lubrication system and such a comprehensive transfer case

Abstract

Lubrication system (42) for use in a transfer case (16) of a motor vehicle powertrain (10), wherein the lubrication system (42) comprises the following: a housing (44) that defines an inner chamber (56) and has a lower section (58); a partition (46) extending from the lower section (58) of the housing (44) and arranged in the inner chamber (56) such that a reservoir chamber (66) for oil is defined next to the partition (46) and spaced apart from the inner chamber (56); a first sprocket (48) which is rotatably supported in the inner chamber (56) and is spaced apart from the container chamber (66); a second sprocket (50) which is rotatably supported in the inner chamber (56); a pump arrangement (52) comprising the following: an oil pump (78) and a receiver (80) which is in flow communication with the oil pump (78) and is at least partially arranged in the reservoir chamber (66); and an endless chain (54) connecting the first sprocket (48) to the second sprocket (50), wherein the chain (54) is spaced away from the partition (46) so that in operation a drift force is generated to transport oil from the inner chamber (56) to the reservoir chamber (66), characterized in that the pump arrangement (52) has a spray bar (82) in flow connection with the oil pump (78) for directing oil (68) pumped from the reservoir chamber (66) to a predetermined location in the inner chamber (56).

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates generally to transfer cases for motor vehicles, and in particular to a lubrication system for a transfer case. 2. Description of the related technology

[0002] Conventional four-wheel drive systems for motor vehicles typically include an internal combustion engine that delivers torque to a transmission, which in turn adjusts the engine speed and torque. The transmission then transfers the adjusted torque to a transfer case. The transfer case is configured to selectively transfer torque to a rear differential in a rear-wheel drive mode, or to both the rear and front differentials in a four-wheel drive mode. To this end, transfer cases typically include a housing that contains a series of shafts, gears, chains, and linkages that work together to effect the selective transfer of torque to the differentials. The transfer case is usually oil-lubricated and includes a pump assembly configured to circulate oil to the various shafts, gears, chains, and linkages in operation.

[0003] The pump assembly typically includes an oil pump that is rotaryally connected to and driven by the shafts, gears, or chains, and which displaces oil from a reservoir chamber to the various components of the transfer case. The pump assembly also usually includes a receiver that is in flow contact with the oil in the reservoir.

[0004] All components of a transfer case of the type described above must work together to selectively and effectively transfer rotation from the transmission to the differentials. Furthermore, each component must be designed not only to enable improved performance and efficiency, but also to reduce the cost and complexity of manufacturing the transfer case.

[0005] DE 10 2012 218 054 B3 describes a transfer case with an oil reservoir and an oil sump separated from the oil reservoir by a partition wall. A lower sprocket is immersed in the sump to distribute the oil within the transfer case. Furthermore, a hydraulically actuated clutch is provided for connecting and disconnecting the lower sprocket from an upper sprocket. This clutch is driven by an oil pump. The oil pump also drives a hydraulic actuator, which interacts with a flap in the partition wall to allow oil to flow from the oil reservoir into the oil sump when the clutch is engaged and to close the flap when the clutch is disengaged.

[0006] Although known transfer case lubrication systems have demonstrated good performance for their specific purpose in related technology, there remains a need in the field for a transfer case lubrication system that offers better operating characteristics and also reduces the cost and complexity of manufacturing the components of the transfer case. BRIEF DESCRIPTION OF THE INVENTION

[0007] The present invention overcomes the disadvantages of related technologies in a lubrication system for use in a transfer case of a motor vehicle drivetrain. The lubrication system comprises a housing that defines an inner chamber and has a lower section. A partition extends from the lower section of the housing and is arranged in the inner chamber, defining a reservoir chamber for oil adjacent to the partition and spaced apart from the inner chamber. A first sprocket is rotatably supported in the inner chamber and is spaced apart from the reservoir chamber, and a second sprocket is rotatably supported in the inner chamber. The lubrication system also includes a pump assembly.The pump assembly comprises an oil pump, a receiver connected to the oil pump and located at least partially within the reservoir chamber, and a spray bar connected to the oil pump for directing oil pumped from the reservoir chamber to a predetermined location in the inner chamber. The lubrication system also includes an endless chain connecting the first sprocket to the second sprocket. The chain is spaced from the partition wall so that, during operation, a drift force is generated to transport oil from the inner chamber to the reservoir chamber.

[0008] Furthermore, the present invention relates to a transfer case for transmitting torque from a transmission to the differentials of a motor vehicle. The transfer case comprises a housing that defines an inner chamber and has a lower section. A partition extends from the lower section of the housing and is arranged in the inner chamber, such that a reservoir chamber for oil is defined next to the partition and spaced apart from the inner chamber. A first sprocket is rotatably supported in the inner chamber and is spaced apart from the reservoir chamber, and a second sprocket is rotatably supported in the inner chamber. The transfer case also includes a pump assembly.The pump assembly comprises an oil pump, a receiver connected to the oil pump and located at least partially within the reservoir chamber, and a spray bar connected to the oil pump for directing oil pumped from the reservoir chamber to a predetermined location in the inner chamber. The distribution gearbox also includes an endless chain connecting the first sprocket to the second sprocket. The chain is spaced from the partition wall so that, during operation, a drift force is generated to transport oil from the inner chamber to the reservoir chamber.

[0009] In this way, parasitic losses during operation in the transfer case are significantly reduced to a minimum by the lubrication system of the present invention. Furthermore, the lubrication system reduces the cost and complexity of manufacturing transfer case housings, which exhibit improved operating characteristics such as high efficiency, improved packaging and ground clearance, as well as an extended service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Further tasks, features and advantages of the present invention will become readily apparent with a better understanding of the invention after reading the following detailed description in conjunction with the accompanying drawings, wherein: Fig. Figure 1 shows a schematic top view of the drive train of a four-wheel drive motor vehicle comprising a transfer case according to an embodiment of the present invention. Fig. 2 is a cross-sectional view of a transfer case lubrication system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Regarding the figures in which the same reference numbers are used to designate the same structure, a part of a motor vehicle's drivetrain is shown in Fig. Figure 1 at 10 is shown schematically. The drivetrain 10 comprises an internal combustion engine 12, a transmission 14, and a transfer case 16. The engine 12 generates torque and is in rotary engagement with the transmission 14. The transmission 14 adjusts the speed and torque from the engine and is configured to deliver the adjusted rotation, as described in more detail below. It will be obvious to the average person skilled in the art that the transmission 14 can be of various designs and thus, depending on the application, can be in rotary engagement with the engine 12 in any suitable manner. As a by no means limiting example, the transmission 14 could include a gear set (not shown, but generally known in the art) that is operated either manually or automatically, or the transmission 14 could be continuously variable.Furthermore, it will be obvious to the average expert that the gearbox is 14, although the engine is 12 and the gearbox is 14 in the representation of . Fig. 1 are operatively coupled, could be spaced apart from the motor 12, so that the weight distribution in the drive train 10 is improved without deviating from the scope of protection of the present invention.

[0012] The gearbox 14 is rotaryally connected to the transfer case 16 and transmits the adjusted torque to it. In the illustrative embodiment shown here, the transfer case 16 is positioned in series with the gearbox 14 and is thus rotaryally connected via a gearbox output shaft 18. However, it will be obvious to the person skilled in the art that the transfer case 16 and the gearbox 14 could be rotaryally connected to each other in a different manner. In particular, it is understood that the gearbox 14 and the transfer case 16 could be offset from each other and rotaryally connected via an intermediate shaft with one or more universal joints (not shown, but generally known in the art), thereby allowing additional flexibility with regard to weight distribution and packaging in the drive train 10.

[0013] The transfer case 16 is generally configured to selectively transmit torque to a rear axle differential 20 in a rear-wheel-drive mode, or to both the rear axle differential 20 and a front axle differential 22 in a four-wheel-drive mode. It will be obvious to a person skilled in the art that the transfer case 16 could be switched from a rear-wheel-drive mode to a four-wheel-drive mode in various ways, such as by mechanical levers or electronically controlled actuators, without departing from the scope of protection of the present invention. The transfer case 16 comprises a rear output 24 and a front output 26 rotaryally connected to the rear axle differential 20 and the front axle differential 22, respectively.A pair of drive shafts 28 with one or more universal joints 30 connect the outputs 24, 26 of the transfer case 16 to the differentials 20, 22, so that torque is transmitted to them. The differentials 20, 22 are each in rotary connection with a corresponding pair of wheels and tires 32, 34 and transmit torque to the wheels and tires 32, 34, so that the automobile is driven during operation. In the illustrative embodiment shown here, the differentials 20, 22 are supported by respective axle assemblies 36, 38 with hubs, generally shown at 40, to which the wheels and tires 32, 34 are mounted. However, it will be obvious to the person skilled in the art that the differentials 20, 22 could transmit torque to the wheels and tires 32, 34 in several different ways, depending on the application.

[0014] Now, with reference to Fig. Figure 2 shows a cross-sectional view of a distribution gearbox 16 of the type described above. In particular, in Fig. Figure 2 shows a lubrication system for the transfer case 16 according to an embodiment of the present invention. The lubrication system 42 comprises a housing 44, a partition 46, a pair of sprockets 48, 50, a pump assembly 52, and an endless chain 54. Each of these components is described in more detail below.

[0015] The housing 44 of the transfer case 16 defines an inner chamber 56 in which the lubrication system 42 is generally arranged. The housing 44 has a lower section 58 that transitions into an upper section 60. In the illustrative example shown here, the lower section 58 and the upper section 60 comprise several integrated projections 62 with connecting screws 64 arranged therein. It will be obvious to the person skilled in the art that the projections 62 and screws 64 interact with the housing 44 of the transfer case 16, such that various individual sections of the housing 44 are fixed to one another (not shown in detail, but generally known in the art).It is understood, however, that the housing 44 could be fixed in any suitable manner, and that the projections 62 and screws 64 could be configured differently or omitted entirely, without deviating from the scope of protection of the present invention.

[0016] The partition 46 extends from the lower section 58 of the housing 44 and is located in the inner chamber 56, thus defining a reservoir chamber 66 for oil 68. The reservoir chamber 66 and the oil 68 are therefore spaced apart from the inner chamber 56 and are located next to the partition 46. The oil 68, the reservoir chamber 66, and the inner chamber 56 interact with the sprockets 48, 50, the pump assembly 52, and the chain 54, as described in more detail below.

[0017] The first sprocket 48 is rotatably supported in the inner chamber 56 of the housing 44 and is spaced apart from the reservoir chamber 66. Similarly, the second sprocket 50 is rotatably supported in the inner chamber 56 of the housing 44. The sprockets 48 and 50 are connected by the endless chain 54, which is spaced apart from the partition 46, so that during operation a drift force is generated to transport oil 68 from the inner chamber 56 to the reservoir chamber 66. As can be seen from the following description of the pump arrangement 52, the fact that the first sprocket 48 is spaced apart from the reservoir chamber 66 and thus not immersed in the oil 68 significantly reduces aeration of the oil 68 and minimizes parasitic losses.

[0018] In one embodiment, the partition 46 defines an acute angle 70 with the lower section 58 of the housing 44 adjacent to the container chamber 66. However, it will be obvious to the person skilled in the art that the partition 46 could be configured in another suitable manner with respect to the lower section 58 of the housing 44 without departing from the scope of protection of the present invention. Furthermore, in one embodiment, the partition 46 is essentially parallel to at least one section of the chain 54 that is arranged between the first sprocket 48 and the second sprocket 50. It is understood, however, that the chain 54 can bend during operation and stretch over time.Thus, the section of chain 54 described above could be located at any suitable point during a sufficient operating point, which is defined in any suitable way between the sprockets 48, 50, so that it is substantially parallel to the partition 46 as described above, without deviating from the scope of protection of the present invention.

[0019] In one embodiment, the inner chamber 56 of the housing 44 includes a curved pocket section, generally shown at 72, next to the first sprocket 48. Furthermore, the housing 44 extends as shown in Fig. 2 shown in the partition 46 next to the curved pocket section 72. However, it is obvious to the person skilled in the art that the partition 46 could be designed or configured differently and could be spaced apart or otherwise separated from the housing 44 to an extent sufficient to define the container chamber 66 as described above, without deviating from the scope of protection of the present invention. Furthermore, the housing 44 is as shown in Fig. Figure 2 shows the inner chamber 56 spaced at a substantially constant distance from the endless chain 54 along its curved pocket section 72. However, as described above, the chain 54 can stretch or otherwise bend during operation, and thus the curved pocket section 72 and the inner chamber could be spaced differently or otherwise configured to accommodate the chain 54 without deviating from the scope of protection of the present invention. In particular, it is conceivable that the inner chamber 56 or the curved pocket section 72 could comprise an elliptical profile (not shown, but generally known in the art) configured to maintain a predetermined distance from the chain 54 during operation.

[0020] In one embodiment, the partition 46 extends into the lower section 58 of the housing 44 and reaches to an end edge 74. The end edge 74 is located in the inner chamber 56 of the housing 44 and is spaced further from the lower section 58 of the housing 44 than a maximum oil level 76 (see Fig. 2) the container chamber 66. As shown, the end edge 74 of the partition wall 46 has a curved profile. However, it will be obvious to the person skilled in the art that the end edge 74 could have any suitable profile sufficient to allow the displacement of oil into the container chamber 66 without departing from the scope of protection of the present invention.

[0021] As described above, the lubrication system 42 of the present invention comprises a pump assembly 52. ​​The pump assembly 52 includes an oil pump 78, a receiver 80 which is in fluid communication with the oil pump 78 and is at least partially located in the reservoir chamber 66, and a spray bar 82. It is understood that the oil pump 78 displaces oil 68 from the reservoir chamber 66 and distributes it over the entire transfer case 16, thus ensuring the proper operation of the various components described above. Furthermore, the spray bar 82 is in fluid communication with the oil pump 78 and directs oil 68 pumped from the reservoir chamber 66 to a predetermined location in the inner chamber 56. Advantageously, the spray bar 82 directs oil 68 to the first sprocket 48 or the endless chain 54.However, it will be obvious to the average person skilled in the art that the spray bar 82 could direct oil 68 to a suitable location in the inner chamber 56 without departing from the scope of protection of the present invention.

[0022] In one embodiment, the first sprocket 48 can be rotatably supported by and aligned with a first shaft 84, with the oil pump 78 being spaced apart from the shaft 84 and thus in rotational connection. It is understood that the first shaft 84 could be any suitable shaft in the distribution gearbox 16 sufficient for an arrangement in fluid flow connection with the oil pump 78. Furthermore, the distribution gearbox 16 can also include a second shaft 86 spaced apart from the first shaft 84, with the second sprocket 50 being rotatably supported by the second shaft 86 and aligned concentrically with it. It is understood that the first and second shafts 84 and 86 can define the outputs 24 and 26 of the distribution gearbox 16 as described above.However, it will be obvious to the average person skilled in the art that the first and second shafts 84, 86 could be configured differently so that they are in rotary connection with other components of the distribution gearbox 16 without deviating from the scope of protection of the present invention.

[0023] As in Fig. As shown in Figure 2, the oil pump 78 is spaced apart from the first shaft 84 and is driven "off-axis" with respect to both shafts 84, 86, whereby the oil pump 78 is not arranged concentrically to either shaft 84, 86. In the Fig. In the embodiment shown in Figure 2, the oil pump 78 is driven off-axis by the second shaft 86, with the respective centers of rotation of the oil pump 78 and the second shaft 86 being spaced apart from each other. It will be obvious to the person skilled in the art that driving the oil pump 78 off-axis in this way significantly improves the packaging of the transfer case 16, since otherwise, if driven on the shaft, the oil pump 78 would require additional length with respect to the shafts 84 and 86.

[0024] In one embodiment, the oil pump 78 is a gerotor pump, and the pump arrangement 52 further comprises a bypass valve 90 for regulating the oil pump 78 based on the flow rate. However, it will be obvious to the person skilled in the art that the oil pump 78 could have any suitable design and be regulated in any way without departing from the scope of protection of the present invention.

[0025] As in Fig. As shown in Figure 2, in one embodiment the first and second shafts 84, 86 define an alignment 88 by their respective centers of rotation. The alignment 88 is essentially parallel to the partition 46. It is therefore understood that the alignment 88, like the partition 46, can also define the acute angle 70 with respect to the lower section 58 of the housing 44 of the transfer case 16 as described above.

[0026] It is understood that the lubrication system 42 and the distribution gearbox 16 of the present invention substantially reduce parasitic losses during operation. In particular, it is understood that the alignment of the sprockets 48, 50, the pump assembly 52, and the reservoir chamber 66 reduces aeration of the oil 68, such that the first sprocket 48 does not need to be immersed in oil 68 for proper lubrication, and that the drift force described above simultaneously prevents an accumulation of oil 68 and displaces the oil 68 to the reservoir chamber 66. Furthermore, it is understood that the present invention reduces the cost and complexity of manufacturing a distribution housing 16 that exhibits improved operating characteristics, such as high efficiency, improved packaging, and improved ground clearance, as well as an improved service life.

[0027] The invention has been described in an illustrative manner. It is understood that the terminology used is to be descriptive rather than restrictive. Given the above teachings, many modifications and variations of the invention are possible. Therefore, within the scope of protection of the appended claims, the invention can be exercised in ways other than those specifically described.

Claims

[1] Lubrication system (42) for use in a transfer case (16) of a motor vehicle powertrain (10), wherein the lubrication system (42) comprises: a housing (44) that defines an inner chamber (56) and has a lower section (58); a partition (46) extending from the lower section (58) of the housing (44) and arranged in the inner chamber (56) such that a reservoir chamber (66) for oil is defined next to the partition (46) and spaced apart from the inner chamber (56); a first sprocket (48) which is rotatably supported in the inner chamber (56) and is spaced apart from the container chamber (66); a second sprocket (50) which is rotatably supported in the inner chamber (56); a pump arrangement (52) comprising the following: an oil pump (78) and a receiver (80) which is in flow communication with the oil pump (78) and is at least partially arranged in the reservoir chamber (66); and an endless chain (54) connecting the first sprocket (48) to the second sprocket (50), wherein the chain (54) is spaced away from the partition (46) so that in operation a drift force is generated to transport oil from the inner chamber (56) to the reservoir chamber (66), characterized by , that the pump arrangement (52) has a spray bar (82) in flow connection with the oil pump (78) for directing oil (68) pumped from the reservoir chamber (66) to a predetermined location in the inner chamber (56). [2] Lubrication system (42) according to claim 1, wherein the partition (46) defines an acute angle (70) with the lower section (58) of the housing (44) next to the reservoir chamber (66). [3] Lubrication system (42) according to claim 1, wherein the partition (46) is substantially parallel to at least one section of the endless chain (54) which is arranged between the first sprocket (48) and the second sprocket (50). [4] Lubrication system (42) according to claim 1, wherein the inner chamber (56) of the housing (44) comprises a curved pocket section (72) next to the first sprocket (48). [5] Lubrication system (42) according to claim 4, wherein the housing (44) transitions into the partition (46) next to the curved pocket section (72). [6] Lubrication system (42) according to claim 4, wherein the housing (44) is spaced at a substantially constant distance along the curved pocket section (72) of the inner chamber (56) from the endless chain (54). [7] Lubrication system (42) according to claim 1, wherein the partition (46) extends into the lower section (58) of the housing (44) and extends to an end edge (74) which is arranged in the inner chamber (56), wherein the end edge (74) is spaced further from the lower section (58) of the housing (44) than a maximum oil level of the reservoir chamber (66). [8] Transfer gear (16) for transmitting torque from a gearbox to differentials of a motor vehicle, the transfer gear (16) comprising the following: a housing (44) that defines an inner chamber (56) and has a lower section (58); a partition (46) extending from the lower section (58) of the housing (44) and arranged in the inner chamber (56) such that a reservoir chamber (66) for oil is defined next to the partition (46) and spaced apart from the inner chamber (56); a first sprocket (48) which is rotatably supported in the inner chamber (56) and is spaced apart from the container chamber (66); a second sprocket (50) which is rotatably supported in the inner chamber (56); a pump arrangement (52) comprising the following: an oil pump (78) and a receiver (80) which is in flow communication with the oil pump (78) and is at least partially arranged in the reservoir chamber (66); and an endless chain (54) connecting the first sprocket (48) to the second sprocket (50), wherein the chain (54) is spaced away from the partition (46) so that in operation a drift force is generated to transport oil from the inner chamber (56) to the reservoir chamber (66), characterized by, that the pump arrangement (52) has a spray bar (82) in flow connection with the oil pump (78) for directing oil pumped from the reservoir chamber (66) to a predetermined location in the inner chamber (56). [9] Transfer case (16) according to claim 8, wherein the partition (46) defines an acute angle (70) with the lower section (58) of the housing (44) next to the reservoir chamber (66). [10] Transfer case (16) according to claim 8, wherein the partition (46) is substantially parallel to at least one section of the endless chain (54) which is arranged between the first sprocket (48) and the second sprocket (50). [11] Transfer case (16) according to claim 8, wherein the inner chamber (56) of the housing (44) comprises a curved pocket section (72) next to the first sprocket (48). [12] Transfer case (16) according to claim 11, wherein the housing (44) transitions into the partition (46) next to the curved pocket section (72). [13] Distributor gear (16) according to claim 11, wherein the housing (44) is spaced at a substantially constant distance along the curved pocket section (72) of the inner chamber (56) from the endless chain (54). [14] Transfer case (16) according to claim 8, wherein the partition (46) extends into the lower section (58) of the housing (44) and extends to an end edge (74) which is arranged in the inner chamber (56), wherein the end edge (74) is spaced further from the lower section (58) of the housing (44) than a maximum oil level of the reservoir chamber (66). [15] Distributor gear (16) according to claim 1, wherein the first sprocket (48) is rotatably supported by a shaft (84) and is concentrically aligned thereon, wherein the oil pump (78) is spaced apart from the shaft (84) and is thus in rotary connection.

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