GB2042650A

GB2042650A - Gear Box with Lubricant Evacuation System

Info

Publication number: GB2042650A
Application number: GB7940529A
Authority: GB
Original assignee: Deere and Co
Current assignee: Deere and Co
Priority date: 1978-11-24
Filing date: 1979-11-23
Publication date: 1980-09-24
Also published as: GB2042650B; FR2442398B1; ES486269A1; DE2946293C2; DE2946293A1; IT1164143B; IT7950871A0; FR2442398A1

Abstract

A gear housing encloses a gear train and contains an integral oil reservoir 70 which keeps the quiescent oil level above the bottom gears 30 and 32 in the train and includes a passageway 62 with a bottom opening enshrouding the gear 32 at the bottom of the housing. Rotation of the bottom gear above a certain tooth tip velocity causes viscously dragged oil to be directed by a lip 64 on the passageway into the passageway and vertically upward to an opening 68 which allows the oil to drop into a dammed reservoir 76 from which part feeds back to the gear train while the majority of the oil returns over the dam 78 to the reservoir. Thus, when excessive oil is evacuated from the gear train, the oil will cascade over the dam to the reservoir so as to provide a predetermined maximum volume of oil gravity-fed back to the gear train. <IMAGE>

Description

SPECIFICATION Gear Box with Lubricant Evacuation System The present invention relates to a gear box with a lubricant evacuation system which requires no additional parts.

In the past, there has always been a substantial power loss due to excessive oil turbulence produced when a gear in a gear train is partically or completely submerged in oil. In order to alleviate this problem, it was often the practice to provide a gear pump operating off the power transmitting gears to pump oil from the gear housing when power was being transmitted. With this solution came the attendant problems of increased costs and decreased reliability due to the additional parts required for the gear pump.

Further, in most systems, the oil was generally fed directly back to the gear train, causing a shortage of oil at slow speeds and an excess of oil and turbulence at higher speeds.

The present invention provides a gear box with a lubricant evacuation system, comprising a train of gears stacked one upon the other in a housing in communication with a lubricant reservoir, and a passageway in the housing with an upper opening leading to the reservoir and a bottom adjacent the bottom gear of the train in an arrangement such that, at a sufficient speed of rotation of the bottom gear in a predetermined sense, oil is forced by teeth of the bottom gear up the passageway and hence to the reservoir. The passageway can supply the lubricant to a gravityfeed system in the main reservoir area. The housing may further be provided with bypass passages proximate one or more mesh areas of the gears to allow displaced lubricant to bypass the mesh area and thus prevent excessive 'lubricant at the mesh areas.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: Fig 1 is a side view, partially in section, of a gear box embodying the present invention; and Fig 2 is a front view of Fig 1 with certain parts removed for clarity.

Referring now to Fig 1, a gear box 10 includes a gear housing 12 made up of a case 14 and cover 16.

The gear housing 12 encloses a gear space 13 which contains a drive gear train 1 8 which is used to transmit power from an input shaft 24 to an output shaft 52, the shaft 24 being driven from a main drive shaft 20 by a planetary gear set 22.

The input shaft 24 is integral with an input gear 26 of the drive gear train 18.

Referring now to Fig 2, it may be seen that the gear train 18 consists of the input gear 26, an intermediate gear 28, an intermediate gear 30, and the output gear 32.

Referring to Fig 1 again, the input gear 26 is supported by tapered roller bearings 34 and 36 which are respectively disposed in the cover 1 6 and the case 14 and preloaded by an end cap 38.

The intermediate gears are similarly supported by tapered roller bearings 40, 42 and 46, 48, preloaded by end caps 44 and 50.

The power output gear 32 is integral with the output shaft 52 and is carried by tapered roller bearings 54 and 56 preloaded by an end cap 58.

The output shaft 52 may be connected at its two ends to forward and rear drive wheels of an industrial, four-wheel drive, articulated tractor, in which case the output shaft 52 would extend longitudinally in the tractor while the drive gear train 18 would lie in a vertical-lateral plane relative to the tractor.

Referring again to Fig 2 which shows the housing casing 14 with the cover 1 6 removed, the bottom of the case 14 defines a bottom shroud 60 which envelops the bottom gear of the drive gear train 1 8 which in the preferred, illustrated embodiment is the output gear 32.

Connected to the bottom shroud 60 is a vertically extending passageway 62 which includes a lip 64 which comes in close proximity to the tooth tips 66 of the output gear 32.

The passageway 62 has an opening 68 at the top which allows lubricant passing through the passageway 62 to enter a reservoir 70 which is separated from the gear space 13 of the housing case 14 by a wall 72.

As may be seen in Fig 1, in the quiescent state, there is a quiescent oil level 74 in the reservoir 70 which allows a comparable oil level in the gear space 13, such as to immerse both the intermediate gear 30 and the output gear 32.

The opening 68 of the passageway 62 further allows oil to pass into a dammed reservoir 76 which has a dam 78 around a portion of it. The dammed reservoir 76 provides a source of oil for the bearing 42 and allows return of oil to the gear space 13 in the housing case 14.

Above the dammed reservoir 76 are two openings 80 and 82 which connect the gear space 13 to the reservoir space and which are partiaily encircled by the outer bolt flange 84 and the inner bolt flanges 86. The inner bolt flanges 86 in part help to define the passageway 62 and include drain holes 88, 90 and 92 for directing oil to the bottom shroud 60 which is the lowest point of the gear housing 12.

It is to be noted from Fig 1 that the wall 72 of the gear housing 1 2 and the housing cover 1 6 very closely surround the gear train 18 so as to minimize the size of the housing 12. For this reason, bypass passages 94 are provided on either side of the mesh 95 between the intermediate gear 30 and the output gear 32.

Similarly, a bypass passage 96 is provided through the wall 72 to the reservoir 70 from just before the mesh 97 between the input gear 26 and intermediate gear 28. Bypass passages 94 and 96 act to provide escape passages for oil entrained in the volumes of the typical tooth spaces 100 as the meshing gear engages the tooth space. This acts to eliminate additional areas of oil turbulence.

When no power is being applied to the main drive shaft 20, the drive gear train 1 8 is stationary and the quiescent oil level 74 in the reservoir 70 is maintained in the gear space 13 as well as in the passageway 62 and reservoir 70.

When power is applied to the main drive shaft 20, the planetary gear set 22 controls the output to the input shaft 24. At very low speeds, and in reverse, oil turbulence is not a substantial factor in power loss and thus the oil evacuation system has little effect.

At the increased forward speeds, (the gears in the drive train 1 8 rotating in directions indicated by the arrows on the gears), the oil level in the passageway 62 begins to increase above the quiescent oil level 74 which drops.

At a predetermined velocity of the tooth tips 66, the oil viscously dragged around the bottom shroud 60 by the input gear 32 is diverted by the lip 64 into the passageway 62 and through the opening 68 into the reservoir 70. In the preferred embodiment, it has been found that the velocity of the tooth tips 66 must be in excess of 1 m/s and that the clearance between the lip 64 and the tooth tips 66 should be approximately 3 mm for optimum evacuation of the gear space 13.

At higher speeds, part of the oil passing through the opening 68 flows into the dammed reservoir 76 to lubricate the bearings 42 by gravity feed. At higher speeds, more oil is fed to the dammed reservoir 76, but due to the configuration of the dam 78 the oil will cascade over the dam 78 and return to the reservoir 70.

At high speeds, since a great deal of oil is transmitted to the input gear 26, oil in the top part of the gear space 13 is directed by the inner bolt flanges 86 back through the openings 80 and 82 to the reservoir 70. Similarly, oil entrained in the tooth spaces 100 at the mesh 97 of the input gear 26 and the intermediate gear 28 is displaced out of the gear space 1 3 through the bypass passage 96 into the reservoir 70. At the mesh 95, which is below the oil level in the oil reservoir 70, the bypass passages 94 and 95 allow the bypass of entrained oil in the tooth spaces 100 of the output gear 32 to flow around the mesh 95 and be drawn to the bottom shroud 60 for evacuation from the gear space 13 through the passageway 62 to the opening 68 and into the reservoir 70.

The drain hole 88 allows oil around the power intermediate gear 28 to fall on to the inner bolt flanges 86 to be drawn through the bypass passages 94 and 95 by the intermediate gear 30 and then drawing to the bottom shroud 60 by the output gear 32. The remainder of the oil about the intermediate gear 28 is drained through the drain holes 90 and 92 directly to the bottom shroud 60.

Claims

1 A gearbox with a lubricant evacuation system, comprising a train of gears stacked one upon the other in a housing in communication with a lubricant reservoir, and a passageway in the housing with an upper opening leading to the reservoir and a bottom opening adjacent the bottom gear of the train in an arrangement such that, at a sufficient speed of rotation of the bottom gear in a predetermined sense, oil is forced by the teeth of the bottom gear up the passageway and hence to the reservoir.

2. A gear box according to claim 1, wherein the passageway has a bottom up closely adjacent the bottom gear and such as to divert into the passageway oil viscously dragged by the bottom gear when it is rotating in the predetermined sense.

3. A gear box according to claim 2, wherein the spacing between the lip and the teeth of the bottom gear is approximately 3 mm,

4. A gear box according to claims 1, 2 or 3, comprising a gravity-feed lubrication system for part of the gear box fed by the lubricant forced up the passageway.

5. A gear box according to claim 4, wherein the upper opening leads to a dammed reservoir in the first said reservoir, the dammed reservoir feeding the gravity-feed lubrication system while excess lubricant fed thereto flows over the dam into the first said reservoir.

6. A gear box according to claims 1 to 5, wherein a bypass passage in the housing bypasses the mesh of two of the gears to allow oil forced out of the mesh when the gears rotate to bypass the mesh and flow back to the gears downstream of the mesh.

7. A gear box substantially as described with reference to and as illustrated in the accompanying drawings.