Method for actuating a decoupling unit

Abstract

The invention relates to a method for actuating a decoupling unit (27) in a powertrain, which powertrain comprises at least one driven shaft. The object of the invention is to simplify the actuation of the decoupling unit (27). This is achieved in that the decoupling unit (27) is passively actuated in an actuating direction via a first hydraulic functional surface (31) with an actuating force provided in a hydraulic system (60) and in that the decoupling unit (27) is passively actuated in a return direction via a second hydraulic functional surface (32) with a return force.

Description

Technical Field

[0001] The present invention relates to a method for decoupling a unit in an actuating transmission system, the transmission system including at least one driven shaft. Background Technology

[0002] The drivetrain is preferably a motor vehicle drivetrain with an electronic shaft, particularly a 2-speed electronic shaft. A motor vehicle drivetrain with a 2-speed electronic shaft comprising only one planetary carrier is known from German patent application DE 10 2018 120 446 A1. A method for controlling a disengaged clutch in a hybrid powertrain is known from international patent application WO 2017 / 194047 A1. A hybrid module having a disengaged clutch and an actuation device is known from German patent application DE 10 2019 122 920 A1. Summary of the Invention

[0003] The purpose of this invention is to simplify the actuation of the decoupling unit in a transmission system that includes at least one driven shaft.

[0004] This objective is achieved by a method for actuating a decoupling unit in a transmission system comprising at least one driven shaft, wherein the decoupling unit is passively actuated in the actuation direction by an actuating force provided in a hydraulic system via a first hydraulic functional surface, and wherein the decoupling unit is passively actuated in the return direction by a restoring force via a second hydraulic functional surface. An inactive drive will generate drive losses or frictional losses when it is not decoupled from the transmission system. In the case of a transmission system comprising two driven shafts, unwanted losses can be advantageously avoided by decoupling the driven shaft that is not needed in normal drive operation. Conventional transmissions have clutches that can be used to decouple the driven wheel or driven shaft. Vehicles with electronic shafts typically do not have switchable transmissions or only have 2-speed transmissions, as known, for example, in German Patent Application Publication DE 10 2018 120 446 A1, which is admitted from the outset. Unwanted losses can be reduced by a suitable decoupling unit. To decouple the unwanted driven shaft, an actuator is typically required, which comprises an active element having an electric motor or at least an electrically or electromagnetically controlled valve. In the claimed method, existing active elements, such as those used for changing the gear ratio, are advantageously used for hydraulically passively actuating the decoupling unit. This provides the advantage of decoupling without the need for additional active elements. Here, for example, the fact that two existing transmission elements, such as a clutch or brake, do not transmit any torque when not actuated is utilized so that the decoupling unit can be actuated by the hydraulic supply and the existing active elements of the transmission elements. The decoupling unit is, for example, a normally disengaged disconnect clutch. To engage the normally disengaged disconnect clutch, a hydraulic signal present in the hydraulic system is advantageously used and logically connected. To engage the decoupling unit, particularly the disconnect clutch, a hydraulic signal is generated that can be used for this purpose and is logically connected in the hydraulic system. Among other things, this provides the advantage of eliminating the need for an actuator, which would otherwise be required to actuate or reset the decoupling unit. Thus, the manufacturing and / or operating costs of the decoupling unit in the actuated transmission system can be effectively reduced.

[0005] A preferred exemplary embodiment of the method is characterized in that the decoupling unit is passively actuated by an actuating force from one of the two transmission elements. The transmission elements are two transmission elements already present in the drivetrain, such as a clutch or brake. This takes advantage of the fact that an actuating force is not always required to actuate the transmission elements. This actuating force is then advantageously used to hydraulically and passively actuate the decoupling unit. In this way, energy can be effectively saved during the operation of the drivetrain. The decoupling unit can be passively controlled by the actuating force or via a valve.

[0006] Another preferred embodiment of the method is characterized in that the transmission element and the decoupling unit are designed such that the decoupling unit reaches the contact point when actuated before the contact point of the transmission element. Therefore, the ventilation path of one of the transmission elements can be advantageously used to hydraulically actuate the decoupling unit. This provides the advantage that the function of the existing transmission element is not impaired.

[0007] Another preferred exemplary embodiment of the method is characterized in that the decoupling unit is actuated via a valve hydraulically connected to the actuation branch of the transmission element. In this way, the hydraulic passive actuation of the decoupling unit can be achieved at a very low cost in terms of design and manufacturing technology.

[0008] Another preferred exemplary embodiment of the method is characterized in that the decoupling unit is actuated via a pressure-reducing valve, which is hydraulically connected to an actuation branch of the transmission element via an OR valve. In this way, functional hydraulic passive actuation of the decoupling unit can be ensured even when the pressure in the hydraulic system used to actuate the decoupling unit is quite low. The pressure-reducing valve can be hydraulically supplied via a hydraulic pressure source, by means of which the transmission element is also supplied. However, the pressure-reducing valve can also be hydraulically supplied via another hydraulic pressure source present in the hydraulic system.

[0009] Another preferred exemplary embodiment of the method is characterized in that the transmission element is a normally disengaged clutch or brake, which is hydraulically closed via its respective associated actuation branch after the decoupling unit, designed as a normally disengaged cut-off clutch, has been closed by means of the same actuation branch. In this way, the decoupling unit can be hydraulically passively actuated with minimal design and manufacturing costs without compromising the ease of actuation of the clutch or brake.

[0010] Another preferred exemplary embodiment of the method is characterized in that the decoupling unit is passively actuated by back pressure, which is prevalent in hydraulic systems, in the presence of hydraulic resistance. Here, for example, the fact that the transmission system does not require cooling and / or lubrication in its non-moving state can be utilized. The already present and unnecessary back pressure can then be used for passive hydraulic actuation of the decoupling unit.

[0011] Another preferred exemplary embodiment of the method is characterized in that, prior to the activation of the driven shaft's shaft drive, back pressure from the cooling and / or lubrication system is used to close the decoupling unit of the normally disconnectable clutch. This ensures, in a simple manner, that sufficient cooling and / or lubrication is provided when the driven shaft is activated.

[0012] Another preferred exemplary embodiment of the method is characterized in that, when a motor vehicle equipped with a drivetrain is coasting, at least one driven shaft is decoupled by means of a passively actuated decoupling unit. In this way, efficient coasting operation of the drivetrain can be achieved with minimal design and manufacturing costs.

[0013] Another preferred exemplary embodiment of the method is characterized in that one of the two driven shafts is decoupled by means of a passively actuated decoupling unit to reduce losses, while the other driven shaft drives the motor vehicle equipped with a transmission system. In this way, unwanted losses in transmission system operation can be effectively reduced in a simple manner.

[0014] Another preferred exemplary embodiment of the method is characterized in that the restoring force in the tank line is generated by two transmission elements. These transmission elements are preferably two transmission elements already present in the drivetrain, such as a clutch or brake. Upon actuation, the transmission elements discharge into the tank via the tank line. Advantageously, the pressure in the tank line is slightly increased to generate the restoring force. It is conceivable to connect a check valve and a barrier in the clutch pressure line to generate a pressure signal for restoring the decoupling unit according to the direction of flow. The decoupling unit is actuated, and particularly engaged, by means of a first hydraulic functional surface advantageously formed on the double-acting piston, as described below with reference to various exemplary embodiments. The first hydraulic functional surface is, for example, circular. The restoring or disengaging engagement of the decoupling unit is initiated by means of a second hydraulic functional surface, which is, for example, designed in an annular shape. The double-acting piston can move back and forth in a cylinder, also known as a double-acting cylinder.

[0015] Another preferred exemplary embodiment of the method is characterized in that, in each case, a hydraulic resistance is arranged in the tank line of the transmission element to generate a restoring force. The hydraulic resistance is, for example, a barrier. The desired restoring force can be set using the magnitude of the hydraulic resistance. An appropriate restoring force signal is advantageously branched between the hydraulic resistance and a pressure-reducing valve assigned to the corresponding transmission element, wherein, if the transmission element is a clutch, the pressure-reducing valve is also called a clutch valve.

[0016] Another preferred exemplary embodiment of the method is characterized in that the restoring force is tapped via an OR valve. The tank line is connected to the two connections of the OR valve, such that the OR valve is subjected to a correspondingly increased tank pressure, which represents the restoring force. The restoring force acts on the second hydraulic functional surface via a third connection of a check valve. In this way, the decoupling unit is advantageously passively restored.

[0017] Another preferred exemplary embodiment of the method is characterized in that the actuation of the decoupling unit is performed by an amplified signal. This provides the advantage that the decoupling unit can be reliably actuated and specifically engaged with a relatively small actuation force.

[0018] Another preferred exemplary embodiment of the method is characterized in that the decoupling unit is responded to by an amplified signal. This provides the advantage that the decoupling unit can safely disconnect or reconnect with relatively low restoring force. The low restoring force provides the advantage that the dynamic actuation or engagement of the decoupling unit is only slightly affected by the restoring force.

[0019] Another preferred exemplary embodiment of the method is characterized in that the hydraulic control surface for resetting the decoupling unit is larger than the control surface for actuating the decoupling unit. The pressure level used for switching or valves is typically lower than the contact pressure of the transmission element designed as a clutch. This is important when torque is transmitted from the first clutch to the second clutch, as the decoupling unit should remain safely closed in this case. With this design, decoupling can only occur when one of the two clutches has disengaged and the second clutch passes its contact point upon disengagement.

[0020] Another preferred exemplary embodiment of the method is characterized in that the decoupling unit includes a double-acting hydraulic cylinder that is actuated and reset via a decoupling valve. The decoupling valve is, for example, designed as a 4 / 2-way valve. Advantageously, the two hydraulic pressure chambers of the double-acting hydraulic cylinder are connected to one side of the decoupling valve. The actuation line and tank line are advantageously connected to the other side of the decoupling valve. The decoupling valve is advantageously controlled by two different pressures.

[0021] Another preferred exemplary embodiment of the method is characterized in that the decoupling valve is designed as a 4 / 2-way valve controlled by two OR valves. One of the OR valves is connected between the aforementioned tank lines of the drive element. The other OR valve is advantageously connected between the two actuation branches of the drive element. In this way, the decoupling unit can be passively controlled in an efficient manner both when it is actuated and when it is deactivated.

[0022] Another preferred exemplary embodiment of the method is characterized in that the decoupling valve is designed as a proportional valve. The reversal of the decoupling valve from the first end position to the second end position is proportional to the magnitude of the corresponding pressure signal. The corresponding load pressure is advantageously fed back to the decoupling valve. A transition position is preferably designed between the two end positions such that the two pressure chambers of the double-acting cylinder are located on the tank. This has the advantage that there will never be pressure on the two pressure chambers of the double-acting hydraulic cylinder simultaneously.

[0023] The present invention may also relate to a computer program product having program code for executing the above-described methods when the computer program product is arranged on a processing device or stored on a computer-readable data carrier. This computer program product is used, for example, in a control system of a hydraulic system or a transmission system having a hydraulic system.

[0024] The present invention may also relate to a hydraulic system for the aforementioned transmission system.

[0025] The invention may also relate to a decoupling unit, valve, and / or decoupling valve for such a hydraulic system. The aforementioned components may be sold separately. Attached Figure Description

[0026] Other advantages, features, and details of the invention will become apparent from the following description, in which various exemplary embodiments are described in detail with reference to the accompanying drawings. In the drawings:

[0027] Figure 1 A schematic diagram of a motor vehicle with two driven axles is shown;

[0028] Figure 2 Two exemplary implementations of the functional chain in the driver located at different positions in the decoupling unit are shown;

[0029] Figure 3 A hydraulic system for actuating and reversing a decoupling unit in the drivetrain of a motor vehicle according to a first exemplary embodiment is shown;

[0030] Figure 4 It shows the relationship with Figure 3 An exemplary embodiment similar to the one described above has an additional decoupling valve assigned to the decoupling unit; and

[0031] Figure 5 It shows the relationship with Figure 4 Similar to the exemplary implementation in the example implementation, the decoupling valve is designed as a proportional valve with a directional switching system. Detailed Implementation

[0032] exist Figure 1 The diagram schematically illustrates a motor vehicle 1 with a transmission system 2. The transmission system 2 includes two driven shafts 3 and 4. Each driven shaft 3 and 4 is equipped with two wheels 5 and 6 and 7 and 8.

[0033] Driven shaft 3 is assigned a shaft drive 9. Driven shaft 4 is assigned a shaft drive 10. When the vehicle 1 is in operation, the two shaft drives 9 and 10 do not always need to be activated simultaneously. To avoid wear and tear, one of the shaft drives 9 and 10 can be turned off during normal operation.

[0034] exist Figure 2 The diagram schematically illustrates two options for a functional chain having a driver 11, a gear ratio device 12, a decoupling unit 13, and a wheel 14. The gear ratio device 12 is, for example, a transmission. To avoid unwanted losses during operation of the driver 11, the driver 11 can be decoupled from the decoupling unit 13. Therefore, losses to the wheel 14 can be reduced.

[0035] Vehicles with typical drives have transmissions with clutches and gears. Here, wear on the wheels can usually be fully decoupled using the clutch and gear selection.

[0036] In vehicles with so-called electronic shafts, shiftable transmissions are typically not installed. Here, decoupling unit 13 can be advantageously used to reduce losses during operation when a corresponding drive 11 is not required.

[0037] Vehicles equipped with electronic shafts can also have multiple gears, particularly two gears. Here, decoupling unit 13 can also be advantageously used to minimize losses. Figure 2 In this configuration, the functional chain above is preferred because the decoupling unit 13 is arranged closer to the wheel 14.

[0038] The decoupling unit 13 can be actuated using a suitable actuator. Conventional actuators include at least one active element with an electric motor or at least an electric valve.

[0039] Figures 3 to 5 This demonstrates how the desired decoupling function can be achieved using a hydraulic system 60 without requiring additional active components in the decoupling unit. Figures 3 to 5 In an exemplary embodiment of the hydraulic system 60, the decoupling unit 27 is connected to an existing active component, allowing the decoupling unit 27 to be effectively actuated without additional active components. Figures 3 to 5 The same reference numerals are used to denote the same or similar parts. Common features are described only once. The hydraulic system 60 includes a hydraulic pressure source 15. The hydraulic pressure source 15 includes, for example, at least one hydraulic pump.

[0040] exist Figures 3 to 5 In the middle, the actuation line 16 is connected to the outlet of the hydraulic pressure source 15. A hydraulic consumable, such as a parking lock, can be connected to the upper end of the actuation line 16, which... Figures 3 to 5 The circuit was cut off. Two branch points, 17 and 18, were provided in the actuation line 16.

[0041] The first actuating branch 19 is connected to branch point 17. The second actuating branch 20 is connected to branch point 18. The first actuating branch 19 is provided with a first transmission element 21. The second actuating branch 20 is provided with a second transmission element 22. Pressure reducing valves 23 and 25 are arranged in each of the actuating branches 19 and 20.

[0042] Hydraulic branches 24 and 26 are provided between the pressure reducing valves 23 and 25 and the transmission elements 21 and 22. An OR valve 29 is connected between the branch points 24 and 26.

[0043] Figure 3 The simplest variation of the hydraulic system 60 is shown. The decoupling unit 27 is directly connected to valve 29, which in turn is connected between branch points 24 and 26. The decoupling unit 27 is, for example, a disengaged clutch. The transmission elements 21 and 22 are, for example, clutches or brakes.

[0044] Transmission elements 21 and 22 are actuated via pressure reducing valves 23 and 25. In the non-actuated state, transmission elements 21 and 22, and especially clutches 21 and 22, do not transmit any torque. This means that when clutches 21 and 22 are disengaged, decoupling unit 27 can also be disengaged.

[0045] During the operation of the hydraulic system 60, it must be ensured that the decoupling unit 27, designed as a cut-off clutch 28, is safely closed before one of the transmission elements, specifically one of the clutches 21 and 22, transmits torque.

[0046] Therefore, the disengagement clutch 28 is designed to safely engage at low pressure before one of the clutches 21 or 22 begins to transmit torque. To achieve this, a pressure range of what is called a ventilation path for one of the clutches 21 or 22 is used to engage the disengagement clutch 28. The actuation path reaching the point of contact is designated as the ventilation path. When the point of contact is exceeded, torque is transmitted in a targeted manner.

[0047] Figure 3 Reference numeral 30 in the accompanying drawings indicates that the decoupling unit 27, designed as a disengagement clutch 28, includes a double-acting cylinder 30. In the double-acting cylinder 30, Figure 3 The piston is guided to move back and forth to the left and right. The piston includes... Figure 3 The first hydraulic functional surface 31 on the left side and Figure 3 The second hydraulic functional surface 32 is located on the right side. The first hydraulic functional surface 31 is designed as a circular surface. The second hydraulic functional surface 32 is designed as an annular surface.

[0048] The first hydraulic functional surface 31 is actuated by a force from the first actuation branch 19 or the second actuation branch 20 via the OR valve 29. The second hydraulic functional surface 32 can be actuated by a restoring force from the tank line 34 or the tank line 35 via the OR valve 33.

[0049] Tank line 34 is connected to pressure reducing valve 23. Tank line 35 is connected to pressure reducing valve 25. A hydraulic resistance 41 is arranged in tank line 34. A hydraulic resistance 42 is arranged in tank line 35.

[0050] The decoupling unit 27 is engaged via a circular first hydraulic functional surface 31 and an OR connection of actuation branches 19 and 20. Disengagement is initiated via an annular second hydraulic functional surface 32. The operating pressure, known as the restoring force, is tapped via an OR connection of tank lines 34 and 35.

[0051] Conversely, the working pressure must first be generated during the disconnection process. For example... Figure 3 As shown, this can be accomplished via hydraulic resistances 41 and 42 in tank lines 34 and 35. Hydraulic resistances 41 and 42 are designed, for example, as barriers. Pressure signals for disconnecting the engagement process are branched between pressure reducing valves 23 and 25 and hydraulic resistances 41 and 42 and sent to valve 33.

[0052] The operating pressure, signal pressure, or restoring force used for disengagement should be relatively low so as to only slightly affect the dynamic disengagement of the transmission elements 21, 22, which are designed as clutches. Therefore, reliable disengagement of the decoupling unit 27 is only possible with a very large hydraulic functional surface 32.

[0053] Therefore, in Figure 4 The exemplary embodiment proposed in the text suggests that both engagement and disengagement occur with signal amplification. Ideally, this is achieved using a passive decoupling valve 45, which is arranged in an actuation branch 37. The actuation branch 37 is connected to a branch 38 of the actuation line 16. In this way, the decoupling valve 45 is supplied with the actuation force or system pressure provided at the outlet of the hydraulic pressure source 15 by the actuation line 16.

[0054] Figure 4 The dashed circle in the diagram indicates another hydraulic pressure source 50, which can be located in the hydraulic system 60 to supply actuation force or system pressure to the actuation branch 37. In this case, Figure 4 The hydraulic connection between branch points 18 and 38 has been omitted. Figure 4 Conversely, as shown, signal amplification engagement and disengagement can also be performed via a passive valve for engagement and disengagement, respectively.

[0055] Figure 4 The diagram illustrates the engaged operating state, in which system pressure is connected to the first hydraulic functional surface for engagement. The decoupling unit 27 engages by a pressure threshold that must be reached at once. This is accomplished by changing the system pressure before the transmission element 21 or 22 is activated or before torque is transmitted via the transmission elements 21, 22, which are designed as clutches.

[0056] The decoupling unit 27, designed as a disengagement clutch 28, disconnects in reverse order. If the drive element 21 or the drive element 22 designed as a clutch reaches its contact point upon disengagement, the force ratio at the decoupling valve 45 is adjusted to cause the decoupling valve 45 to switch and the hydraulic functional surface 32 to be actuated for disengagement and engagement.

[0057] As in Figure 4 As symbolically or schematically shown, this is accomplished by means of pressure control surfaces of different sizes on the decoupling valve 45. Here, the pressure control surface used to open the valve position is larger than the pressure control surface used to close the valve position. The pressure level used to switch the decoupling valve 45 is typically lower than the two contact pressures of the clutches 21 and 22.

[0058] This is also important when torque is transmitted from clutch 21 to clutch 22, as the decoupling unit must remain safely closed here. With this design, decoupling can only occur when one of the two clutches 21, 22 has disengaged and the second has passed the contact point upon disengagement.

[0059] An optional spring on the decoupling valve 45 is not shown, which reliably ensures the preferred position of the decoupling valve 45 under reduced pressure. Depending on boundary conditions, such as a suitable control strategy, either the first or second valve position of the decoupling valve 45 may be advantageous.

[0060] Figure 5 A detailed variation of the decoupling valve 45 is shown. Switching from one valve position to another is proportional to the magnitude of the corresponding pressure signal. The corresponding load pressure is fed back to the decoupling valve 45, which is designed as a proportional valve. The transition position between the two end positions is designed such that both pressure chambers of the double-acting cylinder 30 of the decoupling unit 27 are located on the tank. This has the advantage that there will never be pressure in the two pressure chambers of the double-acting cylinder 30 simultaneously.

[0061] A variation is not shown in which only one of the two pressure chambers of the double-acting cylinder 30 of the decoupling unit 27 is fed back to the decoupling valve 45. It may be advantageous to omit the feedback when the decoupling unit 27 is disconnected, so as to make the decoupling more robust or more dynamic.

[0062] List of reference numerals

[0063] 1. Motor vehicles

[0064] 2. Transmission system

[0065] 3 Driven Shaft

[0066] 4 driven shafts

[0067] 5 wheels

[0068] 6 wheels

[0069] 7 wheels

[0070] 8 wheels

[0071] 9-axis driver

[0072] 10-axis drive

[0073] 11 drives

[0074] 12. Transmission ratio device

[0075] 13 Decoupling Units

[0076] 14 rounds

[0077] 15. Hydraulic pressure source

[0078] 16 Actuation lines

[0079] 17 branch points

[0080] 18 branch points

[0081] 19 First moving branch

[0082] 20 Second Actuation Branch

[0083] 21 First transmission element

[0084] 22 Second transmission element

[0085] 23 Pressure reducing valve

[0086] 24 branch points

[0087] 25 Pressure reducing valve

[0088] 26 branch points

[0089] 27 Decoupling Unit

[0090] 28. Disengagement clutch

[0091] 29 or valve

[0092] 30 Double-acting cylinder

[0093] 31 First Hydraulic Functional Surface

[0094] 32 Second Hydraulic Functional Surface

[0095] 33 or valve

[0096] 34 Tank Pipelines

[0097] 35 tank pipeline

[0098] 37 Actuation Branch

[0099] 38 branch points

[0100] 41 Hydraulic resistance

[0101] 42 Hydraulic resistance

[0102] 45 Decoupling valve

[0103] 50 Another hydraulic pressure source

Claims

1. A method for decoupling units (13; 27) in an actuated transmission system (2), said transmission system comprising at least one driven shaft, characterized in that, The decoupling unit (13; 27) is passively actuated in the actuation direction via a first hydraulic functional surface (31) by an actuating force present in the hydraulic system (60), wherein the decoupling unit (13; 27) is passively actuated in the return direction via a second hydraulic functional surface (32) by a restoring force generated by a first transmission element (21) or a second transmission element (22), wherein hydraulic resistances (41, 42) are arranged in the tank lines (34, 35) of the transmission elements (21, 22) to generate the restoring force, wherein the first hydraulic functional surface (31) is acted upon by an actuating force from a first actuating branch (19) of the first transmission element (21) or a second actuating branch (20) of the second transmission element (22) via a first OR valve (29), and the second hydraulic functional surface (32) is acted upon by a restoring force from the tank lines (34, 35) of the transmission elements (21, 22) via a second OR valve (33).

2. The method according to claim 1, characterized in that, The first OR valve (29) is connected between the first actuation branch (19) and the second actuation branch (20), and the second OR valve (33) is connected between the tank line (34) of the first transmission element (21) and the tank line (35) of the second transmission element (22).

3. The method according to claim 2, characterized in that, The first actuation branch (19) is provided with a pressure reducing valve (23), and the first transmission element (21) is actuated via the pressure reducing valve (23). The second actuation branch (20) is provided with a pressure reducing valve (25), and the second transmission element (22) is actuated via the pressure reducing valve (25).

4. The method according to claim 1, characterized in that, The actuation of the decoupling unit (13; 27) is implemented through signal amplification.

5. The method according to claim 1, characterized in that, The decoupling units (13; 27) are recovered through signal amplification.

6. A method for decoupling units (13; 27) in an actuated transmission system (2), the transmission system comprising at least one driven shaft, characterized in that, The decoupling unit (13; 27) is passively actuated in the actuation direction by an actuating force present in the hydraulic system (60) via a first hydraulic functional surface (31), wherein the decoupling unit (13; 27) is passively actuated in the return direction by a restoring force via a second hydraulic functional surface (32), the decoupling unit (13; 27) is actuated in the actuation direction and passively actuated in the return direction by a decoupling valve (45), the decoupling valve (45) being designed to be controlled via a first OR valve (29) and a second OR valve (33), wherein hydraulic resistances (41, 42) are respectively arranged in the tank line (34) of the first transmission element (21) and the tank line (35) of the second transmission element (22) to generate a pressure signal for the decoupling unit to return and be sent to the second OR valve (33) to control the decoupling valve (45), the pressure signal for the decoupling unit to return being generated by the first transmission element (21) or the second transmission element (22).

7. The method according to claim 6, characterized in that, The first OR valve (29) is connected between the first actuation branch (19) of the first transmission element (21) and the second actuation branch (20) of the second transmission element (22), and the second OR valve (33) is connected between the tank line (34) of the first transmission element (21) and the tank line (35) of the second transmission element (22).

8. The method according to claim 7, characterized in that, The first actuation branch (19) is provided with a pressure reducing valve (23), and the first transmission element is actuated via the pressure reducing valve (23). The second actuation branch (20) is provided with a pressure reducing valve (25), and the second transmission element is actuated via the pressure reducing valve (25).

9. The method according to claim 7, characterized in that, The decoupling valve (45) is arranged in the actuation branch (37), and the actuation branch (19), the second actuation branch (20) and the actuation branch (37) are all actuated by the outlet of the hydraulic pressure source (15) of the hydraulic system (60).

10. The method according to claim 6, characterized in that, The decoupling valve (45) is designed as a two-position four-way valve controlled by a first OR valve (29) and a second OR valve (33).

11. The method according to claim 6, characterized in that, The decoupling valve (45) is designed as a proportional valve.

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