Compact coaxial deceleration drive unit

Abstract

A reduction drive unit may include: a differential device including a differential case accommodating a plurality of pinions intermeshing with a pair of side gears; and a compound planetary gear device including a sun gear, a fixed ring gear, and a plurality of planetary gears. The planetary gear is supported by the differential case or a planet carrier coupled to the differential case. A lubrication system forces lubricant to flow to the planetary gear device. The lubrication system may utilize a splash lubrication device and / or a forced lubrication device within the differential case.

Description

[0001] Cross-citation to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 481,354, filed on January 24, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to differentials for vehicle drivetrains, and more particularly, to open differentials incorporating planetary gear sets in an advantageous arrangement to achieve speed reduction. Background Art

[0004] A reduction drive unit or differential assembly for use in a motor vehicle is used to provide a gear reduction between the drive shaft of a power plant and the axle half-shafts coupled to the vehicle's wheels. The differential assembly also allows for a differential to be generated between the axle half-shafts. Differentials are well-known devices used in vehicle drivetrains. These devices operate to couple a pair of rotating members, such as drive shafts or axle half-shafts, about an axis of rotation. Thus, differentials have been used as part of a transfer case that operatively couples the front and rear axles of a vehicle, in open differentials and limited-slip and locking differentials for coupling axle half-shafts, as well as in other applications known in the art.

[0005] Differentials of the type known in the art may include a housing and a gearbox operatively supported by the housing for rotation by the vehicle driveline. The differential typically includes at least one pair of side gears. The side gears are splined to rotate with a pair of rotating members (e.g., axle half-shafts). A cross shaft having a cross pin is operatively mounted for rotation with the gearbox. Pinion gears are mounted for rotation with the cross pin and in meshing relationship with the side gears. Differential rotation of the side gears, and thereby of the axle half-shafts, can be achieved by rotation of the pinion gears relative to the cross pin, as is well known in the art. Summary of the Invention

[0006] A differential for a vehicle may include: a housing; a differential gear device disposed within the housing, the differential gear including a plurality of pinion bevel gears and a pair of side gears connected to a pair of half-shafts; a hollow drive shaft for connecting to an electric motor, the hollow drive shaft extending on one of the pair of half-shafts and coaxially aligned with the half-shaft; a sun gear formed with or coupled to the hollow drive shaft; a ring gear fixedly fastened to the housing; and a planetary gear device including three planetary gear members, each of the three planetary gear members including a first-stage planetary gear intermeshing with the sun gear and a second-stage planetary gear intermeshing with the ring gear.

[0007] A reduction drive unit may include: a differential device, including a differential case accommodating a plurality of pinion gears meshing with a pair of side gears; and a compound planetary gear device, including a sun gear, a fixed ring gear, a plurality of planetary gears and a planetary carrier structure that rotatably supports the plurality of planetary gears, wherein: the planetary carrier structure is rigidly mounted to the differential case; each of the plurality of planetary gears has a first-stage gear meshing with the sun gear and an axially offset second-stage gear meshing with the fixed ring gear; and the ring gear is axially offset relative to the sun gear so that the sun gear is axially located between the ring gear and the differential device.

[0008] A reduction drive unit may include: a housing assembly, including a first housing portion that matches a second housing portion; a differential device, including a differential case that houses a plurality of pinion gears that mesh with a pair of side gears, the differential device being completely housed within the first housing portion; and a compound planetary gear device, including a sun gear, a fixed ring gear, a plurality of planetary gears, and a planetary carrier structure that rotatably supports the plurality of planetary gears, wherein: the planetary carrier structure is rigidly mounted to the differential case; each of the plurality of planetary gears has a first stage gear that meshes with the sun gear and a second stage gear that meshes with the fixed ring gear; and the sun gear, the fixed ring gear, and the plurality of planetary gears are completely housed within the second housing portion.

[0009] This Summary is provided to introduce some concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Non-limiting and non-exhaustive embodiments are described with reference to the following figures.

[0011] Figure 1 is a schematic cross-sectional view of a compact coaxial reduction unit having features according to the present disclosure.

[0012] Figure 2 yes Figure 1 A schematic cross-sectional view of a compact coaxial reduction unit is shown, illustrating the power flow.

[0013] Figure 3 yes Figure 1 Schematic cross-sectional end view of a compact coaxial reduction unit shown.

[0014] Figure 4 yes Figure 1 Schematic perspective exploded view of the compact coaxial reduction unit shown.

[0015] Figure 5is a cross-sectional view of a drive system according to one embodiment, the drive system including an electric motor and a differential reduction drive unit having features according to the principles of the present disclosure.

[0016] Figure 6 yes Figure 5 A perspective view of a differential reduction drive unit is shown with components separated from one another for easier viewing.

[0017] Figure 7 yes Figure 5 A side cross-sectional view of a portion of a differential reduction drive unit is shown.

[0018] Figure 8 yes Figure 5 A longitudinal section of a differential reduction drive unit is shown, and further illustrating the power flow through the unit.

[0019] Figure 9 yes Figure 5 A perspective view of an exemplary subassembly of a differential reduction drive unit is shown.

[0020] Figure 10 is a cross-sectional view of an exemplary differential having a first type of lubrication system configured according to the principles of the present disclosure.

[0021] Figure 11 yes Figure 10 Another cross-sectional view of the differential, where the lubrication paths to the planetary gear arrangement are visible.

[0022] Figure 12 yes Figure 10 Another cross-sectional view of the differential, where the lubrication paths to the differential gear sets are visible.

[0023] Figure 13 is a cross-sectional view of an exemplary differential having a second type of lubrication system configured according to the principles of the present disclosure.

[0024] Figure 14 yes Figure 13 Another cross-sectional view of the differential, where the lubrication paths to the differential gear sets are visible.

[0025] Figure 15 yes Figure 13 Another cross-sectional view of the differential, where the lubrication path through the differential case is visible.

[0026] Figure 16 yes Figure 13 Another cross-sectional view of the differential, where the lubrication path through the planet carrier to the planetary gear sets is visible.

[0027] Figure 17 is suitable for Figures 10 to 17A perspective view of an exemplary differential case for use in any of the embodiments.

[0028] Figure 18 is a cross-sectional view of an exemplary differential having a third type of lubrication system configured according to the principles of the present disclosure.

[0029] Figure 19 It is along Figure 18 A transverse cross section taken along line 19-19.

[0030] Figure 20 yes Figure 18 A cross-sectional view of a differential, where the lubrication paths to the planetary gear arrangement are visible.

[0031] Figure 21 is a cross-sectional view of an exemplary differential having a fourth type of lubrication system configured according to the principles of the present disclosure.

[0032] Figure 22 Shown by Figure 21 The lubrication path of the differential housing.

[0033] Figure 23 Is suitable for Figure 21 A perspective view of an exemplary differential case for use with a differential. DETAILED DESCRIPTION

[0034] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which specific embodiments or examples are shown by way of illustration. These aspects may be combined, other aspects may be utilized, and structural changes may be made without departing from the present disclosure. These embodiments may be practiced as methods, systems, or devices. Therefore, the following detailed description should not be construed as limiting, and the scope of the present disclosure is defined by the appended claims and their equivalents.

[0035] The accompanying drawings generally illustrate an exemplary drive system suitable for use in, for example, a vehicle application. As shown, the drive system includes an electric motor assembly 70, 170 (see, for example, Figure 1 and Figure 8 ) and differential assemblies 10, 110. A representative embodiment of a differential assembly 10, 110 that may employ side gears and pinions of the type contemplated by the present teachings is Figure 1 and Figure 5 The differential 10, 110 is generally shown in the drawings wherein like reference numerals are used throughout the drawings to indicate like structure. The differential 10, 110 is designed to be used as part of a driveline system for any number of vehicles having a powerplant for providing power to the vehicle.

[0036] Thus, those skilled in the art will appreciate from this disclosure that differential 10, 110 may be used as part of a transfer case for operatively coupling the front and rear axles of a vehicle in an open differential, a limited slip differential, or a locking differential for coupling axle half shafts, as well as in other applications known in the art. A limited slip differential or a locking differential may be hydraulically or electronically actuated and thus include a coupling mechanism, such as a friction clutch, for operatively coupling the axle half shafts together under certain operating conditions. It will be understood from this disclosure that differential 10, 110 is intended merely to provide a basic representative embodiment of a device that may employ features of the present teachings and is not intended to limit the application of the present teachings to the types of differentials represented therein.

[0037] With this in mind, in its most basic configuration, the differential 10, 110 can include a housing assembly, generally indicated at 12, 112. In one aspect, the housing assembly 12, 112 can include a motor housing 12a that mates with a differential housing 12b, 112b via fasteners (not shown), such as screws or bolts. The motor housing 12a is configured to at least partially enclose a motor 70, 170 (e.g., an electric motor, a hybrid electric motor, etc.). The differential housing 12b, 112b at least partially encloses a differential case 14, 114 that includes a differential gear arrangement 15, 115. The differential gear arrangement 15, 115 connects two axle shafts 30, 130 (e.g., axle half shafts) of the vehicle. The drive shaft 28, 128 extends on a first shaft 30a, 130a of the axles 30, 130 and is driven by the motor 70, 170. The compound planetary gear arrangement 50, 150 operatively connects the drive shaft 28, 128 to the differential housing 12, 112, which is operatively connected to the differential gear set 15, 115. Thus, the compound planetary gear set 50, 150 and the differential gear set 15, 115 connect the electric motor 70, 170 to the second of the shafts 30, 130, 30b, 130b.

[0038] The compound planetary gear apparatus 50, 150 includes a sun gear 32, 132, a ring gear 34, 134, and two or more planet gears 24, 124. The sun gear 32, 132 is operatively connected to the drive shaft 28, 128 and is driven by the motor 70, 170. The ring gear 34, 134 is rotationally fixed to the housing assembly 12, 112 so that the ring gear 34, 134 rotates together with the housing assembly 12, 112. Each of the planet gears 24, 124 includes a first gear portion 24a, 124a that engages with the sun gear 32, 132 and a second gear portion 24b, 124b that engages with the ring gear 34, 134. Rotational torque from the drive shaft 28, 128 is transmitted to the sun gear 32, 132, along the planet gears 24, 124, to the ring gear 34, 134, and thereby to the housing assembly 12, 112. As is known in the art, the rotational torque of the housing assembly 12 , 112 is transferred to the second shaft 30 b , 130 b through the differential gear set 15 , 115 .

[0039] In some implementations, the planetary gears 124 are supported by the differential case 114 (see, e.g., Figures 1 to 4 ). For example, in some implementations, at least the second gear portion 124b of the planetary gear 124 is radially aligned with the differential case 114. In other implementations, the planetary gears 24 are supported by the planetary carrier 16 (see, for example, Figures 5 to 9 In some implementations, the planet carrier 16 is mounted to the differential case 14 (e.g., via fasteners). In some embodiments, the planet carrier 16 is axially offset relative to the differential case 14 along the drive shaft 28 such that the planet gears 24 are axially offset relative to the differential case 14.

[0040] In some implementations, the compound planetary gear set 150 is coaxially arranged with the differential gear set 115 (see, for example, Figures 1 to 4 ). Ring gear 134 is disposed about differential case 114 such that ring gear 134 is radially aligned with differential gear arrangement 115. Positioning ring gear 134 about differential case 114 provides a compact axial footprint for housing assembly 12. At least second gear portions 124b of planet gears 124 are also radially aligned with differential gear set 115. Sun gear 132 is axially offset relative to differential gear arrangement 115 such that sun gear 132 is not radially aligned with differential gear arrangement 115. First gear portions 124a of planet gears 124 are radially aligned with sun gear 132.

[0041] In other implementations, the compound planetary gear set 50 is axially offset relative to the differential gear set 15 along the axis of rotation X of the drive shaft 28 (see, e.g., Figures 5 to 9). The ring gear 34 is axially offset relative to the differential case 14. In certain implementations, the ring gear 34 is radially disposed about the planet carrier 16 that holds the planet gears 24. The axial offset of the planetary gear set 50 relative to the differential case 14 along the axis of rotation X of the drive shaft 28 allows for a compact radial footprint of the housing assembly 12 because the planet gears 24 can overlap the differential case 14 along the axis of rotation X of the drive shaft 28.

[0042] Now refer to Figures 1 to 4 An exemplary differential 110 includes a compact, coaxial reduction unit, shown as including an assembly cover 112b housing a differential case 114 having a right-hand split 114b and a left-hand split 114a. In one aspect, the differential case 114 supports a pair of differential side gears 138 that intermesh with three differential bevel gears 148. As shown, axle half shafts 130 are splined or otherwise connected to the differential side gears. The differential case 114 also supports a sun gear 132 rotatably disposed about one of the shafts 130, 130a.

[0043] In certain implementations, at least a portion of the differential case 114 is shown as further supporting a planetary gear arrangement 150 comprising three planetary gear members 124. Each planetary gear member 124 includes a first-stage planetary gear 124a and a second-stage planetary gear 124b. This configuration may be referred to as a compound planetary gear arrangement. In one aspect, the differential case 114 serves as the planet carrier 116 of the planetary gear arrangement 150. A ring gear 134 is also provided, secured within the assembly cover 112b. In one aspect, each of the planetary gear members 124 is supported at one end by a ball bearing assembly 182 and at an opposite end by a needle bearing assembly 180.

[0044] In one aspect, the sun gear 132 is driven by the rotor of the electric motor 70. In one aspect, the sun gear 132 meshes with the first-stage planet gears 124a of the three planetary gear members 124. In one aspect, the planetary gear members 124 are mounted on the planet carrier 116 at 120-degree intervals. In one aspect, each of the planetary gear members 124 has two sets of teeth cut on a single shaft to form the first-stage planet gears 124a and the second-stage planet gears 124b. In one aspect, the planet shafts are supported in the planet carrier 116 with needle bearings 180 on one side and ball bearings 182 on the other side. In one aspect, the sun gear 132 meshes with the first-stage planet gears 124a, while the second-stage planet gears 124b mesh with the ring gear 134. In one aspect, the ring gear 134 is secured in the housing 112 (e.g., the assembly cover 112b) via protrusions on the ring gear 134 and corresponding semicircular slots in the housing 112.

[0045] In one aspect, the planet carrier 116 of the planetary assembly 150 serves as the differential case 114. In certain implementations, the differential case 114 includes a three-pinion yoke assembly 186. In one aspect, three pinion shafts 188 are mounted 120 degrees apart for each planet gear 124 so that the forces are properly balanced (e.g., see FIG. Figure 3 ). Pinion gears 148 are mounted on pinion shafts 188. Thus, in a three-pinion design, each pinion gear 148 is disposed opposite a planet gear 124.

[0046] In one aspect, the differential case 114 is a split design. In certain embodiments, the differential case 114 includes a first body 114a that mates with a second body 114b to enclose the side gears 138 and the pinion gears 148. In certain implementations, the first body 114a holds a needle bearing device 180, and the second body 114b holds a ball bearing device 182.

[0047] It should be noted that Figure 1 The sun gear 132 is shown with Figure 2 The difference shown is that the sun gear 132 is Figure 1 The center spline is connected to the hollow drive shaft 128, and the sun gear is Figure 2 The electric motor 170 is formed integrally with the hollow drive shaft 128. In both cases, the electric motor 170 has a hollow rotor which is the hollow shaft 128 itself or is connected to the hollow shaft. Figure 1 As shown, the hollow drive shaft 128 can be supported by ball bearings 185 .

[0048] refer to Figure 2, which schematically illustrates the power flow of differential unit 110, with electric motor 70 driving sun gear 132, which meshes with first-stage planetary gears 124a. Thus, motor torque is amplified by the ratio between sun gear 132 and first-stage planetary gears 124a. This same torque acts on second-stage planetary gears 124b and is further amplified by the ratio between second-stage planetary gears 124b and ring gear 134, which serves as a fixed component. In one aspect, the output of planetary gears 124 is taken from planet carrier 116, which can be a differential case 114. From case 114, power is transferred to tripod yoke 186, which in turn transfers power to side bevel gears 138 via pinion bevel gears 148. This power is then transferred to shaft 130.

[0049] One particularly advantageous combination is the use of a planetary gear arrangement 150 having three compound planetary gear members 124 in combination with three bevel gears 148, as compared to a more conventional double pinion bevel gear differential or planetary differential. Figure 3 As can be most easily seen in FIG, this arrangement allows the axes PR1, PR2, PR3 of the three pinion shafts 188 associated with the tripod yoke 186 (which are the same as the axis of rotation of the pinion bevel gears 148) to be radially aligned with the compound planetary gear member 124 on opposite sides of the longitudinal axis L of the differential 110 so that the forces can be optimally balanced.

[0050] The disclosed design has several advantages. For example, the design provides a compact design for high reduction ratios. For example, the differential assembly requires a smaller number of bearings. For example, the planetary pinion shafts and the differential pinion shaft 188 are mounted in the structural member 186 serving as the case 114 and the planetary carrier 116. For example, the planetary gears 124 are mounted directly in the planetary carrier 116 using external bearings 180, 182, thereby eliminating the need for planetary pins. In some embodiments, the system reliability is high due to the smaller number of components used. In some embodiments, the design has the advantage of ease of assembly. In some embodiments, the design has the advantage of high quality compound planetary gear manufacturing due to its unique design.

[0051] Now refer to Figures 5 to 9Another exemplary differential 10 includes a separate planetary gear carrier 16 and a differential case 14. In some implementations, the planetary gear carrier 16 is offset relative to the differential case 14 along the longitudinal axis X of the differential 10. In some implementations, the planetary gear carrier 16 is mechanically fastened or otherwise coupled to the differential case 14 to move in unison with the differential case 14. In some implementations, at least a majority of the differential case 14 is mounted within a differential case 12b of the housing 12, while at least a majority of the planetary gear carrier 16 is mounted within a motor case 12a of the housing 12. In some embodiments, the differential case 12b includes an assembly cover.

[0052] In one aspect, a lower baffle structure 12c is provided and secured to the motor housing 12a, for example, by fasteners 12d. The baffle structure 12c partially encloses the planetary gears 24, which will be discussed in greater detail later. A differential case, generally indicated at 14, can be operatively supported within the housing assembly 12 for rotation in a driven relationship by a drivetrain, as is known in the art. Those skilled in the art will appreciate in light of this disclosure that the differential case 14 and housing assembly 12 can be defined by any conventional structure known in the relevant art, and that the present teachings are not limited to the particular housing assembly 12 shown herein, nor to the differential case 14 shown.

[0053] In some implementations, the differential gear arrangement 15 includes a side gear 38 for each axle 30 and one or more pinion gears 48 connected to the side gears 38. In one aspect, the differential case 14 houses a pair of side gears 38a, 38b (collectively, side gears 38) connected to a pair of axle half shafts 30a, 30b (collectively, axle half shafts 30). Although not shown in the figures, the axle half shafts 30 extend to and drive the wheels of the vehicle. The side gears 38 intermesh with four pinion gears 48a, 48b, 48c, 48d, which are collectively referred to as pinion gears 48. As shown, the pinion gears 48 are rotatably supported by pinion shafts 40a, 40b, 40c, 40d, which are collectively referred to as pinion shafts 40. The pinion shaft 40 extends through the opening 14a in the differential case 14 so that rotation of the differential case 14 about the longitudinal axis X causes the pinion shaft 40 and the pinion gears 48 to rotate with the differential case 14, which in turn rotates the side gears 38 and the axle shafts 30 to drive the wheels of the vehicle. The differential case 14, the pinion gears 48, the pinion shaft 40, and the side gears 38 can be collectively referred to as a differential assembly 60. Figure 5 As can be seen, seals 52, 54 are provided between the differential case 14 and the housing 12b.

[0054] In one aspect, the differential case 14 is connected to and driven by the planetary carrier structure 16 via fasteners (e.g., screws or bolts). Thus, the differential case 14 and the planetary carrier structure 16 form a unified, rigid structure. The assembled differential case 14 and the planetary carrier structure 16 are rotationally supported at one end by a bearing assembly 18 that supports the planetary carrier structure 16 within the motor housing 12 a, and at the other end by a bearing assembly 20 that supports the differential case 14 within the differential housing 12 b. The planetary carrier structure 16 forms part of a planetary gear arrangement 50 that includes a plurality of planetary gears 24 that are rotationally supported by bearing assemblies 26 mounted to fixed pins 22. In the illustrated embodiment, three bearing assemblies 26 are provided for each planetary gear 24, and the bearing assemblies are configured as needle roller bearing assemblies. In the illustrated embodiment, the pins 26 are axially and rotationally secured within the planetary carrier structure 16 using grub screws having internal threads. In one aspect, the planet carrier structure 16 includes a first radial wall 16a and a spaced-apart second radial wall 16b, with a plurality of axial legs 16c extending between the first and second radial walls. As shown, the first radial wall 16a defines a central aperture 16d and a plurality of apertures 16e for receiving one end of a pin 22, while the second radial wall 16b defines a central aperture 16f and a plurality of apertures 16g for receiving the opposite end of the pin 22.

[0055] As shown, each of the planetary gears 24 includes a first gear portion 24a and a second gear portion 24b, each defining a plurality of outwardly facing gear teeth. In one aspect, the first gear portion 24a is positioned closer to the differential case 14 than the second gear portion 24b. In one aspect, the first gear portion 24a has a larger diameter and a greater number of gear teeth than the second gear portion 24b. In the illustrated embodiment, the first gear portion 24a is axially separated from the second gear portion 24b by an extension portion 24c that lacks a gear or tooth portion. Thus, an axial gap exists between the first gear portion 24a and the second gear portion 24b. In one aspect, the first gear portion 24a can be referred to as the first stage 24a of the planetary gear 24, while the second gear portion 24b can be referred to as the second stage 24b of the planetary gear 24. Because the planetary gears 24 have two distinct gear sets, the planetary gear arrangement 50 can be referred to as a compound planetary gear arrangement 50.

[0056] As in Figure 5As best seen, the first gear portion 24a intermeshes with outwardly facing teeth 32a of a sun gear 32 which forms part of the planetary gear arrangement 50. In the embodiment shown, the sun gear 32 is an integrally formed part of the hollow drive shaft 28. However, other arrangements are possible, such as attaching a separately formed sun gear 32 to the hollow drive shaft 28. As shown, the hollow drive shaft 28 extends over the shaft half shaft 30a and may be, for example, an electric motor 70 (in Figure 8 Schematically shown) is a part of or connected to the electric motor. Figure 5 , the second gear portion 24b intermeshes with the inwardly facing teeth 34a of the ring gear 34. In one aspect, the ring gear 34 is mounted within the motor housing 12a such that the ring gear 24 is maintained in a fixed position relative to the motor housing 12a and, therefore, relative to the housing assembly 12. In some embodiments, the ring gear 34 is rotationally fixed in position by the interaction of outwardly facing splines provided on the ring gear 34 and inwardly facing splines provided on the housing 12a. In some embodiments, the ring gear 34 is rotationally fixed in position by a pin extending between the ring gear 34 and the housing 12a, such as a pin extending between the ring gear 34 and a crescent-shaped slot in the housing 12a.

[0057] With respect to the disclosed arrangement, it should be noted that the sun gear 32 and the ring gear 34 are axially offset from one another by a distance that is the axial distance between the gear portions 24a and 24b. With this arrangement, the sun gear 32 is characterized as being positionable axially between the ring gear 34 and the side gears 38a. On the same basis, the ring gear 34 is characterized as being spaced or offset axially from the sun gear 32 in a direction away from the side gears 38a and in a direction toward the electric motor 70. Figure 7 It can also be seen that the gear portions 24 b of the planetary gears 24 , which are arranged 120 degrees apart from each other, define an outer envelope D1 that is larger than the outer diameter D2 of the ring gear 34 . Figure 7 Also shown are three planet gears 24 and four pinion gears 48 that are offset from each other by equal angles. It should also be noted that the legs 16c of the planet carrier structure 16 are arranged 120 degrees apart from each other and are offset relative to the planet gears 24 so that the legs 16c extend from the planet gears 24 at an intermediate distance or angle. Return to Reference Figure 5 , it can be seen that the sun gear 32, planet gears 24 and ring gear 34 of the planetary gear arrangement 50 are disposed entirely within the interior volume defined by the housing 12a and are therefore all located on the same side of a plane passing through the junction between the housings 12a, 12b. Figure 5It can also be seen that the differential case 14 is completely contained within the interior volume of the housing 12b along with the pinion gears 48 and the side gears 38. Thus, the planetary gear arrangement 50 and the gears 24, 32, 34 of the differential gear arrangement can be disposed in different housings or compartments.

[0058] In operation, refer to Figure 8 As shown in the power flow diagram, the electric motor 70 drives the shaft 28 and the sun gear 32. The sun gear 32, in turn, meshes with and drives the first stage 24a of the planetary gears 24, and the torque is amplified by the ratio between the sun gear and the first stage 24a of the planetary gears 24. This same torque acts on the second stage 24b of the planetary gears 24 and the ring gear 34. When the ring gear 34 is rotationally fixed in position, this interaction transfers torque to the planetary carrier structure 16, which in turn drives the pinion shafts 40 and pinion gears 48 to transfer power to the side gears 38 and the axle half shafts 30. In the particular embodiment shown, an 8:1 gear ratio or reduction ratio is achieved between the motor shaft 28 and the axle half shafts 30. Other reduction ratios and gear ratios are possible without departing from the concepts herein.

[0059] The disclosed design provides many advantages. For example, a compact design with a high gear reduction ratio is provided. For example, assembly is easier even when the ring gear diameter is smaller than the outer profile of the first stage gear portion 24a of the planetary gear 24. In one advantageous method, the shaft 28 and the ring gear 34 are first installed in the housing 12a, and the planetary assembly 50 and the differential assembly 60 are provided as a complete subassembly, such as Figure 9 As shown, it is then mounted to the shaft 28 and ring gear 34 within the housing 12a, after which the housing 12b can be installed. The disclosed design also advantageously allows the planetary gear carrier to serve as the left housing of the differential assembly 10. In addition, lubrication is made easier because the planetary assemblies 50 and the differential assembly 60 are arranged in different compartments. The disclosed design also reduces the total number of components and therefore increases system reliability. Moreover, by providing a simple bearing support architecture for the planetary carrier 16 / case 14 structure, less deflection is generated. In addition, integrally forming the sun gear 32 into the shaft 28 minimizes or avoids problems associated with noise, vibration, and harshness (NVH).

[0060] Now refer to Figures 10 to 23 Various types of lubrication systems 200, 230, 240, 260 can be used with the differential assembly 10, 110. Exemplary suitable lubricants include oil. For convenience, the various lubrication systems shown herein are relative to Figures 5 to 9 The illustrated differential assembly 10 is shown in which the planetary gear arrangement 50 is held by the planet carrier 16 which is offset relative to the differential case 14. However, it will be understood that these lubrication systems can also be applied to Figures 1 to 4 The differential assembly 110 is provided.

[0061] In some implementations, the differential gear device 15 and the planetary gear device 50 share a lubrication system. However, in other implementations, the differential gear device 15 and the planetary gear device 50 have different lubrication systems. In some implementations, the lubrication system includes a forced circulation path along which lubricant (e.g., pressurized lubricant) circulates to the target area. In certain embodiments, the lubricant circulates continuously along the forced circulation path while the vehicle is operating. In some implementations, the forced circulation system is used only with the planetary gear device 50. In other implementations, the forced circulation system is also used with the differential gear device 15. In other implementations, the lubrication system includes a splash lubrication system in which the lubricant is directed to a chamber in which the lubrication system splashes onto components disposed within the differential chamber. In certain implementations, the lubrication system includes a hybrid system between a forced circulation system and a splash lubrication system.

[0062] Overall reference Figures 10 to 23 Each lubrication system 200, 230, 240, 260 includes an inlet passage 202 defined in the assembly cover 12b that leads from the motor housing 12a to the differential case 14. The inlet passage 202 directs lubricant (e.g., pressurized lubricant) to the interior chamber 45 of the assembly cover 12b where the differential case 14 is located. The lubricant will splash within the chamber 45, thereby providing lubrication between the differential case 14 and the assembly cover 12b. In some implementations, the assembly cover 12b defines an outlet passage 212 (e.g., see FIG. 1 ) that leads from the interior chamber 45 of the assembly cover 12b rearwardly to the motor housing 12a. Figure 12 、 Figure 16 and Figure 21 ).

[0063] The exemplary lubrication systems 200, 230, 240, 260 comprise forced circulation systems for use with at least the planetary gear set 50. The forced circulation systems include a series of passages (e.g., holes or other conduits) extending through the housing assembly 12 and the planet carrier 16. In some implementations, the first lubrication system 200, the second lubrication system 230, the third lubrication system 240, and the fourth lubrication system 260 comprise a first forced circulation system 202 for the planetary gear set 50. In certain implementations, the first forced circulation system 202 includes a bridge passage 214 that extends from the cavity 45 through the differential case 14, through the planet carrier 16, and to the planetary gear set 50. In certain implementations, the bridge passage 214 leads to at least the junction between the first gear portion 24a of each planet gear 24 and the sun gear 32.

[0064] In some implementations, each planet gear 24 is mounted to the planet carrier 16 via a pin 22 rigidly secured to the planet carrier 16 and the bearing assembly 26. In some such implementations, each pin 22 can define a pin passage 216 that leads from a bridge passage 214 to the second gear portion 24 b of the corresponding planet gear 24. In some implementations, one or more transverse paths 218 lead outward from the pin passage 216 to the bearing assembly 26 of the planet gear 24. In some implementations, the pin passage 216 passes through the pin 22 and leads to a distribution member 220 disposed at the end of the pin 22 opposite the differential case 14. In some embodiments, the distribution member 220 is a deflector 220 that deflects lubricant ejected from the pin passage 216 rearward toward the interface between the second gear portion 24 b of the corresponding planet gear 24 and the ring gear 34. In other embodiments, the distribution member 220 is a closed conduit that directs fluid toward the interface between the second gear portion 24 b and the ring gear 34. In certain implementations, the bridge passage 214 leads to the junction between the sun gear 32 and the first gear portion 24 a of each of the planet gears 24 .

[0065] In some implementations, some of the lubricating fluid flowing along the inlet passage 202 enters the differential case 14 rather than being directed to the planetary gear arrangement 50. For example, the lubricating fluid may flow along one or more apertures 222 defined in the differential case 14 (e.g., see FIG. Figure 14 In some implementations, lubricant enters the orifice 222 (see, e.g., FIG. 1 ) due to the high pressure induced in the region 45 of the housing by the seal 49 disposed in the housing chamber 45 to maintain lubrication pressure. Figure 11 In this implementation, the aperture 222 is smaller than the aperture 224 through which the pinion shaft 40 is accessible (see, e.g., Figure 17 In other implementations, due to the rotation of the differential case 14, lubricant enters the interior cavity 47 of the differential case 14 through the larger orifice 222 (see, for example, Figure 23 ).

[0066] Upon entering the differential case 14, the lubricant can splash around within the chamber 47, for example, reaching the thrust washer interface 57 between the side gears 38 and the differential case 14. In another embodiment, the splashed lubricant flows through an aperture 210 defined in the differential case 14 to reach the bearing apparatus 59 (e.g., a needle bearing apparatus) for one or more shafts 30 (e.g., see FIG. Figure 12In some implementations, the differential case 14 defines one or more apertures 208 that lead from the internal cavity 47 to the bearing device 55 (e.g., a ball bearing device) between the differential housing 14 and the assembly cover 12 b. In some implementations, splash fluid within the cavity 47 flows through the apertures 208 to the bearing device 55.

[0067] In certain implementations, one or more components of the differential gear apparatus 15 define passageways that allow lubricant to be directed to a target area of ​​the differential gear apparatus 15 (see, e.g., Figures 10 to 12 In some implementations, one or more pinion shafts 40 of the differential case 14 define a shaft passage 204 extending through the pinion shaft 40 and leading to an outlet passage 206 toward the center of the differential gear arrangement 15. The shaft passage 204 may be provided through an aperture 224 defined in the differential case 14 that is aligned with the pinion shaft 40 (e.g., see FIG. Figure 17 In some embodiments, the outlet passage 206 is angled relative to the shaft passage 204. In some embodiments, the outlet passage 206 directs lubricant toward the interface between the pinion gear 48 and the side gear 38.

[0068] In some embodiments, directing the lubricant along the shaft passage 204 creates a fluid jet that is then directed along the outlet passage 206 to spray outward onto a targeted area of ​​the differential gear set 15. For example, the lubricant is first directed along the shaft passage 204 toward a central location within the differential case 14. In some embodiments, due to the seal 49 between the housing 12 and the differential case 14 (e.g., see FIG. 2 ), the lubricant is directed toward a central location within the differential case 14. Figure 11 ) generates high pressure, the lubricant enters the rotating shaft passage 204. At or near the center, the lubricant then rotates at least 90 degrees relative to the shaft passage 204 and is directed along one or more outlet passages 206. In some embodiments, the lubricant rotates 120 to 160 degrees between the shaft passage 204 and the outlet passage 206. In some embodiments, the lubricant rotates approximately 135 degrees between the shaft passage 204 and the outlet passage 206.

[0069] In certain implementations, this concept of directing lubricating fluid first centrally and then outwardly to a target area can also be applied to the planetary gear apparatus 150 in a centrifugal assisted lubrication system (e.g., see Figures 18 to 20 In some implementations, the planet carrier 16 defines a well 242 at a location at or near the axis of rotation X of the differential case 14 (see, for example, Figure 18 and Figure 19 In some embodiments, the recess 242 forms a ring around one of the side gears 38 (see, for example, Figure 19A first radial path 246 leads radially inward from the bridge path 214 to the recess 242. A second radial path 243 leads radially outward from the recess 242 to the pin path 216 at the planet gears 24. The recess 242 is positioned near the rotational center of the differential 10. Therefore, the centrifugal force acting on the lubricant within the recess 242 is utilized to guide the lubricant radially inward and then radially outward along the radial paths 246 and 244, increasing the pressure of the lubricant. In certain implementations, a corresponding path 250 leads from the recess 242 to the junction between the sun gear 32 and the first portion 24a of each planet gear 24.

[0070] In some implementations, the lubrication system directs lubricant from the housing 12 through the differential case 14 to the planet carrier 16 to reach the planetary gear arrangement 50 (see, for example, FIG. Figures 10 to 20 However, in other implementations, the lubrication system 260 directs lubricant from the housing 12 directly to passages defined in the planet carrier 16 to reach the planetary gear system 50 (see, e.g., Figures 21 to 23 For example, passage 262 may branch from inlet passage 202 upstream of interior chamber 45 of housing 12 (see, e.g., Figure 22 ). Passage 262 leads to an aperture 264 through the planet carrier 216, which leads to the pin passage 216 of the planet gear 24 (see, for example, Figure 21 A port 264 through the planet carrier 216 is sealed from the differential case 14 by a seal (e.g., an O-ring, a gasket, a grommet, etc.) 266. In some implementations, a passage 268 through the planet carrier 16 also leads to the joint between the sun gear 32 and the first portion 24a of each planet gear 24.

[0071] As described above, various types of lubrication systems for the planetary gear set 50 can be mixed with various types of lubrication systems for the differential gear set 15 . Figures 10 to 12 A first exemplary lubrication system 200 is shown, comprising a forced lubrication system for the differential case 14 supplemented by a shaft passage 204 capable of forced lubrication of the differential gear set. The first lubrication system 200 also comprises a first type of forced lubrication system for the planetary gear set 50, wherein a bridge path 214 passes through the differential case 14.

[0072] Figures 13 to 17 A second exemplary lubrication system 230 is shown that utilizes the same forced lubrication system for the planetary gear set 50 as the first lubrication system 200. However, the second lubrication system 230 does not include the shaft passages 204. Instead, the second lubrication system 230 directs lubricant to the internal chamber 47 of the rotating differential case 14, where it can continuously splash around during rotation of the differential 10.

[0073] Figures 18 to 20 A third exemplary lubrication system 240 is shown, wherein a bridge path 214 leads from the differential case 14 to centrifugal paths 246, 242, 244 at the planet carrier 16 to help direct lubricant to the planetary gear set 50. In some implementations, the third lubrication system 240 has the same differential case lubrication system as the second lubrication system 230. In some implementations, the bridge paths 214 of the first lubrication system 200, the second lubrication system 230, and the third lubrication system 240 extend through the differential 14 and the planet carrier 16. For example, lubricant flows from the housing 12 into the internal chamber 45, through the differential case 14, to the planet carrier 16, and to the planetary gear arrangement 50.

[0074] Figures 21 to 23 A fourth exemplary lubrication system 260 is shown in which lubricant directed to the planetary gear set 50 is separated from lubricant directed to the differential case 14 upstream of the differential case 14. In this implementation, a continuous flow of lubricant is directed from the housing 12 to the planet carrier 16 and to the planetary gear set 50. In some such implementations, another continuous flow of lubricant is directed from the housing 12 to the differential case 14. In other such implementations, a predetermined amount of lubricant is trapped within the chamber 45 between the differential case 14 and the housing 12.

[0075] For purposes of this application, directional terms (e.g., "left," "right," "up," "down," "upward," and "downward," etc.) are intended to reference and be described relative to the orientation shown in the accompanying figures for clarity, but embodiments as practiced and included within the scope of the claims may include embodiments in which systems and devices are in different orientations.

[0076] Although specific applications of the technology have been shown and discussed above, the disclosed technology can be used with a variety of environments according to many embodiments of the technology. The above discussion is not meant to suggest that the disclosed technology is only suitable for implementation within the environment shown and described above.

[0077] This disclosure describes certain aspects of the technology with reference to the accompanying drawings, of which only some of the possible aspects are shown. However, other aspects can be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Rather, these aspects are provided to make this disclosure thorough and complete and to fully convey the scope of possible aspects to those skilled in the art.

[0078] As should be understood, the various aspects described herein with reference to the accompanying drawings are not intended to limit the present technology to the specific aspects described. Therefore, additional configurations can be used to practice the technology herein and / or some aspects described can be excluded without departing from the methods and systems disclosed herein.

[0079] Although specific aspects are described herein, the scope of the present technology is not limited to those specific aspects. Those skilled in the art will recognize other aspects or improvements within the scope of the present technology. Therefore, specific structures, actions, or operations are disclosed only as illustrative aspects. The scope of the present technology is defined by the appended claims and any equivalents thereof.

Claims

1. A reduction drive unit, comprising: a) a differential device comprising a differential case housing a plurality of pinion gears meshing with a pair of side gears; as well as b) A compound planetary gear apparatus comprising a sun gear, a ring gear, and a plurality of planet gears, wherein each of the plurality of planet gears has a first stage gear intermeshing with the sun gear and an axially offset second stage gear intermeshing with the ring gear, the ring gear being fixed relative to the differential case.

2. The reduction drive unit according to claim 1, wherein: The ring gear is axially offset relative to the sun gear such that the sun gear is positioned between the ring gear and the differential device in an axial direction.

3. The reduction drive unit according to claim 1, wherein: The differential case serves as a planet carrier for the planetary gears.

4. The reduction drive unit according to claim 1, wherein: The compound planetary gear apparatus includes a planet carrier structure that rotationally supports the plurality of planet gears, the planet carrier structure being rigidly mounted to the differential case.

5. The reduction drive unit according to claim 1, wherein: The plurality of planetary gears includes three planetary gears.

6. The reduction drive unit according to claim 5, wherein: The plurality of pinion gears includes three pinion gears.

7. The reduction drive unit according to claim 5, wherein: The plurality of pinion gears includes four pinion gears.

8. The reduction drive unit of claim 1 further comprising a hollow drive shaft for connection to the electric motor, the hollow drive shaft extending over and coaxially aligned with one of a pair of half-shafts, each half-shaft being coupled to one of the side gears.

9. The reduction drive unit according to claim 8, wherein: The sun gear and the hollow drive shaft are formed together.

10. The reduction drive unit according to claim 8, wherein: The sun gear is coupled to the hollow drive shaft.

11. The reduction drive unit of claim 1 , further comprising a gear reduction housing comprising a first housing portion coupled to a second housing portion, wherein: The differential apparatus is entirely contained within the first housing portion, and wherein the sun gear, the ring gear, and the plurality of planet gears are entirely contained within the second housing portion.

12. The reduction drive unit according to claim 1, further comprising a lubricant forced circulation passage along which lubricant is pumped to the compound planetary gear device during operation of the reduction drive unit.

13. The reduction drive unit according to claim 12, wherein: The lubricant forced circulation passage also extends through the differential device.

14. The reduction drive unit according to claim 13, wherein: The lubricant forced circulation passage includes a hole defined in the differential case to enable lubricant to splash inside the differential case.

15. The reduction drive unit according to claim 14, wherein: The lubricant forced circulation passage includes a hole passing through the pinion gear, the hole leading from the inside of the differential case to the center of the differential device.

16. The reduction drive unit according to claim 12, wherein: When the lubricant forced circulation passage extends to the planetary gear device, the lubricant forced circulation passage bypasses the differential device.

17. The reduction drive unit according to claim 12, wherein: The lubricant forced circulation passage includes a hole passing through a pin of the planetary gear of the compound planetary gear device.

18. The reduction drive unit according to claim 12, wherein: The lubricant forced circulation passage includes a centrifugal assisted lubrication system in which lubricant is directed to a central recess defined by the planet carrier and then directed to the planet gears.

19. A reduction drive unit, comprising: a) a differential device comprising a differential case housing a plurality of pinion gears meshing with a pair of side gears; as well as b) A compound planetary gear apparatus comprising a sun gear, a fixed ring gear, a plurality of planetary gears, and a planet carrier structure rotatably supporting the plurality of planetary gears, wherein: i) the planet carrier structure is rigidly mounted to the differential case; ii) each of the plurality of planetary gears has a first stage gear intermeshing with the sun gear and an axially offset second stage gear intermeshing with the fixed ring gear; and iii) The ring gear is axially offset relative to the sun gear so that the sun gear is positioned between the ring gear and the differential device in the axial direction.

20. A reduction drive unit, comprising: a) a housing assembly comprising a first housing portion mating with a second housing portion; b) a differential arrangement comprising a differential case housing a plurality of pinion gears intermeshing with a pair of side gears, said differential arrangement being entirely housed within said first housing portion; as well as c) A compound planetary gear apparatus comprising a sun gear, a fixed ring gear, a plurality of planetary gears, and a planet carrier structure rotatably supporting the plurality of planetary gears, wherein: iv) the planet carrier structure is rigidly mounted to the differential case; v) each of the plurality of planetary gears has a first stage gear intermeshing with the sun gear and a second stage gear intermeshing with the fixed ring gear; and vi) The sun gear, the fixed ring gear and the plurality of planet gears are completely housed within the second housing portion.

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