Transfer case off-axis pump

Abstract

A transfer case pump includes an oil pump, a cover assembly, and a torque transfer mechanism. The oil pump has a pump shaft and is configured to pressurize lubricant in response to rotation of the pump shaft. The pump shaft rotates about a pump axis. The pump axis is parallel to a rear axle axis of a rear axle. The pump axis is offset from the rear axle axis. The cover assembly has a passage configured to transfer the lubricant from the oil pump to the rear axle. The cover assembly extends around the rear axle and around the pump shaft. The torque transfer mechanism is configured to transfer torque from the rear axle to the pump shaft.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to systems and methods for a transfer case off-axis pump. BACKGROUND

[0002] Single speed transfer cases and dual speed transfer cases implement on-axis transfer case pumps to move lubricant around the interior of the transfer case. The rotational speed of the on-axis transfer case pump is dictated by the speed of the corresponding shaft of the transfer case interior. When a dual speed transfer case is in low gear, the inner shaft rotates slowly. As a result, a large on-axis transfer case pump is implemented in dual speed transfer cases to maintain a minimum rate of lubrication. Such on-axis transfer case pumps typically consume up to about 250 watts of power at 2000 revolutions per minute.

[0003] There is a need for a low power transfer case off-axis pump suitable for use in both single speed transfer cases and dual speed transfer cases. SUMMARY

[0004] A transfer case pump is provided herein. The transfer case pump includes an oil pump, a cover assembly, and a torque transfer mechanism. The oil pump has a pump shaft and is configured to pressurize a lubricant in response to rotation of the pump shaft. The pump shaft rotates about a pump axis. The pump axis is parallel to a rear axle axis of a rear axle. The pump axis is offset from the rear axle axis. The cover assembly has a passage configured to transfer the lubricant from the oil pump to the rear axle. The cover assembly extends around the rear axle and around the pump shaft. The torque transfer mechanism is configured to transfer torque from the rear axle to the pump shaft.

[0005] In one or more embodiments of the transfer case pump, the cover assembly includes an annular oil transfer ring and a pump cover. The annular oil transfer ring is disposed around the rear axle and has a first passage configured to transfer the lubricant to the rear axle. The pump cover extends around the annular oil transfer ring, extends around the pump shaft, and has a second passage configured to transfer the lubricant from the oil pump to the first passage of the annular oil transfer ring.

[0006] In one or more embodiments, the transfer case pump includes an anti-rotation tab coupling the annular oil transfer ring to the rear housing and a fastener attaching the pump cover to the rear housing.

[0007] In one or more embodiments, the transfer case pump includes a cup plug in fluid communication with the passage. The cup plug has an orifice configured to disperse the lubricant from the passage toward the rear housing.

[0008] In one or more embodiments of the transfer case pump, the torque transfer mechanism includes a rear gear couplable to the rear axle and a pump gear coupled to the pump shaft and configured to engage the rear gear.

[0009] In one or more embodiments of the transfer case pump, the rear housing has an access bore aligned with the pump axis, and the transfer case pump further includes a feature disposed at an end of the pump shaft, the feature accessible through the access bore and configured to provide rotational alignment of the pump gear with the rear gear.

[0010] In one or more embodiments of the transfer case pump, the torque transfer mechanism includes a rear sprocket coupled to the rear axle, a pump sprocket coupled to the pump shaft, and a pump chain disposed about the rear sprocket and the pump sprocket.

[0011] In one or more embodiments of the transfer case pump, the transfer case includes a disc clutch, the rear housing includes a rear aperture through which the rear axle extends outside of the transfer case, and the transfer case pump is disposed between the disc clutch and the rear aperture.

[0012] In one or more embodiments, the transfer case pump is part of a transfer case of a vehicle.

[0013] A method for lubrication in a transfer case is provided herein. The method includes rotating a rear axle of the transfer case about a rear axis, and transferring torque from the rear axle to a pump shaft of an oil pump with a torque transfer mechanism. The pump shaft rotates about a pump axis. The pump axis is parallel to the rear axis. The pump axis is offset from the rear axis. The method includes pressurizing lubricant with the oil pump in response to rotation of the pump shaft, and transferring the lubricant from the oil pump to the rear axle through a passage in a cover assembly. The cover assembly extends about the rear axle and about the pump shaft.

[0014] In one or more embodiments of the method, the transferring of the lubricant through the passage in the cover assembly includes transferring the lubricant from the oil pump through a second passage of a pump cover into a first passage of an annular oil transfer ring, and transferring the lubricant through the first passage of the annular oil transfer ring to the rear axle. The annular oil transfer ring is disposed about the rear axle. The pump cover extends about the annular oil transfer ring and extends about the pump shaft.

[0015] In one or more embodiments, the method includes stabilizing the annular oil transfer ring relative to a rear housing of the transfer case, and stabilizing the pump cover relative to the rear housing.

[0016] In one or more embodiments, the method includes dispersing the lubricant from the passage toward a rear housing of the transfer case through an aperture in a cup plug in fluid communication with the passage.

[0017] In one or more embodiments of the method, the transferring of the torque from the rear axle to the pump shaft includes rotating a rear gear with the rear axle, rotating a pump gear with the rear gear, and rotating the oil pump with the pump gear.

[0018] In one or more embodiments of the method, the transferring of torque from the rear axle to the pump shaft includes rotating a rear sprocket with the rear axle, moving a pump chain disposed about the rear sprocket and a pump sprocket, and rotating an oil pump with the pump sprocket.

[0019] In one or more embodiments of the method, the torque transfer mechanism is disposed between the disc clutch and a rear aperture in a rear housing of the transfer case. The rear axle extends through the rear aperture to outside of the transfer case.

[0020] A transfer case is provided herein. The transfer case includes a rear axle, an oil pump, a cover assembly, and a torque transfer mechanism. The rear axle is configured to rotate about a rear axle line. The oil pump has a pump shaft and is configured to pressurize a lubricant in response to rotation of the pump shaft. The pump shaft rotates about a pump shaft line. The pump shaft line is parallel to the rear axle line. The pump shaft line is offset from the rear axle line. The cover assembly has a passage configured to transfer the lubricant from the oil pump to the rear axle. The cover assembly extends about the rear axle and about the pump shaft. The torque transfer mechanism is configured to transfer torque on the rear axle to the pump shaft.

[0021] In one or more embodiments of the transfer case, the cover assembly includes an annular oil transfer ring and a pump cover. The annular oil transfer ring is disposed about the rear axle and has a first passage configured to transfer the lubricant from the pump cover to the rear axle. The pump cover extends about the annular oil transfer ring, extends about the pump shaft, and has a second passage configured to transfer the lubricant from the oil pump to the first passage of the annular oil transfer ring.

[0022] In one or more embodiments, the transfer case includes a rear housing and a cup plug in fluid communication with the passage. The cup plug has an aperture configured to disperse the lubricant from the passage toward the rear housing.

[0023] In one or more embodiments, the transfer case includes a rear housing having a rear aperture through which the rear axle extends to outside of the transfer case, and a disc clutch. The torque transfer mechanism is disposed between the disc clutch and the rear aperture.

[0024] The present invention provides the following technical solutions.

[0025] Technical Solution 1. A transfer case pump, comprising:

[0026] an oil pump having a pump shaft and configured to pressurize a lubricant in response to rotation of the pump shaft, wherein the pump shaft rotates about a pump shaft line, the pump shaft line is parallel to a rear axle line of a rear axle, and the pump shaft line is offset from the rear axle line;

[0027] a cover assembly having a passage configured to transfer the lubricant from the oil pump to the rear axle, wherein the cover assembly extends about the rear axle and about the pump shaft; and

[0028] a torque transfer mechanism configured to transfer torque from the rear axle to the pump shaft.

[0029] Technical Solution 2. The transfer case pump of Technical Solution 1, wherein the cover assembly comprises:

[0030] an annular oil transfer ring disposed about the rear axle and having a first passage configured to transfer the lubricant to the rear axle; and

[0031] a pump cover extending about the annular oil transfer ring, extending about the pump shaft, and having a second passage configured to transfer the lubricant from the oil pump to the first passage of the annular oil transfer ring.

[0032] Technical Solution 3. The transfer case pump of Technical Solution 2, further comprising:

[0033] an anti-rotation tab coupling the annular oil transfer ring to a rear housing; and

[0034] a fastener attaching the pump cover to the rear housing.

[0035] Technical Solution 4. The transfer case pump of Technical Solution 1, further comprising:

[0036] a cup plug in fluid communication with the passage, wherein the cup plug has an orifice configured to disperse the lubricant from the passage toward a rear housing.

[0037] Technical Solution 5. The transfer case pump of Technical Solution 1, wherein the torque transfer mechanism comprises:

[0038] a rear gear couplable to the rear axle; and

[0039] a pump gear coupled to the pump shaft and configured to engage with the rear gear.

[0040] Technical Solution 6. The transfer case pump of Technical Solution 5, wherein a rear housing has an access bore aligned with the pump axis, the transfer case pump further comprising:

[0041] a feature disposed at an end of the pump shaft, accessible through the access bore, and configured to provide rotational alignment of the pump gear with the rear gear.

[0042] Technical Solution 7. The transfer case pump of Technical Solution 1, wherein the torque transfer mechanism comprises:

[0043] a rear sprocket coupled to the rear axle;

[0044] a pump sprocket coupled to the pump shaft; and

[0045] a pump chain disposed about the rear sprocket and the pump sprocket.

[0046] CLAIM 8. The transfer case pump of claim 1, wherein the transfer case includes a disc clutch, the rear housing includes a rear aperture through which the rear shaft extends outside of the transfer case, and the transfer case pump is disposed between the disc clutch and the rear aperture.

[0047] CLAIM 9. The transfer case pump of claim 1, wherein the transfer case pump is part of a transfer case of a vehicle.

[0048] CLAIM 10. A method for lubrication in a transfer case, comprising:

[0049] rotating a rear shaft of the transfer case about a rear shaft axis;

[0050] transferring torque from the rear shaft to a pump shaft of an oil pump with a torque transfer mechanism, wherein the pump shaft rotates about a pump shaft axis, the pump shaft axis is parallel to the rear shaft axis, and the pump shaft axis is offset from the rear shaft axis;

[0051] pressurizing a lubricant with the oil pump in response to rotation of the pump shaft; and

[0052] transferring the lubricant from the oil pump to the rear shaft through a passage in a cover assembly, wherein the cover assembly extends about the rear shaft and about the pump shaft.

[0053] CLAIM 11. The method of claim 10, wherein the transferring of the lubricant through the passage in the cover assembly includes:

[0054] transferring the lubricant from the oil pump through a second passage of a pump cover into a first passage of an annular oil transfer ring; and

[0055] transferring the lubricant through the first passage of the annular oil transfer ring to the rear shaft, wherein the annular oil transfer ring is disposed about the rear shaft and the pump cover extends about the annular oil transfer ring and extends about the pump shaft.

[0056] CLAIM 12. The method of claim 11, further comprising:

[0057] holding the annular oil transfer ring stable relative to a rear housing of the transfer case; and

[0058] holding the pump cover stable relative to the rear housing.

[0059] TECHNICAL SOLUTION 13. The method of TECHNICAL SOLUTION 10, further comprising:

[0060] dispersing the lubricant from the channel toward a rear housing of the transfer case through an orifice in a cup plug in fluid communication with the channel.

[0061] TECHNICAL SOLUTION 14. The method of TECHNICAL SOLUTION 10, wherein the transferring of the torque from the rear axle to the pump axle comprises:

[0062] rotating a rear gear with the rear axle;

[0063] rotating a pump gear with the rear gear; and

[0064] rotating the oil pump with the pump gear.

[0065] TECHNICAL SOLUTION 15. The method of TECHNICAL SOLUTION 10, wherein the transferring of the torque from the rear axle to the pump axle comprises:

[0066] rotating a rear sprocket with the rear axle;

[0067] moving a pump chain disposed about the rear sprocket and a pump sprocket; and

[0068] rotating the oil pump with the pump sprocket.

[0069] TECHNICAL SOLUTION 16. The method of TECHNICAL SOLUTION 10, wherein the torque transfer mechanism is disposed between a disc clutch and a rear orifice in a rear housing of the transfer case, and the rear axle extends through the rear orifice to outside of the transfer case.

[0070] TECHNICAL SOLUTION 17. A transfer case, comprising:

[0071] a rear axle configured to rotate about a rear axle line;

[0072] an oil pump having a pump axle and configured to pressurize a lubricant in response to rotation of the pump axle, wherein the pump axle rotates about a pump axle line, the pump axle line is parallel to the rear axle line, and the pump axle line is offset from the rear axle line;

[0073] a cover assembly having a channel configured to transfer the lubricant from the oil pump to the rear axle, wherein the cover assembly extends about the rear axle and about the pump axle; and

[0074] a torque transfer mechanism configured to transfer torque on the rear axle to the pump axle.

[0075] TECHNICAL SOLUTION 18. The transfer case of TECHNICAL SOLUTION 17, wherein the cover assembly comprises:

[0076] an annular oil transfer ring disposed about the rear axle and having a first passage configured to transfer the lubricant from the pump cover to the rear axle; and

[0077] a pump cover extending about the annular oil transfer ring, extending about the pump shaft, and having a second passage configured to transfer the lubricant from the oil pump to the first passage of the annular oil transfer ring.

[0078] Technical Solution 19. The transfer case of Technical Solution 17, further comprising:

[0079] a rear housing; and

[0080] a cup plug in fluid communication with the passage, wherein the cup plug has an orifice configured to disperse the lubricant from the passage toward the rear housing.

[0081] Technical Solution 20. The transfer case of Technical Solution 17, further comprising:

[0082] a rear housing having a rear orifice through which the rear axle extends outside of the transfer case; and

[0083] a disc clutch, wherein the torque transfer mechanism is disposed between the disc clutch and the rear orifice.

[0084] The above-mentioned features and advantages of the present disclosure and other features and advantages of the present disclosure will become apparent from the following detailed description of the best mode presently contemplated for implementing the present disclosure, when taken in conjunction with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1 is a schematic diagram illustrating an environment of a vehicle according to one or more example embodiments.

[0086] Figure 2 is a schematic cross-sectional view of a transfer case according to an example embodiment.

[0087] Figure 3 is a schematic cross-sectional view of another transfer case according to an example embodiment.

[0088] Figure 4 is a schematic cross-sectional view of a transfer case pump according to one or more example embodiments.

[0089] Figure 5 is a schematic cross-sectional view of another transfer case pump according to one or more example embodiments. DETAILED DESCRIPTION

[0090] Embodiments of the present disclosure provide a low-loss, off-axis transfer case pump for pressurizing lubricant inside a transfer case of a four-wheel drive vehicle. The transfer case pump is suitable for implementation in both single-speed transfer cases and dual-speed transfer cases. The transfer case is coupled to a transmission and is configured to distribute torque from the transmission to front and rear differentials of the vehicle.

[0091] In various embodiments, the transfer case pump can be integrated with a rear housing of the transfer case and subsequently coupled to a rear axle of the transfer case during assembly. In other embodiments, the transfer case pump can be integrated with the rear axle of the transfer case and encapsulated by the rear housing during assembly. The transfer case pump incorporates a gear-driven or chain-driven torque transfer mechanism to provide torque from the rear axle to the transfer case pump. Anti-jamming of the chain-driven torque transfer mechanism can be achieved with a snap ring. The pump shaft of the transfer case pump is oriented parallel to and offset from a corresponding rear axle in the transfer case.

[0092] An oil pump within the transfer case supports an integral oil outlet to feed lubricant under pressure into a channel within the transfer case. The channel directs lubricant to the rear axle and, in some cases, toward a rear region of the transfer case. An integral oil baffle and / or shroud can be provided to maintain lubrication levels when the vehicle is on sloped uphill and / or downhill terrain. In various designs, the cover assembly can be a one-piece device or a two-piece device. In the two-piece design, an energized annular seal maintains lubricant inside the channel under pressure. For certain designs of the transfer case, an assembly service plug and service bore are provided in the rear housing. The service bore allows a tool to couple to a feature on the pump shaft during assembly. The tool is used to twist gears in the torque transfer mechanism so that the gears mesh and rotationally align when the two gears are initially brought together.

[0093] Depending on the gear or sprocket ratio in the torque transfer mechanism, the oil pump can rotate faster, slower, or at the same speed as the rear axle. An overdrive oil pump allows for a smaller pump diameter. A small diameter oil pump is more efficient than a large diameter oil pump. The flexibility of the gear / sprocket ratio also enables the transfer case pump to use a common design in both single-speed and dual-speed transfer cases.

[0094] Reference Figure 1 FIG. 1 illustrates a schematic diagram of an environment of a vehicle 80, in accordance with one or more example embodiments. The vehicle 80 generally includes an engine 82, a transmission 84, a front drive axle 86, a rear drive axle 88, a front differential 90, a rear differential 92, a plurality of wheels 94a-94d, and a transfer case 100.

[0095] Vehicle 80 implements an automobile (or car). In various embodiments, vehicle 80 can include, but is not limited to, a passenger vehicle, a truck, an autonomous vehicle, a pneumatically powered vehicle, an electrically powered vehicle, a hybrid powered vehicle, a recreational vehicle, and / or an off-road vehicle. Other types of vehicles 80 can be implemented to meet design criteria for a particular application.

[0096] Engine 82 implements a motor for vehicle 80. In various embodiments, engine 82 can include, but is not limited to, a gasoline-powered engine, a hybrid gas / electric engine, or an electric motor. Other types of engines 82 can be implemented to meet design criteria for a particular application.

[0097] Transmission 84 implements a multi-speed transmission. Transmission 84 is coupled to engine 82. In various embodiments, transmission 84 includes several (e.g., three to ten) forward gear ratios, a neutral state, a park state, and one or more reverse gear ratios.

[0098] Front and rear drive shafts 86 and 88 are structured to transmit rotational power from transfer case 100 to front and rear differentials 90 and 92, respectively. Front differential 90 is structured to transmit torque from front drive shaft 86 to front wheels (e.g., 94a and 94b). Rear differential 92 is structured to transmit torque from rear drive shaft 88 to rear wheels (e.g., 94c and 94d).

[0099] Wheels 94a-94d implement load-bearing wheels. Wheels 94a-94d are generally structured to provide support and movement for vehicle 80 on a ground surface. In various embodiments, each wheel 94a-94d can include a tire mounted on a rim. Wheels 94a-94d can be used to provide traction between vehicle 80 and a ground surface on which vehicle 80 is disposed.

[0100] Transfer case 100 implements a single or multi-speed (e.g., two-speed) transfer case. Transfer case 100 is coupled to transmission 84 to receive input torque. Transfer case 100 is operable to direct input torque from transmission 84 to front and rear drive shafts 86 and 88. In a two-speed transfer case design, transfer case 100 can be operable to drive front and rear drive shafts 86 and 88 at the same rotational speed or a lower rotational speed than an output shaft of transmission 84. In some embodiments, transfer case 100 can be controlled to deliver input torque to front drive shaft 86 or rear drive shaft 87, but not both.

[0101] The transfer case 100 can include a dog clutch that enables the front drive shaft 86 and the rear drive shaft 88 to be decoupled from the transmission 84. By way of example, the four-wheel drive vehicle 80 can be towed in a dinghy tow mode, with the rear wheels rolling on the ground (e.g., being towed behind another vehicle or recreational vehicle). When in the dinghy tow mode, the transmission 84 is placed in park, and the transfer case 100 is placed in neutral. By implementing the transfer case pump at a location downstream relative to a reduction planetary gear set within the transfer case 100, the transfer case pump can be operated with power received from at least the rear wheels. Thus, when the vehicle 80 is being towed in the dinghy tow mode, the transfer case remains properly lubricated.

[0102] Reference is made to Figure 2 FIG. 1 shows a schematic cross-sectional view of an example implementation of a transfer case 100a in accordance with example embodiments. The transfer case 100a can be a variation of the transfer case 100 shown in FIG. 1. The transfer case 100a implements a multi-speed (e.g., dual-speed) transfer case. Figure 1

[0103] The transfer case 100a generally includes a front housing 102, an input orifice 104 in the front housing 102, a rear housing 106, a rear orifice 108 in the rear housing 106, a front orifice 109 in the front housing 102, an input shaft 110, a planetary gear set 120, a disc clutch 122, a drive chain and sprocket assembly 124, a front axle 130, a rear axle 140, a transfer case pump 150, and a torque transfer mechanism 160. The transfer case pump 150 includes a cover assembly 170, a passage 172 in the cover assembly 170, and an oil pump 180.

[0104] The input shaft 110 is coupled to the transmission 84 and the planetary gear set 120. The input shaft 110 extends through the front housing 102 through the input orifice 104. The input shaft 110 is configured to rotate about an input shaft axis 112. The input shaft 110 receives an input torque 114 from the transmission 84.

[0105] The front axle 130 is coupled to the front drive shaft 86 and the drive chain and sprocket assembly 124. The front axle 130 extends through the front housing 102 through the front orifice 109. The front axle 130 is configured to rotate about a front axle axis 132. The front axle 130 delivers a front torque 134 to the front wheels 94a and 94b through the front drive shaft 86 and the front differential 90.

[0106] The rear axle 140 is coupled to the rear drive shaft 88, the disc clutch 122, and the transfer case pump 150. The rear axle 140 extends through the rear housing 106 through the rear orifice 108. The rear axle 140 is configured to rotate about a rear axle axis 142. In various embodiments, the rear axle axis 142 is aligned with the input shaft axis 112. The rear axle 140 delivers a rear torque 144 to the rear wheels 94c and 94d through the rear drive shaft 88 and the rear differential 92.​

[0107] The planetary gear set 120 is coupled to the input shaft 110 and the rear axle 140. The planetary gear set 120 implements an adjustable multi-speed (e.g., two-speed) mechanism and a dog clutch. The planetary gear set 120 is operable to transfer the input torque 114 from the input shaft 110 to the rear axle 140 at a plurality (e.g., two) of selectable gear ratios (e.g., a low gear ratio is referred to as a high range mode and is used for normal highway driving, and a high gear ratio is referred to as a low range mode and is used for increased torque and reduced speed driving). The dog clutch is operable to alternately couple and decouple the planetary gear set from the rear axle 140. When in the engaged mode, the dog clutch transfers torque to the rear axle 140. When in the neutral mode, the dog clutch isolates the rear axle 140 from torque.

[0108] The disc clutch 122 is coupled to the drive chain and sprocket assembly 124 and the rear axle 140. The disc clutch 122 is operable to couple and decouple the drive chain and sprocket assembly 124 from the rear axle 140. When engaged, the disc clutch 122 transfers a variable amount of torque from the rear axle 140 to the drive chain and sprocket assembly 124. When disengaged, the disc clutch 122 isolates the drive chain and sprocket assembly 124 from the available torque on the rear axle 140.

[0109] The drive chain and sprocket assembly 124 is coupled to the disc clutch 122 and the front axle 130. The drive chain and sprocket assembly 124 is configured to transfer torque from the rear axle 140 through the disc clutch 122 and subsequently to the front axle 130. The front torque 134 can be greater than, less than, or equal to the rear torque 144 based on the torque transferred by the disc clutch 122 to the drive chain and sprocket assembly 124.

[0110] The transfer case pump 150 is operable to pressurize and transfer lubricant around the interior of the rear axle 140 and the transfer case 100a. In various embodiments, the transfer case pump 150 is operable to direct lubricant toward the rear region 107 of the transfer case 100a. The rear region 107 can span between the transfer case pump 150 and the rear orifice 108.

[0111] The torque transfer mechanism 160 implements a gear-based torque transfer mechanism and / or a chain-based torque transfer mechanism. As a gear-based torque transfer mechanism 160, a plurality (e.g., two or more) of gears are used to transfer torque from the rear axle 140 to the oil pump 180. As a chain-based torque transfer mechanism 160, a chain coupled to a plurality (e.g., two) of sprockets transfers torque from the rear axle 140 to the oil pump 180.

[0112] The cover assembly 170 implements a single-piece assembly or a multi-piece (e.g., two-piece) assembly. The cover assembly extends around the rear axle 140 and around a pump shaft of the oil pump 180. The cover assembly 170 is configured to direct lubricant from the oil pump 180 through the passage 172 to the rear axle 140. In various embodiments, the cover assembly 170 can also be configured to direct lubricant from the passage 172 toward the rear region 107 of the transfer case 100a.

[0113] The oil pump 180 is operable to pressurize lubricant available inside the transfer case 100a. The oil pump 180 then directs the pressurized lubricant into the cover assembly 170 for distribution. The oil pump 180 rotates around a pump axis 182. The pump axis 182 is parallel to the rear axis 142 of the rear axle 140. The pump axis 182 is offset from the rear axis 142 of the rear axle 140 by a fixed distance.

[0114] Referring to Figure 3 , a schematic cross-sectional view of an example implementation of another transfer case 100b is shown in accordance with example embodiments. The transfer case 100b can be a variation of the transfer case 100a shown in Figure 2 and / or the transfer case 100 shown in Figure 1 . The transfer case 100b implements a single-speed transfer case.

[0115] The transfer case 100b generally includes a front housing 102, an input orifice 104 in the front housing 102, a rear housing 106, a rear orifice 108 in the rear housing 106, a front orifice 109 in the front housing, an input shaft 110, a disc clutch 122, a drive chain and sprocket assembly 124, a front axle 130, a rear axle 140, a transfer case pump 150, and a torque transfer mechanism 160. The rear housing 106 generally includes ports that connect pump inlets and outlets.

[0116] In the single-speed transfer case 100b, the input shaft 110 is directly connected to the rear axle 140. In various embodiments, the input shaft 110 can be lengthened. In other embodiments, an extension shaft can be installed to effectively lengthen the input shaft 110. The single-speed transfer case 100b operates in the same manner as the multi-speed transfer case 100a when the planetary gear set 120 in the multi-speed transfer case 100a is in the high range mode. Without the planetary gear set 120 in the single-speed transfer case 100b, the single-speed transfer case 100b does not include a low range mode nor does it include a neutral mode in which the rear axle 140 is disconnected from the input shaft 110.

[0117] Referring to Figure 4 , a schematic cross-sectional view of an example implementation of a transfer case pump 150a is shown in accordance with one or more example embodiments. The transfer case pump 150a can be a variation of the transfer case pump 150 shown in Figure 2 and Figure 3a variation of the transfer case pump 150 shown in FIG. 1. The transfer case pump 150a can be integrated with the rear housing 106a during assembly. The rear housing 106a can be a variation of the rear housing 106 shown in FIGS. 1-2. Figure 2 and Figure 3 a variation of the rear housing 106 shown in FIGS. 1-2.

[0118] The transfer case pump 150a generally includes a torque transfer mechanism 160a, a cover assembly 170a, and an oil pump 180. The torque transfer mechanism 160a can be a gear-based version of the torque transfer mechanism 160 shown in FIGS. 1-2. The cover assembly 170a can be a two-piece variation of the cover assembly 170 shown in FIGS. 1-2. Figure 2 and Figure 3 a gear-based version of the torque transfer mechanism 160 shown in FIGS. 1-2. The cover assembly 170a can be a two-piece variation of the cover assembly 170 shown in FIGS. 1-2. Figure 2 and Figure 3 a two-piece variation of the cover assembly 170 shown in FIGS. 1-2.

[0119] The rear axle 140 includes an oil inlet 146 in fluid communication with the oil passage 148. The oil inlet 146 receives lubricant 190 from the cover assembly 170a. The oil inlet 146 transfers the lubricant 190 to the oil passage 148. The oil passage 148 is generally centered about the rear axle line 142. The oil passage 148 is configured to direct the lubricant 190 to other components coupled to and / or proximate to the rear axle 140.

[0120] The torque transfer mechanism 160a generally includes a rear gear 200 and a pump gear 202. The rear gear 200 is coupled to the rear axle 140 and configured to rotate with the rear axle 140. The pump gear 202 is coupled to the pump shaft 186 of the oil pump 180 and configured to rotate with the pump shaft 186. The rear gear 200 and the pump gear 202 are engaged with one another such that the rear gear 200 transfers torque to the pump gear 202. In various embodiments, the gear geometry of the rear gear 200 and the pump gear 202 can implement spur gear geometry, helical geometry, or double helical geometry. Other geometries can be implemented to meet design criteria of a particular application.

[0121] The rotational speed of the rear axle 140 is typically no higher than a few thousand (e.g., approximately 4200) revolutions per minute. Thus, existing oil pump designs operate below the "high speed fill limit." An advantage can be gained by overdriving the oil pump 180 with the torque transfer mechanism 160a to further reduce losses and still meet lubrication standards. At a reasonable gear center distance 203, a reduction / overdrive ratio in the range of approximately 0.8: 1 to approximately 1.8: 1 can be achieved. The gear pitch radius of the rear gear 200 is in the range of approximately 32 millimeters (mm) to approximately 52 mm (e.g., 42.5 mm). The gear pitch radius of the pump gear 202 is in the range of approximately 18 mm to approximately 38 mm (e.g., 28.5 mm). The gear center distance 203 between the center of the rear gear 200 (e.g., rear axle line 142) and the center of the pump gear 202 (e.g., pump axle line 182) can be in the range of approximately 54 mm to approximately 84 mm (e.g., 69 mm). For example, a gear ratio of 42.5 mm radius (rear gear 200) to 28.5 mm radius (pump gear 202) at a 69 mm gear center distance 203 yields a ratio of approximately 1.6: 1. Achieving a small gear center distance 203 generally reduces the mass and windage of the rear gear 200 and the pump gear 202. Other overdrive ratios and / or gear center distances 203 can be achieved to meet design criteria for a particular application.

[0122] The highest lubrication demand of the transfer case 100a generally exists in trucks operating in low range mode. In low range mode, the output rotational speed of the rear axle 140 is less than half of the input rotational speed of the input shaft 110. The planetary gear set 120 is active in low range mode, creating high lubrication standards to maintain active planetary pinions. In contrast, some trucks implement a single speed transfer case 100b and thus do not have a low range mode. To achieve commonality between the dual speed transfer case 100a and the single speed transfer case 100b, a flexible strategy can be employed in the gear-based torque transfer mechanism 160a. This strategy enables high overdrive in the dual speed transfer case 100a and potential reduction drive in the single speed transfer case 100b by changing the gear ratio between the rear gear 200 and the pump gear 202. For example, at a 90 mm gear center distance 203, a 0.9: 1 gear ratio option can be implemented to reduction drive the single speed transfer case 100b. A 1.8: 1 gear ratio option can be implemented to overdrive the dual speed transfer case 100a. The remaining components in the transfer cases 100a and 100b can remain unchanged, except for the effective length of the input shaft 110.

[0123] One or both of the gears 200 and 202 can be made of powdered metal, aluminum, bronze, cast iron, or the like. To reduce noise, one or both of the gears 200 and 202 can be made of a non-metallic material. For example, one or both of the gears 200 and 202 can be made of polyether ether ketone (PEEK) or a similar thermoplastic polymer. The pressure of the lubricant 190 within the transfer case 100 / 100a / 100b is approximately 500 kiloPascals (kPa). In comparison, the lubrication pump in the transmission 84 generally operates at 2100 kPa. Experimental testing has shown that gears made of PEEK material are able to apply lower stresses in the transfer case 100 / 100a / 100b. Other materials can be utilized to meet the design criteria of a particular application.

[0124] The cover assembly 170a implements a two-part assembly. The first part of the cover assembly 170a includes an annular oil transfer ring 210 having a first channel 212, a cup plug 214 having an orifice 216, and an anti-rotation tab 218. The second part of the cover assembly 170a includes a pump cover 220 having a second channel 222. A plurality of cover seals 224 are disposed in grooves in the annular oil transfer ring 210.

[0125] The annular oil transfer ring 210 is disposed around an outer circumference of the rear axle 140 and is coupled to the pump cover 220. An inner diameter of the annular oil transfer ring 210 is sealed metal-to-metal to an outer diameter of the rear axle 140. A fluid connection is established between the first channel 212 of the annular oil transfer ring 210 and the oil inlet 146. The first channel 212 is also in fluid communication with the second channel 222 of the pump cover 220 to receive lubricant 190 from the oil pump 180.

[0126] The cup plug 214 is in fluid communication with the first channel 212. The orifice 216 in the cup plug 214 is configured to disperse lubricant 190 from the first channel 212 toward the rear region 107 of the rear housing 106a. The orifice 216 helps to regulate lubrication to components in the rear region 107 of the transfer case 100 / 100a / 100b. The components include, but are not limited to, output ball bearings, bushings, and seals. The orifice 216 also helps to maintain lubrication during downhill vehicle operation. The timed position of the cup plug 214 can be tuned to establish a head height of the lubrication feed.

[0127] The anti-rotation tab 218 extends from the annular oil transfer ring 210 to engage with the rear housing 106a. The anti-rotation tab 218 is configured to prevent the annular oil transfer ring 210 from rotating due to friction with the rear axle 140.

[0128] The pump cover 220 is configured to couple the oil pump 180 to the annular oil transfer ring 210. The pump cover 220 is fastened to the rear housing 106a and spans two axes (e.g., the rear axis 142 and the pump axis 182). The pump cover 220 includes an orifice in which some portions of the oil pump 180 reside and another orifice (e.g., a circular opening) that surrounds the annular oil transfer ring 210. A second channel 222 transfers lubricant 190 from the oil pump 180 to the first channel 212 of the annular oil transfer ring 210. The pump cover 220 also provides a dam feature at the interface with the annular oil transfer ring 210 and the rear housing 106a. The dam feature prevents the transfer of lubricant 190 between the rear region 107 and the front region of the transfer case 100 / 100a / 100b.

[0129] The cover seal 224 is configured to seal the first channel 212 to the second channel 222, preventing the leakage of lubricant 190. The cover seal 224 also provides a radial tolerance allowance between the outer diameter of the annular oil transfer ring 210 and the inner diameter of the corresponding orifice in the pump cover 220. Since both the annular oil transfer ring 210 and the pump cover 220 are coupled to the rear housing 106a, there is no active rotation at the sealing interface. The cover seal 224 can be made of Teflon, Torlon, Vespel, PEEK, etc. Alternatively, an O-ring can be used with some adjustment to the groove width. The fastener 226 (e.g., a bolt) is configured to secure the pump cover 220 to the rear housing 106a.

[0130] The oil pump 180 generally includes a pump shaft 186 and a gerotor gear pair 188-189. The pump shaft 186 rotates about a pump axis 182. The pump axis 182 is parallel to the rear axis 142 of the rear shaft 140. The pump axis 182 is offset from the rear axis 142 by a gear center distance 203. The pump shaft 186 is configured to couple the inner gerotor gear 189 to the pump gear 202 to receive a pump torque 184. The pump shaft 186 includes a feature 206 (e.g., a drive hex feature) that provides for manual rotation during assembly. The pump torque 184 rotates the gerotor gear pair 188-189 to pressurize the lubricant 190.

[0131] During assembly of the transfer case 100 / 100a / 100b, the oil pump 180 can be inserted into a pocket machined in the rear housing 106a. Fasteners 226 then secure the oil pump 180 to the rear housing 106a. The rear gear 200, the annular oil transfer ring 210, and the shieldless bearing 230 are attached to the rear axle 140 before the rear housing 106a is mated to the front housing 102. A cover seal 224 is applied to the annular oil transfer ring 210. With the annular oil transfer ring 210 aligned with a corresponding aperture in the pump cover 220, the rear axle 140 and the rear housing 106a, with the attached oil pump 180, are moved relative to one another to bring the rear housing 106a into contact with the front housing 102. The rear housing 106a includes an access bore 204 that is aligned with the pump axis 182. With the rear gear 200 engaged with the pump gear 202, a tool (not shown) can be inserted into the access bore 204 to engage a feature 206 at a proximal end of the pump shaft 186. The tool is used to oscillate (or rotate) the pump shaft 186 and the pump gear 202 so that the pump gear 202 is aligned with and meshed with the rear gear 200. The front housing 102 and the rear housing 106a are then attached to one another to close the transfer case 100 / 100a / 100b. After the tool is removed from the access bore 204, an access plug 208 is inserted into the access bore 204 to seal the opening.

[0132] Reference is made to Figure 5 , which shows a schematic cross-sectional view of an example implementation of a transfer case pump 150b, in accordance with one or more example embodiments. The transfer case pump 150b can be a variant of the transfer case pump 150 shown in Figure 2 and Figure 3 and / or the transfer case pump 150a shown in Figure 4 . The transfer case pump 150b can be coupled to the rear axle 140 prior to installation of the rear housing 106b during assembly. The rear housing 106b can be a variant of the rear housing 106 shown in Figure 2 and Figure 3 and / or the rear housing 106a shown in Figure 4 .

[0133] The transfer case pump 150b generally includes a torque transfer mechanism 160b, a cover assembly 170b, and an oil pump 180. The torque transfer mechanism 160b can be a chain-based version of the torque transfer mechanism 160 shown in Figure 2 and Figure 3 . The cover assembly 170b can be a single-piece variant of the cover assembly 170 shown in Figure 2 and Figure 3 .

[0134] The oil inlet 146 of the rear axle 140 is in fluid communication with the cover assembly 170b to receive the lubricant 190.

[0135] The torque transfer mechanism 160b generally includes a rear sprocket 240 and a pump sprocket 244. The rear sprocket 240 is coupled to the rear axle 140 and is configured to rotate with the rear axle 140. The pump sprocket 244 is coupled to the pump shaft 186 of the oil pump 180 and is configured to rotate with the pump shaft 186. A chain 242 engages the rear sprocket 240 and the pump sprocket 244 to transfer torque from the rear axle 140 to the pump shaft 186.

[0136] The chain-based torque transfer mechanism 160b can have the same advantages as the gear-based torque transfer mechanism 160a in that the oil pump 180 can be underdrive or overdrive based on the radii of the rear sprocket 240 and the pump sprocket 244. At a reasonable chain center distance 243, an underdrive / overdrive ratio in a range of about 0.8: 1 to about 1.8: 1 can be achieved. The radius of the rear sprocket 240 is in a range of about 32 mm to about 52 mm (e.g., 42.5 mm). The radius of the pump sprocket 244 is in a range of about 18 mm to about 38 mm (e.g., 28.5 mm). The chain center distance 243 between the center of the rear sprocket 240 (e.g., the rear axis 142) and the center of the pump sprocket 244 (e.g., the pump axis 182) can be in a range of about 54 mm to about 84 mm (e.g., 69 mm).

[0137] As with the transfer case 100a, the highest lubrication requirements of the transfer case 100b generally exist in trucks operating in low range mode. To allow for commonality between the two-speed transfer case 100a and the single-speed transfer case 100b, a flexible strategy can be employed in the chain-based torque transfer mechanism 160b. This strategy allows for high overdrive in the two-speed transfer case 100a and potential underdrive in the single-speed transfer case 100b by changing the ratio between the rear sprocket 240 and the pump sprocket 244. For example, at a 90 mm chain center distance 243, a 0.9: 1 ratio option can be implemented to underdrive the single-speed transfer case 100b. A 1.8: 1 ratio option can be implemented to overdrive the two-speed transfer case 100a. Except for the effective length of the input shaft 110, the rest of the components in the transfer cases 100a and 100b can remain the same.

[0138] One or both of the sprockets 240 and 244 can be made of powdered metal, aluminum, bronze, cast iron, etc. Other materials can be utilized to meet the design criteria of a particular application.

[0139] The cap assembly 170b implements a single-piece integrated assembly. The cap assembly 170b includes a unitary cap 250, an angled channel 252, and a support 254. The orifice of the unitary cap 250 is disposed about the outer circumference of the rear axle 140 and is coupled to the oil pump 180. The inner diameter of the orifice of the unitary cap 250 is metal-to-metal sealed to the outer diameter of the rear axle 140. A fluid connection is established between the angled channel 252 and the oil inlet 146. The angled channel 252 is also in fluid communication with the oil pump 180 to receive the lubricant 190.

[0140] The cup plug 214 is in fluid communication with the angled channel 252. The orifice 216 in the cup plug 214 is configured to disperse the lubricant 190 from the angled channel 252 toward the rear region 107 of the rear housing 106b. The orifice 216 helps to regulate lubrication to components in the rear region 107 of the transfer case 100 / 100a / 100b. A deflector 262 can be located proximate the cup plug 214 downstream of the dispersed lubricant 190. The components include, but are not limited to, output ball bearings, bushings, and seals. The timed position of the cup plug 214 can be tuned to establish a head height of the lubrication feed.

[0141] The support 254 extends from the unitary cap 250 to engage the rear housing 106b. The support 254 engages the rear housing 106b using a snap ring 256. The support 254 and the snap ring 256 are configured to prevent the unitary cap 250 from moving laterally along the rear axis 142. The support 254 and the snap ring 256 are also configured to prevent the unitary cap 250 from rotating due to friction with the rear axle 140. The snap ring 256 can help prevent the unitary cap 250 from binding relative to the rear housing 106b.

[0142] The fastener 226 attaches the unitary cap 250 to the rear housing 106b. The bore in the rear housing 106b that receives the fastener 226 is oversized relative to the diameter of the fastener 226 to account for tolerances. The fastener 226 also prevents lateral movement and rotation of the unitary cap 250. A gasket 228 is disposed between the head of the fastener 226 and the rear housing 106b. The gasket 228 generally protects the lower half of the transfer case pump 150b from clunking, rattling, and other types of movement.

[0143] The one-piece cover 250 is configured to couple the oil pump 180 to the rear axle 140. The one-piece cover 250 is fastened to the rear housing 106b and spans two axes (e.g., the rear axis 142 and the pump axis 182). The one-piece cover 250 includes an orifice in which some portions of the oil pump 180 reside and another orifice (e.g., a circular opening) that surrounds the rear axle 140. An angled channel 252 passes lubricant 190 from the oil pump 180 to the rear axle 140. The one-piece cover 250 provides a dam feature at the interface with the rear axle 140 and the rear housing 106b. The dam feature prevents the passage of lubricant 190 between the rear region 107 and the front region of the transfer case 100 / 100a / 100b.

[0144] The oil pump 180 generally includes a pump shaft 186 and a gerotor pump gear 188-189. The pump shaft 186 rotates about a pump axis 182. The pump axis 182 is parallel to the rear axis 142 of the rear axle 140. The pump axis 182 is offset from the rear axis 142 by a chain center distance 243. The pump shaft 186 is configured to couple the inner gerotor pump gear 189 to the pump gear 202 to receive a pump torque 184. The pump torque 184 rotates the gerotor gear pair 188-189 to pressurize the lubricant 190.

[0145] Adjacent to the torque transfer mechanism 160b includes an oil shield 246. The oil shield 246 is secured to the support with a snap ring and castle nut combination. A shielded bearing 260 is disposed adjacent to the one-piece cover 250. The shield on the side of the bearing 260 facing the one-piece cover 250 retains the lubricant 190 in the rear region 107 of the transfer case 100 / 100a / 100b for adequate downhill grade lubrication.

[0146] During assembly of the transfer case 100 / 100a / 100b, the rear sprocket 240, the oil pump 180, and the shielded bearing 260 are attached to the rear axle 140 before the rear housing 106b is mated to the front housing 102. The snap ring 256 is applied to a groove in the one-piece cover 250. The rear housing 106b and the rear axle 140 are moved relative to one another with the attached oil pump 180 to bring the rear housing 106b into contact with the front housing 102. The front housing 102 and the rear housing 106b are subsequently attached to one another to close the transfer case 100 / 100a / 100b. Thereafter, the fasteners 226 and the gaskets 228 are used to attach the one-piece cover 250 to the rear housing 106b.

[0147] The various embodiments of the transfer case 100 / 100a / 100b generally provide reduced drag, reduced carbon dioxide emissions, and / or better fuel economy for the vehicle 80. The oil pump 180 can consume as little as about 20 watts at 2000 revolutions per minute. The low power consumption can reduce carbon dioxide emissions by about 1-2 grams per mile.

[0148] While the best mode has been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the present disclosure within the scope of the appended claims.

Claims

1. A transfer case pump, comprising: an oil pump having a pump shaft and configured to pressurize lubricant in response to rotation of the pump shaft, wherein the pump shaft rotates about a pump axis that is parallel to a rear axis of a rear axle of the transfer case and offset from the rear axis; a cover assembly having a passage configured to transfer the lubricant from the oil pump to the rear axle, wherein the cover assembly extends around the rear axle and around the pump shaft; and a torque transmitting mechanism configured to transmit torque from the rear axle to the pump shaft, Wherein, the cover assembly comprises: an annular oil transfer ring disposed about the rear axle and having a first passage configured to transfer the lubricant to the rear axle; and a pump cover extending around the annular oil transfer ring, extending around the pump shaft, and having a second passage configured to transfer lubricant from the oil pump to the first passage of the annular oil transfer ring, wherein the rear housing of the transfer case includes a rear aperture through which the rear axle extends to the exterior of the transfer case, and wherein the cover assembly is disposed between the torque transmitting mechanism and the rear aperture, and wherein the oil pump is disposed between the rear axle and a front axle of the transfer case, and wherein the pump cover provides a dam feature at an interface with the annular oil transfer ring and the rear housing to divide the interior of the transfer case into a rear region and a front region and prevent the lubricant from transferring between the rear region and the front region of the transfer case, wherein the rear region spans between the transfer case pump and the rear port, and the transfer case pump is operable to direct the lubricant toward the rear region of the transfer case.

2. The transfer case pump according to claim 1, further comprising: an anti-rotation tab coupling the annular oil transfer ring to the rear housing of the transfer case; and Fasteners attach the pump cover to the rear housing.

3. The transfer case pump according to claim 1 , further comprising: A cup plug is in fluid communication with the first passage, wherein the cup plug has an orifice configured to disperse the lubricant from the first passage toward a rear housing of the transfer case.

4. The transfer case pump according to claim 1, wherein: The torque transmitting mechanism includes: a rear gear coupleable to the rear axle; and A pump gear is coupled to the pump shaft and is configured to engage the rear gear.

5. The transfer case pump according to claim 4, wherein: The rear housing of the transfer case has an inspection inner hole aligned with the pump axis, and the transfer case pump further comprises: A feature disposed at an end of the pump shaft is accessible through the service bore and is configured to provide rotational alignment of the pump gear with the rear gear.

6. The transfer case pump according to claim 1, wherein: The torque transmitting mechanism includes: a rear sprocket coupled to the rear axle; a pump sprocket coupled to the pump shaft; and A pump chain is disposed around the rear sprocket and the pump sprocket.

7. The transfer case pump according to claim 1, wherein: The transfer case includes a disc clutch, and the transfer case pump is disposed between the disc clutch and the rear port.

8. The transfer case pump according to claim 1, wherein: The transfer case pump is part of the vehicle's transfer case.

9. A method for lubrication in a transfer case, comprising: rotating a rear axle of the transfer case about a rear axis; transmitting torque from the rear axle to a pump shaft of an oil pump using a torque transmitting mechanism, wherein the pump shaft rotates about a pump axis, the pump axis is parallel to the rear axis, and the pump axis is offset from the rear axis; pressurizing lubricant with the oil pump in response to rotation of the pump shaft; and transferring the lubricant from the oil pump to the rear axle through a passage in a cover assembly, wherein the cover assembly extends around the rear axle and around the pump shaft, wherein said transferring of said lubricant through said channel in said cover assembly comprises: transferring the lubricant from the oil pump through the second passage of the pump cover to the first passage of the annular oil transfer ring; and transferring the lubricant through the first passage of the annular oil transfer ring to the rear axle, wherein the annular oil transfer ring is disposed about the rear axle and the pump cover extends about the annular oil transfer ring and about the pump shaft, wherein the rear housing of the transfer case includes a rear aperture through which the rear axle extends to the exterior of the transfer case, and wherein the cover assembly is disposed between the torque transmitting mechanism and the rear aperture, and wherein the oil pump is disposed between the rear axle and a front axle of the transfer case, and wherein the pump cover provides a dam feature at an interface with the annular oil transfer ring and the rear housing to divide the interior of the transfer case into a rear region and a front region and prevent the lubricant from transferring between the rear region and the front region of the transfer case, wherein the rear region spans between the oil pump and the rear port, and the oil pump is operable to direct the lubricant toward the rear region of the transfer case.

10. The method according to claim 9, further comprising: stabilizing the annular oil transfer ring relative to the rear housing of the transfer case; and The pump cover is held stable relative to the rear housing.

11. The method according to claim 9, further comprising: The lubricant is dispersed from the first passage toward a rear housing of the transfer case through an orifice in a cup plug in fluid communication with the first passage.

12. The method according to claim 9, wherein The transmission of the torque from the rear axle to the pump shaft includes: causing the rear gear to rotate together with the rear axle; causing the pump gear to rotate together with the rear gear; and The oil pump is caused to rotate together with the pump gear.

13. The method according to claim 9, wherein: The transmission of the torque from the rear axle to the pump shaft includes: causing the rear sprocket to rotate together with the rear axle; moving a pump chain disposed about the rear sprocket and the pump sprocket; and The oil pump is caused to rotate together with the pump sprocket.

14. The method according to claim 9, wherein The torque transmitting mechanism is disposed between the disc clutch and the rear port.

15. A transfer case comprising: a rear axle configured to rotate about a rear axis; an oil pump having a pump shaft and configured to pressurize lubricant in response to rotation of the pump shaft, wherein the pump shaft rotates about a pump axis, the pump axis is parallel to the rear axis, and the pump axis is offset from the rear axis; a cover assembly having a passage configured to transfer the lubricant from the oil pump to the rear axle, wherein the cover assembly extends around the rear axle and around the pump shaft; and a torque transmitting mechanism configured to transmit torque on the rear axle to the pump shaft, Wherein, the cover assembly comprises: an annular oil transfer ring disposed about the rear axle and having a first passage configured to transfer the lubricant from the pump cover to the rear axle; and the pump cover extending around the annular oil transfer ring, extending around the pump shaft, and having a second passage configured to transfer lubricant from the oil pump to the first passage of the annular oil transfer ring, wherein the rear housing of the transfer case includes a rear aperture through which the rear axle extends to the exterior of the transfer case, and wherein the cover assembly is disposed between the torque transmitting mechanism and the rear aperture, and wherein the oil pump is disposed between the rear axle and a front axle of the transfer case, and wherein the pump cover provides a dam feature at an interface with the annular oil transfer ring and the rear housing to divide the interior of the transfer case into a rear region and a front region and prevent the lubricant from transferring between the rear region and the front region of the transfer case, wherein the rear region spans between the oil pump and the rear port, and the oil pump is operable to direct the lubricant toward the rear region of the transfer case.

16. The transfer case of claim 15, further comprising: A cup plug is in fluid communication with the first passage, wherein the cup plug has an orifice configured to disperse the lubricant from the first passage toward the rear housing.

17. The transfer case of claim 15, further comprising: A disc clutch, wherein the torque transmitting mechanism is disposed between the disc clutch and the rear port.

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