LUBRICATION IN A TRANSFER GEARBOX WITHOUT A MECHANICAL PUMP

Abstract

Vehicle transfer case (7), which includes the following: a case (10), a primary shaft (16) which is rotatably mounted inside the housing (10), a secondary shaft (34) which is selectively driven by the primary shaft (16), wherein the secondary shaft (34) is rotatably mounted through the housing (10), a hub (62) which is torsionally attached to the primary shaft (16), a clutch housing (52) which is selectively torsionally connected to the hub (62) via a friction package (56, 58, 64), a gear (44) which is torsionally fixed in relation to the clutch housing (52) and torsionally connected to the secondary shaft (34), a friction pack engager (74) to cause the clutch housing (52) to be selectively connected to the hub (62), and a reservoir system attached to the housing (10) to receive lubricant driven by the operation of at least one of the primary shaft (16) and the secondary shaft (34), wherein the reservoir system has a section adjacent to the engagement gear (44) and the reservoir system channels the lubricant in an axial direction, overlapping the friction pack (56, 58, 64) and supplies the lubricant to a fluid collection reservoir (96), and wherein the reservoir system has a stationary passage (98, 100) formed in the housing (10) to transport lubricant from the reservoir system to the primary shaft (16) radially inward of the friction pack (56, 58, 64), characterized in that the reservoir system has a baffle plate (90) formed by the housing (10) to deflect lubricant to the fluid collection reservoir (96) of the reservoir system.

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application claims the benefit from the preliminary US application 61 / 870 482 filed on August 27, 2013. AREA OF INVENTION

[0002] The present invention relates to transfer cases for automobiles. In particular, the field of the present invention relates to transfer cases for automobiles with a selectively selectable front-wheel drive as needed, specifically for use in vehicles with a conventional rear-wheel drive and longitudinally mounted engines. BACKGROUND OF THE INVENTION

[0003] Most rear-wheel-drive vehicles that can be selectively engaged to become all-wheel-drive vehicles have a transfer case. The transfer case typically has a primary shaft connected to the output of the vehicle's transmission. A gear is typically mounted on the primary shaft, which engages with a chain. The chain typically engages with another gear, which is typically connected to a secondary shaft. The secondary shaft is rotatably mounted within the transfer case. The secondary shaft is torsionally connected to a front driveshaft, which is torsionally connected to a front differential to drive the vehicle's front wheels.To provide a function for selective engagement of the vehicle's front wheels, a clutch mechanism is typically employed. This mechanism selectively engages the gear (on the primary shaft) with the primary shaft to transfer torque from the primary shaft to the secondary shaft, thereby selectively engaging the vehicle's front wheels. Under ideal road conditions, the clutch is typically not engaged, so the vehicle engages only the rear wheels. A control device is typically provided that detects vehicle slip conditions to automatically control clutch engagement. In some embodiments, the clutch can also be engaged upon operator request.

[0004] Most transfer cases incorporate some type of lubricant pump to provide lubrication for the clutch in its associated friction pack. The operation of this pump either presents a mechanical load to the vehicle engine by being driven by a tap from the vehicle's drivetrain, or it presents an indirect load to the engine by generating a parasitic electrical load. It is desirable to provide a transfer case in which the lubrication required for the clutch's friction pack can be provided largely or entirely passively by the operation of the transfer case itself. An example of such a transfer case is provided in U.S. Patent 7,753,173, granted to Gratzer et al. It is desirable to provide a transfer case that is an alternative to the one from Gratzer et al. Furthermore, a similar transfer case is known from JP H10-122,340 A.

[0005] US 2006 / 0 100 053 A1 describes a transfer case with a multi-plate clutch, wherein a hydraulic actuator is associated with the multi-plate clutch.

[0006] DE 10 2006 034 153 A1 describes a transmission comprising a transmission housing, a first output shaft, and a second output shaft, wherein the second output shaft can be driven by the first output shaft and both output shafts are mounted in the transmission housing. A multi-plate clutch is also provided for selectively connecting the first output shaft to the second output shaft. A gear is fixed to a clutch basket and is in rotational engagement with the second output shaft. Furthermore, a pipe system for receiving lubricant is provided, which includes a pipe adjacent to the gear, wherein the pipe, which overlaps the multi-plate clutch, channels the lubricant in the axial direction. A similar transfer case is also known from JP H06-10 655 U. SUMMARY OF THE INVENTION

[0007] To fulfill the aforementioned requirement and provide other advantages, the present invention is described. The present invention provides a transfer case with a primary shaft which can be selectively engaged with a secondary shaft via a clutch mechanism. The clutch mechanism includes a friction pack. A hub of the clutch mechanism is connected to the primary shaft, and the clutch housing is torsionally attached to a primary gear which is rotatably mounted on the primary shaft. A reservoir system is provided to transfer splashed oil axially along the primary shaft, which overlaps the friction pack. The reservoir system includes a fluid collection reservoir which is radially connected via a stationary passage to a lubrication passage within the friction pack of the hub. BRIEF DESCRIPTION OF THE DRAWING

[0008] The present invention will be more fully understood with reference to the detailed description and the accompanying drawing. The drawing shows: Fig. 1 a sectional view of a preferred embodiment of a transfer case according to the present invention, Fig. 2 a rear top view of the in Fig. 1 of the illustrated transfer case, Fig. 3 a perspective front view of the in the Fig. 1 and Fig. 2 of the illustrated transfer case, with a front cover plate removed, Fig. 4 a perspective rear view, showing parts of the transfer case in the Fig. 1 - 3 are represented in imaginary lines, Fig. 5 a partial sectional view showing a lubrication path located between the hub and a primary shaft of the Fig. 1 - 4 of the illustrated transfer case extends, Fig. 6 a perspective rear view of an alternative transfer case according to a preferred embodiment of the present invention, Fig. 7 an enlarged lateral partial sectional view of the in Fig. 6 of the illustrated transfer case, Fig. 8 a side perspective section view of the in Fig. 6 of the transfer case shown, with most of the front cover removed for illustration, and Fig. 9 another lateral perspective partial section view of the in Fig. 6 of the illustrated transfer case. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0009] The following description of the preferred embodiment(s) serves only as an example and is not intended to limit the invention, its application or its uses in any way.

[0010] With regard to the Fig. Figures 1-5 present a transfer case 7 according to the present invention. The transfer case 7 has a housing 10. The housing 10 has a front cover plate 12, which is screwed to a main body 14. A primary shaft 16 is rotatably mounted inside the transfer case housing 10. The primary shaft 16 has a front end 18 adapted to connect to an output shaft (not shown) of a vehicle's transmission. Typically, the vehicle is a rear-wheel-drive vehicle with a longitudinally mounted engine. The vehicle's drivetrain is designed to selectively divert power from the rear axle to be shared with the front axle, thus giving the vehicle all-wheel-drive capability. The primary shaft is mounted to the front cover plate 12 by a front bearing 20.A rear section of the main shaft 16 is rotatably mounted in the main housing body 14 by a rear bearing 22. A rear end 24 of the primary shaft is connected to a yoke 26 by a nut 28 engaging a washer 30. The yoke 26 is connected to a drive shaft extending to a rear differential and a rear axle (not shown) of the vehicle.

[0011] At a lower height, the transfer case 7 also houses a secondary shaft 34. The secondary shaft 34 is designed to have splined teeth 36 on its inner diameter to allow it to drive a front drive shaft (not shown), either directly or via a universal joint, which is torsionally connected to a differential for the vehicle's front wheels. The outer surface of the secondary shaft is an attached gear 38, which is provided with a series of teeth 39. The teeth 39 engage with a flexible torque transmission element or a belt 40 (shown schematically), which is typically equipped with a multi-link chain. The belt 40 engages with teeth 42 provided on the primary gear 44. The primary gear 44 is rotatably mounted on the primary shaft 16 by needle bearings 46.According to other embodiments (not shown), the primary gear can instead be a transmission in direct or indirect transmission connection with the secondary shaft.

[0012] To enable the primary shaft 16 to selectively engage torsionally with the secondary shaft 36, a coupling 50 is provided. The coupling 50 has a coupling housing 52. The coupling housing 52 is torsionally connected to the primary shaft gear 44. The coupling housing 52 has a series of radial folds 54, which provide radially inwardly projecting teeth that engage with correspondingly shaped radial edges of friction discs 56. The friction discs 56 are combined with corresponding friction plates 58. The friction plates 58 have a gear-tooth-like profile along their inner diameter to allow them to be torsionally connected to a hub 62, which has corresponding radially outwardly projecting folds. The hub 62 is torsionally attached to the primary shaft 16 by welding, wedging, or a shrink-fit arrangement. A support plate 64 is also provided.The support plate 64, the friction plates 58 and the friction discs 56 form a friction package to enable a selective connection of the clutch housing 52 with the clutch hub 62, which causes the gear 44 to be connected to the primary shaft 16.

[0013] The hub 62 has several rows of axially extending lubricant passages 70. The axial passages 70 are intersected by radially outwardly projecting lubrication holes 72, which supply lubricant to the friction pack. A piston 74 is provided for selective engagement with the friction pack. The piston 74 has a radially inner seal 76 and a radially outer seal 78. Axially behind the piston 74 is a pressurizable chamber 79, which is connected via a passage (not shown) to a source of pressurized fluid (not shown). When actuated, the piston 74 engages in a bearing 82 adjacent to the support plate 64 to engage this friction pack and thereby torsionally connect the hub 62 and the primary shaft 16 to the gear 44, the belt 40, and the secondary shaft 34 to torsionally drive the front wheels of the vehicle.

[0014] When the front wheels are engaged, lubricant must be supplied to the clutch assembly. The lubricant can also act as a coolant. Lubricant is also supplied to the belt 40, the gears 44, and the secondary shaft 36.

[0015] When the chain moves, lubricating oil is sprayed. A large portion of the oil is injected into a reservoir system that includes a collecting plate 90 with an inlet 92 substantially adjacent to the primary gear 44. The momentum of the lubricating oil causes the lubricant to be carried axially above the primary shaft 16 and above the piston 74, the clutch 50, and its associated friction assembly, overlapping them axially. The lubricant is then collected in a fluid collection reservoir 96. The fluid collection reservoir 96 is formed in the body 14 of the housing. The fluid collection reservoir 96 is stationary and has an air outlet to allow the removal of air trapped within the oil. The collection of oil develops a pressure column that enters a vertical passage 98 of the stationary housing. The vertical passage 98 intersects the rear bearing 22 to lubricate it.The vertical passage 98 intersects a substantially axial passage 100 of the stationary housing. In this way, the oil flow also extends radially into the friction assembly. The axial passage 100 allows the oil supplied by the reservoir to flow axially under the pressure columns in a substantially forward-directed flow into an axially extending lubricant passage 70 provided in the hub. One factor that improves the lubrication provided by the present invention is that, when the lubricant is transported vertically inwards through the passage 98, there is no rotating element through which it must pass. Oil entering the axial lubricant passage 70 is then forced radially outwards by rotation through lubrication holes 72 to lubricate the friction assembly.

[0016] Radially within the lubricant passage 100 is an inner lubricant passage 101. The inner lubricant passage 101 intersects a disk-shaped space 103. The disk-shaped space 103 is bounded by a seal 112, which prevents lubricating oil from being forced towards the piston 74. The primary shaft 24 is keyed to the hub 62 by a series of radially outwardly extending teeth 116, which engage with radially inwardly extending teeth 118 of the hub. One or more of the teeth 116 or 118 are omitted to provide a lubricant passage 114 extending between the interface of the hub and a primary shaft, thus allowing lubricant to flow from the rear part of the hub to the front part of the hub and thereby reach the needle bearings 46, which rotatably support the primary gear 44 on the primary shaft.

[0017] With regard to the Fig.Figures 6-9 describe a transfer case 207 according to an alternative preferred embodiment of the present invention. The transfer case 207 has a housing 210 with a front cover 212 and a main body 214. The transfer case 207 has a primary shaft 216 which is rotatably mounted on the front cover plate 212 by a front bearing 220. A hub 262 is keyed to the primary shaft 216, the hub 262 being connected to the primary shaft 216 in a manner described above and also having an axially extending lubricant passage and being connected to the primary shaft 216 as described above, wherein it has a lubricant passage similar to the passage 114.

[0018] A primary gear 244 is rotatably mounted on the primary shaft 216 by means of needle bearings 246. The primary gear 244 is rigidly connected to a clutch housing 252. The clutch housing 252 can be selectively engaged with the primary shaft 216 and the hub 262 by means of a friction pack, which can be selectively engaged by a piston 274, as previously described. The cover 212 of the front plate has an associated impact plate 215. The impact plate 215 is arranged substantially adjacent to a chain 240, which transmits torque between a primary gear 244 and a secondary gear 238. The transfer case 207 also has a lower slip adjuster 263, from which two lubrication receptacles 235 extend. The lubricant receptacles 235 help to retain lubricant within the chain 240 as the chain 240 moves from the lower secondary gear 238 to the primary gear 244.The lubricant is contained in the lower part of the housing 210 during normal use. The clutch housing 252 also has a series of axially spaced holes 253 to allow lubricant to escape from the friction pack beyond the clutch housing. The holes 253 are typically located on the radial folds 254 of the clutch housing.

[0019] When the chain 240 rotates, oil escapes from the chain 240 and is diverted by the baffle plate 215 to an adjacent inlet of the reservoir system 229. Oil also escapes from the holes 253 and moves to the reservoir system 229. A fluid collection reservoir 261 is formed by the housing 214 on one side 231 of the housing opposite a side facing the clutch housing 252. A cover for the fluid collection reservoir 261 is provided by a plate 233. The fluid collection reservoir 261 is interrupted by a stationary fluid passage 271, which is vertically inclined. The stationary passage 271 carries lubricating oil to an area adjacent to the lower half of the primary shaft 216 to lubricate the rear bearing 222 and an axial needle bearing 273.The axial needle bearing 273 is adjacent to thrust washers 275 and 277, which enable the housing to absorb the axial force generated by the engagement of the clutch, provided by the clutch housing 252 and the hub 262. The lubricant passage 271 is intersected by a substantially axial lubricant passage 281, which then supplies pressurized oil from the hydraulic pressure column formed in the reservoir 261 to the hub and needle bearings 246, as previously described in general terms. One of the essential features of the transfer case 207 is that oil circulates through the transfer case regardless of whether the hub is engaged with the clutch housing 252 via the friction pack 259.

[0020] The description of the invention serves only as an example, and modifications that do not deviate from the concept of the invention are accordingly considered to be within the scope of protection of the invention. These modifications are not considered a deviation from the concept or the scope of protection of the invention.

Claims

[1] Vehicle transfer case (7) comprising the following: a case (10), a primary shaft (16) which is rotatably mounted inside the housing (10), a secondary shaft (34) which is selectively driven by the primary shaft (16), wherein the secondary shaft (34) is rotatably mounted through the housing (10), a hub (62) which is torsionally attached to the primary shaft (16), a clutch housing (52) which is selectively torsionally connected to the hub (62) via a friction package (56, 58, 64), a gear (44) which is torsionally fixed in relation to the clutch housing (52) and torsionally connected to the secondary shaft (34), a friction pack engager (74) to cause the clutch housing (52) to be selectively connected to the hub (62), and a reservoir system attached to the housing (10) to receive lubricant driven by the operation of at least one of the primary shaft (16) and the secondary shaft (34), wherein the reservoir system has a section adjacent to the engagement gear (44) and the reservoir system channels the lubricant in an axial direction, overlapping the friction pack (56, 58, 64) and supplies the lubricant to a fluid collection reservoir (96), and wherein the reservoir system has a stationary passage (98, 100) formed in the housing (10) to transport lubricant from the reservoir system to the primary shaft (16) radially inward of the friction pack (56, 58, 64), characterized by , that the reservoir system has a baffle plate (90) formed by the housing (10) to deflect lubricant to the fluid collection reservoir (96) of the reservoir system. [2] Transfer case (7) according to claim 1, wherein the hub (62) has a lubricant passage (70) below the friction pack. [3] Transfer case (7) according to claim 2, wherein the hub lubricant passage (70) intersects radial holes (72) that intersect a surface of the hub (62) in engagement with the friction pack (56, 58, 64). [4] Transfer case (7) according to one or more of the preceding claims, wherein the stationary passage (98, 100) in the housing (10) also intersects a bearing (22) which supports the primary shaft (16) inside the housing (10). [5] Transfer case (7) according to one or more of the preceding claims, wherein the clutch housing (52) has holes which allow lubricant to escape to the reservoir system. [6] Transfer case (7) according to one or more of the preceding claims, wherein the friction pack gripper (74) has a hydraulically actuated piston (74). [7] Transfer case (7) according to one or more of the preceding claims, wherein the fluid collection reservoir (96) has an air outlet. [8] Transfer case (7) according to one or more of the preceding claims, wherein the stationary passage (98, 100) extends radially inwards from the fluid collection reservoir (96) to the clutch pack engager (74). [9] Transfer case (7) according to one or more of the preceding claims, wherein a fluid collection reservoir (96) of the reservoir system is formed through the housing (10) on a side of the housing (10) which is opposite to a side of the housing (10) facing the engagement wheel (44). [10] Transfer case (7) according to one or more of the preceding claims, wherein the fluid collection reservoir (96) is formed on a side of the housing (10) which is opposite to a side of the housing (10) facing the engagement wheel (44) and wherein the fluid collection reservoir (96) is further bounded by a plate connected to the housing (10) which faces a side (231) of the housing (10) which is opposite to a side of the housing (10) facing the engagement wheel (44). [11] Transfer case (7) according to one or more of the preceding claims, wherein a flexible torque element (40) torsionally connects the engagement wheel (44) to the secondary shaft (34) and wherein the transfer case (7) has a coating to retain lubricant within the torque transmission element (40) when the torque transmission element (40) moves between the secondary shaft (34) and the primary shaft (16). [12] Transfer case (7) according to one or more of the preceding claims, which further comprises a lubricant passage (114) formed between the primary shaft (16) and the hub (62) to provide a passage for lubricant for lubricating bearings (46) which support the engagement gear (44) on the primary shaft (16). [13] Vehicle transfer case (7) for a vehicle normally driven by a rear-wheel drive, the transfer case (7) comprising the following: a housing (10) with a rear body (14) and a front surface plate (12), a primary shaft (16) which is rotatably mounted in the housing (10), a secondary shaft (34) for driving a front differential of a vehicle, wherein the secondary shaft (34) is selectively driven by the primary shaft (16) and is rotatably mounted within the housing (10), a hub (62) which is torsionally attached to the primary shaft (16), wherein the hub (62) has an axially extending lubrication passage (70) which is intersected by substantially radial lubrication holes (72), a clutch housing (52) which is selectively torsionally connected to the hub (62) via a friction pack, wherein the clutch housing (52) has a series of holes to allow radial escape of the lubricant, a primary gear (44) rotatably mounted on the primary shaft (16) and torsionally fixed to the clutch housing (52), the gear (44) engaging with a chain, a hydraulically actuated piston (74) to engage the friction pack (56, 58, 64) which connects the clutch housing (52) to the hub (62), A reservoir system attached to the housing (10) to receive lubricant driven by the operation of the primary (16) and secondary shaft (34), wherein the reservoir system has a baffle plate (90) formed by the housing (10) adjacent to the chain, which channels lubricant to a fluid collection reservoir (96) formed by the housing (10) and axially overlapping the friction pack (56, 58, 64) and the hydraulic piston (74), and wherein the reservoir system has a stationary passage (98, 100) formed in the housing (10) to transfer lubricant from the fluid collection reservoir (96) radially inward of the friction pack (56, 58, 64) to the hub lubricant passage (70), wherein the stationary passage (98, 100) has a substantially vertical section (98) and an intersecting horizontal section (100) exhibits and the stationary passage (98,100) is also facing one of the bearings (22) supporting the primary shaft (16). [14] Vehicle transfer case (7) for a vehicle normally driven by a rear-wheel drive, the transfer case (7) comprising the following: a housing (10) with a rear body (14) and a front surface plate (12), a primary shaft (16) which is rotatably mounted in the housing (10), a secondary shaft (34) for driving a front differential of a vehicle, wherein the secondary shaft (34) is selectively driven by the primary shaft (16) and is rotatably mounted within the housing (10), a hub (62) which is torsionally fixed to the primary shaft (16), wherein the hub (62) has an axially extending lubrication passage (70) which is intersected by substantially radial lubrication holes (72), wherein the hub (62) is keyed to the primary shaft (16) and the hub (62) has an internal lubrication passage (114) between the hub (62) and the primary shaft (16) to allow the lubricant to flow from a rear end of the hub (62) to a front end of the hub (62), a clutch housing (52) which is selectively torsionally connected to the hub (62) via a friction pack (56, 58, 64), wherein the clutch housing (52) has a series of holes to allow radial escape of the lubricant to the outside, a primary gear (44) rotatably mounted on the primary shaft (16) and torsionally fixed to the clutch housing (52), wherein the gear (44) engages with a chain which torsionally connects the primary gear (44) to the secondary shaft (34), wherein the primary gear (44) is rotatably mounted on bearings (46), wherein the bearings (46) are lubricated by lubricant flowing between the hub (62) and the primary shaft (16), a hydraulically actuated piston (74) to engage the friction pack (56, 58, 64) which connects the clutch housing (52) to the hub (62), a reservoir system attached to the housing (10) to receive lubricant driven by the operation of the primary (16) and secondary shaft (34), the reservoir system comprising a baffle plate (90) formed by the housing (10) adjacent to the chain, which channels lubricant to a fluid collection reservoir (96) formed by the housing (10) and axially overlapping the friction pack (56, 58, 64) and the hydraulic piston (74), the fluid collection reservoir (96) being located on one side of the housing (10) substantially opposite to the side of the housing (10) facing the primary gear (44), and a stationary passage (98, 100) formed in the housing (10) to transfer lubricant from the fluid collection reservoir (96) radially within the friction package (56, 58, 64) to the axially extending lubricant passage (70) of the hub (62), wherein the stationary passage (98, 100) has a substantially vertically inclined section (98) which intersects a substantially horizontal section (100), and wherein the stationary passage (98, 100) also faces a rear bearing (22) which supports the primary shaft (16) within the housing (10).

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