DE102006003517A1 - Hydraulic control device for triggering a double clutch, especially in an automatic double-clutch gearbox or in a hybrid drive system has actuators, a proportional valve and distributing valves - Google Patents

Abstract

First (1) and second (3) hydraulically triggered actuators work for first and second clutches in a double clutch respectively. A proportional valve (PV) (5) has an inlet (E5) with a main hydraulic pressure (PHaupt) and an outlet (A51), on which a first hydraulic operating pressure (P1) adjusted by the PV can be removed. First (7) and second (9) distributing valves have inlets and outlets. An independent claim is also included for a method for hydraulic triggering of pressure- controlled actuators, especially coupling actuators.

Description

The The invention relates to a hydraulic control device and a method for the hydraulic control of a first pressure-controlled actuator and a second pressure-controlled actuator, in particular one first Kupplungsaktuators and a second clutch actuator.

The predominant Number of automatic transmissions of conventional design has as starting element a so-called hydrodynamic converter to a motor vehicle to be able to start from scratch. Since meanwhile the claims of driver increased significantly in terms of fuel economy and drivability are, it became necessary in every state of motion of the motor vehicle Permit control and / or regulatory interventions. For automatic transmissions of the type described above, this was only possible to a limited extent. Therefore were developed other control and / or regulating concepts for automatic transmissions.

today Have automatic transmission usually over a hydrodynamic torque converter as a starting element. Besides There are some applications where the torque converter goes through a clutch is replaced as a starting element. This coupling will Hydraulically controlled / regulated and at the same time hydraulically cooled. gear shift are in the stepped transmissions by several hydraulically switchable Couplings or brakes realized.

In a dual-clutch transmission of a newer design, the starting and shifting functions are covered by two clutches. By way of example, the disclosure in the publications DE 198 21 164 A1 or DE 198 58 543 A1 noted dual-clutch transmission described. The clutch actuators of these clutches are hydraulically controlled by solenoid valves. With these solenoid valves infinitely variable control pressures can be set for the clutch actuators.

such Solenoid valves are expensive.

at Another dual-clutch transmission of the prior art will instead of a solenoid valve, a cost-effective slide valve used. The disadvantage of this construction, however, is that the switching from one clutch to the other with a significant short-term Torque drop and thus a traction interruption connected is. Such a switch meets the requirements of modern Motor vehicles with regard to fuel consumption and shifting comfort no more.

Furthermore is a precise one Control of each of the two clutches, z. B. microslip, not sufficiently possible.

It is therefore the object of the present invention, a hydraulic Control device or a corresponding method for driving provide two pressure-controlled actuators, which which is easy and inexpensive produce is a precise one Control of both clutches allows and at the same time when switching the torque drop so low as possible holds.

These The object is achieved by the control device having the features of the patent claim 1 and by the method having the features of the claim 7 solved.

advantageous versions and further developments of the invention are specified in the respective subclaims.

Provided according to the invention is a hydraulic control device for controlling a double clutch, especially in an automatic dual-clutch transmission or a hybrid drive arrangement, with a first hydraulically controllable Actuator for the first clutch of the double clutch and a second hydraulic controllable actuator for the second clutch of the double clutch. Furthermore, a proportional valve is provided, which has an inlet to which a hydraulic main or system pressure is applied. It has an output on which a from the proportional valve set first hydraulic actuating pressure is removable. This output pressure is due to any number of intermediate positions steady and precise adjustable.

Farther is a first directional control valve, preferably an electromagnetically controlled 3/2-way valve with on / off functionality provided, which has an inlet at which the main hydraulic pressure is applied and which has an output to which a second hydraulic actuating pressure depending on the control is removable. Such 3/2-way valves are inexpensive.

The Connection to the two actuators is by means of a second way valve, Preferably implemented a 4/2-way valve, the first Input to which the first hydraulic actuation pressure is applied, as well a second input has, on which the second hydraulic actuating pressure is applied. The 4/2-way valve has a first and second output, which is connected to the first and second actuator.

It is particularly advantageous if the first and second output are each connected to a first or second control input of the directional control valve is, so that the respective larger of the hydraulic actuation pressures determines which pressure paths the directional control valve adjusts and thus which actuating pressure is applied in each case to the two actuators. The second directional control valve is thus without an electronic control, but is controlled hydraulically via the pressure difference at its two working ports.

A Another option for controlling the second directional valve, which is a 4/2-way valve is designed with shift shift function, is that the control surfaces be controlled by external pressurization. This is the switching time can be freely selected and thus the changeover better controllable.

In particularly advantageous embodiment of the invention is provided that the proportional valve as an electromagnetically operated solenoid valve With variable force (VFS) trained is. Such solenoid valves are characterized by a precise control of the output pressure.

Preferably is the second directional valve as a 4/2-way valve with shift shift function formed, wherein the Umschaltschiebefunktion by the at the control inputs adjacent pressures is controllable. This can also be the second directional control valve electromagnetic Control may be omitted, resulting in a significant cost advantage connected is.

alternative is the second directional control valve in an advantageous manner as electromagnetic operated 4/2-way valve educated. For a better control is possible because the switching time freely selectable is. The valve remains unaffected by the inlet pressure values in the chosen Position. It is therefore no surveillance the valve positions necessary because no automatic reset by control pressures he follows.

With Another advantage is both the first actuator and the second Actuator is open in the depressurized state.

Especially for controlling two clutch actuators of a dual clutch for a Automatic transmission (but not just for such) includes the present invention also a method.

At the inventive method for the hydraulic control of a first pressure-controlled actuator and a second pressure-controlled actuator, in particular one first clutch actuator and a second clutch actuator, Both the first actuator and the second actuator will either with one of a first proportional valve starting from a Main pressure set the first actuating pressure or with a provided by a first directional control valve second actuating pressure driven. In this case, a second directional valve with the first and the second operating pressure and it becomes dependent the difference between the first actuating pressure and the second actuating pressure determines which of the two actuating pressures respectively the first or second actuator is supplied.

At the inventive method It is particularly advantageous that when the first actuator in an actuating pressure controlled by the proportional valve acted upon, active state and the second actuator in a depressurized state, the first directional control valve to a placed in flow position at the first specified time, whereby the actuating pressure builds up in the second actuator. In order to the conditions are created that with the inventive method is switched from the first, active clutch to the second.

In order to with the method according to the invention also from the second actuator, which is assumed to be active on the first, in this case inactive actuator to be switched can, it is advantageous that the first directional control valve to a first determined Time is brought into flow position, resulting in the first Actuator of the actuating pressure builds.

With further advantage runs the inventive method such that the actuation pressure controlled by the proportional valve at a second specific time, the time after the first one certain time is reduced. This will be the pressure at the first outlet of the second directional valve degraded so that, compared to the pressure at the second output of the directional control valve, a Pressure difference, which results in switching the second directional control valve leads.

One Another advantage of the method according to the invention is that a switching time, which is determined by the time of the switch of the second directional valve is defined by appropriate choice and adjustment the components of the first and second specific times so It can be determined that the torque drop at the first or second actuator as low as possible fails.

The Invention will now be described with reference to the drawing. Show it:

1 a hydraulic circuit diagram of an embodiment of a hydraulic control device according to the invention for controlling a first Kupplungsaktuators and a second Kupp lungsaktuators a dual clutch of an automatic transmission,

2 a control diagram of the hydraulic control device according to the 1 , such as

3 a hydraulic circuit diagram of another embodiment of a hydraulic control device according to the invention for driving a first Kupplungsaktuators and a second clutch actuator of a dual clutch of an automatic transmission.

1 shows a first embodiment of a hydraulic control device according to the invention for controlling a first pressure-controlled clutch actuator 1 and a second pressure controlled clutch actuator 3 a double clutch of an automatic transmission.

The two clutch actuators 1 . 3 are symbolized by single-acting cylinders. Both the first clutch actuator 1 as well as the second clutch actuator 3 are open in the depressurised state, ie they are not engaged. A piston 11 respectively. 12 is therefore contrary to the force of a spring 13 respectively. 14 can be brought into a closed position by means of a clutch actuation pressure p _K1 or P _K2 . For completeness, pipe ends 15 . 16 shown which with an open hydraulic fluid reservoir 17 connected via the pressures on the hydraulic fluid reservoir 17 can be delivered.

The actual hydraulic control device comprises three valves, the proportional valve 5 , a 3/2-way valve 7 as well as a 4/2-way valve 9 ,

The proportional valve 5 represents the clutch valve, ie the valve with which the two clutch actuators 1 respectively. 3 precisely controlled by pressure. This proportional valve 5 is formed in this embodiment as an electromagnetically continuously controllable 3/2-way valve and the input side to an input E ₅ via the flow line 18 in which a throttle 19 is provided with a hydraulic pump 20 connected. On the output side (output A ₅₁ ) there is a flow line connection via the flow line 22 to the line connection point 30 that the control lines 24 and 25 , which in each case at the left or right end face of the proportional valve ( 5 ) abut, as well as the flow line 23 supplied with pressure. A second output A ₅₂ is via a pipe end 26 with the open hydraulic fluid reservoir 17 connected to discharge excess pressures. The hydraulic pump 20 is on the input side via a flow line 21 with the open hydraulic fluid reservoir 17 connected. The hydraulic pump 20 supplies the flow line 27 , the line connection point 28 and the flow lines 18 and 29 with the system pressure p _main .

This electromagnetically continuously adjustable 3/2-way valve 5 provides at its output A _51, the pressure p ₁ available, which via control lines 24 and 25 at control inputs S ₅₁ and S _{52 of} the proportional valve 5 is applied. The output pressure p _{1 of} the proportional valve is via the infinitely adjustable electromagnet 5 in the flow lines 22 . 23 . 24 and 25 adjustable and adjustable. Instead of this 3/2-way valve 5 It is also possible to use other proportional valves known to the person skilled in the art for stepless regulation of the pressure p ₁ .

Furthermore, the hydraulic control device has a 3/2-way valve 7 on, which is designed as an electromagnetically actuated on / off valve. Such valves are inexpensive and easy to control. An input E ₇ this electromagnetically against the force of a spring 31 operable 3/2-way valve 7 is about the throttle 32 with the main / system pressure line 18 . 27 . 28 . 29 connected.

A first output A _{71 of} this electromagnetically operated 3/2-way valve 7 is in a conventional manner via a corresponding flow line 34 with an input E _{92 of} the 4/2-way valve 9 connected. A second output A ₇₂ is via a pipe end 33 with the open hydraulic fluid reservoir 17 connected. At the first output A ₇₁ is the output pressure p ₂ , according to the on / off function of the 3/2-way valve 7 essentially to the values zero or p _{main is} adjustable. In the how in 1 illustrated embodiment assumes the output pressure p ₂ is zero, since the 3/2-way valve is not energized.

Connected to the output flow lines 23 and 34 of the proportional valve 5 or the on / off valve 7 is according to the present invention, a pressure-controlled 4/2-way valve 9 intended. At its inputs E ₉₁ and E ₉₂ are in the flow lines 23 respectively. 34 existing pressures p ₁ and p ₂ at. On the output side, the 4/2-way valve 9 the two outputs A ₉₁ and A ₉₂ , where the clutch operating _pressures p _K1 and p _K2 abut. The outputs A ₉₁ and A ₉₂ are above the line connection points 35 respectively. 36 and the flow lines 39 respectively. 40 with the inputs E ₁ and E _{2 of} the clutch actuators 1 respectively. 3 connected. In addition, the outputs A ₉₁ and A _{92 are} via the line connection points 35 respectively. 36 via control lines 37 respectively. 38 connected to control inputs S ₉₁ and S ₉₂ , via which on the basis of the pressure difference between p _K1 and p _K2, the flow position of the 4/2-way valve 9 is set. Thus, the 4/2-way valve is considered automatic by means of pressure formed differential shift switch and has exactly two switching positions, so that either p _K1 = p ₁ and p _K2 = p ₂ in the one position (as in 1 shown) or p _K1 = p ₂ and p _K2 = p ₁ in the other position.

The operation of the hydraulic control device according to the invention according to the 1 or the method according to the invention is hereinafter also by means of 2 described:

Phase I: t <t1 (initial position)

First, the initial position of the control device according to the in the 1 and 2 illustrated embodiment described. It is believed that the clutch actuator 1 is active, ie that it is acted upon by the pressure p _K1 , which is identical to the pressure p ₁ , by the proportional valve 5 is controlled. As in 1 shown is the 4/2-way valve 9 in the position that the input E _{91 is} connected to the output A ₉₁ and the input E ₉₂ to the output A ₉₂ (p _K1 = p ₁ ). The height of the pressure p ₁ is through the proportional valve 5 certainly. As in 2 shown, the pressure p _{1 is} slightly less than the main or system pressure p _main .

As a result, the clutch actuator 1 actuated, which is why a torque M _{K1 is} transmitted to the first clutch.

The 3/2-way valve (on / off valve) 7 is located in the 1 shown position, ie it is not energized and is closed, with no force against the spring force of the spring 31 suppressed. Thus, the on / off valve is in the off position, ie the pressure p ₂ at the output A ₇ , as in 2 recognizable, before the time t ₁ equal to zero. By the position of the 4/2-way valve as described above 9 the input E ₉₂ are connected to the output A _92, so _K2 = p p ₂ = 0. The second clutch actuator 3 is thus depressurized, the second clutch is inactive, ie the torque M _K2 is also equal to zero.

Phase II: t ₁ <t <t _U

At time t ₁ , the 3/2-way valve 7 energized, ie it switches to on position, the electromagnetic force being fully against the spring force of the spring 31 acts. Thus now there is a passage connection between its input E ₇ and its first output A ₇₁ , whereby now the pressure p ₂ in the flow line 34 on the pressure p _main increases, as in 2 represented by the dashed line. Through the passage connection in the 4/2-way valve 9 between the input E ₉₂ and the output A ₉₂ , the pressure p _{2 is} also at the output A ₉₂ , which is why p _K2 = p ₂ applies. The clutch actuator 3 is thereby prefilled via the input E ₂ , wherein the pressure p _K2 against the spring force of the spring 14 acts. As a result, the torque M _K2 transmitted by the second clutch also increases, as indicated by the dotted line in FIG 2 shown.

At a time t _A begins by appropriate control of the proportional valve 5 the pressure p ₁ and thus the clutch pressure p _K1 decrease. This time t _A is set according to the characteristics of the components used so that the entire switching process leads to the lowest possible torque drop or the lowest possible interruption of traction, as will be explained in detail below.

Phase III: t _U <t <t ₂

The switching time t _U is characterized in that at this time, the 4/2-way valve switches, ie that there is no passage connection more of E ₉₁ to A ₉₁ and E ₉₂ to A ₉₂ , but now E ₉₁ with A ₉₂ and E ₉₂ with A _{91 are} connected. Trigger of the switching is the difference of the pressures p ₂ and p ₁ , respectively via the control lines 37 respectively. 38 act on the end faces of the 4/2-way valve. As soon as the pressure p ₂ exceeds the pressure p ₁ by a certain amount owing to the inertia, the 4/2-way valve switches over as described above. It takes place in the now connected flow lines 23 and 39 (about E ₉₁ and A ₉₂ ) as well 34 and 40 a pressure equalization by half the pressure difference instead. Out 2 It can be seen that the pressure p ₁ rises by a compensation value and the pressure p ₂ drops by substantially the same compensation value.

It should be noted that the switching time t _U does not correspond to a time that can be determined directly from the outside, but is determined by the selection of the properties of the components of the control device according to the invention. The more sensitive, for example, the 4/2-way valve 9 , So the changeover spool, responds to the pressure difference and thus switches, the closer t _{U is} at the time t _A , at the directly controlled from outside the pressure p ₁ begins to decrease.

Due to the increase in pressure of p ₂ during the phase II described above is at the second clutch actuator 3 to the switching time t _U already transmit a torque M _K2 , which is the amount of something higher than the torque M _K1 . The second clutch is thus also active at the switchover time t _U. Due to the high pressure level, the torque drop during switching is very low. It is obvious to the person skilled in the art that by a suitable choice of the components there is a large number of setting possibilities in order to to control the torque dip and the periods of pressure drop from p ₁ to the switching time t _U and the like.

From the switching time t _U , the second clutch actuator 3 no longer from the outlet pressure p _{2 of} the 3/2-way valve (on / off valve) 7 but from the outlet pressure p1 of the proportional valve 5 controlled. In 2 is shown that from the switching time t _{U of} the second clutch actuator 3 is driven at a constant pressure p ₁ while the second clutch remains active.

The first clutch actuator 1 is from the switching time t _U no longer from the output pressure p _{1 of} the proportional valve 5 but from the outlet pressure p _{2 of} the 3/2-way valve (on / off valve) 7 controlled. Due to the small drop in pressure and thus the torque at the first clutch, the first clutch remains active.

Phase IV: t> t ₂

At time t ₂ , the energization of the 3/2-way valve (on / off valve) 7 stopped, ie it switches immediately in the off position, which is against the spring force of the spring 31 acting electromagnetic force is no longer present. Thus, there is no passage connection between its input E ₇₁ and its output A ₇ more, which now the pressure p ₂ in the flow line 34 gradually drops to zero, as in 2 represented by the dot-dash line to the right of the time axis value t ₂ . That of the first clutch actuator 1 transmitted torque M _K1 gradually drops in the same way as in 2 shown dashed line to the right of the time axis value t ₂ shows.

Once the pressure p ₂ has reached the value zero, the control means is again in the above-described initial position (Phase I), with the difference that by the other travel position of the 4/2-way valve 9 no longer the first, but the second clutch active, by means of the proportional valve 5 precisely controlled clutch is.

For the next changeover, then from the second to the first clutch, you start again as described in Phase II above with the energization of the 3/2-way valve (on / off valve) 7 etc.

3 shows a further embodiment of the hydraulic control device according to the invention for controlling a first pressure-controlled clutch actuator 1 and a second pressure controlled clutch actuator 3 a double clutch of an automatic transmission. It is different from the one in 1 illustrated embodiment by another Ausgestal direction of the directional control valve 9 , as described below. Otherwise, the same components are used, with the same reference numerals as in 1 are provided. For the sake of simplicity, the description thereof will not be repeated here.

About the above advantages of the first embodiment, the offers second embodiment the following advantages. By using the electromagnetically actuated 4/2-way valve can the switching from outside be controlled better, since the switching time is freely selectable. Independent of at his exits adjacent pressures the valve remains in the switched position, if not a switch from the outside initiated becomes. This is no monitoring of Valve positions more necessary because no automatic reset by control pressures he follows. Compared to the above first embodiment, that is in the second embodiment used for coming electromagnetically actuated 4/2-way valve though a bit more expensive, but opposite another proportional clutch valve of the prior art nevertheless cheaper.

The operation of the hydraulic control device of the second embodiment as in 3 is essentially identical to the above described for the first embodiment mode of operation. Differences arise in the determination of the switching time, which can now be determined by a control from the outside. The same results when the control of the second directional control valve 9 is not controlled by internal control pressures, but via an external pressurization of the control surfaces.

The The present invention is not limited to the illustrated embodiment limited. In particular, you can by suitable selection of components in the control device according to the invention and the control parameter in the method according to the invention modifications and changes made without departing from the scope of the invention claimed by the appended claims.

With The present invention was a hydraulic control device or a corresponding method for controlling two pressure-controlled Actuators provided, which or which simple and inexpensive to produce is, a precise Control of both clutches and comfortable load circuits without Pressure or torque drop allows.

1

first Clutch actuator (single-acting cylinder for clutch and gear regulator one first transmission input shaft)

3

second Clutch actuator (single-acting cylinder for clutch and gear regulator one second transmission input shaft)

5

proportional valve

7

first way valve

9

second way valve

11

easy piston rod

12

easy piston rod

13

feather

14

feather

15

pipe end

16

pipe end

17

open Hydraulic fluid reservoir

18

Flowline

19

viskosestabile throttling

20

hydraulic pump

21

pipe end below hydraulic fluid level

22

Flowline

23

Flowline

24

control line

25

control line

26

pipe end

27

Flowline

28

line connection

29

Flowline

30

line connection

31

feather

32

viskosestabile throttling

33

pipe end

34

Flowline

35

line connection

36

line connection

37

control line

38

control line

39

Flowline

40

Flowline

p _main

main pressure

p ₁

first hydraulic actuating pressure

p ₂

second hydraulic actuating pressure

p _K1

first actuating pressure

p _K2

second actuating pressure

p

print

M

torque

M _K1

torque at the first clutch

M _K2

torque on second clutch

t

Time

E ₅

Input of the proportional valve 5

A ₅₁

first output of the proportional valve 5

A ₅₂

second output of the proportional valve 5

S ₅₁

first control input of the proportional valve 5

S ₅₂

second control input of the proportional valve 5

E ₇

Entrance of the directional control valve 7

A ₇₁

first output of the directional control valve 7

A ₇₂

second output of the directional control valve 7

E ₉₁

first input of the directional control valve 9

E ₉₂

second input of the directional control valve 9

_A91

first output of the directional control valve 9

A ₉₂

second input of the directional control valve 9

Claims (12)

Hydraulic control device for controlling a double clutch, in particular in an automatic double-clutch transmission or a hybrid drive arrangement, a. with a first hydraulically controllable actuator ( 1 ) for the first clutch of the double clutch, b. with a second hydraulically controllable actuator ( 3 ) for the second clutch of the double clutch, c. with a proportional valve ( 5 ) having an input (E ₅ ) to which a main hydraulic pressure (P _main ) is applied and which has an output (A ₅₁ ) to which one of the proportional valves (A ₅ ) 5 ) set first hydraulic actuating pressure (p ₁ ) is removable, d. with a first directional control valve ( 7 ) having an inlet (E ₇ ) against which the main hydraulic pressure (p _main ) is applied and which has an outlet (A ₇₁ ) at which a second hydraulic actuating pressure (p ₂ ) is removable, e. with a second directional control valve ( 9 ) having a first input (E ₉₁ ) to which the first hydraulic actuating pressure (p ₁ ) is applied, a second input (E ₉₂ ) to which the second hydraulic actuating pressure (p ₂ ) is applied, a first output (A ₉₁ ) that with the first actuator ( 1 ) and a second output (A ₉₂ ) connected to the second actuator (A ₉₂ ). 3 ) connected is. Hydraulic control device according to claim 1, characterized in that the second output (A ₉₂ ) of the second directional control valve (A ₉₂ ) 9 ) with a first control input (S ₉₁ ) of the second directional control valve (S ₉₁ ) 9 ) and the first output (A ₉₁ ) of the second directional control valve (A ₉₁ ) 9 ) a second control input (S ₉₂ ) of the second directional control valve (S ₉₂ ) 9 ) connected is. Hydraulic control device according to claim 1 or 2, characterized in that the proportional valve ( 5 ) is designed as an electromagnetically operated solenoid valve with variable force (VFS). Hydraulic control device according to claim 1 or 2, characterized in that the first directional control valve ( 7 ) is designed as an electromagnetically actuated 3/2-way valve with on / off functionality. Hydraulic control device according to An Claim 1 or 2, characterized in that the second directional control valve ( 9 ) is designed as a 4/2-way valve with Umschaltschiebefunktion, wherein the Umschaltschiebefunktion by the at the control inputs (S ₉₁ , S ₉₂ ) applied pressure is controllable. Hydraulic control device according to claim 1 or 2, characterized in that the second directional control valve ( 9 ) is designed as an electromagnetically operated 4/2-way valve. Hydraulic control device according to one of the preceding claims, characterized in that both the first actuator ( 1 ) as well as the second actuator ( 3 ) is open in the depressurized state. Method for the hydraulic control of a first pressure-controlled actuator ( 1 ) and a second pressure-controlled actuator ( 3 ), in particular a first clutch actuator ( 1 ) and a second clutch actuator ( 3 ), in which both the first actuator ( 1 ) as well as the second actuator ( 3 ) a. either with one of a first proportional valve ( 5 ) based on a main pressure (p _main ) set first actuating pressure (p ₁ ) b. or with one of a first directional control valve ( 7 ) provided second actuating pressure (p ₂ ) is driven, c. wherein a second directional control valve ( 9 ) is acted upon by the first and the second actuating pressure (p ₁ , p ₂ ) and is determined as a function of the difference between the first actuating pressure (p ₁ ) and the second actuating pressure (p ₂ ), which of the two actuating pressures (p ₁ , p ₂ ) each of the first and second actuator ( 1 . 3 ) is supplied. Method according to claim 8, characterized in that when the first actuator ( 1 ) in one with the proportional valve ( 5 ) controlled actuation pressure (p ₁ ) applied state and the second actuator ( 3 ) is in a depressurized state, the first directional control valve ( 7 ) is brought into flow position at a first specific time (t ₁ ), whereby in the second actuator ( 3 ) the actuating pressure (p ₂ ) builds. A method according to claim 8, characterized in that when the second actuator ( 3 ) in one with the proportional valve ( 5 ) controlled actuation pressure (p ₁ ) applied state and the first actuator ( 1 ) is in a depressurized state, the first directional control valve ( 7 ) is brought into flow position at a first specific time, whereby in the first actuator ( 1 ) the actuating pressure (p ₂ ) builds. Method according to one of claims 8 to 10, characterized in that the from the proportional valve ( 5 ) controlled actuation pressure (p ₁ ) at a second specific time (t _A ), which is temporally after the first predetermined time (t ₁ ), is reduced. Method according to one of claims 8 to 11, characterized in that a switching time (t _U ), by the time of the switch of the second way valve ( 9 ) is defined by suitable choice and adjustment of the components ( 5 . 7 . 9 ) of the first and second specific times (t ₁ , t _A ) is determined so that the torque drop at the first and second actuator ( 1 . 3 ) is as low as possible.