Sensor arrangement for a hydraulic system of a gearbox

Abstract

Sensor arrangement (SA) for a hydraulic system (HY) of a transmission (G), comprising a sensor (pK) for determining a pressure in the hydraulic system (HY), wherein a changeover valve (pK-V) with at least a first position and a second position is provided, wherein the sensor (pK) in the first position of the changeover valve (pK-V) is connected to a first pressure measuring point (pK1, pK11) and in the second position of the changeover valve (pK-V) to a second pressure measuring point (pK2, pK21), characterized in that the first pressure measuring point (pK1, pK11) detects an actuation pressure of a first clutch (K1) of the transmission (G), and the second pressure measuring point (pK2, pK21) detects an actuation pressure of a second clutch (K2) of the transmission (G).

Description

[0001] The invention relates to a sensor arrangement for a hydraulic system of a transmission, and to a hydraulic system with such a sensor arrangement for a transmission of a motor vehicle powertrain. The invention further relates to a hydraulic control unit for such a transmission, and to a transmission for a motor vehicle with such a hydraulic system or such a hydraulic control unit.

[0002] Patent DE 10 2016 214 375 B3 describes a hydraulic system for an automatic transmission of a motor vehicle, in particular for a dual-clutch transmission. An electronic control unit is provided for controlling the dual-clutch transmission, to which two pressure sensors are assigned. The pressure sensors detect the hydraulic pressure applied to the clutch hydraulic cylinders of the dual clutch.

[0003] WO 2018 / 055 197 A1 describes a hydraulic unit for adjusting a vehicle flap of a land, water or air vehicle using at least two linear cylinders, each of which has at least two retaining clips that can be filled with hydraulic fluid such as gear oil.

[0004] WO 2018 / 192 989 A1 discloses a vehicle transmission and a hydraulic system for a vehicle transmission. The vehicle transmission comprises at least two friction elements.

[0005] In EP 3 134 664 B1, a hydraulic system of a transmission device is connected with a hydraulic pump driven via a transmission input shaft and with another hydraulic pump driven via a transmission shaft, and directs hydraulic fluid volume conveyed by the hydraulic pumps to transmission components.

[0006] However, such pressure sensors are very expensive. Apart from the pressure sensors themselves, the electrical contacting and connection of the pressure sensors to an electronic control unit must also be taken into account.

[0007] It is therefore an object of the invention to provide a sensor arrangement for a transmission hydraulics system by means of which the number of pressure sensors can be reduced.

[0008] The problem is solved by the features of claim 1. Advantageous embodiments are shown in the dependent claims, the description and the figures.

[0009] To solve this problem, a sensor arrangement for a transmission's hydraulic system is proposed, which includes a sensor for determining the pressure in the hydraulic system. According to the invention, a changeover valve with at least a first position and a second position is provided. In the first position of the changeover valve, the sensor is connected to a first pressure measuring point. In the second position of the changeover valve, the sensor is connected to a second pressure measuring point. This design makes it possible to determine the pressure at two different measuring points in the hydraulic system with only a single pressure sensor. The additionally required changeover valve incurs lower costs than a separate pressure sensor would otherwise be necessary. This reduces the manufacturing effort of the hydraulic system.

[0010] Preferably, the changeover valve is designed as a spool valve. The spool valve is configured such that, in the first position of the changeover valve, the sensor is hydraulically isolated from the second pressure measuring point, and vice versa. In other words, the changeover valve is preferably designed as a spool valve with overlap. This easily prevents incorrect pressure measurements.

[0011] Preferably, the changeover valve is spring-loaded in the first position and can be actuated electromagnetically or hydraulically. This ensures a safe operating state of the changeover valve should its control system malfunction.

[0012] In a hydraulically piloted changeover valve design, a pressure control valve is preferably provided, the output of which is connected to a control surface of the changeover valve. The pressure control valve is preferably directly actuated electromagnetically, with a supply port of the pressure control valve preferably connected to a pressure circuit of the hydraulic system.

[0013] The first pressure sensor is designed to detect the actuation pressure of the first clutch in the transmission, and the second pressure sensor is designed to detect the actuation pressure of the second clutch in the transmission. For example, in a dual-clutch transmission, knowing the actuation pressures of the dual clutches is advantageous for their control. The sensor arrangement is therefore particularly suitable for detecting different clutch actuation pressures.

[0014] Preferably, the first coupling is actuated by a hydraulic actuator with a first pressure port, and the second coupling by a second hydraulic actuator with a second pressure port. Pressure at the first pressure port is controlled by a first coupling valve, and pressure at the second pressure port is controlled by a second coupling valve. The first and second coupling valves can be directly electromagnetically actuated or hydraulically pilot-operated. A first orifice is arranged between the first coupling valve and the first pressure port, and a second orifice is arranged between the second coupling valve and the second pressure port.

[0015] Preferably, the first pressure measuring point is located between the first orifice and the first pressure port, and the second pressure measuring point is located between the second orifice and the second pressure port. This arrangement allows the actuation pressure of the couplings to be measured directly.

[0016] According to an alternative embodiment, the first pressure measuring point can be arranged between the first coupling valve and the first orifice, and the second pressure measuring point between the second coupling valve and the second orifice. With such a configuration, the measured pressure may deviate from the actuating pressure of the couplings, particularly in the case of a flow-dependent pressure drop across the first orifice or the second orifice. Knowing the expected pressure drop, this arrangement of pressure measuring points allows the condition of the hydraulic connection between the first / second coupling valve and the first / second pressure port to be detected.

[0017] The sensor arrangement can be part of a hydraulic system for a transmission in a motor vehicle powertrain. If the changeover valve is hydraulically piloted, the pilot pressure for the changeover valve is preferably a pressure signal that also serves to pilot at least one other valve in the hydraulic system. Such multiple use of the pressure signal allows the number of valves in the hydraulic system to be kept to a minimum. Preferably, the at least one other valve serves to control the supply of cooling oil to the first and second clutches, for example, as a cooling oil valve.

[0018] The cooling oil valve can have a first, a second, and a third switching position. In the first and third switching positions, the cooling oil valve shuts off the cooling oil supply to the first and second clutches, while in the second switching position, the cooling oil valve opens the cooling oil supply to the first and second clutches. This design of the cooling oil valve allows the cooling oil supply to be controlled independently of the position of the changeover valve.

[0019] The hydraulic system can be part of a hydraulic control unit for a transmission in a motor vehicle powertrain. The hydraulic system, or the hydraulic control unit with the hydraulic system, can be part of a motor vehicle transmission, in particular a dual-clutch transmission, an automatic transmission, or an automated transmission.

[0020] Exemplary embodiments of the invention are described in detail below with reference to the accompanying figures. These show: Fig. 1 a schematic representation of a motor vehicle powertrain with a dual-clutch transmission; Fig. 2 a circuit diagram of a hydraulic system; Fig. 3 a section of the circuit diagram according to Fig. 2 with modified pressure measuring points; Fig. 4 a distribution characteristic of a cooling oil valve of the hydraulic system; as well as Fig. 5 a further section of the circuit diagram according to Fig. 2.

[0021] Fig. Figure 1 shows a schematic representation of a motor vehicle powertrain with a dual-clutch transmission G, which incorporates 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. An internal combustion engine VM is connected to the input shaft AN. A rotor of an electric machine EM2 is connected to the drive shaft GW1. By engaging a first clutch K1, the drive shaft GW1 can be connected to a first sub-transmission TG1. By engaging a second clutch K2, the drive shaft GW1 can be connected to a second sub-transmission TG2. Each of the sub-transmissions TG1 and TG2 is assigned different gear ratios i1, i2, i3, and i4, which can be selectively connected to an output shaft GW2 by actuating a hydraulic switching actuator SK1 and SK2.The output shaft GW2 is connected to a differential gear AG, which distributes the power applied to the output shaft GW2 to the drive wheels DW of the vehicle drivetrain.

[0022] The first clutch K1 and the second clutch K2 form the dual clutch of the dual-clutch transmission G, and are each actuated by hydraulic actuators AK1 and AK2, respectively. The disconnect clutch K0 is actuated by a hydraulic actuator AK0.

[0023] The dual-clutch transmission G also features a central synchronizer ZSY. This comprises two switchable torque transmission paths that connect the input shafts of the two sub-transmissions TG1 and TG2. Each torque transmission path is assigned a synchronizer ratio iZ1 and iZ2, and a clutch Z1 and Z2. The two clutches Z1 and Z2 are actuated by hydraulic actuators AZ1 and AZ2.

[0024] The dual-clutch transmission G features a parking lock PS. The parking lock PS comprises a parking lock gear PSR, which is connected to the output shaft GW2. The parking lock gear PSR has teeth into which a pawl can engage. When the pawl engages the teeth of the parking lock gear PSR, the rotation of the output shaft GW2 is inhibited. The pawl is controlled by a hydraulic actuator APS.

[0025] The switching actuators SK1 and SK2, as well as the actuators AK1, AK2, AK0, AZ1, AZ2, and APS, are actuated by the hydraulic system HY. The hydraulic system HY is supplied with pressure by a pump EP and a pump MP. The second pump MP forms a pressure supply unit, which in this example is configured as a dual-circuit pump. The pump EP is driven by an electric motor EM1 dedicated exclusively to it. The pressure supply unit MP is driven by the drive shaft GW1, which is driven by the electric motor EM2, or, when the disconnect clutch K0 is closed, by the internal combustion engine VM. The pump EP and the pressure supply unit MP draw hydraulic fluid from a tank T of the hydraulic system HY and deliver the hydraulic fluid to a hydraulic control unit HCU, which controls the oil supply to the consumers of the hydraulic system HY.The dual-clutch transmission G has an electronic control unit (ECU) which is configured to control at least the hydraulic system (HY). A temperature sensor (TS) measures the temperature of the hydraulic fluid in the tank (T) and transmits this information to the electronic control unit (ECU).

[0026] The hydraulic control unit HCU is in Fig. Figure 1 is shown as a single assembly. This is merely an example. The hydraulic control unit (HCU) can be structurally divided into several individual control units, which are connected to each other via suitable hydraulic interfaces.

[0027] The structure of the Fig. The dual-clutch transmission G shown in Figure 1 is only an example. The dual-clutch transmission G could also be designed without the electric motor EM2 and without the disconnect clutch K0, so that the internal combustion engine VM is permanently connected to the drive shaft GW1. The sub-transmissions TG1 and TG2 could have more than four gear ratios i1, i2, i3, and i4. Additional shift-actuator units could be provided. To form one or more turns, the two sub-transmissions TG1 and TG2 could be connected via one or more additional shift clutches. The dual-clutch transmission G could be designed without the central synchronizer ZSY.

[0028] Fig. Figure 2 shows a circuit diagram of the hydraulic system HY according to a first embodiment. The hydraulic system HY has a pressure circuit H1 and a pressure circuit H2. The pressure circuit H1 can be supplied by operating the pump EP, which delivers hydraulic fluid from the tank T through a filter FI1 and a filter FI2 to a pressure control valve SysD-V2. When the pressure control valve SysD-V2 is in its initial position, the pump EP delivers the fluid via the pressure control valve SysD-V2 and through a check valve SR-V2 into the pressure circuit H1.

[0029] Pressure circuit H1 is designed for the hydraulic actuation of the first and second clutches K1 and K2, as well as the disconnect clutch K0. For this purpose, pressure circuit H1 includes 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 disconnect clutch K0. Pressure control valve EDS1 provides pilot control for a clutch valve KV-1, which connects pressure circuit H1 to actuator AK1. Similarly, pressure control valve EDS2 provides pilot control for a clutch valve KV-2 for actuator AK2, and pressure control valve EDS5 provides pilot control for a clutch valve KV-0 for actuator AK0. This pilot control is shown only as an example.The pressure control valves EDS1, EDS2, and EDS5 could also directly control the respective actuators AK1, AK2, and AK0, thus eliminating the need for the coupling valves KV-1, KV2, and KV-0. A pressure sensor pK measures the actuation pressure of the respective actuated coupling K1 and K2.

[0030] A sensor arrangement SA is provided for pressure sensing the actuation pressure of the clutches K1 and K2. The sensor arrangement SA comprises the pressure sensor pK and a changeover valve pK-V, designed as a slide valve, which can assume a first position and a second position. In the Fig. In the first position shown in Figure 2, the changeover valve pK-V connects a hydraulic line connected to actuator AK1 to pressure sensor pK, and blocks a connection between a hydraulic line connected to actuator AK2 and pressure sensor pK. The changeover valve pK-V is pre-tensioned in the first position by a spring pK-VF and can be moved to the second position by applying an external force against the force of the spring pK-VF. In the exemplary embodiment according to Fig. 2. The changeover valve pK-V is hydraulically pilot-operated, so that the external force is applied by pressurizing a control surface of the changeover valve pK-V. Alternatively, the external force could be applied by an electromagnet, which directly actuates the spool of the changeover valve pK-V.

[0031] In the exemplary embodiment according to Fig. 2. The pressure sensing of the actuation pressure of actuator AK1 takes place at a pressure measuring point pK1, and the pressure sensing of the actuation pressure of actuator AK2 takes place at a pressure measuring point pK2. The pressure measuring point pK1 is located between an orifice plate KV-1B and a pressure port AK1_p of actuator AK1. The pressure measuring point pK2 is located between an orifice plate KV-2B and a pressure port AK2_p of actuator AK2. The orifice plates KV-1B and KV-2B are located between the respective coupling valves KV-1 and KV2 and the pressure ports AK1_p and AK2_p, respectively.

[0032] The pressure control valve SysD-V2 is pilot-operated via the outputs of the pressure control valves EDS1 and EDS2. The output of pressure control valve EDS1 is connected to a first pilot port of the pressure control valve SysD-V2, and the output of pressure control valve EDS2 is connected to a second pilot port of the pressure control valve SysD-V2. The control surfaces of the pressure control valve SysD-V2 interacting with the two pilot ports are of the same size, so the higher output pressure level of the pressure control valves EDS1 and EDS2 determines the pilot force for the pressure control valve SysD-V2. The flow rate regulated by the pressure control valve SysD-V2 is fed to a cooling circuit H3.

[0033] The electric motor EM1, which drives the pump EP, is preferably powered by a low-voltage circuit of the vehicle's electrical system. This allows the pump EP to continue operating even if a high-voltage circuit of the electrical system is under-supplied. Operating the pump EP allows the disconnect clutch K0 to close, enabling the internal combustion engine VM to drive the electric machine EM2. This machine can then act as a generator to charge the high-voltage circuit. Since the pilot control of the pressure regulating valve SysD-V2 depends on the actuation pressure of the actuators AK1 and AK2, at least one of these actuators must be actuated to close the disconnect clutch K0.

[0034] Pressure circuit H1 also serves to hold the parking lock PS of the dual-clutch transmission G in the disengaged state. The parking lock PS is actuated by an actuating cylinder PS-Z, which forms the actuator APS. The actuating cylinder PS-Z has a piston. The piston is pre-tensioned by a spring, with the spring force actuating the piston in the closing direction of the parking lock PS. The actuating cylinder PS-Z is connected to pressure circuit H1 via a switching valve PS-V. If the pressure force on the piston of the actuating cylinder PS-Z, caused by the pressure in pressure circuit H1, exceeds the force of the spring, the piston is actuated in the opening direction of the parking lock PS.

[0035] The pressure circuit H2 is supplied by the pressure supply unit MP, which in the exemplary embodiment according to Fig. Figure 1 is an example of a dual-circuit pump with a first outlet line MP1 and a second outlet line MP2. Both outlet lines MP1 and MP2 of the pressure supply unit MP draw hydraulic fluid from tank T through a filter FI3. The first outlet line MP1 is constantly connected to a pressure regulating valve SysD-V1. When the pressure regulating valve SysD-V1 is in its initial position, the pressure supply unit MP delivers the fluid, at least via the first outlet line MP1, through the pressure regulating valve SysD-V1, a check valve SR-V1, and a filter FI4 into the pressure circuit H2. The flow rate regulated by the pressure regulating valve SysD-V1 is fed to the cooling circuit H3.

[0036] The pressure regulating valve SysD-V1 is pilot-operated by a pressure control valve EDS3, with one supply port of the pressure control valve EDS3 being directly connected to the first output line MP1 of the pressure supply unit MP. An 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 a switching valve PV for pilot operation of the pressure regulating valve SysD-V1. The switching valve PV is biased by a spring P-VF and has at least a first switching position and a second switching position. If the force of the spring P-VF is greater than the pressure force acting on the control surface of the switching valve PV, the switching valve PV assumes its first switching position, in which the switching valve PV connects the second output line MP2 of the pressure supply unit MP to a suction port MP_in of the pressure supply unit MP.If the pressure force acting on the control surface of the switching valve PV is greater than the force of the spring P-VF, the switching valve PV assumes its second switching position, in which it closes the connection between the second output line MP2 and the suction port MP_in of the pressure supply unit MP. The resulting back pressure in the second output line MP2 opens another valve SV, which connects the two output lines MP1 and MP2 of the pressure supply unit MP. This second valve SV is designed as a poppet valve.

[0037] The switching valve PV has a second control surface which is connected to a regulating line of the pressure control valve SysD-V1. A pressure force acting on the second control surface of the switching valve PV acts in the same direction as the spring, so that an increasing pressure in the regulating line opposes the switching valve PV switching to its second switching position.

[0038] The pressure circuit H2 is supplied with the switching actuators SK1 and SK2, and the actuators AZ1 and AZ2. The hydraulic fluid supply to actuator AZ1 is directly controlled by a pressure control valve EDS6. The hydraulic fluid supply to actuator AZ2 is directly controlled by a pressure control valve EDS7. Alternatively, the hydraulic fluid supply to actuators AZ1 and AZ2 could be pilot-operated. To prevent actuators AZ1 and AZ2 from running dry, a common reservoir line for both actuators is equipped with a pre-filling valve VB-Z, which is designed as a spring-loaded check valve.

[0039] The hydraulic fluid supply to the switching actuator SK1 is directly controlled by a pressure control valve EDS8. The hydraulic fluid supply to the switching actuator SK2 is directly controlled by a pressure control valve EDS9. The pressure control valves EDS8 and EDS9 are designed as spring-loaded 4 / 4-way valves. When the pressure control valves EDS8 and EDS9 are not actuated, the switching actuators SK1 and SK2 are hydraulically locked by means of the pressure control valves EDS8 and EDS9.

[0040] The hydraulic fluid supply to the supply ports of the pressure control valves EDS8 and EDS9, originating from pressure circuit H2, can be shut off by a check valve Sp-V. The check valve Sp-V is spring-loaded in the closed position, thus blocking the fluid line between pressure circuit H2 and the supply ports of the pressure control valves EDS8 and EDS9. To open the check valve Sp-V, the pressure force at a control surface of the check valve Sp-V must overcome the spring force. The control surface of the check valve Sp-V can be pressurized by a pressure control valve EDS4. One supply port of the pressure control valve EDS4 is connected to pressure circuit H1.

[0041] Cooling circuit H3 is connected to a heat exchanger KU for cooling the hydraulic fluid. The flow rate, regulated by the pressure control valve SysD-V1, flows through the heat exchanger KU. If the back pressure of the heat exchanger KU becomes too high, a radiator protection valve BP-V opens a bypass line, allowing the flow rate regulated by the pressure control valve SysD-V1 to bypass the heat exchanger KU. The flow rate regulated by the pressure control valve SysD-V2 is fed into cooling circuit H3 downstream of the heat exchanger KU.

[0042] Cooling circuit H3 also supplies a lubricating oil circuit (not shown) of the dual-clutch transmission G with flow. A cooling oil line, supplied via path C-EM, provides cooling oil to a stator of the electric machine EM2. Cooling circuit H3 is also connected to a cooling oil valve CV. The cooling oil valve CV is spring-loaded. In its unactuated, spring-loaded state, the cooling oil valve CV connects cooling circuit H3 to the suction port MP_in of the pressure supply unit MP. The cooling oil valve CV is configured to connect cooling circuit H3 to a cooling oil line C-V_Kout, through which the first and second clutches K1, K2, and the disconnect clutch K0 can be supplied with cooling oil. In order to connect cooling circuit H3 via the cooling oil valve CV to the cooling oil line C-V_Kout leading to the clutches K1, K2, K0, the pressure force at a control surface of the cooling oil valve CV must overcome the spring force.The control surface of the cooling oil valve CV can be pressurized by the pressure control valve EDS4. If the pressure force on the control surface of the cooling oil valve CV exceeds the spring preload, the connection between cooling circuit H3 and the suction port MP_in of the pressure supply unit MP is interrupted, and the connection between cooling circuit H3 and the cooling oil line C-V_Kout to the couplings K1, K2, K0 is opened. If the pressure force on the control surface of the cooling oil valve CV exceeds a limit value, the connection between cooling circuit H3 and the suction port MP_in of the pressure supply unit MP is opened again, and the connection between cooling circuit H3 and the cooling oil line C-V_Kout to the couplings K1, K2, K0 is closed.

[0043] By controlling the pressure control valve EDS4, which serves as a pilot control for the cooling oil valve CV, the supply of cooling oil to clutches K1, K2, and K0 can be controlled as needed. Clutches K1 and K2, at least, serve as the starting element of the vehicle's drivetrain, so cooling is essential, for example, when the vehicle starts moving on an incline. However, supplying cooling oil to clutches K0, K1, and K2 increases their drag losses, making cooling oil supply undesirable when clutches K0, K1, and K2 are under little or no thermal load. Especially with cold hydraulic fluid, supplying cooling oil to clutches K1 and K2 can increase the drag torque of the input shafts of sub-transmissions TG1 and TG2 to such an extent that reliable gear engagement via the shift actuators SK1 and SK2 can no longer be guaranteed.Since the supply port of the pressure control valve EDS4 is connected to the pressure circuit H1, and since the cooling oil line C-V_Kout to the clutches K0, K1, K2 can be supplied from the volume flow regulated by the pressure control valves SysD-V1, SysD-V2, reliable demand-based control of the cooling oil supply to the clutches K1, K2 is ensured in all operating points of the dual clutch transmission G.

[0044] The EDS4 pressure control valve also serves for the hydraulic pilot control of the pK-V changeover valve. For this purpose, an output of the EDS4 pressure control valve is connected to a control surface of the pK-V changeover valve.

[0045] The flow rate at the pressure control valve SysD-V1 depends on the switching state of the switching valve PV. If the switching valve PV connects the second output line MP2 to the suction port MP_in of the pressure supply unit MP, the second output line MP2 feeds directly into the suction charging system of the pressure supply unit MP. This allows the drive power required to operate the pressure supply unit MP to be kept low. If the switching valve PV blocks the connection between the second output line MP2 and the suction port of the pressure supply unit MP, the flow rate from both output lines MP1 and MP2 of the pressure supply unit MP reaches the pressure control valve SysD-V1. The switching state of the switching valve PV depends on the pressure in pressure circuit H2, since the control surface of the switching valve PV is connected to the control surface of the pressure control valve SysD-V1.By controlling the pressure in pressure circuit H2, the volume flow available to supply cooling circuit H3 can be controlled.

[0046] If one or more of the actuators AK1, AK2, or AK0 have a high flow rate requirement, the pressure in pressure circuit H2 can be increased by appropriately controlling the pressure control valve EDS3. If the pressure in pressure circuit H2 exceeds the pressure in pressure circuit H1 by a defined limit, a differential pressure valve FV opens a direct connection between the two pressure circuits H1 and H2, so that pressure circuit H1 is supplied from pressure circuit H2 via the pressure supply unit MP. The differential pressure valve FV is designed as a spring-loaded check valve. The pressure differential threshold for opening the differential pressure valve FV therefore depends on the spring preload FV of the differential pressure valve.

[0047] Fig. Figure 3 shows a section of the circuit diagram according to Fig. 2 with an alternative configuration of the sensor arrangement SA. Depending on the switching position of the changeover valve pK-V, the pressure sensor pK is now connected to a pressure measuring point pK11 or to a pressure measuring point pK21. The pressure measuring point pK11 is located upstream of the orifice plate KV-1B, so that the pressure measuring point pK11 is arranged between the coupling valve KV-1 and the orifice plate KV-1B. In the same way, the pressure measuring point pK21 is arranged between the coupling valve KV-2 and the orifice plate KV-2B.

[0048] Fig. Figure 4 shows a distribution characteristic of the cooling oil valve CV, where the volume flow rate C-V_Kout_Q supplied to the cooling oil line C-V_Kout is specified as a function of an outlet pressure pEDS4 of the pressure control valve EDS4. At low or no outlet pressure pEDS4, no volume flow rate C-V_Kout_Q is supplied to the cooling oil line C-V_Kout. When the outlet pressure pEDS4 reaches a first limit, the cooling oil valve CV opens the connection between the cooling circuit H3 and the cooling oil line C-V_Kout, causing the volume flow rate C-V_Kout_Q to increase. When the outlet pressure pEDS4 reaches a further limit, the cooling oil valve CV closes the connection between the cooling circuit H3 and the cooling oil line C-V_Kout again, causing the volume flow rate C-V_Kout_Q to drop back to zero.

[0049] Fig. Figure 5 shows another section of the circuit diagram according to Fig. 2, which clarifies the functionality of the cooling oil valve CV and the changeover valve pK-V. In Fig.Figure 5 shows both the cooling oil valve CV and the changeover valve pK-V symbolically. It is clearly evident that the cooling oil valve CV has a first, a second, and a third switching position. The cooling oil valve CV connects the cooling circuit H3 to the cooling oil line C-V_Kout only in the second switching position. In the first and third switching positions, the cooling oil valve CV connects the cooling circuit H3 to the suction port MP_in of the pressure supply unit MP. With a suitable selection of the control surfaces on the cooling oil valve CV and the changeover valve pK-V, this design allows the changeover valve pK-V to be controlled to the desired position independently of a cooling oil supply to the couplings K1, K2, K0. Reference sign G dual-clutch transmission ON input wave VM internal combustion engine GW1 drive shaft K0 disconnect coupling AK0 actuator EM2 Electric Machine K1 First clutch K2 Second Clutch AK1 actuator AK1_p pressure connection AK2 actuator AK2_p pressure connection TG1 First sub-transmission TG2 Second sub-transmission i1, i2, i3, i4 translation stages SK1 switching actuator SK2 switching actuator GW2 output shaft AG Differential Gearbox DW drive wheel ZSY Central Synchronization iZ1, iZ2 Synchronization Translation Z1, Z2 clutch AZ1, AZ2 actuator PS Parking lock PSR parking lock wheel PSA actuator HCU Hydraulic Control Unit ECU Electronic Control Unit HY hydraulic system SA Sensor arrangement H1 pressure circuit H2 pressure circuit H3 cooling circuit EP pump EM1 electric motor MP pressure supply unit MP1 First output line MP2 Second Output Line MP_in suction port T Tank TS temperature sensor pK pressure sensor pK1, pK11 pressure measuring point pK2, pK21 pressure measuring point pK-V changeover valve F11-F14 Filter SysD-V1 pressure control valve SysD-V1_ab control line SysD-V2 pressure control valve EDS1 pressure control valve EDS2 pressure control valve EDS3 pressure control valve EDS4 pressure control valve pEDS4 output pressure EDS5 pressure control valve EDS6 pressure control valve EDS7 pressure control valve EDS8 pressure control valve SR-V1 check valve SR-V2 check valve KV-1 coupling valve KV-1B aperture KV-2 coupling valve KV-2B aperture KV-0 coupling valve PS-Z actuating cylinder PS-V parking lock valve PV switching valve FV Differential pressure valve Sp-V shut-off valve KU heat exchanger BP-V radiator protection valve C-EM cooling oil path CV cooling oil valve C-V_Kout cooling oil line CV-Kout_Q Volume flow

Claims

[1] Sensor arrangement (SA) for a hydraulic system (HY) of a transmission (G), comprising a sensor (pK) for determining a pressure in the hydraulic system (HY), wherein a changeover valve (pK-V) with at least a first position and a second position is provided, wherein the sensor (pK) is connected to a first pressure measuring point (pK1, pK11) in the first position of the changeover valve (pK-V) and to a second pressure measuring point (pK2, pK21) in the second position of the changeover valve (pK-V), characterized by , that the first pressure measuring point (pK1, pK11) detects an actuation pressure of a first clutch (K1) of the gearbox (G), and the second pressure measuring point (pK2, pK21) detects an actuation pressure of a second clutch (K2) of the gearbox (G). [2] Sensor arrangement (SA) according to claim 1, characterized by, that the changeover valve (pK-V) is designed as a spool valve, which is constructed in such a way that the sensor (pK) is hydraulically separated from the second pressure measuring point (pK2, pK21) in the first position of the changeover valve (pK-V) and is hydraulically separated from the first pressure measuring point (pK1, pK11) in the second position of the changeover valve (pK-V). [3] Sensor arrangement (SA) according to claim 1 or claim 2, characterized by , that the changeover valve (pK-V) is pre-tensioned in the first position by means of a spring (pK-VF), wherein the changeover valve (pK-V) can be actuated electromagnetically directly or hydraulically pilot-operated. [4] Sensor arrangement (SA) according to claim 3, characterized by , that the changeover valve (pK-V) is hydraulically pilot-operated, wherein a pressure control valve (EDS4) is provided, the output of which is connected to a control surface of the changeover valve (pK-V). [5] Sensor arrangement (SA) according to claim 1, characterized by , that - the first clutch (K1) can be actuated by a first hydraulic actuator (AK1) with a first pressure port (AK1_p), and the second clutch (K2) can be actuated by a second hydraulic actuator (AK2) with a second pressure port (AK2_p), - wherein a pressure at the first pressure port (AK1_p) can be controlled by a first coupling valve (KV-1), and a pressure at the second pressure port (AK2_p) can be controlled by a second coupling valve (KV-2), - wherein a first orifice (KV-1B) is arranged between the first coupling valve (KV-1) and the first pressure port (AK1_p), and a second orifice (KV-2B) is arranged between the second coupling valve (KV-2) and the second pressure port (AK2_p). [6] Sensor arrangement (SA) according to claim 5, characterized by, that the first pressure measuring point (pK1) is located between the first orifice (KV-1B) and the first pressure port (AK1_p), and the second pressure measuring point (pK2) is located between the second orifice (KV-2B) and the second pressure port (AK2_p). [7] Sensor arrangement (SA) according to claim 5, characterized by , that the first pressure measuring point (pK11) is located between the first coupling valve (KV-1) and the first orifice (KV-1B), and the second pressure measuring point (pK21) is located between the second coupling valve (KV-2) and the second orifice (KV-2B). [8] Hydraulic system (HY) for a gearbox (G) of a motor vehicle powertrain, characterized by a sensor arrangement (SA) according to any one of claims 1 to 7. [9] Hydraulic system (HY) according to claim 8 with reference to any one of claims 3 to 8, characterized by, that the changeover valve (pK-V) is hydraulically pilot-operated, wherein a pilot pressure (pEDS4) of the changeover valve (pK-V) depends on a pressure signal which serves to pilot at least one further valve (CV, Sp-V) of the hydraulic system (HY). [10] Hydraulic system (HY) according to claim 9, characterized by , that the supply of cooling oil to the first and second clutches (K1, K2) can be influenced by means of the additional valve (CV). [11] Hydraulic system (HY) according to claim 9 or claim 10, characterized by , that the further valve is a cooling oil valve (CV), wherein a pilot port of the changeover valve (pK-V) is connected to a pilot port of the cooling oil valve (CV). [12] Hydraulic system (HY) according to claim 11, characterized by, that the cooling oil valve (CV) has at least a first, a second and a third switching position, wherein in the first and third switching positions a cooling oil supply to the first and second clutch (K1, K2) is hydraulically blocked by means of the cooling oil valve (CV), and in the second switching position a cooling oil supply to the first and second clutch (K1, K2) is hydraulically released by means of the cooling oil valve (CV). [13] Hydraulic control unit (HCU) for a gearbox (G) of a motor vehicle powertrain, characterized by that the hydraulic control unit (HCU) comprises a hydraulic system (HY) according to any one of claims 8 to 12. [14] Transmission (G) for a motor vehicle, in particular a dual-clutch transmission, an automatic transmission or an automated transmission, characterized by a hydraulic system (HY) according to any one of claims 8 to 12 or by a hydraulic control unit (HCU) according to claim 13.

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