CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Patent Application No. 61/839,160
filed on June 25, 201 3 and U.S. Patent Application No. 61/936,051 filed on February 5,
2014. The disclosures of the above applications are incorporated herein by reference.
FIELD
[0002] The present disclosure relates generally to differential gear mechanisms and
more particularly to a two-speed differential for a front wheel drive manual transmission
drivetrain vehicle.
BACKGROUND
[0003] A differential gear mechanism can be provided in an axle assembly and used
to transfer torque from a driveshaft to a pair of output shafts. The driveshaft can drive
the differential through the use of a bevel gear that meshes with a ring gear mounted to
a housing of the differential. In automotive applications, a differential allows the tires
mounted at either end of the axle assembly to rotate at different speeds. This is
important when the vehicle is turning because the outer tire travels over an arc of
greater distance than the inner tire. Thus, the outer tire must rotate at a faster speed
than the inner tire to compensate for the greater distance of travel. The differential
includes a differential case and a gear arrangement that allows torque to be transferred
from the driveshaft to the output shafts while concurrently allowing the output shafts to
rotate at different speeds as needed. The gear arrangement can generally include a
pair of side gears that are mounted for rotation with the respective output shafts. A
series of cross pins or pinion gear shafts are fixedly mounted to the differential case for
rotation therewith. A corresponding plurality of pinion gears are mounted for rotation
with the pinion gear shafts and are in meshing relationship with both of the side gears.
[0004] Fuel economy has become increasingly important in motor vehicles. One
way to offer improved efficiency and fuel economy is to provide additional gear sets that
present additional gear ratios for a driver to select. It would be desirable to provide a
transaxle that can operate in additional gear ratios without requiring additional internal
space of the transaxle.
[0005] The background description provided herein is for the purpose of generally
presenting the context of the disclosure. Work of the presently named inventors, to the
extent it is described in this background section, as well as aspects of the description
that may not otherwise qualify as prior art at the time of filing, are neither expressly nor
impliedly admitted as prior art against the present disclosure.
SUMMARY
[0006] A manual transaxle having a two-speed differential according to one example
of the present disclosure includes a differential assembly, a final drive planetary gear
system and a coupling mechanism. The differential assembly can have a differential
housing. The final drive planetary gear system can have a final drive gear, a planetary
ring gear and a sun gear. The final drive planetary gear system can be configured to
selectively operate in (i) a first mode wherein the final drive planetary gear system is
free to rotate relative to the differential housing and (ii) a second mode wherein the final
drive planetary gear system is fixed relative to the differential housing. The coupling
mechanism can be configured to shift the manual transaxle out of sequence while
concurrently moving the final drive planetary gear system between the first and second
modes.
[0007] According to additional features, the manual transaxle can include a
countershaft and a mainshaft that collectively provide a first gear set, a second gear set,
a third gear set, and a fourth gear set. The final drive planetary gear system can
operate in a first mode for a first speed and a second speed and operate in the second
mode for a third speed, fourth speed, fifth speed and a sixth speed. The first speed and
the second speed can have drive ratios that are greater than each of the third, fourth,
fifth and sixth speeds. The first gear set can provide a torque path in the first speed and
the third speed. The third gear set can provide a torque path in the second speed and
the fifth speed.
[0008] According to additional features, the coupling mechanism can further
comprise a shift lever that operates in a double-H shift pattern. The manual transaxle
can further comprise a synchronizer disposed adjacent to the differential housing and
having a slide sleeve configured to selectively engage the planetary ring gear. The
coupling mechanism can further comprise a differential shift rail that supports a
differential shift fork thereon. The coupling mechanism can further comprise a fifth/sixth
speed shift rail that supports a third/fourth shift fork and a fifth/sixth shift fork.
[0009] A manual transaxle having a two-speed differential and constructed in
accordance to additional features can include a differential assembly, a countershaft, a
mainshaft, a final drive planetary gear system and a coupling mechanism. The
differential assembly can have a differential housing and a differential final drive gear.
The countershaft and the main shaft can collectively provide a first gear set, a second
gear set, a third gear set and a fourth gear set. The mainshaft can further comprise a
mainshaft final drive gear that is meshed with the differential final drive gear. The final
drive planetary gear system can have a planetary ring gear and a sun gear. The final
drive planetary gear system can be configured to selectively operate in (i) a first mode
wherein the final drive planetary gear system is free to rotate relative to the differential
housing and (ii) a second mode wherein the final drive planetary gear system is fixed
relative to the differential housing. The coupling mechanism can be configured to shift
the manual transaxle between six distinct gear ratios using the first, second, third and
fourth gear sets and by moving the final drive planetary gear system between the first
and second modes.
[0010] According to additional features, the final drive planetary gear system can
operate in a first mode for a first speed and a second speed. The final drive planetary
gear system can operate in a second mode for a third speed, a fourth speed, a fifth
speed and a sixth speed. The first speed and the second speed can have drive ratios
that are greater than each of the third, fourth, fifth and sixth speeds. The first gear set
can provide a torque path in the first speed and the third speed. The third gear set can
provide a torque path in the second speed and the fifth speed. The coupling
mechanism can further comprise a shift lever that operates in a double-H shift pattern.
The manual transaxle can further comprise a synchronizer disposed adjacent to the
differential housing and having a slide sleeve configured to selectively engage the
planetary ring gear. The coupling mechanism can further comprise a differential shaft
rail that supports a differential shift fork thereon. The coupling mechanism can further
comprise a fifth/sixth speed shift rail that supports a third/fourth shift fork and a fifth/sixth
shift fork. In one example, the manual transaxle is a front wheel drive manual transaxle.
The manual transaxle can be an automated manual transmission having at least one
shift actuator.
[001 1] A two-speed differential gear mechanism constructed in accordance to yet
another example can include a differential casing, a first and second side gear, a
plurality of pinion gears and an electromagnetic solenoid. The differential casing can
have a first differential case portion that defines a first output shaft opening and a
second differential case portion that defines a second output shaft opening. The first
and second side gear can be rotatably mounted within the differential casing. The first
and second side gears can be co-axially aligned along an axis of rotation of the
differential casing. The plurality of pinion gears can be mounted between the first and
second side gears. The plurality of pinion gears can be intermeshed with the first and
second side gears to form torque transfer arrangement configured for transferring
torque between the pinion gears and the first and second side gears to rotate the first
and second side gears about the axis of rotation. The electromagnetic solenoid can be
configured to shift the differential gear mechanism between a first underdrive torque
path and a second direct drive torque path. The underdrive torque path can route
torque through a planetary gear set. The direct drive path can route torque directly
through the pinion gears. The synchronizer can be a boosted self-energized
synchronizer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present disclosure will become more fully understood from the detailed
description and the accompanying drawings, wherein:
[0013] FIG. 1 is perspective view of a six-speed front wheel drive transaxle with four
gear sets and having a drive to a differential with two speeds constructed in accordance
to one example of the present disclosure;
[0014] FIG. 2 is a cross-sectional view of the front wheel drive transaxle of FIG. 1
taken along lines 2-2;
[0015] FIG. 3 is a perspective view of the four gear sets and a corresponding
coupling mechanism of the front wheel drive transaxle of FIG. 1;
[0016] FIG. 4 is a plan view of the coupling mechanism of FIG. 3 and shown in a first
speed;
[0017] FIG. 4A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 4 and shown in the first speed;
[0018] FIG. 5 is a plan view of the coupling mechanism of FIG. 3 and shown in a
second speed;
[0019] FIG. 5A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 5 and shown in the second speed;
[0020] FIG. 6 is a plan view of the coupling mechanism of FIG. 3 and shown in a
third speed;
[0021] FIG. 6A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 6 and shown in the third speed;
[0022] FIG. 7 is a plan view of the coupling mechanism of FIG. 3 and shown in a
fourth speed;
[0023] FIG. 7A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 7 and shown in the fourth speed;
[0024] FIG. 8 is a plan view of the coupling mechanism of FIG. 3 and shown in a fifth
speed;
[0025] FIG. 8A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 8 and shown in the fifth speed;
[0026] FIG. 9 is a plan view of the coupling mechanism of FIG. 3 and shown in a
sixth speed;
[0027] FIG. 9A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 9 and shown in the sixth speed;
[0028] FIG. 10 is a plan view of the coupling mechanism of FIG. 3 and shown in a
reverse speed;
[0029] FIG. 10A is a schematic view of an exemplary shift lever corresponding with
the position of the coupling mechanism of FIG. 10 and shown in the reverse speed;
[0030] FIG. 11 is a table illustrating various gear ratios according to the present
disclosure;
[0031] FIG. 12 is a sectional view of a two-speed differential incorporating a direct
shift planetary reduction according to one example of the present disclosure;
[0032] FIG. 13 is a sectional view of a two-speed differential incorporating a ball
ramp device actuated by an electromagnetic solenoid according to additional features of
the present disclosure;
[0033] FIG. 14 is a chart illustrating a four-speed transmission incorporating an
additional two speeds by way of the two-speed differential and coupling mechanism of
FIG. 1;
[0034] FIG. 15 is a gear pattern and sensor position schematic for a two-speed gear
change according to another configuration of the present disclosure;
[0035] FIG. 16 is a cross-sectional view of a final drive planetary gear system
according to another configuration of the present disclosure; and
[0036] FIG. 17 is a cross-sectional view of an exemplary shift mechanism
constructed in accordance to an additional example of the present disclosure.
DETAILED DESCRIPTION
[0037] With initial reference to FIG. 1, an exemplary two-speed differential
constructed in accordance to one example of the present disclosure is shown and
generally identified with reference numeral 10. The exemplary two-speed differential 10
described herein is shown incorporated into a front wheel drive transaxle 12 having four
gear sets collectively identified at reference 14. As will be described herein, the
combination of a two-speed differential 10 with the four gear sets 14 provides a sixspeed
front wheel drive transmission. While the specific examples described herein are
for a front wheel drive vehicle incorporating a manual transmission and providing six
forward speeds, other configurations can be utilized with the present disclosure.
[0038] As will become appreciated from the following discussion, the present
disclosure provides a low cost, low weight manual transaxle for a front wheel drive
manual transmission driveline. The manual transaxle is provided with a combination of
gears, shafts, synchronizers and the two-speed differential 10. The two-speed
differential 10 can multiply the transmission gear ratios providing two main configuration
options: 1) Overdrive ratio and 2) Low range ratio. The overdrive ratio can allow downspeeding
the engine putting a given vehicle in cruise mode and optimizing fuel
economy. The low range ratio can allow to downsize the engine keeping a launch ratio
able to overcome the vehicle inertia on a rolling start mode until achieving a speed to
maintain the vehicle in movement with high fuel efficiency. Furthermore, the present
disclosure incorporates a mechanical device sensing shifting positions from fourth to
fifth gear at the transmission, or alternatively, from fifth to fourth gear. Mechanical
actuation is provided to change gears on the two-speed differential 10. Transmission
control is able to shift from third gear to fourth gear and from fifth gear to sixth gear
using only one shift rail, transparent to the driver. Other gear change combinations are
contemplated by the present disclosure.
[0039] The present disclosure also considers using a single component for the twospeed
differential 10 in the following concepts: 1) Two-speed differential gear change
using a ball ramp and synchronizing device that boosts shifting force and optimizes gear
engagement. 2) Two-speed differential gear change by direct shift mechanism. 3) Twospeed
differential gear change using a ball ramp device actuated by an electromagnetic
solenoid. 4) Two-speed differential with self-energized boosted synchronizer.
[0040] The two-speed differential 10 incorporated into the front wheel drive manual
transmission 12 can provide a fuel economy improvement due to an optimization of the
gear shift steps. Further, a reduction in weight can be realized in comparison to similar
transmissions for small passenger cars. An existing gear shift pattern (FIGS. 4A, 5A,
6A, etc.) can be maintained for passenger cars making the new technology transparent
to drivers. Gear shift forces can be comparable with small passenger car
transmissions.
[0041] The two-speed differential 10 can be designed having multiple speeds. The
present example includes six speeds on a manual transmission for driver comfort. The
two-speed differential 10 can have an overall ratio of 20 (first gear ratio x differential
gear ratio). Typical transmission ratios may be maintained (4.5 for first gear and 0.65
for sixth gear). Differential ratios of between 3.5 and 5.0 may be used. Shifting of the
two-speed differential 10 can be transparent to the driver.
[0042] The two-speed differential 10 may be incorporated in any manual
transmission including on a four-speed transmission. The two-speed differential 10 can
have a compact size resulting in a weight reduction compared to similar transmissions
currently used on small passenger cars. Compared to a conventional five-speed
transmission, a four-speed transmission incorporating the two-speed differential 10
according to the present disclosure can increase fuel economy. In one example fuel
economy can be increased by 7.5%. It will be appreciated that while the specific
example discussed herein is for a manual transmission having a shift lever, the same
may be applied to an automated manual transmission. An automated manual
transmission may be used with a solenoid actuator. Such an automated manual
transmission may employ electric or pneumatically actuated shift actuators responsive
to a transmission electronic control unit. Gear selection logic can be embedded in an
electronic control unit.
[0043] With specific reference now to FIG. 2, the two-speed differential 10 and
transaxle 14 will be described in greater detail. The transaxle 14 can include a
countershaft 20 and a mainshaft 22 rotatably supported by bearings 24 and 26,
respectively, of the transaxle 14. The countershaft 20 can incorporate a reverse gear
30 thereon. The mainshaft 22 can incorporate a mainshaft final drive gear 32 thereon.
The mainshaft final drive gear 32 can be meshed with a differential final drive gear 40.
[0044] The countershaft 20 and mainshaft 22 collectively provide the gear sets 14 or
specifically, a first gear set 46, a second gear set 48, a third gear set 50 and a fourth
gear set 52. A first and second slide sleeve and reverse gear 60 can be provided on
the mainshaft 22. A fifth and sixth slide sleeve 62 can be provided on the mainshaft 22.
[0045] The front wheel drive transaxle 12 can generally comprise a final drive
planetary gear set or system 70 and the differential assembly 10. The final drive
planetary gear system 70 can include a planetary ring gear 74, a differential housing
(carrier) 78, planetary gears 80 and a sun gear 84. The sun gear 84 can be fixed with a
final drive gear 40.
[0046] A synchronizer assembly 90 can be disposed adjacent to the differential
housing 78. The synchronizer assembly 90 can be a boosted self-energized
synchronizer. In this configuration, the differential housing 78 serves as a carrier. The
ring gear 74 can be selectively engaged by the synchronizer assembly 90. A slide
sleeve 100 can be associated with the synchronizer assembly 90 that selectively
engages the ring gear 74. A bearing 108 can be disposed between the differential
housing 78 and the final drive gear 40.
[0047] The two-speed differential 10 can incorporate multiple pinion gears or
compact bevel gears 120 and the planetary gear set 70 into a single "nested" differential
having dual torque paths. The two-speed differential 10 includes a pair of side gears
122 that are mounted for rotation with axle shafts and first and second front drive
wheels, respectively. The side gears 122 define first and second axle shaft openings.
A cross shaft 130 is fixedly mounted to the differential case 78 for rotation therewith.
The corresponding plurality of pinion gears 120 are in meshing relationship with both of
the side gears 122. In an open configuration, the two-speed differential 10 acts to allow
the axle shafts to rotate at different speeds.
[0048] In a first torque path, an underdrive can be attained through the planetary and
compact bevel differential for short launch rations. In a second torque path, a direct
final drive path can be attained directly through the compact bevel differential for tall
cruising ratios. A gear change can be accomplished through the synchronizer 90 that
boosts gear shift forces and optimizes gear engagement. The synchronizer 90 can
provide similar gear engagement forces compared with small passenger car
transmissions. Leavers and forks can complete the actuation gear change system as
will be described herein.
[0049] Turning now to FIG. 3, a coupling mechanism 130 according to one example
of the present disclosure will be described. The coupling mechanism 130 is used to
shift the transaxle 12 and two-speed differential 10 between six forward speeds and one
reverse speed. The coupling mechanism 130 generally includes a rod drive 132, a cam
lever 134, a differential shift rail 140, fifth/sixth speed shift rail 142, a shift selector rail
144, an auxiliary shift rail 150 (FIG. 4) and a reverse shift rail 152 (FIG. 4). The
differential shift rail 140 supports a differential shift fork 160 thereon. The fifth/sixth
speed shift rail 142 supports a third/fourth shift fork 162 and a fifth/sixth shift fork 166.
The shift selector rail 144 supports a third/fourth and reverse lug 170 and a first/second
and fifth/sixth lug 172. A reverse lever 180 can be coupled between a fifth/sixth shift lug
182 and the fifth/sixth shift fork 166. A first/second and fifth/sixth lug 184 can extend
between the fifth/sixth shift lug 182 and can drag forks 188. A third/fourth and reverse
lug 190 is coupled to the third/fourth shift fork 162 and can selectively couple with a
reverse shift lug 192.
[0050] For the descriptions from FIG. 4 to FIG. 10, the coupling mechanism 130 will
be described for each unique position of a shift lever 200 along the double-H shifter
pattern. Each position of the shift lever 200 will be described in terms of "speed". It will
be appreciated however that the "speed" is actually a distinct gear ratio provided by the
gear sets 14 and the two-speed differential 10. In general, for the first and second
speeds, the final drive gear 40, the planetary ring gear 74 and the sun gear 84 operate
in a first mode (free to rotate relative to the differential housing 78) utilizing an additional
gear ratio of 2.69 (see also FIG. 11) . For the third, fourth, fifth and sixth speeds, the
final drive gear 40, the planetary ring gear 74 and the sun gear 84 operate in a second
mode (fixed to the differential housing 78). When shifting between the second and third
speeds with the shift lever 200 (FIG. 4), the coupling mechanism 130 is providing two
movements. In a first movement, the coupling mechanism 130 disengages the third
gear set 50 and engages the first gear set 46. In a second movement, the coupling
mechanism 130 shifts the two-speed differential 10 from "high-gear" (first mode) to "lowgear"
(second mode). See also FIG. 11.
[0051] As shown in FIGS. 4 and 4A, the coupling mechanism 130 is in a position
corresponding to the first speed. The first speed is a unique gear ratio selectable by the
driver such as by shifting a shift lever 200 along a standard double-H shifter pattern. In
the first speed, the first gear set 46 (FIG. 2) is used. A torque path therefore goes
through the first gear set 46. The final drive gear 40, the planetary ring gear 74 and the
sun gear 84 operate in the first mode ultimately providing a ratio of 20.6 (see also FIG.
11).
[0052] As shown in FIGS. 5 and 5A, the coupling mechanism 130 is in a position
corresponding to the second speed. The second speed is a unique gear ratio
selectable by the driver such as by shifting a shift lever 200 along a standard double-H
shifter pattern. In the second speed, the third gear set 50 (FIG. 2) is used. A torque
path therefore goes through the second gear set 50. The final drive gear 40, the
planetary ring gear 74 and the sun gear 84 operate in the first mode ultimately providing
a ratio of 11.7 (see also FIG. 11) .
[0053] As shown in FIGS. 6 and 6A, the coupling mechanism 130 is in a position
corresponding to the third speed. The third speed is a unique gear ratio selectable by
the driver such as by shifting a shift lever 200 along a standard double-H shifter pattern.
In the third speed, the first gear set 46 (FIG. 2) is used again. A torque path therefore
goes through the first gear set 46. The final drive gear 40, the planetary ring gear 74
and the sun gear 84 operate in the second mode (fixed to the differential housing 78
ultimately providing a ratio of 7.6 (see also FIG. 11).
[0054] As shown in FIGS. 7 and 7A, the coupling mechanism 130 is in a position
corresponding to the fourth speed. The fourth speed is a unique gear ratio selectable
by the driver such as by shifting a shift lever 200 along a standard double-H shifter
pattern. In the fourth speed, the second gear set 48 (FIG. 2) is used. A torque path
therefore goes through the second gear set 48. The final drive gear 40, the planetary
ring gear 74 and the sun gear 84 operate in the second mode ultimately providing a
ratio of 5.5 (see also FIG. 11) .
[0055] As shown in FIGS. 8 and 8A, the coupling mechanism 130 is in a position
corresponding to the fifth speed. The fifth speed is a unique gear ratio selectable by the
driver such as by shifting a shift lever 200 along a standard double-H shifter pattern. In
the fifth speed, the third gear set 50 (FIG. 2) is used. A torque path therefore goes
through the third gear set 50. The final drive gear 40, the planetary ring gear 74 and the
sun gear 84 operate in the second mode ultimately providing a ratio of 4.3 (see also
FIG. 11).
[0056] As shown in FIGS. 9 and 9A, the coupling mechanism 130 is in a position
corresponding to the sixth speed. The sixth speed is a unique gear ratio selectable by
the driver such as by shifting a shift lever 200 along a standard double-H shifter pattern.
In the sixth speed, the fourth gear set 52 (FIG. 2) is used. A torque path therefore goes
through the fourth gear set 52. The final drive gear 40, the planetary ring gear 74 and
the sun gear 84 operate in the second mode ultimately providing a ratio of 3.7 (see also
FIG. 11).
[0057] As shown in FIGS. 10 and 10A, the coupling mechanism 130 is in a position
corresponding to reverse. Reverse is selectable by the driver such as by shifting a shift
lever 200 along a standard double-H shifter pattern.
[0058] With particular reference to FIG. 11, exemplary gears and differential ratio
designs are illustrated. As used herein the term "ratio" is used to denote a ratio of
rotational speeds of an input gear and an output gear. It will be understood that all of
the ratios identified herein are merely exemplary and other ratios may be provided. As
will become appreciated from the following discussion, the final drive planetary gear
system 70 provides a two-speed final drive configuration where six distinct speeds can
ultimately be attained. FIG. 11 illustrates a table 260 that outlines six "speeds" 262 that
can be attained using exemplary gear ratios 264 gear sets 266, and the final drive
planetary gear system 70 (FIG. 2). As described above, the six "speeds" 262 are
generally referred to herein as the unique outputs selectable by the driver such as by
shifting the shift lever 200 along a standard double-H shifter pattern. In this regard,
each unique position along a double-H shifter gate will correspond to a unique "speed".
[0059] In the exemplary configuration shown, the first gear set 46 has a ratio of 1.57,
the second gear set 48 has a ratio of 1.12, the third gear set 50 has a ratio of 0.89 and
the fourth gear set 52 has a ratio of 0.76. The first gear set 46, the second gear set 48,
the third gear set 50 and the fourth gear set 52 (FIG. 2) can be provided on the
countershaft 20 and the mainshaft 22 of the transaxle 12 or can be provided for
communicating a rotational input onto the input shaft. The final drive gear 40 can have
a ratio of 4.87.
[0060] During operation, the final drive gear 40, planetary ring gear 74 and the sun
gear 84 can rotate in a first mode (speeds one and two) relative to the differential
housing 78. The final drive gear 40, planetary ring gear 74 and the sun gear 84 can
alternatively be fixed for rotation with the differential housing 78 in a second mode
(speeds three, four, five and six). The final drive planetary gear system 70 of the
present disclosure can provide a gear ratio of 2.69 in the first mode and 1.00 in the
second mode. Those skilled in the art will appreciate that the modes may be configured
differently while still providing six speeds visible to the driver in sequence with the four
gear sets 14 and the two-speed differential 10. Explained further, the two-speed
differential 10 can be used to connect any of the gear sets 14 as desired. In the
particular example shown, when the first and second speeds are changed, no motion is
required inside the transmission 12. This results in improved fuel economy. FIG. 11
also illustrates a comparison plot 280 of engine rpm versus vehicle speed for a prior art
configuration and the current disclosure (shown as "Proposal").
[0061] Turning now to FIG. 12, a two-speed differential 310 constructed in
accordance to additional features of the present disclosure will be described. The twospeed
differential 3 10 can include a differential casing 320 to incorporate multiple pinion
gears or compact bevel gears 360 and a planetary gear set 362 into a single "nested"
differential having dual torque paths. The two-speed differential 310 includes a pair of
side gears 364 and 366 that are mounted for rotation with axle shafts and first and
second front drive wheels, respectively. The side gears 364 and 366 define first and
second axle shaft openings 370 and 372. A plurality of cross pins are fixedly mounted
to the differential case for rotation therewith. The corresponding plurality of pinion gears
360 are mounted for rotation with the pinion gear shafts and are in meshing relationship
with both of the side gears 364 and 366. In an open configuration, the two-speed
differential 310 acts to allow the axle shafts to rotate at different speeds.
[0062] In a first torque path, an underdrive can be attained through the planetary and
compact bevel gears 360 for short launch rations. In a second torque path, a direct final
drive path can be attained directly through the compact bevel gears 360 for tall cruising
ratios. Gear changes can be accomplished through a small ball ramp device 374
actuated by a direct lever and fork system. The ball ramp device 374 can boost the
gear shift forces and optimize gear engagement. The gear change system can provide
similar gear engagement forces comparatively with existing small passenger car
transmissions.
[0063] With reference to FIG. 13, another two-speed differential constructed in
accordance to the present disclosure is shown and generally identified at reference 410.
The two-speed differential 410 can incorporate multiple pinion gears or compact bevel
gears 420 and a planetary gear set 430 into a single "nested" differential having dual
torque paths. The two-speed differential 410 includes a pair of side gears 434 and 436
that are mounted for rotation with axle shafts and first and second front drive wheels,
respectively. The side gears 434 and 436 define first and second axle shaft openings
440 and 444. A plurality of cross pins are fixedly mounted to the differential case for
rotation therewith. The corresponding plurality of pinion gears 420 are mounted for
rotation with the pinion gear shafts and are in meshing relationship with both of the side
gears 434 and 436. In an open configuration, the two-speed differential 410 acts to
allow the axle shafts to rotate at different speeds.
[0064] In a first torque path, an underdrive can be attained through the planetary and
compact bevel gears 420 for short launch rations. In a second torque path, a direct final
drive path can be attained directly through the compact bevel gears 420 for tall cruising
ratios. A gear change can be accomplished through a ball ramp and a synchronizer
450 or a direct drive boost actuated by an electromagnetic solenoid component 458.
The boost device can provide similar gear engagement forces compared with small
passenger car transmissions. A transmission control unit and specific software will
complete the actuation gear change system.
[0065] Turning now to FIG. 14, a shift sequence according to additional features of
the present disclosure is shown. In the example shown in FIG. 14, the two-speed
differential 10 is used when shifting between the third and fourth gear sets 50 and 52.
In this regard, while the examples shown in FIGS. 1-1 1 focus on (i) the final drive gear
40, the planetary ring gear 74 and the sub gear 84 operating in the first mode (free to
rotate relative to the differential housing 78) for the first and second speeds and (ii) the
final gear 40, the planetary ring gear 74 and the sun gear 84 operating in the second
mode (fixed to the differential housing 78), for the third, fourth, fifth and sixth speeds,
any combination may be used to attain six distinct drive ratios using the four gear sets
14 and two-speed differential 10.
[0066] With reference to FIG. 15, a mechanical system sensing a shifting position of
fourth to fifth gear at the transmission (or similarly from fifth to fourth gear) providing
mechanical actuation such as to the electromagnetic solenoid component 458 (FIG. 13)
to change gears on the two-speed differential 10 is provided. A sensor 480 at the
manual transmission control system is provided to select between high or low mode at
the two-speed differential 10. The sensor 480 can be used in automated transmissions
or as an alternate example to mechanically shift the two-speed differential 10. A boost
device can be provided that is designed to change the gear at the two-speed differential
to keep an existing gear shift pattern for passenger cars and similar gear engagement
forces comparatively with small passenger car transmissions. These features can make
the new technology transparent to the drivers. As is appreciated from the discussion
herein, the mechanical system can additionally or alternatively sense shifting positions
between other gears, such as between first and second (1-2 gate) and third and fourth
(3-4 gate).
[0067] The configuration of the present disclosure provides a front wheel drive
transaxle having a speed change not in sequence combined with a gearbox that
simultaneously changes the two speed differential between the first and second modes.
Explained further, the present configuration allows a user to change speeds (or as a
user sees "shift" using a conventional double H shifter) from second speed to third
speed. In doing so, a torque path changes from utilizing the third gear to the first gear
while simultaneously the differential carrier 232 goes operating from the first mode
(relative rotation) to the second mode (fixed). For the gearing arrangement shown in
FIG. 11, the sensor shown in FIG. 15 would be located between the 1-2 gate and the 3-
4 gate.
[0068] Turning now to FIG. 16, a front wheel drive transaxle constructed in
accordance to another example of the present disclosure is shown and generally
identified at reference 510. The front wheel drive transaxle 510 is generally a six-speed
manual transmission with a two-speed planetary gear configured at a countershaft 514.
The front wheel drive transaxle 5 10 can generally comprise a planetary ring gear 530, a
carrier housing 532, a planet gear 534, a sun gear 538, and a final drive gear 540. In
the example shown, the sun gear 538 is integrated at the countershaft 514. An input
shaft 550 can have a series of gears 552 that can be selectively engaged.
[0069] With reference now to FIG. 17, a shift mechanism 600 constructed in
accordance to one example of the present disclosure is shown. The shift mechanism
600 can change gears on a gearbox not in sequence and also provide the simultaneous
change on the two-speed differential transparent to a user. As used herein the phrase
"not in sequence" will be used to refer to directly shifting between gears out of numerical
sequence (e.g., from third gear to first gear, etc.) In this regard, the gearbox can be a
conventional "double-H" shifter pattern. The shift mechanism 600 can include a
differential shift rail 640 and a third/fourth shift rail 641 . The third/fourth shift rail 641 can
be partially received in a blind bore 638 formed on the differential shift rail 640.
[0070] The shift mechanism 600 can have a first gear set 646, a second gear set
648, a third gear set 650 and a fourth gear set 652. The shift mechanism 600 can
include a reverse shift rail 662, a first/second shift rail 664, a reverse shift fork 668, a
first/second shift fork 670, a third/fourth shift fork 674, a fifth/sixth shift fork 676 and a
differential shift fork 678 and a can 680. A plurality of synchronizers 684 and a plurality
of slide sleeves 688 can be incorporated on the shift mechanism 600. A shift lug 690
can be positioned between the differential shift rail 640 and the third/fourth shift rail 641 .
The synchronizers 684 can be used on both sides of the gear that is used in connection
with the low and high gear at the two-speed differential.
[0071] It will be appreciated that while the above discussion has been directed
toward a six-speed transaxle configuration, the present teachings are not so limited.
The present disclosure can be used on transaxles configured for other speeds. In other
words, the teachings of the present disclosure can be used toward a compact low cost,
low weight, high performance, multiple speed manual transaxle having a two-speed
differential device. Additional configurations may be found in commonly owned and
currently pending PCT application WO 2014/014777, filed on July 12, 201 3, the
contents of which are expressly incorporated herein by reference.
[0072] The foregoing description of the embodiments has been provided for
purposes of illustration and description. It is not intended to be exhaustive or to limit the
disclosure. Individual elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are interchangeable and
can be used in a selected embodiment, even if not specifically shown or described. The
same may also be varied in many ways. Such variations are not to be regarded as a
departure from the disclosure, and all such modifications are intended to be included
within the scope of the disclosure.

CLAIMS
What is claimed is:
1. A manual transaxle having a two-speed differential, the manual transaxle
comprising:
a differential assembly having a differential housing;
a final drive planetary gear system having a final drive gear, a planetary
ring gear and a sun gear, the final drive planetary gear system configured to selectively
operate in (i) a first mode wherein the final drive planetary gear system is free to rotate
relative to the differential housing and (ii) a second mode wherein the final drive
planetary gear system is fixed relative to the differential housing; and
a coupling mechanism configured to shift the manual transaxle out of
sequence while concurrently moving the final drive planetary gear system between the
first and second modes.
2 . The manual transaxle of claim 1, further comprising a countershaft and a
mainshaft that collectively provide a first gear set, a second gear set, a third gear set
and a fourth gear set.
3. The manual transaxle of claim 2 wherein the final drive planetary gear
system operates in the first mode for a first speed and a second speed and operates in
the second mode for a third speed, fourth speed, fifth speed and a sixth speed, wherein
the first speed and second speed have drive ratios greater than each of the third, fourth,
fifth and sixth speeds.
4 . The manual transaxle of claim 3 wherein the first gear set provides a
torque path in the first speed and the third speed.
5. The manual transaxle of claim 4 wherein the third gear set provides a
torque path in the second speed and the fifth speed.
6 . The manual transaxle of claim 1 wherein the coupling mechanism further
comprises a shift lever that operates in a double-H shift pattern.
7. The manual transaxle of claim 1, further comprising a synchronizer
disposed adjacent to the differential housing and having a slide sleeve configured to
selectively engage the planetary ring gear.
8. The manual transaxle of claim 1 wherein the coupling mechanism further
comprises a differential shift rail that supports a differential shift fork thereon.
9. The manual transaxle of claim 8 wherein the coupling mechanism further
comprises a fifth/sixth speed shift rail that supports a third/fourth shift fork and a
fifth/sixth shift fork.
10. A manual transaxle having a two-speed differential, the manual transaxle
comprising:
a differential assembly having a differential housing and a differential final
drive gear;
a countershaft and a mainshaft that collectively provide a first gear set, a
second gear set, a third gear set and a fourth gear set, the mainshaft further comprising
a mainshaft final drive gear that is meshed with the differential final drive gear;
a final drive planetary gear system having, a planetary ring gear and a sun
gear, the final drive planetary gear system configured to selectively operate in (i) a first
mode wherein the final drive planetary gear system is free to rotate relative to the
differential housing and (ii) a second mode wherein the final drive planetary gear system
is fixed relative to the differential housing; and
a coupling mechanism configured to shift the manual transaxle between
six distinct gear ratios using the first, second, third and fourth gear sets and by moving
the final drive planetary gear system between the first and second modes.
11. The manual transaxle of claim 10 wherein the final drive planetary gear
system operates in the first mode for a first speed and a second speed and operates in
the second mode for a third speed, fourth speed, fifth speed and a sixth speed, wherein
the first speed and second speed have drive ratios greater than each of the third, fourth,
fifth and sixth speeds.
12. The manual transaxle of claim 11 wherein the first gear set provides a
torque path in the first speed and the third speed.
13. The manual transaxle of claim 12 wherein the third gear set provides a
torque path in the second speed and the fifth speed.
14. The manual transaxle of claim 10 wherein the coupling mechanism further
comprises a shift lever that operates in a double-H shift pattern.
15. The manual transaxle of claim 10, further comprising a synchronizer
disposed adjacent to the differential housing and having a slide sleeve configured to
selectively engage the planetary ring gear.
16. The manual transaxle of claim 10 wherein the coupling mechanism further
comprises:
a differential shift rail that supports a differential shift fork thereon;
a fifth/sixth speed shift rail that supports a third/fourth shift fork; and
a fifth/sixth shift fork.
17. The manual transaxle of claim 10 wherein the manual transaxle is an
automated manual transmission having at least one shift actuator.
18. The manual transaxle of claim 10 wherein the manual transaxle is a front
wheel drive manual transaxle.
19. A two-speed differential gear mechanism comprising:
a differential casing having a first differential case portion that defines a
first output shaft opening and a second differential case portion that defines a second
output shaft opening;
a first and a second side gear rotatably mounted within the differential
casing, the first and second side gears being co-axially aligned along an axis of rotation
of the differential casing;
a plurality of pinion gears mounted between the first and second side
gears, the plurality of pinion gears intermeshing with the first and second side gears to
form a torque transfer arrangement configured for transferring torque between the
pinion gears and the first and second side gears to rotate the first and second side
gears about the axis of rotation; and
an electromagnetic solenoid configured to shift the differential gear
mechanism between a first underdrive torque path and a second direct drive torque
path, wherein the underdrive torque path routes torque through a planetary gear set and
the direct drive path routes torque directly through the pinion gears.
20. The two-speed differential gear mechanism of claim 19 wherein the
synchronizer is a boosted self-energized synchronizer.