U.S. patent application number 14/160187 was filed with the patent office on 2014-05-15 for direct power reversing drive axle.
This patent application is currently assigned to NACCO Materials Handling Group, Inc.. The applicant listed for this patent is NACCO Materials Handling Group, Inc.. Invention is credited to Chenyao CHEN, Robert Lee CHESS, John ROWLEY.
Application Number | 20140135170 14/160187 |
Document ID | / |
Family ID | 42224500 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140135170 |
Kind Code |
A1 |
CHESS; Robert Lee ; et
al. |
May 15, 2014 |
DIRECT POWER REVERSING DRIVE AXLE
Abstract
A drive axle assembly includes a drive axle configured to rotate
with a driving torque, a first clutch pack assembly located at an
end of the drive axle, and a second clutch pack assembly located at
an opposite end of the drive axle. A first drive wheel assembly is
operatively connected to the first clutch pack assembly, wherein
the first clutch pack assembly is configured to convert the driving
torque of the drive axle to a first driving torque of the first
drive wheel. A second drive wheel assembly is operatively connected
to the second clutch pack assembly, wherein the second clutch pack
assembly is configured to convert the driving torque of the drive
axle to a second driving torque of the second drive wheel.
Inventors: |
CHESS; Robert Lee;
(Troutdale, OR) ; CHEN; Chenyao; (Portland,
OR) ; ROWLEY; John; (Tigard, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NACCO Materials Handling Group, Inc. |
Fairview |
OR |
US |
|
|
Assignee: |
NACCO Materials Handling Group,
Inc.
Fairview
OR
|
Family ID: |
42224500 |
Appl. No.: |
14/160187 |
Filed: |
January 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13202165 |
Aug 18, 2011 |
8651205 |
|
|
PCT/US2010/025324 |
Feb 25, 2010 |
|
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14160187 |
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61155995 |
Feb 27, 2009 |
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Current U.S.
Class: |
477/79 |
Current CPC
Class: |
B60W 10/02 20130101;
B62D 11/08 20130101; B62D 11/24 20130101; B60W 10/10 20130101; B66F
9/07572 20130101; Y10T 477/641 20150115; B66F 9/07568 20130101 |
Class at
Publication: |
477/79 |
International
Class: |
B60W 10/02 20060101
B60W010/02; B60W 10/10 20060101 B60W010/10 |
Claims
1-21. (canceled)
22. A method, comprising: monitoring a vehicle steering angle;
engaging a first clutch pack assembly associated with a first drive
wheel located on a first side of a motorized vehicle, wherein an
engagement force of the first clutch pack assembly is determined,
at least in part, from the monitored vehicle steering angle;
applying a first driving torque to the first drive wheel in a
selected direction of vehicle travel; engaging a second clutch pack
assembly associated with a second drive wheel located on a second
side of the motorized vehicle, wherein an engagement force of the
second clutch pack assembly is determined, at least in part, from
the monitored vehicle steering angle; and applying a second driving
torque to the second drive wheel in the selected direction of
vehicle travel, wherein the second driving torque is different than
the first driving torque.
23. The method of claim 22, wherein the second driving torque
applied to the second drive wheel is greater than the first driving
torque applied to the first drive wheel during a first vehicle
steering angle associated with a vehicle turning radius, and
wherein both the first and second drive wheels are engaged in the
selected direction of vehicle travel.
24. The method of claim 23, further comprising reducing the first
driving torque to zero during a second vehicle steering angle
associated with a smaller vehicle turning radius than the first
vehicle steering angle.
25. The method of claim 24, further comprising applying a reverse
driving torque to the first drive wheel during a third vehicle
steering angle associated with a smaller vehicle turning radius
than the second vehicle steering angle.
26. The method of claim 22, further comprising monitoring
rotational speeds of both the first and second drive wheels,
wherein the engagement forces of the first and second clutch pack
assemblies are independently determined, at least in part, from the
monitored rotational speeds.
27. The method of claim 26, wherein the monitored rotational speed
of the first and second drive wheels indicates that the second
wheel is slipping.
28. The method of claim 27, wherein the engagement of the first
clutch pack assembly and of the second clutch pack assembly is
adjusted to reduce slipping of the second wheel in response to an
indication that the second wheel is slipping.
29. The method of claim 22, wherein engaging the first clutch pack
assembly comprises selectively engaging a first forward clutch or a
first reverse clutch of the first clutch pack assembly associated
with the selected direction of vehicle travel, and wherein engaging
the second clutch pack assembly comprises selectively engaging a
second forward clutch or a second reverse clutch of the second
clutch pack assembly associated with the selected direction of
vehicle travel.
30. The method of claim 22, wherein the second driving torque is
substantially equal to the first driving torque for a first vehicle
steering angle, and wherein the second driving torque is different
than the first driving torque for a second vehicle steering
angle.
31. A method comprising: generating a driving torque associated
with a vehicle; applying the driving torque to a drive axle to
cause the drive axle to rotate in an initial direction of rotation,
wherein the initial direction of rotation is associated with a
direction of vehicle travel selected from a forward direction and a
reverse direction, and wherein the drive axle is operatively
coupled to both a first drive wheel located on a first side of the
vehicle and a second drive wheel located on a second side of the
vehicle; selectively transferring, at a vehicle steering angle, a
first portion of the driving torque to the first drive wheel in the
initial direction of rotation; and selectively transferring, at the
vehicle steering angle, a second portion of the driving torque to
the second drive wheel in the initial direction of rotation,
wherein the first portion corresponds to a different amount of the
driving torque than the second portion.
32. The method of claim 31, further comprising: applying a braking
force, at a second vehicle steering angle, to the first drive
wheel, wherein the second vehicle steering angle is greater than
the vehicle steering angle at which the first portion of the
driving torque is selectively transferred to the first drive wheel;
and while braking the first drive wheel, transferring substantially
all of the driving torque to the second drive wheel in the initial
direction of rotation.
33. The method of claim 31, further comprising: selectively
transferring, at the vehicle steering angle, the first portion of
the driving torque to the first drive wheel in a second direction
of rotation of the drive axle, wherein the second direction of
rotation is opposite to the initial direction of rotation; and
selectively transferring, at the vehicle steering angle, the second
portion of the driving torque to the second drive wheel in the
second direction of rotation.
34. The method of claim 32, further comprising: monitoring the
vehicle steering angle; and varying one or both of the first
portion of the driving torque and the second portion of the driving
torque based, at least in part, on the monitored vehicle steering
angle.
35. The method of claim 34, wherein varying one or both of the
first portion of the driving torque and the second portion of the
driving torque comprises, in response to determining that the
monitored vehicle steering angle is increasing: increasing the
second portion of the driving torque; and decreasing the first
portion of the driving torque.
36. The method of claim 34, wherein varying one or both of the
first portion of the driving torque and the second portion of the
driving torque comprises, in response to determining that the
monitored vehicle steering angle is increasing: maintaining the
second portion of the driving torque approximately constant, and
decreasing the first portion of the driving torque.
37. The method of claim 34, further comprising determining that the
monitored vehicle steering angle is approaching a predetermined
vehicle steering angle, and wherein varying one or both of the
first portion of the driving torque and the second portion of the
driving torque comprises: increasing the second portion of the
driving torque to approach a same torque value as the driving
torque applied to the drive axle at the predetermined vehicle
steering angle; and decreasing the first portion of the driving
torque to approach a zero torque value at the predetermined vehicle
steering angle.
38. The method of claim 37, wherein increasing the second portion
of the driving torque comprises linearly increasing the second
portion of the driving torque toward the same torque value as the
driving torque applied to the drive axle, and wherein decreasing
the first portion of the driving torque comprises linearly
decreasing the first portion of the driving torque toward the zero
torque value.
39. The method of claim 34, wherein varying one or both of the
first portion of the driving torque and the second portion of the
driving torque comprises partially slipping one or more clutch pack
arrangements.
40. A method comprising: receiving one or more operator inputs and
vehicle parameters; commanding a motor to generate a driving
torque, wherein a drive axle is operatively coupled to the motor to
rotate in a rotational direction for transmission of the driving
torque, wherein a first drive wheel is located proximate an end of
the drive axle, and wherein a second drive wheel is located
proximate an opposite end of the drive axle; commanding a first
clutch arrangement operatively connected to the drive axle to
provide a first portion of the driving torque to rotate the first
drive wheel in the rotational direction; commanding a second clutch
arrangement operatively connected to the drive axle to provide a
second portion of the driving torque to rotate a second drive wheel
in the rotational direction; and selectively operating the first
clutch arrangement and the second clutch arrangement to provide
varying amounts of the driving torque to rotate the first drive
wheel and the second drive wheel based on the one or more operator
inputs and vehicle parameters.
41. The method of claim 40, further comprising: selecting the first
clutch arrangement from a first forward clutch arrangement and a
first reverse clutch arrangement based, at least in part, on the
one or more operator inputs and vehicle parameters; and selecting
the second clutch arrangement from a second forward clutch
arrangement and a second reverse clutch arrangement based, at least
in part, on the one or more operator inputs and vehicle parameters,
wherein the rotational direction corresponds with both the selected
first clutch arrangement and the selected second clutch
arrangement.
42. The method of claim 40, further comprising detecting a steering
angle, wherein selectively operating the first clutch arrangement
and the second clutch arrangement comprises providing substantially
equal portions of the driving torque to both the first drive wheel
and the second drive wheel in response to detecting that the
steering angle is in a first range of steering angles.
43. The method of claim 42, wherein selectively operating the first
clutch arrangement and the second clutch arrangement comprises
providing less driving torque to the first drive wheel as compared
to the second drive wheel in response to detecting that the
steering angle is greater than the first range of steering
angles.
44. The method of claim 43, wherein providing less driving torque
to the first drive wheel comprises providing substantially zero
driving torque to the first drive wheel, and wherein the second
portion of the driving torque provided to the second drive wheel is
substantially equal to the driving torque generated by the motor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/202,165, filed Aug. 18, 2011, which is a national stage
entry of International Patent Application No. PCT/US2010/025324,
filed Feb. 25, 2010, which claims priority to U.S. Provisional
Patent Application No. 61/155,995, filed on Feb. 27, 2009, the
contents of which are hereby incorporated by reference in their
entirety.
BACKGROUND
[0002] There is demand to reduce the operator control effort on
fork lift trucks, for example by the reduction or elimination of
the service brake effort, which taxes the drivers with continual
brake applications during normal operation. Furthermore, park brake
levers may wear out and require regular maintenance. By augmenting
or replacing the service brakes and/or the parking brakes with
clutch pack braking, the above issues regarding operator effort and
brake maintenance may be addressed.
[0003] Conventional drive axle differentials apply approximately
equal driving torque to the drive wheels, for example during tight
turns. This tends to force the truck to drive straight forward
applying extra loads to the drive train, inside drive tire, and
steer tires, which robs power from the hydraulic system during
hoisting, wastes fuel and adds to the driver's steering effort.
Transmission systems that include clutch packs in the drive axle
include separate service brakes, separate park brake and a
differential. See, for example, U.S. Pat. No. 7,090,608. Other
transmission arrangements that disconnect the engine while
providing clutch pack braking also include service brakes, a park
brake system and a differential.
[0004] The present invention addresses these and other
problems.
SUMMARY OF THE INVENTION
[0005] A motorized vehicle is herein disclosed as comprising a
drive axle, a transmission system configured to apply a driving
torque to the drive axle, and a first clutch pack assembly located
between the drive axle and an inner drive wheel, wherein the first
clutch pack assembly transfers a first portion of the driving
torque to the inner drive wheel. The motorized vehicle further
comprises a second clutch pack assembly located between the drive
axle and an outer drive wheel, wherein the second clutch pack
assembly transfers a second portion of the driving torque to the
outer drive wheel, and wherein the first portion corresponds to a
different amount of driving torque than the second portion.
[0006] A drive axle assembly is herein disclosed as comprising a
drive axle configured to rotate with a driving torque, first clutch
pack assembly located at an end of the drive axle, and a second
clutch pack assembly located at an opposite end of the drive axle.
A first drive wheel assembly is operatively connected to the first
clutch pack assembly, wherein the first clutch pack assembly is
configured to convert the driving torque of the drive axle to a
first driving torque of the first drive wheel. A second drive wheel
assembly is operatively connected to the second clutch pack
assembly, wherein the second clutch pack assembly is configured to
convert the driving torque of the drive axle to a second driving
torque of the second drive wheel, and wherein the first driving
torque is greater than the second driving torque.
[0007] A method is herein disclosed, comprising monitoring a
vehicle steering request, and engaging a first clutch pack assembly
associated with an inner drive wheel located on a first side of a
motorized vehicle, wherein an engagement force of the first clutch
pack assembly is determined, in part, from the vehicle steering
request. The method further comprises applying a first driving
torque to the inner drive wheel, and engaging a second clutch pack
assembly associated with an outer drive wheel located on a second
side of the motorized vehicle, wherein an engagement force of the
second clutch pack assembly is determined, in part, from the
vehicle steering request. A second driving torque is applied to the
outer drive wheel, wherein the second driving torque is different
than the first driving torque.
[0008] The foregoing and other objects, features and advantages of
the invention will become more readily apparent from the following
detailed description of a preferred embodiment of the invention
which proceeds with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates a simplified block diagram of a motorized
vehicle comprising a drive axle, a transmission system, a first
clutch pack assembly located between the drive axle and a first
drive wheel, and a second clutch pack assembly located between the
drive axle and a second drive wheel.
[0010] FIG. 2 illustrates a simplified example drive axle assembly
comprising a drive axle, a first drive wheel assembly operatively
connected to a first clutch pack assembly, and a second drive wheel
assembly operatively connected to a second clutch pack
assembly.
[0011] FIG. 3 illustrates an example block diagram of a
transmission control system comprising first and second clutch pack
assemblies.
[0012] FIG. 4 illustrates an example spring applied clutch pack
assembly located adjacent a drive wheel.
[0013] FIG. 5 is a diagram illustrating a vehicle comprising a
drive axle assembly and steer axle.
[0014] FIG. 6 illustrates an example block diagram of a
transmission control system comprising a vehicle system manager and
operator controls.
[0015] FIG. 7 illustrates an example diagram of drawbar pull
distribution at a first range of vehicle travel speed.
[0016] FIG. 8 illustrates an example diagram of drawbar pull
distribution at a second range of vehicle travel speed.
[0017] FIG. 9 illustrates a method of engaging a transmission
comprising two clutch pack assemblies.
[0018] FIG. 10 illustrates an example planetary and clutch pack
assembly associated with a drive wheel transmission system.
DETAILED DESCRIPTION
[0019] FIG. 1 illustrates a simplified block diagram of a motorized
vehicle 10 comprising a drive axle assembly 15 and a transmission
system 4 configured to apply a driving torque to a drive axle or
drive shaft 6 of the drive axle assembly 15. The motorized vehicle
10 may comprise an industrial truck, forklift, off-road vehicle, or
any other type of vehicle which is otherwise understood to be
operable with a conventional transmission system. A first clutch
pack assembly 11 is located between the drive shaft 6 and a first
drive wheel 1, wherein the first clutch pack assembly 11 is
configured to transfer a first portion of the driving torque to the
first drive wheel 1. A second clutch pack assembly 13 is located
between the drive shaft 6 and a second drive wheel 3.
[0020] Braking and turning requirements may be sensed by a truck
controller, or vehicle system manager 5, using position sensors to
determine the driver's intention and truck dynamics, using speed
and pressure sensors. The vehicle system manager (VSM) 5 may
receive input from one or more of a transmission sensor 2A,
steering sensor 2B, right wheel rotation (RWR) sensor 2C, and left
wheel rotation (LWR) sensor 2D. Accordingly, VSM 5 is able to both
receive input and send instructions or commands to the transmission
system 4, including the first and second clutch pack assemblies 11,
13.
[0021] Steer axle turning-effort and traction control limits may be
effectively directed by the VSM 5. Computer control of the first
and second clutch pack assemblies 11, 13 mounted on each end of the
drive shaft 6 eliminate the need for the differential used by
conventional transmission systems. By separately controlling an
amount of the driving torque provided to the left and right drive
wheels, the first drive wheel 1 may be made to rotate at a faster
speed than the second drive wheel 3. In other words, a first
portion of the driving torque transferred from the drive shaft to
the first drive wheel 1 may be different than a second portion of
the driving torque transferred to the second drive wheel 3, both
with respect to absolute value and rotational direction.
[0022] In various embodiments described herein, the first drive
wheel 1 may alternately be referred to as an inner drive wheel, or
a left drive wheel. The second drive wheel 3 may alternately be
referred to as an outer drive wheel, or a right drive wheel.
However, which drive wheel is an inner, outer, left, or right drive
wheel is dependent in part on a direction of vehicle travel and a
steering direction of the vehicle. Accordingly, one skilled in the
art would appreciate that either the first or second drive wheels
1, 3 may alternately be referred to as any of the inner, outer,
left, or right drive wheels depending on the embodiment or
operating condition being described.
[0023] Transmission system 4 transmits power from an engine to the
drive shaft 6 as transmission torque (TT). The transmission torque
causes a rotation of the drive shaft 6 about its axis of rotation.
In an embodiment where the transmission system 4 does not include
any differential, the rotation of the drive shaft 6 in response to
the transmission torque is in the same direction of rotation.
Rotational direction control of the first and second drive wheels
1, 3 is independently controlled by the first and second clutch
pack assemblies 11, 13. The first clutch pack assembly 11 causes
the first drive wheel 1 to rotate in either the same rotational
direction, or in an opposite direction of rotation, as the drive
shaft 6. Similarly, the second clutch pack assembly 13 causes the
second drive wheel 3 to rotate in either the same rotational
direction, or in the opposite direction of rotation, as the drive
shaft 6.
[0024] In one mode of operation, both first and second drive wheels
1, 3 concurrently rotate in the same rotational direction of the
drive shaft 6, and in another mode of operation, the first and
second drive wheels 1, 3 both rotate in the opposite direction of
rotation of the drive shaft 6. In yet another mode of operation,
the first drive wheel 1 rotates in an opposite direction of
rotation from the second drive wheel 3.
[0025] Whereas the clutch pack assemblies 11, 13 are described in
certain embodiments as being located on the drive shaft 6, they
could also be located on an axle that both provides traction
control and controls steering. For example, the clutch pack
assemblies 11, 13 could be installed on a vehicle which includes a
steerable drive axle. Similarly, the clutch pack assemblies 11, 13
could be located on either a front or rear axle of the vehicle 10.
In one embodiment, clutch pack assemblies 11, 13 are installed on
both the front and rear of a vehicle equipped with both front and
rear wheel drive.
[0026] FIG. 2 illustrates a simplified example drive axle assembly
such as the drive axle assembly 15 of FIG. 1. The drive axle
assembly comprises a drive shaft 6 which is configured to rotate
with a driving torque, a first clutch pack assembly 20 located at a
first end of the drive shaft 6, and a second clutch pack assembly
25 located at second end of the drive shaft 6, opposite the first
end. A first drive wheel assembly comprising the first drive wheel
1 is operatively connected to the first clutch pack assembly 20,
and a second drive wheel assembly comprising the second drive wheel
3 is operatively connected to the second clutch pack assembly
25.
[0027] The first clutch pack assembly 20 comprises a first forward
clutch pack 26 and a first reverse clutch pack 28. The second
clutch pack assembly 25 comprises a second forward clutch pack 27
and a second reverse clutch pack 29. Separate planetary gearing is
provided for each of the first clutch pack assembly 20 and the
second clutch pack assembly 25. Planetary gearing associated with
the first drive wheel assembly and the first clutch pack assembly
20 comprises a first reverse planetary 22 and a first forward
planetary 24, whereas a second reverse planetary 21 and second
forward planetary 23 are associated with the second drive wheel
assembly and the second clutch pack assembly 25.
[0028] The planetary gearing is configured to cause the drive
wheels 1, 3 to rotate in a reverse or forward direction according
to which of the clutch packs 26-29 are engaged, or according to the
relative amount of clutch pack slipping as between the respective
forward and reverse clutch packs. The planetaries operate to
transmit all, or a portion, of the transmission torque operating on
the drive shaft 6 to one or both of the drive wheels 1, 3. The
drive wheels 1, 3 may be disengaged from the drive shaft 6, such
that neither drive wheel 1, 3 rotates while the drive shaft 6 is
rotating.
[0029] Actuation of a brake pedal may be used to modulate the
clutch pack braking by simultaneously applying the forward and
reverse clutch packs. For example, first forward clutch pack 26 and
first reverse clutch pack 28 may be simultaneously engaged, or
partially engaged, to provide for clutch pack braking of the first
drive wheel 1. The first forward clutch pack 26 and the first
reverse clutch pack 28 may both be in a condition of performing
clutch pack slipping in the partially engaged mode of operation, in
which case both clutch packs 26, 28 may be used to absorb braking
heat or to share the braking energy between the clutch packs.
[0030] The first and second driving torques of the first and second
drive wheels 1, 3 are varied by slipping the respective first and
second clutch pack assemblies 20, 25. In one embodiment, one of the
clutch packs 26, 28 may be allowed to slip to a greater degree. For
example, the first reverse clutch pack 28 may be allowed to slip
more than the first forward clutch pack 26 during clutch pack
braking while the motorized vehicle 10 is moving in a forward
direction. Similarly, second forward clutch pack 27 and second
reverse clutch pack 29 may be simultaneous engaged, or partially
engaged, to provide for clutch pack braking of the second drive
wheel 3. The first forward clutch pack 28, the second forward
clutch pack 27, and the second reverse clutch pack 29 may be
simultaneously slipped. Clutch pack braking of the first clutch
pack assembly 20 may be made independently from the second clutch
pack assembly 25. Systems for clutch pack braking and clutch pack
slipping are described by U.S. Pat. No. 6,684,148, herein
incorporated by reference in its entirety.
[0031] FIG. 3 illustrates an example block diagram of a
transmission control system 30 and the drive axle assembly 15. The
drive axle assembly 15 comprises a drive axle or drive shaft 6
configured to rotate with the driving torque provided by the engine
32 via the transmission control system 30. The drive axle assembly
15 further comprises the first clutch pack assembly 11 located at
an end of the drive shaft 6 and the second clutch pack assembly 13
located at an opposite end of the drive shaft 6.
[0032] A drive wheel assembly comprising the first drive wheel 1 is
connected to the first clutch pack assembly 11, wherein the first
clutch pack assembly 11 is configured to convert the driving torque
of the drive shaft 6 to a first driving torque of the first drive
wheel 1. A drive wheel assembly comprising the second drive wheel 3
is connected to the second clutch pack assembly 13, wherein the
second clutch pack assembly 13 is configured to convert the driving
torque of the drive shaft 6 to a second driving torque of the
second drive wheel 3. In one mode of operation, the first driving
torque is greater than the second driving torque. In another mode
of operation, the second driving torque is greater than the first
driving torque. The first driving torque may be in a same direction
of rotation as the second driving torque, or in an opposite
direction of rotation.
[0033] The first clutch pack assembly 11 may be associated with a
left side of the drive shaft 6, such that the first drive wheel 1
could be considered a left drive wheel with a left wheel rotation
(LWR). Similarly, the second clutch pack assembly 13 may be
associated with a right side of the drive shaft 6, such that the
second drive wheel 3 could be considered a right drive wheel with a
right wheel rotation (RWR). According to one embodiment, the first
clutch pack assembly 11 further comprises a forward left valve V4
and reverse left valve V5 that are operable to provide hydraulic
pressure to the forward and reverse clutches of the first clutch
pack assembly 11. A forward left pressure gauge or pressure sensor
S4 is provided to monitor a hydraulic pressure in the forward
clutch left (such as forward clutch 26 in FIG. 2), whereas a
reverse left pressure sensor S5 is provided to monitor a hydraulic
pressure in the reverse clutch left (such as first reverse clutch
28 in FIG. 2).
[0034] The second clutch pack assembly 13 comprises a forward right
valve V6 and reverse right valve V7 that are operable to provide
hydraulic pressure to the forward and reverse clutches of the
second clutch pack assembly 13. A forward right pressure gauge or
pressure sensor S6 is provided to monitor a hydraulic pressure in
the forward clutch right (such as second forward clutch 27 in FIG.
2), whereas a reverse right pressure sensor S7 is provided to
monitor a hydraulic pressure in the reverse clutch right (such as
second reverse clutch 29 in FIG. 2).
[0035] A travel speed left wheel sensor S8 is provided to monitor
the left wheel rotation LWR of the first drive wheel 1 about the
centerline CL of the drive shaft 6, whereas the travel speed right
wheel sensor S9 is provided to monitor the right wheel rotation RWR
of the second drive wheel 3 about the centerline CL of the drive
shaft 6.
[0036] The transmission control system 30 comprises a torque
convertor 33 configured to convert engine torque generated by the
engine 32 to a rotational torque applied to the transmission output
shaft 36. The transmission control system 30 further comprises an
inching clutch 34 and a drop box 35 connected to the transmission
output shaft 36. Transmission output shaft 36 is operatively
connected to the drive axle via transmission gearing 38. In one
embodiment, transmission gearing 38 comprises a plurality of
beveled gears configured to cause the drive shaft 6 to continuously
rotate anytime the transmission output shaft 36 rotates.
[0037] Engine RPM sensor S1 is provided to monitor the engine
speed, or number of revolutions per minute, to gauge the power
being generated by the engine 32, independent of a rotation of the
transmission output shaft 36. Inching clutch 34 may be configured
to disengage the engine 32 from the transmission output shaft 36,
such that the power of engine 32 may be used during inching
operations or to power hydraulic operations or hydraulic pumps
associated with a hoist function in an industrial lift truck. The
gearing within the transmission gearing 38 may remain engaged with
each other even when the engine 32 is disengaged from the
transmission output shaft 36. In one embodiment, the transmission
gearing 38 remains constantly engaged at all times.
[0038] Inching clutch pressure sensor S2 is provided to monitor a
hydraulic pressure of the inching clutch 34, whereas inching clutch
valve V2 is operable to provide hydraulic pressure to the inching
clutch 34, for example, to disengage or partially disengage the
engine 32 from the transmission output shaft 36. Torque converter
output speed sensor S3 is provided to monitor the rotational speed
of the transmission output shaft 36.
[0039] When driving normally, for example in a forward direction,
only three clutch packs are fully engaged to reduce the
transmission drag, namely the three clutch packs include the
inching clutch pack and the two forward clutch packs. Similarly,
when driving in reverse, only the inching clutch pack and the two
reverse clutch packs may be fully engaged.
[0040] Positive traction of the vehicle may be maintained without
either tire spinning when traversing gravel or on ice. The need for
differential driving action is sensed by steer tire turning angle.
When a small steering angle is requested (i.e. with a large turning
radius), the drive wheel torque of the inner and outer drive tires
is equalized together when traction is needed. If the outside wheel
is rotating too fast, slipping relative to the sensed steering
angle, the driving torque on the inside wheel can be modulated to
maintain traction. The torque on the inside tire is increased if
the outside tire is over running (slipping) the theoretical speed
calculated from the steering angle. During turns, the tire having
the greatest dynamic load (e.g. the outside tire) will have the
most power applied by virtue of the differential strategy
above.
[0041] The transmission control strategy is facilitated by
employing an inching clutch pack 34 on the engine mounted drop box
35. The engine may be disconnected during inching and simultaneous
decelerated by the clutch packs. Clutch pack braking may be
provided to slow the truck travel speed while simultaneously
operating the engine at a high revolution per minute (rpm) to
provide high hydraulic flows. This is further facilitated by the
inching clutch pack's ability to disconnect the engine from the
power train, so that the truck travel speed deceleration does not
load down the engine with drag. The inching clutch may be mounted
in other locations between the engine and the axle, than that shown
in FIG. 3.
[0042] Computer control of first clutch pack assembly 11, the
second clutch pack assembly 13, and the inching clutch 34
eliminates the need for the differential found in conventional
transmission systems. The differential is eliminated by selectively
slipping a selected direction clutch pack according to the measured
steer angle of the motorized vehicle. For example, assuming a
forward travel of the motorized vehicle with both forward clutches
fully engaged, and the vehicle is steered hard to the left. The
first clutch pack assembly 11 associated with the first drive wheel
1, or inside drive wheel, is allowed to slip such that the
rotational speed LWR of the first drive wheel 1 is decreased with
respect to the rotational speed RWR of the second drive wheel 3, or
outside drive wheel. Independent control of the rotational speeds
LWR, RWR of the first and second drive wheels 1, 3 is therefore
accomplished without the need for a conventional differential.
[0043] The separate inching clutch 34 is configured to adjust the
driving torque provided to the transmission output shaft 36
independent of engine speed and braking action provided by the
clutch packs 11, 13 when the engine 32 is used to power the
hydraulic system. Accordingly, this system allows automatic
throttle-up of engine speed in response to operator hydraulic
demand without requiring an increased driving torque to the
transmission output shaft 36 or drive shaft 6.
[0044] A conventional differential is not required. The
differential may be eliminated, gears and all, while being replaced
by a fixed gearing element. This is made possible by having the
ability to slip right and left clutches at different rates to
accommodate different wheel speeds while turning the vehicle.
Functionality of the conventional differential action is
accomplished by computer control of the direction clutch packs in
the drive axle.
[0045] The differential action comes from the VSM (Vehicle System
Manager 5 in FIG. 1) selectively slipping the right and left
driving clutch packs based on steer tire angle and individual drive
axle wheel speed. The drive clutch pack pressure may be adjusted by
momentary slip action to maintain optimum pack pressures for
differential strategy. By only applying the torque/pressure needed,
the inside-pack slip losses are limited and fuel efficiency is
maximized.
[0046] The system limits inside wheel slip horsepower to a minimal
hp loss; e.g., less than 5.0 hp. Clutch pack pressures may be
controlled according to the clutch pack slip speed and pressure
(torque) on the inside wheel pack to calculate losses. The clutch
pack slip speed may be calculated by sensing the corresponding
wheel speed and taking the ratio between wheel speed and clutch
pack speed and comparing it to the axle shaft speed. Other methods
of determining clutch pack slip are possible.
[0047] Increased engine compartment space is achieved by reducing
the size of the transmission housing, since it no longer contains
direction or range clutch packs and gears. The transmission is
simplified to include a drop box, a converter cover, and a pump
drive. Access to the power take off is improved, because of the
increased engine compartment space.
[0048] Elimination of one or more of the following devices and
apparatus is achieved by the system described herein: differential,
service and park brake parts, brake-booster, conventional brake
lines, wet disk brake cooling lines, park brake cables and
actuators, and a transmission control valve.
[0049] Elimination of the devices and apparatus also increases
space available for plumbing routing. Spiral bevel gears and
bearings may be used in the location where the differential would
have been, function to reduce shock loads since there is no longer
any requirement for power reversal loads on the drive train. There
are no power reversal loads transmitted through this gear set,
because the power reversal forces are taken up by the forward and
reverse clutches in the axle.
[0050] FIG. 4 illustrates an example spring applied clutch pack
assembly 40 located adjacent a drive wheel, such as first drive
wheel 1. A similar and separate assembly may be provided for the
second drive wheel 3 (FIG. 3). In one embodiment, the spring
applied clutch pack assembly 40 comprises one or more Spring
Applied Hydraulically Released (SAHR) devices 45 that engages the
clutch packs 46, 48 when hydraulic power is removed, or when the
motorized vehicle is powered off. The SAHR device 45 may be
configured to provide sufficient power to enable vehicle braking
via the clutch packs 46, 48 to bring the motorized vehicle to a
controlled stop independent of any operation of brakes.
[0051] In one embodiment, the drive axle assembly 15 in FIG. 1 is
placed into a hold mode (to decelerate and stop the vehicle)
whenever the driver removes his feet from the foot controls (e.g.
inching pedal and/or acceleration pedal) by simultaneously engaging
forward and reverse clutch packs. A vehicle system comprising
clutch pack braking and the spring applied clutch pack assembly 40
operates to replace or provide the same functionality as service
brakes and the park brake found in conventional vehicle operating
systems. A system comprising a spring applied brake and drive
assembly is described by U.S. patent application Ser. No.
12/388,713, herein incorporated by reference in its entirety.
[0052] Service and park brakes are not required. Braking is
provided by the direction clutch packs. Conventional service and
park brakes are grounded to the drive axle and require associated
brake linkage. Conventional brakes and the associated linkage are
eliminated.
[0053] Actuation of the direction clutch packs may be provided by
Spring Applied Hydraulically Released (SAHR) design. Truck travel
deceleration may be achieved by applying opposing direction clutch
packs (forward against reverse) on both the left and right sides of
the drive axle.
[0054] Braking is independent from side to side of the drive axle.
Braking energy may be divided between the forward and reverse
clutch packs by slipping all packs simultaneously or alternating in
a dithering action between forward and reverse clutch pack pairs.
The right forward and reverse clutch packs may alternately be
slipped with the left forward and reverse clutch packs.
Additionally, the left forward and right reverse clutch packs may
be alternately slipped with the left reverse and right forward
clutch packs. This divides the deceleration energy between the
clutch packs by promoting slipping in each clutch pack.
[0055] Park braking may be automatically applied when the driver
removes his feet from the foot controls. This is accomplished by
the spring applied clutch packs being depressurized when operator
request for travel is removed. The service brake function of the
clutch packs continues to work if deceleration control on one side
truck fails or there is a hydraulic failure.
[0056] FIG. 5 is a diagram illustrating a vehicle 50 comprising a
drive axle assembly 15 and steer axle 55, wherein a first driving
torque is applied to an inner drive wheel (e.g. first drive wheel
1) of the drive shaft 6, and wherein a second driving torque is
applied to the outer drive wheel (e.g. second drive wheel 3) of the
drive shaft 6. The first driving torque is illustrated as forward
driving torque FWD 1 about the drive axle centerline CL when the
inner drive wheel 1 is being rotated in a forward rotational sense,
or as reverse driving torque REV1 when the inner drive wheel 1 is
being rotated in a reverse rotational sense. The second driving
torque is illustrated as forward driving torque FWD2 about the
drive axle centerline CL when the outer drive wheel 3 is being
rotated in a forward rotational sense, or as reverse driving torque
REV2 when the outer drive wheel 3 is being rotated in a reverse
rotational sense.
[0057] When the vehicle 50 is being turned about center of rotation
R0, an inner turn radius R1 is associated with an inner steer wheel
51 of the steer axle 55, whereas an outer turn radius R2 is
associated with the outer steer wheel 53 of the steer axle 55. The
combined effect of the inner and outer turn radii R1, R2 determine
the overall steering angle of the vehicle 50. Steering angles of
the inner and outer steer wheels 51, 53 may be monitored by one or
more steer angles sensors 52, 54.
[0058] When both the first drive wheel 1 and the second drive wheel
3 are rotating in the same directional sense (e.g. in a forward
rotational sense), the second driving torque FWD2 may be equal to
the first driving torque FWD 1 when the vehicle is traveling
straight ahead, or in a first range of steering angles. In a second
range of steering angles, the second driving torque FWD2 is greater
than the first driving torque FWD1. The second range of steering
angles may be associated with a smaller range of turning radii of
the vehicle as compared to the first range of steering angles. In
one embodiment, the above comparison of the driving torques (or
rotational speeds) of the first and second driving torques FWD1 and
FWD2 assumes a same rate of vehicle travel speed.
[0059] Corresponding to an increased steering angle, the center of
rotation R0 of the vehicle approaches the centerline CL.sub.1 of
the inner drive wheel 1. When the center of rotation R0 coincides
with the centerline CL.sub.1 of the inner drive wheel 1, the
vehicle turns about the centerline CL.sub.1 of the inner drive
wheel 1. As the vehicle rotates about the centerline CL.sub.1 of
the inner drive wheel 1, the inner drive wheel 1 may be stationary,
such that it is not rotating. In one embodiment, the range of
steering angle of the vehicle comprises a first steering angle and
a second steering angle. When the steering angle changes from the
first steering angle to the second steering angle, the second
forward driving torque FWD2 of the outer drive wheel 3 approaches
the driving torque of the drive axle as the first forward driving
torque FWD 1 of the inner drive wheel 1 approaches zero torque.
[0060] The inner drive wheel 1 may be disengaged from the first
clutch pack 11 when the first forward driving torque FWD 1 equals
zero torque. In one embodiment, a zero torsional force is applied
to the inner drive wheel 1 when the center of rotation R0 of the
vehicle coincides with the centerline CL.sub.1 of the inner drive
wheel 1. Clutch pack braking may be applied to the inner drive
wheel 1 to control the driving torque FWD1 or keep the inner drive
wheel 1 from rotating. The inner drive wheel 1 may be braked via
clutch pack braking of the first clutch pack assembly 11 when the
second forward driving torque FWD2 equals the driving torque of the
drive shaft 6.
[0061] As the steering angle of the vehicle increases further
still, the center of rotation R0 approaches the centerline CL.sub.0
of the vehicle. The centerline CL.sub.0 of the vehicle is located
intermediate the centerline CL.sub.1 of the inner drive wheel 1 and
the centerline CL.sub.2 of the outer drive wheel 3. The distance
between the centerline CL.sub.1 of the inner drive wheel 1 and the
centerline CL.sub.2 of the outer drive wheel 3 is called a tread
width (TW) of the vehicle.
[0062] In a third range of steering angles, wherein the center of
rotation R0 lies within the tread width TW of the vehicle, a
reverse driving torque REV1 is applied to the inner drive wheel 1
while the forward driving torque FWD2 is applied to the outer drive
wheel 3. The reverse driving torque REV1 may be the same absolute
magnitude as the forward driving torque FWD2, but opposite in
rotational direction. At certain rates of vehicle travel, the
absolute magnitude of the reverse driving torque REV1 applied to
the inner drive wheel may be different than (i.e. less than or
greater than) the forward driving torque FWD2 applied to the outer
drive wheel 3. The relative amount of driving torque applied to the
inner drive wheel 1 and the outer drive wheel 3 is independently
controlled, respectively, by the first and second clutch pack
assemblies 11, 13.
[0063] One skilled in the art would appreciate that either the
first drive wheel 1 or the second drive wheel 3 may be considered
the inner drive wheel or the outer drive wheel depending on the
direction of the steering angle of the vehicle. For example, the
first drive wheel 1 is considered the inner drive wheel during a
forward left turn, whereas the second drive wheel 3 is considered
the inner drive wheel during a forward right hand turn. A forward
direction of travel, in one embodiment, is understood as the drive
shaft 6 being located at a front of the vehicle.
[0064] FIG. 6 illustrates an example block diagram of a
transmission control system comprising a vehicle system manager
(VSM) and operator controls. The operator controls comprise a
steering wheel 62, inch/brake pedal 64, accelerator pedal 66, and
throttle up levers 68. The VSM monitors or receives input from the
operator controls via an inch/brake pedal position sensor 65, an
accelerator pedal position sensor 67, and a throttle up demand
sensor 69. Steering angle of the vehicle may be monitored directly
from the steering wheel 62, or via one or more sensors 52, 54 that
identify a steering angle of the steer tires.
[0065] The VSM additionally monitors or receives input from the
engine RPM sensor S1, the inching clutch pressure sensor S2, the
torque converter output speed sensor S3, the forward left pressure
sensor S4, the reverse left pressure sensor S5, the forward right
pressure sensor S6, the reverse right pressure sensor S7, the
travel speed left wheel sensor S8, and the travel speed right wheel
sensor S9.
[0066] Based on the input from one or more of the sensors, the VSM
is configured to control the amount of torque transferred to the
left and right drive wheels 1, 3. The VSM can independently control
an amount of hydraulic pressure applied to each of the forward left
valve V4, reverse left valve V5, forward right valve V6, and
reverse right valve V7. The amount of hydraulic pressure applied to
the valves determines which clutch packs are engaged, partially
engaged, or disengaged. Similarly, the amount of hydraulic pressure
determines an amount of clutch pack slipping in one or more of the
clutches, or whether clutch pack braking is actuated.
[0067] By providing the on-board VSM with the input from the
various sensors, and the ability to control the amount of torque
and rotational speed of the drive wheels 1, 3, the vehicle may be
commanded to a stop from any velocity without the driver pressing
any pedals. Similarly, the vehicle may be held steady on an incline
without rolling, and without activation of a brake pedal, service
brake, or park brake. The vehicle remains stationary on the
inclined surface without any need to set a park brake, even when
the operator leaves the vehicle. Accordingly, there is also no need
to include a service brake or park brake on the vehicle. In one
embodiment, activation of the inch-brake pedal 64 is sensed by VSM
via the inch-brake pedal position sensor 65 to control an amount of
hydraulic pressure applied to one or more of the clutch pack valves
V4, V5, V6, V7 to apply clutch pack braking of one or both drive
wheels 1, 3 when the driver requests braking of the vehicle.
[0068] The zero-roll on a grade is an automatic function and
continues with the engine stopped. An engine or hydraulic system
failure causes automatic application of the braking function in a
controlled manner with a low deceleration rate. This may be
accomplished using orifices to control the stopping rate when the
system fails.
[0069] Independent control of the amount of torque and braking
applied to each drive wheel provides for improved maneuverability,
for example, around tight turns. In the event a first drive wheel 1
has little or no traction (e.g. when the vehicle is operating on
ice, wet pavement, gravel, etc.) traction control may be maintained
by diverting some or all of the driving torque to the second drive
wheel 3, until the first drive wheel 1 regains traction. In the
event of engine or computer failure or loss of hydraulic power, the
hydraulic pressure holding off the clutch packs is released,
allowing the spring applied braking to actuate. Simultaneous
application of forward and reverse direction clutches provides
braking. The forward direction clutch may be partially slipped at
the same time as the reverse direction clutch is partially slipped.
The inch/brake pedal has a hydraulic valve that provides hydraulic
supply to the clutch pack valves. Pressing the inch/brake pedal
starts dumping the supply pressure mechanically and starts the
spring application of the clutches, which causes braking. The
inch/brake pedal 64 has a hydraulic connection to the clutch packs
in the drive axle. When the inch/brake pedal 64 is pressed, the
pressures in the clutch packs 11, 13 are reduced to provide clutch
pack braking.
[0070] By having the forward and reverse clutches rotate at lower
speeds, this reduces parasitic drag of having forward and reverse
clutches counter rotating at high speed in a transmission. Roll
back of the vehicle located on an incline may be controlled when
performing throttle up, and the vehicle may be locked in place with
forward and reverse clutch packs engaged.
[0071] Controlled torque distribution between left and right drive
wheel assemblies may be achieved for the following example vehicle
operations: one wheel on ice and one wheel on pavement, sharp turn
pivot about inside drive wheel, sharp turn pivot about center line
of truck, vehicle travelling on slippery floor with both wheels
alternately gaining an losing traction, going uphill in snow, and
one wheel climbing out of muddy hole in the ground and the other
wheel on level ground.
[0072] FIG. 7 illustrates an example diagram of drawbar pull
distribution to the inner and outer drive wheel at a first range of
vehicle travel speed. For illustrative purposes only, the vehicle
travel speed is shown as being five to eight miles per hour. The
graph illustrates the relationship of percent of maximum drawbar
pull (% DBP) between the drive axle and the inner and outer drive
wheels for a range of vehicle turning radii. The drive axle DBP 75
is illustrated as being a constant 100% of DBP for vehicle turning
radii over zero feet. The DBP relationship is described using four
ranges of turning radius. A first range of turning radius 71
comprises turning radii of between 35 feet and 100 feet. In the
first range of turning radius 71, inner drive wheel DBP 76 is equal
or approximately equal to outer drive wheel DBP 78, illustrated as
being 50% of DBP. The sum of the inner drive wheel DPB 76 and the
outer drive wheel DBP 78 equals the drive axle DBP 75.
[0073] A second range of turning radius 72 is illustrated as
comprising turning radii of between 20 and 35 feet. In the second
range of turning radius 72, inner drive wheel DBP 76 decreases
linearly to zero torque as the turning radius decreases from the
first turning radius of 35 feet to the second turning radius of 20
feet. As the inner drive wheel DBP 76 linearly decreases to zero
torque, the outer drive wheel linearly increases until it is equal
to the drive axle DBP 75. At any particular turning radius in the
first and second range of turning radius 71, 72, the sum of the
inner and outer drive wheel torque equals the drive axle
torque.
[0074] In the illustrated embodiment, a first steering request or
first steering angle is associated with a vehicle turning radius in
the first range of turning radius 71, whereas a second steering
request or second steering angle is associated with the second
range of turning radius 72. The steering angle associated with the
second steering request is greater than the steering angle
associated with the first steering request. The drive axle torque
(or driving torque) may be divided into two portions, including a
first portion associated with the outer drive wheel DBP 78, and a
second portion associated with the inner drive wheel DBP 76.
[0075] The second portion of the driving torque decreases when the
steering angle of the motorized vehicle is changed from the first
steering angle to the second steering angle, wherein the first
portion of the driving torque increases when the steering angle of
the motorized vehicle is changed from the first steering angle to
the second steering angle. The second portion of the driving torque
approaches a same torque value as the driving torque applied to the
drive axle at a predetermined steering angle (e.g. shown as
occurring at a 20 foot turning radius), whereas the first portion
of the driving torque approaches a zero torque value at the
predetermined steering angle or turning radius.
[0076] In the first and second range of turning radius 71, 72 both
the first drive wheel and the second drive wheel may be understood
to be engaged in a forward direction of vehicle travel. The first
and second portions of the driving torque vary as a function of a
steering angle of the motorized vehicle.
[0077] A third range of turning radius 73 is illustrated as
comprising turning radii of between zero and 20 feet. In the third
range of turning radius 73 the inner drive wheel DBP 76 is held at
or near zero pounds torque, whereas the outer drive wheel DBP 78 is
held constant at the same torque value as the drive axle DBP 75. At
any particular turning radius in the third range of turning radius
73, the sum of the inner and outer drive wheel torque equals the
drive axle torque.
[0078] A fourth range of turning radius 74 is illustrated as
comprising turning radius of zero feet, or slightly less than zero
feet. A turning radius associated with zero feet is understood to
occur when the center of turning radius coincides with the
centerline of the vehicle (e.g. centerline CL.sub.0 of FIG. 5).
When the vehicle turns about its centerline at the zero feet
turning radius, inner drive wheel DBP 76 is made equal or
approximately equal to outer drive wheel DBP 78, illustrated as
being 50% of DBP, however the direction of rotation of the inner
drive wheel is opposite to that of the outer drive wheel. During a
forward turn about the vehicle centerline, the outer drive wheel is
rotated in a forward rotational sense, whereas the inner drive
wheel is rotated in a reverse rotational sense. At the zero feet
turning radius, the inner drive wheel is rotated with a rotational
velocity equal, but opposite in direction, to the outer drive
wheel.
[0079] The driving torque on the driving clutch pack corresponding
to the inside of a turn is progressively reduced as the turning
radius becomes smaller. If the turning radius becomes increasingly
smaller, the driving torque on the inside end of the drive axle
will be reversed enabling a turning center that is between the
wheels. Assume the vehicle is making a zero radius turn to the
left. As the steer angle in increased more and more the forward
left clutch is commanded to slip more and more until it is neutral
(no torque) when the turning center is at the left (inner) wheel.
As the turn angle increases and the turn center moves inboard of
the inner wheel then the reverse left clutch is commanded to
transmit torque. At this point the inner wheel begins turning in
reverse and the outer wheel is still turning forward. As the steer
angle continues to increase the reverse torque continues to be
increased on the inner wheel until finally the inner wheel is
turning in reverse at the same speed the outer wheel is turning
forward and the truck is in a zero radius turn. Turning can be
automatically assisted by braking on the inside wheel at
appropriate turning angles.
[0080] By balancing the driving power applied to the drive tires
during turns, the steer tires do not drag, reducing steer tire wear
and reducing fuel consumption. Steer tires are not dragged sideways
at near torque converter stall during small radius turns. The
steering effort is reduced due to by distributing the driving
torque to the driving wheels in proportion to the steer angle. A
reduction on inside drive tire drag is also reduced. The driving
torque is applied to the wheel on the outside of a turn where it
will be most effective. Turning and braking action closely emulates
the action achieved by dual drive motor axles on electric powered
lift trucks.
[0081] FIG. 8 illustrates an example diagram of drawbar pull
distribution to the inner and outer drive wheel at a second range
of vehicle travel speed. For illustrative purposes only, the
vehicle travel speed is shown as being between zero and four miles
per hour. As before, the DBP relationship is described using four
ranges of turning radius. The drawbar pull is again illustrated as
being 100% for the drive axle DBP 85. One skilled in the art would
appreciate that the maximum drawbar pull corresponding to 100% DBP
will vary for different travel speeds of the vehicle. In one
embodiment, the maximum DBP associated with the second range of
travel speed is approximately twice as great as the maximum DBP
associated with the first range of travel speed illustrated in FIG.
7.
[0082] In the first range of turning radius 81, inner drive wheel
DBP 76 is equal or approximately equal to outer drive wheel DBP 88,
illustrated as being 50% of DBP. In the first range of turning
radius 81, the sum of the inner drive wheel DPB 86 and the outer
drive wheel DBP 88 equals the driving torque provided by the drive
axle DBP 85.
[0083] In the second range of turning radius 82, inner drive wheel
DBP 86 decreases linearly to approximately 15% of DBP while the DBP
88 increases linearly to approximately 65% of DBP as the turning
radius decreases from the first turning radius of 35 feet to the
second turning radius of 20 feet. As the inner drive wheel DBP 86
linearly decreases, the outer drive wheel linearly increases. At
the second range of vehicle travel speed, the drive axle DBP 85
linearly decreases in the second range of turning radius 82 from
100% DBP to 80% DBP. However, as before, at any particular turning
radius in the first and second range of turning radius 81, 82, the
sum of the inner and outer drive wheel torque equals the drive axle
torque.
[0084] In the third range of turning radius 83 the inner drive
wheel DBP 86 is held at a constant torque value greater than zero,
whereas the outer drive wheel DBP 88 is held constant at a torque
value less than that of the drive axle DBP 85. At any particular
turning radius in the third range of turning radius 83, the sum of
the inner and outer drive wheel torque equals the drive axle
torque.
[0085] Whereas the driving torque applied to the inner drive wheel
was held at zero torque for the higher vehicle travel speed of FIG.
7, in the present embodiment, the inner drive wheel is provided
driving torque to increase vehicle traction at the lower vehicle
travel speeds.
[0086] In the fourth range of turning radius 84 (illustrated as
comprising turning radius of zero feet) inner drive wheel DBP 86 is
made equal or approximately equal to outer drive wheel DBP 88. This
relates to an overall increase in driving torque of the drive axle,
illustrated as the drive axle DBP 85 increasing back up to 100%
DBP. The direction of rotation of the inner drive wheel is opposite
to that of the outer drive wheel. At the zero feet turning radius,
the inner drive wheel is rotated with a rotational velocity equal,
but opposite in direction, to the outer drive wheel.
[0087] FIG. 9 illustrates a method 900 of engaging a transmission
comprising two clutch pack assemblies. At operation 910, a vehicle
steering request is monitored. The vehicle steering request may be
monitored via input from a steering device or from the one or more
steer angle sensors 52, 54.
[0088] At operation 920, a first clutch pack assembly associated
with an inner drive wheel located on a first side of a motorized
vehicle is engaged. The engagement force of the first clutch pack
assembly may be determined, in part, from the vehicle steering
request.
[0089] At operation 930, a first driving torque is applied to the
inner drive wheel.
[0090] At operation 940, the second clutch pack assembly associated
with an outer drive wheel located on a second side of the motorized
vehicle is engaged. The engagement force of the second clutch pack
assembly may also be determined, in part, from the vehicle steering
request.
[0091] At operation 950, a second driving torque is applied to the
outer drive wheel, wherein the second driving torque is different
than the first driving torque. In one embodiment, the second
driving torque applied to the outer drive wheel is greater than the
first driving torque applied to the inner drive wheel during a
first steering request associated with a vehicle turning radius.
Both the inner and outer drive wheels may be engaged in a forward
direction of vehicle travel when the first and second driving
torques are applied.
[0092] The first rotation force may be reduced to zero during a
second steering request associated with a smaller vehicle turning
radius than the first steering request. A reverse driving torque
may be applied to the inner drive wheel during a third steering
request associated with a smaller vehicle turning radius than the
second steering request. The engagement forces of the first and
second clutch pack assemblies may be independently determined, in
part, from the monitored rotational speeds of the inner and outer
drive wheels. The independent control of the torque and rotational
speed of the inner and outer drive wheels may be achieved without a
conventional differential.
[0093] FIG. 10 illustrates an example planetary and clutch pack
assembly associated with a drive wheel transmission system 100.
Only one of the clutch pack assemblies 125 is illustrated (e.g. the
right hand clutch pack assembly) for sake of clarity, whereas the
other clutch pack assembly is understood to operate similarly. The
wheel hubs and drive features may be symmetrical, and in the case
of loss of function on either side may provide redundancy.
[0094] A spirol bevel (or hypoid) 138 drives the left hand clutch
pack assembly and the right hand clutch pack assembly. The clutch
pack assembly 125 comprises forward clutch pack 127 and reverse
clutch pack 129. A solid hub 105 may be locked to both the left
hand and right hand clutch pack assemblies. The solid hub 105
transmits the drive torque. The solid hub 105 may be used in place
of a differential. A pack pressure manifold 110 communicates the
pressures to the forward clutch pack 127 and the reverse clutch
pack 129 through rotating seals.
[0095] Forward and reverse direction ring gears 115 for forward and
backward directions of travel are fixed to the axle 106. In one
embodiment, a reversing planetary 135 comprises six gears (planets)
that allow the axle 106 to be reversed. The forward planetary 140
may comprise three gears (planets) that allow the axle to drive 106
in the forward direction. A planet carrier 120 on each side of the
axle 106 transmits the torque from the planet gears. A sun gear
assembly 165 transmits the torque from the forward clutch pack 127
and the reverse clutch pack 129. The sun gear assembly 165 may
comprise both a forward sun gear and a reverse sun gear.
[0096] A wheel spindle 160 located on each side of the axle 106
supports the weight of the vehicle. The wheel mounts on the wheel
hub 130. The left and right axle shafts carry the torque from the
planet carrier 120 to the wheel hub 130. A park brake engine off
release mechanism 150 allows release of spring applied clutch packs
when the engine is off in order to permit towing. The wheel speed
sensor 155 senses direction and speed of the wheel. Left hand and
right hand wheel speed sensors 155 may be provided for the left
hand and right hand wheels, respectively. The forward drive clutch
pack 127 and the reverse drive clutch pack 129 may be independently
modulated for reversing, braking, traction-control, turning, park
braking, and hill holding. In some embodiments, one-way bearings
are not required, or may be eliminated.
[0097] The system and apparatus described above can use dedicated
processor systems, micro-controllers, programmable logic devices,
or microprocessors that perform some or all of the operations. Some
of the operations described above may be implemented in software
and other operations may be implemented in hardware. It is further
understood that computer-readable medium having instructions stored
thereon may be provided, wherein when the instructions are executed
by at least one device, they are operable to perform some or all of
the operations.
[0098] Where specific numbers are provided, they are given as
examples only and are not intended to limit the scope of the
claims. The relationship between inputs and outputs of the various
operations, computation, and methods described herein may be
established by algorithms or by look up tables contained in
processor memory.
[0099] For the sake of convenience, the operations are described as
various interconnected functional blocks or diagrams. This is not
necessary, however, and there may be cases where these functional
blocks or diagrams are equivalently aggregated into a single logic
device, program or operation with unclear boundaries.
[0100] Having described and illustrated the principles of the
invention in a preferred embodiment thereof, it should be apparent
that the invention may be modified in arrangement and detail
without departing from such principles. We claim all modifications
and variation coming within the spirit and scope of the following
claims.
* * * * *