Heat pipe cooler for differential assembly
The present invention is directed to an apparatus to regulate and control the temperature of a differential axle assembly. A heat pipe is inserted though the axle housing with a portion submersed in axle lubricant. Cooling fins are preferably disposed on the heat pipe both in the submersed region of the heat pipe and a portion external the housing. The heat pipe is preferably secured to and substantially accommodated by a removable cover plate which is in turn secured to the housing. The heat pipe includes an evaporative working fluid to promote heat transfer between the lubricant and external environment.
The present application is a Continuation-in-part of U.S. application Ser. No. 10/143,752 filed on May 14, 2002 and is hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a heat pipe cooler for a differential assembly and particularly to an effective evaporative heat pipe assembly for transferring heat from the differential lubricant.
2. Description of Related Art
Typically axles are lubricated by a reservoir of oil in the sump which is circulated by the moving components. This is known as splash lubrication. The operating temperature of a splash lubricated axle assembly or other torque transmission device is generally dependent on the torque being transmitted, the ambient temperature, the speed of rotation and airflow over the device.
The operating temperature can be just above the ambient temperature to more than 200 degrees F. above ambient. Operating temperatures significantly above 250 degrees F. can begin to cause problems with the durability of the components in the axle as well as the lubricant itself. These temperatures are generally encountered at higher speeds and/or torques such as high speed highway driving or trailer towing. Therefore it is desirable to avoid these higher temperatures as much as possible. It is the intention of the present invention to minimize these high operating temperatures.
It is known to provide cooling conduits within an axle assembly in order to avoid high operating temperatures. These conduits are positioned about a majority of the differential assembly and contain a hydraulic fluid from another device which is capable of cooling the lubricant in the axle.
It is also known to have a differential assembly with a heat pipe having heat-absorbing portions extending through an oil sump as well as externally disposed heat-transmitting devices.
Additionally, it is know to have a heat pipe including a closed tube having a heat exchange medium comprised of a plurality of fins.
Thus, the aim underlying the present invention lies in providing an effective fluid lubricant cooling area that is readily utilizable, without significantly increasing the costs of production, the required space, and weight.
SUMMARY OF THE INVENTIONThe present invention is directed to a heat pipe cooler for an axle having a housing and removable cover. The heat pipe is secured to the cover and includes a heat-receiving zone, a heat-emitting zone and a working fluid, wherein the working fluid is evaporated in said heat-receiving zone and condensed in said heat-emitting zone to promote heat transfer between said lubricant and an external environment. The heat-receiving zone is at least partially immersed in the lubricant and contains heat-dissipating fins to promote heat transfer.
BRIEF DESCRIPTIONS OF THE DRAWINGSA better understanding of the present invention will be had when reference is made to the accompanying drawings, wherein identical parts are identified by identical reference numbers and wherein:
The present invention is directed to a heat pipe assembly for cooling lubricating fluid in a differential axle assembly. Preferably an evaporative heat pipe assembly is employed to increase the amount of heat transfer from the lubricant to the external environment. The assembly includes a hermetically sealed heat pipe containing a working fluid which is secured to a removable cover. The working fluid is selected to be vaporizable and condensable within the working temperatures of the differential assembly. The purpose of the heat pipe is to decrease the temperature of the lubricating fluid in the axle assembly. If the temperature of the lubricant gets to high, the lubricant will break down decreasing viscosity and its ability to effectively lubricate the gear assembly. The present invention effectively maintains the fluid lubricant at acceptable operating temperatures.
The heat pipe contains a working fluid such as water, or a sodium based fluid or other acceptable working fluids. In liquid form, the working fluid collects at the bottom of the heat pipe due to the force of gravity. The bottom of the heat pipe is submersed in the pool of axle lubricant and causes the working fluid to vaporize (latent heat of vaporization) thus reducing the temperature of the lubricating oil. The vapor then travels up to a condensing portion where the vapor condenses giving up heat to an external environment. The condensed liquid then returns to the evaporative portion where the cycle continues. The arrangement increases the amount of heat that can be transferred from the axle lubricant. The structure of the preferred embodiments of the present invention will no be explained.
The heat pipe assembly 3, 23 may be filled with a sodium-based working fluid. However, the specific fluid and concentrations of soluble elements may be chosen to maintain a temperature to which the heat is to be transferred which is largely dependent on the desired operating temperature of the lubricating oil such as not to exceed 200 degrees. While this present embodiment does not include a capillary structure or wick, one may be incorporated to the extent it enhances the evaporative cycle. The working fluid must also be chosen to be compatible with the material of the heat pipe to avoid undesirable reactions. For example, the heat pipe 3, 23 and cover 1, may be made of aluminum, copper or stainless steel or other suitable materials.
In the embodiments of
As previously indicated the specific materials may be selected based on the material specified for the cover plate and operating temperature of the lubricating fluid of the axle assembly. The heat pipe, or envelope may be composed of a durable material able to withstand environmental corrosion while being lightweight. Aluminum, copper and even some types of plastics may be employed. In the embodiments shown in
While the foregoing invention has been shown and described with reference to a preferred embodiment, it will be understood by those possessing skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. For example additional exemplary embodiments are shown in
Claims
1. An axle assembly for a motor vehicle, said axle assembly comprising:
- an axle housing provided with a supply of liquid lubricant;
- a cover removably secured to said housing; and
- at least one a sealed heat transfer pipe mounted to said cover and, said heat transfer pipe including an heat-receiving zone, a heat-emitting zone and a heat transfer fluid that flows there between, wherein said fluid being evaporated in said heat-receiving zone and condensed in said heat-emitting zone to promote heat transfer between said lubricant and an external environment; wherein said heat-receiving zone is at least partially immersed in said lubricant when said cover is secured to said housing.
2. The axle assembly according to claim 1, wherein said heat pipe is formed as a hollow loop-shaped pipe forming a continuous closed loop containing said heat transfer fluid.
3. The assembly according to claim 2, wherein said loop shaped pipe include at least two elongated portions, a first elongated portion being disposed within said housing an substantially submerged in said lubricant, said loop shaped heat pipe being cast within a bolstered rear portion of said cover.
4. The assembly according to claim 3, wherein a second elongated portion of said heat pipe is substantially embedded within a said bolstered portion of said cover, said bolstered portion having integrally formed fins directly exposed to said external environment.
5. The assembly according to claim 3, wherein said heat pipe extends through said bolstered portion and includes a second elongated disposed external said housing and directly exposed to said external environment.
6. The assembly according to claim 5, said heat pipe further includes a plurality of heat transfer fins affixed to said second elongated portion of said heat pipe.
7. The assembly according to claim 2 wherein said heat transfer fluid is sodium based solution.
8. An axle assembly for a motor vehicle, said axle assembly comprising:
- an axle housing containing gears to facilitate differential rotation between a pair of driven output gears, said housing containing a pool of liquid lubricant;
- a cover removably secured to said housing to provide access to said gears within said housing; and
- at least one a substantially sealed heat transfer pipe fixed to said cover and removable therewith relative to said housing, said heat transfer pipe including a heat-receiving zone, a heat-emitting zone and a working fluid, wherein said working fluid is evaporated in said heat-receiving zone and condensed in said heat-emitting zone to promote heat transfer between said lubricant and an external environment; wherein said heat-receiving zone is at least partially immersed in said lubricant when said cover is secured to said housing.
9. The assembly according to claim 8, wherein at least one a sealed heat transfer pipe includes a pair of heat pipes each containing separate heat-receiving zones and heat-emitting zones, said pair of heat pipes being interconnected by a set of common heat dissipating fins.
10. The assembly according to claim 9 wherein said set of common heat dissipating fins includes a first set disposed proximate said heat-receiving zone and being substantially immersed in said lubricant.
11. The assembly according to claim 19, said heat pipe extends external said housing to said external environment and said heat pipe further including a second set of common heat dissipating fins disposed proximate said heat-emitting zone in said external environment.
12. The assembly according to claim 8, wherein said cover contains an integrally formed reservoir in fluid communication with said pool of lubricant in said housing, said heat receiving zone of said heat pipe being substantially disposed within said reservoir.
13. The assembly according to claim 8, wherein said working fluid is a water based fluid.
14. The assembly according to claim 8, wherein said heat pipe further includes a wick member disposed within said heat pipe to promote transfer of working fluid from said heat receiving zone to said heat emitting zone through capillary action.
15. The assembly according to claim 14, wherein said wick member is formed of a metal screen.
Type: Application
Filed: Mar 8, 2004
Publication Date: Jun 16, 2005
Inventors: Assil Matti (Madison Heights, MI), Patricia McLeish (Rochester, MI), Michael Dougherty (Rochester Hills, MI), Robert Alward (Otisville, MI), Earl Irwin (Fort Wayne, IN)
Application Number: 10/794,419