[0001] The invention relates to a pump unit for providing a hydraulic pressure for actuating
an actuator in the drive train of a motor vehicle, in particular a clutch actuator
or gearbox actuator, with a pump, a storage container for hydraulic fluid and two
pressure outlets.
[0002] The pump unit serves to provide a hydraulic pressure which is controlled or regulated
by activation of the solenoid valve. The hydraulic pressure can be used to switch
a clutch between an open and a closed position or, in the case of a gearbox actuator,
to switch a certain gear stage.
[0003] Each of the two pressure outlets serves to act upon one of two clutches of a dual
clutch gearbox. For example, the first clutch is then used to switch gear stages,
1, 3, 5 and 7 and the second clutch to switch gear stages 2, 4, 6, 8.
[0004] It is the object of the invention to increase the operational reliability of the
pump unit.
[0005] To achieve this object, in the case of a pump unit of the type mentioned at the beginning,
according to the invention, the storage container is divided into two chambers, wherein
a first intake opening of the pump is arranged in one chamber and a second intake
opening of the pump is arranged in the other chamber. This ensures that, in the event
of a hydraulic leakage in one circuit, only this circuit runs dry and therefore fails,
while the other circuit remains operationally ready as before. This makes it possible
for the driver of the vehicle to continue to operate the vehicle in a limited manner,
namely just with either the even or the odd gear stages. At any rate, the vehicle
can therefore be driven, for example, into a parking bay, from a busy street onto
the pavement or even home or to a garage.
[0006] It is preferably provided that the intake openings are arranged in the vicinity of
the base of the corresponding chamber. This reduces the dead volume in the corresponding
chamber and correspondingly increases the volume of hydraulic fluid which is available
as working volume.
[0007] In order to divide the storage container into two chambers, use can be made of a
substantially horizontally extending partition, wherein the partition has a vertically
extending end wall. Alternatively, it can be provided that the storage container is
divided by a substantially vertically extending partition into the two chambers. In
each case, the profile of the partition can be selected in such a manner that the
external dimensions of the storage container meet the corresponding specifications.
[0008] According to a preferred embodiment, the normal filling level of the storage container
lies above the uppermost edge of the end wall or the partition. This ensures that,
in the normal state, hydraulic fluids are exchanged between the two circuits. In the
event of a minor leakage, the time to failure is thereby also extended since the circuit
losing hydraulic fluid initially takes the latter out of the common volume above the
uppermost edge of the end wall or the partition.
[0009] So that the storage container can be configured compactly, the volume which is common
to the two circuits and is contained in the storage container is smaller between the
uppermost edge of the end wall or the partition and the normal filling level than
the sum of the separate volumes which are each formed within each chamber as far as
the uppermost edge of the end wall or the partition.
[0010] In order to ensure short intake paths for the pump, the storage container is preferably
attached directly to the pump housing.
[0011] According to a preferred embodiment of the invention, two solenoid valves are provided
with which the fluid pressure at the pressure outlets can be controlled, wherein one
of the solenoid valves is arranged in a chamber of the storage container and the other
solenoid valve is arranged in the other chamber. This has the advantage that the two
solenoid valves can be cooled directly by the hydraulic fluid. Furthermore, they are
protected against environmental influences and corrosion. If the hydraulic fluid also
surrounds the armature of the solenoid valve, a constant damping behaviour is ensured.
[0012] The invention will be described below with reference to an embodiment which is illustrated
in the attached drawings. In the latter:
- Figure 1 shows a pump unit in a perspective view;
- Figure 2 shows the pump unit from Figure 1 in a perspective exploded view;
- Figure 3 shows the pump unit from Figure 1 in a side view;
- Figure 4 shows the pump unit from Figure 3 in a first sectional view;
- Figure 5 shows the pump unit from Figure 3 in a second sectional view;
- Figure 6 shows a hydraulic circuit diagram of the pump unit;
- Figure 7 shows the circuit diagram from Figure 6, wherein the hydraulic flow is shown
for two different operating states;
- Figure 8 shows the circuit diagram from Figure 6, wherein a further operating state
is shown;
- Figure 9 shows the circuit diagram from Figure 6, wherein the filters used in the
pump unit are added;
- Figure 10 shows a side view of a storage container which is used in the pump unit;
- Figure 11 shows a partial view of an alternative configuration of the storage container;
- Figure 12 shows a schematic illustration of the various volumes within the storage
container;
- Figure 13 shows a sectional view of a solenoid valve used in the pump unit;
- Figure 14 shows the solenoid valve from Figure 13, wherein the fluid flows during
operation have been drawn in;
- Figure 15 shows a sectional view through the pump unit, wherein a conductor element
is shown which is used for transmitting signals between pressure sensors and a printed
circuit board;
- Figure 16 shows the conductor element from Figure 15 in a perspective view;
- Figure 17 shows the conductor element from Figure 16 in a longitudinal section;
- Figure 18 shows the conductor element from Figure 16 in a cross section;
- Figure 19 shows a variant embodiment of the conductor element;
- Figure 20 shows a detail of the contact connection of the pressure sensor;
- Figure 21 shows a cross section through the pump of the pump unit.
[0013] The figures illustrate a pump unit which serves to provide a hydraulic pressure (and
also a hydraulic fluid flow) which can be converted by an actuator in the drive train
of a motor vehicle into an actuating stroke. The actuating stroke can be used to close
or open a clutch, for example, or can be used to switch a gear stage of a gearbox
or to bring same into the neutral position.
[0014] As essential components (see in particular Figures 1 and 2), the pump unit has a
drive motor 1, a pump 2, an electronic control system 3, two solenoid valves 4, two
pressure sensors 5, which are accommodated in a common housing, and a storage container
6.
[0015] The central component of the pump unit is a pump housing 7 on which the solenoid
valves 4 are mounted and on which the storage container 6 is also mounted. The pressure
sensors 5 are also mounted on the pump housing 7.
[0016] On the side opposite the storage container 6, an electronic housing 8 is mounted
on the pump housing 7, said electronic housing firstly accommodating the electronic
control system 3 and secondly containing the stator of the electric motor 1. A cover
9 is mounted on the electronic housing 8, the cover closing the electronic control
system 3 and serving to dissipate the heat lost from the electronic control system
3 to the environment.
[0017] As can be seen in Figures 4 and 5, the solenoid valves 2 are arranged within the
storage container 6.
[0018] The electric motor 1 is a brushless electric motor with which the pump 2 is driven.
[0019] The pump 2 is a rotary vane pump (see Figure 21) which has a rotor 10 with a plurality
of chambers 12, in each of which a rotary vane element 14 is arranged. The rotary
vane elements 14 are cylindrical rollers. The pump is therefore a roller vane pump.
[0020] The cylindrical rollers roll on the inner contour of a stator 16 which defines a
volume which is variable in the circumferential direction. Accordingly, during rotation
of the rotor 10 by 360°, each rotary vane element passes twice through a sequence
of intake region A and pressure region D. Accordingly, the pump has two suction connections
and two pressure outlets.
[0021] Owing to the two independent pressure outlets D of the pump 2, the pump unit likewise
has two pressure outlets 20 which are independent of each other.
[0022] The pump is constructed symmetrically by all the components which will be explained
below being present for each pressure outlet. Thus when, for example, "the" solenoid
valve is described below, this applies to the two solenoid valves since one is present
for each pressure outlet.
[0023] The basic operation of the pump unit will now be explained with reference to Figures
6 to 8.
[0024] The pump unit has two pressure outlets 20 via which the hydraulic pressure is provided
which is produced by the pump unit for actuating the actuator.
[0025] A nonreturn valve 22 is arranged downstream of each pressure outlet D of the pump
2. The nonreturn valves 22 have a valve seat made of rubber.
[0026] The inlet 24 of the solenoid valve 4 is located downstream of the outlet of the nonreturn
valve 22. Depending on the desired pressure and the actual pressure measured at the
pressure sensor 5, each of the solenoid valves 4 is activated in such a manner that
the desired hydraulic pressure is present at the pressure outlet 20 of the pump unit.
Excess hydraulic fluid is conducted back directly into the storage container 6 by
a return line 26.
[0027] The solenoid valves 4 are designed as proportional valves and, as valve element,
have a ball which, together with the valve seat, ensures that the solenoid valve 4
is free from leakage in the closed state.
[0028] The right side of Figure 7 shows the fluid flow in a state in which hydraulic pressure
is not intended to be provided at the right pressure outlet 20.
[0029] All of the hydraulic fluid is pumped back from the pressure outlet D of the pump
2 in the solenoid valve 4 via the return line 26 into the storage container 6; the
pump therefore operates in a circuit.
[0030] The left side of Figure 7 shows the state in which a regulated hydraulic pressure
is provided at the pressure outlet 20 of the pump unit. In this case, the solenoid
valve 4 is activated by the electronic control system 3 in such a manner that the
actual pressure corresponds to the desired pressure.
[0031] Figure 8 shows the pump unit in a state in which the pump 2 has been stopped. The
solenoid valve 4 on the right side is open, and therefore the right pressure outlet
20 is free from pressure.
[0032] By contrast, the left pressure outlet 20 is shut off since the solenoid valve 4 is
completely closed. A hydraulic pressure built up downstream of the pressure outlet
20 will therefore be maintained even if the pump 2 is not operated further.
[0033] The filters which are used within the pump unit will now be explained with reference
to Figure 9.
[0034] An essential feature of the concept for keeping impurities away from the pump unit
is that no suction-side filters are used; all of the filters are arranged on the pressure
side. Accordingly, the pump sucks up directly from the storage container 6.
[0035] A first filter 30 is located downstream of the corresponding pressure outlet of the
pump 2. Said filter serves to filter out impurities from the hydraulic fluid before
said impurities pass to the solenoid valve 4. Since a large portion of the hydraulic
fluid is conducted by the pump 2 to the solenoid valve 4 and from there via the return
line 26 to the storage container 6, the two filters 30 ensure that impurities are
continuously filtered out from the hydraulic fluid because of the inner circulation
of the hydraulic fluid.
[0036] A second filter 32 is provided downstream of the solenoid valve 4, but still upstream
of the pressure outlet 20. Said filter prevents impurities from being able to be introduced
into the pump unit. Said impurities are in particular original soilings of the lines
and of the actuator and abrasion from the actuator, to which the hydraulic fluid is
provided by the pump unit.
[0037] The filters 30, 32 are configured to be effective throughout the entire service life
of the pump unit without having to be cleaned or replaced.
[0038] In the exemplary embodiment described, they have a cross section of the order of
magnitude of 65 mm
2. Their mesh width is of the order of magnitude of 0.1 mm.
[0039] The storage container 6 is provided with a filling filter 34 which is arranged in
such a manner that any hydraulic fluid which is filled into the storage container
6 via a filling opening 33 has to flow through the filling filter 34.
[0040] In the described exemplary embodiment, the filling filter 34 has a mesh width of
the order of magnitude of 0.3 mm, wherein the material of which said filling filter
is composed has a diameter of the order of magnitude of 0.2 mm. The filling filter
34 ensures that no impurities are introduced into the storage container 6 from the
outside.
[0041] The storage container 6 is divided into two chambers 40, 42, wherein an intake opening
44 leading to the suction connection A of the pump 2 is arranged in each chamber 40,
42. By dividing the internal volume of the storage container 6 into two separate chambers
40, 42, it is ensured that whenever one of the hydraulic circuits has a leakage, a
certain residual volume is still available in the other hydraulic circuit, with which
the nondefective hydraulic circuit can continue to be operated for a certain time.
[0042] Thus, for example, a driver, after receiving a warning about the failure of the first
hydraulic circuit, can still safely drive the vehicle into a parking bay or into a
parking space since, for example in the case of a dual clutch gearbox, a clutch and
the gearbox switching stages associated therewith are still ready for operation.
[0043] In order to divide the storage container 6 into the two chambers 40, 42, use can
be made of a substantially horizontally extending partition 46 which has a vertically
extending end wall 48 (see Figure 10), or a substantially vertically extending partition
50 (see Figure 11).
[0044] Each chamber 40, 42 has a dead volume T which corresponds to the volume below the
corresponding intake opening 44. A working volume W is located above the dead volume.
Said working volume W is determined by the uppermost edge of the end wall 48 or of
the partition 50. A common working volume GW is located above the working volumes
W.
[0045] The hydraulic circuits are separated from one another whenever the common working
volume GW drops to zero and each hydraulic circuit only still sucks up from its own
working volume W.
[0046] As is known from Figures 2, 4 and 5, the solenoid valves 4 are arranged within the
storage container 6. A solenoid valve is in each case arranged here in a chamber 40,
42.
[0047] Each of the solenoid valves 4 has a housing 60 (see Figure 13) which surrounds the
components of the solenoid valve 4.
[0048] The solenoid valve 4 has a nonreturn valve 62, a valve seat 64, a valve element 66,
an armature 68 and a coil 70. The hydraulic fluid flows via an intake 72 (see Figure
14) either to the pressure outlet 20 of the pump unit or via the opening cross section
between the valve seat 64 and the valve element 66 to the return line 26.
[0049] A particular feature consists in that the route to the return line 26 leads through
the interior of the housing 60. A corresponding return output 67 of the solenoid valve
is symbolized in Figure 14 by the vertically downwardly pointing arrow, the return
output beginning behind the valve seat and leading into the space within the housing
60.
[0050] By means of this arrangement of the return output of the solenoid valve 4, an encircling,
in particular annular, free space 74 which is present between the housing 60 and the
coil 70 is flushed through with hydraulic fluid.
[0051] The nonreturn valve 62 which is integrated here in the solenoid valve 4 corresponds
to the nonreturn valve 22 shown in Figures 6 to 9.
[0052] A further particular feature consists in that a bearing gap which is present between
the armature 68 and a bearing 76 inserted into the coil 70 and the solenoid valve
housing is likewise flushed through with hydraulic fluid.
[0053] A further particular feature of the solenoid valve 4 consists in that it is self-cleaning
since the path to the return line 26 removes any particles from the open valve seat
and the valve element.
[0054] It will now be explained with reference to Figures 15 to 20 how the pressure sensors
5 are connected to the electronic control system 3.
[0055] While, in the embodiment of Figures 1 and 2, a cable is still used for this purpose,
in the case of the configuration according to Figures 15 to 20 two inherently stable
conductor elements 80 are used. Each conductor element 80 contains three electric
conductors which are composed, for example, of spring bronze. The conductors 82 are
encased, in particular insert moulded, with plastic, such that the conductor element
80 is formed.
[0056] The conductors 82 are bent over by barely 180° on their side facing the pressure
sensor 5 such that spring contacts 86 are formed. The latter serve to lie in a spring-elastic
manner against corresponding connection contacts with the pressure sensors and thereby
to produce an electrical contact (see Figure 20).
[0057] The pressure sensor 5 is sealed on the side facing away from the conductor element
80 by means of various seals 114.
[0058] At the opposite end, the electric conductors 82 are designed as contact pins 88 which
can be inserted into a plug on a printed circuit board 90 on which the electronic
control system 3 is constructed.
[0059] The conductor element 80 extends from the printed circuit board 90 through a leadthrough
92 in the electronic housing 8 and into a receptacle 94 in the pump housing 7. The
conductor element 80 is sealed both in relation to the leadthrough 92 and in relation
to the receptacle 94. For this purpose, two seals 96, 98 are provided which provide
a seal within the leadthrough 92, and a seal 100 is provided which provides a seal
in relation to the receptacle 94.
[0060] The seals 96, 98, 100 are O rings which are accommodated in corresponding receiving
grooves 102, 104, 106 which are provided on the conductor element 80.
[0061] In the variant embodiment shown in Figure 19, a total of four receptacles for seals
are used.
[0062] The conductor element 80 is provided with a channel 110 which extends along the longitudinal
direction of the conductor element 80, specifically leading from the side which is
arranged in the receptacle 94, i.e. the side assigned to the pressure sensors 5, and
into a recess 112 between the seals 96 and 98, i.e. within the leadthrough 92.
[0063] The channel 110 serves to check with little outlay whether the two conductor elements
80 are correctly mounted, in particular whether the seals 96, 98, 100 are providing
a seal in the desired manner.
[0064] The test takes place by a negative pressure being applied in the region of the pressure
sensors. After a short settling time, it can be measured whether the applied negative
pressure remains constant or whether the pressure rises.
[0065] If the pressure remains constant, this means that all of the seals are providing
a seal in the desired manner. If the negative pressure becomes lower, this means that
at least one of the seals is not correctly providing a seal. This can either be the
seal 96, and therefore air is sucked out of the region of the printed circuit board
90 into the leadthrough 92 and via the recess 112 into the channel 110. It can also
mean that the seal 98 is not providing a seal, and therefore ambient air is sucked
out of the region between the leadthrough 92 and the receptacle 94 towards the recess
112. Finally, it can mean that the seal 100 is not providing a seal, and therefore
ambient air is sucked through the receptacle 94 towards the region of the pressure
sensors 5.
1. Pump unit for providing a hydraulic pressure for actuating an actuator in the drive
train of a motor vehicle, in particular a clutch actuator or gearbox actuator, with
a pump (2), a storage container (6) for hydraulic fluid and two pressure outlets (20),
characterized in that the storage container (6) is divided into two chambers (40, 42), wherein a first
intake opening (44) of the pump (2) is arranged in one chamber (40) and a second intake
opening (44) of the pump (2) is arranged in the other chamber (42).
2. Pump unit according to Claim 1, characterized in that the intake openings (44) are arranged in the vicinity of the base of the corresponding
chamber (40, 42).
3. Pump unit according to Claim 1 or 2, characterized in that the storage container (6) is divided by a substantially horizontally extending partition
(46) into the two chambers (40, 42), wherein the partition (46) has a vertically extending
end wall (48).
4. Pump unit according to Claim 1 or Claim 2, characterized in that the storage container (6) is divided by a substantially vertically extending partition
(50) into the two chambers (40, 42).
5. Pump unit according to either of Claims 3 and 4, characterized in that the normal filling level of the storage container (6) lies above the uppermost edge
of the end wall (48) or the partition (50).
6. Pump unit according to Claim 5, characterized in that the volume (GW) which is common to the two circuits and is contained in the storage
container (6) is smaller between the uppermose edge of the end wall (48) or the partition
(50) and the normal filling level than the sum of the separate volumes (W, T) which
are each formed within each chamber (40, 42) as far as the uppermost edge of the end
wall (48) or the partition (50).
7. Pump unit according to one of the preceding claims, characterized in that the storage container (6) is attached directly to a pump housing (7).
8. Pump unit according to one of the preceding claims, characterized in that two solenoid valves (4) are provided with which the fluid pressure at the pressure
outlets (20) can be controlled, wherein one of the solenoid valves (4) is arranged
in a chamber (40) of the storage container (6) and the other solenoid valve (4) is
arranged in the other chamber (42).