Patent Application
20150233464
The present disclosure relates to a lubrication system for a gearbox.
Vehicle transmissions, such as power take off (PTO) transmissions, have shafts and gears which rotate in a housing which forms an oil sump so that the parts are adequately coated with lubricating oil while they rotate. Certain PTO transmissions have a pressurized lube system wherein sump oil level which is above the center of a shaft, and radial passages in the shaft pull oil through the shaft. Shaft and gear rotation causes the sump oil to be thrown away from the center of the transmission.
Lube fluid for a transmission can also be diverted from a tractor hydraulic system. But, this requires balancing lube systems, returning and controlling sump oil levels, and mixing oil with a gear box that is coupled to an implement, such as a planter. A transmission lubrication system can also include a small lube pump. However, this increases costs due to the additional parts, such as screens, lines and cooling requirements.
In a known small gear box, a needle bearing is sandwiched between two gears which rotate at lower and higher speeds, respectively. The gear box does not have any pressurized lube system or lube pump and will only use sump oil splash for cooling and lubrication. Due to the rotation of the gears, centripetal force will push sump oil away from the needle bearing and an adjacent ball bearing. It is desired to have a system which delivers lubrication oil to the bearings while working against the centrifugal force created by the rotating gears.
According to an aspect of the present disclosure, a gearbox has a housing which encloses a rotating gear and a volume which contains oil and pressurized air. The gear has a first surface exposed to the volume and a second surface exposed to the environment. A vent arrangement includes first and second passages formed in the gear. The second passage extends part way into the gear and has an outer end exposed to the second surface. The first passage extends radially outwardly from the second passage to the first surface. The second passage extends axially along a central axis of the gear. A check valve is mounted in the second passage and permits one-way flow of air from the volume to the environment.
Referring to
Referring to
A radially outwardly facing peripheral wall or annular surface 35 extends between surfaces 34 and 33, and surrounds the smaller diameter flange portion 31. An inner portion of smaller diameter flange portion 31 forms an annular rim 36 which projects generally axially from surface 34. An annular channel 38 is formed between the rim 36 and an axially inner end 32 of the hub 22. Annular peripheral surface 35 has a diameter which is larger than a diameter of the hub 22.
A plurality (preferably two) milled slots or grooves 40 and 42 extend radially inwardly from the wall 35, through smaller diameter flange portion 31, through the rim 36 and to the channel 38. The slots 40 and 42 may be curved or spiral shaped. Thus, the grooves 40 and 42 communicate the outer edge of smaller diameter flange portion 31 with the outer surface of hub 22. The outer ends of the groves 40 and 42 are forward of their inner ends with respect to the direction of rotation of the input gear 14. Thus, the slots 40 and 42 in the side of the input gear 14 scoop sump oil and direct it inwardly through the slots 40 and 42 towards the needle bearing 24.
Referring again to
The passage 56 in the output gear 18, which rotates at 6000 rpm, creates an under-pressure that helps pull oil through the needle bearing 24 and communicate oil to the ball bearing 26. Because of the differential in speed between the input gear 14 and the output gear 18, the passage 56 in output gear 18 will create more of an under-pressure than the slots 40 and 42 in the slower rotating (1000 rpm) input gear 14.
Thus, as the input gear 14 rotates, the spiral grooves 40 and 42 scoop lubrication oil from the interior of the housing 12 and impel this oil radially inwardly though the rim 36 and onto the outer surface of the hub 22. A pressure differential pulls this oil through the needle bearing 24, then through the passage 56 and through the bearing 26. The result is a system which using the rotation of the gears to create a pressure differential which sends lubricating sump oil to a buried needle bearing and ball bearing. Without these features, sump oil would normally be thrown outwardly and away from the centrally located bearings 24 and 26.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims.
