Hydraulic system for a dual-clutch transmission

Abstract

Hydraulic system (1) for a dual clutch transmission with a first electric pump (4) which is connected via an output to an actuating fluid line (6) of a dual clutch, with a second pump (12) which is connected via an output to an actuating line (11) to gear actuators (GS-A, GS-B, GS-C) and a cooling and lubrication line (16), wherein the actuating line (11) is designed as a supply line for actuating the gear actuators (GS-A, GS-B, GS-C), wherein a pressure distribution (10) for the gear actuators (GS-A, GS-B, GS-C) with an intermediate pressure control (9) is connected to the second pump (12) via the control line (11), wherein the cooling and lubrication line (16) is connected to an inlet of at least one cooling and lubrication valve (20) for a component (17, 18, 19) or group of components to be cooled and / or lubricated, characterized by the fact that a control input of the cooling and lubrication valve (20) is directly connected to an output port of the pressure control (9) via a control line (23), wherein the actuating fluid line (6) of the double clutch is designed to be pressure-independent and fluidically separated from the areas pressurized by the second pump (12).

Description

[0001] The invention relates to a hydraulic system for a dual-clutch transmission of the type defined in more detail in the preamble of claim 1.

[0002] A hydraulic system for a dual-clutch transmission is described in DE 10 2018 214 427 A1. The hydraulic system described therein for a dual-clutch transmission is divided into two subsystems connected via a check valve, each with its own pump. The first subsystem, pressurized by an electric pump, actuates the dual clutch. The second subsystem comprises the cooling, lubrication, and gear actuators within the dual-clutch transmission. It is pressurized by its own pump, which can be mechanically and / or electrically driven.

[0003] Hydraulic systems for dual-clutch transmissions are also described in DE 103 16 215 A1, EP 1 602 849 A1 and the generic WO 2010 083 862 A1.

[0004] Despite this division into two separate areas or subsystems, it remains critical that the gear actuators, on the one hand, and the cooling and lubrication systems, on the other, have very different requirements for oil pressure and quantity. Gear actuators require medium pressures with a medium flow rate for adjustment and high pressures with a very low flow rate for synchronization. Cooling and lubrication typically operate at ideally low pressures and small to very high oil flow rates.

[0005] Especially when, as part of optimizing energy consumption, the size of the oil pump, which can be electrically driven, is continuously reduced, ensuring an adequate supply to the gear actuators while simultaneously meeting maximum oil demand for cooling and lubrication becomes nearly impossible, necessitating prioritization. A further disadvantage lies in the need to control cooling and lubrication valves, which direct the flow of cooling and lubricating oil to the individual components or component groups. The commonly used electromagnetic control is complex, expensive, and requires considerable installation space.

[0006] The object of the present invention is therefore to provide an improved hydraulic system which offers an optimized design, particularly with regard to effort and installation space.

[0007] According to the invention, this problem is solved by a hydraulic system with the features in claim 1, and in particular in the characterizing part of claim 1. An advantageous embodiment and further development of the hydraulic system according to the invention is described in the dependent claim.

[0008] The design of the hydraulic system according to the invention is essentially based on a design known in principle from the prior art, comprising a first pump for supplying the dual clutches and a second pump for supplying the gear actuators as well as for cooling and lubrication. The second pump is connected via an outlet to an actuating line to the gear actuators and to a cooling and lubrication line. The actuating line serves as a supply line for actuating at least one gear actuator, and a pressure distribution system for the gear actuators, with an intermediate pressure control unit, is connected to the second pump via the actuating line. As is known in the art, the cooling and lubrication line is connected to the inlet of at least one cooling and lubrication valve for one or more components or component groups to be cooled and / or lubricated.According to the invention, a control input of this at least one cooling and lubrication valve is directly connected via a control line to an output port of the pressure control system, wherein the actuating fluid line of the dual clutch is designed to be pressure-independent and fluidically separated from the areas pressurized by the second pump. This indirect connection of the control input of the cooling and lubrication valve to the actuator line enables pressure regulation via the pilot pressure from the actuator line, i.e., the supply line for actuating the gear actuators. This has the decisive advantage that a cooling and lubrication valve constructed and used in this way can be designed without external actuators and yet still enables reliable control and regulation in the desired manner.The complex, expensive, and space-consuming electromagnetically controlled valve, which is standard practice in this area, can therefore be dispensed with. This approach can be used for various components or component groups supplied via the cooling and lubrication line and a cooling and lubrication valve. Overall, this significantly reduces the complexity of the electromagnetic actuators for these valves.

[0009] Furthermore, according to the invention, the actuating fluid line of the dual clutch is designed to be independent and fluidically separated on the pressure side from the areas pressurized by the second pump. The first subsystem, i.e., the dual clutch, supplied with pressure by the first pump, and the second subsystem, i.e., the gear actuators and the cooling / lubrication system, supplied with pressure by the second pump, are thus hydraulically completely separated from each other on the pressure side. Unlike the prior art, where a connection is implemented via a check valve, the design in this embodiment of the invention is completely separate. The two systems are connected exclusively via the oil sump and thus via the oil, which is typically present there at ambient pressure, but are completely separated on the pressure side, which facilitates the controllability of the respective pressures and oil volumes.

[0010] Further advantageous embodiments of the hydraulic system according to the invention also result from the exemplary embodiment, which is described in more detail below with reference to the figure.

[0011] The only accompanying figure shows an exemplary embodiment of a hydraulic system according to the invention.

[0012] The illustration in the only accompanying figure shows a possible embodiment of a hydraulic system 1. This is the hydraulic system 1 for a dual-clutch transmission (not shown). It essentially consists of two subsystems: a first subsystem 2 and a second subsystem 3. The first subsystem 2, shown on the left in the figure, comprises a first pump 4, which draws oil from, for example, a common oil sump 5 and delivers it to an actuating fluid line 6 of a dual clutch. From this line, the clutches K1, K2, and a disconnect clutch K0 are actuated via corresponding valves 7.

[0013] In the embodiment shown here, the actuating fluid line 6 is also connected to the oil sump 5 via an optional valve 8. This valve can be omitted if the working pressure is controlled accordingly via the first pump 4, which is easily achievable, for example, with an electrically driven pump. However, the valve 8 can also be designed as an electrically controlled working pressure valve, which is electromagnetically actuated, as indicated in the figure. Another possibility would be to design the valve 8 as a fixed-setting pressure relief valve or as an externally pressure-controlled working pressure valve.

[0014] Otherwise, the first subsystem 2 of the hydraulic system 1 for the dual-clutch transmission largely corresponds to the design known from the prior art, so no further discussion is necessary. Completely separate from this first subsystem 2 on the pressure side, the second subsystem 3 is located on the right side of the figure and is designed, among other things, to supply gear actuators GS-A, GS-B, GS-C, ...

[0015] With an intermediate pressure control 9, a pressure distribution 10 for the gear actuators GS-A, GS-B, GS-C,... is connected via a control line 11 to a second pump 12. The pressure control 9 is directly connected to the pressure distribution 10, and the pressure distribution 10 is directly connected via the control line 11 to an output side of the second pump 12.

[0016] The second pump 12 is connected to the oil sump 5 on its inlet side and to the control line 11 on its outlet side. The outlet side of the second pump 12 is also directly connected, without any further intermediate components, to an inlet of a pressure relief valve 14, which is located upstream of a heat exchanger 15 that serves as a cooler.

[0017] A control input of the pressure relief valve 14 is directly connected to an inlet of the heat exchanger 15. An outlet of the heat exchanger 15 is connected to a cooling and lubrication line 16, through which corresponding components or component groups 17, 18, 19, for example, a wheelset, the dual clutch, and an electric drive motor, can be cooled or lubricated. Cooling and lubrication valves 20, 21, 22 are arranged between the respective components 17, 18, 19 and the cooling and lubrication line 16.

[0018] The cooling and lubrication valve 22 is shown as an example and optionally as a conventional electromagnetically controlled valve.

[0019] The cooling and lubrication valve 20 for supplying component 17, for example the wheelset, is designed as a particularly economical and compact externally pressure-controlled valve. A control input of the cooling and lubrication valve 20 is indirectly connected to the actuating line 11, specifically downstream of the pressure control unit 9, via a control line designated 23. The control input of the cooling and lubrication valve 20 is directly connected to an output port of the pressure control unit 9.

[0020] The cooling and lubrication of the wheelset, as component or component group 17, is controlled as a function of the pressure in the control line 11. It is particularly advantageous to control the cooling and lubrication of the wheelset, as component or component group 17, directly as a function of the pressure downstream of the pressure control 9. This eliminates the need for electromagnetic control, such as that shown for the prior art of the cooling and lubrication valve 22 for component 19, for example, an electric drive motor. This is advantageous in terms of the required installation space, the complexity of the control system, and the costs. The cooling and lubrication valve 22 could also be designed analogously to the cooling and lubrication valve 20.

[0021] The cooling and lubrication valve 21, which supplies component 18 (the dual clutch) with oil for cooling and lubrication, is designed as a pressure relief valve, its control input being connected to the cooling and lubrication line 16. If the pressure level in this cooling and lubrication line 16 exceeds a preset pressure of the pressure relief valve 21, oil is released towards component 18, i.e., for cooling and lubrication of the dual clutch.

[0022] In addition to the connection of the control input of the cooling and lubrication valve with overpressure function 21, a spring, as shown in the figure, acts in the same direction, i.e., in the direction of "opening the valve." In the opposite direction, i.e., in the direction of "closing the valve," an electromagnetic actuator acts. The cooling and lubrication valve with overpressure function 21 is open in the de-energized state. The higher the current in the electromagnetic actuator of the cooling and lubrication valve with overpressure function 21, the greater the closing force. This allows, on the one hand, the release of excess pressure into the area of ​​component 18, for example, the dual clutch, and on the other hand, the electromagnetic actuator of this cooling and lubrication valve with overpressure function 21 enables demand-based control, in which the pressure at the control input acts only as a kind of "offset."

[0023] In practical operation, the lubrication and cooling of component 17 (the wheelset) and component 19 (the electric drive motor) take priority over the cooling of the dual clutch. In the second subsystem 3, there are essentially two control variables for this: the speed of the second pump 12 and the pressure threshold, which is set by the cooling and lubrication valve with overpressure function 21. If there is a high oil demand in the area of ​​component 17 or 19, the speed of the second pump 12 can be increased accordingly, and the pressure in the cooling and lubrication line 16 can be increased by increasing the current to the actuator of the cooling and lubrication valve with overpressure function 21.Furthermore, cooling of the dual clutch is also possible when required because, due to pressure losses in components 17 and 19 or due to the active closing of their associated cooling and lubrication valves 20 and 22, the pressure upstream of the cooling and lubrication valve with overpressure function 21 increases in the cooling and lubrication line 16 due to the higher pump speed. This, in turn, cools component 18, i.e., the dual clutch. Its priority is intentionally subordinate to that of components 17 and 19. Overall, this leads to energy optimization, allowing for highly optimized operation of the second pump 12 to minimize excess oil and thus reduce line losses.

Claims

[1] Hydraulic system (1) for a dual clutch transmission comprising a first electric pump (4) connected via an output to an actuating fluid line (6) of a dual clutch, a second pump (12) connected via an output to an actuating line (11) to gear actuators (GS-A, GS-B, GS-C) and a cooling and lubrication line (16), wherein the actuating line (11) is designed as a supply line for actuating the gear actuators (GS-A, GS-B, GS-C), wherein a pressure distribution (10) for the gear actuators (GS-A, GS-B, GS-C) with an intermediate pressure control (9) is connected to the second pump (12) via the control line (11), wherein the cooling and lubrication line (16) is connected to an inlet of at least one cooling and lubrication valve (20) for a component (17, 18, 19) or group of components to be cooled and / or lubricated, characterized by , that a control input of the cooling and lubrication valve (20) is directly connected to an output port of the pressure control (9) via a control line (23), wherein the actuating fluid line (6) of the double clutch is designed to be pressure-independent and fluidically separated from the areas pressurized by the second pump (12). [2] Hydraulic system (1) according to claim 1, characterized by , that the output of the second pump (12) is directly connected to an input of a pressure relief valve (14) which is arranged upstream of a heat exchanger (15) which serves as a cooler, wherein a control input of the pressure relief valve (14) is directly connected to an input of the heat exchanger (15), wherein an output of the heat exchanger (15) is connected to the cooling and lubrication line (16).

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