Patent Application
20130015023
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.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
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.
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.
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.
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.
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.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present teachings in any way.
Corresponding reference numerals indicate corresponding parts throughout the several views of drawings.
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.
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.
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.
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.
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.
Referring now to
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 26A and a friction pad 26B. 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 26A of the brake pads 26.
Referring now to
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 38A of the heat pipes 38, then to the condenser ends 38B of the heat pipes 38, then, via conduction, to the rotor heat sink 42 permanently affixed to the condenser ends 38B, 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.
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 38A and the liquid state of the working fluid at the condenser ends 38B 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 38A 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 38B 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 38A of the heat pipes 38 where it can be evaporated again.
Referring now to
Particularly, the evaporator ends 38A of the heat pipes 38 are disposed within various portions of the caliper body 22A. The condenser ends 38B 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 22A. 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 38B, and hence the cooling of the caliper body 22A. 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 22A.
Referring now to
In various embodiments, addition to the condenser ends 38B 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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 61507219 | Jul 2011 | US |
