WO2001031229A2

WO2001031229A2 - Method and apparatus for adjusting lubricant temperature within a gearbox

Info

Publication number: WO2001031229A2
Application number: PCT/US2000/041563
Authority: WO
Inventors: John M. Hawkins
Original assignee: Rolls-Royce Corporation
Priority date: 1999-10-25
Filing date: 2000-10-25
Publication date: 2001-05-03
Also published as: WO2001031229A3

Abstract

A lubrication system (50) adapted for use in a mechanical gearbox (24) that includes multiple gear meshes and bearing locations. The lubrication system (50) includes multiple heat exchangers (51, 52) that are suitable to tailor the temperature of the lubricant to a predetermined value for the gear meshes and bearing locations. In one form a first heat exchanger (52) adjusts the temperature of a quantity of the lubricant to a first predetermined value and a second heat exchanger (51) adjusts the temperature of a quantity of the lubricant to a second predetermined value. The lubricant after exiting the respective heat exchanger at the first predetermined value and/or the second predetermined value is delivered to the respective bearing or gear mesh to lubricate and cool the component.

Description

METHOD AND APPARATUS FOR ADJUSTING LUBRICANT

TEMPERATURE WITHIN A GEARBOX

RELATED APPLICATIONS

The present application claims the benefit of United States Provisional Patent Application serial number 60/161,286 filed October 25, 1999. United States Provisional Application 60/161,286 is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of lubrication systems. More particularly, one embodiment of the present invention contemplates a gearbox lubrication system wherein the lubricant temperature utilized within the gearbox is adjusted to different temperatures prior to delivery to a specific gear mesh point and/or bearing. The present invention was developed for gas turbine engine applications, however certain applications may be outside of this field. Many gas turbine engines utilize a mechanical gearbox within their power train components to deliver power to a motive device. The mechanical efficiency of gearboxes has been the subject of extensive work by engineers in order to extend the performance envelope of aircraft. It is widely understood that the aircraft's range, payload and operating ceiling can be increased if the efficiency of the mechanical gearbox is increased. The power loss in the mechanical gearbox is a function of many parameters including sliding losses, windage losses, lubricant churning losses, rolling traction losses and material hysteretic losses. The sliding friction losses in the gears and bearings account for a large portion of the power loss.

Most gearboxes include a lubrication system designed and developed to deliver a lubricant to the gear meshes and bearings within the gearbox. Prior lubrication systems typically cool the lubricant to a single uniform temperature and this uniform temperature lubricant is then delivered to cool and lubricate the gear meshes and bearings. A conventional design practice was to cool the lubricant to the requirement of the most critical gear mesh or bearing. This practice results in the lubricant being too cool for optimum efficiency for many of the other gear meshes and bearings within the gearbox. There are a variety of lubrication systems that have been conceived of over the years. While these prior lubrication systems are steps in the right direction the need for additional improvement still remains. The present invention satisfies this need in a novel and unobvious way.

SUMMARY OF THE INVENTION

One form of the present invention contemplates a lubrication system in which the lubricant temperature is adjusted to meet the individual parameters associated with gear mesh points and/or the bearing requirements of a gearbox.

Another form of the present invention contemplates a method for lubricating components within a gearbox. The method, comprises: adjusting the temperature of a first quantity of the lubricant to a first temperature; delivering at least a portion of the first quantity of the lubricant at the first temperature to a first location within the gearbox; changing the temperature of a second quantity of the lubricant to a second temperature; and, delivering at least a portion of the second quantity of the lubricant at the second temperature to a second location within the gearbox.

Another form of the present invention contemplates a system, comprising: a mechanical housing having a plurality of mesh points therein, and the mechanical housing is adapted to hold a lubricant; a first lubricant heat exchanger in heat transfer relationship with a first quantity of lubricant, the first lubricant heat exchanger is adapted to change the temperature of the first quantity of lubricant to a first temperature, wherein at least a portion of the first quantity of lubricant exits the first heat exchanger at the first temperature and is delivered to a first one of the plurality of mesh points within the mechanical housing; and, a second lubricant heat exchanger in heat transfer relationship with a second quantity of lubricant, the second lubricant heat exchanger is adapted to change the temperature of the second quantity of lubricant to a second temperature, wherein at least a portion of the second quantity of lubricant exits the second heat exchanger at the second temperature and is delivered to a second one of the plurality of mesh points within the mechanical housing.

In yet another form the present invention contemplates a gearbox, comprising: a mechanical housing adapted to have a lubricant therein; a first gear set positioned within the mechanical housing, the first gear set defines a first gear mesh; a second gear set positioned within the mechanical housing, the second gear set defines a second gear mesh; a first heat exchanger having a first lubricant inlet and a first lubricant outlet, the first lubricant inlet is in fluid communication with the mechanical housing and the lubricant exiting the first lubricant outlet has had its temperature changed to a first predetermined temperature by the first heat exchanger; a second heat exchanger having a second lubricant inlet and a second lubricant outlet, the second lubricant inlet is in fluid communication with the mechanical housing and the lubricant exiting the second lubricant outlet has had its temperature changed to a second predetermined temperature by the second heat exchanger; and, a lubricant delivery system within the mechanical housing, the lubricant delivery system has a first portion that receives lubricant at the first predetermined temperature from the first outlet and delivers to the first gear mesh and a second portion that receives lubricant at the second predetermined temperature from the second outlet and delivers to the second gear mesh.

In yet another form the present invention contemplates a gearbox, comprising: a mechanical housing adapted to have a lubricant therein; a first gear set positioned within the mechanical housing, the first gear set defines a first gear mesh; a second gear set positioned within the mechanical housing, the second gear set defines a second gear mesh; a first heat exchanger having a first lubricant inlet and a first lubricant outlet, the first lubricant inlet is in fluid communication with the mechanical housing and the lubricant exiting the first lubricant outlet has been cooled to a first predetermined temperature by the first heat exchanger; a second heat exchanger having a second lubricant inlet and a second lubricant outlet, the second lubricant inlet is in fluid communication with the first lubricant outlet and adapted to receive a portion of the lubricant cooled to the first predetermined temperature, and the lubricant exiting the second lubricant outlet has been cooled to a second predetermined temperature by the second heat exchanger; and, a lubricant delivery system in fluid communication with the mechanical housing, the lubricant delivery system has a first portion that receives lubricant at the first predetermined temperature from the first outlet and delivers to the first gear mesh and a second portion that receives lubricant at the second predetermined temperature from the second outlet and delivers to the second gear mesh. One object of the present invention is to provide a unique system for adjusting lubricant temperature within a gearbox.

Related objects and advantages of the present invention will be apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative view of a typical helicopter including a lubrication temperature adjustment system of the present invention.

FIG. 2 is a block diagram of a gas turbine engine coupled to a gearbox including a lubrication adjustment system of the present invention.

FIG. 3 is a schematic illustration of one embodiment of the lubrication adjustment system of the present invention.

FIG. 4 is a schematic illustration of an alternate embodiment of the lubrication adjustment system of the present invention. FIG. 5 is a sectional view of a gearbox including a planet output gear set.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

With reference to FIG. 1 , there is illustrated a side elevational view of a helicopter 20. The helicopter 20 includes a main rotor 21 and a tail rotor 22. A gas turbine engine propulsion system 23 drives the rotors 21 and 22. The present invention is applicable to many fields and has particular application in the aircraft industry. The term aircraft is generic and includes helicopters, airplanes, missiles, unmanned space devices and other substantially similar devices. With reference to FIG 2, there is illustrated a block diagram of the gas turbine engine 23 coupled to a gear box 24. The gas turbine engine includes a compressor 25, a combustor 26 and a turbine 27. It is important to realize that there are a multitude of ways in which the gas turbine engine components can be linked together. Additional compressors and turbines could be added with intercoolers connecting between the compressors and reheat combustion chambers can be added between the turbines. The present invention is not intended to be limited to a specific gas turbine engine and further details relating to gas turbine engines will not be provided as one of ordinary skill in the art will be familiar with general gas turbine engine technology.

With reference to FIG. 3 there is illustrated a schematic representation of one embodiment of a lubrication temperature adjustment system 40. The lubrication temperature adjustment system is designed to deliver a lubricant at a predetermined temperature to each of a plurality of points within the gearbox 24. The plurality of points is intended to include gear sets, bearings, and similar mechanical structures requiring lubrication and/or cooling by the lubricant within the gearbox housing. The lubrication temperature adjustment system will be described with reference to a gearbox having two gear mesh points, however, the present invention is useable with any number of mechanical points and is not intended herein to be limited to a gearbox having two gear mesh points. Further, while the description is set forth herein in terms of gear mesh points it is understood that the present inventions are equally applicable to other mechanical components requiring lubrication and/or cooling by the lubricant within the gearbox housing.

The lubricant temperature adjustment system 40 includes a primary lubricant temperature adjuster 28 which receives a quantity of lubricant from within the gearbox 24. The lubricant delivered through input 41 into the primary lubricant temperature adjuster 28 has an initial temperature and the primary lubricant temperature adjuster 28 functions to adjust the temperature of the lubricant to a predetermined temperature prior to delivery at the gear mesh point one. A portion of the lubricant adjusted within and output from the primary lubricant temperature adjuster 28 is delivered to a secondary lubricant temperature adjuster 29 via input 43. The primary lubricant temperature adjuster 28 and the secondary lubricant temperature adjuster 29 are in fluid communication. The second lubricant temperature adjuster 29 adjusts the temperature of the lubricant entering through input 42 to a predetermined temperature for gear mesh point 2.

In one embodiment, the primary lubricant temperature adjuster 28 includes a cooler. The cooler includes a heat exchanger functioning to transfer energy between the lubricant and a cooling media. The cooling media includes but is not limited to air, and/or fuel. The secondary lubricant temperature adjuster 29 is connected in series with the primary lubricant temperature adjuster 28 and receives a portion of the lubricant from the primary adjuster 28. The secondary lubricant temperature adjuster 29 in one form includes a cooler, and more preferably is a heat exchanger functioning to transfer energy between the lubricant and a cooling media. The cooling media includes but is not limited to air, and/or fuel. The primary lubricant temperature adjuster 28 and the secondary lubricant temperature adjuster 29 are intended herein not to be limited to a specific type of cooler. Further, the present invention contemplates in one embodiment active feedback control to monitor and adjust the temperature of the lubricant being cooled by the heat exchangers. With reference to FIG. 4 there is illustrated an alternative embodiment of a lubricant temperature adjustment system 50. The lubricant temperature adjustment system 50 is substantially similar to the lubricant temperature adjustment system 40 discussed previously, however, the secondary lubricant temperature adjuster 51 is not coupled in series with the primary lubricant temperature adjuster 52. Each of the lubricant temperature adjusters 51 and 52 adjust the temperature of the input lubricant to a predetermined temperature necessary for the specific gear mesh point. The features and description of the primary lubricant temperature adjuster 52 and secondary lubricant temperature adjuster 51 are substantially similar to the description regarding FIG. 3. In one form the temperature adjustment of the lubricant by the primary lubricant adjuster 52 and the secondary lubricant adjuster 51 is taking place in a substantially parallel process.

In another form, the lubrication temperature adjustment system includes a localized heater to heat the lubricant prior to delivery to a specific gear mesh point. One embodiment of the localized heater includes a coil type heater. However, the present invention includes heating the lubricant prior to delivery to the individual gear mesh points by other techniques, including, but not limited to mixing with uncooled oil. The localized heater can form part of a system that also cools lubricant for delivery to other points within the gearbox. In one form of the present invention, a specific gear mesh or bearing has a critical lubrication temperature necessary in order to have a sufficient lubricant film thicknesses and the remaining bearing and/or gear meshes have a lower lubricant film thickness requirement. A portion of the lubricant within the gearbox passes through the primary lubricant temperature adjuster and its temperature is changed to a temperature suitable for all other mesh points and/or bearings except for the critical mesh point. A portion of the lubricant exiting from the primary temperature adjuster passes through the secondary lubricant temperature adjuster and the temperature of the lubricant is adjusted to the required temperature for the critical mesh point. In the embodiment of FIG. 4, the lubricant is not processed in series and each lubricant temperature adjuster changes the temperature of the lubricant to the temperature needed for delivery to a specific set site within the gearbox.

In order to aid the reader in understanding the present invention an example of a transmission 100 having a planet output gear set 101 will be described with the aid of FIG. 5. It is understood herein that the present invention is not limited to the design of FIG. 5 and other gearboxes and transmissions are contemplated herein. The phrases gearbox and transmission will be used interchangeably unless specifically stated to the contrary and are intended to have a broad meaning and are not limited to the specific types of examples set forth in the description. The planet gear set is the critical mesh point from a lubrication standpoint. We will suppose that the planet output gear set mesh point needs a lubricant-in temperature of 180 degrees Fahrenheit to have sufficient lubricant film thicknesses, but all other points within the transmission need a lubrication-in temperature of 250 degrees Fahrenheit. The lubricant is routed through a cooler such that the lubrication-in temperature from the housing is about 250 degrees Fahrenheit for all the bearings and/or gear mesh points except the planet output gear set. The lubricant for the planet output gear set is routed through a supplementary cooler and cooled to 180 degrees Fahrenheit. While the example only sets forth the need for two predetermined lubrication temperatures, it is understood herein that the present invention is not limited to the developing of two different lubrication temperatures and, a plurality of different lubrication temperatures are contemplated herein. One technique to adjust the temperatures is with a plurality of coolers and/or heaters.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the prefeπed embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. In reading the claims it is intended that when words such as "a", "an", "at least one", "at least a portion" are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

What is claimed:

1. A method for lubricating components within a gearbox with a lubricant, comprising: adjusting the temperature of a first quantity of the lubricant to a first temperature; delivering at least a portion of the first quantity of the lubricant at the first temperature to a first location within the gearbox; changing the temperature of a second quantity of the lubricant to a second temperature; and delivering at least a portion of the second quantity of the lubricant at the second temperature to a second location within the gearbox.

2. The method of claim 1, wherein the first location is one of a gear mesh and a bearing and the second location is one of a gear mesh and a bearing.

3. The method of claim 1, which further includes drawing the first quantity of lubricant and the second quantity of lubricant from a common reservoir.

4. The method of claim 1 , wherein the initial temperature of the second quantity of lubricant is the first temperature, and wherein said changing occurs sequentially after said adjusting.

5. The method of claim 1, wherein the first temperature and the second temperature are not equal.

6. The method of claim 1, which further includes altering the temperature of a third quantity of lubricant to a third temperature, and delivering at least a portion of the third quantity of lubricant at the third temperature to a third location within the gearbox.

7. The method of claim 1, wherein the lubricant after said delivering returns to a common collection point.

8. The method of claim 1 wherein said adjusting and said changing affect the viscosity of the lubricant.

9. The method of claim 1, wherein the first location is representative of the most critical lubrication requirement within the gearbox, and wherein the first temperature is the predetermined temperature necessary for the lubricant to provide the cooling and lubrication necessary for the most critical lubrication requirement.

10. The method of claim 1, wherein said adjusting and said changing involve cooling the lubricant prior to said delivering.

11. The method of claim 1 , wherein at least one of said adjusting and said changing involves heating the lubricant prior to said delivering.

12. The method of claim 1, wherein the second quantity of lubricant at the second temperature is thicker than the first quantity of lubricant at the first temperature.

13. A system, comprising a mechanical housing having a plurality of mesh points therein, said mechanical housing adapted to hold a lubricant; a first lubricant heat exchanger in heat transfer relationship with a first quantity of lubricant, said first lubricant heat exchanger is adapted to change the temperature of the first quantity of lubricant to a first temperature, wherein at least a portion of the first quantity of lubricant exiting the first heat exchanger at said first temperature and is delivered to a first one of said plurality of mesh points within said mechanical housing; and a second lubricant heat exchanger in heat transfer relationship with a second quantity of lubricant, said second lubricant heat exchanger is adapted to change the temperature of the second quantity of lubricant to a second temperature, wherein at least a portion of the second quantity of lubricant exiting the second heat exchanger at said second temperature is delivered to a second one of said plurality of mesh points within said mechanical housing.

14. The system of claim 13, wherein said plurality of mesh points includes bearing locations and gear meshes.

15. The system of claim 13, wherein the first lubricant heat exchanger and the second lubricant heat exchanger are in serial flow communication.

16. The system of claim 13, wherein the first lubricant heat exchanger and the second lubricant heat exchanger are in parallel flow communication.

17. The system of claim 13, wherein the first temperature and the second temperature are unequal.

18. The system of claim 13 wherein one of the lubricant heat exchangers is a cooler and the other of the lubricant heat exchangers is a heater.

19. The system of claim 13, which further includes a plurality of additional lubricant heat exchangers in heat transfer relationships with quantities of lubricant, each of said plurality of additional heat exchangers is adapted to change the temperature of one of the quantities of lubricant to a predetermined temperature, wherein at least a portion of each of the quantities of lubricant exiting the respective one of said plurality of lubricant heat exchangers at said predetermined temperature is delivered to one of said plurality of mesh points within said mechanical housing.

20. A gear box, comprising a mechanical housing adapted to have a lubricant therein; a first gear set positioned within said mechanical housing, said first gear set defines a first gear mesh; a second gear set positioned within said mechanical housing, said second gear set defines a second gear mesh; a first heat exchanger having a first lubricant inlet and a first lubricant outlet, said first lubricant inlet is in fluid communication with said mechanical housing and the lubricant exiting said first lubricant outlet has had it's temperature changed to a first predetermined temperature by said first heat exchanger; a second heat exchanger having a second lubricant inlet and a second lubricant outlet, said second lubricant inlet is in fluid communication with said mechanical housing and the lubricant exiting said second lubricant outlet has had it's temperature changed to a second predetermined temperature by said second heat exchanger; and a lubricant delivery system within said mechanical housing, said lubricant delivery system has a first portion that receives lubricant at said first predetermined temperature from said first outlet and delivers to said first gear mesh and a second portion that receives lubricant at said second predetermined temperature from said second outlet and delivers to said second gear mesh.

21. A gearbox, comprising a mechanical housing adapted to have a lubricant therein; a first gear set positioned within said mechanical housing, said first gear set defines a first gear mesh; a second gear set positioned within said mechanical housing, said second gear set defines a second gear mesh; a first heat exchanger having a first lubricant inlet and a first lubricant outlet, said first lubricant inlet is in fluid communication with said mechanical housing and the lubricant exiting said first lubricant outlet has been cooled to a first predetermined temperature by said first heat exchanger; a second heat exchanger having a second lubricant inlet and a second lubricant outlet, said second lubricant inlet is in fluid communication with said first lubricant outlet and adapted to receive a portion of the lubricant cooled to said first predetermined temperature, and the lubricant exiting said second lubricant outlet has been cooled to a second predetermined temperature by said second heat exchanger; and a lubricant delivery system in fluid communication with said mechanical housing, said lubricant delivery system has a first portion that receives lubricant at said first predetermined temperature from said first outlet and delivers to said first gear mesh and a second portion that receives lubricant at said second predetermined temperature from said second outlet and delivers to said second gear mesh.