CN110864109A

CN110864109A - Hydraulic system for a dual clutch transmission

Info

Publication number: CN110864109A
Application number: CN201910771196.7A
Authority: CN
Inventors: R·诺瓦克; T·普夫勒格
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2018-08-27
Filing date: 2019-08-21
Publication date: 2020-03-06
Anticipated expiration: 2039-08-21
Also published as: DE102018214430A1; CN110864109B; FR3085196B1; FR3085196A1

Abstract

The invention relates to a hydraulic system (HY) for a twin clutch transmission (G) of a motor vehicle drive train, wherein the hydraulic system (HY) has a first pump (EP) for the pressure supply of a first pressure circuit (H1) and a second pump (MP) for the pressure supply of a second pressure circuit (H2), wherein the first pressure circuit (H1) is provided at least for the hydraulic actuation of a twin clutch (K1, K2) and for the hydraulic actuation of a parking lock (PS) of the twin clutch transmission (G), and the second pressure circuit (H2) is provided at least for the hydraulic actuation of a shift actuator (SK1, SK2) of the twin clutch transmission (G), and to a twin clutch transmission (G) for a motor vehicle having such a hydraulic system (HY).

Description

Hydraulic system for a dual clutch transmission

Technical Field

The invention relates to a hydraulic system for a dual clutch transmission of a motor vehicle drive train, and to a dual clutch transmission having such a hydraulic system.

Background

Different types of hydraulic transmission control devices are known in the prior art. Thus, for example, EP1469235a1 describes a hydraulic control and regulation system for use in a dual clutch transmission. In which a first hydraulic pump for supplying the high-pressure circuit and a second hydraulic pump for supplying the low-pressure circuit are arranged. The high-pressure circuit is assigned to the actuator, and the low-pressure circuit is used for cooling and lubricating the dual clutch transmission.

DE102004025764a1 describes a hydraulic circuit for the oil supply of an automatic transmission of a motor vehicle. The hydraulic circuit has a low-pressure circuit and a high-pressure circuit, each of which is supplied with a volume flow by a pump. The pressure in the low-pressure circuit can be regulated by means of a pressure-limiting valve. By actuating the pressure-limiting valve, the pressure level of the low-pressure circuit can be increased to the pressure level of the high-pressure circuit, whereby the non-return valve between the two pressure circuits is opened. The volumetric flows of the two pumps for supplying the high-pressure circuit can thereby be summed.

DE102009005756a1 describes a control device for a dual clutch transmission having two pumps. The two pumps supply a hydraulic circuit, via which the double clutches and the selector levers of the double clutch transmission can be hydraulically actuated.

Disclosure of Invention

The object of the present invention is to provide a novel hydraulic system for a dual clutch transmission, which is characterized in particular by good efficiency.

This object is achieved by the features of claim 1. Advantageous embodiments emerge from the dependent claims, the description and the drawings.

A hydraulic system for a dual clutch transmission of a motor vehicle drive train is proposed, which has a first pump for supplying a first pressure circuit with pressure and a second pump for supplying a second pressure circuit with pressure. The two pumps are formed by two pumps that are different from each other, i.e. not by a single double-circuit pump.

The hydraulic system according to the invention is characterized in particular in that a first pressure circuit is assigned to the hydraulic actuation of the double clutch and a hydraulic actuation of the parking lock of the double clutch transmission as hydraulic consumers, and a second pressure circuit is assigned to the hydraulic actuation of the shift actuator of the double clutch transmission as hydraulic consumers. With the described consumer configuration, the volumetric flow requirement of the first pump can be kept low, since during constant driving operation of a motor vehicle having a dual clutch transmission, only one of the two clutches of the dual clutch has to be supplied with actuating pressure. Although a relatively high pressure is required for hydraulically releasing the parking lock or, if necessary, for hydraulically holding the parking lock in the released state, only a small volume flow is required. Since the shift actuators of a dual clutch transmission usually actuate the dog clutches, no or only a small pressure and volume flow is required to hold the dog clutches during constant driving operation. The excess volume flow of the second pump can thus be used, for example, for cooling and lubricating the dual clutch transmission. Thus, such a hydraulic system has a particularly good efficiency.

Preferably, the two pressure circuits are connected to each other by a differential pressure valve. The differential pressure valve may be configured, for example, as a check valve, which is preferably spring-loaded so that, when the pressure difference is sufficient, a volume flow starting from the second pressure circuit into the first pressure circuit can be achieved.

For regulating the pressure in the second pressure circuit, a pressure regulating valve may be provided, which is pre-controlled by a pressure control valve. By actuating the pressure control valve accordingly, the pressure in the second pressure circuit can be adjusted to a value which is higher than the pressure in the first pressure circuit, so that the first pressure circuit can be supplied with the pressure and the volume flow of the second pump via the differential pressure valve. In constant driving operation, no or only a small pressure and volume flow is required in the second pressure circuit to hold the dog clutch. In this operating state, the pressure in the second pressure circuit can be kept low by actuating the pressure control valve, as a result of which the drive output of the second pump is kept low. In the case of an unstable driving operation of the motor vehicle, both the double clutch and the shift actuator are actuated in order to shift gears of the double clutch transmission. For this purpose, the pressure in the second pressure circuit can be increased by actuating the pressure control valves accordingly, so that the dog clutches to be opened and the dog clutches to be closed in the partial transmissions of the dual clutch transmission can be actuated. In order to actuate the clutch of the dual clutch that is to be closed during the shifting operation, the pressure in the second pressure circuit can be increased as required to such a high level that the differential pressure valve is opened and the volume flow of the second pump is also available for actuating the clutch that is to be closed.

Preferably, the supply connection of the pressure control valve is connected to the first pressure circuit. The pressure in the second pressure circuit is thus controlled independently of the pressure prevailing in the second pressure circuit. Since one clutch of the dual clutch is normally closed during operation of the motor vehicle, a relatively high pressure is inherently present in the second pressure circuit. The pressure in the first pressure circuit can thus be adjusted to the desired value particularly quickly.

Instead, the supply connection of the pressure control valve can be connected to the pressure side of the second pump. Since the volume flow requirement of the shift actuator is relatively small, the pressure in the second pressure circuit can also be adjusted dynamically during such a shift.

According to a preferred embodiment, the hydraulic system has a cooling circuit. The cooling circuit is supplied with hydraulic fluid, which is regulated by a pressure regulating valve. If the pressure regulating valve is in its initial position, the cooling circuit is not supplied from the second pressure circuit. The cooling circuit thus forms a secondary circuit which opens into the second pressure circuit.

Preferably, a second pressure regulating valve is provided for regulating the pressure in the first pressure circuit, in order to reduce the control effort of the first pump. The hydraulic fluid regulated by the second pressure regulating valve is preferably used to feed the cooling circuit.

Preferably, the first pressure circuit is assigned a second pressure control valve for controlling the actuating pressure of the first clutch of the dual clutch and a third pressure control valve for controlling the actuating pressure of the second clutch of the dual clutch. The second and third pressure control valves either directly control the actuation pressure of the dual clutch or are used to pre-control the respective actuation pressure. According to one possible embodiment, the output of the second pressure control valve is connected to the first pilot control interface of the second pressure regulating valve, and the output of the third pressure control valve is connected to the second pilot control interface of the second pressure regulating valve. Instead, a switching valve is provided, which is connected to the outputs of the second and third pressure control valves. The reversing valve is also connected with a pre-control interface of the second pressure regulating valve. Both variants make it possible to control the pressure in the first pressure circuit as a function of the actuation pressure of the dual clutch, wherein the higher actuation pressure specifies the pilot control pressure of the second pressure control valve. Thus, no separate pressure control valve is required for controlling the pressure in the first pressure circuit.

The first pressure circuit may be provided for hydraulically actuating the disconnect clutches of the dual clutch transmission. The disconnect clutch is functionally disposed between the input shaft of the dual clutch transmission and the dual clutches of the dual clutch transmission. The force transmission between the drive unit and the double clutch of the motor vehicle can thus be interrupted by means of the separating clutch. This is advantageous in particular for hybrid drive-train systems in which an electric machine is connected to the input side of the double clutch and can thus drive the motor vehicle. In order to control the actuation pressure of the separating clutch, the first pressure circuit can be assigned a fourth pressure control valve. The fourth pressure control valve either directly controls the actuation pressure of the dual clutch or serves to pre-control the actuation pressure. The separating clutch can therefore be actuated independently of the actuation of the double clutch.

The second pressure circuit may also be provided for hydraulically operating a central synchronizer of the dual clutch transmission. In contrast to conventional lockup synchronizers, the central synchronizer allows the rotational speed of the input shafts of the partial transmissions to be adapted independently of the actuation of the shift actuators of the dual clutch transmission. The central synchronizer can be realized, for example, by one or more switchable torque transmission paths between the hydraulically actuated input shafts.

Preferably, the parking lock is actuated by an actuating cylinder, wherein the supply of fluid to the actuating cylinder can be controlled by means of a parking lock valve. A piston guided in an actuating cylinder actuates a pawl of the parking lock, which interacts with a parking lock wheel of the parking lock. The piston is preloaded by a spring so that the pawl latches into the parking lock wheel by the spring force and the parking lock device is thus locked. By actuating the parking lock valve, hydraulic fluid is supplied to the operating cylinder, which hydraulic fluid counteracts the spring preload force and causes the parking lock to disengage. In this case, the supply connection of the parking lock valve is preferably connected to the first pressure circuit.

The first pump may preferably be driven by its own motor. The electric motor is independent of the drive of the motor vehicle and is used only for driving the first pump. The second pump is preferably driven by a drive unit of the motor vehicle drive train, i.e. for example by an internal combustion engine, and/or by an electric motor designed for driving the motor vehicle.

An electronic control unit may be provided, which is designed to control the hydraulic system, in particular to actuate the pressure control valve. The electronic control unit may be an integral part of a motor vehicle transmission.

The hydraulic system may be a component of the dual clutch transmission, such that elements of the hydraulic system are structurally integrated into the dual clutch transmission.

Drawings

Embodiments of the invention are explained in detail below with the aid of the figures. Wherein:

FIG. 1 shows a schematic diagram of a motor vehicle powertrain system having a dual clutch transmission; and

fig. 2 to 5 each show a circuit diagram of a different exemplary embodiment of a hydraulic system according to the invention.

Detailed Description

Fig. 1 shows a schematic representation of a motor vehicle drive train with a dual clutch transmission G with a hydraulic system HY. The motor vehicle transmission G has AN input shaft AN, which can be connected to a drive shaft GW1 via a disconnect clutch K0. The internal combustion engine VM is connected to the input shaft AN. The rotor of the electric machine EM2 is connected to the drive shaft GW 1. By closing the first clutch K1, the drive shaft GW1 can be connected to the first subtransmission TG 1. By closing the second clutch K2, the drive shaft GW1 can be connected to the second subtransmission TG 2. Each subtransmission TG1, TG2 is assigned a different transmission ratio stage i1, i2, i3, i4, which can be selectively connected to the output shaft GW2 by actuating hydraulic shift actuators SK1, SK 2. The output shaft GW2 is connected to a differential AG, which distributes the power present at the output shaft GW2 to the drive wheels DW of the motor vehicle drive train.

The first clutch K1 and the second clutch K2 form dual clutches of the dual clutch transmission G and are operated by hydraulic actuators AK1, AK2, respectively. The disconnect clutch K0 may be operated by a hydraulic actuator AK 0.

The dual clutch transmission G also has a central synchronizer ZSY. The central synchronizer comprises two switchable torque transmission paths which interconnect the input shafts of the two subtransmissions TG1, TG 2. Each of the torque transmission paths is associated with a synchronous transmission ratio iZ1, iZ2 and a clutch Z1, Z2. The two clutches Z1, Z2 can be actuated by means of hydraulic actuators AZ1, AZ 2.

The twin clutch transmission G has a parking lock device PS. The parking lock device PS includes a parking lock wheel PSR connected to a driven shaft GW 2. The parking lock wheel PSR has a toothing into which a pawl can latch. If the pawl latches into the tooth portion of the parking lock wheel PSR, the rotational movement of the driven shaft GW2 is prevented. The pawl is controlled by a hydraulic actuator APS.

The shift actuators SK1, SK2 and the actuators AK1, AK2, AK0, AZ1, AZ2, APS are operated by the hydraulic system HY. The pressure supply of the hydraulic system HY is effected by the first pump EP and the second pump MP. The first pump EP is driven by an electric motor EM1 which is assigned exclusively to the first pump EP. The second pump MP is driven by a drive shaft GW1, which is driven by the electric machine EM2 or by the internal combustion engine VM when the disconnect clutch K0 is closed. The two pumps EP, MP pump hydraulic fluid from a tank T of the hydraulic system HY and deliver it to a hydraulic control unit HCU which controls the oil supply to consumers of the hydraulic system HY. The twin-clutch transmission G has an electronic control unit ECU which is at least designed to control the hydraulic system HY. The temperature sensor TS measures the temperature of the hydraulic fluid in the tank T and transmits this information to the electronic control unit ECU.

The hydraulic control unit HCU is shown as a single component in fig. 1. This is to be regarded as exemplary only. The hydraulic control unit HCU may be structurally divided into a plurality of individual control units, which are connected to each other by suitable hydraulic interfaces.

The structure of the dual clutch transmission G shown in fig. 1 is to be regarded as exemplary only. The dual clutch transmission G can also be implemented without the electric machine EM2 and without the separating clutch K0, so that the internal combustion engine VM is permanently connected to the driveshaft GW 1. The subtransmissions TG1, TG2 may have more gear ratio steps than only four gear ratio steps i1, i2, i3, i 4. Other shift actuator units may be provided. In order to form one or more winding path gears, the two subtransmissions TG1, TG2 may be connected by one or more additional shifting clutches. The dual clutch transmission G can be constructed without a central synchronizer ZSY.

Fig. 2 shows a circuit diagram of the hydraulic system HY according to the first embodiment. The hydraulic system HY has a first pressure circuit H1 and a second pressure circuit H2. The supply of the first pressure circuit H1 can be effected by operating a first pump EP which delivers hydraulic fluid from the tank T through a filter FI1 and a filter FI2 to the pressure regulating valve SysD-V2. If the pressure regulating valve SysD-V2 is in its initial position, the first pump EP delivers fluid via the pressure regulating valve SysD-V2 through the holding valve SR-V2 into the first pressure circuit H1.

The first pressure circuit H1 is provided for hydraulically actuating the first and second clutches K1, K2 and the disconnect clutch K0. For this purpose, the first pressure circuit H1 is assigned a pressure control valve EDS1 for controlling the actuation pressure of the first clutch K1, a pressure control valve EDS2 for controlling the actuation pressure of the second clutch K2 and a pressure control valve EDS5 for controlling the actuation pressure of the separating clutch K0. The pressure control valve EDS1 serves to pilot-control a clutch valve KV1, which controllably connects the first pressure circuit H1 to the actuator AK 1. Likewise, the pressure control valve EDS2 is used to pre-control the clutch valve KV-2 for the actuator AK2, while the pressure control valve EDS5 is used to pre-control the clutch valve KV-0 for the actuator AK 0. The pre-control is only to be regarded as exemplary. The pressure control valves EDS1, EDS2, EDS5 may also directly control the respective actuators AK1, AK2, AK0, thereby eliminating the clutch valves KV-1, KV2, KV-0. The pressure sensor pk measures the actuating pressure of the respective actuated clutch K1, K2.

The pressure regulating valve SysD-V2 is pre-controlled via the outputs of the pressure control valves EDS1 and EDS2 by: the output of the pressure control valve EDS1 is connected to the first pilot interface of the pressure regulating valve SysD-V2, and the output of the pressure control valve EDS2 is connected to the second pilot interface of the pressure regulating valve SysD-V2. The control surfaces of the pressure control valve SysD-V2, which interact with the two pilot interfaces, are as large, so that the higher initial pressure level of the pressure control valves EDS1, EDS2 specifies the pilot control force for the pressure control valve SysD-V2. The volume flow regulated by the pressure regulating valve SysD-V2 is fed to the cooling circuit H3.

The energy supply for the electric motor EM1 driving the first pump EP is preferably carried out via a low-voltage circuit of the on-board electrical system of the motor vehicle. As a result, the first pump EP can also continue to be operated when the high-voltage supply of the on-board electrical system is insufficient. By operating the first pump EP, the separating clutch K0 can be closed, so that the internal combustion engine VM can drive the electric machine EM 2. The electric machine may be used as a generator to charge a high voltage circuit. Since the pilot control of the pressure regulating valve SysD-V2 is dependent on the actuation pressure of the actuators AK1, AK2, at least one of the actuators AK1, AK2 must be actuated in order to close the separating clutch K0.

The first pressure circuit H1 is also used to hold the parking lock device PS of the dual clutch transmission G in a disengaged state. The parking lock device PS is operated by means of an operating cylinder PS-Z constituting an actuator APS. The operating cylinders PS-Z have pistons. The piston is preloaded by a spring, wherein the spring force operates the piston in the closing direction of the parking lock PS. The steering cylinders PS-Z are connected to a first pressure circuit H1 via parking lock valves PS-V. If the pressure on the piston of the operating cylinder PS-Z caused by the pressure in the first pressure circuit H1 exceeds the spring force, the piston is operated in the opening direction of the parking lock device PS.

The second pressure circuit H2 is supplied by a second pump MP, which in the exemplary embodiment according to fig. 1 is designed as a double-circuit pump having two pump circuits (Pumpenfluten). The two pump lines of the second pump MP draw hydraulic fluid from the tank T through the filter FI 3. One of the two pump lines is permanently connected to a pressure regulating valve SysD-V1. If the pressure regulating valve SysD-V1 is in its initial position, the second pump MP delivers fluid through at least one pump line via the pressure regulating valve SysD-V1 through the holding valve SR-V1 and the filter FI4 into the second pressure circuit H2. The volume flow regulated by the pressure regulating valve SysD-V1 is fed to the cooling circuit H3.

The pressure regulating valve SysD-V1 is pre-controlled by means of the pressure control valve EDS3, wherein the supply connection of the pressure control valve EDS3 is connected directly to the pump line of the second pump MP, which is permanently connected to the pressure regulating valve SysD-V1. The output of the pressure control valve EDS3 is connected to a control surface of the pressure regulating valve SysD-V1 and also to a control surface of the switching valve P-V for the pilot control of the pressure regulating valve SysD-V1. The switching valve P-V is preloaded by means of a spring. If the spring force is greater than the pressure acting on the control surface of the switching valve P-V, the switching valve P-V connects the pump line, which is not permanently connected to the pressure regulating valve SyD-V1, to the suction connection of the second pump MP. If the pressure acting on the control surface of the switching valve P-V is greater than the spring force, the switching valve P-V blocks the connection between the pump line and the suction connection of the second pump MP. Whereby the check valve S-V, which interconnects the two pump lines of the second pump MP, opens.

The second pressure circuit H2 is equipped with shift actuators SK1, SK2 and actuators AZ1, AZ2 as consumers. The hydraulic fluid supply to the actuator AZ1 may be directly controlled by the pressure control valve EDS 6. The hydraulic fluid supply to the actuator AZ2 may be directly controlled by the pressure control valve EDS 7. Instead, the hydraulic fluid supply to the actuators AZ1, AZ2 may be designed to be pre-controlled. In order to prevent idle rotation of the actuators AZ1, AZ2, the common tank line of the actuators AZ1, AZ2 is provided with a prefill valve VB-Z, which is configured as a spring-loaded check valve.

The hydraulic fluid supply to the shift actuator SK1 may be directly controlled by the pressure control valve EDS 8. The hydraulic fluid supply to the shift actuator SK2 may be directly controlled by the pressure control valve EDS 9. The pressure control valves EDS8, EDS9 are configured as spring-loaded four-way valves. In the state in which the pressure control valves EDS8, EDS9 are not actuated, the shift actuators SK1, SK2 are hydraulically blocked by means of the pressure control valves EDS8, EDS 9.

The hydraulic fluid supply from the second pressure circuit H2 to the supply connections of the pressure control valves EDS8, EDS9 can be shut off by a shut-off valve Sp-V. The stop valve Sp-V is preloaded in the stop position by a spring, so that the fluid line between the second pressure circuit H2 and the supply connections of the pressure control valves EDS8, EDS9 is blocked. In order to switch the stop valve Sp-V into its open position, the pressure on the control surface of the stop valve Sp-V must overcome the spring force. The control surface of the stop valve Sp-V can be pressure-controlled by the pressure control valve EDS 4. The supply connection of the pressure control valve EDS4 is connected to the first pressure circuit H1.

The cooling circuit H3 is provided with a heat exchanger KU for cooling the hydraulic fluid. The volume flow regulated by the pressure regulating valve SysD-V1 flows through the heat exchanger KU. If the stagnation pressure of the heat exchanger KU becomes too great, the cooler protection valve BP-V opens a bypass line through which the volume flow regulated by the pressure regulating valve SySD-V1 can bypass the heat exchanger KU. The volume flow regulated by the pressure regulating valve SysD-V2 is fed to the cooling circuit H3 downstream of the heat exchanger KU.

The lubricating oil circuit, not shown, of the dual clutch transmission G is also supplied with a volume flow via the cooling circuit H3. A cooling oil line is supplied via path C-EM, which supplies cooling oil to the stator of the electric machine EM 2. The cooling circuit H3 is also connected to the cooling oil valve C-V. The cooling oil valve C-V is preloaded by a spring. In the non-actuated, spring-preloaded state, the cooling oil valve C-V connects the cooling circuit H3 with the suction interface of the second pump MP. The cooling oil valves C-V are designed to connect the cooling circuit H3 to a cooling oil line, via which the first and second clutches K1, K2 and the separating clutch K0 can be supplied with cooling oil. In order to connect the cooling circuit H3 to the cooling oil line to the clutches K1, K2, K0 via the cooling oil valve C-V, the pressure on the control surface of the cooling oil valve C-V must overcome the spring force. The control surfaces of the cooling oil valves C-V can be pressure-controlled by a pressure control valve EDS 4. If the pressure on the control surface of the coolant valve C-V exceeds the spring preload force, the connection between the cooling circuit H3 and the suction connection of the second pump MP is interrupted and the connection between the cooling circuit H3 and the coolant line to the clutches K1, K2, K0 is released.

By actuating the pressure control valve EDS4 for the pilot control of the coolant valves C-V, the coolant supply to the clutches K1, K2, K0 can be controlled as required. Since at least the clutches K1, K2 serve as starting elements of the drive-train of the motor vehicle, cooling is required anyway, for example during a start of the motor vehicle in a slope. However, the supply of cooling oil to clutches K0, K1, K2 increases the drag losses thereof, so that the supply of cooling oil is undesirable when clutches K0, K1, K2 are subjected to little or no thermal load. In particular, if the hydraulic fluid is cold, the supply of cooling oil to the clutches K1, K2 may increase the drag torque of the input shafts of the subtransmissions TG1, TG2 in such a way that a reliable engagement of the gears by means of the shift actuators SK1, SK2 is no longer ensured. Since the supply connection of the pressure control valve EDS4 is connected to the first pressure circuit H1 and since the cooling oil line to the clutches K0, K1, K2 can be supplied from the volume flow regulated by the pressure control valves SysD-V1, SysD-V2, a reliable, on-demand control of the cooling oil supply to the clutches K1, K2 is ensured in all operating points of the dual clutch transmission G.

The volume flow present at the pressure regulating valve SysD-V1 is dependent on the switching state of the switching valve P-V. If the switching valve P-V connects the pump line, which is not permanently connected to the pressure regulating valve SysD-V1, to the suction connection of the second pump MP, said pump line feeds directly into the suction load of the second pump MP. The drive power required for operating the second pump MP can thus be kept low. If the switching valve P-V blocks the connection between the pump line and the suction connection of the second pump MP, the volume flows of the two pump lines of the second pump MP reach the pressure regulating valve SysD-V1. The switching state of the switching valve P-V is dependent on the pressure in the second pressure circuit H2, since the control surface of the switching valve P-V is connected to the control surface of the pressure regulating valve SysD-V1. Thus, the volume flow available to supply the cooling circuit H3 may be controlled by controlling the pressure in the second pressure circuit H2.

When the volume flow demand of one or more of the actuators AK1, AK2, AK0 is high, the pressure in the second pressure circuit H2 can be increased by actuating the pressure control valve EDS3 accordingly. If the pressure in the second pressure circuit H2 exceeds the pressure in the first pressure circuit H1 by a defined limit value, the differential pressure valve F-V opens a direct connection between the two pressure circuits H1, H2, so that the first pressure circuit H1 is supplied by the second pump MP, proceeding from the second pressure circuit H2. The differential pressure valve F-V is configured as a spring-loaded check valve. The limit value of the differential pressure for opening the differential pressure valve F-V is therefore dependent on the spring preload force F-V of the differential pressure valve.

Fig. 3 shows a circuit diagram of a hydraulic system HY according to a second exemplary embodiment, which substantially corresponds to the first exemplary embodiment shown in fig. 2. The supply connection of the pressure control valve EDS3 is now no longer connected to the pump line of the second pump MP, which is permanently connected to the pressure regulating valve SysD-V1. Instead, the supply connection of the pressure control valve EDS3 is now connected to the first pressure circuit H1.

Fig. 4 shows a circuit diagram of a hydraulic system HY according to a third embodiment, which hydraulic system substantially corresponds to the second embodiment shown in fig. 3. Furthermore, the pressure control valve SysD-V2 is pre-controlled therein via the outputs of the pressure control valves EDS1, EDS2, wherein the pressure control valve SysD-V2 has only one pre-control interface. Instead of connecting the outputs of the two pressure control valves EDS1, EDS2 to a pilot control interface on the pressure regulating valve SysD-V2, a changeover valve KW-V is now provided. The switching valve KW-V connects the pilot control connection of the pressure control valve SysD-V2 to the outputs of the pressure control valves EDS1, EDS2, which have a higher pressure.

Fig. 5 shows a circuit diagram of a hydraulic system HY according to a fourth embodiment, which hydraulic system substantially corresponds to the second embodiment shown in fig. 3. The second pump MP is now implemented as a single-circuit pump, the pressure side of which is connected to the pressure regulating valve SysD-V1. The switching valve P-V is correspondingly eliminated.

The hydraulic system HY is controlled by an electronic control unit ECU in the following mode: the electronic control unit controls the supply of current to the pressure control valves EDS1, EDS2, EDS3, EDS4, EDS5, EDS6, EDS7, EDS8 in accordance with signals from the pressure sensor pK, the temperature sensor TS, and, if necessary, other sensors. The electronic control unit ECU may also receive signals from other control units and use these signals to control the hydraulic system HY.

List of reference numerals

G double clutch transmission

AN input shaft

VM internal combustion engine

GW1 drive shaft

K0 disconnect clutch

AK0 actuator

EM2 motor

K1 first clutch

K2 second clutch

AK1 actuator

AK2 actuator

TG1 first-branch transmission

TG2 second branch transmission

i1, i2, i3, i4 ratio steps

SK1 gearshift actuator

SK2 gearshift actuator

GW2 driven shaft

AG differential mechanism

DW driving wheel

ZSY Central synchronizer

iZ1, iZ2 synchronous ratio

Z1, Z2 clutch

AZ1, AZ2 actuator

PS parking lock device

PSR parking locking wheel

PSA actuator

HCU hydraulic control unit

ECU electronic control unit

HY hydraulic system

H1 first pressure circuit

H2 second pressure loop

H3 cooling circuit

EP first pump

EM1 motor

MP second pump

T-shaped oil tank

TS temperature sensor

pk pressure sensor

FI1-FI4 filter

SysD-V1 pressure regulating valve

SysD-V2 pressure regulating valve

EDS1 pressure control valve

EDS2 pressure control valve

EDS3 pressure control valve

EDS4 pressure control valve

EDS5 pressure control valve

EDS6 pressure control valve

EDS7 pressure control valve

EDS8 pressure control valve

SR-V1 holding valve

SR-V2 holding valve

KV-1 clutch valve

KV-2 clutch valve

KV-0 clutch valve

PS-Z operating cylinder

PS-V parking locking valve

P-V switching valve

S-V check valve

F-V differential pressure valve

Sp-V stop valve

KU heat exchanger

BP-V cooler protection valve

C-EM cooling oil path

C-V cooling oil valve

KW-V change valve

Claims

1. A hydraulic system (HY) for a dual clutch transmission (G) of a motor vehicle drive train, wherein the hydraulic system (HY) has a first pump (EP) for pressure supply of a first pressure circuit (H1) and a second pump (MP) for pressure supply of a second pressure circuit (H2),

wherein the first pressure circuit (H1) is provided at least for hydraulically actuating the dual clutch (K1, K2) and for hydraulically actuating a parking lock (PS) of the dual clutch transmission (G),

characterized in that the second pressure circuit (H2) is provided at least with shift actuators (SK1, SK2) for hydraulically actuating the dual clutch transmission (G).

2. Hydraulic system (HY) according to claim 1 characterized in that the first pressure circuit (H1) and the second pressure circuit (H2) are connected to each other by means of differential pressure valves (F-V) so that a volume flow from the second pressure circuit (H2) into the first pressure circuit (H1) can be achieved.

3. The hydraulic system (HY) according to claim 1 or claim 2 characterized in that a pressure regulating valve (SysD-V1) is provided for regulating the pressure in the second pressure circuit (H2), where the pressure regulating valve (SysD-V1) is pre-controlled by a pressure control valve (EDS3),

wherein the pressure in the second pressure circuit (H2) can be adjusted to a value which is higher than the pressure in the first pressure circuit (H1) by actuating the pressure control valve (EDS3), so that the first pressure circuit (H1) can be supplied with hydraulic fluid by means of the second pump (MP) by automatic opening of the differential pressure valve (F-V).

4. The hydraulic system (HY) of claim 3 wherein the supply interface of the pressure control valve (EDS3) is connected with the first pressure circuit (H1).

5. The hydraulic system (HY) of claim 3 wherein the supply interface of the pressure control valve (EDS3) is connected with the pressure side of the second pump (MP).

6. The hydraulic system (HY) according to any one of claims 3 to 5 characterized by that it has a cooling circuit (H3) where the cooling circuit (H3) can be supplied with hydraulic fluid regulated by pressure regulating valve (SysD-V1).

7. The hydraulic system (HY) according to any of claims 3-6 characterized by the fact that a second pressure regulating valve (SysD-V2) is provided for regulating the pressure in the first pressure circuit (H1).

8. The hydraulic system (HY) according to claims 6 and 7 where the cooling circuit (H3) can be supplied by hydraulic fluid regulated by a second pressure regulating valve (SysD-V2).

9. The hydraulic system (HY) according to claim 7 or claim 8, characterized in that the first pressure circuit (H1) is assigned a second pressure control valve (EDS1) for controlling the actuation pressure of the first clutch (K1) of the dual clutch (K1, K2) and a third pressure control valve (EDS2) for controlling the actuation pressure of the second clutch (K2) of the dual clutch (K1, K2), wherein the output of the second pressure control valve (EDS1) is connected to the first pilot control connection of the second pressure regulating valve (SysD-V2) and the output of the third pressure control valve (EDS2) is connected to the second pilot control connection of the second pressure regulating valve (SysD-V2).

10. The hydraulic system (HY) as claimed in claim 7 or claim 8, characterized in that the first pressure circuit (H1) is provided with a second pressure control valve (EDS1) for controlling the actuation pressure of the first clutch (K1) of the dual clutch (K1, K2) and a third pressure control valve (EDS2) for controlling the actuation pressure of the second clutch (K2) of the dual clutch (K1, K2),

wherein the output of the second pressure control valve (EDS1) and the output of the third pressure control valve (EDS2) are connected to a directional control valve (KW-V) which is connected to a pilot control connection of the second pressure control valve (SysD-V2), so that the higher output pressure of the second pressure control valve (EDS1) and the third pressure control valve (EDS2) specifies the pilot control pressure of the second pressure control valve (SysD-V2).

11. The hydraulic system (HY) according to one of the preceding claims, characterized in that the first pressure circuit (H1) is also provided with a separating clutch (K0) for hydraulically actuating the dual clutch transmission (G), wherein the separating clutch (K0) is functionally arranged between the input shaft (AN) of the dual clutch transmission (G) and the dual clutches (K1, K2), wherein the first pressure circuit (H1) is assigned a fourth pressure control valve (EDS5) for controlling the actuating pressure of the separating clutch (K0).

12. The hydraulic system (HY) as claimed above, characterized in that the second pressure circuit (H2) is also provided for hydraulically operating the central synchronizer (ZSY) of a dual clutch transmission (G).

13. The hydraulic system (HY) according to any one of the preceding claims characterized in that fluid supply to the operating cylinders (PSZ) of the parking lock devices (PS) of a dual clutch transmission (G) can be controlled by means of parking lock valves (PS-V) whose supply interfaces are connected to the first pressure circuit (H1).

14. Hydraulic system (HY) according to any of the preceding claims characterized in that the first pump (EP) can be driven by an electric motor (EM1) assigned only to the first pump (EP), which is not designed for driving a motor vehicle, wherein the second pump (MP) can be driven by a drive unit (VM, EM2) of a motor vehicle drive train.

15. A twin-clutch transmission (G) for a motor vehicle, characterized in that it has a hydraulic system (HY) according to any one of claims 1 to 14.