WO2015130659A1 - Low loss lubrication system - Google Patents

Abstract

A low loss vehicle differential axle lubrication system has a differential housing having axle gearing, where a lubricant is void of anti-foaming agents, but may have foaming agents. The lubricant may be churned/aerated to form foam, turbulence, and bubbles. System members make mechanically interacting contact while immersed in the lubricant. Mechanically interacting contact is either mechanically meshing or loaded contact. The lubricant presents a lower magnitude drag force on each member. The system may have a beater, a gas pressure jet or nozzle, and/or a surface characteristic that generate the foam, turbulence, and bubbles. These elements contribute to better heat transfer, less wear on parts, and smoother operation of a differential with less loss of efficiency resulting from reducing oil drag. Consequently, the differential housing may be sealed without a circulating pump or external heat exchanger, thereby avoiding the addition of oil throughout the system's life.

Description

TITLE

LOW LOSS LUBRICATION SYSTEM

RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Serial No. 61/946,114, filed February 28, 2014, which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a lubrication system for a mechanical device. More particularly, the present invention relates to a low loss lubrication system for axle gearing.

BACKGROUND OF THE INVENTION

Typically, it is necessary to utilize a lubrication system for a mechanical device so as to smoothly operate the mechanical device and reduce wear therein, especially at an interface between mechanical contact surfaces thereon, where mechanically interacting (interlaced) or mechanically loaded (non-interlaced) contact is made. Therein, a lubricant or lubricant system comprises a mixture of oil in combination with at least one additive.

Examples of mechanically interacting contact are axle spur and helical gear teeth in a vehicle having contact surfaces that mesh continuously, wherein a lubricant comprising a viscous oil VO with a traditional anti-foaming agent AA disposed therein, splashes within a differential housing, thereby providing wear protection by the lubricant splashing onto and around the contact surfaces. Examples of mechanically loaded surface contacts are axle bearings and traction interfaces using continuously variable transmissions (CVT), wherein wear protection is provided by the viscous oil VO, with the traditional anti- foaming agent AA disposed therein, flowing onto and around the contact surfaces.

In both mechanically interacting contact and mechanically loaded surface contact cases, the lubricant also provides a means to transfer heat generated at the contact surfaces which further aids in a smooth operation and reduction of wear of the mating parts. Unfortunately, the mechanical device experiences power loss due to viscous drag resulting from the viscous oil resisting the motion of the rotating gears, which generates added heat that hinders operation and adds wear to mating parts.

Prior to the addition of the anti-foaming agent AA to conventional viscous oil VO, oil formulations available to oil splash systems (like system 10 in Fig. 1) and pump systems (not shown but common in the art) would build up foam F (see Figs. 2 and 3) due to motion of the various parts within a

differential housing. This foam F is conventionally considered to be an undesirable nuisance that piles up and spills out of a differential housing vent or chokes a pump (not shown but common in the art).

Fig. 1 illustrates the prior art mechanically interacting oil splash system 10 within, for example, a first differential axle housing 11 , where a first gear 12, having first contact surfaces 14, is rotationaliy driven by an unseen mechanical drive source, in a clockwise direction by an attached first shaft 16. In turn, a second gear 18, having second contact surfaces 20, is rotationaliy driven in a counter-clockwise direction by the first gear 12, by way of meshing contact at an interface 21 of the first and second contact surfaces 14, 20. Consequently, a second shaft 22, which is attached to the second gear 18, mechanically communicates rotational energy to, for example, a wheel of a vehicle (neither of which are shown but both common in the art). The oil splash system 10 is, however, immersed in the viscous oil VO with the conventional anti-foaming agent AA disposed therein, which presents a significant oil drag force FDI on the first gear 12.

Fig. 4 illustrates an example of an above-mentioned continuously variable transmission (CVT) that is designated as item 900, which is disclosed in U.S. Patent Application Publication 2014/0194242 and incorporated herein. Here, mechanically loaded contact is made on surfaces between non-interlaced balls 997 and three separate contact surfaces 995, 996, 999, upon which the balls 997 can rotate separately. Specifically, these surfaces are a disc input conical surface 995, a disc output conical surface 996, and idlers 999, which are coated with the conventional viscous oil VO having the anti-foaming agent AA disposed therein. As so described, this CVT transmission 900 would function as a splash system. It is, however, possible that the CVT transmission 900 could be utilized with a sump pump (not shown), wherein conventional lubricant, with VO and AA, would flow into the CVT 900, where the arrows are shown at the top of Fig. 4.

Such a sump pump system moves lubricant to contact surfaces in the absence of a splash system, and usually is applied so as to avoid completely immersing rotating parts. By scavenging oil from a sump pump, below the level of the rotating parts, and pumping the oil to contact areas, friction concerns are diminished somewhat by reducing viscous drag. Unfortunately new losses are introduced from the functioning of the sump pump, along with weight and cost added to the vehicle. Also, the pump lubrication system tends to be more sensitive to lost oil, through seals and leaks in the housing or by way of gaskets. This compares to a small amount of sensitivity to oil loss in a splash lube system, which therefore does not have much impact on splashing characteristics.

Unfortunately, oil loss in a pumped system can reduce the amount of oil available to flow through the pump. Less oil in a pump lubrication system makes it harder to absorb and disperse the heat from the contact surfaces. Thus, pump lubrication systems frequently require external coolers and large flows of oil to enable adequate heat exchange, while splash systems depend on a large amount of oil being spread around the housing and transferring heat to the metal that is in contact with ambient conditions outside of the splash lubrication system.

Further, oil loss in a pump lubrication system needs to be monitored due in part to the fact that current sump pump alternatives risk insufficient availability of oil in an effort to reduce power transmission losses from oil drag on the rotating parts, which in turn causes added wear on the rotating parts.

Hence, what is sought are lubrication systems that reduce oil loss, provide reduced wear at contact surfaces, reduce weight, improve heat transfer, reduce oil drag on parts, use less oil, and may not require sump pumping. As a result, better utilization of energy will be realized, while still providing sufficient availability of oil. SUMMARY OF THE INVENTION

A low loss lubrication system comprises a vehicle differential housing having a lubricant and a member disposed therein, where the member is selected from the group consisting of a beater, a gas pressure jet, a gas pressure nozzle, a surface characteristic, and any combination thereof.

Further objects and advantages of the present invention will be apparent from the following description and appended claims, reference being made to the accompanying drawings forming a part of a specification, wherein like reference characters designate corresponding parts of several views.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partial three dimensional cutaway view of a prior art oil splash lubrication system;

Fig. 2 is a partial three dimensional cutaway view of a first low loss lubrication system having beaters;

Fig. 3 is a partial three dimensional view of a second low loss lubrication system having an air pressure jet or nozzle with an optional surface

characteristic; and

Fig. 4 is a cutaway view of a prior art continuously variable transmission

(CVT).

DESCRIPTION OF THE INVENTION

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise.

In general, the present invention involves eliminating anti-foaming agents AA in differential housings, as illustrated in differential housings 31 , 51 of Figs. 2 and 3. Further, the present invention involves increased turbulence T2, T3, as also illustrated in splash lubrication systems 30, 50 of Figs. 2 and 3. An elimination of anti-foaming agents AA and an increase in turbulence T2, T3 result in forming a reduced drag oil RO.

Also, aerating, foaming, and forming bubbles in the lubricant in a differential housing contribute to forming reduced drag oil RO. Although these actions are similar, these actions are different. In the present invention, lubricant foaming F is analogous to soap bubbles, wherein lubricant bubbles 66, as seen in Fig. 3, are able to transport lubrication properties and heat using the lubricant in the walls of the bubbles 66. However, the bubbles 66 are mostly gas, which lower drag loss on rotating members, for example, fifth gear 52 shown in Fig. 3.

In order to generate bubbles 66, which are a temporary mixture of oil and air within the differential housing, the lubricant RO needs to be actively aerated. This aeration is a result of beating or adding air into the lubricant, even if conventional anti-foaming agents AA are present within the lubricant. As a result of the inducement of bubbles, oil drag loss is reduced within the differential housing.

On the other hand, it has been found in the present invention that it may be desirable to actually add foaming agents FA into the differential housing 30 in order to obtain a better balance between inducing air, foam F, and bubbles 66 within the lubricant.

Hence, the instant invention is directed to controlling a foaming behavior of the lubricant within the differential housing, by controlling the turbulence, bubbles, foam, anti-foaming agents AA, foaming agents FA, and aeration.

Splash lubrication systems exhibit robustness to lubricant loss over lubrication weight reduction characteristics of pumped systems. The above- mentioned bubble/aeration concepts are valuable because wear at the contact surfaces and heat transfer properties are maintained rather than improved.

It should be noted herein that a lubricant is to be taken to mean a combination of oil and additives, like anti-foaming additives or even a lack thereof, which have been found herein to affect oil drag force, heat transfer, and surface chemistry within the differential housing. Opposite pumped systems, the splash systems 30, 50 of the present invention work well. Also, the properties of reduced drag from bubbles 66 and aeration result in a reduction of the losses from rotating components in the reduced viscosity oil RO.

Accordingly, foam F is a fairly stable arrangement of lubricant combined with air, consisting of bubbles with walls of lubricant - somewhat like foam rubber. Formation of this foam F is the property that anti-foaming agents AA are supposedly to preventing. But herein, foam F is found to make a lubricant less viscous than the full-density lubricant, and serves the contact surfaces appropriately as long as it is delivered in adequate volume.

Aerated lubricant is very similar, but does not share the same bubble properties. Instead, mechanical turbulence or air jets create a combination of air and lubricant that essentially has the same lubricant properties with less viscosity, and therefore less drag.

Specifically, low loss lubrication systems 30, 50, which respectively are depicted in Figs. 2 and 3, comprise vehicle differential housings 31 , 51 and have a reduced drag lubricant RO disposed therein, wherein the lubricant RO is void of anti-foaming agents AA, like that found in prior art Fig. 1. In each of these housings 31 , 51 there is respectively disposed at least one member 32, 38, 52, 58.

Further, the first low loss splash lubrication system 30 of Fig. 2

comprises the differential axle housing 31 and a third gear 32, having third contact surfaces 34, that is rotationally driven by an unseen mechanical drive source, in a clockwise direction by way of an attached third shaft 36. In turn, the fourth gear 38, having fourth contact surfaces 40, is rotationally driven in a counter-clockwise direction by the third gear 32, by way of meshing mechanical contact at an interface 41 of the third and fourth contact surfaces 34, 40.

Consequently, a fourth shaft 42, which is attached to the fourth gear 38, mechanically communicates rotational energy to, for example, a vehicle wheel (not shown but common in the art).

Immersing the first low loss lubrication system 30 in the lubricant RO without any anti-foaming agents AA allows for foam F to be formed under normal operating conditions. As a consequence of the formation of foam F, it has been found that the lubricant RO exhibits reduced drag. In addition, the lubricant may be aerated, wherein an oil drag force FD2 is presented to the third gear 32. Consequently, the magnitude of this oil drag force FD2 is significantly less than the oil drag force FDI of an equivalently structured oil splash system like that shown in prior art Fig. 1.

The first low loss lubrication system 30 may also comprise at least one rotating beater 44 (i.e., for further churning, aerating, and foaming with minimal creation of shear forces) disposed within the reduced drag oil RO, whereby the beater 44 induces more turbulence T2 into the reduced drag oil RO than an equivalently structured prior art oil splash system, like that shown in prior art Fig. 1.

Also shown in Fig. 2 is that the beaters 44 may be structured having a mechanically powered shaft with one or more arcuate blades attached at an end thereof. Hence, the shaft causes the blades to rotate (as shown by the rotating arrows above the beaters 44), which in turn causes the reduced drag oil RO to churn and form turbulence T2, as seen in Fig. 2. These arcuate blades could be similar to the beater blades associated with mixer blades used in food preparation. However, any shaped beater that adds turbulence to the reduced drag oil RO can be applied to the instant invention 30. In addition to the creation of the foam F and bubbles 66, it has been found that the more turbulence that is induced into this lubrication system 30, the lower the viscosity of the lubricant that in turn better coats the surfaces that come in contact with each other, thereby lowering wear of the parts.

Pictorially, the turbulence T2 throughout Fig. 2 is shown higher than the turbulence Ti of the prior art splash system 10, and the turbulence T2 shown at the top of Fig. 2 is higher on the left side than on the top of the right side, in order to further indicate greater turbulence. Greater turbulence will also result, for example, from lubrication formulations that are void of anti-foaming agents AA, because anti-foaming agents are added to prior art lubricants to keep them settled so that the lubricant moves quickly through pumps (not shown), where aeration is considered a problem. It has been found in the present invention that the addition of foaming additives FA may be utilized in order to create a balance between turbulence, bubbles, foam, and specific viscosity so as to result in the best coating of the oil RO upon the contact surfaces 34, 40.

The second low loss lubrication system 50, which is illustrated in Fig. 3, comprises the differential axle housing 51 and the fifth gear 52, having fifth contact surfaces 54, and is shown rotationally driven by an unseen mechanical drive source, in a clockwise direction by an attached fifth shaft 56. In turn, the sixth gear 58, having sixth contact surfaces 60, is rotationally driven in a counter-clockwise direction by the fifth gear 52, by way of meshing contact at an interface 61 between the fifth and sixth contact surfaces 54, 60.

Consequently, a sixth shaft 62, which is attached to the sixth gear 58, mechanically communicates rotational energy to, for example, a vehicle wheel (not shown but common in the art).

The second low loss lubrication system 50 also comprises a gas pressure jet or nozzle 64 (for example, a slow leak of air, at 1 psi above ambient) disposed within the reduced drag oil RO which induces bubbles 66 and more turbulence T3 into the reduced drag oil RO than that of an

equivalently structured prior art lubricant splash system. Pictorially, the turbulence T3 throughout Fig. 3 is shown higher than the turbulence Ti of the splash system 10, and the turbulence T3 at the top left side of Fig. 3 is shown higher than that on the top of the right side, in order to further indicate greater turbulence.

Also depicted in Fig. 3 is an optional surface characteristic 70, for example a blade, attached to the sixth gear 58 that induces more turbulence T3 within the housing 51. Even though the surface characteristic 70 is attached on the sixth gear 58 within the housing 51 of the second low loss lubricant system 50, it is possible to attach the surface characteristic 70 to any item (e.g., a rotating item or a nearby item to a rotating item) that can induce turbulence to a lubrication system, for example, the systems 10, 30, 50. Also, the shape and size of a surface characteristic can be different from the blade 70 shown in Fig. 3, as long as it does not physically interfere with the functioning of the

lubrication system to which the surface characteristic 70 has been added. Although not shown, the surface characteristic 70 could be of an extending ring shaped item attached to the inside of the vehicle differential housing, or a small distortion on the edge of gear teeth themselves that would not interfere with the operation of the meshing gears, like gears 34, 40, 54, 60. These surface characteristics would be coupled with the reduced drag oil RO that is void of the anti-foaming agent AA.

Splash lubrication systems, including the reduced drag systems 30, 50 of the present invention, have fewer moving parts and leak sources than the sump pump systems that are mentioned in the Background section above, thereby having fewer incidences of oil loss. Also, by utilizing the reduced drag oil RO (i.e., lubricant) in the present invention, the aeration and foaming of the oil allows a smaller amount of oil to make better heat transfer at the interfaces 41 , 61 and better heat transfer where the oil is in contact with the housings 31 , 51 due to aeration.

The low loss lubrication systems 30, 50 may have any combination of the beaters 44, the gas pressure jet or the nozzle 64, the surface characteristic 70, and the reduced drag oil RO, where foam F, greater turbulence T2, T3, and bubbles 66 are produced which results in reduced oil loss, reduced wear at contact surfaces 34, 40, 54, 60, reduced weight and oil drag FD2, F D3 on parts that results in better utilization of energy, while still providing sufficient availability of the oil RO. Although foaming is detrimental to pump applications because the foam does not pump well with air in it, the above-mentioned foam F creates less drag FD on rotating parts, versus non-aerated oil.

In place of each of the above-stated embodiments that has a

mechanically interacting (interlaced) drive gear or driven gear, embodiments comprising mechanically loaded (non-interlaced) drive and driven gears, cones, belts, and devices utilizing magnetics, ratchets, hydrostatics, radial rollers, v- belt drives, planetary action, and pulleys, to name a few, may be realized.

Anyone of these embodiments may have the added feature of a surface characteristic, which would further reduce drag within the vehicle differential housing. In general, the low loss lubrication system comprises a vehicle differential housing having a lubricant and at least a first member disposed therein, wherein the lubricant is void of anti-foaming agents AA. The low loss lubrication system further comprises a second member disposed therein, where each of the two members are movable parts and each has a contact surface, wherein the contact surfaces make meshing mechanical contact or

mechanically loaded contact at an interface therebetween. These two moving members are immersed in the lubricant, which may be a reduced drag oil RO. It is also possible to operate the low loss lubrication systems as disclosed above with the viscous oil VO, while comprising an item selected from a group consisting of a beater, a gas pressure jet, a gas pressure nozzle, a surface characteristic, and any combination thereof.

In fact, the benefits of low loss lubricant can be applied to the prior art CVT 900 system of Fig. 4, where the viscous oil VO is replaced with anti- foaming agent AA with reduced drag oil RO, foam F is produced, bubbles 66 are produced, and foaming agents FA are included in the oil RO.

In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that the invention may be practiced otherwise than specifically explained and illustrated without departing from its spirit or scope.

Claims

WHAT IS CLAIMED IS:

1. A low loss lubrication system, comprising:

a vehicle differential housing having a lubricant disposed therein; and a first member selected from a group consisting of a beater, a gas pressure jet, a gas pressure nozzle, a surface characteristic, and any combination thereof.

2. The low loss lubrication system of claim 1 , wherein the lubricant is void of anti-foaming agents.

3. The low loss lubrication system of claim 1 , further comprising second and third members disposed therein having at least one mechanical contact surface at an interface therebetween.

4. The low loss lubrication system of claim 3, wherein the interface is in mechanically interacting contact or mechanically loaded contact.

5. The low loss lubrication system of claim 4, wherein the mechanically interacting contact at the interface comprises two gears having meshing mechanical contact.

6. The low loss lubrication system of claim 4, wherein the mechanically interacting contact at the interface comprises a continuously variable

transmission having mechanically loaded contact.

7. The low loss lubrication system of claim 3, wherein the second and third members are immersed in the lubricant having aerated bubbles.

8. The low loss lubrication system of claim 3, wherein the second and third members are immersed in the lubricant having foam.

9. The low loss lubrication system of claim 3, wherein the second member is a drive gear and the third member is a driven gear.

10. The low loss lubrication system of claim 9, wherein the lubricant is void of anti-foaming agents.

11. The low loss lubrication system of claim 3, wherein the surface characteristic comprises a blade.

12. The low loss lubrication system of claim 11 , wherein the blade is of a gear tooth shape.

13. The low loss lubrication system of claim 12, wherein the blade is attached to the driven gear.

14. The low loss lubrication system of claim 3, wherein the gas pressure nozzle comprises a leak of 1 psi above ambient air pressure.

15. The low loss lubrication system of claim 3, wherein the low loss lubrication system is a non-sump pump low loss lubrication system.

16. The low loss lubrication system of claim 3, wherein the second and third members comprise axle gearing.

17. The low loss lubrication system of claim 16, wherein the axle gearing comprises an axle spur and helical gear teeth in a vehicle.

18. The low loss lubrication system of claim 1 , wherein the lubricant comprises a foaming agent.