U.S. patent application number 12/407277 was filed with the patent office on 2009-09-24 for transfer case arrangement.
This patent application is currently assigned to MAGNA Powertrain AG & Co KG. Invention is credited to Walter Hamal, Johannes Quehenberger.
Application Number | 20090235781 12/407277 |
Document ID | / |
Family ID | 40984031 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090235781 |
Kind Code |
A1 |
Quehenberger; Johannes ; et
al. |
September 24, 2009 |
TRANSFER CASE ARRANGEMENT
Abstract
The invention relates to a transfer case arrangement comprising
a first output shaft, a second output shaft, a clutch for the
distribution of a torque between the output shafts, a shutdown
device for the shutting down of the second output shaft when the
clutch is disengaged and a lubrication device for the lubrication
of the clutch and/or of another component of the transfer case
arrangement.
Inventors: |
Quehenberger; Johannes;
(Saalbach, AT) ; Hamal; Walter; (Stallhof,
AT) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
MAGNA Powertrain AG & Co
KG
Lannach
AT
|
Family ID: |
40984031 |
Appl. No.: |
12/407277 |
Filed: |
March 19, 2009 |
Current U.S.
Class: |
74/665F ;
192/113.3 |
Current CPC
Class: |
B60K 17/3515 20130101;
F16H 57/0441 20130101; B60K 23/0808 20130101; Y10T 74/19074
20150115; B60K 23/08 20130101; Y10T 477/613 20150115; F16H 57/0483
20130101; B60K 17/342 20130101; B60K 17/02 20130101; F16H 57/0435
20130101 |
Class at
Publication: |
74/665.F ;
192/113.3 |
International
Class: |
B60K 23/08 20060101
B60K023/08; F16D 13/74 20060101 F16D013/74 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 2008 |
DE |
10 2008 015 200.5 |
Claims
1. A transfer case arrangement comprising a first output shaft; a
second output shaft; a clutch for distributing a torque between the
output shafts; a shutdown device for shutting down the second
output shaft when the clutch is disengaged; a lubrication device
for lubricating the clutch and/or another component of the transfer
case arrangement, the lubrication device having an oil conveying
device for conveying lubrication oil; and a control that activates
the oil conveying device periodically when the second output shafts
shut down.
2. The transfer case arrangement in accordance with claim 1,
wherein the control activates the oil conveying device
intermittently when the second output shaft is shut down.
3. The transfer case arrangement in accordance with claim 1,
wherein the oil conveying device includes an electrically driven
pump or a pump driven by the second output shaft.
4. The transfer case arrangement in accordance with claim 1,
wherein the oil conveying device is formed by a chain drive or by a
gear connection connected between an output of the clutch and the
second output shaft.
5. The transfer case arrangement in accordance with claim 1,
wherein activation of the oil conveying device takes place by an at
least partial engagement of the clutch.
6. The transfer case arrangement in accordance with claim 1,
wherein the oil conveying device conveys the lubrication oil from
an oil sump of the transfer case into a region of the transfer case
disposed above the clutch or above the another component.
7. The transfer case arrangement in accordance with claim 1,
wherein the lubrication device includes an oil reservoir for
collecting the lubrication oil conveyed by the oil conveying device
such that an oil level in the oil reservoir is above an outlet
opening of a supply line leading from the oil reservoir to the
clutch or to the another component.
8. The transfer case arrangement in accordance with claim 1,
wherein the second output shaft transmits of torque to wheels of a
motor vehicle and the shutdown device is connected between the
wheels and the second output shaft.
9. The transfer case arrangement in accordance with claim 1,
wherein the shutdown device is arranged at the hubs of the
wheels.
10. The transfer case arrangement in accordance with claim 1,
wherein the shutdown device is arranged at an output of an axial
differential of a vehicle axle driving the wheels.
11. The transfer case arrangement in accordance with claim 1,
wherein the control activates the oil conveying device during a
deceleration or a coasting mode of a motor vehicle in which the
transfer case arrangement is arranged.
12. A method for lubricating a clutch and/or another component of a
transfer case arrangement that includes a first output shaft and a
second output shaft, the clutch distributing a torque between the
output shafts the method comprising: shutting down the second
output shaft with a shutdown device when the clutch is disengaged;
and lubricating the clutch and/or the another component of the
transfer case arrangement with a lubrication device having an oil
conveying device for conveying lubrication oil, the oil conveying
device being activated periodically when the second output shaft is
shut down.
13. The method in accordance with claim 12, wherein the oil
conveying device is activated by an at least partial engagement of
the clutch.
14. The method in accordance with claim 12, wherein the oil
conveying device is activated during a deceleration or a coasting
mode of a vehicle in which the transfer case arrangement is
arranged.
Description
[0001] The invention relates to a transfer case arrangement having
a first output shaft, a second output shaft, a clutch for the
distribution of a torque between the output shafts and a shutdown
device for the shutting down of the second output shaft with a
disengaged clutch.
[0002] Such a transfer case arrangement is generally known and is
used, for example in a motor vehicle, to permanently drive a
vehicle axle, e.g. a rear axle, connected to the first output shaft
and to additionally transmit, when required, drive torque via the
second output shaft to a second vehicle axle, e.g. a front axle.
The first vehicle axle permanently driven by the first output shaft
is also called the primary axle, whereas the optionally drivable
second vehicle axis is called a secondary axle.
[0003] The transmission of drive torque via the second output shaft
to the secondary axle takes place by an at least partial engagement
of the clutch of the transfer case. When the clutch is disengaged,
the second output shaft, and consequently also the secondary axle,
is, in contrast, not loaded with drive torque. To prevent
unnecessary moments of inertia and drag losses from being generated
in that the second output shaft is set into rotation by vehicle
wheels connected to the secondary axle with a disengaged clutch, it
is known to provide a shutdown device by which the second output
shaft can be shut down when the clutch is disengaged in that it is
decoupled from the vehicle wheels.
[0004] Known transfer cases typically--independently of whether
they have a shutdown device for the shutting down of the second
output shaft or not--have a lubrication device for the lubrication
of the clutch and/or of another component, e.g. of a bearing, of
the transfer case, said lubrication device having a pump for the
conveying of lubrication oil from an oil sump of the transfer case
to the clutch and/or to the other component.
[0005] Conventionally, the pump is an electrically driven pump or a
pump driven by the first output shaft, for example a gerotor pump
which continuously conveys lubrication oil.
[0006] Such pumps result in a deterioration of the efficiency of
the transfer case so that pump-less lubrication devices have been
developed which convey lubrication oil from the transmission sump
to the clutch and/or bearings of the transfer case while utilizing
a chain drive or a gear connection between the output of the clutch
and the second output shaft.
[0007] If such pump-less lubrication devices are provided in a
transfer case arrangement with a shutdown device, the problem,
however, occurs that no lubrication oil conveying takes place when
the second output shaft is shut down. This impairs the lubrication
of the clutch and/or of the bearings of the transfer case and can
result in damage to the transfer case at least in the long
term.
[0008] It is the underlying object of the invention to provide a
transfer case arrangement of the initially named kind whose
reliable function is permanently ensured.
[0009] A transfer case arrangement having the features of claim 1
is provided to satisfy the object.
[0010] The transfer case arrangement in accordance with the
invention includes a first output shaft, a second output shaft, a
clutch for the distribution of a torque between the output shafts,
a shutdown device for the shutting down of the second output shaft
when the clutch is disengaged and a lubrication device for the
lubrication of the clutch and/or of another component, e.g. of a
bearing, of the transfer case arrangement, with the lubrication
device having an oil conveying device or the conveying of
lubrication oil. A control is furthermore provided which serves to
activate the oil conveying device from time to time when the second
output shaft is shut down.
[0011] Since the control provided in accordance with the invention
provides an activation of the oil conveying device from time to
time when the second output shaft is shut down, it is ensured that
a quantity of lubrication oil is conveyed which is sufficient for
an ideal lubrication of the clutch and/or of the other transmission
component even with a shut down second output shaft, for example
with a vehicle drive only via the primary axle. Since an oil
conveying is typically anyway provided with a driven second drive
shaft, a sufficient lubrication of the clutch or of the other
transmission component is therefore always ensured and a
prerequisite for a long-term reliable function of the transfer case
is thus provided.
[0012] Since the control provided in accordance with the invention
does not provide a continuous oil conveying with a shut down second
output shaft, but only an activation of the oil conveying device
from time to time, churning losses accompanying the oil conveying
as well as unwanted moments of inertia, which can occur, for
example, when the oil conveying is based on a rotation of the
second output shaft, are furthermore minimized, which ultimately
contributes to a better efficiency of the transfer case
arrangement.
[0013] Advantageous embodiments of the invention can be seen from
the dependent claims, from the description and from the
drawing.
[0014] In accordance with a first embodiment, the control serves to
activate the oil device intermittently, i.e. to repeatedly switch
the oil conveying device on and off, with a shut down second output
shaft. In this respect, the switching on and off of the oil
conveying device can take place at regular or irregular time
intervals with the activation or deactivation of the oil conveying
device being able to follow a fixedly preset pattern or being able
to be carried out in a demand-oriented manner.
[0015] The oil conveying device can in particular be activated on a
braking of the vehicle, e.g. by an engine brake or by a foot brake,
since losses accompanying the actuation of the oil conveying
device, for example drag losses and/or moments of inertia, do not
have a disadvantageous effect, but rather an advantageous one. In
addition, the actuation of the oil conveying device contributes to
the heating of the transfer case and/or of an axial differential of
the secondary axle, which has an advantageous effect on the
efficiency of the transmissions.
[0016] The oil conveying device can include an electrically driven
pump or a pump driven by the second output shaft, e.g. a gerotor
pump. Alternatively, the oil conveying device can be formed by a
chain drive or by a gear connection which is connected between an
output of the clutch and the second output shaft.
[0017] In the case of an electrically driven pump, the activation
of the oil conveying device can take place by an activation signal
of the control output to the pump directly.
[0018] If, in contrast, the oil conveying device is formed by a
pump driven by the second output shaft or by a chain drive or a
gear connection, the activation of the oil conveying device
preferably takes place by an at least partial engagement of the
clutch. Some of the drive torque is branched off from the first
output shaft to the second output shaft by the at least partial
engagement of the clutch, whereby the second output shaft is set
into rotation and the oil conveying device is set into motion. The
second output shaft shut down per se is in other words therefore
temporarily set into rotation for the oil conveying.
[0019] In particular in the case that the oil conveying device is
formed by a pump driven by the second output shaft or by a chain
drive or a gear connection, it proves to be particularly
advantageous if the control is made to activate the oil conveying
device during a deceleration or a coasting mode of a motor vehicle
in which the transfer case arrangement is arranged since the
acceleration of the previously shut down second output shaft can be
carried out with particular fuel economy in this manner and
ultimately better fuel efficiency is achieved.
[0020] The oil conveying device is preferably made so that it
conveys the lubrication oil from an oil sump of the transfer case
into a region of the transfer case disposed above the clutch or
above the other component.
[0021] Furthermore, the lubrication device can include an oil
reservoir for the collection of lubrication oil conveyed by the oil
conveying device, in particular such that an oil level in the oil
reservoir is above an outlet opening of a supply line leading from
the oil reservoir to the clutch or to the other component. Such an
oil reservoir so-to-say acts as a buffer or intermediate store
which ensures that sufficient lubrication oil is also available for
the lubrication of the clutch or of the other transmission
component between two oil conveying procedures. The position of the
oil level in the oil reservoir above the outlet opening of the
supply line makes it possible that the oil can only flow out of the
oil reservoir to the clutch or to the other transmission component
due to gravity, i.e. without any additional pumping effect.
[0022] The length of an oil conveying procedure and the time
interval between two sequential oil conveying procedures are
preferably matched to the oil reservoir and/or to the supply line
such that an oil level sufficiently high for a reliable lubrication
is always ensured in the oil reservoir. Alternatively or
additionally, the oil reservoir can have an oil level sensor which
detects the level of the oil in the oil reservoir and transmits a
corresponding signal to the control when the oil level falls below
a critical lower limit and an activation of the oil conveying
device is required.
[0023] In accordance with a further embodiment, the second output
shaft serves for the transmission of drive torque to wheels of a
motor vehicle and the shutdown device is connected between the
wheels and the second output shaft. The second output shaft can
therefore be decoupled from the wheels by the shutdown device to
prevent the second output shaft from being set into rotation by the
wheels with a disengaged clutch of the transfer case.
[0024] The shutdown device can in this respect be arranged directly
at the hubs of the wheels. This has the advantage that not only the
second output shaft, but rather also the vehicle axle connected
thereto and driving the wheels, i.e. the secondary axle, can be
decoupled with respect to a rotation of the wheels. The shutdown
device therefore thus effects a shutdown not only of the second
output shaft, but also of the secondary axle. With a shutdown
device arranged at the hubs of the wheels, it can be a question of
dog clutches which can e.g. be actuated by negative pressure, for
example from a vacuum pump for a brake power assist unit or from an
intake restriction of the throttle, or also
electromagnetically.
[0025] Alternatively, the shutdown device can be arranged at an
axial differential, in particular at an output or at both outputs
of the axial differential, of a vehicle axle driving the wheels, in
other words that is of the secondary axle. In this case, the
shutdown device is therefore connected between the secondary axle
and the second output shaft so that only the second output shaft
can be shut down, whereas the secondary axle is set into rotation
by the wheels with a moving vehicle. A shutdown device of this kind
can, for example, be a friction clutch actuated by an electric
motor or one or two dog clutch(es).
[0026] A further subject of the invention is also a method for the
lubrication of a clutch and/or of another component of a transfer
case arrangement having the features of claim 11. The aforesaid
advantages can be achieved accordingly by the method in accordance
with the invention. Advantageous embodiments of the method result
from the embodiments of the transfer case arrangement in accordance
with the invention described above.
[0027] The invention will be described in the following purely by
way of example with reference to an advantageous embodiment and to
the enclosed drawing.
[0028] FIG. 1 shows a schematic representation of a transfer case
arrangement in accordance with the invention.
[0029] A transfer case arrangement of a motor vehicle which has an
engine 10 and a transfer case 12 is shown in FIG. 1. The transfer
case 12 includes a drive shaft 14 which is driven by the engine 10
and which is rigidly connected to a first output shaft 16 of the
transfer case 12. The combination of drive shaft 14 and first
output shaft 16 is also called a main shaft. The transfer case 12
can furthermore optionally have a step-down transmission (not
shown) arranged at the first drive shaft 14 for the switching in of
an off-road gear (hi/lo gear).
[0030] The first output shaft 16 is connected via an axial
differential 18 to a first vehicle axle 20. The first vehicle axle
20 is driven permanently by the first output shaft 16 so that the
first vehicle axle 20 is also called the primary axle. The primary
axle 20 serves for the driving of vehicle wheels 22.
[0031] The transfer case 12 furthermore has a second output shaft
24 which is connected via an axial differential 26 to a second
vehicle axis 28, the so-called secondary axle, which serves for the
driving of vehicle wheels 30.
[0032] In the present embodiment, the primary axle 20 represents a
rear axle of the vehicle and the vehicle wheels 22 correspondingly
represent rear wheels, while the secondary axle 28 is a front axle
and the vehicle wheels 30 are front wheels of the vehicle.
Generally, however, the primary axle 20 can also be a front axle
and the secondary axle 28 can be a rear axle.
[0033] For the distribution of the drive torque of the engine 10
between the first output shaft 16 and the second output shaft 24,
the transfer case 12 has a clutch 32 which is connected at the
input side to the first output shaft 16 and at the output side to
the second output shaft 24. The clutch 32 is a friction clutch, for
example a multi-disk clutch, and in particular a wet multi-disk
clutch
[0034] The actuation of the clutch 32, i.e. that is the engagement
state or disengagement state of the clutch 32, is controlled by
means of a control 34. The proportion of the drive torque which is
or can be transmitted via the second output shaft 24 to the front
wheels 30 is set by the degree of the engagement of the clutch
32.
[0035] A chain drive 36 is connected between the output side of the
clutch 32 and the second output shaft 24, with a gear connection
also being able to be provided instead of a chain drive 36. The
chain drive 36 does not only serve for the transmission of torque
from the clutch 32 to the second output shaft 24, but rather it
additionally conveys lubrication oil from an oil sump 38 arranged
in a lower region of the transfer case 12 into a region of the
transfer case 12 disposed above the clutch 32. The chain drive 36
therefore forms an oil conveying device 40 in addition to a torque
transmission device.
[0036] The lubrication oil conveyed upward by the chain drive 36
serves for the lubrication of the clutch 32 as well as of other
components of the transfer case 12, such as of bearings, and is
collected in an oil reservoir 42. The lubrication oil conveyed
upward is stored in the oil reservoir 42 such that the oil level in
the oil reservoir 42 is above an outlet opening of a supply line
(not shown) leading from the oil reservoir 42 to the clutch 32 or
to the other components of the transfer case 12 so that the
lubrication oil can flow to the clutch 32 or to the other
transmission components due to gravity.
[0037] It must be pointed out that the oil reservoir 42 does not
necessarily have to be provided. Instead, it is also possible to
supply the lubrication oil conveyed upward by the chain drive 36
directly to the clutch 32 or to the other components of the
transfer case 12.
[0038] It is easy to understand that the chain drive 36 only acts
as an oil conveying device 40 when the second output shaft 24
rotates, i.e. that is when the clutch 32 is at least partially
engaged, and/or when the second output shaft 24 is driven by the
front wheels 30 with a moving vehicle. Conversely, no oil conveying
takes place when the second output shaft 24 is stationary.
[0039] To prevent the secondary axle 28 and the second output shaft
24 from being set into motion by the rotating front wheels 30 with
a disengaged clutch 32, i.e. on a drive of the vehicle exclusively
via the primary axle 20, and thus from unnecessary moments of
inertia being produced, a shutdown device is provided for the
shutting down of the secondary axle 28 and of the second output
shaft 24. The shutdown device is formed by dog clutches 44 arranged
at the hubs of the front wheels 30 by which the front wheels 30 can
be rotationally effectively decoupled from the secondary axle
28.
[0040] Alternatively, the shutdown device can also be arranged at
the axial differential 26 of the secondary axle 28. In this case,
only the second output shaft 24 would be rotationally effectively
decoupled from the front wheels 30, whereas the secondary axles 28
would always rotate together with the front wheels 30.
[0041] It has already been mentioned that no conveying of
lubrication oil from the oil sump 38 into the oil reservoir 42
takes place when the secondary output shaft 24 is shut down. On a
drive of the vehicle only via the primary axle 20, there is
therefore generally the danger that sufficient lubrication oil is
not available in the oil reservoir 42 for the lubrication of the
clutch 32 or of the other transmission components.
[0042] In order always to store a quantity of lubrication oil in
the oil reservoir 42 sufficient for the lubrication of the clutch
32 and of the other transmission components or in order also to
ensure a sufficient lubrication of the clutch 32 and of the other
transmission components without any oil reservoir 42 present, the
control 34 therefore ensures that an oil conveying also takes place
from time to time with a generally shut down second output shaft 24
in that the control 34 commands an at least partial engagement of
the clutch 32 from time to time, whereby the chain drive 35 is
actuated and an oil conveying is thus set in motion.
[0043] In this respect, the engagement of the clutch 32 from time
to time, and thus the length of an oil conveying procedure or the
time interval between two sequential oil conveying procedures, can
follow a predetermined regular or irregular pattern or can take
place in a demand-oriented manner with reference to the oil level
in the oil reservoir 42 which can be detected with the help of a
suitable oil level sensor or determined with reference to a map or
calculation model and transmitted to the control 34. In addition,
the clutch 32 can always be engaged when the vehicle is braked,
e.g. by a foot brake or by an engine brake.
[0044] Finally, it must be pointed out that the oil conveying
device 40 for the conveying of lubrication oil from the oil sump 38
into the oil reservoir 42 does not necessarily have to be a chain
drive 36 or a corresponding gear connection connected between the
clutch 32 and the second output shaft 24, but that the oil
conveying device 40 can rather also be a separate oil pump. Such an
oil pump can, for example, be a gerotor pump which is driven by the
second output shaft 24 and which is actuable by an at least partial
engagement of the clutch 32 from time to time with a generally shut
down second output shaft 24 in accordance with the chain drive 36.
Alternatively, the oil pump can, however, also be an electrically
driven pump which is activated occasionally by the control 34 or by
another suitable control when the output shaft 24 is shut down.
TABLE-US-00001 Reference numeral list 10 engine 12 transfer case 14
drive shaft 16 first output shaft 18 axial differential 20 first
vehicle axle/primary axle 22 vehicle wheels 24 second output shaft
26 axial differential 28 second vehicle axle/secondary axle 30
vehicle wheels 32 clutch 34 control 36 chain drive 38 oil sump 40
oil conveying device 42 oil reservoir 44 dog clutch
* * * * *