Electric drive module with a gearbox having parallel double gear pairs for distributing load to a final drive gear

Abstract

Electric drive module (24) with: an electric motor (42); a differential assembly (46); a transmission (44) that transmits rotational power between the electric motor (42) and the differential assembly (46); a housing (40) in which the transmission (22) and the differential assembly (46) are accommodated; wherein the transmission (44) includes a first reduction gear and a second reduction gear, the first reduction gear having a drive gear (60) and a pair of first reduction gears (62), the drive gear (60) being rotatable about a first axis (58), each of the first reduction gears (62) being engaged with the drive gear (60) and rotatable about a respective second axis (74), wherein the second axes (74) are spaced apart from each other and parallel to the first axis (58), wherein the second reduction comprises an output gear (66) and a pair of second reduction gears (64), wherein the output gear (66) is rotatable about a third axis (76) which is parallel to the first axis (58), wherein each of the second reduction gears (64) is engaged with the output gear (66) and non-rotatably coupled to an associated one of the first reduction gears (62); wherein the electric drive module (24) further comprises: a pair of parking gears (202), each of the parking gears (202) being non-rotatably coupled to a corresponding one of the second reduction gears (64); a pawl (204) having a pair of pawl teeth (222), the pawl (204) being coupled to the housing (40) and pivotable between an engaged position in which each of the pawl teeth (222) engages a corresponding one of the parking gears (202), and a disengaged position in which the pawl teeth (222) are disengaged from the parking gears (202); and a pair of pistons (206) movable between a first position and a second position, each of the pistons (206) having a first body portion (232) and a second body portion (236) smaller in diameter than the first body portion (232), wherein contact between the first body portion (232) of the pistons (206) and the pawl (204) positions the pawl (204) in the engaged position, and wherein the pawl (204) is disposed in the disengaged position when the second body portion (236) of the pistons (206) contacts the pawl (204).

Description

FIELD OF INVENTION

[0001] The present disclosure relates to an electric drive module having a transmission including parallel gear pairs that distribute the load to a final drive gear. BACKGROUND

[0002] This section provides background information related to the present disclosure that is not necessarily prior art.

[0003] It is known in the art to provide an electric drive module having an electric motor that drives a differential assembly via a transmission. Known electric drive module configurations may include a coaxial arrangement in which the electric motor output shaft, the differential assembly, and the input and output of the transmission are arranged about a common axis of rotation, or an arrangement in which the electric motor output shaft, the differential assembly, and the input and output of the transmission are arranged about two or more axes of rotation that are parallel to each other. Although such configurations are well suited for their intended purpose, they may be somewhat difficult to package or install in certain vehicles because there may not be enough space in a lateral, side-to-side, or radial direction.Accordingly, there is still a need in the field for an electric drive module that is relatively compact.

[0004] Such electric drive modules are known, for example, from the document JP 2019 173 833 A and the document CN 201 118 356 Y. From the document DE 10 2016 111 685 A1, a parking mechanism with a parking gear, a pawl, a rod, a cam, and a spring of an automatic transmission for motor vehicles is known. SUMMARY

[0005] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its entire scope or all of its features.

[0006] In one form, the present disclosure provides an electric drive module including an electric motor, a differential assembly, and a transmission that transmits rotational power between the electric motor and the differential assembly. The transmission has first and second reduction gears. The first reduction gear includes a drive gear rotatable about a first axis and a pair of first reduction gears rotatable about a respective second axis, each of which is meshed with the drive gear. The second axes are spaced apart from each other and parallel to the first axis. The second reduction gear includes an output gear and a pair of second reduction gears. The output gear is rotatable about a third axis parallel to the first axis.Each of the second reduction gears is engaged with the output gear and non-rotatably coupled to an associated one of the first reduction gears.

[0007] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. DRAWINGS

[0008] The drawings described herein are intended to illustrate selected embodiments only and not all possible implementations and are not intended to limit the scope of the present disclosure. Fig. 1 is a schematic illustration of an exemplary vehicle having an electric drive module constructed in accordance with the teachings of the present disclosure; Fig. 2 is a perspective, partially fragmented section of the electric drive module of Fig. 1, which illustrates an electric motor and a gearbox in more detail; Fig. 3 is a cross-sectional view of a portion of the electric drive module of Fig. 1, illustrating a transmission final drive gear and a differential assembly; Fig. Figure 4 is a schematic illustration of a portion of the electric drive module of Fig. 1, which illustrates the relative positioning of the electric motor, transmission and differential assembly; Fig. 5 is a perspective view of a portion of the electric drive module of Fig. 1, illustrating an optional parking lock mechanism; Fig. 6 is a plan view of a portion of the parking lock mechanism illustrating a pawl disposed in engagement with a pair of parking gears to lock the countershafts of the electric drive module; Fig. 7 is a sectional view taken through a portion of the parking lock mechanism, the view illustrating a cam disc aligned in a first rotational position and a pair of pistons disposed in an extended position; Fig. 8 is a perspective view of a portion of the parking lock mechanism illustrating the pawl disengaged from a pair of parking gears to permit rotation of the countershafts of the electric drive module; Fig. 9 is a sectional view taken through a portion of the parking lock mechanism, the view illustrating the cam disc oriented in a second rotational position and a pair of pistons disposed in a retracted position; Fig. 10 is a partially sectioned perspective view of the parking lock mechanism; Fig. 11 is a perspective view of a portion of the parking lock mechanism illustrating a first surface of the cam disc in more detail; Fig. 12 is a sectional view of a portion of the parking lock mechanism illustrating a lock actuator in more detail; Fig. 13 is a perspective view of a portion of the cam disc illustrating a locking aperture formed in a second surface of the cam disc; and

[0022] Fig. 14 is a perspective view of a portion of the parking lock mechanism illustrating the pistons in the extended position and the pawl in the engaged position.

[0009] Matching reference numbers indicate matching parts throughout the different views of the drawings. DETAILED DESCRIPTION

[0010] With reference to Fig. 1 of the drawings: An exemplary vehicle having a drive module constructed in accordance with the teachings of the present disclosure is indicated generally by the reference numeral 10. The vehicle 10 may include a front or primary driveline 14 and a rear or secondary driveline 16. The front driveline 14 may include an internal combustion engine 18 and a transmission 20 and may be configured to drive a front or primary set of drive wheels 22. The rear driveline 16 may include an electric drive module 24, which may be configured to drive a rear or secondary set of drive wheels 26 as needed or "on demand."Although in the present example the front wheels 22 belong to the primary driveline 14 and the rear wheels 26 belong to the secondary driveline 16, it should be understood that alternatively the rear wheels could be driven by the primary driveline and the front wheels could be driven by the secondary driveline. Although the electric drive module 24 is indicated in this example as being configured to drive a secondary drive wheel set on a temporary basis, it should also be understood that a drive module constructed in accordance with the present teachings could be used to drive a (front, rear, or other) drive wheel set (e.g., a front set of wheels) on a full-time basis, either as the sole drive means for the vehicle or in conjunction with other drive means. The electric drive module 24 may include a drive unit 30 and a pair of axle shafts 32.

[0011] With reference to Fig. 2 and Fig. 3: The drive unit 30 may include a housing 40, an electric motor 42, a transmission 44, and a differential assembly 46. The housing 40 may define a structure to which the other components of the drive unit 30 are mounted. The housing 40 may be formed from two or more housing members that may be rigidly coupled together, such as via a plurality of threaded fasteners. The electric motor 42 may be any type of electric motor, such as a permanent magnet motor. The electric motor 42 may be mounted on a flange (not specifically shown) on the housing 40 and may have an output shaft 56 that is rotatable along a first axis of rotation 58 ( Fig. 4) and is accommodated in the housing 40.

[0012] With reference to Fig. 2 and Fig. 4: The transmission 44 may include one or more gear stages or reductions providing a transmission input driven by the output shaft of the electric motor 42 and a transmission output driving the differential assembly 46. The transmission 44 may include one or more gear stages or reductions providing multiple stages of gear reductions and may optionally include one or more multi-speed gear stages. A clutch (not shown) may also optionally be interposed between the transmission output and the differential assembly 46 to selectively decouple the differential assembly 46 from the electric motor 42. In the example provided, the transmission 44 includes a drive gear or input pinion 60, a plurality of first reduction gears 62, a plurality of second reduction gears 64, and an output gear or final drive gear 66.The input pinion 60 may be coupled to the output shaft of the electric motor 42 for rotation therewith. The first reduction gears 62 are engaged with the input pinion 60, have more teeth than the input pinion 60, and have a pitch diameter that is relatively larger than the pitch diameter of the input pinion 60. Each of the first reduction gears 62 may be fixedly coupled to a corresponding one of the second reduction gears 64 to form a compound reduction gear 70. The second reduction gears 64 are larger in pitch diameter and have more teeth than the first reduction gears 62. Each of the compound reduction gears 70 may be arranged for rotation about a second axis of rotation 74 that is parallel to and offset from the first axis of rotation 58 on a countershaft or axle 72 mounted on the housing 40.Each of the countershafts 72 may be supported by a pair of bearings that may be mounted on the housing 40. It should be understood that each of the countershafts 72 may be formed as a discrete component that may be mated with a corresponding one of the compound reduction gears 70, or it may be formed integrally and integrally with a corresponding one of the compound reduction gears 70. The final drive gear 66 may be supported by the housing 40 for rotation about an output axis 76 that is parallel to and offset from the second rotational axis 74 and the first rotational axis 58.In the example provided, the input pinion 60, the first reduction gears 62, the second reduction gears 64, and the final drive gear 66 are helical gears, with the first reduction gears 62 and the second reduction gears 64 counter-rotating to balance axial forces on the compound reduction gears 70 associated with the transfer of rotational power between the input pinion 60 and the first reduction gears 62 and between the second reduction gears 64 and the final drive gear 66. Although the transmission 44 has been described as employing helical gears, it should be understood that some or all of these gears could be constructed as spur gears.

[0013] With reference to Fig. 3: The differential assembly 46 may include a differential input component and a pair of differential output components. The differential input component may be coupled to the final drive gear 66 for rotation therewith about the output axis 76, while each of the differential output components may be coupled for rotation with a corresponding one of the axle shafts 32. In the particular example provided, the differential assembly 46 includes a differential case 80 and a differential gear set 82. The differential case 80 may function as the differential input component and may be supported on the housing 40 for rotation about the output axis 76 by a pair of bearings 84. The bearings 84 are illustrated in the provided example as being tapered roller bearings, however, it should be understood that the bearings 84 could alternatively be configured as angular contact ball bearings or as ball bearings.The differential gear set 82 may include a pair of differential pinion gears 90 and a pair of side gears 92. The differential pinion gears 90 may be received within the differential case 80 and are rotatably disposed on a crosspin 94 mounted to the differential case 80. The crosspin 94 may extend at least partially through the differential case 80 and is oriented perpendicular to the output axis 76. The side gears 92 are, in the example provided, the differential output components. The side gears 92 are received within the differential case 80 and are rotatable relative to the differential case 80 about the output axis 76. Each of the side gears 92 is engaged with the differential pinion gears 90.

[0014] Each of the axle shafts 32 may be non-rotatable, but may be axially slidably engaged with a corresponding one of the side gears 92. In the example provided, each of the axle shafts 32 includes a toothed segment 100 that mateably engages an internally toothed opening 102 in a corresponding one of the side gears 92. Each of the axle shafts 32 is configured to transmit rotational power between one of the side gears 92 and an associated one of the vehicle wheels.

[0015] The design of the transmission 44 is advantageous in several aspects. For example, the compound reduction gears 70 allow the use of a relatively high-speed electric motor and a relatively small input pinion, which reduces the peripheral speed and thus positively impacts the bending stress, load capacity, and service life of the input pinion 60 and the first reduction gears 62. As another example, the load on the final drive gear 66 is distributed across the second reduction gears 64, allowing a reduction in the size of the second reduction gears 64 (as opposed to an arrangement where the entire load is transferred through a single gear into the final drive gear 66).Consequently, the arrangement of the gear train between the electric motor 42 and the final drive gear 66 allows for a reduction in the assembly size of the drive unit 30, and furthermore, these gears can be relatively smaller and / or formed of less expensive materials than components of the known electric drive units, thus reducing the cost and mass of the electric drive module 24.

[0016] If desired, a parking lock mechanism (not shown) may be integrated into the electric drive module 24. Referring to Fig. 2 and Fig. 4: The parking lock mechanism could be configured in a conventional manner with a pawl pivotally coupled to the housing 40, a toothed ratchet gear rotatably coupled to the final drive gear 66, or a component of the differential assembly 46 rotatable about the output axis 76. The pawl can be pivoted into and out of engagement with the teeth of the toothed ratchet gear to block rotation of the final drive gear 66 relative to the housing 40. Alternatively, the parking lock mechanism could be configured to selectively lock the countershafts 72 to the housing 40. A scissor mechanism or a rocker arm mechanism could be employed to simultaneously lock the countershafts 72 to the housing 40.

[0017] With reference to Fig. 5 to 7: An optional parking lock mechanism 200 may be integrated into the drive unit 30. The parking lock mechanism 200 may include a pair of parking gears 202, a pawl 204, a pair of pistons 206, a pair of piston bias springs 208, and an actuator 210.

[0018] Each of the parking gears 202 may be non-rotatably coupled to an associated one of the countershafts 72 and may define a plurality of teeth 216 and a plurality of recesses 218. Each of the recesses 218 is disposed between a respective pair of the teeth 216.

[0019] The pawl 204 includes a pawl body 220 and a pair of pawl teeth 222 disposed at opposite ends of the pawl body 220. The pawl body 220 is pivotally coupled to the housing 40 of the drive unit 30 so that the pawl 204 can be moved between an engaged position ( Fig. 6), in which each of the pawl teeth 222 engages a corresponding one of the parking gears 202 (ie, each pawl tooth 222 is received in a recess 218 in a corresponding one of the parking gears 202) to thereby rotatably lock the parking gears 202 and the countershafts 72 to the housing 40, and a disengaged position ( Fig. 8), in which each of the pawl teeth 222 clears the teeth 216 on the associated one of the park gears 202 so that the pawl 204 does not block rotation of the park gears 202 or the countershafts 72 relative to the housing 40. In the example provided, a pivot axis 226 is mounted to the housing 40 and extends through the pawl 204 and into the actuator 210. The pawl 204 may be received somewhat loosely on the pivot axis 226 to ensure that the load transmitted via the park lock mechanism 200 is evenly distributed from the park gears 202 as well as evenly distributed from the pawl gears 222. The pawl 204 may be biased about the pivot axis 226 toward a desired rotational position, such as the disengaged position.In the example provided, a helical torsion spring 258 is disposed about the pivot axis 226 and is engaged with the housing 40 and the pawl body 220.

[0020] With reference to Fig. 7: Each of the pistons 206 may include a piston body with a guide portion 230, a first body portion 232, a transition portion 234, and a second body portion 236. The guide portion 230 may be disposed on a first axial end of the piston 206 and may be cylindrically shaped with a first diameter. The first body portion 232 may be disposed between the guide portion 230 and the transition portion 234 and may be sized in a desired manner. For example, the first body portion 232 could be generally cylindrically shaped with a desired diameter, such as the first diameter.In the example provided, the first body portion 232 is frusto-conical with a base (with the first body portion 232 intersecting the guide portion 230) having a diameter equal to the first diameter and a relatively shallow taper angle that causes the outer surface of the first body portion 232 to taper inwardly toward the central axis of the piston 206 between the guide portion 230 and the transition portion 234 by a desired amount, such as 2 degrees to 30 degrees, preferably 5 degrees to 15 degrees.

[0021] The second body portion 236 may also be cylindrically shaped, but has a second diameter that is smaller than the first diameter. The transition portion 234 may be frustoconically shaped so that it tapers between the first and second body portions 232 and 236. A spring opening 240 may be formed in the first axial end of the piston 206 and is sized to receive a corresponding one of the piston biasing springs 208 therein. In the example provided, each of the piston biasing springs 208 is a helical compression spring, however, it is understood that other spring types could be used instead of or in addition to a helical compression spring.

[0022] Each piston 206 and each piston biasing spring 208 is received within a piston opening 244 in the housing 40. In the example shown, the housing 40 includes an optional pair of piston bushings 246, which may be formed from a suitable material, such as hardened steel. Each of the piston bushings 246 defines a piston opening 244 sized to receive the first body portion 232 of a corresponding one of the pistons 206 and a corresponding one of the piston biasing springs 208. The piston opening 244 may be a blind hole such that the piston bushing 246 defines an inner wall 248 against which an end of the corresponding one of the piston biasing springs 208 may abut.

[0023] Each of the pistons 206 is movable along its longitudinal axis relative to the housing 40 between an extended position (shown in Fig. 6 & 7), in which the first body portion 232 of each of the pistons 206 is disposed in a rotational path of the pawl body 220, and a retracted position (shown in Fig. 8 & 9). To position the pistons 206 in an extended position, the pawl teeth 222 must be engaged with the parking gears 202. If the outer surface of the first body portion 232 is tapered (truncated conical), the piston biasing springs 208 will urge the pistons 206 outward from the piston openings 244 so that the outer surface of the first body portion 232 of each piston 206 contacts the pawl body 220. With the pistons 206 in their retracted positions, the pawl 204 can be rotated to the disengaged position via the torsion spring 258. The pawl 204 can contact the second body portion 236 of one or both pistons 206 when the pawl 204 is in the disengaged position.

[0024] With reference to Fig. 7 and Fig. 10: The actuator 210 is configured to control movement of the pistons 206 between the extended and retracted positions. The actuator 210 may include a pair of cam followers 250, an actuator hub 252, a cam disc 254, a bearing 256, a torsion spring 258, a rotary actuator 260, and a locking actuator 262.

[0025] With reference to Fig. 7 and Fig. 9: Each of the cam followers 250 may be arranged linearly with a corresponding one of the pistons 206. In the example provided, each of the cam followers 250 is integrally formed with a corresponding one of the pistons 206. In particular, the cam follower 250 may be a spherical radius at a second axial end of the piston 206, which is opposite the first axial end.

[0026] The actuator hub 252 may be fixedly coupled to the housing 40, concentrically about the axis about which the pawl 204 pivots. In the example provided, the actuator hub 252 is press-fitted onto the pivot axis 226. The actuator hub 252 may include a central portion 270, a bearing retainer 272, and a locking actuator retainer 274. The central portion 270 may define a pivot axis opening 280 and a threaded opening 282 aligned along a common axis. The pivot axis opening 280 is formed by a first axial side of the central portion 270 and is sized to engage the pivot axis 226 in a press-fitted manner. The threaded opening 282 is formed by a second, opposite axial side of the central portion 270.The bearing retainer 272 is concentrically disposed about the central portion 270 and may be coupled to the central portion 270 by a flange member 284 or, alternatively, by a plurality of spokes or webs. The bearing retainer 272 includes an outer peripheral surface 286, a shoulder 288 extending radially outward from the outer peripheral surface, and a retaining ring groove 290 formed in the outer peripheral surface 286. The locking actuator retainer 274 may have a bean-shaped (i.e., a kidney bean) configuration, best illustrated in FIG. Fig. 5, and may be fixedly coupled to (e.g., formed integrally with) the bearing support 272 so as to be radially offset from the central portion 270.

[0027] With reference to Fig. 5, Fig. 7 and Fig. 11: The cam disc 254 may include an annular disc 300, a gear portion 302, a torsion spring retainer 304, and a pair of sensor targets 306a, 306b. The annular disc 300 may be formed from a suitable material. The annular disc 300 may have an inner circumferential surface 310 and may define a pair of lobes 312. Each of the lobes 312 is formed in a first surface of the annular disc 300 that faces toward the cam followers 250 and the pistons 206. Each of the lobes 312 may be a circumferentially extending groove in the first surface of the annular disc 300. Each of the lobes 312 may be located between a first circumferential end 320 ( Fig. 11) of the groove where the groove is at its deepest, and a second opposite circumferential end 322 ( Fig. 11) of the groove where the groove is shallowest. Each of the cam followers 250 can be received in a corresponding one of the cams 312 (i.e., grooves) such that rotation of the cam disc 254 about an axis about which the pawl 204 pivots causes a corresponding linear movement of the pistons 206. In particular, the placement of a cam follower 250 in the deepest part of a corresponding one of the cams 312 (i.e., the first circumferential end 320 of the groove forming the corresponding one of the cams 312), as shown in Fig. 7, a corresponding one of the piston biasing springs 208 urges the associated one of the pistons 206 into its extended position, while positioning a cam follower 250 in the flattest part of an associated one of the cams 312 (i.e., the second circumferential end of the groove forming the associated one of the cams 312), as shown in Fig. 9, positions a corresponding one of the pistons 206 against the bias of the corresponding one of the piston biasing springs 208 into its retracted position. The gear portion 302 may include a plurality of gear teeth that may be fixedly coupled to the annular disc 300 such that the gear teeth are concentric with the inner circumferential surface 310. In the example provided, the gear teeth are formed integrally and integrally with the annular disc 300. The gear teeth may be disposed around the entire circumference of the annular disc 300, as shown in the example provided, or they could be formed on a sector of the annular disc 300. The torsion spring retainer 304 may be a cylindrical pin or boss that may extend from a second surface of the annular disc 300 opposite the first surface.Each of the sensor targets 306a, 306b may be mounted on the annular disk 300 and is configured to be scanned by a sensor 328 (. Fig. 10) when the cam disc 254 is in a predetermined rotational position relative to the housing 40. In the example provided, each of the sensor targets 306a, 306b is a magnet, and the sensor 328 is a Hall-effect sensor coupled to the housing 40.

[0028] With reference to Fig. 7: The bearing 256 is configured to support the cam disc 254 for rotation relative to the actuator hub 252. The bearing 256 may include an inner bearing race 330, an outer bearing race 332, and a plurality of bearing elements 334 received between the inner and outer bearing races 330 and 332. The inner bearing race 330 may be received on the outer peripheral surface 286 of the bearing retainer 272 and abut against the shoulder 288. If desired, the inner bearing race 330 may be pressed onto the outer peripheral surface 286 of the bearing retainer 272. An outer retaining ring 336 may be received in the retaining ring groove 290 and may block axial movement of the inner bearing race 330 on the actuator groove 252 in a direction away from the shoulder 288. The outer bearing race 332 may be coupled to the cam disc 254 in any desired manner.For example, the outer bearing race 332 could be pressed or bonded to the inner circumferential surface 310 of the annular disc 300. In examples where the annular disc is formed from a plastic material, the annular disc 300 could alternatively be overmolded onto the outer bearing race 332, such that the outer bearing race 332 is firmly bonded to the annular disc 300.

[0029] With reference to Fig. 5 and Fig. 7: The torsion spring 258 may be wrapped around the central portion 270 and may include a first follower 340 that may oppose the actuator groove 252 and a second follower 342 that may oppose the torsion spring retainer 304 on the cam plate 254. In the example provided, the first follower 340 is received in a hole formed in the flange member 284. The torsion spring 258 may be attached to the central portion 270 via a washer 346 and a threaded fastener 348 that is threaded to the threaded opening 282 in the central portion 270. The torsion spring 258 is configured to rotationally bias the cam disc 254 about its rotational axis toward a first rotational position, which may be a position that aligns the lowest part of the cams 312 with the cam followers 250.Alternatively, the torsion spring 258 could be designed to rotationally bias the cam disc 254 about its rotational axis into a position in which the flattest part of the cams 312 is aligned with the cam followers 250.

[0030] With reference to Fig. 10: The rotary actuator 260 is configured to control the rotation of the cam disc 254 about its rotational axis between the first rotational position and a second rotational position. The rotary actuator 260 may include a rotary electric motor (not specifically shown) and an output pinion (not specifically shown) engaged with the gear teeth of the gear portion 302 of the cam disc 254. The electric motor may be coupled (e.g., mounted) to the housing 40. The output pinion may be driven by the electric motor, either directly (e.g., the output pinion is mounted on an output shaft of the electric motor) or via a transmission (not shown) having one or more gears (not shown) arranged in a power transmission path between the electric motor and the output pinion.

[0031] The electric motor may be operated to drive the cam 254 to the second rotational position, which may be a position that aligns an opposite circumferential end of the cams 312, such as the flattest portion of the cams 312, with the cam followers 250. In some forms, the electric motor may be employed to drive the cam 254 to the desired rotational position and thereafter maintain the cam 254 in that rotational position. Optionally, the cam 254 may be configured with a stop member (not shown) that abuts a mating stop component (not shown) coupled to the housing 40 when the electric motor rotates or drives the cam 254 to the desired rotational position.However, in the example provided, the sensor target 306b, the sensor 328, and the locking actuator 262 are used to maintain the cam disc 254 in the desired rotational position, so that electrical power to the electric motor does not need to be maintained.

[0032] The placement of the cam 254 in both the first and second rotational positions can be sensed by the sensor 328, and the sensor 328 can generate a corresponding sensor signal in response. For example, the placement of the cam 254 in the first rotational position aligns the sensor target 306a with the sensor 328, and the sensor 328 generates a first sensor signal in response, while the placement of the cam 254 in the second rotational position aligns the sensor target 306b with the sensor 328, and the sensor 328 generates a second sensor signal in response. In response to receiving the second sensor signal, a controller (not shown) can control the locking actuator 262 to engage the locking actuator 262 with the cam 254 to prevent rotation of the cam 254 from the second rotational position (i.e.due to the moment applied to the cam disc 254 by the torsion spring 258).

[0033] With reference to Fig. 10 and Fig. 12: The locking actuator 262 may include any means for blocking the rotation of the cam disc 254 relative to the housing 40. In the example provided, the locking actuator 262 includes a solenoid assembly 400 and a locking port 402. The solenoid assembly 400 may be coupled to the housing 40 and may include a solenoid 410, a solenoid piston 412, and a solenoid spring 414. The solenoid piston 412 is movable within the solenoid 410 between an extended or latched position and a retracted or unlatched position. The solenoid spring 414 biases the solenoid piston 412 to the extended or latched position. The locking opening 402 is formed in the second surface of the annular disc 300 and is configured to receive the solenoid piston 412 therein when the cam disc 254 is in the second rotational position.In the example shown, the solenoid piston 412 has a tip 420 defined by a spherical radius, and the latch opening 402 has a frustoconical sidewall 422. The contour of the tip 420 of the solenoid piston 412 and the sidewall 422 of the latch opening 402 allows the solenoid piston 412 to be driven toward the retracted or unlatched position via the torsion spring 258 when no electrical power is provided to the solenoid 410 or the electric motor.

[0034] With reference to Fig. 5, Fig. 7 and Fig. 12: When no electrical power is supplied to the electric motor or the solenoid 410 during operation of the drive unit 30, the torsion spring 258 biases the cam disc 254 into the first rotational position in which the deepest part of the cams 312 is aligned with the cam followers 250, as shown in the Fig. 7, so that the pistons 206 are arranged in their extended positions so that the first body portions 232 contact the pawl body 220 and the pawl 204 is arranged about the pivot axis 226 so that the pawl teeth 222 engage the parking gears 202, as shown in Fig. 6. Under this condition, the countershafts 72 are effectively non-rotatably locked to the housing 40, and due to the design of the park lock mechanism 200, the load transmitted across each pawl tooth 222 and each park gear 202 is equal. Under this condition, the sensor target 306a is aligned with the sensor 328 so that the sensor 328 generates the first sensor signal in response. The first sensor signal may be received by a controller (not shown) and used to determine that the cam disc 254 is in a rotational position that causes the park lock mechanism 200 to lock the countershafts 72 to the housing 40. The solenoid spring 414 of the lock actuator 262 biases the tip 420 of the solenoid piston 412 against the second surface of the annular disc 300.

[0035] To unlock the countershafts 72 from the housing 40 to permit rotation of the countershafts 72 relative to the housing 40, electrical power may be applied to the electric motor to drive the output pinion to cause corresponding rotation of the cam disc 254 about its rotational axis in a first rotational direction. The rotation of the cam disc 254 in the first rotational direction increasingly aligns flatter portions of the grooves or lobes 312 with the cam followers 250, as shown in Fig. 9, which causes the pistons 206 to move from their extended positions to their retracted positions. Due to the tapered shapes of the first body portion 232 and the transition portion 234 of the pistons 206, as well as the moment applied to the pawl 204 by the torsion spring 258, the pawl teeth 222 are increasingly moved away from the teeth 216 of the parking gears 202 as the pistons 206 increasingly move to their retracted positions. The placement of the pawl 204 in contact with the second body portions 236 of the pistons 206, as shown in Fig. 8 and Fig.9, positions the pawl teeth 222 away from the park gears 202 to a position where the park gears 202, and consequently the countershafts 72, are able to rotate freely relative to the housing 40. Further rotation of the cam disc 254 in the first rotational direction positions the cam disc 254 to the second rotational position, which aligns the sensor target 306b with the sensor 328 such that the sensor 328 generates the second sensor signal in response. In response to receiving the second sensor signal, the controller may provide electrical power to the solenoid 410 to drive the solenoid piston 412 into the locking opening 402 and maintain the solenoid piston 412 in that position. Optionally, the controller may also discontinue the supply of electrical power to the motor.The torque applied to the cam disc 254 by the torsion spring 258 to urge the cam disc 254 toward the first rotational position is not sufficient to drive the solenoid piston 412 out of the locking opening 402 when electrical power is supplied to the solenoid 410.

[0036] To relock the countershafts 72 to the housing 40 to prevent rotation of the countershafts 72 relative to the housing 40, the supply of electrical power to the solenoid 410 is terminated. The torque applied to the cam 254 by the torsion spring 258 to urge the cam 254 toward the first rotational position is sufficient to overcome the force applied by the solenoid spring 414 to the solenoid piston 412 and drive the solenoid piston 412 out of the locking opening 402. The torque applied by the torsion spring 258 to the cam 254 causes the cam 254 to rotate in a second rotational direction opposite the first rotational direction.Rotation of the cam 254 in the second rotational direction can cause the gear teeth of the gear portion 302 to drive the output pinion backward as the cam 254 rotates toward and into the first rotational position. Rotation of the cam 254 in the second rotational direction also aligns progressively deeper portions of the grooves or lobes 312 with the cam followers 250, causing the pistons 206 to move from their retracted positions to their extended positions. Due to the tapered shapes of the transition portion 234 and the first body portion 232 of each of the pistons 206, when the cam plate 254 is rotated in the second rotational direction, the contact between the pawl body 220 and the pistons 206 drives the pawl 204 about the pivot axis 226 so that the pawl teeth 222 are rotated toward their respective parking gear 202.The pawl teeth 222 are capable of moving directly into the recesses 218 in the park gears 202 in situations where the park gears 202 are aligned in receiving positions. In other situations, the movement of the pawl gears 222 into the recesses 218 may be blocked because the park gears 202 are aligned in positions where each pawl tooth 222 contacts a tooth of a corresponding one of the park gears 202. However, the piston biasing springs 208 provide compliance that drives the pistons 206 to their extended positions (where the outer surfaces of the first body portions 232 engage the pawl 204 and thereby drive the pawl teeth 222 into engagement with the park gears 202) when the countershafts 72 are slightly rotated.

Claims

[1] Electric drive module (24) with: an electric motor (42); a differential assembly (46); a transmission (44) that transmits rotational power between the electric motor (42) and the differential assembly (46); a housing (40) in which the transmission (22) and the differential assembly (46) are accommodated; wherein the transmission (44) includes a first reduction gear and a second reduction gear, the first reduction gear having a drive gear (60) and a pair of first reduction gears (62), the drive gear (60) being rotatable about a first axis (58), each of the first reduction gears (62) being engaged with the drive gear (60) and rotatable about a respective second axis (74), wherein the second axes (74) are spaced apart from each other and parallel to the first axis (58), wherein the second reduction comprises an output gear (66) and a pair of second reduction gears (64), wherein the output gear (66) is rotatable about a third axis (76) which is parallel to the first axis (58), wherein each of the second reduction gears (64) is engaged with the output gear (66) and non-rotatably coupled to an associated one of the first reduction gears (62); wherein the electric drive module (24) further comprises: a pair of parking gears (202), each of the parking gears (202) being non-rotatably coupled to a corresponding one of the second reduction gears (64); a pawl (204) having a pair of pawl teeth (222), the pawl (204) being coupled to the housing (40) and pivotable between an engaged position in which each of the pawl teeth (222) engages a corresponding one of the parking gears (202), and a disengaged position in which the pawl teeth (222) are disengaged from the parking gears (202); and a pair of pistons (206) movable between a first position and a second position, each of the pistons (206) having a first body portion (232) and a second body portion (236) smaller in diameter than the first body portion (232), wherein contact between the first body portion (232) of the pistons (206) and the pawl (204) positions the pawl (204) in the engaged position, and wherein the pawl (204) is disposed in the disengaged position when the second body portion (236) of the pistons (206) contacts the pawl (204). [2] The electric drive module (24) of claim 1, wherein the electric motor (42) includes an output shaft (56) and wherein the drive gear (60) is coupled to the output shaft (56) for rotation therewith about a first axis (58). [3] The electric drive module (24) of claim 2, wherein the differential assembly (46) includes a differential input member (80) and wherein the output gear (66) is coupled to the differential input member (80) for common rotation about the third axis (76). [4] The electric drive module (24) of claim 3, wherein the differential assembly (46) includes a differential gear set (82). [5] The electric drive module (24) of claim 4, wherein the differential gear set (82) includes a plurality of differential pinions (90) engaged with a pair of side gears (92). [6] The electric drive module (24) of claim 5, wherein a pair of said differential pinions (90) are mounted on a cross pin (94) mounted on said differential input member (80). [7] The electric drive module (24) of claim 1, wherein when the pawl (204) is in the engaged position, a first load transmitted between a first of the pawl teeth (222) and a first of the park gears (202) is equal to a second load transmitted between a second of the pawl teeth (222) and a second of the park gears (202). [8] The electric drive module (24) of claim 1, wherein the pawl (204) is pivotally mounted on a pivot axis (226), and wherein a fit between the pawl (204) and the pivot axis (226) allows non-rotating movement of the pawl (204) relative to the pivot axis (226) to allow the load transferred between the pawl teeth (222) and the parking gears (202) to be balanced. [9] Electric drive module (24) according to claim 1, wherein the first body portion (232) of the pistons (206) is frusto-conical. [10] The electric drive module (24) of claim 9, wherein each piston (206) further comprises a transition portion (234) disposed between the first body portion (232) and the second body portion (236), wherein the transition portion (234) is frustoconical in shape, and wherein a cone angle of the first body portion (232) is smaller than a cone angle of the transition portion (234). [11] The electric drive module (24) of claim 1, further comprising an actuator (210) for controlling the movement of the pistons (206) between the first and second positions, the actuator (210) comprising an actuator hub (252), a cam disc (254), and a plurality of cam followers (250), the actuator hub (252) being coupled to the housing (40), the cam disc (254) being rotatable about the actuator hub (252) and defining a pair of cams (312), each of the cams (312) being a circumferential groove having a depth that tapers between a first circumferential end (320) and a second circumferential end (322), each of the cam followers (250) being received in a corresponding one of the cams (312) and linearly arranged with an associated one of the pistons (206). is. [12] The electric drive module (24) of claim 11, wherein each of the cam followers (250) is fixedly coupled to the associated one of the pistons (206). [13] The electric drive module (24) of claim 11, wherein the actuator (210) further includes a torsion spring (258) disposed between the actuator hub (252) and the cam disc (254), the torsion spring (258) biasing the cam disc (254) toward a first rotational position relative to the actuator hub (252). [14] The electric drive module (24) of claim 11, wherein the actuating member (210) further includes a locking actuating member (262), the locking actuating member (262) having a solenoid assembly (400) and a locking opening (402), the solenoid assembly (400) having a solenoid piston (412), the locking opening (402) formed in the cam disc (254), the solenoid assembly (400) being energized to cause the solenoid piston (412) to be received in the locking opening (402) and to engage the cam disc (254) when the cam disc (254) is rotated to a rotational position aligning the second circumferential ends (322) of the cams (312) with the cam followers (250). [15] The electric drive module (24) of claim 11, wherein a bearing (256) is disposed radially between the actuator hub (252) and the cam disc (254).

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