17].

Fade Stop Brake Cooler

As previously discussed, the rotor has an integral vent that, during rotation, moves ambient temperature air through the rotor as a means to cool it down. The brake pads, however, have no such mechanism and cooling is primarily achieved through contact with the rotor and contact with the caliper piston. Judging from the glowing rotor and the brake pad fire in Figure 6, it is clear that cooling through contact with the rotor may not always be effective. It is therefore not surprising that it is possible to get even high temperature brake fluid to boil.

The Fade Stop Brake Cooler (FSBC), shown in Figure 7, is an inexpensive aftermarket accessory that fits between the brake pad backing plate and the caliper piston (Figure 8). The stainless steel of the novel metal composite prevents deformation of the ductile copper that is providing a thermally conductive path from the interface to a heat APPENDIX C

sink located externally to the caliper. It was the development of this composite, called Thermal Steel, which made manufacturing of the FSBC economically feasible. [Author's Note: Tlte FSBC and Thermal Steel are subjects of separate patent applications.] Figure 9 is a picture of the prototype FSBC lying on a brake pad from a 1970 Datsun 240Z. While the gold plated copper ducts are currently bent away from the brake pad backing plate, upon installation they will fit into the spaces between the stainless steel fingers. This can be more clearly seen in Figure 10. The primary goal of this article is to detail the results of testing the prototype FSBC on my 1970 240Z.

FSBC testing

In order to monitor the temperature of the brake pad backing plate and caliper piston interface with and without the FSBC, it was necessary to construct two custom thermocouple assemblies that would fit onto the end of the caliper pistons. Figure 11 is a picture of two thermocouple assemblies with an Omega HH306 data-logger [19]. Figure T2 illustrates how the thermocouple assembly is installed between the FSBC and the caliper piston. On the caliper without the FSBC, the thermocouple assembly is simply installed between the brake pad backing plate and the caliper piston (not shown). For the first experiment I used the organic Raybestos pads that were already on my car (they both had more than 0.30 inches of pad left). Figure 13 is a picture of the front driver's side brake caliper with the FSBC installed. Because of the wheel offset, installing the FSBC on the inner side of the brake caliper did not result in issues with wheel clearance, but this will need to be addressed for the outer side of the brake caliper and for different wheel sizes. Generally speaking, there is sufficient room for a modestly sized FSBC inside the wheel. Also shown in the photograph is one of the two cold air ducts that have been installed for this experiment: the one on the driver's side is directed at the FSBC while the one on the passenger's side is directed at the brake caliper in roughly the same place.

After installation was completed, the car was taken for a test drive and it was not possible to tell that the FSBC was installed; the brakes felt exactly the same. The caliper piston temperature for both the caliper with the FSBC and the caliper without the FSBC were simultaneously recorded on the Omega HH306 at two second intervals during a descent from 3,500 to less than 1,000 feet along the Los Angeles Crest Highway, State Route 2. Recording continued as I drove at highway speeds after the mountain descent.

The data is illustrated in Figure 14 with a best-fit five-term polynomial line and clearly shows an average 70⁰C (16O⁰F) difference in maximum temperature between the two! That is a difference of more than 70 percent! In several cases the instantaneous difference hits over 90⁰C (200⁰F). Finite element analysis (a.k.a., computer modeling) had predicted that the FSBC would provide at most a 20 percent improvement and I was expecting something in the range of 10-15 percent, but 70 percent is simply amazing. But, because I was very skeptical of such a large temperature difference, and, because I smoked the Raybestos pads in this single test, I decided to perform a series of tests with a set of Sumitomo SP51H semi-metallic brake pads. Two tests were performed: one with the FSBC on the driver's side and one with FSBC on the passenger's side. Nothing else in the set-up was changed during these two tests. As was expected, variations in the thermocouple response, pad thickness, and possibly the airflow resulted in different results for the two sides. Therefore, the data from the two sides was averaged and the results are illustrated in Figure 15Figure 15 with a best-fit five-term polynomial line. It is APPENDIX C

clear that the caliper with the FSBC installed stays an average of 30 percent cooler. While this is less than half of the difference obtained with the Raybestos pads, it is more reasonable as it includes the averaging of the data taken from both sides and the testing did not result in the destruction of the Sumitomo pads.

One final point: the rates of cooling seem similar for the caliper with and the caliper without the FSBC. This puzzled me at first, but then I realized that the two rates may not be directly compared because they are dependent upon the temperature difference between the pad and ambient air. In other words, a hotter object will cool faster because there is a greater temperature difference. If the two caliper pistons had started at the same temperature, it would be possible to see that the caliper with the FSBC cools faster, but, as they don't start at the same maximum temperature, it is difficult to compare them. What may be comfortably stated is that after the same amount of time, the caliper piston with the FSBC will always be significantly lower in temperature.

^"FSBC Conclusions

Before completing the research required to write this article I thought that the FSBC was simply an interesting concept. Having since learned that a common limit of a modern high-performance brake system is the boiling point of the brake fluid, I now appreciate the potential importance of this Patent- Applied-For innovation. The brake caliper with the FSBC installed was over 4O⁰C (105⁰F) cooler than the caliper without it (Figure 15). In instances where the DOT 3 brake fluid has a significant amount of water (see Figure 5), having the FSBC installed may prevent brake failure.

Another potential benefit occurs regarding one of the principle trade-offs in a high-performance brake system between the impact of the rotor size on the thermal capacity and the rotational inertia: too small a rotor and your brake fluid boils, to large a rotor and your acceleration suffers. With the FSBC it is now possible to decrease the rotor size while still maintaining the operational temperature of the brake fluid.

The FSBC tested for this article was a prototype. It produced a maximum caliper piston temperature difference of 70 percent during the initial test with the Raybestos organic pads (Figure 14), and an average temperature difference of 30 percent during the tests with the Sumitomo pads (Figure 15). A significant amount of data has been recorded with the Sumitomo pads and generally produces an average difference of 30 to 40 percent.

The FSBC as designed for manufacturing will be similar to the rendering in Figure 7 and will be sold through common automotive parts retailers. The FSBC may be employed on many different make and model automobiles with the only requirement being that they have high performance multi-piston calipers with suitable clearance between the calipers and the wheels. Some of the automobiles that the FSBC will work on are: 1^st generation Z cars, G35 and 350Zs models equipped with factory installed Brembo brakes, Mitsubishi EVOs, Subaru WRXs, almost all Porsches, and, surprisingly, almost the entire line of Toyota trucks. Initially, the FSBC will have to be for track use only, but Department Of Transportation approval will be sought so that the FSBC may be used on public thoroughfares. For information related to the availability of the FSBC for your automobile, please contact your automotive parts retailer. APPENDIX C

[I] Peter J. Blau, Compositions, Functions, and Testing of Friction Brake Materials and Their Additives, ORNL/TM-2001/64 prepared for the U.S. Department of Energy under contract DE-AC05-00OR22725. August 2001.

[2] A discussion about how hydraulic leverage works is beyond the scope of this article but the reader is invited to read the How Stuff Works website (http://auto.howstuffworks.com/brake3.htm).

[3] Communication with Brian Joseph of Classic and Exotic Services, Inc. a rebuilder and supplier of Bragg-Kliesrath Vacuum Boosters for classic automobiles. 2032 Heide, Troy, MI 48084. (http://www.classicandexotic.com.^')

[4] Images of the solid and vented rotor were found at the http://www.iag-lovers.org/ web ^' site.

[5] It is beyond the scope of this article to explain the concept of torque and horsepower to their fullest. For more information, the reader is invited to study the following two wonderful websites in this order: http ://vettenet.o rg/torq uehp. html and httpV/www.mazdaόtech.com/articles/suspension/unsprung-weight-and-inertia.html (particularly the MS Excel sheets at the bottom of this page). Please note, the end-all for such discussions is reference [H].

[6] Tom McCready and James Walker, Jr. of scR motorsports have a very good white paper on the dynamics of braking (httpy/www.stoptech.com/whitepapers/brakebiasandperformance.htm).

[7] The reader is invited to read the How Stuff Works website

(http ://auto .howstuf fworks .com/anti- lock-brake .htm) or simply find a book on ABS systems at their local library.

[8] Kwangin Lee, "Numerical Prediction of Brake Fluid Temperature Rise During Braking and Heat Soaking," International Congress and Exposition Detroit, Michigan March 1-4, 1999. SAE Technical Papers Series 1999-01-0483.

[9] The different compounds with their temperature ranges were available on the Hawk website (http ://w ww . hawkperformance. com/), but have since been removed. One can contact Hawk for the details or check out Precision Brakes Hawk related website (Mp://www.precisionbrakescompany.corn/hawlchtml)

[10] Image of the KVR rotors was found on the http://www.pdm- racing.com/products/subaru corner.html web site.

II 1] David Halliday and Robert Resnick, Fundamentals of Physics. 1988, 3^rd Ed. John Wiley & Sons, New York, New York. APPENDIX C

[12] Image of the vented and slotted rotors was found on the http://www.next-gear.com/ web site.

[13] StopTech has a number of good white papers in the technical section of their website (www.stoptech.com/technical/). The one I refer to with this reference is the Brake Systems and Upgrade Selections written by Stephen Ruiz and Carroll Smith. (http://www.stoptech.com/whitepapers/brake systems and upgrade selections 122701. htm). I suggest everyone interested in brake systems read it carefully.

[14] SIGRASIC is a carbon ceramic material produced by SGL Carbon Group. The characteristics of the material may be found on their website.

(http ://www . sglcarbon. com/sgl t/industrial/si grasicΛ . SGL Carbon Group produces brake rotors (http://www.sglcarbon.com/sgl t/img/brakedisc/disc.htmr).

[T5] ^"J:E: Hunt^'ef, S.^'S.^'Caftief, D^". J. Temple and R. C. Masόri, "Brake Fluid Vaporization^" as a Contributing Factor In Motor Vehicle Collisions," SAE 980371, 1988.

[16] Info on the Wilwood brake fluid may be found at: httpV/wNvw.wilwood.com/Products/OOβ-MasterCylinders/O^-EXP/index.asp.

[17] Info on the Patent Applied For FSBC can be found at http ://www.fo urproducts.com/.

[18] Dave.Coleman and Josh Jacquot, Project EVO vs Project STI, Sport Compact Car, September 16(9) pgs. 189-96. 2004

[19] Omega Incorporated (http:/Avww.omega.com/)

APPENDIX C

Solid Rotor Vented Rotor

Figure 1 : A comparison of a solid rotor and a vented rotor [4].

APPENDIX C

Figure 2 : A cut through of the dual piston brake caliper found on the 1970 Datsun 240Z. Brake fluid pumped into the inlet forces the pistons to clamp the brake pads onto the rotor. The rotor pictured here is a solid one.

APPENDIX C

Figure 3 : A picture of a cross-drilled vented rotor (top) and a cross-drilled solid rotor (bottom) [10].

APPENDIX C

Figure 4 A picture of a pair of slotted and vented rotors [12]

APPENDIX C

APPENDIX C

Figure 6 : In a Sport Compact Car article the authors captured this photograph of a brake pad fire after a mountain decent. [17] APPENDIX C

Figure 7 : A solid rendering of the Fade Stop Brake Cooler. APPENDIX C

Figure 8 : A solid rendering of a set of installed Fade Stop Brake Coolers. APPENDIX C

Figure 9 : A photograph of the prototype FSBC with a brake pad from a 1970 240Z.

APPENDIX C

Figure 10 : Another photograph of the FSBC from a different angle showing how the fingers of the stainless steel and copper line up. APPENDIX C

Figure 11 : The Omega HH306 data-logger shown with the two thermocouples mounted in stainless steel donuts. APPENDIX C

Figure 12 : An illustration of how the stainless steel donut with the thermocouple (blue) is mounted between the FSBC and the caliper piston on the driver's side disc brake. A similar thermocouple is mounted on the passenger's side between the brake pad backing plate and the caliper piston. APPENDIX C

Fⁱgure 13 : The FSBC mounted on the driver's side brake caliper. A duct provides airflow to the FSBC and the thermocouple connector from the thermocouple can be seen hanging in the background between the duct and the FSBC. A similar duct is present on the passenger's side, but there isn't an FSBC, just a thermocouple.

APPENDIX C

Figure 14 : Data taken during a single test with the Raybestos pads at two-second intervals on a decent from 3,500 feet to 1,000 feet along the Los Angeles Crest Highway, State Route 2.

APPENDIX C

200 400 600 aoo Time (sec)

Figure 15 : The average of data taken from two separate tests with the Sumitomo pads: one with the FSBC on the driver's side and one with the FSBC on the passenger's side. Data was recorded at two-second intervals on a decent from 3,500 feet to 1,000 feet along the Los Angeles Crest Highway, State Route 2.

Claims

What is claimed is:

1. A brake cooling apparatus for use in a disk brake system of a moveable vehicle, the disk brake system having a caliper which includes a hydraulic piston for moving a brake pad into a forced contact with a rotor that rotates when the vehicle is moving, where the forced contact between the rotor with the brake pad reduces the rate at which the rotor is iotating to slow the movement of the vehicle and the forced contact generates heat in the brake pad, the cooling apparatus comprising: a thermally conductive sheet for positioning in thermal communication with the brake pad, the conductive sheet including a thermally conductive material for conducting heat away from the brake pad; and a heat sink thermally connected to the conductive sheet and positioned away from the brake pad when the conductive sheet is hi thermal communication with the brake pad, the heat sink having at least two cooling fin members for dissipating heat into a cooling medium, the heat sink receiving heat from the brake pad through the conductive sheet and dissipating the heat into the cooling medium to cool the brake pad.

2. A brake cooling apparatus as defined in claim 1 wherein the brake pad is connected to a backing plate and the conductive sheet is captureα oeiween the piston, and tie backing plate when positioned in thermal communication with ^■ the brake pad.

3. A brake cooling apparatus as defined in claim 1 wherein the thermally conductive material of the conductive slieet has a thermal conductivity greater than 100 Watts/meter Kelvin.

4. A brake cooling apparatus as defined in claim 1 wherein the thermally conductive sheet is 1 millimeter thick.

5. A brake cooling apparatus as defined in claim 1 wherein the heat is dissipated into cooling medium that is ambient air.

6. A brake cooling apparatus as defined in claim 1 wherein the conductive sheet includes a high yield strength material in. addition to the thermally conductive material.

7. A brake cooling apparatus as defined in claim 1 wherein the brake pad is permanently attached to the conductive sheet and the piston contacts the conductive sheet to move the brake pad into forced contact with the rotor.

8. A brake cooling apparatus as defined in claim 1 wherein the thermally conductive material in the thermally conductive sheet is copper.

9. A brake cooling apparatus as defined in claim 1 wheiein the characteristic of the heat sink for dissipating heat includes thermally conductive cooling fin members.

10. A brake cooling apparatus as defined in claim 9 wherein the rotor defines a plane and the thermally conductive cooling fin members extend outwardly with respect to the plane.

11. A brake cooling apparatus as defined in claim 1 wherein the caliper has a peripheral outline and the heat sink is positioned entirely externally to the peripheral outline when the sheet is in thermally communication with, the brake pad.

12. A method for cooling a brake pad in a disk brake system of a moveable vehicle, the disk brake system having a caliper which includes a hydraulic piston for moving a biake pad into a. forced contact with a rotor that rotates when the vehicle is moving, where the forced contact between the rotor with the brake pad reduces the rate at which the rotor is rotating to slow the movement of the vehicle and the forced contact generates heat in the brake pad, the method comprising: inserting a thermally conductive sheet between the brake pad and the hydraulic piston to receive heat from the brake pad; and positioning a heat sink having at least two cooling fin members at a location away from the brake pad in surrounding air, wherein the heat sink is attached to the thermally conductive sheet and the heat sink receives heat from the brake pad through the conductive sheet and dissipates the heat with the cooling fin members.

13^". A method, as defined in claim.12 wherein" the brake pad is connected -to a backing p late and-inserting the thermally conductive sheet includes positioning the conductive sheet between the piston and the backing plate.

14. A method as defined in claim 12 wherein the brake pad is connected to the thermally conductive sheet and inserting me thermally conductive sheet includes inserting the brake pad into the caliper.

15. A method as defined in claim 12 wherein the heat sinkreceives the heat from the brake pad through copper in the conductive sheet

16. A method as defined in claim 12 wherein the heat sink dissipates the heat to surrounding air with theimaliy conductive cooling fin members.

17. A method as defined in claim 16 wherein the rotor defines a plane and the thermally conductive cooling fin members extend outwardly with respect to the plane.

18. A method as defined in claim 12 wherein positioning the heat sink away from the brake pad includes positioning the heat sink entirely externally to the caliper when the sheet is in thermal contact with the brake pad.

19. A brake cooling apparatus for use in a disk brake system of a moveable vehicle, the disk brake system having a caliper which includes a peripheral outline and which includes a hydraulic piston for moving a brake pad into a forced contact with a rotor that rotates when the vehicle is moving, where the forced contact between the rotor with the brake pad reduces the rate at which the rotor is rotating to slow the movement of the vehicle and the forced contact generates heat in the brake pad, the cooling apparatus comprising: a heat receiving portion in thermal communication with said brake pad and a distal, heat dissipating portion- extending out of the peripheral outline of the caliper and in thermal communication with said heat receiving portion for receiving the heat from the heat receiving portion by thermal conduction and, thereafter, for dissipating the heat into a cooling medium.