DE102020211908A1 - Hydraulic system - Google Patents

Abstract

A hydraulic system (9) for a drive system (1) of a motor vehicle is proposed which has at least one electrical machine (2) and at least two gear stages (G1, G2) for the drive, the hydraulic system (9) having at least one actuator unit (10a ) for the control of two clutches (C1, C2), which can be connected to at least one further actuator unit (10b), which actuates two further clutches (C3, C4) and / or to a further actuator unit (10c) which is used for cooling the clutches (C1, C2, C3, C4) and the electric machine (2) is designed.

Description

The invention relates to a hydraulic system for a drive system of a motor vehicle which has at least one electrical machine and at least two gear stages for the drive, the hydraulic system having at least one actuator unit for controlling two clutches.

State of the art

There is currently a trend towards hybrid drive units in which a first drive unit such as an internal combustion engine is combined with an electric machine as the second drive unit.

Different concepts are known for the hybridization of dual clutch transmissions. For example, it is known to provide an electric machine between the friction clutches and the internal combustion engine, which leads to a P2 parallel hybrid. A friction clutch can be provided between the electrical machine and the first drive unit. The drive power of the electric machine can be fed into the first or the second transmission via the first friction clutch or the second friction clutch.

In another embodiment, an electrical machine is connected to one of the two sub-transmissions, that is, behind the associated friction clutch when viewed in the power flow direction, which is referred to as a P2.5 hybrid.

The clutches are actuated with a hydraulic system such as that in the EP 1 763 643 B1 is described in which the hydraulic circuit for dual clutch transmissions has a central valve which connects the pressure control valves to the respective clutches in a first position and separates the pressure control valves from the respective clutches in a second position. The actuation of the friction clutches takes place via a central motor-pump unit, an optional pressure accumulator and a proportional pressure or flow control valve for each friction clutch.

Furthermore, purely electric vehicles are increasingly being used, which are provided with simple two-speed transmissions or variably adjustable transmissions or transfer cases.

In the case of high-performance electric drive modules, often with 800V e-machines, in the power class of 200-320kW, there are high demands on the power density of the actuator components of the hydraulic system due to the limited installation space.

The very different variants of the drive systems with different drive units and gears each have to be installed with a hydraulic system that is adapted to the respective requirements. This reduces the number of pieces for the respective hydraulic systems.

It is the object of the invention to provide a hydraulic system with at least one actuator unit which is suitable without restrictions for the electrohydraulic actuation of many electric or hybrid drive systems and conventional four-wheel drives or transfer gear systems.

In addition, the hydraulic system with the actuator unit must be suitable to meet the requirements for the switching dynamics to be achieved and the desired fail-safe behavior in the event of malfunctions.

Description of the invention

The object is achieved with a hydraulic system for a drive system of a motor vehicle, which has at least one electrical machine and at least two gear stages for the drive, the hydraulic system having at least one actuator unit for controlling two clutches, which can be connected to at least one further actuator unit, which actuates two further clutches and / or with a further actuator unit which is designed to cool the clutches and / or the electrical machine.

The modular concept with several actuator units is used for controlled actuation, cooling and lubrication of up to four friction clutches. This means that platform components from other hydraulic systems such as the motor-pump units can also be used.
There are three actuator units used as main modules, control of a double clutch transmission, unit for a transfer case and a cooling unit for the electrical machine.

In addition, it can be used in all electrified drive systems which serve as primary or secondary drives and are equipped with a multi-step transmission and / or a transfer case for reasons of efficiency and / or performance.

The hydraulic system is particularly suitable for a drive system, with only one electric machine as a drive. In the case of purely electric drives with high outputs in the range of 200 to 300 kW, efficient and powerful hydraulics are particularly important. The cooling of the electrical machine is of great importance.

In one embodiment, the clutches are connected to individual, assigned displacement pumps with pump motors.

In an alternative embodiment, the couplings are connected to a single positive displacement pump with a pump motor.

It is particularly advantageous that the actuator unit has actuation paths for controlling two clutches, which are connected via a safety valve.

The safety valve is advantageously a total pressure valve.

The total pressure valve is designed as a valve sleeve with a valve piston which is displaceable against a force and which has two control edges for the first clutch pressure level and the second clutch pressure level.

It is advantageous to provide hydraulically releasable check valves in the actuation paths. This pressure holding function allows the electrical power consumption of the actuator unit to be minimized via optional pressure holding valves.

Figure list

• 1 zeigt ein beispielhaftes Getriebelayout einer ersten Ausführungsvariante als lastschaltbares Zweigang-Getriebe,
• 2 zeigt ein beispielhaftes Getriebelayout einer zweiten Ausführungsvariante als lastschaltbares Zweigang-Getriebe mit einer Verteilergetriebeeinheit,
• 3 zeigt ein beispielhaftes Getriebelayout einer dritten Ausführungsvariante als Eingang-Getriebe mit einer Verteilergetriebeeinheit,
• 4 zeigt eine schematische Darstellung eines erfindungsgemäßen Hydrauliksystems mit einer ersten Aktuatoreinheit für ein elektrische Antriebseinheit nach 1,
• 5 zeigt eine schematische Darstellung eines erfindungsgemäßen Hydrauliksystems mit einer ersten und einer zweiten Aktuatoreinheit für eine elektrische Antriebseinheit nach 2,
• 6 zeigt eine schematische Darstellung eines erfindungsgemäßen Hydrauliksystems mit modularen Aktuatoreinheiten für ein elektrische Antriebseinheit,
• 7 zeigt eine schematische Darstellung des Hydraulikkreises für ein elektrohydraulisches Betätigungskonzepte eines lastschaltbaren Doppelkupplungsgetriebes in einer ersten Ausführungsform,
• 8 zeigt eine schematische Darstellung des Hydraulikkreises eines lastschaltbaren Doppelkupplungsgetriebes in einer zweiten Ausführungsform,
• 9 und 10 zeigen eine beispielhafte Ausführung des erfindungsgemäßen Sicherheitsventils in der Ausführung als Summendruckventil,
• 11 zeigt eine schematische Darstellung des Hydrauliksystems nach 7, ergänzt um das erfindungsgemäße Sicherheitsventil nach 9 und 10,
• 12 zeigt eine schematische Darstellung des Hydrauliksystems nach 8, ergänzt um das erfindungsgemäße Sicherheitsventil nach 9 und 10,
• 13 zeigt eine weitere Ausgestaltung eines erfindungsgemäßen Hydrauliksystems mit einer ersten Aktuatoreinheit für ein elektrische Antriebseinheit mit zusätzlichen Druckhalteventilen.

The invention is described below by way of example with reference to the accompanying drawings.

• 1 shows an exemplary transmission layout of a first variant as a power shiftable two-speed transmission,
• 2 shows an exemplary transmission layout of a second variant as a power shiftable two-speed transmission with a transfer case unit,
• 3 shows an example of a transmission layout of a third variant as an input transmission with a transfer case unit,
• 4th shows a schematic representation of a hydraulic system according to the invention with a first actuator unit for an electric drive unit according to FIG 1 ,
• 5 shows a schematic representation of a hydraulic system according to the invention with a first and a second actuator unit for an electric drive unit according to FIG 2 ,
• 6th shows a schematic representation of a hydraulic system according to the invention with modular actuator units for an electric drive unit,
• 7th shows a schematic representation of the hydraulic circuit for an electrohydraulic actuation concept of a power shiftable double clutch transmission in a first embodiment,
• 8th shows a schematic representation of the hydraulic circuit of a power shiftable double clutch transmission in a second embodiment,
• 9 and 10 show an exemplary embodiment of the safety valve according to the invention in the form of a total pressure valve,
• 11 shows a schematic representation of the hydraulic system according to FIG 7th , supplemented by the safety valve according to the invention 9 and 10 ,
• 12th shows a schematic representation of the hydraulic system according to FIG 8th , supplemented by the safety valve according to the invention 9 and 10 ,
• 13th shows a further embodiment of a hydraulic system according to the invention with a first actuator unit for an electric drive unit with additional pressure holding valves.

1 shows drive system 1 using the example of a purely electric drive module. This is an electrical machine 2 used as the only drive unit that has an input shaft 4th drives. On the input shaft 4th is a first reduction gear stage for first gear G1 , as well as a second reduction gear stage for the second gear G2 arranged. On an intermediate shaft 5 are two clutches C1 and C2 arranged. Together they form a dual clutch transmission 3 . The two clutches alternatively each connect a loose wheel, which is in engagement with the associated fixed wheel of the reduction gear stages, frictionally with the intermediate shaft 5 . Via an output gear 6th is the intermediate shaft 5 with a differential 7th tied together. The differential 7th drives two half waves 8a and 8b which are each connected to a wheel of the vehicle.

The gearbox layout of this variant is designed as a power shiftable two-speed gearbox. In this version, the two clutches C1 and C2 Realize a shift without a noticeable interruption in traction.

2 shows a drive system of a second embodiment as a power shiftable two-speed transmission with a transfer case unit. In the following, the torque vectoring unit is referred to as the transfer case, which consists of a transfer unit with two friction clutches which are used for the controllable distribution of the drive torque to the left and right wheels of the driven axle 1 instead of a differential, another pair of clutches C3 and C4 used. These clutches alternately or jointly connect the two half-shafts 8a and 8b and thus the two wheels of the vehicle with the drive unit 2 .

3 shows a further embodiment with an input transmission, again being a combination of two clutches C3 and C4 the drive energy on the two half-waves 8a and 8b distributed.

The three embodiments of a purely electric drive have a different number of clutches and require different hydraulic systems to actuate these clutches.

4th shows a schematic representation of a hydraulic system according to the invention 9 with a first actuator unit 10a for the drive system 1 with electric drive unit 2 as in 1 executed. The actuator unit 10a needs two clutches C1 and C2 actuate hydraulically.

This is where the double clutch 3 of the powershift two-speed transmission operated via pressure control.

While a motor-pump unit with a pump motor 12a or 12b and a positive displacement pump 13a or 13b builds up the clutch pressure required for reliable transmission of the torque and keeps it constant or according to the torque requirement of the electric machine 2 adjusts as required, the other motor-pump unit with the pump motor 12a or 12b and the positive displacement pump 13a or 13b can be used for other functions in reversing mode. By reversing the direction of rotation of the pump motor and thus the pump, a pressure accumulator can be created 22nd filled or the active clutch oiled 23 as required.

The motor-pump unit shown in the exemplary embodiment with the pump motor 12a or 12b and the positive displacement pump 13a or 13b , has its own engine control unit ECU, which communicates via an internal CAN bus, called private CAN, with the further engine control unit ECU and also via a public CAN bus, called public CAN, with the vehicle or with another Control unit of the electric drive machine 2 connected is. The other components of the arrangement are explained in more detail in the following drawing.

In 5 the expansion of the hydraulic system is shown, which includes an additional actuator unit 10b is expanded. The actuator unit 10b applies to two more clutches C3 and C4 with an actuation pressure and is also connected to the motor-pump units with the pump motor 12a or 12b and the positive displacement pump 13a or 13b tied up. The inputs of the actuator unit 10b are connected to the motor-pump units of the Actuator unit 10a connected. The hydraulic system 9 with the two actuator units 10a and 10b is for the independent actuation of the four clutches of the drive system according to 2 suitable.

In the 6th is the hydraulic system 9 shown in a further design. The hydraulic system contains another actuator unit 10c that with another motor-pump unit 12th c and which is used to cool the electrical machine 2 and the couplings are in place. The actuator unit 10c therefore do not operate a clutch.

The actuator unit 10c can also be connected directly to the actuator unit 10a be coupled without using the actuator unit 10b and thus meet the cooling requirements of the transmission and the electrical machine.

The following table shows exemplary pressure ranges p1 until p4 of the hydraulic system 9 with the actuator units 10a , 10b , 10c listed: Pressure level Operating range p1 0 ... 42 bar p2 17 ... 42 bar p3 0 ... 15 bar p4 ~ 1 bar

p1, p2 denote a first clutch pressure level which is used to actuate the clutches C1 and C2 is required, p5 denotes the supply pressure level of the second actuator unit, specifically the accumulator pressure level, p3 and p4 are the clutch pressure level which is used to actuate the clutches C3 and C4 is required, p6 denotes the pressure level in a cooling / lubricating oil path.

7th shows a schematic representation of the hydraulic circuit for an electrohydraulic actuation concept of a power shiftable double clutch transmission in a first embodiment with the actuator unit 10a as well as in 4th shown. Thereby the two clutches C1 and C2 that act as friction clutches 17a and 17b are formed, each directly via a motor-pump unit, each with a pump motor 13a or 13b and a positive displacement pump 12a or 12b actuated.

The positive displacement pumps 12a or 12b are with an oil sump 22nd connected and build in the respective actuation path 11a or 11b an actuation pressure. The pressure is - measured with a pressure sensor 15a , 15b - on an actuating piston 16 a , 16b which the respective coupling C1 , C2 actuated. The pressure in the respective actuation path 11a , 11b and on the couplings C1 , C2 is controlled by an optional pressure relief valve 18a , 18 b limited to a maximum system pressure pmax. The pressure reduction takes place actively by reversing the direction of rotation of the respective motor-pump unit and passively, for example when the motor-pump unit is inactive, via one between the pressure side of the pump 13a and 13b and the oil sump 22nd arranged aperture 14a, 14b.

8th shows a schematic representation of the hydraulic system with an actuator unit 10d of a power shiftable double clutch transmission in a second embodiment. A single motor-pump unit is used with the pump motor 12th and the positive displacement pump 13th a central pressure accumulator 19th filled and the two couplings C1 and C2 are each via a proportional pressure control valve 20a , 20b actuated.

In the case of double clutch transmissions, incorrect simultaneous actuation of both clutches can generate a mechanical tension torque in the transmission. Depending on the current driving status, pulling, pushing, sailing operation, this can lead to a drop in the drive torque or to a sudden locking of the wheels. The latter must be prevented under all circumstances.

This is of particularly high relevance with 2-speed transmissions such as in the 1 and 2 shown where each sub-transmission consists of a reduction gear stage that is permanently connected to the input or output shaft G1 and G2 exists and thus no additional switching elements such as locking synchronizers or dog clutches for separating the power flow between the clutch and the output shaft are included.

Thus, the faulty simultaneous actuation of both clutches causes a mechanical tensioning torque which, depending on the effective rotating masses and the maximum The torque capacity of the clutches is composed of a short-term dynamic component and a static component.

Known solutions continuously check the pressure in both clutches and react to an unexpected pressure increase. On the one hand, this requires a pressure sensor in both clutches and, in the event of a fault, requires immediate and highly dynamic opening of the active clutch, provided that it can still be actively controlled in the event of a fault. This approach is problematic at high vehicle speeds in second gear and with an active clutch C2 . In this operating state, the clutch can be actuated unintentionally C1 Inadmissibly high tension torques in the gearbox as well as high acceleration of the electric drive machine to inadmissibly high speeds, right up to the bursting speed range.

Therefore, the hydraulic system described so far 9 improved to the extent that a hydraulic total pressure valve 30th is used. 9 and 10 show an exemplary embodiment of such a safety valve in the form of a total pressure valve.

Via the summation pressure valve 30th becomes the pressure p1 and p2 on both couplings C1 and C2 added and with a preset spring force of a valve spring 33 compared.

In the event of a fault, depending on the design of the valve, the pressure p1 and p2 on both couplings C1 and C2 or just the pressure p1 or p2 on the couplings C1 or C2 can be dismantled directly via the safety valve. In a further embodiment of the hydraulic summation pressure valve 30th can the valve spring 33 can be replaced by the electromagnetic force of a switching or proportional magnet, whereby further fault cases can be secured.

The respective effective clutch pressure p1 , p2 of clutch C1 and clutch C2 is connected to a common valve piston via one line 32 of the summation pressure valve 30th guided.

The summation pressure valve 30th has a valve sleeve 31 on, in which there is a valve piston 32 longitudinally displaceable against the valve spring 33 supports. The first pressure input with the clutch pressure p1 lies on the face 35a of the valve piston 32 at. The second pressure inlet is in an annular area between the valve piston 32 and the valve sleeve 31 . This ring area is created by reducing the diameter of the valve piston 32 and an enlarged diameter of the valve sleeve is formed. Gap seals 34a, 34b and 34c seal the valve piston 32 against the valve sleeve 31 away. The output p _T denotes the unpressurized drain into the oil sump 22nd . 9 shows the summation pressure valve 30th in the basic position without pressurization.

In 10 is the summation pressure valve 30th shown in a pressurized position. Due to the geometric design of the valve piston 32 there are two piston surfaces A1, A2 which interact with the corresponding surfaces of the valve sleeve. The first piston surface A1 creates a first control edge 35a formed with the control edge 35b the valve sleeve 31 cooperates. The piston surface A2 forms a second control edge 36a off that in turn with the control edge 36b the valve sleeve 31 corresponds.

The opening behavior of the total pressure valve 30th is determined by the choice of the piston area ratios A1: A3 and the overlap of the control edges 35a , 35b and 36a , 36b , as well as optionally through the additional introduction of fine control notches on the control edges 35a , 35b and or 36a , 36b influenced. Thus, different nominal pressure levels of clutch C1 and clutch C2 taken into account and weighted differently.

Corresponding design and coordination of the piston surfaces can result in incorrect actuation of the clutch C1 or from clutch C2 be weighted differently. For example, with clutch C2 a higher pressure may be permissible in the event of a fault than with the coupling C1 .

As an alternative to the sum pressure valve described 30th An electrically operated switching valve, which is open when de-energized, or a proportional pressure-reducing valve can also be used. This means that additional error cases can be covered. For example, this can prevent unintentional actuation and, as a result, an unwanted pressure build-up in one or both clutches in the neutral (decoupled) position of the transmission.

11 shows an embodiment of the hydraulic system as in 7th with a first actuator unit 10a for an electric drive unit with an additional total pressure valve 30th between the actuation paths 11a and 11 b .

12th shows the embodiment according to 8th using the summation pressure valve 30th between the actuation paths 11a and 11 b .

The following table shows examples for a preset total pressure of 130% in different distributions on the couplings C1 and C2 : Clutch pressure C1 [%] Clutch pressure C2 [%] Clutch pressure C1 + C2 [%] 100 30th 130 80 50 130 65 65 130 50 80 130 30th 100 130

The exemplary operating states are selected in such a way that they are just possible with a set total opening pressure of 130% without the safety valve responding.

13th shows an embodiment according to 6th with additional pressure holding valves. In the embodiment shown, these are designed as hydraulically releasable check valves R1 and R2, which are connected to respective control lines z1, z2 to the first and second hydraulically releasable check valves. This means that any pressure level can be maintained and the pressure in the direction of the clutches can be increased as required.

The pressure reduction takes place by hydraulic unlocking via the respective control line z1, z2 with simultaneous actuation of the respective other motor-pump unit with pump motor 12a , 12b and positive displacement pump 13a , 13b . If the components are optimally designed, the pressure required to unlock the check valve R1, R2 is below the piston pressure applied by the return or release spring acting on the clutch piston.

The summation pressure valve 30th can either just for the clutch C2 For example, for design as an efficiency gear, but also only for the clutch C1 or, as in 13th shown for both couplings C1 and C2 in the embodiment according to 2 be used.

This enables the clutch to be overlocked (a so-called clutch-overlock function) at any torque level, which works entirely or almost without any electrical holding power requirement. The pressure supply of the transfer case unit can take place at the same time through both motor-pump units during sporty operation of the vehicle with the clutch of the two-speed transmission over-locked. Likewise, an increased cooling / lubricating oil requirement in this operating mode can be applied by both motor-pump units at the same time.

List of reference symbols

1

Drive system

2

Electric machine

3

Double clutch

4th

Input shaft

5

Intermediate shaft

6th

Output gear

7th

differential

8 a, b

Half waves

9

Hydraulic system

10a, 10b, 10c

Actuation unit

11 a, b

Actuation path

12 a, b

Pump motor

13 a, b

Positive displacement pump

14 a, b

cover

15 a, b

Pressure sensor

16 a, b

Actuating piston

17 a, b

Friction clutch

18 a, b

Pressure relief valve

19th

Pressure accumulator

20 a, b

Proportional pressure reducing valve

22nd

Oil sump

23

Oiling

30th

Summation pressure valve

31

Valve sleeve

32

Valve piston

33

Valve spring

34 a, b, c

Gap seal

35 a, b

first control edge

36 a, b

second control edge

C1, C2, C3, C4

coupling

G1

Reduction gear stage for gear 1

G2

Reduction gear stage for gear 2

p1

first clutch pressure level (clutch C1 )

p2

second clutch pressure level (clutch C2 )

p3

third clutch pressure level (clutch C3 )

p4

fourth clutch pressure level (clutch C4 )

p5

Supply pressure level of the second actuator unit, accumulator pressure level

p6

Pressure level in a cooling / lubricating oil path

pT

pressureless connection to the oil sump

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 1763643 B1 [0005]

Claims (8)

Hydraulic system (9) for a drive system (1) of a motor vehicle, which has at least one electric machine (2) and at least two gear stages (G1, G2) for the drive, the hydraulic system (9) having at least one actuator unit (10a) for control of two clutches (C1, C2), which can be connected to at least one further actuator unit (10b), which actuates further clutches (C3, C4) and / or to a further actuator unit (10c) which is used to cool the clutches (C1, C2, C3, C4) and the electrical machine (2) is designed. Hydraulic system (9) for a drive system (1) of a motor vehicle according to Claim 1 , with only one electric machine (2) as a drive. Hydraulic system (9) for a drive system (1) according to Claim 1 or 2 , characterized in that the clutches (C1, C2) are connected to individual, assigned displacement pumps (13a, 13b) with pump motors (12a, 12b). Hydraulic system (9) for a drive system (1) according to Claim 1 or 2 , characterized in that the clutches (C1, C2) are connected to a single positive displacement pump (13) with a pump motor (12). Hydraulic system (9) for a drive system (1) according to one of the preceding claims, characterized in that the actuator unit (10a) for controlling two clutches (C1, C2) has actuation paths (11a, 11b) which are connected via a safety valve . Hydraulic system (9) for a drive system (1) according to Claim 5 , characterized in that the safety valve is a sum pressure valve (30). Hydraulic system (9) for a drive system (1) according to Claim 6 , characterized in that the summation pressure valve is designed as a valve sleeve with a valve piston displaceable against a force and has two control edges for the first clutch pressure level and the second clutch pressure level. Hydraulic system (9) for a drive system (1) according to one of the preceding Claims 5 until 7th , characterized in that the safety valve is connected to the actuation paths (11a, 11b) via hydraulically releasable check valves.

Images