Drive unit with oil exchange
The invention relates to a drive unit for vehicles, the
'drive unit having a gearing, a brake and, arranged
5 therebetween, an electric machine. Here, the electric
machine has a cooling arrangement which functions
separately from the further components. In the further
components, a separate lubrication circuit is
maintained using existing components, and the
10 lubrication circuit is utilized as .a further cooling
circuit.
Prior art
15 The document DE69323553 T2 is known from the prior art.
Said document presents a drive unit with a liquidcooled
electric motor and with a connected planetary
gear set. Said drive device provides a water-type
cooling arrangement for the electric motor, wherein the
20 cooling circuit is driven by a pump function in the
planetary gear set. For this purpose, the connected
planetary gear set must be of s-uitable construction,
and the components must be specially pre-formed. In the
prior art, for this purpose, the internal gear of the
25 planetary gear set is formed such that two separate
chambers are generated in the gearing housing, the
content of which chambers is pumped into the cooling
circuit of the electric motor by way of the movement of
the internal gear.
30
Said solution requires a special design of the gearing
and an adapted design of the gearing housing, which
make it possible to provide the required cooling flow
rate.
The presented solution comprises the function of
lubricating components with the function of cooling the
electric machine in a circuit with a cooling fluid. A
disadvantage is the functionally induced mixing of the
cooling liquid with air, which results in significantly
decreased heat transfer.
5 DE 4410074 discloses a. function for the lubrication of
bearing points. Here, a differential that is driven by
an electric motor is supplied with lubricant via a
hollow shaft. The solution presented in the document
however does not present an approach for solving the
10 problem as to how the lubricant is transported to the
bearing points of the differential.
It is an object of the present invention to provide a
drive unit with an improved design in relation to the
15 known solutions. In particular, it is sought to provide
a solution in which components are separated from one
another by an electric machine but are lubricated and
cooled by means of a common system. The lubricant is
required both for the bearings of the electric machine,
20 for the gearing and also for the bearings of the drive
input and drive output flanges. Since an electric
machine is arranged between the components, there is
the problem that there are two separate oil chambers.
25 The problem is solved by means of a drive unit
according to the invention having the features of claim
1. The solution has a gearing, a brake and, arranged
therebetween, an electric machine, wherein the stator
of the electric machine has a cooling jacket and the
30 cooling of the further components is performed by way
of a separate lubrication circuit, wherein the drive
unit has means for maintaining the lubrication circuit.
The separate lubrication circuit advantageously also
performs the cooling function.
The further separate lubrication circuit advantageously
connects the oil chamber of the gearing to the oil
chamber of the brake.
It is advantageous that the lubrication circuit is led
through a hollow shaft of the electric machine.
It is furthermore advantageous that the oil-conducting
duct of the hollow shaft is fed from the oil chamber of
the gearing by way of the positive displacement of oil
from the intermediate spaces of the toothing
engagements of the sun gear. In this way, a uniform
feed of oil from the oil chamber of the gearing into
the oil chamber assigned to the brake is ensured.
An oil duct arranged in the housing conducts the oil
that is fed in back to the oil chamber of the gearing,
and realizes a closed lubrication circuit.
Through the advantageous use of the toothing
engagements of the sun gear in the gearing for feeding
oil from the oil chamber of the gearing into the oil
chamber of the brake, and owing to the advantageous
design of the duct, uniform lubrication of the bearing
points is ensured, and different oil levels are
generated in the two oil chambers during operation.
Description of the invention
The solution according to the invention, and the
advantageous embodiment thereof, will be explained in
more detail in the following description on the basis
of a single figure.
Figure 1 shows a longitudinal section through the drive
unit according to the invention. Figure 1 illustrates a
drive unit 1 according to the invention which is
composed of an electric motor 2 and a gearing 3 and a
brake 4. All of the individual components of the drive
unit 1 are combined in one housing. Here, the housing
5 of the electric machine 2 is denoted by 5, the bearing
cover of the brake is denoted by 6, and the housing of
the gearing is denoted by 7. The housing parts 5, 6, 7
are sealingly connected to one another and may also be
of multi-part construction. For example, in the figure,
10 the housing of the gearing 7 is of two-part form. The
electric machine 2 depicted in the figure has a stator
8 and a rotor 9. The rotor 9 is fixedly connected to a
hollow shaft 11 and is rotatably mounted, by way of the
bearings 13 and 14, in the housing parts 6 and 7. The
15 electric machine 2 has a cooling jacket 10. The cooling
of the electric machine 2 is realized separately from
the lubrication circuit. The electric machine 3 is
generally advantageously water-cooled. Furthermore, the
stator 8 and the rotor 9 of the electric machine 2 are
20 sealed off by the bearings 13 and 14, and the chamber
of stator 8 and rotor 9 is filled only with air.
The electric machine 2 is advantageously a permanently
excited synchronous machine. The invention is however
25 not restricted to this type of machine. Any electric
machine suitable for drive purposes may be used in the
solution according to the invention.
The hollow shaft 11 is part of a first duct 12 which
30 extends from the gearing side to the brake side. The
tube 30 is inserted into the hollow shaft 11 on that
side of the hollow shaft 11 which faces toward the
gearing 3, and said tube extends to a point close to
the toothing engagements 18 of the sun gear shaft 22.
35 At that side, the tube 30 has a constriction. The first
duct 12, which is arranged in the manner of a jacket
within the tube 30 and within the hollow shaft 11,
widens conically slightly in stepped fashion in the
direction of the brake 4. The duct opens out in the
second oil chamber 21 via passage openings 16 which are
5 formed by relief portions on the tooth tips of the
driving toothing between hollow shaft 11 and sun gear
shaft 22. The second oil chamber 21 of the brake 4 is
connected to the first oil chamber 20 of the gearing 3
via a housing duct 17 which runs in the housing 5 and
10 in the housing 7.
The gearing arrangement illustrated .in the drawing is a
planetary gear set composed of a sun gear of the sun
gear shaft 22, planet gears 23, and a hollow gear 24.
15 The sun gear shaft 22 is connected rotationally
conjointly to the hollow shaft 11 of the electric
machine 2 and to the brake flange 27, and is mounted in
the bearing cover of the brake 6 by way of the brake
flange 27. The drive output shaft 25 is mounted in the
20 housing of the gearing 7 and is in the form of a planet
carrier on which planet gears 23 are mounted. The drive
output flange 26 is seated concentrically on, and
connected rotationally conjointly to, the drive output
shaft 25. When the drive unit is in operation, oil is
25 drawn out of the oil sump of the first oil chamber 20
by the planet gears 23.
Owing to the contact in the toothing engagements 18,
oil is squeezed between the sun gear of the sun gear
30 shaft 22 and the planet gears 23. A partial stream of
said squeezed oil is conveyed tangentially and axially
into the tube 30 and, owing to the constriction, can no
longer flow out into the first oil chamber 20.
35 Here, the gearwheels 22, 23 perform the function of a
pump with positive displacement action, which
transports oil from the first oil chamber 20 into the
tube 30 of the first duct 12. Owing to the centrifugal
positive displacement action in the duct 12 with the
slightly conical widening, a directed oil flow in the
direction of the brake is obtained. The oil flows
through the first duct 12, which widens toward the
passage openings 16. The oil passes through the passage
openings 16 into the second oil chamber 21 and to the
bearing of the brake flange 27, on which the further
rotating parts, not illustrated in figure 1, of the
brake 4 are seated.
When the drive unit 1 is in operation, oil is conveyed
from the first oil chamber 20 into the second oil
chamber 21. The oil level in the first oil chamber 20
falls, as a result of which splashing losses are
greatly reduced.
The lubrication circuit is completed by a housing duct
17 which connects the oil chamber 21 of the brake 4 to
the oil chamber 20 of the gearing 3. Oil flows into the
housing duct 17 via an inlet opening 15 in the oil
chamber 21 of the brake 4, and said oil is conducted
into the oil chamber 20 of the gearing 3 via an outlet
opening 19 in the lower region of the first oil chamber
20. Adaptation of the dimensioning of the housing duct
17 with the inlet and outlet openings 15 and 19 in
conjunction with different heights of the inlet and
outlet openings 15 and 19 ensures a desired oil level
setting in the oil chambers 20 and 21. According to the
invention, during operation of the drive unit 1, the
level in the first oil chamber 20 is much lower than
the level in the second oil chamber 21.
The second oil chamber 21 is used as a flow-calmed oil
chamber. Through suitable configuration of the bearing
cover of the brake 6, the second oil chamber 21 may be
utilized as an oil reservoir. According to the
invention, the lubrication circuit is cooled by the
cooling jacket 10 via the housing duct 17.
The drive unit presented has been described in
conjunction with a planetary gear set. The solution
according to the invention may however also be realized
with other suitable gearing arrangements, provided that
10 these provide squeezed oil by the positive displacement
action of the toothing engagements and said oil. can be
captured and conveyed onward by suitable means.
Furthermore, the electric machine of the drive unit
presented is operated as a motor and as a generator. In
15 the description of the invention, the lubricant has
been described using the term "oil" . The invention is
however not intended to be restricted to oil; any other
lubricating fluid may be used in the solution according
to the invention.
List of reference numerals
Drive unit
Electric machine
Gearing
Brake
Housing of the electric machine
Bearing cover of the brake
Housing of the gearing
Stator
Rotor
Cooling jacket
Hollow shaft
First duct
Bearings
Inlet opening
Passage opening
Housing duct
Toothing engagement
Outlet opening
First oil chamber
Second oil chamber
Sun gear shaft
Planet gear
Hollow gear
Drive output shaft
Drive output flange
Brake flange
Tube

We claim:
1. A drive unit (1) for vehicles, the drive unit
having a gearing (3) , a brake (4) and, arranged
therebetween, an. electric machine (2) in an at
least two-part housing (5, 6, 7), wherein the
electric machine (2) has a cooling jacket (10) and
the lubrication of the further components (3, 4)
is performed by way of a separate lubrication
circuit, characterized in that the separate
lubrication circuit in the at least two-part
housing (5, 6, 7) for the gearing (3) and brake
(4) is maintained using existing components (23,
22, 11).
The drive unit (1) as claimed in claim 1,
characterized in that the separate lubrication
circuit also performs the cooling function.
The drive unit (1) as claimed in claims 1 and 2,
characterized in that the separate lubrication
circuit connects the first oil chamber (20) of the
gearing (3) to. the second oil chamber (21) of the
brake (4) .
25 4. The drive unit (1) as claimed in claim 1,
characterized in that the further lubrication
circuit is led through a hollow shaft (11) of the
electric machine (2) .
30 5. The drive unit (1) as claimed in claim 4,
characterized in that the hollow shaft (11) has a
first duct (12).
6. The drive unit (1) as claimed in claim 5,
35 characterized in that the first duct (12) extends
from the side of the gearing (3) to the side of
the brake (4) .
7. The drive unit (1) as claimed in claim 6,
characterized in that the first duct (12) widens
slightly conically in stepped fashion.
5 8. The drive unit (1) as claimed in claim 4,
characterized in that the first duct (12) is fed
from the first oil chamber (20) of the gearing (3)
by way of the positive displacement action 'of the
toothing engagements ( 18 ) .
9. The drive unit (1) as claimed in claim 6,
characterized in that the lubricant flows through
at least one passage opening (16) into the second
oil chamber (21) of the brake (4).
10. The drive unit (1) as claimed in claim 4,
characterized in that the return flow from the
second oil chamber (21) of the brake (4) into the
first oil chamber (20) of the gearing (3) takes
place via a housing duct (17) in the housing (5)
of the electric machine (2) and in the housing (7)
of the gearing (3 ) of the drive unit (1) .
11. The drive unit (1) as claimed in claim 4,
characterized in that the oil level in the first
oil chamber (20) of the gearing (3) is much lower
than that in the second oil chamber (21) of the
brake (4) .