Method for operating a hydraulic system of a transmission for a motor vehicle

Abstract

The invention relates to a method for operating a hydraulic system (10) for a motor vehicle transmission, wherein the hydraulic system (10) comprises a hydraulic pump (12), a first hydraulic valve (26), a second hydraulic valve (28) and a sump (32).In a first process step, a diagnosis of the first hydraulic valve (26) is carried out, wherein if a defect of the first hydraulic valve (26) is detected in the first process step, a second process step is carried out for the purpose of pressure reduction in a working pressure line (36), wherein in the second process step the second hydraulic valve (28) is briefly brought into a second actuating position, in which a connection is made between a second working pressure port (44) of the second hydraulic valve (28) and a second actuating port (46) of the second hydraulic valve by means of the second hydraulic valve (28), wherein subsequently in a third process step the second hydraulic valve (28) is brought into a second rest position in which there is a connection between the second actuating port (46) and the sump (32).

Description

[0001] The invention relates to a method for operating a hydraulic system of a transmission for a motor vehicle.

[0002] From DE 10 2018 214 427 A1, a hydraulic system for a dual-clutch transmission of a motor vehicle is known. This hydraulic system comprises a hydraulic pump and piston-cylinder units, each for actuating two friction clutches of a dual clutch and a disconnect clutch upstream of the dual clutch. Each piston-cylinder unit is assigned a hydraulic valve, which allows each actuation chamber of the respective piston-cylinder unit to be supplied with actuation fluid from the hydraulic system as needed. The actuation fluid is supplied via a working pressure line connected to the hydraulic valves and the hydraulic pump.

[0003] The object of the present invention is to provide a method for operating such a hydraulic system known from the prior art, whereby a particularly safe operation of the hydraulic system is to be made possible.

[0004] The problem is solved by a method according to claim 1. Advantageous further developments of the method are described by claims dependent on claim 1.

[0005] This paper is based on known methods for operating a hydraulic system for a motor vehicle transmission, wherein the hydraulic system comprises a hydraulic pump, a first piston-cylinder unit, a second piston-cylinder unit, a first hydraulic valve, a second hydraulic valve, and a sump. In a known manner, an outlet of the hydraulic pump is connected to a working pressure line, with a first working pressure port of the first hydraulic valve and a second working pressure port of the second hydraulic valve each connected to the working pressure line. Furthermore, a first actuation port of the first hydraulic valve is connected to a first actuation chamber of the first piston-cylinder unit via a first supply line. Additionally, a second actuation port of the second hydraulic valve is connected to a second actuation chamber of the second piston-cylinder unit via a second supply line.A first sump port of the first hydraulic valve and a second sump port of the second hydraulic valve are each connected to the sump.

[0006] The first supply line is advantageously connected at one end directly to the first actuation port and at the other end directly to the first actuation chamber. The second supply line is advantageously connected at one end directly to the second actuation port and at the other end to the second actuation chamber.

[0007] The term "direct connection of two hydraulic elements" means that no further valve is arranged between the hydraulic elements mentioned, although it is not excluded that throttling elements could be arranged between the hydraulic elements mentioned.

[0008] The hydraulic pump is advantageously designed as an electrically driven hydraulic pump. The hydraulic pump transfers hydraulic fluid from the sump, which serves as a kind of reservoir, into the working pressure line.

[0009] The piston-cylinder units are designed to actuate clutches of the motor vehicle transmission. They are particularly advantageous for actuating friction clutches of the motor vehicle transmission. For this purpose, the actuating pistons of the piston-cylinder units are advantageously arranged such that each actuating piston of a respective piston-cylinder unit can, for example, act on a multi-plate clutch. The respective actuating pistons are arranged partially within a cylinder of the piston-cylinder units in a known manner. The actuating pistons divide the respective internal volume of the respective piston-cylinder units into an actuating chamber and a centrifugal oil chamber in a known manner.

[0010] The hydraulic valves are designed as described above to connect the respective piston-cylinder units to the working pressure line on one side and to the sump on the other. The hydraulic valves are advantageously designed as electromagnetically actuated proportional valves.

[0011] The first hydraulic valve is advantageously designed in a known manner such that, in a first actuated position of the first hydraulic valve, a connection is established between the first working pressure port of the first hydraulic valve and the first actuating port of the first hydraulic valve. The first hydraulic valve is further advantageously designed such that, in a first rest position of the first hydraulic valve, a connection is established between the first actuating port and the first sump port.

[0012] The second hydraulic valve is designed such that in a second actuating position of the second hydraulic valve a connection is established between the second working pressure port and the second actuating port, and that in a second rest position of the second hydraulic valve a connection is established between the second actuating port and the second sump port.

[0013] The respective actuation positions are advantageously those valve positions which, by appropriately supplying the respective piston cylinder units with hydraulic fluid, cause the respective friction clutches to close.

[0014] In the method according to the invention, it is provided that in a first process step a diagnosis of the first hydraulic valve is carried out, wherein if a defect of the first hydraulic valve is detected in the first process step, a second process step is carried out for the purpose of pressure reduction in the working pressure line, wherein in the second process step the second hydraulic valve is briefly brought into the second actuating position, wherein subsequently in a third process step the second hydraulic valve is brought into the second rest position.

[0015] The diagnostic procedure is a well-known method used to verify the proper functioning of a hydraulic valve. This diagnostic process is advantageously performed or controlled by an electronic control unit of the hydraulic system. For example, the diagnostic procedure can be a plausibility check, verifying whether actuation of the first hydraulic valve in its initial position elicits a system response that would indicate, for instance, a closed friction clutch coupled to the first hydraulic valve. If the expected system response does not occur, a defect can be inferred. In other words, a defect can be detected in this way.Upon detection of such a defect, an error message is advantageously stored in an error memory of the electronic control unit of the hydraulic system.

[0016] Secondly, a protective reaction is advantageously triggered upon detection of the defect. This advantageous protective reaction, as described above, ensures that hydraulic fluid is drained from the working pressure line to the sump as quickly as possible, at least to the extent that there is no longer any overpressure in the working pressure line.

[0017] The second step of the process, in which the second hydraulic valve is briefly moved into its second actuated position, means that the duration for which the second hydraulic valve is in this position is so short that no perceptible movement of the second actuating piston of the second piston-cylinder unit occurs. During this brief period in the second actuated position, a small amount of hydraulic fluid is transferred from the working pressure line into the second supply line, causing a slight drop in hydraulic pressure in the working pressure line and a slight increase in hydraulic pressure in the second supply line. Then, in the third step, when a connection is established between the second supply line and the sump, a small amount of hydraulic fluid is transferred from the second supply line into the sump.The second and third process steps thus enable the drainage of hydraulic fluid from the working pressure line into the sump.

[0018] Particularly advantageous is a fourth process step following the third, in which the second hydraulic valve is briefly returned to its second actuation position. In the fourth process step, the second hydraulic valve is treated exactly as in the second process step. Then, a fifth process step is advantageously performed, in which the second hydraulic valve is treated exactly as in the third process step. This procedure is particularly advantageously repeated at least until any overpressure in the working pressure line is completely relieved or until at least a certain pressure threshold in the working pressure line is undercut.

[0019] An advantageous further development of the method is proposed below, which can then be applied when the hydraulic system has a third piston-cylinder unit and a third hydraulic valve, wherein a third working pressure port of the third hydraulic valve is connected to the working pressure line, wherein a third actuating port of the third hydraulic valve is connected to a third actuating chamber of the third piston-cylinder unit by means of a third supply line, and wherein a third sump port of the third hydraulic valve is connected to the sump, wherein the third hydraulic valve is configured such that in a third actuating position of the third hydraulic valve there is a connection between the third working pressure port and the third actuating port, and that in a third rest position of the third hydraulic valve there is a connection between the third actuating port and the third sump port.In the third process step, the third hydraulic valve is briefly moved into the third actuated position, and then, in the fourth process step, the third hydraulic valve is moved into the third rest position. Thus, in this further development, the third hydraulic valve is treated in the same sequence of process steps as the second hydraulic valve, but with a time offset.

[0020] A further development involves putting the hydraulic pump into a non-pumping state during the second process step. For example, the hydraulic pump, which is advantageously designed as an electric hydraulic pump, is de-energized for this purpose.

[0021] A further development of the method provides that the second and third hydraulic valves each have not only an actuating port but also a return port. In both cases, the respective return port is permanently connected to the respective actuating chamber by means of a return line. In other words, it is advantageous that in both cases the respective return port is permanently connected to the respective actuating port by means of the respective return line. In both cases, it is advantageous that the respective hydraulic valve is internally designed such that a connection between the respective return port and the respective sump port can be established internally within the hydraulic valve, i.e., without any additional external lines.

[0022] The invention will now be described in detail with reference to the figures mentioned below.

[0023] This shows: Fig. 1 a schematic representation of a hydraulic system as well as Fig. 2 a schematic flowchart of a procedure for operating the hydraulic system.

[0024] Fig. Figure 1 shows a schematic representation of a hydraulic system 10 for a motor vehicle transmission, in particular for a hybrid dual-clutch transmission. The hydraulic system 10 is a part of a complete hydraulic system for the motor vehicle transmission, which is not shown in its entirety. The part relevant to the method according to the invention is shown here.

[0025] The hydraulic system 10 includes an electrically operated hydraulic pump 12, by means of which a hydraulic fluid can be pumped from a sump 32 into a working pressure line 36. For this purpose, an outlet 34 of the hydraulic pump 12 is connected to the working pressure line 36.

[0026] The hydraulic system 10 further comprises a first piston-cylinder unit 14, a second piston-cylinder unit 16, and a third piston-cylinder unit 18. The first piston-cylinder unit 14 is configured to actuate a first multi-plate clutch (not shown) of a dual-clutch transmission of the hybrid dual-clutch transmission. The second piston-cylinder unit 16 is configured to actuate a second multi-plate clutch (not shown) of the dual-clutch transmission of the hybrid dual-clutch transmission. The third piston-cylinder unit 18 is configured to actuate a disconnect clutch (not shown) of the hybrid dual-clutch transmission, which is configured as a third multi-plate clutch. The disconnect clutch is arranged with respect to a power flow between an input shaft (not shown) of the hybrid dual-clutch transmission and the dual clutch.

[0027] To supply the piston cylinder units 14, 16, 18 with hydraulic fluid as required, the hydraulic system has a first hydraulic valve 26, a second hydraulic valve 28 and a third hydraulic valve 30.

[0028] The hydraulic valves 26, 28, 30 are advantageously designed as electromagnetically actuated proportional valves.

[0029] Advantageously, the hydraulic valves 26, 28, 30 have electromagnetic actuators 80, 82, 84, namely a first electromagnetic actuator 80 of the first hydraulic valve 26, a second electromagnetic actuator 82 of the second hydraulic valve 28 and a third electromagnetic actuator 84 of the third hydraulic valve 30.

[0030] Advantageously, the hydraulic valves 26, 28, 30, in particular their electromagnetic actuators 80, 82, 84, are connected to an electronic control and regulation unit not shown here.

[0031] The first hydraulic valve 26 has a first working pressure port 38, which is directly connected to the working pressure line 36. Direct connection means that no other hydraulic valve is arranged between the working pressure line 36 and the hydraulic valve 26, or between the two directly connected elements mentioned above. The second hydraulic valve 28 has a second working pressure port 44, which is directly connected to the working pressure line 36.

[0032] In an advantageous embodiment of the inventive method described below, the third hydraulic valve 30 has a third working pressure port 50, which is directly connected to the working pressure line 36.

[0033] A first actuation port 40 of the first hydraulic valve 26 is directly connected via a first supply line 74 to a first actuation chamber 20 of the first piston-cylinder unit 14. A second actuation port 46 of the second hydraulic valve 28 is directly connected via a second supply line 76 to a second actuation chamber 22 of the second piston-cylinder unit 16. A third actuation port 52 of the third hydraulic valve 30 is directly connected via a third supply line 78 to a third actuation chamber 24 of the third piston-cylinder unit 18.

[0034] The first actuation chamber 20 is a chamber enclosed by a cylinder of the first piston-cylinder unit 14 and by a first actuating piston 68 of the first piston-cylinder unit 14. If hydraulic fluid is supplied to the first actuation chamber 20 via the first supply line 74, the first actuating piston 68 is moved in such a way that the first multi-plate clutch is closed.

[0035] Similarly, a supply of hydraulic fluid to the second actuation chamber 22 via the second supply line 76 causes a second actuating piston 70 to move, thus closing the second multi-plate clutch. Similarly, a supply of hydraulic fluid to the third actuation chamber 24 via the third supply line 78 causes a third actuating piston 72 to move, thus closing the third multi-plate clutch.

[0036] The first hydraulic valve 26 has a first sump port 62. The first sump port 62 is preferably directly connected to the sump 32.

[0037] The first hydraulic valve 26 is designed such that at least two valve positions can be realized, namely a first actuated position and a first rest position. In the first actuated position of the first hydraulic valve 26, there is a connection, advantageously internal to the valve, between the first working pressure port 38 and the first actuating port 40. In the first rest position of the first hydraulic valve 26, there is a connection between the first actuating port 40 and the first sump port 62.

[0038] Advantageously, the first hydraulic valve 26 has a first return port 42. The first return port 42 is connected to the first actuating chamber 20 by means of a first return line 56. The first return port 42 is advantageously connected directly to the first supply line 74. The first hydraulic valve 26 is particularly advantageously designed such that, in the first rest position, there is an internal connection between the first return port 42 and the first sump port 62.

[0039] The second hydraulic valve 28 has a second sump port 64. The second sump port 64 is preferably directly connected to the sump 32.

[0040] The second hydraulic valve 28 is designed such that at least two valve positions can be realized, namely a second actuated position and a second rest position. In the second actuated position of the second hydraulic valve 28, there is a connection, advantageously internal to the valve, between the second working pressure port 44 and the second actuating port 46. In the second rest position of the second hydraulic valve 28, there is a connection between the second actuating port 46 and the second sump port 64.

[0041] Advantageously, the second hydraulic valve 28 has a second return port 48. The second return port 48 is connected to the second actuation chamber 22 by means of a second return line 58. The second return port 48 is advantageously connected directly to the second supply line 76. The second hydraulic valve 28 is particularly advantageously designed such that, in the second rest position, there is an internal connection between the second return port 48 and the second sump port 64.

[0042] The third hydraulic valve 30 has a third sump port 66. The third sump port 66 is preferably directly connected to the sump 32.

[0043] The third hydraulic valve 30 is designed such that at least two valve positions can be realized, namely a third actuating position and a third rest position. In the third actuating position of the third hydraulic valve 30, there is a connection, advantageously internal to the valve, between the third working pressure port 50 and the third actuating port 52. In the third rest position of the third hydraulic valve 30, there is a connection between the third actuating port 52 and the third sump port 66.

[0044] Advantageously, the third hydraulic valve 30 has a third return port 54. The third return port 54 is connected to the third actuation chamber 24 by means of a third return line 60. The third return port 54 is advantageously connected directly to the third supply line 78. The third hydraulic valve 30 is particularly advantageously designed such that, in the third rest position, there is an internal connection between the third return port 54 and the third sump port 66.

[0045] Fig. Figure 2 shows a schematic flowchart of a procedure for operating the hydraulic system 10.

[0046] For the execution or control of the process, the hydraulic system 10 has a Fig. 1 control and regulation unit not shown.

[0047] In a first process step S1 of the procedure for operating the hydraulic system 10, a diagnosis of the first hydraulic valve 26 is performed. The diagnostic procedure is not described in detail here. The diagnosis can be a known diagnostic method for hydraulic valves. For example, the diagnosis can include an electrical test of the first electromagnetic actuator 80. Alternatively, the diagnosis can include a plausibility check of the first hydraulic valve 26. The first process step includes a first test step P1, in which it is checked whether or not the first hydraulic valve 26 is defective. If the first hydraulic valve 26 is defective, a second process step S2 is performed. If the test in test step P1 shows that the first hydraulic valve 26 is not defective, the first process step S1 is performed again.

[0048] In the second process step S2, the second hydraulic valve 28 is briefly moved to its second actuated position to reduce pressure in the working pressure line 36. The term "briefly" means that the time for which the second hydraulic valve 28 is moved to its second actuated position during the second process step S2 is so short that no noticeable displacement of the second actuating piston 70 occurs. Thus, in the second process step S2, a small flow of hydraulic fluid from the working pressure line 36 into the second supply line 76 takes place.

[0049] Advantageously, during the second process step, the hydraulic pump 12 is brought into a non-pumping state, so that the pressure in the working pressure line 36 no longer increases.

[0050] Advantageously, a third process step S3 is carried out immediately after the second process step S2. During the third process step, the second hydraulic valve 28 is, advantageously briefly, moved into its second rest position. This results in a small flow of hydraulic fluid from the second supply line 76, advantageously via the second return line 58, into the sump 32 during the third process step S3.

[0051] Particularly advantageously, during the third process step S3, the third hydraulic valve 30 is briefly moved into the third actuating position, so that a small flow of hydraulic fluid from the working pressure line 36 into the third supply line 78 occurs. The third process step is advantageously carried out quickly, i.e., with a short overall duration, so that no noticeable movement of the third actuating piston 72 occurs during the third process step S3.

[0052] After the third process step S3, a fourth process step S4 is advantageously carried out. During the fourth process step S4, the third hydraulic valve 30 is moved to the third rest position, so that a small flow of hydraulic fluid from the third supply line 78, advantageously via the third return line 60, into the sump 32 occurs. Advantageously, during the fourth process step, the second hydraulic valve 28 is again briefly moved to the second actuated position, in the same way as the second hydraulic valve 28 is handled in the second process step S2.

[0053] After the fourth process step S4, a second test step P2 is advantageously carried out. During the second test step P2, it is checked whether the pressure in the working pressure line 36 has been sufficiently reduced. This check can be performed using a suitable and appropriately positioned pressure sensor and the electronic control unit. If, during the second test step P2, it is determined that the pressure in the working pressure line 36 is higher than a pressure threshold, the third process step S3 is carried out again. If, on the other hand, it is determined during the second test step P2 that the pressure in the working pressure line 36 is less than or equal to the pressure threshold, the process is terminated, or the first process step is carried out next. Reference symbol list 10 Hydraulic system 12 Hydraulic pump 14 First piston-cylinder unit 16 Second piston cylinder unit 18 Third piston cylinder unit 20 First activity area 22 Second activity room 24 Third activity area 26 First hydraulic valve 28 Second hydraulic valve 30 Third hydraulic valve 32 Swamp 34 Exit 36 Working pressure line 38 First working pressure connection 40 First actuation connection 42 First return port 44 Second working pressure connection 46 Second actuation port 48 Second return port 50 Third working pressure connection 52 Third actuation connection 54 Third return port 56 First return line 58 Second return line 60 Third return line 62 First sump connection 64 second sump connection 66 Third sump connection 68 First actuating piston 70 Second actuating piston 72 Third actuating piston 74 First supply line 76 Second supply line 78 Third feeder 80 First electromagnetic actuator 82 Second electromagnetic actuator 84 Third electromagnetic actuator P1 First test step P2 Second test step S1 First procedural step S2 Second procedure step S3 Third procedural step S4 Fourth process step QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 214 427 A1

[0002]

Claims

[1] Method for operating a hydraulic system (10) for a motor vehicle transmission, wherein the hydraulic system (10) comprises a hydraulic pump (12), a first piston-cylinder unit (14), a second piston-cylinder unit (16), a first hydraulic valve (26), a second hydraulic valve (28) and a sump (32), wherein an output (34) of the hydraulic pump (12) is connected to a working pressure line (36), wherein a first working pressure connection (38) of the first hydraulic valve (26) is connected to the working pressure line (36), wherein a second working pressure connection (44) of the second hydraulic valve (28) is connected to the working pressure line (36), wherein a first actuation connection (40) of the first hydraulic valve (26) is connected to a first actuation chamber (20) of the first piston-cylinder unit (14), wherein a second actuation connection (46) of the second hydraulic valve (28) is connected to a second actuation chamber (22) of the second piston-cylinder unit (16), wherein a first sump connection (62) of the first hydraulic valve (26) and a second sump connection (64) of the second hydraulic valve (28) are each connected to the sump (32), wherein the second hydraulic valve (28) is designed such that in a second actuating position of the second hydraulic valve (28) there is a connection between the second working pressure connection (44) and the second actuating connection (46), and that in a second rest position of the second hydraulic valve (28) there is a connection between the second actuating connection (46) and the second sump connection (64), characterized by , that in a first method step (S1) a diagnosis of the first hydraulic valve (26) is carried out, wherein if a defect in the first hydraulic valve (26) is detected in the first method step (S1) a second method step (S2) is carried out for the purpose of reducing the pressure in the working pressure line (36), wherein in the second method step (S2) the second hydraulic valve (28) is briefly brought into the second actuating position, wherein subsequently in the course of a third method step (S3) the second hydraulic valve (28) is brought into the second rest position. [2] Method according to claim 1, characterized by , that the hydraulic system (10) comprises a third piston-cylinder unit (18) and a third hydraulic valve (30), wherein a third working pressure connection (50) of the third hydraulic valve (30) is connected to the working pressure line (36), wherein a third actuating connection (52) of the third hydraulic valve (30) is connected to a third actuating chamber (24) of the third piston-cylinder unit (18), and wherein a third sump connection (66) of the third hydraulic valve (30) is connected to the sump (32), wherein the third hydraulic valve (30) is designed such that in a third actuating position of the third hydraulic valve (30) there is a connection between the third working pressure connection (50) and the third actuating connection (52) and that in a third rest position of the third hydraulic valve (30) there is a connection between the third actuating connection (52) and the third sump connection (66), wherein in the course of the third method step (S3) the third hydraulic valve (30) is briefly brought into the third actuating position, wherein subsequently in the course of a fourth method step (S4) the third hydraulic valve (30) is brought into the third rest position. [3] Method according to claim 2, characterized by that in the course of the fourth method step (S4) the second hydraulic valve (28) is briefly brought into the second actuating position. [4] Method according to one of the preceding claims, characterized by that in the course of the second method step (S2) the hydraulic pump (12) is brought into a non-delivery state. [5] Method according to one of the preceding claims, characterized byin that a first piston (68) of the first piston-cylinder unit (14) is designed as an actuating piston for a first friction clutch of a dual clutch of a dual clutch transmission, wherein a second actuating piston (70) of the second piston-cylinder unit (16) is designed as an actuating piston for a second friction clutch of the dual clutch of the dual clutch transmission. [6] Method according to claim 2 and claim 5, characterized by that a third actuating piston (72) of the third piston-cylinder unit (18) is designed as an actuating piston for a separating clutch of the dual-clutch transmission arranged upstream of the dual clutch. [7] Method according to one of the preceding claims, characterized byin that the second hydraulic valve (28) has a second return connection (48) connected to the second actuating chamber (22), wherein the second hydraulic valve is designed such that in the second rest position there is a connection between the second return connection (48) and the second sump connection (64).

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