U.S. patent number RE31,981 [Application Number 06/600,981] was granted by the patent office on 1985-09-10 for control system for split axle drive mechanism.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to Brook A. Lindbert.
United States Patent |
RE31,981 |
Lindbert |
September 10, 1985 |
Control system for split axle drive mechanism
Abstract
A part-time four-wheel drive vehicle has a transfer case and a
split axle drive mechanism for the selectively driving two vehicle
wheels. The slit axle drive mechanism has a clutch associated with
one of the differential side gears for preventing back drive to the
transfer case in the two-wheel drive mode. A control system for
operating the clutch responsive to the operational mode of the
transfer case comprises a vacuum motor and a solenoid operated
two-way valve energized by way of a switch in the transfer case.
The control system also includes a pneumatic time delay and a
vacuum check valve.
Inventors: |
Lindbert; Brook A. (Utica,
MI) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
26953186 |
Appl.
No.: |
06/600,981 |
Filed: |
April 16, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
268580 |
May 29, 1981 |
04407387 |
Oct 4, 1983 |
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Current U.S.
Class: |
180/247;
180/24.1 |
Current CPC
Class: |
B60K
23/08 (20130101); B60K 17/35 (20130101) |
Current International
Class: |
B60K
17/35 (20060101); B60K 23/08 (20060101); B60K
017/34 (); B60K 023/08 () |
Field of
Search: |
;180/247,249,24.1
;192/3.51,3.59,3.58,.096,.07,.075,.08 ;403/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0035324 |
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Sep 1981 |
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EP |
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2503097 |
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Aug 1975 |
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DE |
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2637635 |
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Feb 1978 |
|
DE |
|
48-8821 |
|
Mar 1973 |
|
JP |
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Other References
Design Engineering, New 4-Wheel Drive, vol. 52, No. 2, 2/1981, p.
16. .
AMC's State-of-the Art, Mechanics Illustrated, 1/1981, pp. 68, 69,
70 & 90..
|
Primary Examiner: Pekar; John A.
Attorney, Agent or Firm: Leahy; Charles E.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine, comprising:
a vacuum motor mechanically connected to the clutch so that the
clutch is biased toward disengagement when the vacuum motor is
vented and biased toward engagement when the vacuum motor is
evacuated,
conduit means connecting the vacuum motor to a vacuum source
provided by the internal combustion engine,
said conduit means including a two-way valve which has a first
operative position when the vacuum motor is connected to a vent and
a second operative position where the vacuum motor is connected to
the vacuum source for evacuating the vacuum motor,
means operatively connected to the transfer case positioning the
two-way valve in the second operative position when the transfer
case is in a four-wheel drive mode whereby the clutch is
automatically engaged when four-wheel drive is selected, and
said two-way valve being mechanically positioned in the fist
operative position when the transfer case is in the two-wheel drive
mode whereby the control system does not require any power for
operation in the two-wheel drive mode.
2. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine, comprising:
a vacuum motor operatively connected to the clutch so that the
clutch is biased toward disengagement when the vacuum motor is
vented and biased toward engagement when the vacuum motor is
evacuated,
conduit means connecting the vacuum motor to a vacuum source
provided by the internal combustion engine,
said conduit means including a two-way valve which has a first
operative position where the vacuum motor is vented and a second
operative position where the vacuum motor is evacuated by the
vacuum source,
means positioning the two-way valve in the second position when the
transfer case is in a four-wheel drive mode whereby the clutch is
automatically engaged when four-wheel drive is selected, and
time delay means in the conduit means for delaying clutch
engagement to a time after the transfer case is shifted to
four-wheel drive, so that the clutch parts are rotating in the same
direction and four-wheel drive can be selected while the vehicle is
in motion.
3. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine, comprising:
a vacuum motor mechanically connected to the clutch so that the
clutch is biased toward disengagement when the vacuum motor is
vented and biased toward engagement when the vacuum motor is
evacuated,
conduit means connecting the vacuum motor to the intake manifold of
the internal combustion engine for evacuating the vacuum motor,
said conduit means including a two-way valve which has a first
operative position where the vacuum motor is vented and a second
operative position where the vacuum motor is connected to the
vacuum source,
electric means operatively connected to the transfer case
positioning the two-way valve in the second operative position when
the transfer case is in a four-wheel drive mode whereby the clutch
is automatically engaged when four-wheel drive is selected, and
a vacuum check valve in the conduit means between the two-way valve
and the intake manifold for preventing bleed down of the evacuated
vacuum motor by the intake manifold.
4. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine, comprising:
a vacuum motor mechanically connected to the clutch so that the
clutch is biased toward disengagement when the vacuum motor is
vented and biased toward engagement when the vacuum motor is
evacuated,
conduit means connecting the vacuum motor to the intake manifold of
the internal combustion engine for evacuating the vacuum motor,
said conduit means including a two-way valve which has a first
operative position where the vacuum motor is vented and a second
operative position where the vacuum motor is connected to the
vacuum source,
spring means positioning the valve in the first operative
position,
electric means positioning the two-way valve in the second
operative position when the transfer case is in a four-wheel
.Iadd.drive .Iaddend.mode whereby the clutch is automatically
engaged when four-wheel drive is selected,
pneumatic time delay means in the conduit means between the vacuum
motor and the two-way valve for delaying the clutch engagement for
a predetermined mininum amount of time after the transfer case is
shifted to four-wheel drive so that the clutch parts are rotating
in the same direction when four-wheel drive is selected while the
vehicle is in motion, and
a vacuum check valve in the .[.condition.]. .Iadd.conduit
.Iaddend.means between the two-way valve and the intake manifold
for preventing bleed down of the evacuated vacuum motor by the
intake manifold.
5. In a part-time four-wheel drive vehicle having a source of
vacuum, a transfer case having a two-wheel drive operating mode and
a four wheel drive operating mode, and a split axle drive mechanism
having a single clutch moveable between disengaged and engaged
positions for the two-wheel drive and four-wheel drive operating
modes, respectively,
a control system for automatically operating the clutch responsive
to the operational mode of the transfer case, comprising:
a vacuum motor,
means operatively connecting the vacuum motor to the clutch for
biasing the clutch toward the engaged position when the vacuum
motor is evacuated, and biasing the clutch toward the disengaged
position when the vacuum motor is vented to atmosphere,
conduit means connected between the vacuum motor and the vacuum
source,
said conduit means including valve means moveable between first and
second positions for alternately connecting the conduit means to
atmosphere or to the vacuum source,
means normally locating the valve means in the first position to
connect the conduit means to atmosphere and maintain the clutch
disengaged,
signal means actuated by the transfer case when in the four-wheel
drive operating mode for indicating such mode to the vehicle
operator,
and means actuated by the transfer case concurrently with actuation
of the signal means for moving the valve means to the second
position to connect the vacuum motor to the vacuum source and
evacuate the vacuum motor to bias the clutch toward the engaged
position when the transfer case is in the four-wheel drive
operating mode,
and time delay means delaying evacuation of the vacuum motor by the
vacuum source to a time after the transfer case is in the
four-wheel drive operating mode so that the clutch parts are
rotating in the same direction and four-wheel drive can be selected
while the vehicle is in motion.
6. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine, comprising:
a vacuum motor operatively connected to the clutch so that the
clutch is biased toward disengagement when the vacuum motor is
vented and biased toward engagement when the vacuum motor is
evacuated,
conduit means connecting the vacuum motor to a vacuum source
provided by the internal combustion engine,
said conduit means including a two-way valve which has a first
operative position where the vacuum motor is vented and a second
operative position where the vacuum motor is evacuated by the
vacuum source,
means positioning the two-way valve in the second position when the
transfer case is in a four-wheel drive mode whereby the clutch is
automatically engaged when four-wheel drive is selected, and
time delay means for delaying clutch engagement to a time after the
transfer case is shifted to four-wheel drive, so that the clutch
parts are rotating in the same direction and four-wheel drive can
be selected while the vehicle is in motion.
7. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine, comprising:
a vacuum motor mechanically connected to the clutch so that
.[.that.]. clutch is biased toward disengagement when the vacuum
motor is vented and .[.baised.]. .Iadd.biased .Iaddend.toward
engagement when the vacuum motor is evacuated,
conduit means connecting the vacuum motor to the intake manifold of
the internal combustion engine for evacuating the vacuum motor,
said conduit means including a two-way valve which has a first
operative position where the vacuum motor is vented and a second
operative position where the vacuum motor is connected to the
vacuum source,
spring means positioning the valve in the first operative
position,
means positioning the two-way valve in the second operative
position when the transfer case is in a four-wheel drive mode
whereby the clutch is automatically engaged when four-wheel drive
is selected,
pneumatic time delay means for delaying the clutch engagement for a
predetermined minimum amount of time after the transfer case is
shifted to four-wheel drive so that the clutch parts are rotating
in the same direction when four-wheel drive is selected while the
vehicle is in motion, and
a vacuum check valve in the conduit means between the two-way valve
and the intake manifold for preventing bleed down of the evacuated
vacuum motor by the intake manifold.
8. In a part-time four-wheel drive vehicle having a source of
vacuum, a transfer case having a two-wheel drive operating mode and
a four-wheel drive operating mode, and a split axle drive mechanism
having a single clutch moveable between disengaged and engaged
positions for the two-wheel drive and four-wheel drive operating
modes, respectively,
a control system for automatically operating the clutch responsive
to the operational mode of the transfer case, comprising:
a vacuum motor;
means operatively connecting the vacuum motor to the clutch for
biasing the clutch toward the engaged position when the vacuum
motor is evacuated, and biasing the clutch toward the disengaged
position when the vacuum motor is vented to atmosphere,
conduit means connected between the vacuum motor and the vacuum
source,
said conduit means including valve means moveable between first and
second positions for alternately connecting the conduit means to
atmosphere or to the vacuum source,
means normally locating the valve means in the first position to
connect the conduit means to atmosphere and maintain the clutch
disengaged,
means actuated by the transfer case for moving the valve means to
the second position to connect the vacuum motor to the vacuum
source and evacuate the vacuum motor to bias the clutch toward the
engaged position when the transfer case is in the four-wheel drive
operating mode,
and time delay means delaying evacuation of the vacuum motor by the
vacuum source to a time after the transfer case is in the
four-wheel drive operating mode so that the clutch parts are
rotating in the same direction and four-wheel drive can be selected
while the vehicle is in motion. .Iadd.
9. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine comprising:
a motor operatively connected to the clutch so that the clutch is
biased toward disengagement when a first signal is communicated to
the motor and biased toward engagement when a second signal is
communicated to the motor,
control means having a first operative position where the first
signal is communicated to the motor and a second operative position
where the second signal is communicated to the motor,
means positioning the control means in the second operative
position when the transfer case is in a four-wheel drive mode
whereby the clutch is automatically engaged when four-wheel drive
is selected, and
time delay means for delaying clutch engagement to a time after the
transfer case is shifted to four-wheel drive, so that the clutch
parts are rotating in the same direction and four-wheel drive can
be selected while the vehicle is in motion. .Iaddend. .Iadd.
10. A control system for automatically operating the clutch in a
single clutch split axle drive mechanism responsive to an
operational mode of a transfer case, with which the split axle
drive mechanism is used in a part-time four-wheel drive vehicle
powered by an internal combustion engine comprising:
a fluid motor operatively connected to the clutch so that the
clutch is biased toward disengagement when a first pressure
condition is communicated to the fluid motor and biased toward
engagement when a second pressure condition is communicated to the
fluid motor,
conduit means connecting the fluid motor to a fluid pressure
source,
said conduit means including a valve which has a first operative
position where the first pressure condition is communicated to the
fluid motor and a second operative position where the second
pressure condition is communicated to the fluid motor,
means positioning the valve in the second operative position when
the transfer case is in a four-wheel drive mode whereby the clutch
is automatically engaged when four-wheel drive is selected, and
time delay means for delaying clutch engagement to a time after the
transfer case is shifted to four-wheel drive, so that the clutch
parts are rotating in the same direction and four-wheel drive can
be selected while the vehicle is in motion. .Iaddend. .Iadd.
11. A control system enabling selection of four-wheel drive during
two-wheel driven motion of a vehicle having a transfer case which
includes a clutch or the like actuable to drivingly connect engine
torque with a propeller shaft connected with the differential input
of a differentially split axle drive mechanism having a first
differential output drive coupled with a first wheel and a second
differential output disconnectably coupled to a second wheel by an
axle clutch enabling the two-wheel drive mode to include
disconnection of the axle clutch as well as deactuation of the
transfer case clutch so that the propeller shaft and differential
input remain at fuel and wear saving rest while the road driven
first wheel back drives the second differential output in
counterrotation relative to the second wheel, said control system
comprising:
motor means connected to the axle clutch to actuate the axle clutch
to connectably couple the second differential output and the second
wheel, and control means operably associated with the transfer case
and adapted to operate the motor means and effect axle clutch
engagement, said control means having associated time delay means
so that axle clutch engagement occurs subsequent to actuation of
the transfer case clutch or the like to provide engine driven
rotation of the then resting propeller shaft and the differential
input and provide reversal of the counterrotation of the second
differential output into same direction rotation with the second
wheel at a substantially synchronized rate therewith whereby
four-wheel drive can be selected while the vehicle is in two-wheel
drive motion. .Iaddend. .Iadd.
12. A control system enabling selection of four-wheel drive during
two-wheel driven motion of a vehicle having a transfer case which
includes a clutch or the like actuable to drivingly connect engine
torque with a propeller shaft connected with the differential input
of a differentially split axle drive mechanism having a first
differential output drive coupled with one wheel and a second
differential output disconnectably coupled to a second wheel by an
axle clutch enabling the two-wheel drive mode to include
disconnection of the axle clutch as well as deactuation of the
transfer case clutch so that the propeller shaft and differential
input remain at fuel and wear saving rest while the road driven
first wheel back drives the second differential output in
counterrotation relative to the second wheel, said control system
comprising:
motor means operatively connected to the axle clutch for engaging
the axle clutch;
motor control means adapted to operate the motor means to engage
the axle clutch in response to four-wheel drive selection and
attendant actuation of the transfer case clutch to thereby
connectably couple the second differential output with the second
wheel; and
means for delaying the axle clutch engagement for an amount of time
subsequent to transfer case clutch actuation to enable initiation
of engine driven rotation of the then resting propeller shaft and
differential input and concomitant reversal of the counterrotation
of the second differential output into rotation in the same
direction with the second wheel and at a substantially synchronized
rate therewith whereby the transfer case clutch and axle clutch can
be selected to their respective four-wheel drive operating modes
while the vehicle is in motion. .Iaddend. .Iadd.13. A control
system enabling selection of four-wheel drive during two-wheel
driven motion of a vehicle having a transfer case which includes a
clutch or the like actuable to drivingly connect engine torque with
a propeller shaft connected with the differential input of a
differentially split axle drive mechanism having a first
differential output coupled with one wheel and a second
differential output disconnectably coupled to a second wheel by an
axle clutch enabling the two-wheel drive mode to include
disconnection of the axle clutch as well as deactuation of the
transfer case clutch so that the propeller shaft and differential
input remain at fuel and wear saving rest while the road driven
first wheel back drives the second differential output in
counterrotation relative to the second wheel, said control system
comprising:
a fluid motor operatively connected to the axle clutch so that the
axle clutch is disengaged in response to a first fluid pressure
condition and engaged in response to a second fluid pressure
condition;
valve means having a first operative position to communicate the
first fluid pressure condition to the fluid motor and a second
operative position for communicating the second fluid pressure
condition to the fluid motor;
means positioning the valve means in the second operative position
when the transfer case clutch is engaged whereby the axle clutch is
automatically engaged in response to engagement of the transfer
case clutch and attendant engine driven rotation of the propeller
shaft and differential input; and
means for delaying axle clutch engagement to a time after the
transfer case clutch is engaged to assure reversal of the
counterrotation of the second differential output and rotation of
the second differential output at a substantially synchronized rate
with the second wheel whereby the axle clutch can be engaged while
the vehicle is in motion. .Iaddend.
Description
This invention relates to a split axle drive mechanism and, more
particularly, to a control system for operating the clutch of a
split axle drive mechanism which is used in a part-time four-wheel
drive vehicle.
A common drive configuration for a part-time four-wheel drive
vehicle comprises a transfer case having an input shaft driven by
the vehicle transmission and two output shafts. One output shaft is
drive connected to the input shaft for continuously driving one set
of vehicle wheels, usually the rear wheels, through a propeller
shaft, differential and split axle. The second output shaft is
connectable to the input shaft by a clutch or the like in the
transfer case for selectively driving the other set of vehicle
wheels, usually the front wheels, through a second propeller shaft,
a differential and split axle. Two-wheel drive is provided when the
clutch in the transfer case is disengaged and four-wheel drive when
the clutch is engaged.
A long standing problem associated with part-time four-wheel drive
configurations of the above-noted type is wear and power
consumption in the two-wheel drive mode. This is caused by the
non-driven front wheels back driving the drive line components
between the non-driven wheels and the clutch or comparable
mechanism in the transfer case which disconnects the second or
auxiliary output shaft from the transfer case input shaft.
A known solution to reducing wear and power consumption is the use
of a single clutch in the axle assembly for the selectively driven
wheels which disconnects one of the selectively driven wheels from
its associated side gear in the differential when the vehicle is in
the two-wheel drive mode. See U.S. patent application Ser. No.
126,561, for a Split Axle Drive Mechanism filed by Laszlo Nagy on
Mar. 3, 1980, now U.S. Pat. No. 4,341,281.
The object of this invention is to provide a control system for
automatically operating the clutch in the split drive mechanism
responsive to the operational mode of the transfer case in a
part-time four-wheel drive vehicle.
Another object of this invention is to provide a control system
which uses components already on the vehicle as much as possible
and thereby minimizing the number of additional components required
by the system.
A feature of the invention is that the control system does not
require any power to disengage the clutch and, consequently, the
control system contributes to fuel economy in the two-wheel drive
mode.
Another feature of the invention is that the control system
incorporates a time delay between the shift to four-wheel drive in
the transfer case and the application of clutch engage forces in
the split axle drive mechanism so that four-wheel drive can be
selected while the vehicle is in motion.
Yet another feature of the invention is that the control system
uses a vacuum motor for engaging and disengaging the clutch and,
consequently, the clutch fork can be operated directly by the
vacuum motor without the necessity of a complicated shifter
mechanism as in the aforesaid patent application.
Still yet another feature of the invention is that the control
system includes a vacuum check valve so that the system can operate
off of the engine intake manifold.
Still yet another feature of the invention is that the control
system is electrically activated and deactivated by a pre-existing
switch associated with the transfer case.
Still yet another feature of the invention is that abusive clutch
engagement, such as at full throttle, is not possible when the
engine is the vacuum source because the available vacuum is not
sufficient to actuate the control system.
Still yet another feature of the invention is that the control
system uses the engine intake manifold as a vacuum source and a
pre-existing switch associated with the transfer case thereby
minimizing the number of additional components required by the
system.
Other objects and features of the invention will become apparent to
those skilled in the art as the disclosure is made in the following
detailed description of a preferred embodiment of the invention as
illustrated in the accompanying sheets of drawing in which:
FIG. 1 is a schematic plan view of a part-time four-wheel drive
vehicle having a split axle drive mechanism and a control system
for operating the clutch thereof in accordance with my
invention.
FIG. 2 is a partially sectioned plan view of the split axle drive
mechanism shown in FIG. 1.
FIG. 3 is a schematic view showing details of the control system
and its relationship to other vehicle components.
Referring now to the drawing and particularly to FIG. 1, there is
shown a schematic plan view of a part-time four-wheel drive
vehicle, comprising an internal combustion engine 10, transmission
12 and transfer case 14 mounted on a vehicle chassis (not shown).
The engine 10 and transmission 12 are well-known components as is
the transfer case 14 which typically has an input shaft (not
shown), a main output shaft 16 and an auxiliary output shaft 18.
The main output shaft 16 is drive connected to the input shaft in
the transfer case 14 and is customarily aligned with it. The
auxiliary output shaft 18 is drive connectable to the input shaft
by a clutch or the like in the transfer case 14 and customarily
offset from it. The transfer case clutch is actuated by a suitable
selector mechanism (not shown) which is generally remotely
controlled by the vehicle driver.
The main output shaft 16 is drivingly connected to a rear propeller
shaft 20 which in turn is drivingly connected to a rear
differential 22. The rear differential 22 drives the rear wheels 24
through split axle parts in a well-known manner.
The auxiliary output shaft 18 is drivingly connected to a front
propeller shaft 26 which in turn is drivingly connected to a split
axle drive mechanism 28 for selectively driving the front wheels 30
through split axle parts.
The Split Axle Drive Mechanism
As shown in FIGS. 2 and 3, the split axle drive mechanism 28
includes an automotive type differential 32 inside a housing 34.
The differential 32 has a drive shaft 36 and a differential case 38
rotatably mounted in the housing 34 on orthogonally relaxed axes.
The drive shaft 36 is the differential input and has an external
yoke 40 at one end for universally coupling the drive shaft 36 to
the front propeller shaft 26. The internal end of the drive shaft
36 has an integral driving pinion 42 which meshes with a ring gear
44 attached to the differential case 38. The differential case 38
carries a plurality of rotatable pinion gears 46 mounted on a cross
pin 48. The pinion gears 46 mesh with side gears 50 and 52 which
are splined to the end of the stub shafts 54 and 56 respectively.
The stub shafts 54 and 56 are rotatably mounted in the housing 34
on the differential case axis. These stub shafts are rotatable
relative to each other and to the differential case. The
differential 32 as thus far described and its mode of operation are
well-known.
The split drive axle mechanism 28 further includes a positive
clutch 58 which changes the mode of operation of the differential
32 and makes it particularly useful for the selectively driven
wheels in a part-time four-wheel drive vehicle. As shown in FIG. 3,
the clutch 58 comprises an integral spline wheel 60 at the outer
end of the stub shaft 54 and a matching spline wheel 62 attached to
the inner end of an extension shaft 64. The extension shaft 64 has
its inner end journalled in the hollow outer end of the stub shaft
54 and its outer end journalled in a bearing (not shown) at the
remote end of an extension tube 66 attached to the housing 34.
The clutch 58 further includes an internally splined sleeve 68
which is slidably mounted on the spline wheel 60. The splined
sleeve 68 is shiftable between a disengaged position (shown in
solid lines in FIGS. 2 and 3) and an engaged position (shown in
phantom lines in FIG. 3) where it couples the spline wheels 60 and
62.
The split axle drive mechanism 42 is attached to the vehicle
chassis by means of a housing bracket (not shown) and a bracket 70
on the extension tube 66.
The split axle drive mechanism 28 has two outputs for the
respective split axle parts associated with the respective front
wheels 30. One output is the stub shaft 54, clutch 58 and extension
shaft 64 which has an external flange 72 for attaching one of the
split axle parts. The other output is the stub shaft 56 which has
an external flange 74 for attaching the other split axle part.
Suitable split axle parts, commonly referred to as half shafts, are
well-known from front wheel drive automobiles. These may be used
for connecting the split axle drive mechanism 28 to the front
wheels 30. The drawings schematically illustrate a common type of
half shaft for driving connection to independently suspended
steerable vehicle wheels comprising an axle shaft 76 having a
plunging universal joint 78 at its inboard end adapted for
connection to an output such as the flange 72 or 74 and the
well-known Rzeppa-type universal joint 80 at its outboard end
adapted to be connected to the vehicle wheel 30.
The split axle drive mechanism 28 also includes a shifter 81 for
operating the clutch 58. The shifter 81 as shown in FIG. 3
comprises a fork 82 having its tines engaged in an external groove
of the sleeve 68 and its base slidably mounted on a slide 84. The
fork 82 is positioned on the slide 84 by opposed coil springs 86
and 88. The slide 84 itself is translated by a push-pull cable 90.
FIG. 3 shows the fork 82 and the slide 84 in the clutch disengaged
position in solid lines. The clutch 58 is engaged by moving the
slide 84 to the left from the solid line position shown in FIG. 3.
This loads the spring 88 which in turn biases the fork 82 and
sleeve 68 toward the left. The sleeve 68 then slides into
engagement with the spline wheel 62 under the action of spring 88
when their respective splines align in a complementary manner. The
clutch 58 is disengaged by returning the slide 84 to the position
shown in FIG. 3. This loads the spring 86 which in turn returns the
slide 84 and fork 82 to the clutch disengaged position when the
biasing force of spring 86 is sufficient to overcome the torque
load on the engaged splines of spline wheel 62 and sleeve 68.
The Control System
A control system for operating the clutch 58 via the push-pull
cable 90 and shifter 81 is shown in the lower portion of FIG.
3.
The control system comprises a vacuum motor 92, a solenoid operated
two-way slide valve 94, a vacuum check valve 96, three rubber
conduits or hoses 98, 100 and 102 and an orifice device 103.
The vacuum motor 92 comprises a hard plastic cup shaped shell 104
and a flexible cup shaped diaphragm 106 attached together
rim-to-rim to form a collapsible chamber 108. The bottom wall of
the diaphragm 106 is reinforced by plates 110 and 112 which are on
opposite sides of the bottom wall and riveted together. The
diaphragm 106 is normally extended as shown in FIG. 3 and biased
into the extended position by a coil spring 114 inside the chamber
108. The hard plastic shell 104 has a nipple 116 which forms a port
117 for evacuating or venting the chamber 108.
The push-pull cable 90 which operates the shifter 81 for the clutch
58 is attached to an eyelet of the outer plate 112 as shown in FIG.
3 so that the clutch 58 is disengaged when the chamber 108 is
vented to atmosphere and the diaphragm 106 of the vacuum motor 92
is extended.
The vacuum motor 92 is mounted on a U-shaped bracket 118 which in
turn is fixedly mounted in the engine compartment of the vehicle,
such as by fastening the bracket 118 to a body panel as
schematically represented in FIG. 1.
The two-way slide valve 94 can also be conveniently mounted on the
bracket 118 as shown in FIG. 1. However, the slide valve 94 is
shown in a detached position in FIG. 3 for clarity.
The two-way slide valve 94 comprises a sheet metal cup 119 with a
plastic spool secured in it to provide a cylindrical valve chamber
120. The valve chamber 120 has coaxial ports 122,124 at opposite
ends and a radial port 126. Ports 122 and 124 are vent and vacuum
ports, respectively. The orifice device 103 is a bias cup having a
small hole through its bottom wall. The cup is mounted in the outer
end of the radial port 126 and the radial port 126 is connected to
the vacuum motor 92 by the rubber hose 98.
A slide member 128 is disposed in the valve chamber 120. The slide
member 128 has stems 130,132 at its opposite ends which cooperate
with the respective vent and vacuum ports 122 and 124. The slide
member 128 is biased by a coil spring 134 to an extended position
where the stem 132 closes the vacuum port 124 as shown in FIG. 3.
Consequently, the vacuum motor 92 is normally vented via the open
vent port 122.
The valve chamber 120 is surrounded by a solenoid coil 136 which,
when energized, retracts the slide member 128 so that the stem 130
closes the vent port 122 and the vacuum port 124 is opened. The
enlarged center section 129 of the slide member 128 is a cylinder
with four equally spaced flats 131. The cylinder pilots the slide
member 128 in the valve chamber 120 while the flats 131 permit flow
from one end of the valve chamber 120 to the other, particularly in
the vent mode illustrated in FIG. 3 where air flows from the vent
port 122 to the vacuum motor 92 via the radial port 126.
The vacuum port 124 is connected to the vacuum check valve 96 by
the rubber hose 100. The vacuum check valve 96 comprises a plastic
housing 137 having a nipple at each end which form respective
suction and discharge ports 138,139 for a valve chamber 140. The
suction port 138 is connected to the vacuum port 124 of the slide
valve 94 by the hose 100 as indicated above. The discharge port 139
is connected by hose 102 to a vacuum source, such as the intake
manifold of the internal combustion engine 10.
The valve chamber 137 has an internal apertured wall 141 which
supports a coil spring 143 and a flat plug 142 which is biased by
the coil spring to block the suction port 138. The vacuum check
valve 96 permits air flow from the slide valve 94 to the vacuum
source that is, in the direction of the arrow 144 shown in FIG. 3
but prevents air flow from the vacuum source to the slide valve 94.
The vacuum check valve 96 prevents the engine from bleeding down
the vacuum motor 92 when the chamber 108 is evacuated.
The solenoid operated two-way slide valve 94 has a plastic socket
146 at the end which has the vent port 122. The socket 146 houses a
pair of male blade terminals 148,150 attached to the respective
ends of the solenoid coil 136. The socket 146 also houses a filter
152 for the vent port 122.
The electric circuit for energizing the solenoid coil 136 is shown
schematically in FIG. 3. By way of background, transfer cases for
part-time four-wheel drive vehicles commonly include an electric
switch which is closed when the transfer case is in the four-wheel
drive mode. The closed switch completes a circuit to an indicator
light on the vehicle instrument panel to advise the vehicle driver
that the vehicle is in the four-wheel drive mode. See for instance,
U.S. Pat. No. 3,283,298 issued to Edgar F. Kaiser on Nov. 1,
1966.
FIG. 3 schematically illustrates a transfer case 14 having a switch
154, it being understood that the switch 154 is operatively
connected with the transfer case 14 so that the switch 154 opens
when the transfer case 14 is in the two-wheel drive mode and closes
when the transfer case 14 is in the four-wheel drive mode.
The switch 154 is electrically connected in series with the vehicle
battery 156 and two branch circuits--one having an indicator light
158 and the other having the solenoid coil 136. Consequently, the
solenoid coil 136 is also energized when the indicator light 158 is
lit responsive to the transfer case 14 being in the four-wheel
drive mode.
Operation
The two-wheel drive mode is illustrated in FIGS. 2 and 3. In this
mode, the drive to the auxiliary output shaft 18 is disconnected in
the transfer case and, consequently, the switch 154 is open. The
slide member 128 is extended under the action of spring 134, in a
position blocking the vacuum port 124, and opening the vent port
122. The clutch 58 is disengaged and held in the disengaged
position by the coil spring 114 in the vacuum motor 92 acting on
the shifter 81 via the push-pull cable 90.
When the vehicle is driven in the two-wheel drive mode, the lower
wheel 30 shown in FIG. 1 back drives the differential side gear 52
but the upper wheel 30 does not back drive the differential side
gear 50 because the clutch 58 is disengaged. Since the side gear 50
does not have any load, the side gear 52 merely counter-rotates the
side gear 50 through the pinion gears 46. Hence, there is no back
drive to the differential case 38, drive shaft 36 (differential
input), front propeller shaft 36, auxiliary output shaft 18 and
other transfer case components connected to the auxiliary output
shaft 18 ahead of the disconnect in the transfer case 14. This mode
of operation eliminates the major portion of wear and power
consumption which would result from back drive of both wheels
30.
It should also be noted that the control system does not require
any power for operation in the two-wheel drive mode since the
vacuum motor 92 is vented and the solenoid operated two-way slide
valve 94 is deenergized. Consequently, the control system itself
enhances fuel economy in the two-wheel drive mode.
When the four-wheel drive mode is selected by the vehicle operator,
the auxiliary output shaft 18 is drive connected to the input shaft
in the transfer case 14 and the switch 154 is closed, setting off
two chains of events which result in the clutch 58 automatically
being engaged.
The transfer case output shaft 18 now drives the drive shaft 36
(differential input) and the differential case 38. The driven or
rotating differential case 38 in turn reverses the counter-rotating
side gear 50 so that the side gear 50 and stub shaft 54 rotate in
the same direction as the side gear 52 and the extension shaft 64
which are driven by the respective front vehicle wheels 30. In
time, the driven differential case 38 tends to synchronize the
speeds of the stub shaft 54 and the extension shaft 64.
In the meantime, the closed switch 154 energizes the solenoid coil
136 of the two-way slide valve 94 retracting the slide member 128.
The retracted slide member 128 closes the vent port 122 and opens
the vacuum port 124 which connects the chamber 108 of vacuum motor
92 to the vacuum source provided by the internal combustion engine
10 through hose 102, vacuum check valve 96, hose 100, vacuum port
124, radial port 126, orifice device 103, rubber hose 98 and port
117.
The vacuum chamber 108 is then evacuated, producing a clutch engage
force which collapses the diaphragm 106 against the action of
spring 114 and pulls the slide 84 to the left from the solid line
position shown in FIG. 3 via the cable 90. Movement of the slide 84
loads the coil spring 88 which biases the shifter fork 82 and
sleeve 68 toward the clutch engage position. The sleeve 68 then
slides into engagement with the spline wheel 62 under the action of
spring 88 when their respective splines align in a complementary
manner. When the clutch 58 is engaged, as shown in phantom in FIG.
3, both front wheels 30 are driven and the split axle drive
mechanism 28 acts as a conventional differential.
The orifice device 103 provides a time delay of approximately two
to three seconds between the time that the switch 154 is closed and
the vacuum chamber 108 is evacuated. This time delay is provided so
that rotation of the counter-rotating side gear 50 is reversed and
the sleeve 68 is rotating in the same direction as the spline wheel
62 before any substantial clutch engage force is produced by the
vacuum motor 92. This time delay feature permits the vehicle
operator to shift the transfer case 14 from two-wheel drive to
four-wheel drive while the vehicle is in motion.
Another feature which should be noted is the vacuum check valve 96
which keeps the chamber 108 evacuated once it is evacuated by the
engine intake manifold. This feature prevents the evacuated chamber
108 from being bled down by a low vacuum in the engine intake
manifold such as in a steep, four-wheel drive, hillclimb.
The clutch 58 is also automatically disengaged when the vehicle is
returned to the two-wheel drive. When the two-wheel drive mode is
selected at the transfer case 14, the switch 154 opens deenergizing
the solenoid coil 136. The slide member 128 is then biased by
spring 134 to the position shown in FIG. 3 where the vacuum port
124 is closed and the vent port 122 is opened. The chamber 108 is
now vented and the diaphragm 106 extends, aided by the coil spring
114. This in turn pushes the slide 84 via the push-pull cable 90 to
the clutch disengaged position shown in FIG. 3 which loads the coil
spring 86. The coil spring 86 then biases the fork 82 and sleeve 68
toward the solid line position shown in FIG. 3. The clutch 58 then
automatically disengages when the force of spring 86 is sufficient
to overcome the torque loading between the spline wheel 62 and the
sleeve 68 which usually occurs with a slight deceleration of the
vehicle. When the clutch 58 is disengaged, there is no back drive
to the differential case 38 as indicated earlier.
It should be noted that shifter 81 provides a redundancy when used
in conjunction with the control system illustrated in FIG. 3. The
coil springs 86 and 88 bias the sleeve 68 toward the disengaged and
engaged position, respectively, so that the clutch 58 is not
engaged and disengaged with excessive force which could happen if
the shift fork 82 was operated by a solid mechanical linkage.
Since the vacuum motor 92 itself provides controlled clutch
engagement and disengagement forces, it is possible to simplify the
shifter 81 by eliminating the springs 86 and 88 and fixing the
shift fork 82 on the slide 84 so that the push-pull cable 90 moves
the shift fork 82 directly.
It wish it to be understood that I do not desire to be limited to
the exact details of construction shown and described, for obvious
modifications will occur to a person skilled in the art.
* * * * *