ADAPTER FOR CONNECTING A COUNTERSHAFT
TRANSMISSION WITH A HYDRAULIC LAUNCH ASSIST SYSTEM
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of United States Provisional Application
No. 61/264,987, filed November 30, 2009, which is hereby incorporated by reference
in its entirety.
BACKGROUND OF THE INVENTION
[0002] Known hybrid vehicle drive systems coupling an internal combustion
engine and an alternative power source such as an electric motor or a hydraulic
motor require means of linking the alternative power source and the internal
combustion engine to the drive wheels. Each configuration may have a preferred
configuration, but such configuration can vary with vehicle use and application.
[0003] One known electric hybrid system, of the general type described in US
Patent No. 7463962, has an electric motor coupled to a transmission input shaft.
This configuration'was well suited for use with a transmission, having a countershaft
powerflow configuration. However, by placing the motor in line with the engine and
transmission, increasing the size of the electric motor requires making many
significant changes to the associated driveline: components and mounting features at
great expense. It is desired to have an arrangement which permits greater flexibility
in changing the size of the electric motor or electric motor/generator, and which is
also well suited to a countershaft.transmission. Countershaft transmissions are also
known as mechanical or manual transmissions, in part because countershaft
transmissions have been shifted manually by the vehicle operator. Automated
countershaft transmissions are known as automated mechanical transmissions or
AMTs.
[0004] One hydraulic hybrid system, known as a hydraulic launch assist (HLA)
system, has been adapted for commercial vehicles and increases fuel economy and
acceleration compared to vehicles not so equipped, particularly when used in
application having frequent starting and stopping and low-speed operation, such as
city buses and refuse collection trucks. However,.HLA systems are typically used in
combination with conventional automatic transmissions employing a torque converter
to communicate driving, torque from an engine to the transmission. The torque
converter facilitates starting the vehicle from a stopped condition without the need to
gradually engage a clutch, and; the torque converter also provides torque
multiplication when there is a significant speed ratio across the torque converter. At
low speed operation, the torque converter losses are a muchmore significant portion
of the power from the-engine. A countershaft transmission, and more particularly an
automated mechanical transmission (AMT) equipped with a plate clutch for
transmitting torque, is significantly more efficient at low speed and start-stop
operation than a torque converter transmission, and weighs less than a torque
converter transmission. However, typical dry friction clutch plates or driven discs
wear out undesirably quickly under such operating conditions. Additionally, the rate
of acceleration when starting from a stop is typically less for an AMT equipped
vehicle than a torque converter/automatic transmission equipped vehicle in part
because of the torque multiplication benefit conferred by a torque converter. It is
desired to have an arrangement which permits the coupling of an HLA system with a
countershaft transmission and reduces the driven disc wear concern and improves
the acceleration of the-system over the acceleration provided by an AMT with a dry
friction clutch.
SUMMARY OF THE INVENTION
[0005] This invention provides a common means of coupling an alternative
power source to a vehicle's drive wheels which is particularly well suited for use with
a countershaft-type transmission.
[0006] This invention also overcomes the clutch wear concern by eliminating
the need to engage the friotional clutch to launch the vehicle. This invention also
improves the acceleration of the vehicle compared to a typical dry friction clutch
launch by relying on the HLA system to transfer more power to the drive wheels more
quickly than would be transferred by a typical launch engagement of a dry friction,
clutch in a commercial vehicle.
DESCRIPTION OF DRAWINGS
[0007] Figure 1 is a perspective view of a drivetrain combining an automated
mechanical transmission AMT and an HLA.
[0008] Figure 2 is a schematic view of the drivetrain of figure 1.
[0009] Figure 3 is a schematic view of a first alternative embodiment of the
Invention.
[0010] Figure 4 is a schematic view of a second alternative embodiment of the
invention.
[0011] Figure 5 is a schematic view of a third alternative embodiment of the
invention.
[0012] Figure 6 is a schematic view of a fourth alternative embodiment of the
invention.
[0013] Figure 7 is a schematic view of a-fifth alternative embodiment of the
invention.
[0014] Figure 8 is a schematic view of a sixth, alternative embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Figure 1 shows a drivetrain 10 including an automated mechanical
transmission (AMT) 12 connected to a hydraulic launch assist system (HLA system)
14 by an intermediate propeller shaft 16. Another propeller shaft, referred to
hereafter as adriveshaft 18, is connected to transmission 12 on one end for
connection to an axle, (not shown) on the other end. An adapter module-20 is
incorporated into transmission 12 to connect HLA system 14 to drivetrain. Adapter
module 20 beneficially eliminates the need for a transfer case which was disposed.
between the transmission and the HLA system in prior, art systems. Adapter module
20 provides much of the functionality of a transfer case with much less hardware, A
master clutch 22 provides a selectively engaged driving connection between a
vehicle drive engine (not shown) and AMT 12.
[0018] Figure 2 shows schematically one configuration of the drivetrain of
Figure 1. Adapter module 20 is disposed between front box 24 and auxiliary section
26. The invention is not intended to be limited by the configuration of the
transmission shown, except to extent the transmission employs an'input shaft, an
output shaft and a countershaft. Front box 24 has an input shaft 28, an output shaft
30 and a countershaft 32. Front box 24, by way of example only, provides four
selectable forward drive gear ratios and one reverse gear drive ratio. A headset of
meshed gears provides driving: engagement between input shaft.:28 and countershaft
32. Gears on output shaft 30 are in mesh with gears on countershaft 32. Slideable
dog clutches are used to fix the gears, to the shaft on which they are disposed to
achieve the targeted gear ratio.
[0019] Auxiliary section 26, in the. exemplary embodiment a range box, is
coupled, to front box 24 by output shaft 30, providing up to an additional four ratios for
each forward gear ratio, The.number of ratios available in each section is not critical
to the invention. Auxiliary section 26 has a countershaft 34 and an output shaft 36.
intermediate propeller shaft 16 passes adjacent to rather thanthrough range box 26.
[0020] Adapter module 20 has a mechanism for transmitting torque between
transmission output, shaft 30 and an HLA system input shaft 38. The mechanism
takes the form of an adapter gear set 40 with meshed first and second gears 42 and
44 respectively. It should be appreciated that any known fixedrratio means for
transferring speed and torque between parallel shafts can be employed in place of
gear set 40, such as more complicated gear sets, or a sprocket and chain
combination, potentially in combination with other fixed ratio mechanisms.
[0021] First gear 42 is drivingly connected to input shaft 38 of HLA system 14.
First gear 42 is shown as mounted directly to shaft 38, but could alternatively be on a
separate shaft and drivingly connected by a gear set, drive chain and sprocket
combination, or any other mechanism known in the art. Such an intermediate
element could provide a speed differential of a fixed ratio between countershaft 32
and the HLA input shaft 38.
[0022] Second gear 44 is shown as being rotatably disposed over a range box
output shaft 36.
[0023] Adapter module 20 also has two clutches: a launch clutch 46 and a
regen clutch 48.
[0024] Launch clutch 46 is coaxial with first gear 42 and selectively connects
first gear 42 to counter shaft 32. Regen clutch 48 is coaxial with second gear 44 and
selectively drivingly connects second gear 44 with output shaft 30. Clutches 46 and
48 do not have to be coaxial with their respective gears, as might be the case if
intermediate elements are employed. An important function of launch clutch 46 is.
that it provides a selective driving connection between countershaft 32 and HLA
system input shaft 38.. An important function of regen clutch 48 is that it provides a
selective driving connection between output shaft 30 and the HLA system input shaft
38.
[0025] Launch clutch 46 is shown in the figures as being, a slider or dog-tooth
type clutch. Such a clutch has the benefit of being self contained, requiring little
energy to operate, and'permitting no slippage when engaged. Launch clutch 46 can
be controlled by any mechanism suitable for axially displacing a clutch sleeve. Such
mechanisms are well known in the art of transmissions, and include pneumatically,
hydraulically and electrically actuated shift forks. Schemes for direct displacement
through electromagnetic means are also known in the art.
[0026] Regen dutch 48 is shown as a plate-type clutch, typical of those found
in torque converter type automatic transmissions. Such clutches have the advantage
of being able to permit engagement while there is a relative speed difference
between the parts being engaged by the clutch. Additionally, plate clutches more
easily enable declutching or releasing than typical sliding-dog tooth clutches.
[0.027] HLA system 14 includes a pump/motor unit 50and both a high pressure
accumulator 52 and a reservoir or low pressure accumulator 54. The HLA system
functions as described in US Patent No. 7;082,757. in an HLA "charging" or
"regeneration" mode, torque is applied to input shaft 38 of both HLA system 14 and
pump/motor unit 50 with pump/motor unit 50 operating in a pump mode. In the pump
mode, pump/motor unit 50 draws hydraulic fluid from low pressure accumulator 54
and forces it into high pressure accumulator 52 where the fluid is retained under
significant pressure. In a "discharging" or "driving" mode of HLA system 14,
pump/motor unit 50 operates in a motor mode. In the motor mode, pressurized fluid
from high pressure accumulator 52 acts oh pump/motor unit 50 to induce a torque on
input shaft 38 and causing shaft 38 to rotate. Fluid exiting pump/motor unit 50 enters
low pressure accumulator 54, Torque is transferred between HLA system 14 and
adapter module 20 by intermediate propeller shaft 16.
[0028] A description of the invention operation follows. In a first, or launch
condition, a vehicle employing the inventive drive'traih is at a complete stop with the
vehicle engine Idling, master clutch 22 disengaged, range box 26 in an appropriate
launch mode, and high pressure:accumulator 52 fully charged. A first gear ratio
dutch within transmission front box 24 is engaged. Launch clutch 46 is engaged,
ratatively fixing transmission counter shaft 32 to HLA Input shaft 38. Regen clutch 48
is disengaged, allowing gear 44 to rotate freely on output shaft: 30. Pump/motor 50 is
operated in its motor mode, communicating torque to counter shaft 32 and through
the transmission gear set of the first gear ratio to output shaft 30, through range box
26 and driveshaft 18 to the vehicle axle (not shown), starting the vehicle in motion. It
is appreciated that transmission input shaft 28 is back-driven through a gear set
between the input shaft and countershaft, or headset 56, by the rotation of
countershaft 32. When input shaft 28 reaches approximately the rotational speed of
the crankshaft of the idling engine, master clutch 22 can be engaged, and the source
of driving power transitioned from HLA system 14 to the vehicle engine. Launch
clutch 46 can then be disengaged.
[0029] it should be appreciated that this sequence can be altered. For
example, instead of having the engine idling, the engine could be completely
stopped1. With master clutch 22 engaged, launch clutch 46 engaged and
transmission front box 24 in neutral, the engine would be started by torque from HLA
system 14 passing through the countershaft and transmitted to the engine through
headset 56. Master clutch 22 and launch clutch 46 would be each disengaged, a
start gear selected in front box 28, and the vehicle launched by engaging master
clutch 22. Depending on the torque capabilities of HLA system 14, it may be possible
to simultaneously launch the vehicle and start the motor, With master clutch 22
engage, launch clutch 46 engaged and transmission front box 24 in a selected
launch gear, the engine would be started as the vehicle starts to roll under the power
of the HLA system. Once the engine is at a self-sustaining speed, launch clutch 46 is
disengaged. Yet alternatively, the vehicle could be launched using the HLA alone,
and the engine started by engaging master clutch 22 when the vehicle is at a
predetermined speed. Launch clutch 46 would be disengaged before engaging
master clutch 22.
[0030] In an alternative launch mode of operation, with the vehicle at a stop,
the engine idling, and high pressure accumulator 52 fully charged, master clutch 22 is
disengaged, launch clutch 46 is disengaged, and regen clutch 48 is engaged. A gear
set within each of transmission front.box 24 and range box 26 is selected and
engaged. HLA system 14 is used to launch the vehicle. Output shaft 30, through its
selected gear set, back drives countershaft 32 which in turn back drives transmission
input shaft 28. When input shaft 28 is rotating at about engine idle speed, master
clutch 22 is engaged while regen clutch 48 is disengaged, enabling a smooth shift
from HLA driving torque to engine driving torque.
[0031] To enable operation of HLA system 14 in a regeneration mode, launch
clutch 46 is disengaged, regen clutch 48 is disengaged, master clutch 22 can be
either engaged or disengaged, the front box 24 and range box 26 each have an
appropriate gear engaged, and the vehicle is moving at or below a predetermined
speed. Pump/motor unit 50 is placed in the pump mode, and regen clutch 48 is
engaged to recharge the high pressure accumulator. Rotation of output shaft 36,
resulting from rotation of the vehicle wheels, through range box 26, drives output
shaft 30 which rotates second gear 44 which, through first gear 42, causes HLA
system input shaft 38 to rotate, causing motor pump 50 to draw fluid from jow
pressure accumulator, and force it into high pressure accumulator 52 under high
pressure. Such recharging can be executed responsive to vehicle system
commands to slow the vehicle, providing regenerative braking. The kinetic energy
associated with the inertia of the vehicle is transformed into the potential energy
associated with the pressurized hydraulic fluid in the high pressure accumulator.
[0032] Placing adapter module 20 between front box 24 and auxiliary section
26 of transmission 12 beneficially enables HLA system 14 to be used to provide
hydraulic assist in several different drive ratios. It is anticipated that for certain
applications, auxiliary section 26 would enable the anticipated range of speed of
countershaft 32 to remain within the operating speed range of the HLA pump/motor
unit 50. In such cases, power from HLA system 14 would be avaltable over the enlire
operational range of the vehicle.
[00331 Figure 3 shows an alternative drivetrain 110 in which a transmission
112 has (he more conventional arrangement of an auxiliary section or box 126 fixed
directly to an end of a front box 124. An adapter module 120 is mounted to an end of
auxiliary box 126 opposite front box 124. The launch modes and regen or recharge
modes of operation would be essentially the same as described above for the
embodiment of Fig. 2, but an HLA system 114 would only be available at a low end of
the vehicle's range of operating speeds because of the fixed ratio relationship
between the rotational speed of an HLA input shaft 138 and a propeller shaft 118
connecting to the axle.
[0034] Fig. 4 shows an alternative drivetraih 210 for a transmission 212 not
having an auxiliary section. Such arrangements are typical in light and medium duty
vehicle applications. Adapter module 220 is connected to an end of transmission
212 opposite a master clutch 222. A first gear 242 and a launch clutch 246 and HLA
input shaft 238 are axially aligned with a countershaft 232. A second gear 244 and
regen clutch 248 are disposed over output shaft 230. As with the embodiment of Fig.
3, HLA system 214 is only available at the low end of the vehicle's operating speed
range because of the fixed ratio relationship between the rotational speed of HLA
input shaft 238 and the output shaft 230 which is drivingly connected to the axle.
[0035] Fig. 5 shows a drivetrain 310 nearly the same as that of Fig. 2, with an
adapter module 320 disposed between a front box 324 and an auxiliary section 326
of transmission 312. A significant change relative to the embodiment of Fig. 2 is that
the embodiment of Fig. 5 does not have HLA input shaft 338 axially aligned with
countershaft 332. Instead, adapter module 320 has a third gear 345 in its adapter
module gear set 340. First gear 342 is in axial alignment with countershaft 332.
Launch clutch 346 selectively engages first gear 342 with countershaft 332. Second
gear 344 is disposed over output shaft 330 of front box 324, with regen clutch 348
selectively relatively fixing second gear 344 to output shaft 330. Third gear 345,
drivingly meshed with first gear 342, is relatively fixed to input shaft 338 of HLA
systenrv314.
[0036] Fig. 6 also shows a drivetrain 410 nearly the same as that of Fig. 2, with
an adapter module 420 disposed between a front box 424 and an auxiliary section
426 of transmission 412. A significant change relative to the. embodiment of Fig. 2 is
that the embodiment of Fig. 6 does not have a launch clutch in axial alignment with
output shaft 43b. Instead, a two-way clutch mechanism 449 employed to
alternatively provide the launch and regen functions is in axial alignment with
countershaft 432. Also, first gear 442 rotates freely relative to input shaft 438 unless
mechanism 449 engages clutch 448, instead of being fixed relative thereto as in the
embodiment of Fig. 2. Second gear 444 is accordingly ftxed relative to output shaft
430, as distinguished from the embodiment ef Fig 2 which has the second gear
rotatably mounted on the output shaft,
[0037] Clutching mechanism 449 selectively engages regen clutch 448 to
rotatably couptefirst gear 442 to HLA system input shaft 438 in a regen mode.
Torque is transferred between HLA system 414 and output shaft 430 by gear set
440. Alternatively, clutching mechanism 449 selectively engages launch clutch 446
to rotatably couple HLA system input shaft 438 with a countershaft 432 in a launch
mode. Arrow 458 illustrates one possible torque path in the launch mode. No torque
is transmitted through gear set 440.
[0038] Fig. 7 shows a drivetratn 510 similar to that of Fig. 4, with an adapter
module 520 adjacent to a transmission 512 having no auxiliary section. A significant
change relative to the embodiment of Fig. 4 isthat an electric hybrid system 560 has
been substituted for the HLA system. Hybrid system 560 serves as an alternative
means of converting mechanical kinetic energy to potential energy. Another
difference isthat regen clutch 548 is a non-synchronized dog-tooth clutch, tike launch
clutch 546. Another less significant difference is-that adapter module 520 lias three
gears tike the adapter module of Fig. 5.
[0039] Hybrid system 560 includes an electric motor/generator 562 in place of
a hydraulic pump/motor, and a battery 564 in place of a high pressure accumulator.
Hybrid system 560 additionally includes a power electronics module 566 which may
incorporate elements, by way of example, a voltage transformer, and an Inverter.
Power electronics module 566 can be comprised of integrated elements, or separate,
discrete elements, Motor/generator 562 is scalable depending on system design
requirements. An anticipated power range for the motor/generator for the anticipated
applications is 30kW to 100 kW. Packaging design will accommodate the packaging
of a range of motor/generator sizes. Motor/generator capacities can potentially be
varied with the length of the motor/generator. Battery 564 can also be scaled to
accommodate anticipated system demands. Larger batteries Incorporating additional
cells may be employed. Or, alternatively, a plurality of identical batteries may be
employed to increase energy storage capacity as may be desired.
[0040] Each of the embodiments of Figures 1-7 would require systems controls
to operate the transmission and hybrid system,, whether hydraulic or electronic, in a
coordinated fashion. Fig. 7 shows discrete transmission and hybrid electronic control
units ("ECU" or "ECUs") 568 and 570 respectively. It should be appreciated that
transmission and hybrid ECUs 568 and 570. could be integrated into a single ECU.
Transmission ECU 568 is electronically connected to transmission and adapter
module controllers 572 and 574 respectively. Controllers include mechanisms for
shifting the transmission and the adapter module to select desired gear modes. Such
mechanisms are well known in the art and can include any of electric or hydraulic or
pneumatic actuating mechanisms or any combination thereof. The connections can
be by wire, or can by any known wireless means such as Bluetooth®. Such
connections provide a means of transmitting control signals from ECU 568 to
controllers 572 and 574.
[0041] By employing.an electric hybrid system 560, driveiine 510 beneficially
eliminates the need tor a synchronizing clutch within adapter module 520. Electric
motor/generator 592 can be speed controlled with sufficient accuracy to provide the
necessary low speed differential between gear 544 and output shaft 530 to enable
engagement of dbg clutch. 548 without any mechanical synchronization to speeding
up or slowing down the supplemental power source, in this case motor/generator
562. Driveline systems employing hydraulic pump/motors preferably employ
mechanical synchronization means such as plate clutches or synchronizer type dog
clutches to bring the rotating speeds of the rotating parts into synchronization
because the response time of a pump/motor to speed control commands is
significantly greater that that of an electric motor.
[0042] As with the hydraulic system, alternative embodiments of the electric
hybrid system are anticipated. Examples of alternative configurations are shown in
Figures 8 through 10.
We claim:
1. A drivetrain for a motor vehicle comprising:
an automated, mechanical transmission having an input shaft and an output
shaft and a counter shaft and a first gear disposed between the inputs shaft
and the countershaft arid at least two selectively engageable gear sets
disposed between the countershaft and the output shaft;
an alternative power source including a motor and an energy storage unit; and
an adapter module operable disposed between the automated mechanical
transmission and the motor and including
an adapter gear set including a first gear in mesh with a second gear,
providing driving connections between the motor and the transmission
output shaft;
a first clutch selectively drivingly connecting the motor input shaft to the
countershaft;: and
a second clutch selectively connecting the output shaft to the motor
input shaft through the adapter gear set,
2. A drivetrain as claimed in claim 1 wherein the second clutch is a multiplate clutch
enabling a transmission of torque between the associated gear and shaft while there
is slippage across the clutch.
3. A drivetrain as claimed in claim 1 wherein each of the first and second clutches is
a non-synchronized dogr-lothed clutch.
4. A transmission suited for use with a hydraulic launch system, the transmission
comprising;
an input shaft;
an output shaft;
a counter shaft;
a first gear set disposed between the inputs shaft and the countershaft;
at least two selectively engageable gear sets disposed between the
countershaft and the output shaft; and
an adapter module operable including
an adapter gear set including a first gear in mesh with a second gear,
providing driving connections between the motor and the transmission
output shaft;
a, first clutch selectively drivingty connecting the motor input shaft to the
countershaft; and
a second clutch selectively connecting the output shaft to the motor
input shaft through the adapter gear set,
5. A transmission as claimed in claim 4 wherein the second clutch is a multiplate
clutch enabling a transmission of torque between the associated gear and shaft while
there is slippage across the clutch.
6. A transmission as claimed in claim 4 wherein each of the first and second clutches
is a non-synchronized dog-toothed clutch.

ABSTRACT

The present application relates to a drivetrain for a motor vehicle comprising
an automated mechanical transmission (12) having an input shaft (28), an
output shaft (30), a counter shaft (32) and at least two selectively engageable
gear sets disposed between the countershaft and the output shaft. In order to
assist in launching the vehicle, the application provides an alternative power
source including a motor (50) and an energy storage unit (52, 54) and an
adapter module (20) operable disposed between the automated mechanical
transmission (12) and the motor (50). Said module (20) comprises an adapter
gear set including a first gear (42) in mesh with a second gear (44),
providing driving connections between the motor (50) and the transmission
output shaft (30), a first clutch (46) selectively drivingly connecting the
motor input shaft (38) to the countershaft (32) and a second clutch (44)
selectively connecting the transmission output shaft (30) to the motor input
shaft (38) through the adapter gear set (42, 44). The motor (50) may be
hydraulic or electric.