Abstract:
The present disclosure provide various systems and methods for cooling mobile platform braking systems, e.g., braking systems for automobiles, aircraft, motorcycles, etc., utilizing heat pipes. The heat pipes are disposed within components of the braking systems, e.g., brake rotors, calipers and brake pads, to efficiently remove large amounts of heat from such components that is generated during use of the respective braking system to slow and/or stop movement of the respective mobile platform.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/507,219, filed on Jul. 13, 2011. The disclosures of the above application is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present teachings relate to braking systems for mobile platforms, and more particularly to systems and methods for cooling mobile platform braking systems via heat pipes. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    The braking systems, also referred to herein simply as brakes, for many mobile platforms, e.g., automobiles, aircraft, motorcycles, etc., use friction to convert kinetic energy to heat. Heat is a necessary by product of how brakes work. However, these areas are all temperature limited. For example, in contemporary disc brake systems there are generally three key components that are subject to heat generated by use of the braking system: 1) the brake rotors; 2) the brake calipers; and 3) the brake pads, all of which are subject to large amounts of heat during use. 
         [0005]    This is significant as the total amount of braking provided by the respective braking system is proportional to the total amount of heat produced. Hence, removing/dissipating the heat from such components is important to the efficiency, capability and reliability of the respective braking system. Known braking systems rely on direct contact with the heated components by air flowing around the components to remove/dissipate the heat. This method of cooling or heat removal/dissipation is highly inefficient and limits the useful life of such components. For example, traditional braking system rotors are internally finned to help to pump air thru them, however they are still extremely limited in their ability to shed heat as the air flow inside the wheel is limited. Additionally, although the rotors can be manufactured to tolerate the extremely high temperatures, the surrounding components (namely the calipers) cannot. 
         [0006]    Particularly, the calipers of the braking system can tolerate the least amount of heat and are most subject to failure due to the heat generated by operation of the braking system. If the brake caliper gets too hot, there is an increased possibility that the brake fluid will boil, which results in an inability for the caliper to exert proper pressure on the brake pads. This in turn reduces the ability of the brakes to slow and/or stop the respective mobile platform. Furthermore, with excessive heat the piston could stick within the caliper, or rubber seals can fail. 
       SUMMARY 
       [0007]    The present disclosure provide various systems and methods for cooling mobile platform braking systems, e.g., braking systems for automobiles, aircraft, motorcycles, etc., utilizing heat pipes. The heat pipes are disposed within components of the braking systems, e.g., brake rotors, calipers and brake pads, to efficiently remove large amounts of heat from such components that is generated during use of the respective braking system to slow and/or stop movement of the respective mobile platform. 
         [0008]    Further areas of applicability of the present teachings will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings. 
       DRAWINGS 
       [0009]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present teachings in any way. 
         [0010]      FIG. 1  is a cross-sectional view of a heat pipe cooled brake system, in accordance with various embodiments of the present disclosure. 
         [0011]      FIG. 2A  is a cross-sectional view of a heat pipe cooled rotor of the system shown in  FIG. 1 , in accordance with various embodiments of the present disclosure. 
         [0012]      FIG. 2B  is another cross-sectional view of the heat pipe cooled rotor of the system shown in  FIG. 1 , in accordance with various embodiments of the present disclosure. 
         [0013]      FIG. 3  is a cross-sectional view of a heat pipe cooled caliper of the system shown in  FIG. 1 , in accordance with various embodiments of the present disclosure. 
         [0014]      FIG. 4  is a cross-sectional view of a heat pipe cooled brake pad assembly of the system shown in  FIG. 1 , in accordance with various embodiments of the present disclosure. 
     
    
       [0015]    Corresponding reference numerals indicate corresponding parts throughout the several views of drawings. 
       DETAILED DESCRIPTION 
       [0016]    The following description is merely exemplary in nature and is in no way intended to limit the present teachings, application, or uses. Throughout this specification, like reference numerals will be used to refer to like elements. 
         [0017]    By removing heat from the various components of braking systems to areas that can better shed/dissipate the heat (such as heat sinks, heat exchangers, etc.) the total amount of heat that can be removed is increased. In order to move large amounts of heat through relatively small areas and small differences in temperature, heat pipes can be used to facilitate the necessary heat transfer. 
         [0018]    As all the various embodiments of the present systems and methods for cooling mobile platform braking systems described herein are based on heat pipes, all of the various embodiments are passive in nature. 
         [0019]    Generally, heat pipes are a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between hot and cold interfaces. A typical heat pipe consists of a sealed hollow tube made of a thermally conductive material, e.g., a thermally conductive metal such as copper or aluminum. The heat pipe contains a relatively small quantity of a “working fluid” (such as water, ethanol or mercury) with the remainder of the heat pipe being filled with a vapor phase of the working fluid, all other gases being substantially excluded. Heat is transferred from an evaporator end of a heat pipe to an opposing condenser end of the heat pipe by a rapid heat vaporization of the working fluid from the evaporator end to the condenser end. 
         [0020]    More particularly, heating the evaporator end of the heat pipe will cause the working fluid inside the heat pipe at the evaporator end to turn to vapor, thereby increasing the vapor pressure inside the heat pipe. Latent heat of evaporation absorbed by the vaporization of the working fluid reduces the temperature at the evaporator end of the heat pipe. Moreover, the vapor pressure at the evaporator end of the heat pipe is higher than the equilibrium vapor pressure at the condenser end of the heat pipe. This pressure difference drives a rapid mass transfer of the heated vaporized working fluid from the evaporator end to the condenser end of the heat pipe where the vapor condenses back to a fluid state, thereby releasing its latent heat and heating the condenser end of the heat pipe. The condensed working fluid then flows back to the evaporator end of the heat pipe. 
         [0021]    Referring now to  FIG. 1 , the present disclosure provides a heat pipe cooled (HPC) braking system  10 . A mobile platform, e.g., automobile, aircraft, motorcycle, etc. can include the HPC braking system  10  disposed within the structure of each suspension and wheel assembly of the respective mobile platform. The HPC braking system  10  disposed within the structure of each suspension and wheel assembly of the respective mobile platform is substantially identical, therefore, only a single HPC braking system  10  will be described herein. 
         [0022]    The HPC braking system  10  generally includes a rotor  14  mountable to a rotating wheel hub  18  of the respective suspension and wheel assembly, a caliper assembly  22  mountable to a stationarily portion of the suspension and wheel assembly, and a pair of brake pads  26  moveably disposed with caliper  22 . Each brake pad  26  includes a metal backing  26 A and a friction pad  26 B. A wheel  30  of the mobile platform is mounted to the rotating hub  18  such that the rotor  14  and wheel  30  are operably interconnected and rotate simultaneously, at the same rate of speed, as a single subassembly. The caliper assembly  22  includes at least one piston  34 , e.g., two opposing pistons  34 , that is/are structured and operable to expand to apply force to the brake pads  26 , as controlled by an operator of the mobile platform. Subsequently, the brake pads  26  are pushed against the rotor  14  to apply frictional force to the rotating rotor  14  to slow and/or stop rotation rotor  14  and the wheel  30  and hence the mobile platform. The HPC braking system  10  additionally includes a plurality of heat pipes  38  disposed within the rotor  14 , and/or the caliper  22 , and/or a metal backing  26 A of the brake pads  26 . 
         [0023]    Referring now to  FIGS. 2A and 2B , in various embodiments, heat pipes  38  can be disposed in the rotors  14  of a mobile platform braking system to assist in the cooling of the rotors  14  and thereby increase the efficiency, capability and reliability of the braking system. Particularly, the rotors  14  of a mobile platform braking system can get extremely hot during application of the brake pads  26  ( FIG. 1 ) to rotors  14 . The evaporator ends  38 A of the heat pipes  38  (the hot end, the end of the heat pipe that absorbs the heat) is disposed at the outside diameter of the rotor  14 , i.e., the same area where the brake pads  26  contact the rotor  14 . The condenser ends  38 B of the heat pipes  38  (the cool end, the end mounted to the heat exchanger) is disposed closer to the center of the rotor  14 . In various embodiments, the condenser ends  38 B extend through the center of the rotor  14 , through the hub  18  and are disposed within a heat sink  42  (referred to herein as the rotor heat sink  42 ) that extends through a center aperture in the respective wheel  30  such that the rotor heat sink  42  is exposed at an exterior side of the wheel  30 . In various embodiments, a finned heat exchanger  46  (referred to herein as the rotor heat exchanger  46 ) can be integrated with, i.e., thermally connected to, the rotor heat sink  42  and is disposed on the exterior side of the wheel  30 . The rotor heat exchanger  46  can be thermally connected to the rotor heat sink  42 , via one or more bolts. 
         [0024]    In operation, the heat is carried from the rotor  14  to the rotor heat sink  42  via the heat pipes  38 . Heat is transferred, via conduction, from the rotor  14  to the evaporator ends  38 A of the heat pipes  38 , then to the condenser ends  38 B of the heat pipes  38 , then, via conduction, to the rotor heat sink  42  permanently affixed to the condenser ends  38 B, and then, via conduction, to the rotor heat exchanger  46  directly connected, i.e., thermally connected, to the rotor heat sink  42 . In various implementations a thermal paste, e.g., thermal grease, can be applied between the rotor heat sink  42  and the rotor heat exchanger  46 . The heat is finally removed, i.e., dissipated, via the finned rotor heat exchanger  46 . The rotor heat exchanger  46  is disposed outboard, i.e., exteriorly, of the wheel  30 , and fully exposed to the air flow. 
         [0025]    Additionally, when configured as described above, circulation of the working fluid within the heat pipes  38 , i.e., circulation between the vapor state of the working fluid at the evaporator ends  38 A and the liquid state of the working fluid at the condenser ends  38 B is enhanced due to centrifugal force generated by rotation of the wheel  30  and rotor  14 . Particularly, the heat pipe working fluid is evaporated at the evaporator ends  38 A disposed at the radially outward portion of the rotor  14 . When the fluid evaporates, it moves radially inward to a radially inward to portion of the rotor  14  where the heat pipe condenser ends  38 B are attached to, or disposed within, the rotor heat sink  42 . When the rotor heat exchanger  46  cools the rotor heat sink  42  and thus the working fluid, the working fluid condenses from a gas back to a liquid. Then, centrifugal force via wheel  30  rotation helps to push the fluid back to the evaporator ends  38 A of the heat pipes  38  where it can be evaporated again. 
         [0026]    Referring now to  FIG. 3 , in various embodiments, heat pipes  38  can be disposed within the body  22 A of the caliper  22  to assist in cooling the caliper  22  and reducing the risk of failure thereof. Additionally, by having heat pipes  38  disposed within the caliper body  22 A, the caliper  22  and can be cooled, thereby reducing the amount of the heating of brake fluid used to operate the piston(s)  34 . This will minimize chances of the brake fluid boiling and any potential for the caliper piston(s)  34  to seize. 
         [0027]    Particularly, the evaporator ends  38 A of the heat pipes  38  are disposed within various portions of the caliper body  22 A. The condenser ends  38 B are is disposed with a heat sink  50  (referred to herein as the caliper heat sink  50 ). In various implementations, the caliper heat sink can be mounted to the caliper body  22 A. In various embodiments, a finned heat exchanger  54  (referred to herein as the caliper heat exchanger  54 ) can be attached to the caliper heat sink  50  to assisting in the cooling of the caliper heat sink  50  and hence, the cooling of the heat pipe condenser ends  38 B, and hence the cooling of the caliper body  22 A. Particularly, air flowing past the finned caliper heat exchanger  54  removes heat from the caliper heat exchanger  54 , which in turn will removes heat from the caliper heat sink  50 , which ultimately removes heat from the caliper body  22 A. 
         [0028]    Referring now to  FIG. 4 , in various embodiments, the evaporator ends  38 A of heat pipes can be disposed with the metal backing plate  26 A of at least one of the brake pads  26 . As described above, the brake pads  26  include the friction pads  26 B mounted to metal back plates  26 A. The condenser ends  38 B of the heat pipes  38  are disposed within one or more heat sinks  58  (referred to herein as brake pad heat sink(s)  58 ). In various embodiments, one or more heat exchangers  62  (referred to herein as brake pad heat exchanger(s)  62 ) can be thermally connected to the brake pad heat sink(s)  58 . Hence, heat from the friction pad(s)  26 B is transferred to the metal backing plate(s)  26 A and then to the brake pad heat sink(s)  58 , via the heat pipes  38 . Subsequently, the heat from the brake pad heat sink(s)  58  can be dissipated into the air via the brake pad heat exchanger(s)  62 . Hence, heat can be efficiently removed from the brake pad(s)  26 , particularly from the friction pad(s)  26 B via the heat pipes  38 . By removing heat from the friction pad(s)  26 B, the life of the friction pad(s)  26 B can be extended. Additionally, the amount of heat transferred from the brake pad(s)  26 , i.e., the friction pad(s)  26 B and backing plate(s)  26 A, to the caliper  22  is reduced. 
         [0029]    In various embodiments, addition to the condenser ends  38 B of the heat pipes  38  being disposed with the stationary caliper and brake pad heat sinks  50  and  58 , thermally conductive bonding straps (not shown) can be implemented to thermally connect major massive structural components of the respective mobile platform (e.g., the frame of a car) to the stationary caliper and brake pad heat sinks  50  and  58 . Accordingly, such major massive structural components can act as additional heat sinks and heat exchangers to increase the removal of heat from the caliper and brake pad heat sinks  50  and  58 , and hence from the braking system components. This will increase the overall cooling ability of the heat pipe brake system described herein. 
         [0030]    The description herein is merely exemplary in nature and, thus, variations that do not depart from the gist of that which is described are intended to be within the scope of the teachings. Such variations are not to be regarded as a departure from the spirit and scope of the teachings.